In this study, the authors have comparatively studied the influence of H2 addition on the structures and properties of ZnO films grown by metal organic (MO) chemical vapor deposition with dimethyl zinc and diethyl zinc as zinc precursors and N2O and O2 as oxygen sources, respectively. Various characterization methods, like x-ray diffraction, Raman scattering, Hall effect, photoluminescence, and atomic force microscopy, have been utilized, showing that H2 has different effects on different MO precursors and oxidants. The H2 addition has significantly improved the crystal structural quality of ZnO thin films for the case of dimethyl zinc source, but an opposite effect has been found for the case of diethyl zinc. Moreover, the H2 addition can significantly improve the optical properties of the ZnO films, regardless of the zinc MO sources used, with the surface morphology improved too. The suppression of carbon-related contaminations depends on the use of different precursors and whether H2 is added. By analyzing the experimental results, we have given the effects of H2 on the decomposition of the discussed MO precursors and oxidants, the proposed mechanism could be used in understanding the experimental data.

In this study, BaCu(B2O5) (BCB) is utilized as the sintering aids to decrease the sintering temperature of Ba3(Co0.4Zn0.6)2Fe24O41 [(Co0.4Zn0.6)2Z]. The influence of BCB addition on the microstructures as well as the dielectric and magnetic properties of the (Co0.4Zn0.6)2Z ceramic samples is investigated. It is found that the 5 wt% BCB added (Co0.4Zn0.6)2Z sintered at 925 °C exhibits both a high relative density of about 95% and a homogeneous microstructure with few pores existing. Both the relative permittivity and permeability of the sample keep stable from 10 to 800 MHz. Also, the dielectric and magnetic loss are low and effectively suppressed within a wide frequency range. For the specimen with 5 wt% BCB, the dielectric and magnetic loss tangent are 0.003 and 0.039 at 200 MHz, respectively. In addition, a compatibility test with Ag powders has been carried out. The optimized properties indicate that this kind of low temperature sintered Z-type hexaferrite is a good candidate for the applications of multilayer chip inductors.

In this study, resistive switching (RS), polarization switching, and charge distribution under DC bias in undoped ZnO thin films are studied by applying scanning probe microscopy (SPM) techniques on the same location. The techniques include Piezoresponce Force Microscopy, Kelvin Probe Force Microscopy, and Conductive Atomic Force Microscopy. The effects of oxygen partial pressure during the film deposition are also investigated. The results show that high resistance state (HRS) is accompanied by the polarization switching and charges storage. By comparing the SPMs results from the same location, it is found that the oxygen partial pressure during film deposition is an important factor over the holes injection during the poling processes in the HRS. On the other hand, the low resistance state (LRS) may be dominated by the electrons injection. Based on these findings, the energy band diagrams in the Pt-tip/ZnO-film/Pt-bottom-electrode structure with the applications of the external biases are illustrated schematically. This study also proposes a more persuasive mechanism of RS in ZnO films.

Designing materials for application as electrodes in sodium-ion batteries may require the use of unconventional materials to realize acceptable reversible sodium insertion/extraction capabilities. To design new materials simple electrochemical methods need to be coupled with other techniques such as in situ x-ray diffraction (XRD) to correlate the influence of electrochemical performance on a parameter that can be modified, e.g., the crystal structure of the material. Here we use in situ synchrotron XRD data on Gd2TiO5-containing cells to show the minor changes in reflection positions during discharge/charge that illustrates minimal volume expansion and contraction due to insertion/extraction reactions. These small changes correlate to the Gd2TiO5 anode material in both lithium- and sodium-ion batteries showing reversible capacities of ∼45 and ∼23 mA h/g after 20 cycles, respectively. Analysis of sodium location in the crystal structure shows a preference for sodium in the smaller channels along the c axis direction during the first discharge before moving to the larger channels at the charged state. Therefore, in this work, in situ studies highlight minimal structural changes with respect to volume expansion during electrochemical cycling and illustrate where sodium ions locate within the Gd2TiO5 structure.

