Materials

13 pages, 1534 KiB

Open AccessArticle

Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings

by Myung-Joo Kim^†, Yun-Jung Choi^†, Seong-Kyun Kim, Seong-Joo Heo and Jai-Young Koak^*

¹ Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, 101 Daehak-Ro Jongno-Gu, Seoul 03080, Korea

^† These authors contributed equally to this work.

Materials 2017, 10(1), 93; https://doi.org/10.3390/ma10010093 - 23 Jan 2017

Cited by 45 | Viewed by 7343

Abstract

Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal [...] Read more.

Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture) milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance), a Scheffe’s test, and Pearson’s correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps (p < 0.05). The CAD/CAM milled group revealed a significantly high axial internal gap. There are moderate correlations between the vertical marginal discrepancy and the internal gap variables (r = 0.654), except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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22 pages, 5743 KiB

Open AccessFeature PaperArticle

First-Row Transition Metal Doping in Calcium Phosphate Bioceramics: A Detailed Crystallographic Study

by Guillaume Renaudin^*, Sandrine Gomes and Jean-Marie Nedelec

Université Clermont Auvergne, CNRS, SIGMA Clermont, Institut de Chimie de Clermont-Ferrand, F-63000 Clermont–Ferrand, France

Materials 2017, 10(1), 92; https://doi.org/10.3390/ma10010092 - 23 Jan 2017

Cited by 70 | Viewed by 8380

Abstract

Doped calcium phosphate bioceramics are promising materials for bone repair surgery because of their chemical resemblance to the mineral constituent of bone. Among these materials, BCP samples composed of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) and β-TCP (Ca₃ [...] Read more.

Doped calcium phosphate bioceramics are promising materials for bone repair surgery because of their chemical resemblance to the mineral constituent of bone. Among these materials, BCP samples composed of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) and β-TCP (Ca₃(PO₄)₂) present a mineral analogy with the nano-multi-substituted hydroxyapatite bio-mineral part of bones. At the same time, doping can be used to tune the biological properties of these ceramics. This paper presents a general overview of the doping mechanisms of BCP samples using cations from the first-row transition metals (from manganese to zinc), with respect to the applied sintering temperature. The results enable the preparation of doped synthetic BCP that can be used to tailor biological properties, in particular by tuning the release amounts upon interaction with biological fluids. Intermediate sintering temperatures stabilize the doping elements in the more soluble β-TCP phase, which favors quick and easy release upon integration in the biological environment, whereas higher sintering temperatures locate the doping elements in the weakly soluble HAp phase, enabling a slow and continuous supply of the bio-inspired properties. An interstitial doping mechanism in the HAp hexagonal channel is observed for the six investigated cations (Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with specific characteristics involving a shift away from the center of the hexagonal channel (Fe³⁺, Co²⁺), cationic oxidation (Mn³⁺, Co³⁺), and also cationic reduction (Cu⁺). The complete crystallochemical study highlights a complex HAp doping mechanism, mainly realized by an interstitial process combined with calcium substitution for the larger cations of the series leading to potentially calcium deficient HAp. Full article

(This article belongs to the Special Issue Calcium Phosphate in Biomedical Applications)

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18 pages, 41321 KiB

Open AccessArticle

Idealized vs. Realistic Microstructures: An Atomistic Simulation Case Study on γ/γ^′ Microstructures

by Aruna Prakash^*

and Erik Bitzek

Materials Science and Engineering, Institute I (MSE I), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Martensstrasse 5, Erlangen 91058, Germany

Materials 2017, 10(1), 88; https://doi.org/10.3390/ma10010088 - 23 Jan 2017

Cited by 15 | Viewed by 8839

Abstract

Single-crystal Ni-base superalloys, consisting of a two-phase γ/

γ^{'}

microstructure, retain high strengths at elevated temperatures and are key materials for high temperature applications, like, e.g., turbine blades of aircraft engines. The lattice misfit between the γ and

γ^{'}

phases [...] Read more.

Single-crystal Ni-base superalloys, consisting of a two-phase γ/

γ^{'}

microstructure, retain high strengths at elevated temperatures and are key materials for high temperature applications, like, e.g., turbine blades of aircraft engines. The lattice misfit between the γ and

γ^{'}

phases results in internal stresses, which significantly influence the deformation and creep behavior of the material. Large-scale atomistic simulations that are often used to enhance our understanding of the deformation mechanisms in such materials must accurately account for such misfit stresses. In this work, we compare the internal stresses in both idealized and experimentally-informed, i.e., more realistic, γ/

γ^{'}

microstructures. The idealized samples are generated by assuming, as is frequently done, a periodic arrangement of cube-shaped

γ^{'}

particles with planar γ/

γ^{'}

interfaces. The experimentally-informed samples are generated from two different sources to produce three different samples—the scanning electron microscopy micrograph-informed quasi-2D atomistic sample and atom probe tomography-informed stoichiometric and non-stoichiometric atomistic samples. Additionally, we compare the stress state of an idealized embedded cube microstructure with finite element simulations incorporating 3D periodic boundary conditions. Subsequently, we study the influence of the resulting stress state on the evolution of dislocation loops in the different samples. The results show that the stresses in the atomistic and finite element simulations are almost identical. Furthermore, quasi-2D boundary conditions lead to a significantly different stress state and, consequently, different evolution of the dislocation loop, when compared to samples with fully 3D boundary conditions. Full article

(This article belongs to the Section Advanced Materials Characterization)

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10 pages, 5908 KiB

Open AccessArticle

Self-Healing Materials for Ecotribology

by Shih-Chen Shi^*

and Teng-Feng Huang

Department of Mechanical Engineering, National Cheng Kung University (NCKU), No. 1 University Road, Tainan 70101, Taiwan

Materials 2017, 10(1), 91; https://doi.org/10.3390/ma10010091 - 22 Jan 2017

Cited by 25 | Viewed by 6215

Abstract

Hydroxypropyl methylcellulose (HPMC) is a biopolymer that is biodegradable, environmentally friendly, and bio-friendly. Owing to its unique chemical structure, HPMC can reduce the coefficient of friction (COF) and frictional wear and thus possesses excellent lubrication properties. HPMC has good dissolvability in specific solvents. [...] Read more.

