Materials — Open Access Journal of Materials Science

Subsphaeroidal SiC/polymer composite granules with good flowability for additive manufacturing/3D printing of SiC were prepared by ball milling with surface modification using polyvinyl butyral (PVB). PVB adheres to the particle surface of SiC to form a crosslinked network structure and keeps them combined with each other into light aggregates. The effects of PVB on the shape, size, phase composition, distribution and flowability of the polymer-ceramic composite powder were investigated in detail. Results show that the composite powder material has good laser absorptivity at wavelengths of lower than 500 nm. Full article

Polyethylene glycol (PEG)/hybrid carbon foam (CF) phase change materials (PCMs) were prepared by integrating PEG into CF via dynamic-vacuum impregnation. The hybrid CF was first synthesized by mixtures of graphene oxide (GO) and carbon nanotubes (CNTs) with different volume ratios. The morphologies, chemical structures, thermal conductivities, shape-stabilization levels, and photo-thermal energy conversion levels of these composite PCMs were characterized systematically. The prepared composite PCMs exhibited good shape-stabilization levels and showed their original shapes without any PEG leakage. It was found that the polyethylene glycol/carbon foam with multi-walled carbon nanotubes (PEG/MCF) composite PCMs had a better shape-stable performance below the temperature of 250 °C, and the thermal conductivity of the PEG/MCF composite PCMs reached as high as 1.535 W/(mK), which was obviously higher than that of polyethylene glycol/carbon foam with single-walled carbon nanotubes (PEG/SCF, 1.159 W/(mK)). The results of the photo-thermal simulation tests showed that the composite PCMs had the ability to absorb light energy and then convert it to thermal energy, and the maximum thermal energy storage efficiency of the PEG/MCF composite PCMs and the PEG/SCF composite PCMs was 92.1% and 90.6%, respectively. It was considered that a valuable technique to produce high-performance composite PCMs was developed. Full article

In this paper, the mechanical properties and minimum thermal conductivity of ZnZr, Zn₂Zr, Zn₂Zr₃, and MgZn₂ are calculated from first principles. The results show that the considered Zn-Zr intermetallic compounds are effective strengthening phases compared to MgZn₂ based on the calculated elastic constants and polycrystalline bulk modulus B, shear modulus G, and Young’s modulus E. Meanwhile, the strong Zn-Zr ionic bondings in ZnZr, Zn₂Zr, and Zn₂Zr₃ alloys lead to the characteristics of a higher modulus but lower ductility than the MgZn₂ alloy. The minimum thermal conductivity of ZnZr, Zn₂Zr, Zn₂Zr₃, and MgZn₂ is 0.48, 0.67, 0.68, and 0.49 W m⁻¹ K⁻¹, respectively, indicating that the thermal conductivity of the Mg-Zn-Zr alloy could be improved as the precipitation of Zn atoms from the α-Mg matrix to form the considered Zn-Zr binary alloys. Based on the analysis of the directional dependence of the minimum thermal conductivity, the minimum thermal conductivity in the direction of [110] can be identified as a crucial short limit for the considered Zn-Zr intermetallic compounds in Mg-Zn-Zr alloys. Full article

In this study, a series of chitosan-based quaternary ammonium graft flocculants, namely chitosan-graft-poly(acrylamide and methacryloyl ethyl trimethyl ammonium chloride) [CTS-g-P(AM-DMC)], was successfully synthesized by plasma initiation, and the as-prepared [CTS-g-P(AM-DMC)] had both flocculation and sterilization functions. Various characterization techniques were used to study the structure and physicochemical properties of the chitosan-based flocculants. ¹H nuclear magnetic resonance spectroscopy (¹H NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), and thermogravimetric analysis/differential scanning calorimetry (TG/DSC) confirmed the successful synthesis of CTS-g-P(AM-DMC). Scanning electron microscopy (SEM) analysis exhibited that CTS-g-P(AM-DMC) contained a smooth convex and porous structure with an enormous surface area. CTS-g-P(AM-DMC) was then used to flocculate the simulated wastewater of the kaolin suspension and the Salmonella suspension. Besides external factors, such as the dosage of flocculant and pH, the effect of the internal factor graft ratio was also evaluated. The experimental results showed that CTS-g-P(AM-DMC) also revealed a strong sterilization effect, aside from the excellent flocculation effect. Moreover, the sterilization mechanism was investigated through a series of conductivity measurements and the analysis of fluorescence-based cell live/dead tests. The results indicated that CTS-g-P(AM-DMC) destroyed the cell membrane of Salmonella through its grafted quaternary ammonium salt, thereby exhibiting sterilization property. Full article

