Chitosan is an important cationic biopolymer widely used in various biomedical applications such as wound care, drug delivery, biomaterial scaffolds, and tissue engineering. In this work, hollow silica sphere (HSS) nanoparticles with an average size of 400–450 nm (via TEM) were synthesized by sol–gel process and were epoxidized using epichlorohydrin. Then, chitosan was chemically bound to the epoxidized HSS to form a bionanocomposite, HSS-epoxy-CHI-X where X represents the percentage of chitosan in the sample. BET analysis showed that pure HSS has a specific surface area (Ass) of around 4.8 m2/g and adsorption average pore diameter of 10.18 nm. Bionanocomposites were characterized by FT-IR spectroscopy to confirm the bonding of chitosan on HSS nanoparticles. X-ray diffraction studies demonstrated that the amorphous character of the materials improved with the HSS content. Thermogravimetric analysis illustrated that at low temperatures, the thermal stability of bionanocomposites was higher than that of the sample with no chitosan in it. Scanning electron microscopic analysis results confirmed the homogenous distribution of HSS in the bionanocomposites. Considering the biological activity of chitosan and absorption characteristics of HSS, newly developed HSS-epoxy-CHI-X bionanocomposites were tested for wound healing by in vitro scratch assay using NIH 3T3 fibroblast cells. Among the bionanocomposites analyzed, HSS-epoxy-CHI-60 exhibited better performance where about 90% wound closure was observed for this sample after 21 h of exposure.

The growth advantage of twinned dendrites over regular columnar ones was systematically investigated during Bridgman solidification. An experimental approach was designed and the results indicated that the strong twin growth advantage lost its efficiency in the coexisting microstructure containing both twinned and regular dendrites at a low growth rate of 10 μm/s. The twin growth advantage derives from three essential components: the lateral twin propagation perpendicular to twin plane (Rx), the propagation parallel to twin plane (Ry), and the dendrite tip growth (Rz). The lateral extension component Rx played a vital role and would be limited at a low rate. Meanwhile, the tip undercooling of the twinned dendrite was estimated based on its plate-like growth morphology. Furthermore, the competitive growth between twinned dendrites was investigated in different feathery grains. When the included angle between twin planes was relatively large, the lateral twin propagation would keep down the in-plane twin propagation.

The formation of low-angle grain boundaries (LABs) in the rejoined platforms of a Ni-based single crystal superalloy under different directional solidification rates was investigated by the experimental investigation and the ProCAST simulation. The results showed that the growth morphology and orientation evolution of dendrites in the platforms were different under the withdrawal rates in the range of 60–100 μm/s and then resulted in different types of LABs. At lower withdrawal rates, the longitudinal LABs were common in the rejoined platforms. Both the sliver defects and the orientation deviation of original primary dendrites from two independent growth paths could cause the longitudinal LABs in the platforms. At higher withdrawal rates, the dendrite growth patterns were more complex and the secondary branches with lateral growth tended to deviate from their original orientation, eventually leading to the formation of some transverse LABs. Finally, some suggestions to prevent the formation of different LABs are provided.

High-purity niobium single crystals of five different orientations were compressed at 77 K to 2–4% plastic strain to investigate the mechanisms operative in the initial stage of yielding. The crystals deformed in the direction close to the [001] axis exhibit predominant slip on the high-stressed (101) and a much lower stressed $\left( {0\bar{1}1} \right)$ plane. The expected slip on the $\left( {\bar{1}01} \right)$ plane is nearly homogeneously distributed with only a few sharp slip traces corresponding to localized slip. The samples compressed along center-triangle orientations and those close to the $\left[ {011} \right] - \left[ {\bar{1}11} \right]$ edge deform predominantly by twinning on {112}〈111〉 systems with some contribution from slip on the $\left( {\bar{1}01} \right)\left[ {\bar{1}\bar{1}\bar{1}} \right]$ system with the highest Schmid factor. A majority of twins exhibit internal contrast due to alternating slip on $\left( {\bar{1}01} \right)$ and $\left( {0\bar{1}1} \right)$ planes. No slip traces are observed in the matrix adjacent to the twin, which implies that twin boundaries are impenetrable obstacles for the motion of dislocations.

