Microstructural analysis and bulk dielectric property analysis (real and imaginary permittivity at 95 GHz) were performed at temperatures ranging from 25 to 550 °C for ceramic composites comprising a hot-pressed aluminum nitride matrix (containing yttria and trace carbon as sintering additives) with molybdenum powder as a millimeter-wave radiation-absorbing additive. Loading percentages in the range of 0.25 vol% to 4.0 vol% Mo were characterized. For the temperature regime evaluated, the temperature-related changes in real and imaginary components of permittivity were found to be relatively modest compared with those driven by Mo loading. Energy-dispersive X-ray spectroscopic analysis of Mo grains and surrounding regions showed the presence of a mixed-phase layer, containing Mo2C, at the AlN–Mo interface. The Mo2C-containing mixed-phase layer, typically a few micrometers thick, surrounded the Mo grains. Further characterization of this mixed-phase layer is required to determine its contribution to the dielectric properties of the composite.

Glasses were prepared in systems based on two stoichiometric sulfides that were selected from Ga2S3, GeS2, and Sb2S3, with the incorporation of excess sulfur and CsCl. We investigated the fundamental properties, including glass transition, density, and optical absorption, and their variations with the incorporation of excess sulfur and CsCl into the pseudo two-component sulfide glasses. The incorporation of CsCl into the GeS2–Sb2S3 glasses shifted the absorption edge at the short-wavelength side to the long-wavelength direction, particularly for glasses with more amount of GeS2 than SbS3/2. In both cases of CsCl incorporation into the Ga2S3–GeS2 glass and Ga2S3–Sb2S3 glass systems, the absorption edges shifted to the short-wavelength direction regardless of the compositions. Ag photodoping behaviors were investigated for the bulk sulfide glasses with excess sulfur and CsCl. The results are discussed based on the diffusion of silver in the glass network that is modified by the incorporation.

Nano-sized TiN-reinforced Ti metal matrix composites were fabricated by powder metallurgical route, which includes high-energy ball milling pretreatment and subsequent hot-press sintering treatment. The phase composition and microstructure of the sintered samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Results showed that N2 was absorbed and solubilized into TiH2 by milling pretreatment, and TiN was formed during sintering process and was fine to a grain size of 20–100 nm. The final phase composition of the composites was αTi, βTi, and TiN with solution N in matrix. Mechanical tests showed that with increasing milling time, the hardness of the composites increased by 31, 58, 93, and 101% compared with pure Ti. The compressive strength initially increased and later decreased to 2440 and 2120 MPa when milled for 1.5 and 2 h, respectively.

The measured hardness of a metal crystal depends on a variety of length scales. Microstructural features, such as grain size and precipitate spacing, determine the intrinsic material length scale. Extrinsic (test) length scales, such as the indentation depth, lead to the indentation size effect (ISE), whereby it is typically found that smaller is stronger. Nix and Gao [J. Mech. Phys. Solids46, 411 (1998)] developed a widely used model for interpreting the ISE based on forest hardening in single crystalline pure metals. This work extends that model to consider the hardness of polycrystals and alloys, as well as introducing a finite limit to the hardness at very small extrinsic length scales. The resulting expressions are validated against data from the literature. It is shown that a reasonable estimate of the intrinsic material length scale can be extracted from a suite of hardness tests conducted across a range of indentation depths using spherical indenters of various radii.

Ti6Al4V alloy is commonly used in hip and knee replacements due to its high strength, ductility, wear, and corrosion resistance. Despite its optimal physical and chemical properties, Ti6Al4V based orthopedic implants have a limited lifetime of only 15–20 years. One of the main reasons for having limited lifetime is the suboptimal integration of Ti6Al4V implants with the juxtaposed bone tissue (osseointegration). To enhance osseointegration, and thus prolong the lifetime of orthopedic implants, Ti6Al4V implants surfaces were modified to have bioactive properties using electrochemical anodization process. In this work, oxide based micropit structures were fabricated on Ti6Al4V surfaces using a fluoride-free electrolyte consisting of NH4Cl in distilled water. Micropit structures were characterized for their surface morphology, crystallinity, and chemistry before and after high temperature crystallization heat treatment. Upon interaction of Ti6Al4V samples with simulated body fluid up to 30 days, enhanced calcium phosphate mineral deposition was observed on anodized surfaces.

A nanoparticle-based drug delivery system is first established by mesoporous silica encapsulating amino acid–intercalated layered double hydroxide (LDH) to construct nanocomposites AA-LDH@MS. The amino acids including phenylalanine (Phe) and histidine (His) with aromatic groups are intercalated into LDH as the cores Phe-LDH and His-LDH. These nanocomposites AA-LDH@MS display multispaces of the interlayer spaces of LDH and porous channels of mesoporous silica to load drugs. Moreover, amino acid molecules provide the interaction sites to improve effectively loading amounts of drugs. 5-Fluorouracil (5-FU) is used as the cargo molecules to observe the delivery in vitro. The results indicate that the maximum loading amounts of drugs are up to 392 mg/g at 60 °C for 12 h in the nanocomposite Phe-LDH@MS. All the nanocomposites exhibit the sustained release of 5-FU at pH 4 and pH 7.4. The Korsmeyer–Peppas model is used to fit the kinetic plot of the drug release in vitro, which concludes that 5-FU release from AA-LDH@MS belongs to Fickian diffusion.