Hydroxypropyl methylcellulose (HPMC) is a biopolymer that is biodegradable, environmentally friendly, and bio-friendly. Owing to its unique chemical structure, HPMC can reduce the coefficient of friction (COF) and frictional wear and thus possesses excellent lubrication properties. HPMC has good dissolvability in specific solvents. The present research focuses on the reversible dissolution reaction subsequent to the film formation of HPMC, with a view to the healing and lubrication properties of thin films. Raman spectroscopy was used to test the film-forming properties of HPMC and the dissolution characteristics of various solvents. In this study, the solvents were water, methanol, ethanol, and acetone. The results showed that the HPMC film had the highest dissolvability in water. The ball-on-disk wear test was used to analyze the lubrication properties of HPMC, and the results showed that HPMC had the same COF and lubrication properties as the original film after being subjected to the water healing treatment. The HPMC film can be reused, recycled, and refilled, making it an ideal lubricant for next-generation ecotribology. Full article

(This article belongs to the Special Issue Selected Material Related Papers from ICI2016)

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13 pages, 8299 KiB

Open AccessArticle

Experimental Study on Influence of Trap Parameters on Dielectric Characteristics of Nano-Modified Insulation Pressboard

by Qingguo Chen, Heqian Liu^*, Minghe Chi, Yonghong Wang and Xinlao Wei

Key Laboratory of Engineering Dielectric and its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150040, China

Materials 2017, 10(1), 90; https://doi.org/10.3390/ma10010090 - 22 Jan 2017

Cited by 21 | Viewed by 5345

Abstract

In order to study the influence of trap parameters on dielectric characteristics of nano-modified pressboards, pressboards were made using the nano doping method with different nanoparticle components. The dielectric characteristics of the modified pressboards were measured, and the trap parameters were investigated using [...] Read more.

In order to study the influence of trap parameters on dielectric characteristics of nano-modified pressboards, pressboards were made using the nano doping method with different nanoparticle components. The dielectric characteristics of the modified pressboards were measured, and the trap parameters were investigated using the thermally stimulated current (TSC) method. The test results indicated that the conductivity initially declined and then rose with the increase of nano-Al₂O₃ content, whereas it solely rose with the increase of nano-SiC content. Moreover, the conductivity exhibited nonlinear characteristics with the enhancement of electric field stress at high nanoparticle content. The relative permittivity of modified pressboard declines initially and then rises with the increase of nanoparticle content. In addition, the breakdown strength of modified pressboards exhibited a pattern of incline followed by decline with the increase of nano-Al₂O₃ content, while it always declined with the increase of nano-SiC content. The analysis based on the energy band theory on trap parameters of the constructed multi-core model concludes that the nanoparticle components added in pressboard altered both the depth and density of traps. It is therefore concluded that trap parameters have significant influence on the dielectric characteristics of nano-modified insulation pressboard. Full article

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17 pages, 6256 KiB

Open AccessArticle

Combining Bioactive Multifunctional Dental Composite with PAMAM for Root Dentin Remineralization

by Shimeng Xiao^1,2, Kunneng Liang^1,2, Michael D. Weir², Lei Cheng^1,2

, Huaibing Liu³, Xuedong Zhou¹, Yi Ding^1,* and Hockin H. K. Xu^2,4,5,*

¹ State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China

² Biomaterials and Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, University of Maryland School of Dentistry, Baltimore, MD 21201, USA

³ L.D. Caulk Division, Dentsply Sirona Restorative, Milford, DE 19963, USA

⁴ Center for Stem Cell Biology & Regenerative Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA

⁵ Department of Mechanical Engineering, University of Maryland, Baltimore County, MD 21250, USA

Materials 2017, 10(1), 89; https://doi.org/10.3390/ma10010089 - 22 Jan 2017

Cited by 24 | Viewed by 6434

Abstract

Objectives. The objectives of this study were to: (1) develop a bioactive multifunctional composite (BMC) via nanoparticles of amorphous calcium phosphate (NACP), 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of silver (NAg); and (2) investigate the effects of combined BMC + [...] Read more.

Objectives. The objectives of this study were to: (1) develop a bioactive multifunctional composite (BMC) via nanoparticles of amorphous calcium phosphate (NACP), 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of silver (NAg); and (2) investigate the effects of combined BMC + poly (amido amine) (PAMAM) on remineralization of demineralized root dentin in a cyclic artificial saliva/lactic acid environment for the first time. Methods. Root dentin specimens were prepared and demineralized with 37% phosphoric acid for 15 s. Four groups were prepared: (1) root dentin control; (2) root dentin with BMC; (3) root dentin with PAMAM; (4) root dentin with BMC + PAMAM. Specimens were treated with a cyclic artificial saliva/lactic acid regimen for 21 days. Calcium (Ca) and phosphate (P) ion concentrations and acid neutralization were determined. The remineralized root dentin specimens were examined via hardness testing and scanning electron microscopy (SEM). Results. Mechanical properties of BMC were similar to commercial control composites (p = 0.913). BMC had excellent Ca and P ion release and acid-neutralization capability. BMC or PAMAM alone each achieved slight mineral regeneration in demineralized root dentin. The combined BMC + PAMAM induced the greatest root dentin remineralization, and increased the hardness of pre-demineralized root dentin to match that of healthy root dentin (p = 0.521). Significance. The excellent root dentin remineralization effects of BMC + PAMAM were demonstrated for the first time. BMC + PAMAM induced effective and complete root dentin remineralization in an acid challenge environment. The novel BMC + PAMAM method is promising for Class V and other restorations to remineralize and protect tooth structures. Full article

(This article belongs to the Section Biomaterials)

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8 pages, 4040 KiB

Open AccessArticle

Microstructure Evolution in High Purity Aluminum Single Crystal Processed by Equal Channel Angular Pressing (ECAP)

by Jinfang Dong, Qing Dong, Yongbing Dai, Hui Xing^*, Yanfeng Han, Jianbo Ma, Jiao Zhang^*, Jun Wang and Baode Sun

Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, China

Materials 2017, 10(1), 87; https://doi.org/10.3390/ma10010087 - 22 Jan 2017

Cited by 8 | Viewed by 5008

Abstract

Aluminum single crystal with 99.999% purity was deformed at room temperature by equal channel angular pressing (ECAP) up to 16 passes. Grain size and misorientation of processed samples were quantitatively characterized by TEM and EBSD. The results show that the refinement efficiency of [...] Read more.

Aluminum single crystal with 99.999% purity was deformed at room temperature by equal channel angular pressing (ECAP) up to 16 passes. Grain size and misorientation of processed samples were quantitatively characterized by TEM and EBSD. The results show that the refinement efficiency of high purity aluminum single crystal was poor in the initial stage. Extrusion by fewer ECAP passes (n ≤ 8) resulted in only elongated grains containing a large number of subgrains and small misorientations between grains. Stable microstructures of nearly equiaxed grains with high misorientations were obtained by 15 passages, indicating that the initial extremely coarse grains and highly uniform grain orientation are not conducive to the accumulation of strain energy. The initial state of high purity aluminum has a significant effect on the refining efficiency of the ECAP process. Full article

(This article belongs to the Section Advanced Materials Characterization)

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15 pages, 9957 KiB

Open AccessArticle

Synthesis of Graphene Based Membranes: Effect of Substrate Surface Properties on Monolayer Graphene Transfer

by Feras Kafiah¹, Zafarullah Khan^1,*, Ahmed Ibrahim^1,2, Muataz Atieh³ and Tahar Laoui^1,*

¹ Department of Mechanical Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia

² Department of Mechanical Design and Production Engineering, Zagazig University, Zagazig 44519, Egypt

³ Qatar Environment and Energy Research Institute, HBKU, Qatar Foundation, P.O. Box 5825, Doha, Qatar

Materials 2017, 10(1), 86; https://doi.org/10.3390/ma10010086 - 21 Jan 2017

Cited by 14 | Viewed by 10098

Abstract

In this work, we report the transfer of graphene onto eight commercial microfiltration substrates having different pore sizes and surface characteristics. Monolayer graphene grown on copper by the chemical vapor deposition (CVD) process was transferred by the pressing method over the target substrates, [...] Read more.