The enhanced photoresponse of commercial TiO2 (C-TiO2) nanoparticles in quantum dot (QD) sensitized solar cells, when doped with neodymium (Nd), is explored for graphene oxide–copper sulphide (GO–CuS) composite material as counter electrode. The modification of C-TiO2 and the preparation of GO–CuS were done by solid state and sonication methods respectively. The same were characterized by spectroscopy, microscopy, and cyclic voltammetry techniques. Results clearly indicate an enhanced conversion efficiency of ∼1.6 times over the undoped C-TiO2. UV and reflectance spectroscopy reveal that the dopants/defects/oxygen vacancies create midbands causing favorable surface electron states which act as electron traps suppressing recombination and the same is later detrapped leading to an efficient electron transfer. The retention of anatase phase, increase in particle size and decrease in band gap energy to visible range together with high surface area imparted by the GO to CuS in counter electrode facilitate good light harvesting and rapid enhanced electron transfer to redox system on doping. These findings make Nd–TiO2 a good photoanode material and GO–CuS a good counter electrode in QD solar cells.

Molecular dynamics simulations of compression deformation of $\left[ {11\bar 20} \right]$-textured 2-dimensional polycrystalline pure Mg, Mg–0.1 at.%Al, and Mg–1.0 at.%Al models were performed at 5 and 300 K. A $\left\{ {10\bar 11} \right\}$ twin nucleated before formation of a $\left\{ {10\bar 12} \right\}$ twin in the simulations at 5 K, while a $\left\{ {10\bar 11} \right\}$ twin nucleated after formation of a $\left\{ {10\bar 12} \right\}$ twin in the simulations at 300 K. The formation of a $\left\{ {10\bar 11} \right\}$ twin was the result of the glide of pyramidal 〈c + a〉 partial dislocations of ${1 \mathord{\left/ {\vphantom {1 6}} \right. \kern-\nulldelimiterspace} 6}\left\{ {10\bar 11} \right\}\left[ {\bar 2023} \right]$. $\left\{ {10\bar 11} \right\}$ twin formation was suppressed at the sites around the Al atoms because the strong Mg–Al bond suppresses atomic shuffling. However, formation was not suppressed at the sites away from the Al atoms because the effect of strong Mg–Al bond is short range. On the other hand, because $\left\{ {10\bar 12} \right\}$ twinning requires the simultaneous glide of zonal dislocations, Al inevitably suppressed $\left\{ {10\bar 12} \right\}$ twinning.

The carbon foams prepared by the thermo-foaming of dispersions of activated carbon (AC) powder of various average particle sizes (4.9 to 15 μm) in an aqueous sucrose resin were characterized. The stability of the wet foams increased with the decrease in the AC particle size as finer particles preferentially adsorbed on the air–resin interface. The particle agglomeration leading to the foam collapse was observed at lower AC powder to sucrose weight ratios with the finer powders. The cell size (0.33–2.34 mm), foam density (0.1151–0.2281 g/cm3), and compressive strength (0.16–2.77 MPa) of the carbon foams depend on the AC particle size as well as the AC powder to sucrose weight ratio. The thermal conductivity of the carbon foams (0.036–0.049 W m−1 K−1) was much lower than that of the vitreous carbon foams of similar densities. The foams were fire resistant and amenable to machining with the conventional machines and tool.