The objective of the present work was to evaluate the behavior of osteogenesis of mesenchymal stem cells (MSCs) on a double-layer, protective, and bioactive hybrid coating sterilized by 3 different processes: steam autoclave, hydrogen peroxide plasma, and ethylene oxide. The hybrid coating was obtained from a sol consisting of the silane precursors tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), applied on a Ti6Al4V substrate. To promote bioactivity, hydroxyapatite (HA) particles were dispersed in a second coating (bioactive layer: TEOS/MTES + HA) applied on the first (TEOS/MTES). The sterilized coatings were evaluated by scanning electron microscopy, wettability, and micrometer roughness. The behavior of hydrolytic degradation was evaluated by the mass variation of the samples and the release of silicon by the technique of high-resolution atomic absorption spectrometry. All coatings presented morphological and superficial alterations after sterilization. Sterilization by ethylene oxide and hydrogen peroxide plasma intensified the hydrolytic degradation of the bioactive coating causing a greater release of silicon. The sterilized hybrid coatings did not show cytotoxicity to MSCs. Adhesion, viability, and osteogenic differentiation were favored on the sterilized coating of hydrogen peroxide plasma, which is opposite to what was observed for the ethylene oxide-sterilized coating.

Multifunctional nanoparticles are an emerging area of research, impacting numerous fields ranging from biomedical applications to energy. While initial core–shell structures consisted of similar materials, such as Au–Ag or CdTe–CdSe nanoparticles, recent work has expanded this line of investigation to include particles of dissimilar materials. However, there are several challenges when synthesizing dissimilar material systems. In this work, a method for doping the shell of an Au–ZnO nanosphere is demonstrated. Several metal dopants are investigated, including Cu, Ce, Er, Nd, Tm, and Yb. The ZnO shell is nucleated on the gold nanosphere core via an ascorbic acid–assisted growth, and the dopant is intercalated uniformly into the shell during the self-assembly phase of the shell formation. The doping and polycrystalline shell are confirmed using a series of qualitative and quantitative methods. This multi-material nanoparticle synthesis strategy opens the door for future applications in sensing, photocatalysis, and bioimaging.

Magnetic iron oxide nanoparticles (MIONPs) are particularly attractive in biosensor, antibacterial activity, targeted drug delivery, cell separation, magnetic resonance imaging tumor magnetic hyperthermia, and so on because of their particular properties including superparamagnetic behavior, low toxicity, biocompatibility, etc. Although many methods had been developed to produce MIONPs, some challenges such as severe agglomeration, serious oxidation, and irregular size are still faced in the synthesis of MIONPs. Thus, various strategies had been developed for the surface modification of MIONPs to improve the characteristics of them and obtain multifunctional MIONPs, which will widen the applicational scopes of them. Therefore, the processes, mechanisms, advances, advantages, and disadvantages of six main approaches for the synthesis of MIONPs; surface modification of MIONPs with inorganic materials, organic molecules, and polymer molecules; applications of MIONPs or modified MIONPs; the technical challenges of synthesizing MIONPs; and their limitations in biomedical applications were described in this review to provide the theoretical and technological guidance for their future applications.

Plasticity and fracture of materials at the nanoscale levels can deviate significantly from the same phenomena in bulk properties, which may have important implications if they are to be used in real-world engineering systems. Nanoscale metal–metal multilayered materials provide a model material system platform to understand plasticity and fracture based on dislocation interactions with microstructural features. Recently, there is a growing trend to understand the fracture of multilayered materials to see the interactions between the crack and multilayered interface through novel experimentation techniques. In this review, we will introduce the rationale, the current microfracture methods to test and analyze the multilayer fracture behavior and the challenges faced in performing them. Four examples of in situ fracture techniques are highlighted in this work through tensile testing of film on a substrate: microfracture clamped beam bending technique across the multilayers and delamination along the multilayered interface.

