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Isothermal rolling is conducted at 1050 °C (α2 + B2 phase region) and 1100 °C (B2 phase region) for a spark plasma sintering (SPS)‐processed Ti‐22Al‐25Nb alloy. The effects of rolling temperature, pass, reduction per pass, and solution and aging on microstructure evolution, phase transformation, and tensile property at ambient temperature are systematically investigated. The results show that as the alloy is rolled at 1050 °C for 1 pass (P), the optimal tensile strength (TS) and the yield strength (YS) are 964.78 and 935.16 MPa, respectively, and the elongation (δ) reaches 23.65%. Then, followed by a subsequent solution and aging at 940 °C/30 min/water quenching (WQ) + 760 °C/24 h/air cooling (AC), it exhibits a decrease in mechanical properties. Moreover, a mixed fracture mechanism dominated by ductile fracture is shown for the as‐rolled alloy. However, after a solution and aging, it is transformed to a mixed fracture mechanism dominated by brittle fracture, which attributes to the void aggregation and the development of the discontinuous brittle α2 precipitates along B2 matrix grains during the solution and aging treatment. Finally, fracture models of the as‐rolled alloy and the solution and aging‐treated alloy are established. [ABSTRACT FROM AUTHOR]

The powder metallurgy (P/M) Ti-22Al-25Nb alloy obtained by spark plasma sintering (SPS) of Ti-22Al-25Nb prealloyed powders at 950 °C/80 MPa/10 min (α2 + B2 + O three-phase region) was adopted as the starting material to systematically investigate the evolution of microstructure, phase transition, B2 grain size uniformity and microhardness with solution temperature and holding time. The solution treatment was conducted at temperatures from 940 to 1100 °C (α2 + B2 + O, α2 + B2 and B2 phase regions) and holding times range of 10-120 min (10, 30, 60, and 120 min). After solution treatment, the microhardness of the alloy was measured. The results showed that the microstructure and microhardness of the alloy were closely related to the solution temperature and holding time. The B2 phase grain size and its uniformity increased with the increase in the solution temperature and holding time, and the microhardness decreased with the growth of the grains. The P/M Ti-22Al-25Nb alloy tested at 940 °C/10 min had the best performance, exhibiting three phases of α2 + B2 + O and a grain size of 43.57 μm. The microhardness was 359.52 ± 3.73 HV. In addition, the grain growth activation energy and grain growth index of different solution temperatures and holding times were obtained by linear fitting, and the relationship between the B2 grain size and the solution temperature and holding time was further established. [ABSTRACT FROM AUTHOR]

• Interlayer was prepared on the surface of W substrate using in-situ reduction. • Brittle intermetallic compound was completely avoided in the joint. • Thermal expansion coefficient of diffusion layer is between that of W and steel. • Incomplete coherent interface in diffusion layer improves the bonding strength. 90WNiFe alloy (W) and 30CrMnSiA steel (steel) were diffusion bonded using the porous NiFeWss interlayer, which was prepared on the surface of W substrate using electrolytic corrosion technology and showed high structural adaptability. The typical microstructure of joint is W/diffusion layer (NiFeW SS matrix + tiny W particle)/steel. Benefiting from the absence of brittle intermetallic compounds, the appropriate thermal expansion coefficient of (NiFeW SS matrix + W particle) diffusion layer and the incomplete coherent interface between NiFeW SS matrix and W particle in diffusion layer, the high property W/steel joint with tensile strength of 289 MPa and elongation of 8.14% was obtained. [ABSTRACT FROM AUTHOR]

