Materials

8 pages, 567 KiB

Open AccessArticle

Feasibility of Using Multilayer Platelets as Toughening Agents

by Yuan-Liang Chin and Wei-Hsing Tuan^*

Ceramic-Matrix Composite Lab., Dept. of Mater. Sci. & Eng., National Taiwan University, Taipei, 106 Taiwan

Materials 2010, 3(1), 1-8; https://doi.org/10.3390/ma3010001 - 24 Dec 2009

Cited by 13 | Viewed by 14035

It is known that the toughness of brittle ceramics can be improved significantly with the addition of hard platelets. In the present study, platelet-shape multilayer ceramic laminates are utilized as a toughening agent for alumina ceramics. They are prepared by laminating the BaTiO [...] Read more.

It is known that the toughness of brittle ceramics can be improved significantly with the addition of hard platelets. In the present study, platelet-shape multilayer ceramic laminates are utilized as a toughening agent for alumina ceramics. They are prepared by laminating the BaTiO₃-based ceramic tapes. Although the elastic modulus of the BaTiO₃-based platelets is lower than that of the alumina matrix, and the platelets are also reactive to alumina at elevated temperatures, the weak platelets are found to exhibit the ability to deflect major matrix cracks by forming a large number of microcrack branches within the platelets, thus achieving the desired toughening effect. Full article

(This article belongs to the Special Issue Composite Materials)

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17 pages, 631 KiB

Open AccessArticle

Nanoporous Carbide-Derived Carbon Material-Based Linear Actuators

by Janno Torop¹, Mati Arulepp², Jaan Leis^2,3, Andres Punning¹, Urmas Johanson¹, Viljar Palmre¹ and Alvo Aabloo^1,*

¹ IMS Lab, Institute of Technology, University of Tartu, Nooruse1, 50411 Tartu, Estonia

² Carbon Nanotech Ltd., Riia 185, 51014 Tartu, Estonia

³ Institute of Chemistry, University of Tartu, Ravila 14a, 50411, Tartu, Estonia

Materials 2010, 3(1), 9-25; https://doi.org/10.3390/ma3010009 - 24 Dec 2009

Cited by 40 | Viewed by 17067

Abstract

Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric effect [...] Read more.

Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric effect in nanocomposite material actuators containing carbide-derived carbon (CDC) and polytetrafluoroetylene polymer (PTFE). Transducers based on high surface area carbide-derived carbon electrode materials are suitable for short range displacement applications, because of the proportional actuation response to the charge inserted, and high Coulombic efficiency due to the EDL capacitance. The material is capable of developing stresses in the range of tens of N cm^-2. The area of an actuator can be dozens of cm², which means that forces above 100 N are achievable. The actuation mechanism is based on the interactions between the high-surface carbon and the ions of the electrolyte. Electrochemical evaluations of the four different actuators with linear (longitudinal) action response are described. The actuator electrodes were made from two types of nanoporous TiC-derived carbons with surface area (S_A) of 1150 m² g^-1 and 1470 m² g^-1, respectively. Two kinds of electrolytes were used in actuators: 1.0 M tetraethylammonium tetrafluoroborate (TEABF₄) solution in propylene carbonate and pure ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf). It was found that CDC based actuators exhibit a linear movement of about 1% in the voltage range of 0.8 V to 3.0 V at DC. The actuators with EMITf electrolyte had about 70% larger movement compared to the specimen with TEABF₄electrolyte. Full article

(This article belongs to the Special Issue Molecular Biomimetics and Materials Design)

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22 pages, 924 KiB

Open AccessReview

Graded/Gradient Porous Biomaterials

by Xigeng Miao^1,* and Dan Sun²

¹ Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, QLD 4059, Australia

² NIBEC, University of Ulster, Jordanstown Campus, Co. Antrim, NI, BT37 0QB, Northern Ireland, UK

Materials 2010, 3(1), 26-47; https://doi.org/10.3390/ma3010026 - 25 Dec 2009

Cited by 235 | Viewed by 26438

Abstract

Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. [...] Read more.

Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering. Full article

(This article belongs to the Special Issue Ceramics for Healthcare)

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16 pages, 2643 KiB

Open AccessReview

Novel Bioactive Titanate Layers Formed on Ti Metal and Its Alloys by Chemical Treatments

by Tadashi Kokubo^* and Seiji Yamaguchi

Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi, 487-8501, Japan

Materials 2010, 3(1), 48-63; https://doi.org/10.3390/ma3010048 - 25 Dec 2009

Cited by 65 | Viewed by 17368

Abstract

Sodium titanate formed on Ti metal by NaOH and heat treatments induces apatite formation on its surface in a body environment and bonds to living bone. These treatments have been applied to porous Ti metal in artificial hip joints, and have been used [...] Read more.

Sodium titanate formed on Ti metal by NaOH and heat treatments induces apatite formation on its surface in a body environment and bonds to living bone. These treatments have been applied to porous Ti metal in artificial hip joints, and have been used clinically in Japan since 2007. Calcium titanate formed on Ti-15Zr-4Nb-4Ta alloy by NaOH, CaCl₂, heat, and water treatments induces apatite formation on its surface in a body environment. Titanium oxide formed on porous Ti metal by NaOH, HCl, and heat treatments exhibits osteoinductivity as well as osteoconductivity. This is now under clinical tests for application to a spinal fusion device. Full article

(This article belongs to the Special Issue Ceramics for Healthcare)

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12 pages, 616 KiB

Open AccessArticle

Coordination of {Mo142} Ring to La3+ Provides Elliptical {Mo134La10} Ring with a Variety of Coordination Modes

by Eri Ishikawa^1,2, Yutaka Yano^1,3 and Toshihiro Yamase^1,4,*

¹ Chemical Resources Laboratory, Tokyo Institute of Technology, R1-21, 4259 Nagatsuta, Midori-ku, Yokohama 226–850, Japan

² Department of Applied Chemistry, College of Engineering, Chubu University, 1200 Matsumoto, Kasugai, Aichi 487–8501, Japan

³ Matsuda Sangyo Co., Ltd., Shinjuku Nomura Building 6th Fl., 1-26-2 Nishishinjuku, Shinjuku-ku, Tokyo 163–0558, Japan

⁴ (Inc.) MO Device, 2-14-10 Kanaiwa-higashi, Kanazawa 920–0335, Japan

Materials 2010, 3(1), 64-75; https://doi.org/10.3390/ma3010064 - 28 Dec 2009

Cited by 7 | Viewed by 15536

Abstract

A28-electron reduced C_2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo₁₄₂O₄₂₉H₁₀(H₂O)₄₉(CH₃CO₂)₅(C₂H₅CO₂)]^30- (≡{Mo₁₄₂(CH₃CO₂)₅ [...] Read more.

