Three important low valent transition metal oxides were synthesized in supercritical methanol by using inorganic metal salts as precursors. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy were applied to analyze the composition, structure, and morphology of the products. Results showed that Cu2O, MoO2, and V2O3 were obtained successfully under a supercritical condition of 240 °C and 9.0 MPa. MoO2 and V2O3 displayed sphere-like morphology with average particle sizes of 20–40 and 20–50 nm, respectively. Cu2O particles displayed edge-truncated cubic morphology with a particle size of 2.5 μm. Formation mechanism proposed that high valent metal oxides (CuO, MoO3, and V2O5) were formed firstly in supercritical methanol by the decomposing of precursors and then reduced to target products by free hydroxyl anions. In addition, methanol performed important roles not only as a reaction medium but also as a reducing agent under supercritical fluid conditions.

Dissimilar materials of S235JR steel and AZ31B Mg alloy were welded by metal inert-gas arc welding. Interface characteristics and mechanical behavior of intermetallic compound layer at the Mg/steel interface in the welded joint were investigated. The intermetallic compound layer was mainly made up of FeAl phase, which exhibited unequal thickness at different positions in the interface. The growth coefficient of FeAl intermetallic compound layer could be expressed as K = K0 exp(−Q/RT) with Q of 195 kJ/mol. The kinetics of growth of the intermetallic compound layer indicated that its formation and growth were mainly driven by elements diffusion, and hence the thickness of the layer was dependent on peak temperature and reaction time which were determined by welding parameters. The FeAl intermetallic compound layer with high hardness was the weak zone where cracks inclined to derive and propagate during tensile testing. The fracture surfaces displayed both brittle and ductile features.

The microstructure formation and wear resistance of a superduplex stainless steel modified with the addition of 3 wt% boron produced by spray forming were investigated. Thermodynamic simulations were used as comparison basis and to explain the experimentally observed microstructure, which was composed by primary M2B-type borides, an austenitic-ferritic matrix, and eutectic M3B2-type borides. The predicted solidification sequence started with the precipitation of primary M2B boride, followed by ferrite/austenite formation and a final eutectic reaction resulting in M3B2 borides. A good correlation with the simulations and final microstructure was found. The abrasive wear resistance was investigated with the dry sand/rubber wheel test and the results indicated an outstanding performance, similar to the cobalt-based Stellite 1016 alloy. The excellent wear resistance resulted from the presence of a significant amount (about 35 vol%) of hard borides homogeneously dispersed in the microstructure, which was effective at increasing hardness and protecting the duplex matrix against abrasion.

In the paper, 2.5 vol% (TiB + TiC)/Ti composite has been fabricated by in situ casting route. 1-D forging and subsequent multistep rolling in (α + β) phase field are conducted on the as-cast composite and, accordingly, the matrix microstructure is significantly refined, and the distribution uniformity of reinforcements is greatly improved. The tensile properties of the composites with different processing states are tested at room temperature (RT), 600 and 700 °C. The results indicate that thermomechanical processing (TMP) can drastically improve strength and elongation of the as-cast composite both at RT and 600 °C. As tensile temperature increases to 700 °C, the UTSs of the composites gradually reduce while the elongations of the composites are enhanced remarkably after TMP. The degradation in UTS can be related to the matrix softening and interfacial debonding at 700 °C.

Titanium carbonitride (TiCN) is a popular hard coating for carbide cutting tools in various applications. This paper studied the influence of the carbon content and coating composition within TiCxN1−x coatings with regard to their adhesive strength on tungsten carbide substrate and subsequently, the performance of cutting tool in the dry turning of stainless steel. Among all the TiCxN1−x coatings, the TiCN coating has exhibited the highest adhesivity onto a substrate, followed by a TiC coating and lastly, a TiN coating. It was found that the adhesive strength of TiCN coating increased with the carbon content. The C/N ratio or C–N bond is a vital contributor to the adhesivity of the TiCxN1−x coating rather than the C or N atoms in the TiCxN1−x coating. It was found that the coating was delaminated before the exposure of substrate material. Hence, coating with higher adhesivity will promote longer tool life.