A promising nickel cobaltite oxide (NiCoO) composite electrode material was successfully synthesized by a sol-gel method and followed by a simple sintering process. The microstructure and surface morphology of NiCoO modified by hexadecyltrimethylammonium bromide (CTAB) and polyvinyl alcohol were physically characterized by powder X-ray diffraction and scanning electron microscopy. Meanwhile, electrochemical performance was widely investigated in 2 M KOH aqueous electrolyte using cyclic voltammetry, galvanostatic charge-discharge test, and electrochemical impedance spectroscopy. The results show that evident porous microstructure was successfully fabricated by CTAB. The NiCoO controlled by CTAB exhibited highly specific capacitance of 1,440 F g at a current density of 5 mA cm. Remarkably, it still displays desirable cycle retention of 94.1 % over 1,000 cycle numbers at a current density of 20 mA cm. The excellent electrochemical performance suggests its potential application in electrode material for electrochemical capacitors. [ABSTRACT FROM AUTHOR]

A (TiNb)3(SiAl)C2 solid solution was designed and synthesized to improve the high-temperature oxidation resistance of Ti3(SiAl)C2. After doping with Nb, the oxidation resistance of Ti3(SiAl)C2 is improved. Its oxidation kinetics follows parabolic behavior up to 1300°C. The oxide scale formed on (TiNb)3(SiAl)C2 is thinner and smaller in grain size than that on Ti3(SiAl)C2 under the same oxidation condition. The beneficial effect of Nb doping on the oxidation resistance of Ti3(SiAl)C2 mainly results from the decreased concentration of oxygen vacancies and titanium interstitials in the rutile form of TiO2, and the inhibited generation of excessive voids in the oxide scale. [ABSTRACT FROM AUTHOR]

YH 2 bulk is regarded as the most potential metal hydride to be used as neutron moderator of microreactors serving as likely space nuclear power. In this work, YH 2- x monoliths are fabricated by spark plasma sintering (SPS) for the first time. Various properties of YH 2- x monoliths, including density, density distribution, density uniformity, hydrogen content, and attainable hydrogen density, are measured and calculated systematically. A hydrogen release process is accompanied by the densifying process during SPS. The effective densifying temperature interval is among 700–1000 °C. Steep hydrogen release occurs once the sintering temperature exceeds 900 °C. The microstructural evolution of YH 2- x monoliths is also related to the densifying process and the hydrogen release behaviors. Finally, a sintering process analysis of SPS for YH 2- x monoliths is discussed and illustrated in detail. • YH 2- x monoliths are fabricated by SPS for the first time. • The densifying and hydrogen release behaviors of sintering YH 2- x powders are found. • The sintering parameters for high hydrogen density YH 2- x monoliths are confirmed. • The critical temperature for sintering necks forming is observed to be 800 °C. • The microstructural evolution in a YH 2- x powders sintering process is revealed. [ABSTRACT FROM AUTHOR]

Abstract: One dimensional CoMoO4 nanorods with monoclinic crystal structure are successfully fabricated by a facile chemical co-precipitation method. The CoMoO4 nanorods synthesized at 70°C exhibit excellent supercapacitive performance. A high specific capacitance of 286Fg−1 is achieved at a current density of 5mAcm−2 and 97.5% of the initial specific capacitance is remained after 2000 cycles. The excellent stability is mainly due to the stable crystal structure and good structure stability of one dimension CoMoO4 nanorods. This study puts forward a new research strategy for developing and using of binary metal oxides based new electrode materials in electrochemical capacitors. [Copyright &y& Elsevier]

The microstructures of nanomaterials play important role in electrochemical and optical properties of nanomaterials. With wide applications of nanomaterials in electrochemiluminescence (ECL), how the microstructures of nanomaterials affect the ECL properties of nanomaterials have attracted increasing attentions. Deeper understanding of the relationship between microstructures of nanomaterials and ECL properties can not only facilitate better performances of nanomaterials in ECL applications, but also promote new emerging applications of nanomaterial-based ECL. In this review, recent progress on impact of microstructures of nanomaterials on ECL properties was introduced. The microstructures of nanomaterials include defect, morphology, surface ligand, valence state and spatial distribution of nanomaterial composition. The ECL properties involve ECL intensity and efficiency, wavelength and polarization of ECL emission as well as ECL triggering potential. In addition, the mechanisms of how microstructures of nanomaterials shape ECL properties were discussed. Finally, future perspectives in this field were provided. This review may inspire researchers in analytical chemistry and material science to design and apply nanomaterials with well-controlled microstructures for desired ECL performances in various applications. • Microstructures of nanomaterials play important role on ECL performances. • The effects of microstructures of nanomaterials on ECL properties are reviewed. • Challenges and perspectives on improving performances of nanomaterial-based ECL are discussed. [ABSTRACT FROM AUTHOR]