A28-electron reduced C_2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo₁₄₂O₄₂₉H₁₀(H₂O)₄₉(CH₃CO₂)₅(C₂H₅CO₂)]^30- (≡{Mo₁₄₂(CH₃CO₂)₅(C₂H₅CO₂)}) comprising eight carboxylate-coordinated (with disorder) {Mo₂} linkers and six defect pockets in two inner rings (four and three for each, respectively), reacts with La³⁺ in aqueous solutions at pH 3.5 to yield a 28-electron reduced elliptical C_i-Mo-blue ring of formula [Mo₁₃₄O₄₁₆H₂₀(H₂O)₄₆{La(H₂O)₅}₄{La(H₂O)₇}₄{LaCl₂(H₂O)₅}₂]^10- (≡{Mo₁₃₄La₁₀}), isolated as the Na₁₀[Mo₁₃₄O₄₁₆H₂₀(H₂O)₄₆{La(H₂O)₅}₄{La(H₂O)₇}₄{LaCl₂(H₂O)₅}₂]·144 H₂O Na⁺ salt. The elliptical structure of {Mo₁₃₄La₁₀} showing 36 and 31 Å long and short axes for the outer ring diameters is attributed to four (A-D) modes of LaO₉/LaO₇Cl₂tricapped-trigonal-prismatic coordination (TTP) geometries. Two different LaO₂(H₂O)₇ and one LaO₂(H₂O)₂Cl₂ TTP geometries (as A-C modes) for each of two inner rings result from the coordination of all three defect pockets of the inner ring for {Mo₁₄₂(CH₃CO₂)₅(C₂H₅CO₂)}, and two LaO₄(H₂O)₅ TTP geometries (as D mode) result from the displacement of two (acetate/propionate-coordinated) binuclear {Mo₂} linkers with La³⁺ in each inner ring. The isothermal titration calorimetry (ITC) of the ring modification from circle to ellipsoid, showing the endothermic reaction of [La³⁺]/[{Mo₁₄₂(CH₃CO₂)₅(C₂H₅CO₂)}] = 6/1 with DH = 22 kJ×mol^-1, DS = 172 J×K^-1×mol^-1, DG = −28 kJ×mol^-1, and K = 9.9 ´ 10⁴ M^-1at 293 K, leads to the conclusion that the coordination of the defect pockets to La³⁺ precedes the replacement of the {Mo₂} linkers with La³⁺. ¹³⁹La- NMR spectrometry of the coordination of {Mo₁₄₂(CH₃CO₂)₅(C₂H₅CO₂)} ring to La³⁺ is also discussed. Full article

(This article belongs to the Special Issue Polyoxometalate Compounds)

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21 pages, 843 KiB

Open AccessReview

Dental Glass Ionomer Cements as Permanent Filling Materials? – Properties, Limitations and Future Trends

by Ulrich Lohbauer

Dental Materials Lab, Dental Clinic 1, University of Erlangen-Nuremberg, Glueckstrasse 11, 91054 Erlangen, Germany

Materials 2010, 3(1), 76-96; https://doi.org/10.3390/ma3010076 - 28 Dec 2009

Cited by 207 | Viewed by 43641

Abstract

Glass ionomer cements (GICs) are clinically attractive dental materials that have certain unique properties that make them useful as restorative and luting materials. This includes adhesion to moist tooth structures and base metals, anticariogenic properties due to release of fluoride, thermal compatibility with [...] Read more.

Glass ionomer cements (GICs) are clinically attractive dental materials that have certain unique properties that make them useful as restorative and luting materials. This includes adhesion to moist tooth structures and base metals, anticariogenic properties due to release of fluoride, thermal compatibility with tooth enamel, biocompatibility and low toxicity. The use of GICs in a mechanically loaded situation, however, has been hampered by their low mechanical performance. Poor mechanical properties, such as low fracture strength, toughness and wear, limit their extensive use in dentistry as a filling material in stress-bearing applications. In the posterior dental region, glass ionomer cements are mostly used as a temporary filling material. The requirement to strengthen those cements has lead to an ever increasing research effort into reinforcement or strengthening concepts. Full article

(This article belongs to the Special Issue Ceramics for Healthcare)

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13 pages, 1622 KiB

Open AccessArticle

Improved Mechanical and Tribological Properties of Metal-Matrix Composites Dispersion-Strengthened by Nanoparticles

by Evgenii Levashov, Victoria Kurbatkina and Zaytsev Alexandr^*

Moscow Institute of Steel and Alloys, Leninskii pr. 4, Moscow, 119049, Russia

Materials 2010, 3(1), 97-109; https://doi.org/10.3390/ma3010097 - 29 Dec 2009

Cited by 45 | Viewed by 16590

Abstract

Co- and Fe-based alloys produced by powder technology are being widely used as a matrix for diamond-containing composites in cutting, drilling, grinding pplications, etc. The severe service conditions demand that the mechanical and tribological properties of these alloys be improved. Development of metal-matrix [...] Read more.

Co- and Fe-based alloys produced by powder technology are being widely used as a matrix for diamond-containing composites in cutting, drilling, grinding pplications, etc. The severe service conditions demand that the mechanical and tribological properties of these alloys be improved. Development of metal-matrix composites (MMCs) and alloys reinforced with nanoparticles is a promising way to resolve this problem. In this work, we have investigated the effect of nano-sized WC, ZrO₂, Al₂O₃, and Si₃N₄ additives on the properties of sintered dispersion-strengthened Co- and Fe-based MMCs. The results show an increase in the hardness (up to 10 HRB), bending strength (up to 50%), wear resistance (by a factor of 2–10) and a decrease in the friction coefficient (up to 4-fold) of the dispersion-strengthened materials. The use of designed alloys as a binder of cutting diamond tools gave a 4-fold increment in the service life, without reduction in their cutting speed. Full article

(This article belongs to the Special Issue Composite Materials)

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17 pages, 1142 KiB

Open AccessReview

Characterization of Bronze Surface Layer Formed by Microarc Oxidation Process in 12-Tungstophosphoric Acid

by Ubavka B. Mioč^1,*, Stevan Stojadinović² and Zoran Nedić¹

¹ Faculty of Physical Chemistry, University of Belgrade, P.O. Box 47, 11158 Belgrade 118, PAC 105305, Serbia

² Faculty of Physics, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia

Materials 2010, 3(1), 110-126; https://doi.org/10.3390/ma3010110 - 31 Dec 2009

Cited by 16 | Viewed by 15352

Abstract

This paper is a brief review of our recent research into novel uses for heteropoly compounds as precursors for thin films that can be used as catalysts and materials with good optical, conductive and other characteristics. In view of this, we have chosen [...] Read more.

This paper is a brief review of our recent research into novel uses for heteropoly compounds as precursors for thin films that can be used as catalysts and materials with good optical, conductive and other characteristics. In view of this, we have chosen thin film obtained with 12-tungsphosphoric acid on aluminum substrates. In all cases, a relatively new, microarc oxidation technique has been used to prepare oxide coatings on substrate surfaces. Advanced physicochemical methods, AFM and SEM-EDS, XRD, Raman and Micro-Raman, and luminescence spectroscopy, as the most powerful techniques, have been used for the characterization of new materials. Possible applications have been discussed as well. Full article

(This article belongs to the Special Issue Polyoxometalate Compounds)

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23 pages, 2881 KiB

Open AccessReview

Recent Developments in Carbon Nanotube Membranes for Water Purification and Gas Separation

by Kallista Sears^1,*, Ludovic Dumée^1,2, Jürg Schütz¹, Mary She³, Chi Huynh¹, Stephen Hawkins¹, Mikel Duke²

and Stephen Gray²

¹ CSIRO Materials Science and Engineering, Bayview Ave, Clayton Vic 3168, Australia

² Institute for Sustainability and Innovation, Victoria University, Werribee Campus, Hoppers Lane, Werribee PO Box 14428, Melbourne, Victoria, 8001, Australia

³ Centre for Material and Fibre Innovation, Institute for Technology and Research Innovation, Deakin University, Geelong Vic 3217, Australia

Materials 2010, 3(1), 127-149; https://doi.org/10.3390/ma3010127 - 4 Jan 2010

Cited by 253 | Viewed by 28226

Abstract

Carbon nanotubes (CNTs) are nanoscale cylinders of graphene with exceptional properties such as high mechanical strength, high aspect ratio and large specific surface area. To exploit these properties for membranes, macroscopic structures need to be designed with controlled porosity and pore size. This [...] Read more.