In this work, we report the transfer of graphene onto eight commercial microfiltration substrates having different pore sizes and surface characteristics. Monolayer graphene grown on copper by the chemical vapor deposition (CVD) process was transferred by the pressing method over the target substrates, followed by wet etching of copper to obtain monolayer graphene/polymer membranes. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) measurements were carried out to explore the graphene layer transferability. Three factors, namely, the substrate roughness, its pore size, and its surface wetting (degree of hydrophobicity) are found to affect the conformality and coverage of the transferred graphene monolayer on the substrate surface. A good quality graphene transfer is achieved on the substrate with the following characteristics; being hydrophobic (CA > 90°), having small pore size, and low surface roughness, with a CA to RMS (root mean square) ratio higher than 2.7°/nm. Full article

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21 pages, 604 KiB

Open AccessArticle

An Extended Damage Plasticity Model for Shotcrete: Formulation and Comparison with Other Shotcrete Models

by Matthias Neuner^*

, Peter Gamnitzer and Günter Hofstetter

Unit for Strength of Materials and Structural Analysis, Institute of Basic Sciences in Engineering Science, Innsbruck University, Technikerstr. 13, A-6020 Innsbruck, Austria

Materials 2017, 10(1), 82; https://doi.org/10.3390/ma10010082 - 21 Jan 2017

Cited by 27 | Viewed by 6866 | Correction

Abstract

The aims of the present paper are (i) to briefly review single-field and multi-field shotcrete models proposed in the literature; (ii) to propose the extension of a damage-plasticity model for concrete to shotcrete; and (iii) to evaluate the capabilities of the proposed extended [...] Read more.

The aims of the present paper are (i) to briefly review single-field and multi-field shotcrete models proposed in the literature; (ii) to propose the extension of a damage-plasticity model for concrete to shotcrete; and (iii) to evaluate the capabilities of the proposed extended damage-plasticity model for shotcrete by comparing the predicted response with experimental data for shotcrete and with the response predicted by shotcrete models, available in the literature. The results of the evaluation will be used for recommendations concerning the application and further improvements of the investigated shotcrete models and they will serve as a basis for the design of a new lab test program, complementing the existing ones. Full article

(This article belongs to the Special Issue Numerical Analysis of Concrete using Discrete Elements)

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25 pages, 7531 KiB

Open AccessArticle

On the Injection Molding Processing Parameters of HDPE-TiO₂ Nanocomposites

by Abdel-Hamid I. Mourad¹

, Mohammad Sayem Mozumder^2,*, Anusha Mairpady², Hifsa Pervez²

and Uma Maheshwara Kannuri²

¹ Mechanical Engineering Department, College of Engineering, UAE University, Al Ain 15551, UAE

² Chemical & Petroleum Engineering Department, College of Engineering, UAE University, Al Ain 15551, UAE

Materials 2017, 10(1), 85; https://doi.org/10.3390/ma10010085 - 20 Jan 2017

Cited by 43 | Viewed by 7978

Abstract

In recent years, the development and use of polymeric nanocomposites in creating advanced materials has expanded exponentially. A substantial amount of research has been done in order to design polymeric nanocomposites in a safe and efficient manner. In the present study, the impact [...] Read more.

In recent years, the development and use of polymeric nanocomposites in creating advanced materials has expanded exponentially. A substantial amount of research has been done in order to design polymeric nanocomposites in a safe and efficient manner. In the present study, the impact of processing parameters, such as, barrel temperature, and residence time on the mechanical and thermal properties of high density polyethylene (HDPE)-TiO₂ nanocomposites were investigated. Additionally, scanning electron microscopy and X-ray diffraction spectroscopy were used to analyze the dispersion, location, and phase morphology of TiO₂ on the HDPE matrix. Mechanical tests revealed that tensile strength of the fabricated HDPE-TiO₂ nanocomposites ranged between 22.53 and 26.30 MPa, while the Young’s modulus showed a consistent increase as the barrel temperature increased from 150 °C to 300 °C. Moreover, the thermal stability decreased as the barrel temperature increased. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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14 pages, 4762 KiB

Open AccessArticle

Synthesis of Magnetic Microspheres with Sodium Alginate and Activated Carbon for Removal of Methylene Blue

by Chaodao Li^1,2, Jianjiang Lu^1,2,*, Shanman Li^1,2, Yanbin Tong^1,2 and Bangce Ye^1,2

¹ School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003, China

² Key Laboratory for Green Processing of Chemical Engineering of Xinjiang Bingtuan, Shihezi 832003, China

Materials 2017, 10(1), 84; https://doi.org/10.3390/ma10010084 - 20 Jan 2017

Cited by 66 | Viewed by 9663

Abstract

Based on the adsorption performance of composite microspheres with activated carbon (AC) and sodium alginate (SA), as well as the magnetic property of Fe₃O₄, we designed and explored an efficient strategy to prepare a unique, multifunctional Fe₃O [...] Read more.

Based on the adsorption performance of composite microspheres with activated carbon (AC) and sodium alginate (SA), as well as the magnetic property of Fe₃O₄, we designed and explored an efficient strategy to prepare a unique, multifunctional Fe₃O₄/AC/SA composite absorbent (MSA-AC) that extracted dye from aqueous solution. The composite exhibited the following advantages: rapid and simple to prepare, environmentally friendly process, low-cost, recyclability, and multi-functionality. The physicochemical properties of the prepared magnetic microspheres were measured, and methylene blue (MB) was selected to investigate the performance of the magnetic absorbent. The results showed a maximum adsorption capacity of 222.3 mg/g for MB. Adsorption studies revealed that the data of adsorption isotherms and kinetics fit the pseudo-second-order kinetic model and Langmuir isotherm model. Full article

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14 pages, 6716 KiB

Open AccessFeature PaperArticle

Bioactive Glass Fiber-Reinforced PGS Matrix Composites for Cartilage Regeneration

by Marina Trevelin Souza^1,*, Samira Tansaz²

, Edgar Dutra Zanotto¹

and Aldo R. Boccaccini²

¹ CeRTEV—Center for Research, Technology and Education in Vitreous Materials, Vitreous Material Laboratory, Department of Materials Engineering, Universidade Federal de São Carlos—UFSCar, 13565905 São Carlos, SP, Brazil

² Institute of Biomaterials, University of Erlangen-Nuremberg, 91058 Erlangen, Germany

Materials 2017, 10(1), 83; https://doi.org/10.3390/ma10010083 - 20 Jan 2017

Cited by 44 | Viewed by 7896

Abstract

Poly(glycerol sebacate) (PGS) is an elastomeric polymer which is attracting increasing interest for biomedical applications, including cartilage regeneration. However, its limited mechanical properties and possible negative effects of its degradation byproducts restrict PGS for in vivo application. In this study, a novel PGS–bioactive [...] Read more.