A mechanical model is developed to explain the influence of grain rotation on nanovoid growth in nanocrystalline solids in the current paper. In the framework of the mechanical model, the dislocations released from the nanovoid surface will be affected by four stresses: the driving stress induced by far-field stress, the stress arising from grain rotation, the image stress caused by the free surface of the nanovoid, and the back stress generated by the previously emitted dislocations. Furthermore, under the condition of different rotational strength and surface effects, we analyzed in detail the influence of the important parameters such as nanovoid radius, nucleation radius, dislocation emission angle, relative distance, rotation grain size, rotation coefficient, and direction angle on the critical stress. Finally, we discuss the effect of the coupling of rotational deformation and the grain boundary on the growth of the nanovoid. As a conclusion, the high stress nearby the nanovoid can be released by grain rotation, which inhibits the growth of the nanovoid.

An analytical research is developed using the averaging technique of composites for the macroscopic behaviors of porous shape memory alloy (SMA) beam with different porosity under pure bending. The whole material is regarded as a composite beam of porous SMA and dense SMA, in which the component fractions of the porous SMA show gradient changes over geometric dimension. To get the theoretical solution of such material under pure bending, the Mises yield theory and the ideal elastoplastic model are used to describe the phase transition of the material. The macroscopic behaviors of the porous SMAs beam with different porosity are then simulated using the averaging technique of composites. Examples for a porous SMA beam with gradient porosity from 0 to 50% considering the tension compression asymmetry of the SMAs are then supplied; the results show that after transformation the stress distribution in the whole material is lower than in the case of the pure elastic gradient porous materials, and for different part of the SMA with different porosity shows different strength characters.

The effect of zirconium alloying on the crystal structures and mechanical properties of binary tungsten–zirconium alloys is investigated in this study using the first-principles method. Firstly, we investigate the cell volumes, lattice constants, and formation energies of binary W1−xZrx (x = 0, 0.0625, 0.125, 0.1875, 0.25, and 0.5) alloys. It is shown that binary tungsten–zirconium alloys maintain BCC structures. When the concentration of zirconium atoms is lower than 12.5%, the structures of binary tungsten–zirconium alloys can be thermodynamically stable. The elastic constants of binary tungsten–zirconium alloys are calculated based on the optimized atomic lattice. Then, the elastic modulus and other mechanical parameters are deduced according to the relevant formulas. It is shown that the mechanical strength of binary tungsten–zirconium alloy decreases with an increasing concentration of zirconium atoms, which is lower than the mechanical strength of pure tungsten metal. However, the mechanical strength of binary tungsten–zirconium alloys is higher than that of pure zirconium metal. In addition, zirconium alloying can be effective in improving the ductility of pure tungsten metal.

The microstructure and oxidation behavior at high temperatures ranging from 900 °C to 1100 °C of equiatomic CrMoNbTaV high-entropy alloy produced by vacuum arc melting were investigated. The phase component, microstructure, and microhardness of the alloy were examined by using X-ray diffraction, scanning electron microscopy equipped with an energy-dispersive X-ray spectroscope, and Vickers hardness tests, respectively. The as-cast alloy consists of a single body-centered cubic (BCC) refractory metal solid solution due to the high mixing entropy effect and exhibits a dendritic microstructure. The alloy has a very high microhardness value of 923 HV due to the strong solid solution strengthening effect. The average microhardness in interdendrites (950 HV) was higher than that in dendrites (896 HV) because of composition segregation. The oxidation kinetic curves of the alloy after exposure to air at 900 and 1000 °C follow the pseudo-parabolic rate law, while the mass gain increases first and then decreases at 1100 °C. The thickness of the oxide layer increases with the increasing of oxidation time. The long rod-shaped oxidation products are composed of Nb2O5, NbO2, CrTaO4, CrNbO4, Ta9VO25, Nb9VO25, and TaO after oxidation at 900 and 1000 °C for 25 h. The oxides of CrTaO4 and CrNbO4 disappear as the oxidation temperature elevated to 1100 °C.