Layered materials are an actively pursued area of research for realizing highly scaled technologies involving both traditional device structures as well as new physics. Lately, non-equilibrium growth of 2D materials using molecular beam epitaxy (MBE) is gathering traction in the scientific community and here we aim to highlight one of its strengths, growth of abrupt heterostructures, and superlattices (SLs). In this work we present several of the firsts: first growth of MoTe2 by MBE, MoSe2 on Bi2Se3 SLs, transition metal dichalcogenide (TMD) SLs, and lateral junction between a quintuple atomic layer of Bi2Te3 and a triple atomic layer of MoTe2. Reflected high electron energy diffraction oscillations presented during the growth of TMD SLs strengthen our claim that ultrathin heterostructures with monolayer layer control is within reach.

The aim of this study was to obtain a tridimensional electrode with an even greater specific surface area (a s), using the electrodeposition of PbO2 films onto 45, 60, and 80 ppi RVC substrates applying different current densities. The kinetics and efficiency of decolorization of Reactive Blue 19 (RB19) dye achieved with the 60 ppi RVC/PbO2 were higher than obtained with a flat PbO2 electrode and 45 ppi RVC/PbO2, due not only to a greater electrochemically active area, but also especially due to the substantial increase in mass transfer caused by the turbulence generated by the porous matrix. It was found that the coating and the formation of β-PbO2 was only possible on the 60 ppi substrate applying 3.5 mA/cm2; in the case of the 80 ppi substrate, the uneven distribution of potential and current within the porous electrode did not allow establishment of suitable operational conditions that permitted complete and uniform coating of the substrate.

The fatigue crack growth (FCG) tests were performed on a Ni–17Mo–7Cr base superalloy before and after thermal exposure to investigate the influence of microstructural variation on the alloy's FCG behavior. It was observed that the original alloy consists of Ni matrix and MoC particles. When the alloy was aged at 1350 °C for 0.5 h, the MoC melts together with circumambient Ni matrix, forming a eutectic–like structure. The microstructural analysis shows that, for original alloy, the crack basically propagates in the matrix. When it encounters the particles, the crack meanders to avoid them, creating a linear da/dN–ΔK curve. As the crack approaches the eutectic-like structures within the aged alloy, however, it cuts through them but circumvents tiny particles within the structures, producing torturous crack paths and waved da/dN–ΔK curve. The aged alloy has a higher FCG resistance in contrast to original alloy.

Intermetallic composite has been expected to be one kind of high-performance wear material at elevated temperature due to its inherent high hardness and strong atomic bonds. This paper presents the wear behaviors under elevated temperature conditions of NiMo/Mo2Ni3Si intermetallic “in situ” composite. Metallographic observations were carried out with optical microscope and scanning electron microscope. Elevated-temperature wear tests were performed under pin-on-disc mode dry sliding conditions. Results shown that the relative wear resistant property of NiMo/Mo2Ni3Si alloys at 500 °C is over 7 times, and become higher at 550 °C compared with austenitic 1Cr18Ni9Ti stainless steel. The effect of temperature and applied load on elevated-temperature wear resistance of alloy was evaluated. The corresponding wear mechanism is also reported through examining the worn surface, subsurface, and wear debris of the NiMo/Mo2Ni3Si intermetallic alloys which is found to be soft abrasive wear.

A congruent melting compound LiNaV2O6 has been synthesized by high-temperature solution reaction and it has been grown with sizes up to 11 × 6 × 2 mm3 by the top-seeded growth method for the first time. LiNaV2O6 crystallizes in the monoclinic system with space group C2/c, with a = 10.184(2) Å, b = 9.067(2) Å, c = 5.8324(11) Å, β = 108.965(14)°. UV–Vis–NIR diffuse reflectance spectrum of LiNaV2O6 shows that it has a wide transmittance range from 385 to 2500 nm. The ab initio calculations show that the birefringence of LiNaV2O6 is 0.136 at 589.3 nm. Therefore, LiNaV2O6 may be a new birefringent material. Based on the analysis of the relationship between crystal structure and linear optical properties, it is found that the large birefringence is attributed to the particular arrangement of V–O anionic groups.