To study thermal desulfurization of pyrite (FeS2), we conducted in situ neutron diffraction experiments in the temperature range 298–1073 K. On heating, pyrite remained stable up to 773 K, at which it started to decompose into pyrrhotite (Fe1−xS) and S2 gas. Rietveld analysis of the neutron data from 298 to 773 K allowed determination of the thermal expansion coefficient of pyrite (space group Pa$\bar 3$) to be αV = 3.7456 × 10−5 K−1, which largely results from the expansion of the Fe–S bond. With further increase in temperature to 1073 K, all the pyrite transformed to pyrrhotite (Fe1−xS) at 873 K. Unit-cell parameters of Fe1−xS (space group P63/mmc) increase on heating and decrease on cooling. However, the rates in cell expansion are larger than those in contraction. This hysteresis behavior can be attributed to continuous desulfurization of pyrrhotite (i.e., x in Fe1−xS decreases) with increasing temperature until the stoichiometric troilite (FeS) was formed at 1073 K. On cooling, troilite underwent a magnetic transition to an orthorhombic structure (space group Pnma) between 473 and 573 K. In addition, using differential thermal analysis (DTA) and thermogravimetric analysis (TGA) implemented with a differential scanning calorimeter, we performed kinetic measurements of pyrite decomposition. Detailed peak profile and Arrhenius (k = A exp(−Ea/RT)) analyses yielded an activation energy Ea of 302.3 ± 28.6 kJ/mol (based on DTA data) or 302.5 ± 26.4 kJ/mol (based on TGA data) and a ln(A) of 35.3 ± 0.1.

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.

A novel tetragonal B2CO structure (tP16-B2CO), formed by strong covalent sp2–sp3 B–C and B–O bonds, was predicted with aid of an unbiased structure searching method. With the energy lower than those of previously proposed candidates, except oI16-B2CO, tP16-B2CO was identified as the thermodynamic metastable phase for B2CO compound. The elastic matrix and phonon dispersion spectra declare that tP16-B2CO is mechanically and dynamically stable. The electronic band structure calculation at ambient pressure and a series of high pressure has manifested the indirect semiconducting and band gap increases first and then decreases with pressure increases. The calculation of mechanical properties such as hardness and stress–strain relations of tP16 structure revealed its common hard nature with high hardness of 23.19 GPa and anisotropy with the max stress along [001] is far higher than that along [100].

In the present work, Mo was added to an Al–Si–Mg foundry alloy to study its influence on the evolution of dispersoids during various heat treatments. The microhardness and the elevated-temperature tensile properties and creep resistance were measured to evaluate the contribution of dispersoids. Results showed that the addition of Mo greatly promoted the formation of α-dispersoids. During solution treatment, the formation of α-dispersoids started after 8 h at 500 °C. At high temperature (540 °C), the coarsening of dispersoids with increasing time became predominant. The optimum condition of dispersoids can be reached by 520 °C/12 h or 500 °C/4 h + 540 °C/2 h, leading to the highest differences in microhardness between the Mo-containing alloy and base alloy. The tensile strengths were improved at both room temperature and elevated temperatures, while the elongation at elevated temperature was greatly increased. The creep resistance at elevated temperature is further enhanced due to the Mo addition.

Mechanical alloying (MA) followed by sintering has been one of the most widely adopted routes to produce nanocrystalline high-entropy alloys (HEAs). Enhanced solid solubility, room temperature processing, and homogenous alloy formation are the key benefits provided by MA. Spark plasma sintering has largely been used to obtain high-density HEA pellets from milled powders. However, there are many challenges associated with the production of HEAs using MA, which include contamination during milling and high propensity of oxidation. The present review provides a comprehensive understanding of various HEAs produced by MA so far, with the aim to bring out the governing aspects of phase evolution, thermal stability, and properties achieved. The limitations and challenges of the process are also critically assessed with a possible way forward. The paper also compares the results obtained from high-pressure torsion, another severe plastic deformation technique.

Considering the nonlocal small-scale effect and surface effect, we perform the size-dependent vibration analysis of carbon nanotube (CNT). The modified governing equations for CNT’s vibration behaviors are derived by using the nonlocal Euler–Bernoulli and Timoshenko beam models, together with the consideration of surface tension and surface elasticity. According to the numerical experiments, both small-scale effect and surface effect make a substantial difference. For flexural vibration, size effect for CNT’s vibration behaviors weakens with the increase of its diameter, but strengthens with the increase of the length–diameter ratio; for shear vibration with constant length–diameter ratio, a nonlinear correlation between size effect and CNT’s diameter exists, suggesting that there is a typical diameter for CNTs, which corresponds to the “strongest” size effect. In addition, the effects of elastic substrate modulus, temperature change, and axial preloading on the vibration behaviors and their size-dependence are analyzed, respectively.

Wearable electrochromic devices are considered as the essential components for the development of smart clothing with the intelligent sensing, actuating, and displaying functions. In this study, the electrochromic composite flexible membranes of polyaniline (PANI) and reduced graphene oxide (RGO) were fabricated by in situ polymerization of aniline monomer in the presence of RGO dispersion. The effects of RGO concentration on the morphology, chemical structure, crystallinity, and electrochromic behavior of the composite membranes were studied. Our experimental results show that the conductivity of PANI/RGO composite membrane increases with the increasing of RGO concentration from 0.1 to 0.25 wt%, and the highest conductivity is 3.57 S/cm. An improved electrochemical performance with good electrochromic cycle characteristic of the PANI/RGO composite can be obtained, which shows a wide color range from green to black compared with the PANI membrane that ranging from green to dark blue. This research provides a systematical investigation of flexible PANI-based electrochromic membrane, which has the potential application in the field of wearable electrochromic devices in the future.