Poly(glycerol sebacate) (PGS) is an elastomeric polymer which is attracting increasing interest for biomedical applications, including cartilage regeneration. However, its limited mechanical properties and possible negative effects of its degradation byproducts restrict PGS for in vivo application. In this study, a novel PGS–bioactive glass fiber (F18)-reinforced composite was developed and characterized. PGS-based reinforced scaffolds were fabricated via salt leaching and characterized regarding their mechanical properties, degradation, and bioactivity in contact with simulated body fluid. Results indicated that the incorporation of silicate-based bioactive glass fibers could double the composite tensile strength, tailor the polymer degradability, and improve the scaffold bioactivity. Full article

(This article belongs to the Special Issue Bioceramics 2016)

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9 pages, 3497 KiB

Open AccessArticle

Metal-Organic Framework of Lanthanoid Dinuclear Clusters Undergoes Slow Magnetic Relaxation

by Hikaru Iwami¹, Ryo Nakanishi^1,*, Yoji Horii¹, Keiichi Katoh¹

, Brian K. Breedlove¹ and Masahiro Yamashita^1,2,*

¹ Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan

² WPI Research Center, Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

Materials 2017, 10(1), 81; https://doi.org/10.3390/ma10010081 - 20 Jan 2017

Cited by 2 | Viewed by 7611

Abstract

Lanthanoid metal-organic frameworks (Ln-MOFs) can adopt a variety of new structures due to the large coordination numbers of Ln metal ions, and Ln-MOFs are expected to show new luminescence and magnetic properties due to the localized f electrons. In particular, some Ln metal [...] Read more.

Lanthanoid metal-organic frameworks (Ln-MOFs) can adopt a variety of new structures due to the large coordination numbers of Ln metal ions, and Ln-MOFs are expected to show new luminescence and magnetic properties due to the localized f electrons. In particular, some Ln metal ions, such as Dy(III) and Tb(III) ions, work as isolated quantum magnets when they have magnetic anisotropy. In this work, using 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic acid (H₃TATB) as a ligand, two new Ln-MOFs, [Dy(TATB)(DMF)₂] (1) and [Tb(TATB)(DMF)₂] (2), were obtained. The Ln-MOFs contain Ln dinuclear clusters as secondary building units, and 1 underwent slow magnetic relaxation similar to single-molecule magnets. Full article

(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)

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13 pages, 3681 KiB

Open AccessArticle

Cellulose Nanocrystals (CNCs) from Corn Stalk: Activation Energy Analysis

by Siwei Huang¹, Ling Zhou², Mei-Chun Li³, Qinglin Wu^3,* and Dingguo Zhou^1,*

¹ College of Materials Science and Engineering, Nanjing Forestry University, Long Pan Road, Nanjing 210037, China

² School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China

³ School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA

Materials 2017, 10(1), 80; https://doi.org/10.3390/ma10010080 - 20 Jan 2017

Cited by 87 | Viewed by 10102

Abstract

Cellulose nanocrystals (CNCs) were isolated from corn stalk using sulfuric acid hydrolysis, and their morphology, chemical structure, and thermal stability properties were characterized. The CNCs had an average length of 120.2 ± 61.3 nm and diameter of 6.4 ± 3.1 nm (L/D = [...] Read more.

Cellulose nanocrystals (CNCs) were isolated from corn stalk using sulfuric acid hydrolysis, and their morphology, chemical structure, and thermal stability properties were characterized. The CNCs had an average length of 120.2 ± 61.3 nm and diameter of 6.4 ± 3.1 nm (L/D = 18.7). The degree of crystallinity of the CNCs increased to 69.20% from the 33.20% crystallinity of raw corn stalk fiber, while the chemical structure was well kept after sulfuric acid hydrolysis. Thermal stability analysis showed that the degradation temperature of the CNCs reached 239.5 °C, which was higher than that of the raw fiber but lower than that of the extracted cellulose. The average activation energy values for the CNCs, evaluated using the Friedman, Flynn-Wall-Ozawa (F-W-O) and Coats-Redfern methods, were 312.6, 302.8, and 309 kJ·mol⁻¹ in the conversion range of 0.1 to 0.8. The isolated CNCs had higher values of activation energy than did the purified cellulose, which was attributed to the stronger hydrogen bonds present in the crystalline domains of CNCs than in those of cellulose. These findings can help better understand the thermal properties of polymer/CNC composites. Full article

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11 pages, 5709 KiB

Open AccessArticle

Methodology for Fast and Facile Characterisation of Carbon-Based Electrodes Focused on Bioelectrochemical Systems Development and Scale Up

by Raúl Mateos¹

, Raúl M. Alonso¹, Adrián Escapa^1,2,* and Antonio Morán¹

¹ Chemical and Environmental Bioprocess Engineering Group, Natural Resources Institute (IRENA), Universidad de León, Av. de Portugal 41, 24009 León, Spain

² Department of Electrical Engineering and Automatic Systems, Universidad de León, Campus de Vegazana s/n, 24071 León, Spain

Materials 2017, 10(1), 79; https://doi.org/10.3390/ma10010079 - 20 Jan 2017

Cited by 15 | Viewed by 5158

Abstract

The development and practical implementation of bioelectrochemical systems (BES) requires an in-depth characterisation of their components. The electrodes, which are critical elements, are usually built from carbon-based materials due to their high specific surface area, biocompatibility and chemical stability. In this study, a [...] Read more.

The development and practical implementation of bioelectrochemical systems (BES) requires an in-depth characterisation of their components. The electrodes, which are critical elements, are usually built from carbon-based materials due to their high specific surface area, biocompatibility and chemical stability. In this study, a simple methodology to electrochemically characterise carbon-based electrodes has been developed, derived from conventional electrochemical analyses. Combined with classical electrochemical theory and the more innovative fractal geometry approach, our method is aimed at comparing and characterising the performance of carbon electrodes through the determination of the electroactive surface and its fractal dimension. Overall, this methodology provides a quick and easy method for the screening of suitable electrode materials to be implemented in BES. Full article

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15 pages, 10949 KiB

Open AccessArticle

Investigation of γ-(2,3-Epoxypropoxy)propyltrimethoxy Silane Surface Modified Layered Double Hydroxides Improving UV Ageing Resistance of Asphalt

by Canlin Zhang¹, Jianying Yu^1,*, Lihui Xue^2,* and Yubin Sun²

¹ State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China

² Centrer for Materials Research and Analysis, Wuhan University of Technology, Wuhan 430070, China

Materials 2017, 10(1), 78; https://doi.org/10.3390/ma10010078 - 19 Jan 2017

Cited by 46 | Viewed by 7054

Abstract

γ-(2,3-Epoxypropoxy)propyltrimethoxy silane surface modified layered double hydroxides (KH560-LDHs) were prepared and used to improve the ultraviolet ageing resistance of asphalt. The results of X-ray photoelectron spectrometry (XPS) indicated that KH560 has been successfully grafted onto the surface of LDHs. The agglomeration of LDHs [...] Read more.

