Microcellular injection molding, a process capable of mass-producing complex plastic parts, and particle leaching methods were combined to fabricate porous thermoplastic polyurethane tissue engineering scaffolds. Water soluble polyvinyl alcohol (PVOH) and sodium chloride (NaCl) were used as porogens to improve the porosity and interconnectivity as well as the hydrophilicity of the scaffolds. It was found in the study that the microcellular injection molding process was effective at producing high pore density and porosity. The addition of PVOH decreased the pore diameter and increased the pore density. Furthermore, scaffolds with NaCl and PVOH porogens showed more interconnected pores. The 3T3 fibroblast cell culture was used to confirm the biocompatibility of the scaffolds. Residual PVOH content after leaching increased the hydrophilicity of the scaffolds and further improved cell adhesion and proliferation. The resulting scaffolds offer an alternative scalable tissue scaffold fabrication method for soft tissue scaffold production.

The 8 mol% yttria-stabilized zirconia (8Y-ZrO2) was bonded to stainless steel 316L at 900 °C for 1 h in a protective Ar atmosphere using an interlayer of Ti/Ni/Ti. Interfacial microstructures were characterized using both secondary electron microscope (SEM) and transmission electron microscope (TEM), each with an attached energy dispersive spectroscope (EDS). A layer sequence of σ-phase/TiFe2/TiFe + β-Ti/Ti2Fe was observed at the stainless steel 316L/Ti interface, whereas a layer sequence of Ti2Ni/Ti2Ni + TiNi/TiNi3 was found at the Ti/Ni interface. Furthermore, TiO and c-ZrO2−x formed at the Ti/8Y-ZrO2 interface. An acicular α-Ti and a fine ω-phase existed along with β-Ti in the residual Ti foil adjacent to the stainless steel 316L, but α-Ti and Ti2Ni were observed within β-Ti in the other residual Ti foil adjacent to the 8Y-ZrO2. The orientation relationships of the ω-phase and β-Ti were ${\left[ {1\bar 10} \right]_{{\rm{ \beta {\hbox-} Ti}}}}//{\left[ {1\bar 210} \right]_{\rm{\omega }}}$ and ${\left( {111} \right)_{{\rm{\beta {\hbox-} Ti}}}}//{\left( {0001} \right)_{\rm{\omega }}}$, respectively. The microstructural development was elucidated with the aid of Fe–Ti and Ni–Ti binary phase diagrams.

Two phases of nickel sulfide (α-NiS and β-NiS) nanoarchitectures were successfully and controllably synthesized by a facile solvothermal method with two different solvents of alcohol and water, respectively. The products were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectrophotometer. The sphere-like shape for α-NiS and cross-like shape composed of nanorods for β-NiS are uniform and well distributed as well as their size. Both α-NiS and β-NiS powders were used as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). It is found that the DSSC with an α-NiS CE performs much better than the one with a β-NiS CE. The energy conversion efficiency of the former was 5.2%, whereas the latter was 4.2%, about 20% increment.

The growth mechanism of an icosahedral quasicrystal and solute partitioning in a Mg-rich Mg–Zn–Y alloy were investigated. It is found that the preferred growth directions of the icosahedral quasicrystalline phase (I-phase) are along 5-fold axes and the planes perpendicular to the 5-fold axes grow in a facet manner. Due to the local compositional change at the solid/liquid interface, the planar growth is gradually replaced by cellular growth. During the nucleation of the primary I-phase, on a microscale, the distribution of the Y element is changed and concentrated along 5-fold directions in the remaining liquid. If the cooling rate is relatively slow, there will be more Y element in the remaining liquid after the formation of the primary I-phase. It causes that (I-phase + α-Mg) eutectic structures form around the primary I-phase. Almost all the Y element is exhausted after this stage. Especially, under a relatively slow cooling rate, the solute partitioning occurs during the growth process of the primary I-phase, which leads to the microshrinkage cavity and crack defects at the edge of the primary I-phase.

A multistep heat treatment process consisting of intercritical tempering between quenching and conventional tempering contributed to the development of a ferrite–martensite dual-phase structure in a Ni- and Cu-containing high-strength low-alloy steel. By using electron backscatter diffraction and scanning transmission electron microscopy, the microstructures were found to have an elongated lathlike morphology with carbide and Cu precipitates located especially at the boundaries of ferrite and martensite crystals. Atom probe tomography reveals at atomic scale the existence of solute-diluted ferrite and solute-rich martensite, and the later phase was considered to be transformed from the reverse austenite that was formed during intercritical tempering. Cu precipitation greatly correlates with the microconstituents, resulting in different distributional characteristics of Cu precipitates within these two phases and at their boundaries. It is a promising process to utilize Cu precipitation strengthening and phase transformation toughening simultaneously in alloy steels.

For years, substituted iron nitrides have been studied by various types of approaches: physical, chemical, and materials engineering, both experimental and theoretical. More recently, substituted iron nitrides have been studied by theoretical models for calculation of electronic structure, presenting the advantage of being economically viable. The properties of these compounds have potential application not only as a recording material but also in other areas: as resistance to corrosion and wear. The changes occurred in the alloys when transformed into nitrides still require further studies. Thus, the electronic and magnetic structure of IrFe3 and Ir3Fe alloys and the changes caused in their ground state properties when the nitrogen atoms were included in their stoichiometry, turning them into substituted iron nitrides type Ir3FeN and IrFe3N, will be investigated in this study. The electronic structure of these compounds was modeled using the linearized augmented plane waves (LAPW), an augmented plane wave (APW – method of Slater) modification. The following methodology was used in this study: the cohesive energy for steady state was calculated and then the ground state properties, such as charge transfer, magnetic moment, hyperfine properties, and the density of states, were obtained. The ground state properties are also assessed from the pressure variation experienced by these compounds, that way, the induced changes in the alloys caused by introducing the nitrogen atom are obtained. This study may assist in obtaining new and better nitrides.