The flow softening behavior caused by deformation heating of the 6063 aluminum alloy was investigated employing uniaxial compression tests. The adiabatic correction factor (η) and mechanical work partitioning factor (φ), commonly considered to be constant, were found to be highly variable at medium strain rates, namely from 0.01 to 10 s−1. η decreased with increasing strain and decreasing strain rate, but it was relatively not sensitive to temperature. φ, traditionally taken to be a constant of 0–10%, was found to vary from 2.8% at a temperature of 623 K and a strain rate of 10 s−1 to 26.8% at a temperature of 773 K with a strain rate of 0.01 s−1. An expression for temperature rise involving these two variable factors was optimized. FEM simulation using the corrected and uncorrected true stress–strain curves and corresponding extrusion experiment were carried out. Comparisons between the simulated and experimental results confirmed the temperature compensation was trustable.

The microstructure evolution of a typical nickel-based superalloy was studied in the strain range of 0.1–0.9 at 1110 °C/0.01 s−1 by using the electron backscattered diffraction technique. It was found that the evolution of recrystallized microstructures, grain boundary characteristics, and textures was closely related to strain level. With the increasing strain level, the fraction of equiaxed dynamic recrystallization (DRX) grains increased significantly at the expense of the large non-recrystallized grains, and there was a decrease in total low angle grain boundaries fraction and a simultaneous increase in the fraction of high angle grain boundaries. In addition, the occurrence of DRX promoted the formation of Σ3 boundaries, and the coherent Σ3 boundaries were much easier to form at the strain above 0.5. On the other hand, 〈100〉 component of the textures became stronger with the increasing strains, and the lack of 〈111〉 orientations can also be observed in the textures at high strains above 0.7.

The effect of SiCp on the aging behavior of the extruded SiCp/AZ91 composite fabricated by stir casting was investigated in detail. The necklace-type distribution of the particles in the cast SiCp/AZ91 composite was destroyed, and the extrusion bands consisting of SiCp and small dynamic recrystallized grains formed aligning along the extrusion direction. Addition of SiCp could accelerate the aging kinetics of the AZ91 matrix because of the overlapped particle plastic zone. The improved particle distribution and refined grains caused by the recrystallization could affect the aging behavior of the SiCp/AZ91 composite. The Mg17A112 discontinuous precipitates preferred to nucleate at the SiC/Mg interfaces and the grain boundaries within the extrusion bands and then expanded into the particle-free region. Moreover, the promoted discontinuous precipitates would suppress the continuous intragranular precipitates with respect to the unreinforced AZ91 alloy.

Ti/Al/Mg/Al/Ti laminates were fabricated by hot rolling at 450 °C with various rolling reductions, and the relationship between the mechanical properties and microstructures was investigated in detail. Both Al–Mg and Ti–Al interfaces are well bonded without pore, crack, and intermetallics. Mg layer of 50% rolling reduction has the most dynamic recrystallized (DRXed) grains around the deformation bands, and tensile twins appear in Mg layer when the rolling reduction increases to 60%. Large numbers of twins are formed to absorb the further strain as reduction increases. Ti layer shows equiaxed grains, which are not sensitive to thickness strain. Mg layers of laminates with various rolling reductions all exhibit typical (0002) basal texture. Fifty-percent rolling reduction has the largest ultimate tensile strength of 337.8 MPa, which is mainly owing to grain refinement caused by the extensive DRX. The differences of elongation among the three samples with different rolling reductions are small.