Carbon nanotubes (CNTs) are nanoscale cylinders of graphene with exceptional properties such as high mechanical strength, high aspect ratio and large specific surface area. To exploit these properties for membranes, macroscopic structures need to be designed with controlled porosity and pore size. This manuscript reviews recent progress on two such structures: (i) CNT Bucky-papers, a non-woven, paper like structure of randomly entangled CNTs, and (ii) isoporous CNT membranes, where the hollow CNT interior acts as a membrane pore. The construction of these two types of membranes will be discussed, characterization and permeance results compared, and some promising applications presented. Full article

(This article belongs to the Special Issue Porous Materials)

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8 pages, 349 KiB

Open AccessArticle

Syntheses and a Solid State Structure of a Dinuclear Molybdenum(V) Complex with Pyridine

by Barbara Modec^1,*

and Jon Zubieta²

¹ Department of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia

² Department of Chemistry, Syracuse University, Syracuse, New York, NY 13244, USA

Materials 2010, 3(1), 150-157; https://doi.org/10.3390/ma3010150 - 4 Jan 2010

Cited by 5 | Viewed by 14259

Abstract

A mononuclear complex [MoOCl₄(H₂O)]⁻ readily forms a metal−metal bonded {Mo₂O₄}²⁺ core. A high content of pyridine in the reaction mixture prevents further aggregation of dinuclear cores into larger clusters and a neutral, dinuclear [...] Read more.

A mononuclear complex [MoOCl₄(H₂O)]⁻ readily forms a metal−metal bonded {Mo₂O₄}²⁺ core. A high content of pyridine in the reaction mixture prevents further aggregation of dinuclear cores into larger clusters and a neutral, dinuclear complex with the [Mo₂O₄Cl₂(Py)₄] composition is isolated as a product. Solid state structures of two compounds containing this complex, [Mo₂O₄Cl₂(Py)₄]·2.25Py (1) and [Mo₂O₄Cl₂(Py)₄]·1.5PyHCl (2), were investigated by X-ray crystallography. Full article

(This article belongs to the Special Issue Polyoxometalate Compounds)

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7 pages, 480 KiB

Open AccessArticle

Controllable Layered Structures in Polyoxomolybdate-Surfactant Hybrid Crystals

by Takeru Ito^1,2,*

and Toshihiro Yamase^1,3,*

¹ Chemical Resources Laboratory, Tokyo Institute of Technology, R1-21, 4259 Nagatsuta, Midoriku, Yokohama 226–8503, Japan

² Department of Chemistry, School of Science, Tokai University, 1117 Kitakaname, Hiratsuka 259–1292, Japan

³ (Inc.) MO Device, 2-14-10 Kanaiwa-higashi, Kanazawa 920–0335, Japan

Materials 2010, 3(1), 158-164; https://doi.org/10.3390/ma3010158 - 6 Jan 2010

Cited by 15 | Viewed by 14204

Abstract

Inorganic-organic hybrid crystals containing α-octamolybdate (Mo₈) or hexamolybdate (Mo₆) were isolated by using hexadecyltrimethylammonium (C₁₆) surfactant. The packing mode of the inorganic layers depended on a difference in the polyoxomolybdate molecular structure. The structure for both crystals [...] Read more.

Inorganic-organic hybrid crystals containing α-octamolybdate (Mo₈) or hexamolybdate (Mo₆) were isolated by using hexadecyltrimethylammonium (C₁₆) surfactant. The packing mode of the inorganic layers depended on a difference in the polyoxomolybdate molecular structure. The structure for both crystals consisted of alternate stacking of C₁₆ organic bilayers and polyoxomolybdate inorganic layers with a periodicity of 24.4–24.6 Å. However, the C₁₆-Mo₈crystals contained Mo8 monolayers, while the C₁₆-Mo₆ crystals contained Mo₆ bilayers. These lattice structures for the polyoxometalate/organic hybrid will be designed by the molecular structures of polyoxometalate. Full article

(This article belongs to the Special Issue Inorganic-Organic Hybrid Materials)

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36 pages, 3848 KiB

Open AccessReview

Functionalization of Artificial Freestanding Composite Nanomembranes

by Zoran Jakšić^1,* and Jovan Matovic²

¹ Center of Microelectronic Technologies and Single Crystals (CMTM), Institute of Chemistry, Technology and Metallurgy (IHTM), University of Belgrade, Njegoševa 12, 11000 Belgrade, Serbia

² Institute for Sensor and Actuator Systems (ISAS), Faculty of Electrical Engineering & Information Technology, Vienna University of Technology, Gusshausstrasse 27-29/366-MST, A-1040 Vienna, Austria

Materials 2010, 3(1), 165-200; https://doi.org/10.3390/ma3010165 - 7 Jan 2010

Cited by 36 | Viewed by 21853

Abstract

Artificial nanomembranes may be defined as synthetic freestanding structures with a thickness below 100 nm and a very large aspect ratio, of at least a few orders of magnitude. Being quasi-2D, they exhibit a host of unusual properties useful for various applications in [...] Read more.

Artificial nanomembranes may be defined as synthetic freestanding structures with a thickness below 100 nm and a very large aspect ratio, of at least a few orders of magnitude. Being quasi-2D, they exhibit a host of unusual properties useful for various applications in energy harvesting, sensing, optics, plasmonics, biomedicine, etc. We review the main approaches to nanomembrane functionalization through nanocompositing, which ensures performance far superior to that of simple nanomembranes. These approaches include lamination (stacking of nanometer-thin strata of different materials), introduction of nanoparticle fillers into the nanomembrane scaffold, nanomembrane surface sculpting and modification through patterning (including formation of nanohole arrays and introduction of ion channels similar in function to those in biological nanomembranes). We also present some of our original results related to functionalization of metal matrix composite nanomembranes. Full article

(This article belongs to the Special Issue Composite Materials)

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15 pages, 496 KiB

Open AccessArticle

A New Approach for the Modification of Paper Surface Properties Using Polyoxometalates

by Mikhail S. Saraiva¹, José A. F. Gamelas^1,*, António P. Mendes de Sousa², Bruno M. Reis², José L. Amaral² and Paulo J. Ferreira^1,*

¹ Departamento de Engenharia Química, Universidade de Coimbra, Pólo II – R. Sílvio Lima, 3030-790 Coimbra, Portugal

² RAIZ – Instituto de Investigação da Floresta e Papel, Quinta de São Francisco, Apartado 15, 3801-501 Eixo, Portugal

Materials 2010, 3(1), 201-215; https://doi.org/10.3390/ma3010201 - 7 Jan 2010

Cited by 29 | Viewed by 17520

Abstract

A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented by [...] Read more.

A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented by coating pigments, namely H₃PW₁₂O₄₀·23H₂O, H₄SiW₁₂O₄₀·24H₂O, and K₇PW₁₁O₃₉·9H₂O, have been used in order to improve the quality of inkjet printing. The analysis of the different samples by FTIR-ATR spectroscopy showed the presence of the polyoxometalates (and the cationic starch) on the top surface of the paper. In addition, the determination of surface energy parameters, namely the polar component (σ_s^p) and the dispersive component (σ_s^d) of the surface energy, by contact angle measurements revealed that, for the new samples, the polar component level was much higher than that of the uncoated base paper. The quality of inkjet printing, evaluated by parameters such as the gamut area and the optical density, was considerably improved by these surface treatments. Full article

(This article belongs to the Special Issue Polyoxometalate Compounds)

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16 pages, 1130 KiB

Open AccessArticle

Effect of SO₂ Dry Deposition on Porous Dolomitic Limestones

by Mihaela Olaru^1,*, Magdalena Aflori¹, Bogdana Simionescu², Florica Doroftei¹ and Lacramioara Stratulat³

¹ Petru Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487, Iasi, Romania

² University of Oviedo, Department of Geology, Calle Jesus Arias de Velasco s/n, 33005 Oviedo, Spain

³ Moldova National Museum Complex, 1 Stefan cel Mare si Sfant Square, 700028, Iasi, Romania

Materials 2010, 3(1), 216-231; https://doi.org/10.3390/ma3010216 - 7 Jan 2010

Cited by 26 | Viewed by 19096

Abstract

The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain) used as building material in stone monuments and submitted to artificial ageing by SO₂ dry deposition in the presence of humidity. To [...] Read more.