γ-(2,3-Epoxypropoxy)propyltrimethoxy silane surface modified layered double hydroxides (KH560-LDHs) were prepared and used to improve the ultraviolet ageing resistance of asphalt. The results of X-ray photoelectron spectrometry (XPS) indicated that KH560 has been successfully grafted onto the surface of LDHs. The agglomeration of LDHs particles notably reduced after KH560 surface modification according to scanning electron microscopy (SEM), which implied that the KH560 surface modification was helpful to promote the dispersibility of LDHs in asphalt. Then, the influence of KH560-LDHs and LDHs on the physical and rheological properties of asphalt before and after UV ageing was thoroughly investigated. The storage stability test showed that the difference in softening point (ΔS) of LDHs modified asphalt decreased from 0.6 °C to 0.2 °C at an LDHs content of 1% after KH560 surface modification, and the tendency became more pronounced with the increase of LDH content, indicating that KH560 surface modification could improve the stability of LDHs in asphalt. After UV ageing, the viscous modulus (G’’) of asphalt significantly reduced, and correspondingly, the elastic modulus (G’) and rutting factor (G*/sin δ) rapidly increased. Moreover, the asphaltene increased and the amount of “bee-like” structures of the asphalt decreased. Compared with LDHs, KH560-LDHs obviously restrained performance deterioration of the asphalt, and helped to relieve the variation of the chemical compositions and morphology of asphalt, which suggested that the improvement of KH560-LDHs on UV ageing resistance of asphalt was superior to LDHs. Full article

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1 pages, 144 KiB

Open AccessErratum

Erratum: Myoung, S.C.; Su-Tae, K.; Bang, Y.L.; Kyeong-Taek, K.; Gum-Sung, R. Improvement in Predicting the Post-Cracking Tensile Behavior of Ultra-High Performance Cementitious Composites Based on Fiber Orientation Distribution. Materials 2016, 9, 829

by Myoung Sung Choi¹, Su-Tae Kang^2,*

, Bang Yeon Lee³

, Kyeong-Taek Koh⁴ and Gum-Sung Ryu⁴

¹ Department of Safety Engineering, Dongguk University-Gyeongju, 123 Dongdae-ro, Gyeongju, Gyeongbuk 38066, Korea

² Department of Civil Engineering, Daegu University, 201 Daegudae-ro, Jillyang, Gyeongsan, Gyeongbuk 38453, Korea

³ School of Architecture, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Korea

⁴ Structural Engineering Research Institute, Korea Institute of Civil Engineering and Building Technology, 283 Goyangdae-Ro, Ilsanseo-Gu, Goyang, Gyeonggi 10223, Korea

Materials 2017, 10(1), 63; https://doi.org/10.3390/ma10010063 - 19 Jan 2017

Cited by 2 | Viewed by 3475

Abstract

1.The authors wish to remove the symbol “†”, which indicates the equal contribution from each author. The correct authorship is shown below:[...] Full article

9 pages, 3652 KiB

Open AccessArticle

Facile Synthesis of V₂O₅ Hollow Spheres as Advanced Cathodes for High-Performance Lithium-Ion Batteries

by Xingyuan Zhang¹, Jian-Gan Wang^1,*

, Huanyan Liu¹, Hongzhen Liu¹ and Bingqing Wei^1,2,*

¹ State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, School of Materials Science and Engineering, Northwestern Polytechnical University and Shaanxi Joint Lab of Graphene (NPU), Xi’an 710072, China

² Department of Mechanical Engineering, University of Delaware, Newark, DE 19716, USA

Materials 2017, 10(1), 77; https://doi.org/10.3390/ma10010077 - 18 Jan 2017

Cited by 35 | Viewed by 10031

Abstract

Three-dimensional V₂O₅ hollow structures have been prepared through a simple synthesis strategy combining solvothermal treatment and a subsequent thermal annealing. The V₂O₅ materials are composed of microspheres 2–3 μm in diameter and with a distinct hollow interior. [...] Read more.

Three-dimensional V₂O₅ hollow structures have been prepared through a simple synthesis strategy combining solvothermal treatment and a subsequent thermal annealing. The V₂O₅ materials are composed of microspheres 2–3 μm in diameter and with a distinct hollow interior. The as-synthesized V₂O₅ hollow microspheres, when evaluated as a cathode material for lithium-ion batteries, can deliver a specific capacity as high as 273 mAh·g⁻¹ at 0.2 C. Benefiting from the hollow structures that afford fast electrolyte transport and volume accommodation, the V₂O₅ cathode also exhibits a superior rate capability and excellent cycling stability. The good Li-ion storage performance demonstrates the great potential of this unique V₂O₅ hollow material as a high-performance cathode for lithium-ion batteries. Full article

(This article belongs to the Special Issue Materials for Electrochemical Capacitors and Batteries)

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23 pages, 41922 KiB

Open AccessFeature PaperReview

On the Selective Laser Melting (SLM) of the AlSi10Mg Alloy: Process, Microstructure, and Mechanical Properties

by Francesco Trevisan^1,2, Flaviana Calignano², Massimo Lorusso², Jukka Pakkanen^1,2

, Alberta Aversa¹

, Elisa Paola Ambrosio², Mariangela Lombardi¹

, Paolo Fino^1,2

and Diego Manfredi^2,*

¹ DISAT, Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

² Centre for Sustainable Future Technologies @PoliTo, Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Torino, Italy

Materials 2017, 10(1), 76; https://doi.org/10.3390/ma10010076 - 18 Jan 2017

Cited by 404 | Viewed by 33909

Abstract

The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM) technique known as Selective Laser Melting [...] Read more.

The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM) technique known as Selective Laser Melting (SLM). This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented. Full article

(This article belongs to the Special Issue Metals for Additive Manufacturing)

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16 pages, 4790 KiB

Open AccessArticle

XPS Study on the Stability and Transformation of Hydrate and Carbonate Phases within MgO Systems

by Vanessa Rheinheimer^1,*, Cise Unluer², Jiawei Liu², Shaoqin Ruan², Jisheng Pan³ and Paulo J. M. Monteiro⁴

¹ Berkeley Education Alliance for Research in Singapore, Singapore 138602, Singapore

² Department of Civil and Environmental Engineering, Nanyang Technical University, Singapore 639798, Singapore

³ Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634, Singapore

⁴ Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley 94720, CA, USA

Materials 2017, 10(1), 75; https://doi.org/10.3390/ma10010075 - 18 Jan 2017

Cited by 72 | Viewed by 10596

Abstract

MgO cements have great potential for carbon sequestration as they have the ability to carbonate and gain strength over time. The hydration of reactive MgO occurs at a similar rate as ordinary Portland cement (PC) and forms brucite (Mg(OH)₂, magnesium hydroxide), [...] Read more.