The work was intended to explore the effect of the widely available cationic polymer polyethylenimine (PEI) on small diameter poly(ɛ-caprolactone) (PCL) blood vessel grafts. PEI was blended with PCL and electrospun into nanofibrous vascular scaffolds. The morphologies, wettabilities, mechanical properties, and biological activities of the PCL/PEI electrospun nanofibers were investigated. It was found that by increasing the content of PEI to 5% within the scaffolds, the fiber diameters decreased from 469.7 ± 212.1 to 282.5 ± 107.1 nm, the water contact angle was reduced from 126.6 ± 1.1° to 27.6 ± 3.9°, while the Young's modulus increased from 2.0 ± 0.2 to 4.1 ± 0.1 MPa, the suture retention strength increased from 4.2 ± 0.4 to 6.1 ± 0.7 N, and the burst pressure increased from 801.2 ± 14.1 to 926.2 ± 22.8 mmHg. The in vitro evaluations demonstrated that the nanofibers containing 2% PEI promoted the attachment and proliferation of human umbilical vein endothelial cells (HUVECs).

Indentation-induced phase transformation processes were studied by in situ Raman imaging of the deformed contact region of silicon thin films, using a Raman spectroscopy-enhanced instrumented indentation technique (IIT). In situ Raman imaging was used to study the generation and evolution of the phase transformation of silicon while performing an IIT experiment analyzed to determine the average contact pressure and indentation strain. This is, to our knowledge, the first sequence of Raman images documenting the evolution of the strain fields and changes in the phase distributions of a material while conducting an indentation experiment. The reported in situ experiments provide insights into the transformation processes in silicon during indentation, confirming, and providing the experimental evidence for, some of the previous assumptions made on this subject. The developed Raman spectroscopy-enhanced IIT has shown its potential in advancing the understanding of deformation mechanisms and will provide a very useful tool in validating and refining contact models and related simulation studies.

A continuous nonflux inclusion-removal method, rotating gas bubble stirring, is used to purify Mg–10Gd–3Y–0.5Zr melt. The effects of rotating gas bubble stirring process parameters (Ar flow rate, time, and rotating speed) on purifying effectiveness, mechanical properties, and fracture behavior of sand-cast Mg–10Gd–3Y–0.5Zr alloy are studied. The results show that too high or too low Ar flow rate is unfavorable for inclusion-removal. The results also indicate that the high rotary speed of spraying gas is helpful to improve the inclusion-removal and mechanical properties. But when the melt is subjected to overtime gas bubbling treatment, the mechanical properties became poor again. Nonflux purification does not change the microstructure of Mg–10Gd–3Y–0.5Zr alloy. However, rotating gas bubble stirring has a certain effect on the fracture pattern of the alloy. In addition, the melt purifying mechanism of the gas bubble stirring treatment for the sand-cast alloy was discussed systematically.

Gd2TixZr2−xO7 (x = 0 to 2) pyrochlore was irradiated by 30 MeV C60 clusters, which provide an extremely high ionizing energy density. High-resolution transmission electron microscopy revealed a complex ion-track structure in Gd2Ti2O7 and Gd2TiZrO7, consisting of an amorphous core and a shell of a disordered, defect-fluorite structure. As compared with the irradiation by 1.5 GeV U ions with the highest energy loss, the track structure is consistent with tracks created by monoatomic swift heavy ions, but the diameters (with the entire diameter of 17 nm for Gd2Ti2O7 and 15 nm for Gd2TiZrO7) are significantly larger due to the much smaller velocity and higher energy density of the C60 ions. Ion tracks created by monoatomic ions are challenging to describe by HRTEM, as the boundary between disordered fluorite and pyrochlore matrix is less distinct. However, the C60 irradiation shows a clearly resolved ion track with completely crystalline, disordered, defect-fluorite structure around an amorphous core. Based on the distinct boundaries of the track morphology, inelastic thermal-spike calculations were used to describe the track size and extract critical energy densities for the interpretation of the complex core–shell morphologies for the different pyrochlore compositions.