A powder metallurgy (P/M) Ti-22Al-25Nb (at%) alloy was prepared by spark plasma sintering of pre-alloyed powders at 1000 °C/80 MPa/10 min. The solution treatments of the P/M Ti-22Al-25Nb alloy were conducted at a temperature range of 940–1030 °C at 30 °C intervals and holding times of 10 min, 30 min, 60 min, and 120 min. The effects of the solution temperature and the holding time on the microstructure evolution, B2 grain growth behavior, phase transition, tensile mechanical properties, and fracture behavior of the P/M Ti-22Al-25Nb alloy were systematically evaluated using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction, and tensile tests. The results indicated that the microstructure and mechanical properties were closely linked to the solution temperature and the holding time. The effect of the holding time and the solution temperature on the B2 grain growth is well described by Beck's equation and Hillert's equation, respectively. The tensile tests showed that the tensile properties of the solution-treated P/M Ti-22Al-25Nb alloy were mainly affected by the number of O phases in the interior of the B2 grains and the phase transition degree of the α 2 phase at the grain boundary. The P/M Ti-22Al-25Nb alloy solution-treated at 940 °C/10 min exhibited the best mechanical properties at room temperature with a yield strength, tensile strength, and elongation of 867.8 MPa, 949.5 MPa, and 7.4%, respectively. A phase transition model of the α 2 phase was established. In addition, a tensile fracture model of the P/M Ti-22Al-25Nb alloy solution-treated under different conditions was established. • A powder metallurgy Ti-22Al-25Nb alloy was fabricated by spark plasma sintering. • Microstructure evolution and phase transition during solution treatment were studied. • B2 grain growth behavior of the solution-treated alloys was investigated. • A phase transition model of α 2 phase at the grain boundary was established. • Fracture mechanisms were analyzed and a fracture model was established. [ABSTRACT FROM AUTHOR]

• Thermal fatigue of cement-based materials in a mild temperature range. • Quantification of microcracks based on image processing and grayscale algorithm. • The double-edged effect of the w/c ratio on the deterioration. • Evolution of macro-properties and micro-structure under thermal cycling fatigue. • The establishment of the relationship between microcracks and Vickers hardness. Concrete structures in the atmosphere are continuously subjected to thermal cycle (TC) induced by varying environmental temperature. However, the influencing mechanism of thermal cycling fatigue on the mechanical properties and microstructure of cement-based materials has not been thoroughly documented. To address this issue, the relationship between the macro-properties and microstructure of cement paste under TC was analyzed using micro-properties measurement and quantitative microcrack evaluation. In this work, ordinary Poland cement pastes with three different water-to-cement (w/c) ratios (0.4, 0.5, and 0.6) were exposed to TC in the range of 5–45 °C. The mechanical properties, pore structures, and micromorphology of cement pastes after different cycle times were measured. The result indicated that as the number of cycles increased, TC negatively affected the macro-mechanical characteristics, pore structure, and micromorphology of cement pastes. Cement pastes with greater w/c ratios were more susceptible to TC-induced deterioration. In addition, thermal cycling fatigue caused the propagation of microcracks including crack width, length, and density. Thermal cycling fatigue also coarsened the pore structure of cement pastes, especially the large pores (i.e., diameter > 100 nm). The underlying damage mechanism caused by TC is the coupled actions of fluid flow, thermal deformation, and thermal fatigue. Moreover, a negative linear relationship was established between microcrack density and Vickers hardness of cement pastes. [ABSTRACT FROM AUTHOR]