As a novel energetic material with quite a high energy density, titanium hydride (TiH₂) was introduced into a polytetrafluoroethylene/aluminum (PTFE/Al) reactive material system for the first time. The effects of TiH₂ on the reaction energy, dynamic mechanical responses, and reaction properties of the composites were investigated through adiabatic bomb calorimeter, split-Hopkinson pressure bar, and drop-weight experiments. The results show that the reaction heat of the composites improved significantly as the content of TiH₂ increased. Under dynamic compression, these composites show obvious strain hardening and strain rate hardening effects. Besides, a certain amount of TiH₂ granules helps to improve the material’s compressive strength, and the maximum would even reach 173.2 MPa with 5% TiH₂ percentage, 10.1% higher than that of PTFE/Al. Mesoscale images of the samples after dynamic compression indicate that interface debonding between the particles and PTFE matrix and the fracture of the PTFE matrix are the two major mechanisms resulting in the material’s failure. In addition, the drop-weight experiments indicate that the material’s impact sensitivities are sensitive to the content of TiH₂, which would be increased to within 20% of the content of TiH₂ compared with PTFE/Al, and the reaction degree is also improved to within 10% of the content of TiH₂. The retrieved reaction residues after drop-weight experiments imply that the reaction is initiated at the edges of the samples, indicating a shear-induced initiation mechanism of this kind of reactive material. Full article

This in vivo study assessed (hard and soft) peri-implant tissue remodeling around implants with micro-ring and open-thread neck designs placed in a dog model. Twenty histological sections corresponding to four different implant designs that were placed in America Foxhound dogs were obtained from previous studies. All the implants had been placed under identical conditions and were divided into four groups: Group A, micro-rings on implant neck plus 0.5 mm refined surface; Group B, micro-rings on implant neck; Group C, open-thread neck; and, Group D, double-spiral neck. Eight weeks after surgery, the integrated implants were removed and processed for histological examination. Crestal bone loss and bone-to-implant contact was greater for micro-ring necks than open-thread necks. Soft tissues showed significant differences on both buccal and lingual aspects, so that the distance from peri-implant mucosa to the apical portion of the barrier epithelium was smaller in the micro-ring groups. So, in spite of generating greater bone-to-implant contact, implants with micro rings produced more bone loss than open-thread implants. Moreover, the outcomes that were obtained IPX implants smooth neck design produced less bone loss in the cervical area, following by Facility implants when compared with the other open thread and microthreaded implant designs. Implant thread design can influence on bone remodeling in the cervical area, related to bundle bone preservation. Full article

Due to the low absorption coefficients of crystalline silicon-based solar cells, researchers have focused on non-silicon semiconductors with direct band gaps for the development of novel photovoltaic devices. In this study, we use density functional theory to model the electronic structure of a large database of candidates to identify materials with ideal properties for photovoltaic applications. The first screening is operated at the GGA level to select only materials with a sufficiently small direct band gap. We extracted twenty-seven candidates from an initial population of thousands, exhibiting GGA band gap in the range 0.5–1 eV. More accurate calculations using a hybrid functional were performed on this subset. Based on this, we present a detailed first-principle investigation of the four optimal compounds, namely, TlBiS₂, Ba₃BiN, Ag₂BaS₂, and ZrSO. The direct band gap of these materials is between 1.1 and 2.26 eV. In the visible region, the absorption peaks that appear in the optical spectra for these compounds indicate high absorption intensity. Furthermore, we have investigated the structural and mechanical stability of these compounds and calculated electron effective masses. Based on in-depth analysis, we have identified TlBiS₂, Ba₃BiN, Ag₂BaS₂, and ZrSO as very promising candidates for photovoltaic applications. Full article