The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain) used as building material in stone monuments and submitted to artificial ageing by SO₂ dry deposition in the presence of humidity. To investigate the protection efficiency of different polymeric coatings, three commercially available siloxane-based oligomers (Lotexan-N, Silres BS 290 and Tegosivin HL 100) and a newly synthesized hybrid nanocomposite with silsesquioxane units (TMSPMA) were used. A comparative assessment of the data obtained in this study underlines that a better limestone protection was obtained when treated with the hybrid nanocomposite with silsesquioxane units. Full article

(This article belongs to the Special Issue Composite Materials)

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9 pages, 448 KiB

Open AccessArticle

Families of Molecular Hexa- and Trideca-Metallic Vanadium(III) Phosphonates

by Sumit Khanra, Rachel Shaw, Madeleine Helliwell, Floriana Tuna, Christopher A. Muryn, Eric J. L. McInnes^* and Richard E. P. Winpenny^*

School of Chemistry, The University of Manchester, Manchester M13 9PL, UK

Materials 2010, 3(1), 232-240; https://doi.org/10.3390/ma3010232 - 8 Jan 2010

Cited by 6 | Viewed by 14472

Abstract

The synthesis and structural characterization of two families of low-valent vanadium(III) {V₆P₄} and vanadium(III/IV) {V₁₃P₈} phosphonate complexes are reported. Magnetic characterization is reported for representative examples. Full article

(This article belongs to the Special Issue Polyoxometalate Compounds)

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23 pages, 355 KiB

Open AccessReview

Scaffold Characteristics for Functional Hollow Organ Regeneration

by Maya Horst¹, Srinivas Madduri¹, Rita Gobet³, Tullio Sulser¹, Heike Hall² and Daniel Eberli^1,*

¹ Laboratory for Urologic Tissue Engineering and Stem Cell Therapy, Department of Urology, University Hospital, Zurich, Switzerland

² Cells and Biomaterials, Department of Materials, ETH Zurich, Switzerland

³ Division of Pediatric Urology, Department of Pediatric Surgery, University Children‘s Hospital, Zurich, Switzerland

Materials 2010, 3(1), 241-263; https://doi.org/10.3390/ma3010241 - 8 Jan 2010

Cited by 13 | Viewed by 18051

Abstract

Many medical conditions require surgical reconstruction of hollow organs. Tissue engineering of organs and tissues is a promising new technique without harvest site morbidity. An ideal biomaterial should be biocompatible, support tissue formation and provide adequate structural support. It should degrade gradually and [...] Read more.

Many medical conditions require surgical reconstruction of hollow organs. Tissue engineering of organs and tissues is a promising new technique without harvest site morbidity. An ideal biomaterial should be biocompatible, support tissue formation and provide adequate structural support. It should degrade gradually and provide an environment allowing for cell-cell interaction, adhesion, proliferation, migration, and differentiation. Although tissue formation is feasible, functionality has never been demonstrated. Mainly the lack of proper innervation and vascularisation are hindering contractility and normal function. In this chapter we critically review the current state of engineering hollow organs with a special focus on innervation and vascularisation. Full article

(This article belongs to the Special Issue Advances in Biomaterials)

32 pages, 2752 KiB

Open AccessReview

Interface Reactions and Synthetic Reaction of Composite Systems

by Joon Sik Park^* and Jeong Min Kim

Division of Advanced Engineering Materials, Hanbat National University, Daejeon, 305-719 Korea

Materials 2010, 3(1), 264-295; https://doi.org/10.3390/ma3010264 - 8 Jan 2010

Cited by 15 | Viewed by 15303

Abstract

Interface reactions in composite systems often determine their overall properties, since product phases usually formed at interfaces during composite fabrication processing make up a large portion of the composites. Since most composite materials represent a ternary or higher order materials system, many studies [...] Read more.

Interface reactions in composite systems often determine their overall properties, since product phases usually formed at interfaces during composite fabrication processing make up a large portion of the composites. Since most composite materials represent a ternary or higher order materials system, many studies have focused on analyses of diffusion phenomena and kinetics in multicomponent systems. However, the understanding of the kinetic behavior increases the complexity, since the kinetics of each component during interdiffusion reactions need to be defined for interpreting composite behaviors. From this standpoint, it is important to clarify the interface reactions for producing compatible interfaces with desired product phases. A thermodynamic evaluation such as a chemical potential of involving components can provide an understanding of the diffusion reactions, which govern diffusion pathways and product phase formation. A strategic approach for designing compatible interfaces is discussed in terms of chemical potential diagrams and interface morphology, with some material examples. Full article

(This article belongs to the Special Issue Composite Materials)

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22 pages, 197 KiB

Open AccessReview

On Micro-Macro Transition in Non-Linear Mechanics

by Claude Stolz

Lab. M´ecanique des Solides, Ecole polytechnique UMR 7649, 91128 Palaiseau Cedex France

Materials 2010, 3(1), 296-317; https://doi.org/10.3390/ma3010296 - 8 Jan 2010

Cited by 3 | Viewed by 14252

Abstract

This paper is devoted to the description of the general relationships between microscopic and macroscopic mechanical quantities in non-linear mechanics. From a thermodynamical viewpoint, it is only necessary to know the two macroscopic potentials (macroscopic free energy and macroscopic potential of dissipation) to [...] Read more.

This paper is devoted to the description of the general relationships between microscopic and macroscopic mechanical quantities in non-linear mechanics. From a thermodynamical viewpoint, it is only necessary to know the two macroscopic potentials (macroscopic free energy and macroscopic potential of dissipation) to describe the state of the body and its quasistatic evolution. These global potentials are the averages of the local ones. We point out some particular cases of non-linearities, especially the case of damaged materials. Full article

(This article belongs to the Special Issue Composite Materials)

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11 pages, 484 KiB

Open AccessArticle

The Effect of (Ag, Ni, Zn)-Addition on the Thermoelectric Properties of Copper Aluminate

by Shun-ichi Yanagiya^1,2,*, Ngo Van Nong², Jianxiao Xu² and Nini Pryds²

¹ Department of Electrical and Electronic Engineering, Hakodate National College of Technology, 14-1 Tokura, Hakodate, Hokkaido 042-8501, Japan

² Fuel Cells and Solid State Chemistry Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, Roskilde 4000, Denmark

Materials 2010, 3(1), 318-328; https://doi.org/10.3390/ma3010318 - 11 Jan 2010

Cited by 55 | Viewed by 16915

Abstract

Polycrystalline bulk copper aluminate Cu₁_-x-yAg_xB_yAlO₂ with B = Ni or Zn were prepared by spark plasma sintering and subsequent thermal treatment. The influence of partial substitution of Ag, Ni and Zn for Cu-sites in CuAlO [...] Read more.

Polycrystalline bulk copper aluminate Cu₁_-x-yAg_xB_yAlO₂ with B = Ni or Zn were prepared by spark plasma sintering and subsequent thermal treatment. The influence of partial substitution of Ag, Ni and Zn for Cu-sites in CuAlO₂ on the high temperature thermoelectric properties has been studied. The addition of Ag and Zn was found to enhance the formation of CuAlO₂ phase and to increase the electrical conductivity. The addition of Ag or Ag and Ni on the other hand decreases the electrical conductivity. The highest power factor of 1.26 × 10^-4 W/mK² was obtained for the addition of Ag and Zn at 1,060 K, indicating a significant improvement compared with the non-doped CuAlO₂ sample. Full article

(This article belongs to the Special Issue Novel Thermoelectric Materials and Applications)

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22 pages, 8971 KiB

Open AccessReview

Friction Stir Processing of Particle Reinforced Composite Materials

by Yong X. Gan^1,2,*, Daniel Solomon² and Michael Reinbolt¹

¹ Department of Mechanical, Industrial and Manufacturing Engineering, College of Engineering, University of Toledo, 2801 W Bancroft Street, Toledo, OH 43606, USA

² Department of Mechanical Engineering, Albert Nerken School of Engineering, The Cooper Union for the Advancement of Science and Art, 41 Cooper Square, New York, NY 10003, USA

Materials 2010, 3(1), 329-350; https://doi.org/10.3390/ma3010329 - 11 Jan 2010

Cited by 129 | Viewed by 25475

Abstract

The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have [...] Read more.