MgO cements have great potential for carbon sequestration as they have the ability to carbonate and gain strength over time. The hydration of reactive MgO occurs at a similar rate as ordinary Portland cement (PC) and forms brucite (Mg(OH)₂, magnesium hydroxide), which reacts with CO₂ to form a range of hydrated magnesium carbonates (HMCs). However, the formation of HMCs within the MgO–CO₂–H₂O system depends on many factors, such as the temperature and CO₂ concentration, among others, which play an important role in determining the rate and degree of carbonation, the type and stability of the produced HMCs and the associated strength development. It is critical to understand the stability and transformation pathway of HMCs, which are assessed here through the use of X-ray photoelectron spectroscopy (XPS). The effects of the CO₂ concentration (in air or 10% CO₂), exposure to high temperatures (up to 300 °C) and curing period (one or seven days) are reported. Observed changes in the binding energy (BE) indicate the formation of different components and the transformation of the hydrated carbonates from one form to another, which will influence the final performance of the carbonated blends. Full article

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16 pages, 9852 KiB

Open AccessArticle

Supercritical CO₂-Assisted Spray Drying of Strawberry-Like Gold-Coated Magnetite Nanocomposites in Chitosan Powders for Inhalation

by Marta C. Silva^1,2, Ana Sofia Silva^1,3

, Javier Fernandez-Lodeiro^2,4

, Teresa Casimiro¹

, Carlos Lodeiro^2,4,*

and Ana Aguiar-Ricardo^1,*

¹ LAQV-REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, Caparica 2829-516, Portugal

² BIOSCOPE Research Group, UCIBIO@REQUIMTE, Chemistry Department, Faculty of Science and Technology, University NOVA of Lisbon, Caparica Campus, Caparica 2829-516, Portugal

³ CICS-UBI, Health Sciences Research Center, Faculdade de Ciências da Saúde, Universidade da Beira Interior, Av. Infante D. Henrique, Covilhã 6200-506, Portugal

⁴ PROTEOMASS Scientific Society, Rua dos Inventores, Madam Parque, Caparica Campus, Caparica 2829-516, Portugal

Materials 2017, 10(1), 74; https://doi.org/10.3390/ma10010074 - 18 Jan 2017

Cited by 30 | Viewed by 7117

Abstract

Lung cancer is one of the leading causes of death worldwide. Therefore, it is of extreme importance to develop new systems that can deliver anticancer drugs into the site of action when initiating a treatment. Recently, the use of nanotechnology and particle engineering [...] Read more.

Lung cancer is one of the leading causes of death worldwide. Therefore, it is of extreme importance to develop new systems that can deliver anticancer drugs into the site of action when initiating a treatment. Recently, the use of nanotechnology and particle engineering has enabled the development of new drug delivery platforms for pulmonary delivery. In this work, POXylated strawberry-like gold-coated magnetite nanocomposites and ibuprofen (IBP) were encapsulated into a chitosan matrix using Supercritical Assisted Spray Drying (SASD). The dry powder formulations showed adequate morphology and aerodynamic performances (fine particle fraction 48%–55% and aerodynamic diameter of 2.6–2.8 µm) for deep lung deposition through the pulmonary route. Moreover, the release kinetics of IBP was also investigated showing a faster release of the drug at pH 6.8, the pH of lung cancer. POXylated strawberry-like gold-coated magnetite nanocomposites proved to have suitable sizes for cellular internalization and their fluorescent capabilities enable their future use in in vitro cell based assays. As a proof-of-concept, the reported results show that these nano-in-micro formulations could be potential drug vehicles for pulmonary administration. Full article

(This article belongs to the Special Issue Selected papers from ISN2A2016)

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14 pages, 10377 KiB

Open AccessArticle

Properties of a Laser Shock Wave in Al-Cu Alloy under Elevated Temperatures: A Molecular Dynamics Simulation Study

by Xiankai Meng¹, Jianzhong Zhou^1,*, Shu Huang¹, Chun Su^1,2

and Jie Sheng¹

¹ School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China

² School of Mechanical & Vehicle Engineering, Changzhou Institute of Technology, Changzhou 213022, China

Materials 2017, 10(1), 73; https://doi.org/10.3390/ma10010073 - 18 Jan 2017

Cited by 27 | Viewed by 7418

Abstract

The laser shock wave (LSW) generated by the interaction between a laser and a material has been widely used in laser manufacturing, such as laser shock peening and laser shock forming. However, due to the high strain rate, the propagation of LSW in [...] Read more.

The laser shock wave (LSW) generated by the interaction between a laser and a material has been widely used in laser manufacturing, such as laser shock peening and laser shock forming. However, due to the high strain rate, the propagation of LSW in materials, especially LSW at elevated temperatures, is difficult to study through experimental methods. A molecular dynamics simulation was used in this study to investigate the propagation of LSW in an Al-Cu alloy. The Hugoniot relations of LSW were obtained at different temperatures and the effects of elevated temperatures on shock velocity and shock pressure were analyzed. Then the elastic and plastic wave of the LSW was researched. Finally, the evolution of dislocations induced by LSW and its mechanism under elevated temperatures was explored. The results indicate that the shock velocity and shock pressure induced by LSW both decrease with the increasing temperatures. Moreover, the velocity of elastic wave and plastic wave both decrease with the increasing treatment temperature, while their difference decreases as the temperature increases. Moreover, the dislocation atoms increases with the increasing temperatures before 2 ps, while it decreases with the increasing temperatures after 2 ps. The reason for the results is related to the formation and evolution of extended dislocations. Full article

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11 pages, 5658 KiB

Open AccessFeature PaperCommunication

Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries

by Jin Zhang, Beibei Wang, Jiachen Zhou, Ruoyu Xia, Yingli Chu and Jia Huang^*

School of Materials Science and Engineering, Tongji University, Shanghai, 201804, China

Materials 2017, 10(1), 72; https://doi.org/10.3390/ma10010072 - 17 Jan 2017

Cited by 29 | Viewed by 9032

Abstract

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH₂)₅COOH”, and the CuO nanowires (NWs) were well [...] Read more.

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH₂)₅COOH”, and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g⁻¹ after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes. Full article

(This article belongs to the Special Issue Microwave Absorbing and Energy Storage Materials)

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17 pages, 57543 KiB

Open AccessFeature PaperArticle

Inspection of Piezoceramic Transducers Used for Structural Health Monitoring

by Inka Mueller

and Claus-Peter Fritzen^*

Department of Mechanical Engineering, University of Siegen, Paul-Bonatz-Str., 9-11, 57076 Siegen, Germany

Materials 2017, 10(1), 71; https://doi.org/10.3390/ma10010071 - 16 Jan 2017

Cited by 44 | Viewed by 6712

Abstract

The use of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) purposes is state of the art for acousto-ultrasonic-based methods. For system reliability, detailed information about the PWAS itself is necessary. This paper gives an overview on frequent PWAS faults and [...] Read more.