Mo2Ni3Si–Al2O3 nanocomposite was synthesized using MoO3, Ni, Si, and Al as starting materials by mechanical alloying. The mechanically alloyed powders were consolidated by hot pressing. The morphology and structural evolution of composite powders were investigated by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The microstructure and mechanical properties of the consolidated products were studied in detail. The results showed that Mo2Ni3Si–Al2O3 composite was obtained after 10 h of milling. The reaction mechanism mechanically induced self propagating reaction. The mean grain size of Mo2Ni3Si and Al2O3 after milling for 20 h were 15.9 and 32.4 nm, respectively. The Mo2Ni3Si–Al2O3 composite powders are stable during an annealing at 1000 °C. After consolidation, Mo2Ni3Si–Al2O3 composite has a high density (96.3%) and fine-grain (microns and submicrometer range). The hardness, flexure strength, and fracture toughness of Mo2Ni3Si–Al2O3 composite are 13 GPa, 533 MPa, and 6.29 MPa·m1/2, respectively. Meanwhile, the composite has higher strength at high temperature, and the strength remains stable up to 1000 °C (about 513 MPa).

The microstructures and mechanical properties of ternary (Ni75Al9V16) and multicomponent (Ni69Al9V9.5Nb3Ti1.5Co4Cr4) dual two-phase intermetallic alloys charged with C were investigated by scanning electron microscope, electron probe microscopic analyzer, x-ray diffraction, Vickers hardness, and tensile tests. Solid solubility limits of C in the dual two-phase microstructures were small, mostly less than 0.1 at.%. When C was charged exceeding the solid solubility limit, large-sized carbides were solidified with no structural coherency with the dual two-phase microstructure. Major transition metals constituting the carbides changed from Nb and Ti to V with increasing charged C content. This transition was correlated with the capability of the carbide formation. C dissolving in the dual two-phase microstructure enhanced hardness and flow strength through solid solution hardening without sacrificing tensile ductility. The formed carbides little contributed to strengthening, rather, contributed to softening through depleting constituent element V as well as alloying metals Nb, Ti, and Cr from the dual two-phase microstructures.

The effect of 0.5 wt% Mn addition on the microstructure and mechanical properties of cast Al–2Li–2Cu–0.8Mg–0.4Zn–0.2Zr (wt%) alloy was investigated. Results showed that the grain size of Mn-containing alloy was smaller than that of Mn-free alloy in both the as-cast and solution treated state. Al20Mn3Cu2 dispersoids were formed during solution treatment in the Mn-containing alloy. After aging at 175 °C for 32 h, a large volume fraction of coherent Al3Li/Al3(Li, Zr) particles were precipitated in both Mn-free and Mn-containing alloys, while more Guinier–Preston–Bagaratsky zones were observed in the Mn-free alloy. Mn addition improved the elongation significantly, which was 1.7% for Mn-free alloy and 3.3% for the alloy with 0.5 wt% Mn addition.

Statistical distribution of grid indentation data measured in multiphase materials can be significantly affected by the presence of an interface between adjacent materials. The influence of an interface on the distribution of measured indentation moduli was therefore characterized in model metal–metal, ceramic–ceramic, and metal-ceramic composites. The change of properties near the interface was simulated by finite element method and experimentally verified by indentation in proximity of the boundary between two phases with distinctly different mechanical properties varying the depth of penetration and the distance from the interface. Subsequently, the conditional probability of measuring near the interface was quantified by beta distribution function with parameters dependent on the size of the volume/area affected by the presence of the interface. Using this approach, the intrinsic properties of the individual materials were successfully extracted from the experimental grid indentation data.

Herein, Cu and Cu–Ge alloys with different stacking fault energies (SFEs) are prepared via rolling at room temperature (RTR) and via a combination of high-pressure torsion (HPT) and RTR (HPT + RTR). The x-ray diffraction measurements reveal that the grain size, dislocation density, and twin density vary with the strain and SFEs. The tensile tests indicate that the strength of materials with medium SFEs increases initially and then slightly declines, while the ductility is enhanced by increasing the strain via HPT. In contrast, for low-SFE materials, enhanced strength and improved ductility may be achieved simultaneously through increasing the strain to a high level. The variation of strength with respect to strain is primarily dependent on the solute concentration and SFE. The underlying mechanisms governing the effect of strain and SFE on the microstructures and mechanical properties of the metals are also discussed.