This investigation reports mechanical properties of the exoskeleton of deep sea shrimp, Rimicaris exoculata, at temperatures ranging from 25 to 80 °C measured using nanoindentation experiments. The measured properties are compared with the corresponding shallow water shrimp (Pandalus platyceros) exoskeleton properties. Scanning electron microscopy suggests that both types of shrimp exoskeletons have the twisted plywood, Bouligand structure. However, they differ in the volume fraction and distribution of mineral content. The variations in the nanoindentation measured hardness values of the examined shrimp exoskeletons are found to be strongly correlated with the corresponding compositional difference between the two exoskeleton types. Nanoindentation creep strain rate measurements are performed to provide an assessment of the two types of exoskeleton for the role of proteins and minerals to cause difference in behavior and properties between the two shrimp species. The measured creep load–depth data are fitted with a viscoelastic creep function to find the creep compliance as a function of experimentally varying temperature and in the context of natural variations in mineral content.

Heat-resistant Al–8.5Fe–1.3V–1.7Si (wt%) aluminum alloy components were fabricated using selective laser melting (SLM). The as-built samples were examined in terms of density, chemical composition, surface morphologies, microstructures, and mechanical behavior. The results show that nearly full dense samples with the relative density of 99.3% can be produced. The chemical composition of the deposited material is close to that of the powder, presenting a limited aluminum loss and a low oxygen pickup. The SLM specimens consist of three typical zones: the fusion zone (FZ), the remelting border zone (RBZ), and the heat-affected zone (HAZ). Ultrafine continuous cellular α-Al networks are observed in the FZ. The HAZ exhibits fine rounded Al12(Fe,V)3Si particles (10–70 nm) distributed homogeneously in the α-Al matrix, while the rectangle-like AlmFe-type phase (m = 4.0–4.4) with 100–500 nm in size is preferably formed in the RBZ. The microhardness of the parts shows directional independent, with a mean value of 246 HV0.1.

Liquid film migration (LFM) in the fiber laser welded Inconel 617 joint was investigated. The results show that the LFM occurs in HAZ of the laser welded Inconel 617 joint. The element of Mo in the migrated region is slightly richer than that in the adjacent matrix. The diffusional coherency strain due to the lattice mismatch between the element of Mo and the matrix atom is the dominant factor contributing to the occurrence of LFM in HAZ of laser welded Inconel 617. The migration of the liquid film is promoted by the thin initial liquid film and the slow cooling rate in large heat input. LFM tends to occur on the grain boundary (GB) with the fine particles and the GB-resolidified particles are formed on the GB with the large particles. Liquation cracking is reduced in the welds with the high heat input and in the solution treatment condition by LFM (1100 °C/1 h).

Niobium is an important alloying element in steels. In the present work an effort has been made to investigate the effect of electropulsing on the niobium carbide (NbC) at an elevated temperature (800 °C). The results show that the electropulsing treatment can generate an evenly distributed NbC by decreasing the kinetics barriers for precipitation. It has been also found that a semitransformed pearlite structure forms in such a way that the grains are oriented toward a direction parallel to that of the electric current flow. Furthermore, the electropulsed sample benefits from refined grain size. This is thought to be due to the electropulse-enhanced nucleation rate. Tensile testing has been carried out to compare the properties of electropulsed sample with that of without electropulsing. The results show that the sample with treatment has greater yield strength and ultimate tensile stress while its elongation is only 1% less that of the unelectropulsed samples. The improved mechanical properties of the sample with pulsing are attributed to its finer grain sizes as well as the elimination of precipitation free zones caused by the electropulsing treatment.

This work focused on the modification of milled GaN powder. Successful attachment of a porphyrin derivative to a GaN powder was performed via in situ functionalization in the presence of phosphoric acid. The GaN powder was imaged using scanning electron microscopy and was found to be heterogeneous in nature, adopting no consistent geometry in the aggregates. The aqueous stability of the porphyrin used was observed in deionized water and a solution of phosphoric acid using ultraviolet–visible spectroscopy. Surface chemistry was characterized with x-ray photoelectron spectroscopy and infrared spectroscopy, which identified evidence of successful functionalization through the presence of characteristic peaks. The interface stability of the covalent bond between GaN and porphyrin was evaluated using fluorescence spectroscopy and demonstrated no leaching of dye in water solutions for 20 days.