Earlier work had indicated that enzyme-mediated hydrolysis of xylooligomer-rich water-soluble streams (derived from steam pre-treated wheat straw) resulted in the effective production of xylose which was subsequently used to produce bio-glycol. In the work reported here, both the thermostability and recyclability of xylanases were significantly improved by covalent immobilizing the enzymes onto alginate beads. The immobilized xylanases showed a lower hydrolytic potential (~55% xylooligomer conversion) compared to the commercial xylanase cocktail HTec3 (~90% xylooligomer conversion) when used at the same protein loading concentration. This was likely due to the less efficient immobilization of key higher molecular weight enzymes (>75 kDa), such as β-xylosidases. However, enzyme immobilization could be improved by lowering the glutaraldehyde loading used to activate the alginate beads, resulting in improved hydrolysis efficacy (~65% xylooligomer conversion). Enzyme immobilization improved enzyme thermostability (endoxylanase and β-xylosidase activities were improved by 80% and 40%, respectively, after 24 h hydrolysis) and this allowed the immobilized enzymes to be reused/recycled for multiple rounds of hydrolysis (up to five times) without any significant reduction in their hydrolytic potential. Full article

Bioactive alloplastic materials, like beta-tricalcium phosphate (β-TCP) and calcium sulfate (CS), have been extensively researched and are currently used in orthopedic and dental bone regenerative procedures. The purpose of this study was to compare the performance of EthOss versus a bovine xenograft and spontaneous healing. The grafting materials were implanted in standardized 8 mm circular bicortical bone defects in rabbit calvariae. A third similar defect in each animal was left empty for natural healing. Six male rabbits were used. After eight weeks of healing, the animals were euthanized and the bone tissue was analyzed using histology and micro-computed tomography (micro-CT). Defects treated with β-TCP/CS showed the greatest bone regeneration and graft resorption, although differences between groups were not statistically significant. At sites that healed spontaneously, the trabecular number was lower (p < 0.05) and trabecular separation was higher (p < 0.05), compared to sites treated with β-TCP/CS or xenograft. Trabecular thickness was higher at sites treated with the bovine xenograft (p < 0.05) compared to sites filled with β-TCP/CS or sites that healed spontaneously. In conclusion, the novel β-TCP/CS grafting material performed well as a bioactive and biomimetic alloplastic bone substitute when used in cranial defects in this animal model. Full article

Short silicon nitride fibers were fabricated by direct nitridation of ferrosilicon in N₂ atmosphere, and their structure and possible growth mechanism were characterized and investigated. The rod-like fibers which were α-Si₃N₄ with a low degree of crystallization and a high aspect ratio had a diameter of about 4 μm and a length close to a few millimeters. Belt-like fibers with a width about 5 μm and a thickness about 1 μm were also found in the nitrides. Scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM), and selected area electron diffraction (SAED) investigations indicated that the fibers were single-crystalline α-Si₃N₄ with few amorphous distributed in the edge region, and the fibers grew by vapor–liquid–solid (VLS) mechanism. Full article

Electronic structure and corresponding electrical properties of PbPdO₂ and PbPd_0.75Co_0.25O₂ ultrathin slabs with (002) preferred orientation were systematically investigated using first-principles calculations. The calculated results revealed the strain induced evidently the changes of band structure and carrier concentration in both slabs. It was also found that PbPdO₂ and PbPd_0.75Co_0.25O₂ ultrathin slabs exhibited evident differences in the external strain dependence of the band gap and charge carrier concentration, which was strongly dependent on bond angle and bond length induced by in-plane anisotropy strain. Interestingly, the carrier concentration of the PbPd_0.75Co_0.25O₂ slab could increase up to 5–6 orders of magnitude with the help of external strain, which could explain the potential mechanism behind the observed colossal strain-induced electrical behaviors. This work demonstrated that the influence of the doping effect in the case of PbPdO₂ could be a potentially fruitful approach for the development of promising piezoresistive materials. Full article