In this study, the effects of Ag variations on dynamic recrystallization (DRX), texture, and mechanical properties of ultrafine-grained Mg–3Al–1Zn alloys are investigated. The results suggest that Ag segregation and Al–Zn–Ag clusters form in the Mg matrix with Ag addition less than 1 wt%, which retard DRX and the growth of the DRXed grains. The resulting grain size decreases from 513 to 316 nm. As the Ag addition increases to 2 wt%, the Mg54Ag17 phase precipitates along the grain boundary, which plays an important role in restricting DRXed grain growth via grain boundary pinning effect. The resulting grain size is 375 nm with a bimodal grain size distribution. The extrusion texture of the investigated alloys is in fairly scattered orientation distribution. The weak basal texture and ultrafine grain size lead to the high yield asymmetry ratio. The Ag-containing extruded alloys exhibit an increase in the tensile and compressive properties. The strengthening mechanisms due to grain refinement, dislocations, solid solution, precipitates, solute clusters, and segregation are discussed.

The effects of different Sn contents on the microstructure and tensile properties of an in situ prepared Al–15% Mg2Si composite were investigated. Adding 5 wt% Sn not only reduced the average size of Mg2Si primary particles from ∼55 µm to ∼10 µm, but also increased the ultimate tensile strength and elongation values. Mg2Sn intermetallic was identified in Al–15% Mg2Si–5% Sn composite and the lowest disregistry was also found for $\left( {001} \right)_{{\rm{Mg}}_2 {\rm{Sn}}} {\parallel} \left( {001} \right)_{{\rm{Mg}}_{\rm{2}} {\rm{Si}}}$ , indicating that Mg2Sn can be a potent heterogeneous nucleation site for Mg2Si particles. Computer-aided cooling curve analysis revealed that Sn addition changes the solidification performance of the material by increasing both solidification time and recalescence undercooling and also reducing the growth temperature to some extent. The solidification behavior of the composite was also explained in terms of the presence of oxide bifilms in the liquid Al.

Texture and microstructure evolution during recrystallization of a heavily cold-rolled Ni9W alloy were investigated using x-ray diffraction and electron back-scattered diffraction. Brass, S and random orientations dominated the recrystallization process because the fractions of cube, Copper, and Goss orientations were low. Nearly all of the Brass and a part of the S orientation were consumed during recrystallization. Some of the S orientation was recrystallized grains, which grew during annealing and remained after the primary recrystallization. A large number of grains with other random orientations were formed as they had a significant size and fraction advantage during recrystallization. The evolution of microstructure and texture during recrystallization demonstrated that the cube grains did not have a size advantage compared with the noncube grains, which lead to the formation of a rough recrystallization cube texture in the Ni9W alloy after annealing.

In this article, we have explored the interface states that form between the channel of a monolayer MoS2 transistor and a high-κ gate dielectric. These interface states lead to large hysteresis in the drain current versus gate voltage characteristic or the so-called transfer characteristic of the transistor. By applying carefully designed pulses to the gate of the transistor, we show that it is possible to both understand the nature of the interface states and minimize the hysteresis, so that the transfer characteristic can be reliably used for subsequent extraction of material parameters such as mobility.

The friction and wear behaviors of reciprocatingly extruded AA 6061–SiC composites form the focal point of this study. To find the optimum way for refining the grains of the matrix, reciprocating extrusion (RE), as a deformation processes, is conducted and found to be feasible. Accordingly, RE has been applied on SiC particles reinforced AA 6061 matrix composite. Using the RE passes as a base, wear behaviors of the composites have been investigated at ambient temperature under dry and lubricated forms. Optical microscopy, transmission electron microscopy and scanning electron microscopy techniques were used to reveal the effect of the RE passes on the microstructure of the materials. As a result, it is found that there is a clear relationship between the weight loss, wear resistance and hardness of the samples. As the load and the number of passes increase, the weight loss in the samples increases. The worn surfaces of the reinforced composites have commonly adhesive and abrasive type of wear.