The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned. Full article

(This article belongs to the Special Issue Composite Materials)

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18 pages, 3290 KiB

Open AccessReview

Ceramics for Dental Applications: A Review

by Isabelle Denry^* and Julie A. Holloway

The Ohio State University College of Dentistry, 305 W 12th Avenue, Columbus, OH 43210, USA

Materials 2010, 3(1), 351-368; https://doi.org/10.3390/ma3010351 - 11 Jan 2010

Cited by 385 | Viewed by 38067

Abstract

Over the past forty years, the technological evolution of ceramics for dental applications has been remarkable, as new materials and processing techniques are steadily being introduced. The improvement in both strength and toughness has made it possible to expand the range of indications [...] Read more.

Over the past forty years, the technological evolution of ceramics for dental applications has been remarkable, as new materials and processing techniques are steadily being introduced. The improvement in both strength and toughness has made it possible to expand the range of indications to long-span fixed partial prostheses, implant abutments and implants. The present review provides a state of the art of ceramics for dental applications. Full article

(This article belongs to the Special Issue Ceramics for Healthcare)

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17 pages, 858 KiB

Open AccessArticle

Synthesis and Properties of Trehalose-Based Flexible Polymers Prepared from Difurfurylidene Trehalose and Maleimide- Terminated Oligo(dimethylsiloxane) by Diels-Alder Reactions

by Naozumi Teramoto^*, Masashi Niwa and Mitsuhiro Shibata

Department of Life and Environmental Sciences, Faculty of Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan

Materials 2010, 3(1), 369-385; https://doi.org/10.3390/ma3010369 - 12 Jan 2010

Cited by 12 | Viewed by 15257

Abstract

Difurfurylidene trehalose (DFTreh) was synthesized from trehalose and furfural by an acetalization reaction. Maleimide-terminated dimethylsiloxane oligomers (DMS-BMI) were synthesized from amine-terminated dimethylsiloxane oligomers by condensation with maleic anhydride. Three types of DMS-BMI with different length were prepared. Trehalose-based polymers were synthesized by Diels-Alder [...] Read more.

Difurfurylidene trehalose (DFTreh) was synthesized from trehalose and furfural by an acetalization reaction. Maleimide-terminated dimethylsiloxane oligomers (DMS-BMI) were synthesized from amine-terminated dimethylsiloxane oligomers by condensation with maleic anhydride. Three types of DMS-BMI with different length were prepared. Trehalose-based polymers were synthesized by Diels-Alder reaction of DFTreh and DMS-BMI. The reaction proceeded at 40~70 °C to produce a polymer with a maximum weight average molecular weight of ~19,000. The thermal degradation temperature increased with the increase of the length of the oligo(dimethylsiloxane) units. The differential scanning calorimetry (DSC) measurements revealed the glass transition temperature (T_g) of the polymer at -130~-120 °C, and no distinct T_g not observed above room temperature in the DSC measurement. The polymer products are not liquid at room temperature, and solid films can be obtained by casting from solution, implying a phase-separated structure made up of soft and hard segments. The phase-separated structure was confirmed by transmission electron microscope (TEM) study. The DSC curve of the polymer showed a broad endothermic peak at 110~160 °C, suggesting that a retro-Diels-Alder reaction occurred. When a N,N-dimethylformamide solution of the polymer was kept at 100 °C and the resulting solution was analyzed by gel permeation chromatography (GPC), the molecular weight decreased and monomers appeared. Full article

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15 pages, 407 KiB

Open AccessArticle

Description of Extrudate Swell for Polymer Nanocomposites

by Kejian Wang

Institute of Plastics Machinery and Engineering, Beijing University of Chemical and Technology, Beijing 100029, China

Materials 2010, 3(1), 386-400; https://doi.org/10.3390/ma3010386 - 12 Jan 2010

Cited by 11 | Viewed by 15871

Abstract

Extrudate swell is often observed to be weakened in nanocomposites compared to the pure polymer matrix. A theory quantifying this would be significant either for optimum processing or for understanding their viscoelasticity. A unified extrudate swell correlation with material properties and capillary parameters [...] Read more.

Extrudate swell is often observed to be weakened in nanocomposites compared to the pure polymer matrix. A theory quantifying this would be significant either for optimum processing or for understanding their viscoelasticity. A unified extrudate swell correlation with material properties and capillary parameters was suggested for polymer melt and their nanocomposites when considering the reservoir entry effect. More importantly, it was the first to find that the composite swell ratio can be the matrix swell ratio multiplied by the concentration shift factor, which is similar to the dynamic moduli expression for composites. The factor is a function of the shear field (stress or shear rate), filler content, filler internal structure and the surface state as well as the matrix properties. Several sets of swell data for nanocomposites were chosen from publications to test the new theories. The proposed quantitative model displayed good fit for the five kinds of nanocomposites, which verified the rationality of the swell theory for nanocomposites. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)

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33 pages, 873 KiB

Open AccessReview

Synthetic Fabrication of Nanoscale MoS₂-Based Transition Metal Sulfides

by Shutao Wang¹, Changhua An^1,* and Jikang Yuan^2,3

¹ College of Chemistry and Chemical Engineering, China University of Petroleum, Dongying, Shandong 257061, China

² College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China

³ Department of Applied Physics, The Hongkong Polytechnic University, Hung Hom, Hongkong, China

Materials 2010, 3(1), 401-433; https://doi.org/10.3390/ma3010401 - 12 Jan 2010

Cited by 58 | Viewed by 20992

Abstract

Transition metal sulfides are scientifically and technologically important materials. This review summarizes recent progress on the synthetic fabrication of transition metal sulfides nanocrystals with controlled shape, size, and surface functionality. Special attention is paid to the case of MoS₂ nanoparticles, where organic [...] Read more.

Transition metal sulfides are scientifically and technologically important materials. This review summarizes recent progress on the synthetic fabrication of transition metal sulfides nanocrystals with controlled shape, size, and surface functionality. Special attention is paid to the case of MoS₂ nanoparticles, where organic (surfactant, polymer), inorganic (support, promoter, doping) compounds and intercalation chemistry are applied. Full article

(This article belongs to the Special Issue Composite Materials)

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18 pages, 3850 KiB

Open AccessArticle

An Incremental Mori-Tanaka Homogenization Scheme for Finite Strain Thermoelastoplasticity of MMCs

by Heinz E. Pettermann^1,*, Christopher O. Huber², Mathias H. Luxner^2,3, Sergio Nogales¹ and Helmut J. Böhm¹

¹ Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gusshausstr. 27-29, A-1040 Vienna, Austria

² Austrian Aeronautics Research (AAR), Network for Materials and Engineering, Austria

³ Luxner Engineering ZT, Christian Plattner-Str. 4, A-6460 Imst, Austria

Materials 2010, 3(1), 434-451; https://doi.org/10.3390/ma3010434 - 13 Jan 2010

Cited by 31 | Viewed by 16672

Abstract

The present paper aims at computational simulations of particle reinforced Metal Matrix Composites as well as parts and specimens made thereof. An incremental Mori-Tanaka approach with isotropization of the matrix tangent operator is adopted. It is extended to account for large strains by [...] Read more.