For the general quantitative evaluation of the flow characteristics of a material, various factors that affect the flow should be examined. Notably, cement paste shows multi-dimensional flow characteristics owing to not only its inherent features such as its various particle sizes and hydration reaction, but also due to environmental factors including temperature, humidity, and pressure. Therefore, an analysis of those environmental factors is important for the quantitative evaluation of the flow characteristics of cement paste. In this study, we analyzed the flow characteristics of cement paste and a newly developed standard reference material (SRM) that has similar flow characteristics to cement paste at different temperatures. For the analysis, the flow characteristics of each cement paste mixture at five different temperatures (5 °C, 10 °C, 20 °C, 30 °C, and 40 °C) were examined, in consideration of variations in construction environments. Then, the flow characteristics of the developed SRM at different temperatures were also analyzed. The result of the analysis demonstrated a decrease in the rheology constant value following a rise in the temperature. Notably, the degree of variation in the flow characteristics was larger at a lower temperature, while flow characteristics remained nearly constant at higher temperatures. The result of the analysis also confirmed that cement paste and the newly developed SRM displayed similar tendencies for the change in flow characteristics following a change in temperature. In conclusion, the newly developed SRM is thought to be useful for consistently representing the flow characteristics of cement paste under various construction environments in consideration of temperature change. Full article

In this paper, the fracture behavior of GaN piezoelectric semiconductor ceramics was investigated under combined mechanical and electric loading by using three-point bending tests and numerical analysis. The experimental results demonstrate that, in contrast to traditional insulating piezoelectric ceramics, electric current is a key factor in affecting the fracture characteristics of GaN ceramics. The stress, electric displacement, and electric current intensity factors were numerically calculated and then a set of empirical formulae was obtained. By fitting the experimental data, a fracture criterion under combined mechanical and electrical loading was obtained in the form of an ellipsoid function of intensity factors. Such a fracture criterion can be extended to predict the failure behavior of other piezoelectric semiconductors or devices with a crack, which are useful in their reliability design and applications. Full article

Warp-knitted meshes have been widely used for structural reinforcement of rigid, semi-rigid, and flexible composite materials. In order to meet the performance requirements of different engineering applications, four typical warp-knitted meshes (rectangular, square, circular, and diamond) were designed and developed. The mechanical behaviors of these meshes under mono-axial and multi-axial tensile loads were compared. The influence of the initial notch length and orientation on the mechanical performance was also analyzed. The results showed that the biaxial tensile behavior of warp-knitted meshes tended to be more isotropic. The anisotropy level of the diamond warp-knitted mesh was the lowest (λ = 0.099), while the rectangular one was the highest (λ = 0.502). The notch on a significantly anisotropic mesh was propagated along the direction of larger modulus, while for a not remarkably anisotropic mesh, notch propagation was probably consistent with the initial notch orientation. The breaking strength of warp-knitted meshes with the same initial notch orientation decreased with the increase in notch length in both the wale and course directions. For warp-knitted meshes with the same initial notch length, the breaking strength in the wale direction was kept stable at different notch orientations, while that in the course direction decreased remarkably with notch orientation from 0° to 90°. Full article

A simple 1,2-squaraine based chemosensor material (SQ) has been reported to show dual sensing performance for colorimetric detection of Fe³⁺ and Hg²⁺ ions. Compared to common instrumental analysis, this method could provide fast and direct detection though colorimetric changes by the naked eye. The sensor has shown excellent selectivity over the other metal ions by tuning different solvent environments. The detection limit for Fe³⁺ could reach to 0.538 μM, which was lower than that in the environmental agency guideline (U.S. Environmental Protection Agency, U.S. EPA) in drinking water. And for Hg²⁺ detection, the limit was calculated as 1.689 μM in our case. A 1:1 binding mode between SQ–Fe³⁺ and SQ–Hg²⁺ ion were evidenced by Job’s plot measurement and IR analysis. The proposed different binding mechanisms were also supported by Density Function Theory (DFT) calculation. All these findings provide a unique material and a simple, facile, and low cost colorimetric method for dual metal ions analysis and have shown preliminary analytical applications in industrial water sample analysis. Full article