The variant selection from the parent α phase to the product β phase during the enhanced phase transformation induced by the electric current pulses (ECPs) was investigated in a Cu–Zn alloy. The electron backscatter diffraction results showed that the crystallographic variant selection was not only across those prior α/α grain boundaries, but also within the α grain interior, and it implied that the nucleation of the β phase on the up-transformation obeyed a preferred orientation selection. Further analysis revealed that the orientation relationship between the α phase and the β phase variants nucleated from the α phase was close to 44.3° about <114>, which clearly described the rotation axes and the misorientation angles in terms of an axis/angle description when the high temperature phase nucleated from the matrix. Therefore, the ECP treatment would provide a new promising and convenient method to investigate the variant evolution on the up-transformation.

We report on the occurrence of sinter-hardening with concurrent improved plasticity in fine-grained Fe79.3Mo4.5P8.1C6.75B1.35 bulk alloys fabricated by spark plasma sintering (SPS) of metallic glass composite powder. When the sintering temperature is higher than the austenite transformation temperature, the as-fabricated bulk alloys are composed of expected wattle martensite plus Fe3P, Fe7C3, and Fe3Mo3C. Meanwhile, the martensite-containing bulk alloys exhibit increased hardness, fracture strength as well as concurrent improved plasticity. The fracture stress and strain of the martensite-containing bulk alloys are as high as 2573 MPa and 8.6%, respectively. The formation of the martensite microstructure is attributed to that high sintering temperature leads to the austenitization transformation and consequently formed austenite partially transforms into martensite under rapid cooling rate provided by SPS system. The results obtained provide insight into fabrication of iron alloys with good mechanical property by powder metallurgy.

Cobalt crystals with hcp or hcp/fcc mixed structure were prepared by a solvothermal process based on the dosages of N2H4·H2O and the effect of crystal structure on their magnetic properties and Congo red (CR) removal abilities was studied. To our best knowledge, it is the first report on CR removal by micrometer and submicrometer sizes of Co crystals with the best CR removal ability reaching 694.4 mg g−1. For the hcp and fcc mixed structure, the degree of mixing can be clearly observed from the high-resolution transmission electron microscopy images. The micrometer and submicrometer sizes of Co crystals will be good for magnetic separation after CR removal.

Isothermal annealing in the temperature range of 300–600 °C, microstructural characterization, and analysis of the grain growth kinetics during annealing were carried out for Cu–5 vol% Al2O3 nanocomposite powder particles produced by high energy mechanical milling. When the annealing temperature was 400 °C or lower, only reduction in dislocation density occurred during annealing. When the annealing temperature was 500 °C or higher, reduction in dislocation density, abnormal grain growth of the nanocrystalline Cu matrix, and coarsening of the Al2O3 nanoparticles occurred. It has been found that the microstructure of the nanocrystalline Cu matrix of the nanocomposite exhibits a far higher thermal stability than that of monolithic nanocrystalline Cu, even though the apparent activation energy of the grain growth of the former is similar to that of the latter over the temperature range of 400–600 °C, showing the dramatic drag effects of finely distributed Al2O3 nanoparticles and Al3+/O2− clusters on the grain boundary motion.

The low-temperature joining technique (LTJT) by silver sintering is being implemented by major manufacturers of power electronic devices and modules for bonding power semiconductor chips. A common die-attach material used with LTJT is a silver paste consisting of silver powder (micrometer- or nanometer-sized particles) mixed in organic solvent and binder formulation. It is believed that the drying of the paste during the bonding process plays a critical role in determining the quality of the sintered bond-line. In this study, a model based on the diffusion of solvent molecules and viscous mechanics of the paste was introduced to determine the stress and strain states of the silver bond-line. A numerical simulation algorithm of the model was developed and coded in the C++ programming language. The numerical simulation allows determination of the time-dependent physical properties of the silver bond-line as the paste is being dried with a heating profile. The properties studied were solvent concentration, weight loss, shrinkage, stress, and strain. The stress is the cause of cracks in the bond-line and bond-line delamination. The simulated results were verified by experiments in which the formation of bond-line cracks and interface delamination was observed during the pressure-free drying of a die-attach nanosilver paste. The simulated results were consistent with our earlier experimental findings that the use of uniaxial pressure of a few mega-Pascals during the drying stage of a nanosilver paste was sufficient to produce high-quality sintered joints. The insight offered by this modeling study can be used to develop new paste formulations that enable pressure-free, low-temperature sintering of the die-attach material to significantly lower the cost of implementing the LTJT in manufacturing.

Carbon foams were successfully fabricated from sucrose and kaolinite clay by thermo-foaming method using aluminum nitrate as the blowing agent. The phases, pore structure, and compressive strength were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and mechanical test, respectively. The foams had porous structure with spherical open cells of size in the range of 400–1000 μm, dense struts, and interconnected voids of size in the range of 100–600 μm. Both smooth and coarse types of voids are observed. Mullite and cristobalite, products of the clay mineral, are concentrated more on the strut and cell walls. The ultimate compressive strength evolution is found to be in correlation with the amount of voids and the microcracking in the carbon foams.