The present paper aims at computational simulations of particle reinforced Metal Matrix Composites as well as parts and specimens made thereof. An incremental Mori-Tanaka approach with isotropization of the matrix tangent operator is adopted. It is extended to account for large strains by means of co-rotational Cauchy stresses and logarithmic strains and is implemented into Finite Element Method software as constitutive material law. Periodic unit cell predictions in the finite strain regime are used to verify the analytical approach with respect to non-proportional loading scenarios and assumptions concerning finite strain localization. The response of parts made of Metal Matrix Composites is predicted by a multiscale approach based on these two micromechanical methods. Results for the mesoscopic stress and strain fields as well as the microfields are presented to demonstrate to capabilities of the developed methods. Full article

(This article belongs to the Special Issue Composite Materials)

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15 pages, 287 KiB

Open AccessArticle

Removal of Mn, Fe, Ni and Cu Ions from Wastewater Using Cow Bone Charcoal

by Juan Carlos Moreno^1,*

, Rigoberto Gómez¹ and Liliana Giraldo²

¹ Facultad de Ciencias, Departamento de Química, Grupo de Investigación en Sólidos Porosos y Calorimetría, Universidad de los Andes, Colombia

² Facultad de Ciencias, Departamento de Química, Universidad Nacional de Colombia, Bogotá, Colombia

Materials 2010, 3(1), 452-466; https://doi.org/10.3390/ma3010452 - 14 Jan 2010

Cited by 111 | Viewed by 18661

Abstract

Cow bone charcoal (CBC) was synthesized and used for the removal of metals ions (manganese, iron, nickel and copper) from aqueous solutions. Two different adsorption models were used for analyzing the data. Adsorption capacities were determined: copper ions exhibit the greatest adsorption on [...] Read more.

Cow bone charcoal (CBC) was synthesized and used for the removal of metals ions (manganese, iron, nickel and copper) from aqueous solutions. Two different adsorption models were used for analyzing the data. Adsorption capacities were determined: copper ions exhibit the greatest adsorption on cow bone charcoal because of their size and pH conditions. Adsorption capacity varies as a function of pH. Adsorption isotherms from aqueous solution of heavy metals on CBC were determined. Adsorption isotherms are consistent with Langmuir´s adsorption model. Adsorbent quantity and immersion enthalpy were studied. Full article

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36 pages, 3696 KiB

Open AccessReview

A New Approach to the Computer Modeling of Amorphous Nanoporous Structures of Semiconducting and Metallic Materials: A Review

by Cristina Romero¹, Juan C. Noyola², Ulises Santiago¹, Renela M. Valladares², Alexander Valladares² and Ariel A. Valladares^1,*

¹ Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Ciudad Universitaria, Apartado Postal 70-360, México, D.F. 04510, Mexico

² Facultad de Ciencias, Universidad Nacional Autónoma de México / Ciudad Universitaria, Apartado Postal 70-542, México, D.F. 04510, Mexico

Materials 2010, 3(1), 467-502; https://doi.org/10.3390/ma3010467 - 15 Jan 2010

Cited by 18 | Viewed by 18003

Abstract

We review our approach to the generation of nanoporous materials, both semiconducting and metallic, which leads to the existence of nanopores within the bulk structure. This method, which we have named as the expanding lattice method, is a novel transferable approach which consists [...] Read more.

We review our approach to the generation of nanoporous materials, both semiconducting and metallic, which leads to the existence of nanopores within the bulk structure. This method, which we have named as the expanding lattice method, is a novel transferable approach which consists first of constructing crystalline supercells with a large number of atoms and a density close to the real value and then lowering the density by increasing the volume. The resulting supercells are subjected to either ab initio or parameterized—Tersoff-based—molecular dynamics processes at various temperatures, all below the corresponding bulk melting points, followed by geometry relaxations. The resulting samples are essentially amorphous and display pores along some of the “crystallographic” directions without the need of incorporating ad hoc semiconducting atomic structural elements such as graphene-like sheets and/or chain-like patterns (reconstructive simulations) or of reproducing the experimental processes (mimetic simulations). We report radial (pair) distribution functions, nanoporous structures of C and Si, and some computational predictions for their vibrational density of states. We present numerical estimates and discuss possible applications of semiconducting materials for hydrogen storage in potential fuel tanks. Nanopore structures for metallic elements like Al and Au also obtained through the expanding lattice method are reported. Full article

(This article belongs to the Special Issue Porous Materials)

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16 pages, 518 KiB

Open AccessArticle

Transformation of Tri-Titanium(IV)-Substituted α-Keggin Polyoxometalate (POM) into Tetra-Titanium(IV)-Substituted POMs : Reaction Products of Titanium(IV) Sulfate with the Dimeric Keggin POM Precursor under Acidic Conditions

by Yuki Mouri, Yoshitaka Sakai, Yoshitaka Kobayashi, Shoko Yoshida and Kenji Nomiya^*

Department of Materials Science, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan

Materials 2010, 3(1), 503-518; https://doi.org/10.3390/ma3010503 - 15 Jan 2010

Cited by 11 | Viewed by 17504

Abstract

Reaction products of titanium(IV) sulfate in HCl-acidic aqueous solution with the dimeric species linked through three intermolecular Ti-O-Ti bonds of the two tri-titanium(IV)-substituted α-Keggin polyoxometalate (POM) subunits are described. Two novel titanium(IV)-containing α-Keggin POMs were obtained under different conditions. One product was a [...] Read more.

Reaction products of titanium(IV) sulfate in HCl-acidic aqueous solution with the dimeric species linked through three intermolecular Ti-O-Ti bonds of the two tri-titanium(IV)-substituted α-Keggin polyoxometalate (POM) subunits are described. Two novel titanium(IV)-containing α-Keggin POMs were obtained under different conditions. One product was a dimeric species through two intermolecular Ti-O-Ti bonds of the two tetra-titanium(IV)-substituted α-Keggin POM subunits, i.e., [[{Ti(H₂O)₃}₂(μ-O)](α-PW₉Ti₂O₃₈)]₂^6- (1). The other product was a monomeric α-Keggin species containing the tetra-titanium(IV) oxide cluster and two coordinated sulfate ions, i.e., [{Ti₄(μ-O)₃(SO₄)₂(H₂O)₈}(α-PW₉O₃₄)]^3- (2). Molecular structures of 1 and 2 were also discussed based on host (lacunary site)-guest (titanium atom) chemistry. Full article

(This article belongs to the Special Issue Polyoxometalate Compounds)

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17 pages, 560 KiB

Open AccessReview

Brushite-Forming Mg-, Zn- and Sr-Substituted Bone Cements for Clinical Applications

by Sandra Pina^* and José M.F. Ferreira

Department of Ceramics and Glass Engineering, University of Aveiro, CICECO, 3810-193 Aveiro, Portugal

Materials 2010, 3(1), 519-535; https://doi.org/10.3390/ma3010519 - 18 Jan 2010

Cited by 64 | Viewed by 17036

Abstract

Calcium phosphate cements have been in clinical use for the last 10 years. Their most salient features include good biocompatibility, excellent bioactivity, self-setting characteristics, low setting temperature, adequate stiffness, and easy shaping to accomodate any complicated geometry. They are commonly used in filling [...] Read more.

Calcium phosphate cements have been in clinical use for the last 10 years. Their most salient features include good biocompatibility, excellent bioactivity, self-setting characteristics, low setting temperature, adequate stiffness, and easy shaping to accomodate any complicated geometry. They are commonly used in filling bone defects and trauma surgeries as mouldable paste-like bone substitute materials. Substitution of trace elements, such as Mg, Sr and Zn ions, into the structure of calcium phosphates is the subject of widespread investigation nowadays, because of their impending role in the biological process. Subtle differences in composition and structure of these materials may have a profound effect on their in vivo behaviour. Therefore, the main goal of this paper is to provide a simple, but comprehensive overview of the present achievements relating to brushite-forming cements doped with Mg, Zn and Sr, and to identify new developments and trends. In particular, the influence of ionic substitution on the chemical, physical and biological properties of these materials is discussed. Full article

(This article belongs to the Special Issue Ceramics for Healthcare)

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27 pages, 349 KiB

Open AccessReview

Porous Dielectrics in Microelectronic Wiring Applications

by Vincent McGahay

International Business Machines Corporation, 2070 Route 52, Hopewell Junction, NY 12533, USA

Materials 2010, 3(1), 536-562; https://doi.org/10.3390/ma3010536 - 18 Jan 2010

Cited by 44 | Viewed by 17470

Abstract

Porous insulators are utilized in the wiring structure of microelectronic devices as a means of reducing, through low dielectric permittivity, power consumption and signal delay in integrated circuits. They are typically based on low density modifications of amorphous SiO₂ known as SiCOH [...] Read more.