To fill the shortages in the knowledge of the pyrolysis and combustion properties of new and aged polyvinyl chloride (PVC) sheaths, several experiments were performed by thermogravimetric analysis (TG), Fourier transform infrared (FTIR), microscale combustion calorimetry (MCC), and cone calorimetry. The results show that the onset temperature of pyrolysis for an aged sheath shifts to higher temperatures. The value of the main derivative thermogravimetric analysis (DTG) peak of an aged sheath is greater than that of a new one. The mass of the final remaining residue for an aged sheath is also greater than that of a new one. The gas that is released by an aged sheath is later but faster than that of a new one. The results also show that, when compared with a new sheath, the heat release rate (HRR) is lower for an aged one. The total heat release (THR) of aged sheath is reduced by 16.9–18.5% compared to a new one. In addition, the cone calorimetry experiments illustrate that the ignition occurrence of an aged sheath is later than that of a new one under different incident heat fluxes. This work indicates that an aged sheath generally pyrolyzes and it combusts more weakly and incompletely. Full article

In the present study, the newly synthesized castor oil-derived thioether-containing ω-hydroxyacid (TEHA) block copolymers with polycaprolactone (TEHA-b-PCL), with methoxypoly(ethylene glycol) (mPEG), (TEHA-b-mPEG) and with poly(ethylene glycol) (PEG) (TEHA-b-PEG-b-TEHA), were investigated as polymeric carriers for fabrication of naltrexone (NLX)-loaded microspheres by the single emulsion solvent evaporation technique. These microspheres are appropriate for the long-term treatment of opioid/alcohol dependence. Physical properties of the obtained microspheres were characterized in terms of size, morphology, drug loading capacity, and drug release. A scanning electron microscopy study revealed that the desired NLX-loaded uniform microspheres with a mean particle size of 5–10 µm were obtained in all cases. The maximum percentage encapsulation efficiency was found to be about 25.9% for the microspheres obtained from the TEHA-b-PEG-b-TEHA copolymer. Differential scanning calorimetry and X-ray diffractometry analysis confirmed the drug entrapment within microspheres in the amorphous state. In vitro dissolution studies revealed that all NLX-loaded formulations had a similar drug release profile: An initial burst release after 24 h, followed by a sustained and slower drug release for up to 50 days. The analysis of the release kinetic data, which were fitted into the Korsmeyer–Peppas release model, indicated that diffusion is the main release mechanism of NLX from TEHA-b-PCL and TEHA-b-mPEG microspheres, while microspheres obtained from TEHA-b-PEG-b-TEHA exhibited a drug release closer to an erosion process. Full article

Brain‒machine interface (BMI) is a promising technology that looks set to contribute to the development of artificial limbs and new input devices by integrating various recent technological advances, including neural electrodes, wireless communication, signal analysis, and robot control. Neural electrodes are a key technological component of BMI, as they can record the rapid and numerous signals emitted by neurons. To receive stable, consistent, and accurate signals, electrodes are designed in accordance with various templates using diverse materials. With the development of microelectromechanical systems (MEMS) technology, electrodes have become more integrated, and their performance has gradually evolved through surface modification and advances in biotechnology. In this paper, we review the development of the extracellular/intracellular type of in vitro microelectrode array (MEA) to investigate neural interface technology and the penetrating/surface (non-penetrating) type of in vivo electrodes. We briefly examine the history and study the recently developed shapes and various uses of the electrode. Also, electrode materials and surface modification techniques are reviewed to measure high-quality neural signals that can be used in BMI. Full article

This study evaluated the effect of UltraSonic Treatment (UST) on a range of Al–Mg alloys. Previous research was carried out on single magnesium compositions. However, the amount and type of the alloy addition are known to affect the grain size even under UST, and the aim of this study was to determine whether or not alloy composition plays a similar role in the case of Al–Mg alloys. By testing binary Al–Mg alloys cast under regular casting conditions and under the presence of an ultrasonic field, it was found that while the addition of Mg solute is important, the amount of solute has little effect when UST is applied. It was observed that the grain size was barely affected by extra solute additions in this condition. This is due to the application of UST during solidification, which resulted in a dramatic reduction in the size of the nucleation free zone thus promoting many more successful nucleation events. Acoustic streaming is proposed as the main cause of this reduction in grain size. Full article