The use of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) purposes is state of the art for acousto-ultrasonic-based methods. For system reliability, detailed information about the PWAS itself is necessary. This paper gives an overview on frequent PWAS faults and presents the effects of these faults on the wave propagation, used for active acousto-ultrasonics-based SHM. The analysis of the wave field is based on velocity measurements using a laser Doppler vibrometer (LDV). New and established methods of PWAS inspection are explained in detail, listing advantages and disadvantages. The electro-mechanical impedance spectrum as basis for these methods is discussed for different sensor faults. This way this contribution focuses on a detailed analysis of PWAS and the need of their inspection for an increased reliability of SHM systems. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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11 pages, 2345 KiB

Open AccessArticle

Conjugation Length Effect on TPA-Based Optical Limiting Performance of a Series of Ladder-Type Chromophores

by Yujin Zhang^1,†

, Wei Hu^2,†, Liyun Zhao¹

, Jiancai Leng^1,* and Hong Ma^3,*

¹ School of Science, Qilu University of Technology, Jinan 250353, China

² Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China

³ School of Physics and Electronics, Shandong Normal University, Jinan 250014, China

^† These authors contributed equally to this work.

Materials 2017, 10(1), 70; https://doi.org/10.3390/ma10010070 - 16 Jan 2017

Cited by 6 | Viewed by 5083

Abstract

Nonlinear optical properties of a series of newly-synthesized ladder-type chromophores containing oligo-p-phenylene moiety with different π-conjugated lengths were theoretically studied by numerically solving the rate equations and the field intensity equation with an iterative predictor-corrector finite-difference time-domain technique. Ab initio calculation [...] Read more.

Nonlinear optical properties of a series of newly-synthesized ladder-type chromophores containing oligo-p-phenylene moiety with different π-conjugated lengths were theoretically studied by numerically solving the rate equations and the field intensity equation with an iterative predictor-corrector finite-difference time-domain technique. Ab initio calculation results show that the compounds can be described by the three-level model. Based on the two-photon absorption mechanism, highly efficient optical limiting performances are demonstrated in the chromophores, which strongly depend on the π-conjugated length of the molecule. Special attention has been paid to the dynamical two-photon absorption, indicating that the parameter of the medium can affect the dynamical two-photon absorption cross section. Our numerical results agree well with the experimental measurements. It reveals that the increase in the π-conjugated length of ladder-type oligo-p-phenylene for these chromophores leads to enhanced nonlinear optical absorption. The results also provide a method to modulate the optical limiting and dynamical two-photon absorption of the compounds by changing the molecular density and thickness of the absorber. Full article

(This article belongs to the Special Issue Nonlinear Optical Material)

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9 pages, 4924 KiB

Open AccessArticle

Novel AlN/Pt/ZnO Electrode for High Temperature SAW Sensors

by Xingpeng Liu, Bin Peng^*, Wanli Zhang, Jun Zhu, Xingzhao Liu and Meng Wei

State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China

Materials 2017, 10(1), 69; https://doi.org/10.3390/ma10010069 - 16 Jan 2017

Cited by 19 | Viewed by 5698

Abstract

In order to develop a film electrode for the surface acoustic wave (SAW) devices working in high temperature, harsh environments, novel AlN/Pt/ZnO multilayers were prepared using pulsed laser deposition (PLD) systems on langasite (LGS) substrates. The AlN film was used as a protective [...] Read more.

In order to develop a film electrode for the surface acoustic wave (SAW) devices working in high temperature, harsh environments, novel AlN/Pt/ZnO multilayers were prepared using pulsed laser deposition (PLD) systems on langasite (LGS) substrates. The AlN film was used as a protective layer and the ZnO buffer layer was introduced to improve the crystal quality of Pt films. The results show that the resistances of Pt and AlN/Pt film electrodes violently increase above 600 °C and 800 °C, respectively, while the resistances of AlN/Pt/ZnO electrodes have more stable electrical resistance from room temperature to 1000 °C. The AlN/Pt/ZnO electrode, where the ZnO film was deposited at 600 °C, has the best temperature stability and can steadily work for 4 h at 1000 °C. The mechanism underlying the stable resistance of the AlN/Pt/ZnO electrode at a high temperature was investigated by analyzing the microstructure of the prepared samples. The proposed AlN/Pt/ZnO film electrode has great potential for applications in high temperature SAW sensors. Full article

(This article belongs to the Section Advanced Materials Characterization)

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12 pages, 2210 KiB

Open AccessArticle

Electrospun Nanofibers Made of Silver Nanoparticles, Cellulose Nanocrystals, and Polyacrylonitrile as Substrates for Surface-Enhanced Raman Scattering

by Suxia Ren¹, Lili Dong¹, Xiuqiang Zhang¹, Tingzhou Lei^1,*, Franz Ehrenhauser², Kunlin Song³, Meichun Li³, Xiuxuan Sun³ and Qinglin Wu^3,*

¹ Key Biomass Energy Laboratory of Henan Province, Zhengzhou 450008, Henan, China

² Audubon Sugar Institute, Louisiana State University Ag Center, St. Gabriel, LA 70776, USA

³ School of Renewable Natural Resources, Louisiana State University Ag Center, Baton Rouge, LA 70803, USA

Materials 2017, 10(1), 68; https://doi.org/10.3390/ma10010068 - 14 Jan 2017

Cited by 39 | Viewed by 9301

Abstract

Nanofibers with excellent activities in surface-enhanced Raman scattering (SERS) were developed through electrospinning precursor suspensions consisting of polyacrylonitrile (PAN), silver nanoparticles (AgNPs), silicon nanoparticles (SiNPs), and cellulose nanocrystals (CNCs). Rheology of the precursor suspensions, and morphology, thermal properties, chemical structures, and SERS sensitivity [...] Read more.

Nanofibers with excellent activities in surface-enhanced Raman scattering (SERS) were developed through electrospinning precursor suspensions consisting of polyacrylonitrile (PAN), silver nanoparticles (AgNPs), silicon nanoparticles (SiNPs), and cellulose nanocrystals (CNCs). Rheology of the precursor suspensions, and morphology, thermal properties, chemical structures, and SERS sensitivity of the nanofibers were investigated. The electrospun nanofibers showed uniform diameters with a smooth surface. Hydrofluoric (HF) acid treatment of the PAN/CNC/Ag composite nanofibers (defined as p-PAN/CNC/Ag) led to rougher fiber surfaces with certain pores and increased mean fiber diameters. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed the existence of AgNPs that were formed during heat and HF acid treatment processes. In addition, thermal stability of the electrospun nanofibers increased due to the incorporation of CNCs and AgNPs. The p-PAN/CNC/Ag nanofibers were used as a SERS substrate to detect p-aminothiophenol (p-ATP) probe molecule. The results show that this substrate exhibited high sensitivity for the p-ATP probe detection. Full article

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10 pages, 1232 KiB

Open AccessArticle

Bonding to Different PEEK Compositions: The Impact of Dental Light Curing Units

by Nina Lümkemann, Marlis Eichberger and Bogna Stawarczyk^*

Department of Prosthodontics, Dental School, Ludwig-Maximilians-University Munich, Goethestrasse 70, 80336 Munich, Germany

Materials 2017, 10(1), 67; https://doi.org/10.3390/ma10010067 - 14 Jan 2017

Cited by 22 | Viewed by 6356

Abstract

This study investigated the impact of different light curing units (LCUs) for the polymerization of adhesive system visio.link (VL) on the tensile bond strength (TBS) of different PEEK compositions. For TBS measurements, 216 PEEK specimens with varying amounts of TiO₂ (PEEK/0%, PEEK/20%, [...] Read more.