Porous insulators are utilized in the wiring structure of microelectronic devices as a means of reducing, through low dielectric permittivity, power consumption and signal delay in integrated circuits. They are typically based on low density modifications of amorphous SiO₂ known as SiCOH or carbon-doped oxides, in which free volume is created through the removal of labile organic phases. Porous dielectrics pose a number of technological challenges related to chemical and mechanical stability, particularly in regard to semiconductor processing methods. This review discusses porous dielectric film preparation techniques, key issues encountered, and mitigation strategies. Full article

(This article belongs to the Special Issue Porous Materials)

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9 pages, 727 KiB

Open AccessArticle

Diode Laser Assisted Filament Winding of Thermoplastic Matrix Composites

by Fabrizio Quadrini^*, Erica Anna Squeo and Claudia Prosperi

Department of Mechanical Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy

Materials 2010, 3(1), 563-571; https://doi.org/10.3390/ma3010563 - 20 Jan 2010

Cited by 9 | Viewed by 16821

Abstract

A new consolidation method for the laser-assisted filament winding of thermoplastic prepregs is discussed: for the first time a diode laser is used, as well as long glass fiber reinforced polypropylene prepregs. A consolidation apparatus was built by means of a CNC motion [...] Read more.

A new consolidation method for the laser-assisted filament winding of thermoplastic prepregs is discussed: for the first time a diode laser is used, as well as long glass fiber reinforced polypropylene prepregs. A consolidation apparatus was built by means of a CNC motion table, a stepper motor and a simple tensioner. Preliminary tests were performed in a hoop winding configuration: only the winding speed was changed, and all the other process parameters (laser power, distance from the laser focus, consolidation force) were kept constant. Small wound rings with an internal diameter of 25 mm were produced and compression tests were carried out to evaluate the composite agglomeration in dependence of the winding speed. At lower winding speeds, a stronginterpenetration of adjacent layers was observed. Full article

(This article belongs to the Special Issue Composite Materials)

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13 pages, 714 KiB

Open AccessArticle

Thermo-Exfoliated Graphite Containing CuO/Cu₂(OH)₃NO₃:(Co²⁺/Fe³⁺) Composites: Preparation, Characterization and Catalytic Performance in CO Conversion

by Elena V. Ischenko, Ludmila Yu. Matzui, Snezhanna V. Gayday, Ludmila L. Vovchenko, Tatyana V. Kartashova and Vladyslav V. Lisnyak^*

Kyiv Taras Shevchenko National University, 64 Volodymyrska str., UA-01033, Kyiv, Ukraine

Materials 2010, 3(1), 572-584; https://doi.org/10.3390/ma3010572 - 20 Jan 2010

Cited by 24 | Viewed by 17147

Abstract

Thermo-exfoliated graphite (TEG)/CuO/Cu₂(OH)₃NO₃:(Co²⁺/Fe³⁺) composites were prepared using a wet impregnation method and subsequent thermal treatment. The physicochemical characterization of the composites was carried out by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) [...] Read more.

Thermo-exfoliated graphite (TEG)/CuO/Cu₂(OH)₃NO₃:(Co²⁺/Fe³⁺) composites were prepared using a wet impregnation method and subsequent thermal treatment. The physicochemical characterization of the composites was carried out by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Ar temperature-desorption techniques. The catalytic efficiency toward CO conversion to CO₂ was examined under atmospheric pressure. Characterization of species adsorbed over the composites taken after the activity tests were performed by means of temperature programmed desorption massspectrometry (TPD MS). (TEG)/CuO/Cu₂(OH)₃NO₃:(Co²⁺/Fe³⁺) composites show superior performance results if lower temperatures and extra treatment with H₂SO₄ or HNO₃ are used at the preparation stages. The catalytic properties enhancements can be related to the Cu₂(OH)₃NO₃ phase providing reaction centers for the CO conversion. It has been found that prevalence of low-temperature states of desorbed CO₂ over high-temperature ones in the TPD MS spectra is characteristic of the most active composite catalysts. Full article

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29 pages, 640 KiB

Open AccessReview

Geometrical Description in Binary Composites and Spectral Density Representation

by Enis Tuncer

Applied Superconductivity Group, Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6122, USA

Materials 2010, 3(1), 585-613; https://doi.org/10.3390/ma3010585 - 21 Jan 2010

Cited by 25 | Viewed by 16490

Abstract

In this review, the dielectric permittivity of dielectric mixtures is discussed in view of the spectral density representation method. A distinct representation is derived for predicting the dielectric properties, permittivities ε, of mixtures. The presentation of the dielectric properties is based on [...] Read more.

In this review, the dielectric permittivity of dielectric mixtures is discussed in view of the spectral density representation method. A distinct representation is derived for predicting the dielectric properties, permittivities ε, of mixtures. The presentation of the dielectric properties is based on a scaled permittivity approach, ξ = (ε_e − ε_m)(ε_i − ε_m)⁻¹, where the subscripts e, m and i denote the dielectric permittivities of the effective, matrix and inclusion media, respectively [Tuncer, E. J. Phys.: Condens. Matter 2005, 17, L125]. This novel representation transforms the spectral density formalism to a form similar to the distribution of relaxation times method of dielectric relaxation. Consequently, I propose that any dielectric relaxation formula, i.e., the Havriliak-Negami empirical dielectric relaxation expression, can be adopted as a scaled permittivity. The presented scaled permittivity representation has potential to be improved and implemented into the existing data analyzing routines for dielectric relaxation; however, the information to extract would be the topological/morphological description in mixtures. To arrive at the description, one needs to know the dielectric properties of the constituents and the composite prior to the spectral analysis. To illustrate the strength of the representation and confirm the proposed hypothesis, the Landau-Lifshitz/Looyenga (LLL) [Looyenga, H. Physica 1965, 31, 401] expression is selected. The structural information of a mixture obeying LLL is extracted for different volume fractions of phases. Both an in-house computational tool based on the Monte Carlo method to solve inverse integral transforms and the proposed empirical scaled permittivity expression are employed to estimate the spectral density function of the LLL expression. The estimated spectral functions for mixtures with different inclusion concentration compositions show similarities; they are composed of a couple of bell-shaped distributions, with coinciding peak locations but different heights. It is speculated that the coincidence in the peak locations is an absolute illustration of the self-similar fractal nature of the mixture topology (structure) created with the LLL expression. Consequently, the spectra are not altered significantly with increased filler concentration level—they exhibit a self-similar spectral density function for different concentration levels. Last but not least, the estimated percolation strengths also confirm the fractal nature of the systems characterized by the LLL mixture expression. It is concluded that the LLL expression is suitable for complex composite systems that have hierarchical order in their structure. These observations confirm the finding in the literature. Full article

(This article belongs to the Special Issue Composite Materials)

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24 pages, 516 KiB

Open AccessReview

Semiconductor Nanocrystals Hybridized with Functional Ligands: New Composite Materials with Tunable Properties

by Matthew McDowell, Ashley E. Wright and Nathan I. Hammer^*

Department of Chemistry & Biochemistry, The University of Mississippi, Coulter Hall 113, MS 38677 USA

Materials 2010, 3(1), 614-637; https://doi.org/10.3390/ma3010614 - 22 Jan 2010

Cited by 22 | Viewed by 18058

Abstract

Semiconductor nanocrystals hybridized with functional ligands represent an important new class of composite nanomaterials. The development of these new nanoscale building blocks has intensified over the past few years and offer significant advantages in a wide array of applications. Functional ligands allow for [...] Read more.