In classical twinning theory, the K2 plane of $\left\{ {11\bar 22} \right\}\left\langle {11\bar 2\bar 3} \right\rangle$ twinning mode was predicted to be $\left\{ {11\bar 2\bar 4} \right\}$, with a twinning shear of ∼0.22 which was experimentally “confirmed”. However, these twinning elements cannot be reproduced or verified in atomistic simulations. The K2 plane in the simulations is always (0001), but this K2 plane would lead to a nominal twining shear of 1.26 which is unrealistically large. In this work, atomistic simulations were performed to investigate the migration of $\left\{ {11\bar 22} \right\}$ twin boundary in titanium (Ti). Shear and atomic shuffles for three different, reported K2 planes were analyzed in great detail, for the first time. The analyses show that ${K_2} = \{ 11\bar 2\bar 4\}$ leads to very complex shuffles despite the small twinning shear and is unfavorable. If ${K_2} = \{ 11\bar 2\bar 2\}$, only half of the parent atoms are involved in the shuffling, but the twinning shear is very large (0.96) and is also unfavorable. When K2 = (0001), the parent atoms are carried to twin positions partly by shear and partly by a simple shuffle. Because shuffling makes no contribution to the twinning shear, the actual twinning shear is 0.66, instead of 1.26. Thus, K2 = (0001) is the most favorable and the conflict between the simulation results and the classical twinning theory can be reconciled.

The microstructural evolution of type 347H heat-resistant austenitic steel during long-term aging at 700–900 °C was investigated by using a transmission microscope, a scanning electron microscope, and electron energy spectrum technology. The microstructural examination showed the typical micrographs of MX carbonitrides and M23C6 carbides after aging. The existence of the Z phase (NbCrN) at the grain boundaries during aging was identified. Meanwhile, the possible precipitation sequence of these particles was also confirmed. In the beginning of aging, fine Nb(C,N) precipitates first, then, M23C6 carbides precipitate along the grain boundaries. Finally, the Z phase is also observed at the grain boundaries. Moreover, the influence of isothermal holding temperature on the precipitation of MX carbonitrides and M23C6 carbides was discussed. The various microstructural characterizations showed that the M23C6 carbides and MX carbonitrides precipitate more easily with the increase of aging temperature. Furthermore, the number and the size of MX particles and M23C6 carbides increase when the isothermal holding time is prolonged.

The effect of adding nucleic acids to gold seeds during the growth stage of either nanospheres or nanorods was investigated using UV–Vis spectroscopy to reveal any oligonucleotide base or structure-specific effects on nanoparticle growth kinetics or plasmonic signatures. Spectral data indicate that the presence of DNA duplexes during seed aging drastically accelerated nanosphere growth while the addition of single-stranded polyadenine at any point during seed aging induces nanosphere aggregation. For seeds added to a gold nanorod growth solution, single-stranded polythymine induces a modest blue shift in the longitudinal peak wave length. Moreover, a particular sequence comprised of 50% thymine bases was found to induce a faster, more dramatic blue shift in the longitudinal peak wave length compared to any of the homopolymer incubation cases. Monomeric forms of the nucleic acids, however, do not yield discernable spectral differences in any of the gold suspensions studied.

Small specimen testing techniques have a long history in nuclear material research due to the limitations posed by nuclear facilities. The limited space in reactors and the fact that the samples are oftentimes radioactive in addition to the increasing need to obtain mechanical properties from ion beam irradiated samples require small specimen mechanical testing. With the application of modern focused ion beam sample preparation techniques and the enhancement of nanoindentation instruments, the size scale has been moved to even smaller scales and new geometries. Micrometer and even nanometer size samples are feasible, but raise the question of comparability to large scale properties for engineering applications. In this review, we summarize available small scale materials testing techniques and potential shortcomings based on examples from the literature, as well as introduce novel experimental approaches conducted using microcompression testing, microbend bar testing, and nanoindentation at ambient and nonambient conditions.