This study investigated the impact of different light curing units (LCUs) for the polymerization of adhesive system visio.link (VL) on the tensile bond strength (TBS) of different PEEK compositions. For TBS measurements, 216 PEEK specimens with varying amounts of TiO₂ (PEEK/0%, PEEK/20%, PEEK/>30%) were embedded, polished, air abraded (Al₂O₃, 50 µm, 0.4 MPa), conditioned using VL, and polymerized using either a halogen LCU (HAL-LCU) or a LED LCU (LED-LCU) for chairside or labside application, respectively. After thermocycling (5000×, 5/55 °C), TBS was measured, and fracture types were determined. Data was analyzed using a 2-way ANOVA followed by Tukey–HSD, Kruskal–Wallis H and Mann–Whitney U tests as well as a Chi²-test and a Ciba–Geigy table (p < 0.05). Globally, the light curing units, followed by PEEK composition, was shown to have the highest impact on TBS. The HAL-LCUs, compared to the LED-LCUs, resulted in a higher TBS for all PEEK compositions—without significant differences between chairside and labside units. Regarding the different PEEK compositions, PEEK/20%, compared to PEEK/0%, resulted in a higher TBS when both, HAL-LCUs or LED-LCUs were used for labside application. In comparison with PEEK/>30%, PEEK/20% resulted in a higher TBS after using HAL-LCU for labside application. No significant differences were found between PEEK/0% and PEEK/>30%. HAL-LCU with PEEK/20% for labside application showed a higher TBS than HAL-LCU with PEEK/20% for chairside application, whereas LED-LCU with PEEK/>30% for chairside application showed a higher TBS than LED-LCU with PEEK/>30% for labside application. Full article

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16 pages, 5020 KiB

Open AccessArticle

Scaling-Up Techniques for the Nanofabrication of Cell Culture Substrates via Two-Photon Polymerization for Industrial-Scale Expansion of Stem Cells

by Davide Ricci¹

, Michele M. Nava^1,*

, Tommaso Zandrini², Giulio Cerullo², Manuela T. Raimondi¹

and Roberto Osellame²

¹ Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milano, Italy

² Istituto di Fotonica e Nanotecnologie (IFN)-CNR and Department of Physics, Politecnico di Milano, 20133 Milano, Italy

Materials 2017, 10(1), 66; https://doi.org/10.3390/ma10010066 - 13 Jan 2017

Cited by 44 | Viewed by 8300

Abstract

Stem-cell-based therapies require a high number (10⁶–10⁹) of cells, therefore in vitro expansion is needed because of the initially low amount of stem cells obtainable from human tissues. Standard protocols for stem cell expansion are currently based on chemically-defined [...] Read more.

Stem-cell-based therapies require a high number (10⁶–10⁹) of cells, therefore in vitro expansion is needed because of the initially low amount of stem cells obtainable from human tissues. Standard protocols for stem cell expansion are currently based on chemically-defined culture media and animal-derived feeder-cell layers, which expose cells to additives and to xenogeneic compounds, resulting in potential issues when used in clinics. The two-photon laser polymerization technique enables three-dimensional micro-structures to be fabricated, which we named synthetic nichoids. Here we review our activity on the technological improvements in manufacturing biomimetic synthetic nichoids and, in particular on the optimization of the laser-material interaction to increase the patterned area and the percentage of cell culture surface covered by such synthetic nichoids, from a low initial value of 10% up to 88% with an optimized micromachining time. These results establish two-photon laser polymerization as a promising tool to fabricate substrates for stem cell expansion, without any chemical supplement and in feeder-free conditions for potential therapeutic uses. Full article

(This article belongs to the Special Issue Materials for Hard and Soft Tissue Engineering: Novel Approaches)

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14 pages, 6397 KiB

Open AccessArticle

Laser Sintered Magnesium-Calcium Silicate/Poly-ε-Caprolactone Scaffold for Bone Tissue Engineering

by Kuo-Yang Tsai^1,†, Hung-Yang Lin^2,3,†, Yi-Wen Chen^3,4, Cheng-Yao Lin⁴, Tuan-Ti Hsu⁴ and Chia-Tze Kao^5,6,*

¹ Department of Oral and Maxillofacial Surgery, Changhua Christian Hospital, Changhua 500, Taiwan

² Department of Oral and Maxillofacial Surgery, China Medical University Hospital, Taichung 40447, Taiwan

³ Graduate Institute of Biomedical Sciences, China Medical University, Taichung 40447, Taiwan

⁴ 3D Printing Medical Research Center, China Medical University Hospital, China Medical University, Taichung 40447, Taiwan

⁵ School of Dentistry, Chung Shan Medical University, Taichung 40201, Taiwan

⁶ Department of Stomatology, Chung Shan Medical University Hospital, Taichung 40201, Taiwan

^† Both authors contributed equally to this work.

Materials 2017, 10(1), 65; https://doi.org/10.3390/ma10010065 - 13 Jan 2017

Cited by 66 | Viewed by 8166

Abstract

In this study, we manufacture and analyze bioactive magnesium–calcium silicate/poly-ε-caprolactone (Mg–CS/PCL) 3D scaffolds for bone tissue engineering. Mg–CS powder was incorporated into PCL, and we fabricated the 3D scaffolds using laser sintering technology. These scaffolds had high porosity and interconnected-design macropores and structures. [...] Read more.

In this study, we manufacture and analyze bioactive magnesium–calcium silicate/poly-ε-caprolactone (Mg–CS/PCL) 3D scaffolds for bone tissue engineering. Mg–CS powder was incorporated into PCL, and we fabricated the 3D scaffolds using laser sintering technology. These scaffolds had high porosity and interconnected-design macropores and structures. As compared to pure PCL scaffolds without an Mg–CS powder, the hydrophilic properties and degradation rate are also improved. For scaffolds with more than 20% Mg–CS content, the specimens become completely covered by a dense bone-like apatite layer after soaking in simulated body fluid for 1 day. In vitro analyses were directed using human mesenchymal stem cells (hMSCs) on all scaffolds that were shown to be biocompatible and supported cell adhesion and proliferation. Increased focal adhesion kinase and promoted cell adhesion behavior were observed after an increase in Mg–CS content. In addition, the results indicate that the Mg–CS quantity in the composite is higher than 10%, and the quantity of cells and osteogenesis-related protein of hMSCs is stimulated by the Si ions released from the Mg–CS/PCL scaffolds when compared to PCL scaffolds. Our results proved that 3D Mg–CS/PCL scaffolds with such a specific ionic release and good degradability possessed the ability to promote osteogenetic differentiation of hMSCs, indicating that they might be promising biomaterials with potential for next-generation bone tissue engineering scaffolds. Full article

(This article belongs to the Special Issue 3D Printing for Biomedical Engineering)

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