Semiconductor nanocrystals hybridized with functional ligands represent an important new class of composite nanomaterials. The development of these new nanoscale building blocks has intensified over the past few years and offer significant advantages in a wide array of applications. Functional ligands allow for incorporation of nanocrystals into areas where their unique photophysics can be exploited. Energy and charge transfer between the ligands and the nanocrystal also result in enhanced physical properties that can be tuned by the choice of ligand architecture. Here, progress in the development and applications involving this new class of composite materials will be discussed. Full article

(This article belongs to the Special Issue Composite Materials)

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18 pages, 97 KiB

Open AccessReview

Current Strategies in Cardiovascular Biomaterial Functionalization

by Simon Schopka^1,*, Thomas Schmid², Christof Schmid¹ and Karla Lehle¹

¹ Department of Cardiothoracic Surgery, University Medical Center Regensburg, D-93042 Regensburg, Germany

² German Aerospace Center, Institute of Robotics and Mechatronics Robotic and Mechatronic Robotic Systems, D-82234 Oberpfaffenhofen-Wessling, Germany

Materials 2010, 3(1), 638-655; https://doi.org/10.3390/ma3010638 - 22 Jan 2010

Cited by 33 | Viewed by 17266

Abstract

Prevention of the coagulation cascade and platelet activation is the foremost demand for biomaterials in contact with blood. In this review we describe the underlying mechanisms of these processes and offer the current state of antithrombotic strategies. We give an overview of methods [...] Read more.

Prevention of the coagulation cascade and platelet activation is the foremost demand for biomaterials in contact with blood. In this review we describe the underlying mechanisms of these processes and offer the current state of antithrombotic strategies. We give an overview of methods to prevent protein and platelet adhesion, as well as techniques to immobilize biochemically active molecules on biomaterial surfaces. Finally, recent strategies in biofunctionalization by endothelial cell seeding as well as their possible clinical applications are discussed. Full article

(This article belongs to the Special Issue Biocompatibility of Materials)

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16 pages, 874 KiB

Open AccessArticle

Electrical and Electrorheological Properties of Alumina/Natural Rubber (STR XL) Composites

by Nuchnapa Tangboriboon¹, Nuttapot Uttanawanit¹, Mean Longtong¹, Piraya Wongpinthong¹, Anuvat Sirivat^2,* and Ruksapong Kunanuruksapong²

¹ Department of Materials Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand

² The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand

Materials 2010, 3(1), 656-671; https://doi.org/10.3390/ma3010656 - 22 Jan 2010

Cited by 14 | Viewed by 15515

Abstract

The electrorheological properties (ER) of natural rubber (XL)/alumina (Al₂O₃) composites were investigated in oscillatory shear mode under DC electrical field strengths between 0 to 2 kV/mm. SEM micrographs indicate a mean particle size of 9.873 ± 0.034 µm and [...] Read more.

The electrorheological properties (ER) of natural rubber (XL)/alumina (Al₂O₃) composites were investigated in oscillatory shear mode under DC electrical field strengths between 0 to 2 kV/mm. SEM micrographs indicate a mean particle size of 9.873 ± 0.034 µm and particles that are moderately dispersed in the matrix. The XRD patterns indicate Al₂O₃ is of the β-phase polytype which possesses high ionic conductivity. The storage modulus (G′) of the composites, or the rigidity, increases by nearly two orders of magnitude, with variations in particle volume fraction and electrical field strength. The increase in the storage modulus is caused the ionic polarization of the alumina particles and the induced dipole moments set up in the natural rubber matrix. Full article

(This article belongs to the Special Issue Composite Materials)

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10 pages, 376 KiB

Open AccessArticle

Preparation of Multi-Walled Carbon Nanotube/Amino-Terminated Ionic Liquid Arrays and Their Electrocatalysis towards Oxygen Reduction

by Zhijuan Wang^1,2, Rose-Marie Latonen¹, Carita Kvarnström^1,†, Ari Ivaska^1,* and Li Niu^1,2,*

¹ Laboratory of Analytical Chemistry, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, FI-20500 Turku/Åbo, Finland

² State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, and Graduate University of the Chinese Academy of Sciences, Chinese Academy of Sciences, Changchun 130022, China

^† Current address: Department of Chemistry, University of Turku, FI-20014 Turku, Finland

Materials 2010, 3(1), 672-681; https://doi.org/10.3390/ma3010672 - 25 Jan 2010

Cited by 15 | Viewed by 16052

Abstract

Arrays of aligned multi-walled carbon nanotube-ionic liquid (MIL) were assembled on silicon wafers (Si-MIL). Formation of Si-MIL was confirmed by ATR-FTIR, AFM and Raman techniques. The electrochemical measurements indicated that Si-MIL showed good electrocatalysis towards oxygen reduction compared with MIL drop-cast on a [...] Read more.

Arrays of aligned multi-walled carbon nanotube-ionic liquid (MIL) were assembled on silicon wafers (Si-MIL). Formation of Si-MIL was confirmed by ATR-FTIR, AFM and Raman techniques. The electrochemical measurements indicated that Si-MIL showed good electrocatalysis towards oxygen reduction compared with MIL drop-cast on a glassy carbon electrode. Full article

(This article belongs to the Special Issue Composite Materials)

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22 pages, 614 KiB

Open AccessReview

Inorganic Hybrid Materials with Encapsulated Polyoxometalates

by Véronique Dufaud^1,* and Frédéric Lefebvre^2,*

¹ Laboratoire de Chimie, Université de Lyon, UMR 5182 CNRS-ENS Lyon, 46 Allée d'Italie, F-69364 Lyon cedex 07, France

² Laboratoire de Chimie, Catalyse, Polymères et Procédés, Université de Lyon, UMR 5265 CNRS-CPE Lyon, 43 bd du 11 Novembre 1918, 69622 Villeurbanne cedex, France

Materials 2010, 3(1), 682-703; https://doi.org/10.3390/ma3010682 - 25 Jan 2010

Cited by 51 | Viewed by 18366

Abstract

This review describes the synthesis and characterization of inorganic materials containing polyoxometalates encapsulated in oxide matrices. Examples illustrating key aspects in terms of synthesis and applications are presented according to the nature of the final hybrid material: those based on non-structured silicas, on [...] Read more.

This review describes the synthesis and characterization of inorganic materials containing polyoxometalates encapsulated in oxide matrices. Examples illustrating key aspects in terms of synthesis and applications are presented according to the nature of the final hybrid material: those based on non-structured silicas, on mesostructured silicas, on macrostructured silicas and on other oxides. In each part, key points of the synthetic protocols are highlighted and structural features and properties of the resultant hybrid nanocomposites are discussed. Full article

(This article belongs to the Special Issue Polyoxometalate Compounds)

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37 pages, 932 KiB

Open AccessReview

Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels

by Katalin Sinkó

Institute of Chemistry, University of Loránd Eötvös, Budapest, H-1117, Hungary

Materials 2010, 3(1), 704-740; https://doi.org/10.3390/ma3010704 - 26 Jan 2010

Cited by 142 | Viewed by 22206

Abstract

Silica or various silicate aerogels can be characterized by highly porous, open cell, low density structures. The synthesis parameters influence the three-dimensional porous structures by modifying the kinetics and mechanism of hydrolysis and condensation processes. Numerous investigations have shown that the structure of [...] Read more.

Silica or various silicate aerogels can be characterized by highly porous, open cell, low density structures. The synthesis parameters influence the three-dimensional porous structures by modifying the kinetics and mechanism of hydrolysis and condensation processes. Numerous investigations have shown that the structure of porous materials can be tailored by variations in synthesis conditions (e.g., the type of precursors, catalyst, and surfactants; the ratio of water/precursor; the concentrations; the medium pH; and the solvent). The objectives of this review are to summarize and elucidate the effects of chemical conditions on the nanoporous structure of sol-gel derived silicate aerogels. Full article

(This article belongs to the Special Issue Porous Materials)

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Materials, Volume 3, Issue 1 (January 2010) – 40 articles , Pages 1-754

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