A nanostructured α‑uranium surface layer with an average subgrain/grain size of 140 nm was obtained by using shot peening treatment (SPT). While, the nanostructures might be unstable in thermal condition due to dense lattice defects, high density of dislocations and ultrafine grains induced by severe plastic deformation. In this work, the thermal stability of the nanostructured surface layer was investigated using quasi-in situ electron backscatter diffraction (EBSD) after annealing treatments at temperatures ranging from 400 °C to 500 °C. Results show that the nanostructured surface layer has reasonably good thermal stability below 400 °C. Recrystallization and subsequent growth occurred when the temperature increased to 450 °C. The recrystallization nuclei are rooted in the initial nanostructured sites in the top surface layer and from dense dislocation walls in the subsurface consisting of high density of twin boundaries. At 450 °C, the exponent of recrystallization subsequent growth is determined to be 2.86, and the apparent activation energy value is 112.24 kJ/mol. Recrystallization occurs predominantly in a continuous manner. Furthermore, the evolution of dislocation density and grain size accounts for the decaying of surface mechanical properties. • A nanostructured α-uranium surface layer was resulted from SPT. • The activation energy value for recrystallization subsequent growth was calculated. • The recrystallization proceeded mainly by continuous recrystallization mechanism. • The surface microhardness was affected by dislocation density and grain size. [ABSTRACT FROM AUTHOR]

In order to solve the problem of waste concrete caused by demolition of old buildings, calcined nano-attapulgite (CNAT) was added into recycled aggregate concrete (RAC) to form nano-attapulgite recycled concrete. In this paper, the experiment was divided into two stages. Stage 1: The influence of activity of nano-attapulgite (NAT) which is calcined at different temperatures was analyzed by thermo-gravimetric analysis (TGA), scanning electron microscope (SEM) and X-ray diffraction (XRD) to find out the optimal activation temperature. Stage 2: The influence of different CNAT content and replacement rate of recycled coarse aggregate (RA) on the compressive strength of RAC were investigated, and the microstructure was analyzed by SEM, XRD and Barret-Joyner-Halenda (BJH) method. The results showed that when the calcination temperature is 500 °C, NAT has the highest activity; the compressive strength of RAC decreases gradually with the increase of replacement rate of RA. When the replacement rate of RA were 30 wt% and 50 wt% and the content of CNAT was 6 wt%, the compressive strength of concrete were the largest and the compressive strength is 13.2% and 16.1% higher than that without CNAT, respectively. Because of its filling effect, surface effect and pozzolanic activity, CNAT can fill the pores and cracks in the old mortar, new mortars and the interfacial transition zone (ITZ) of RAC. The harmful pores of RAC is refined, and the concrete is more dense. Above all, CNAT can increase the macroscopic mechanical properties of RAC by improving its microstructure effectively, which provides a theoretical basis for the further study of RAC. [ABSTRACT FROM AUTHOR]

• A gradient nanostructure on the surface of U-2 Nb alloy was fabricated by SPT. • The mean grain size of the top surface after SPT was about 63 nm. • Both α phase and γ phase in dual-phase U-2 Nb alloy were refined to nanograins. • The formation and mechanism of nanograins composed of α and γ phase were discussed. The microstructure changes and mechanical properties of dual-phase U-2 Nb alloy subjected to shot peening treatment (SPT) were investigated. SPT induced severe plastic deformation in the U-2 Nb alloy surface, and a gradient nanostructure was formed on the surface with the grain size ranging from nanocrystallization structure to coarse grains from the surface to the matrix. The results showed that both the α phase with an orthorhombic crystal structure and the γ phase with a body-centered cubic structure in the surface layer of the U-2 Nb alloy were refined to nanocrystals with an average nanocrystallization structure size of 63 nm. Due to the concentration of stress at the α/γ interface and grain size effect, the refinement of the α phase matrix occurred before γ phase. Furthermore, dislocation slipping caused by deformation, rather than deformation twinning, played a key role in the grain refinement of U-2 Nb alloy. Microhardness and tensile tests showed that both surface microhardness and tensile strength were improved after SPT. [ABSTRACT FROM AUTHOR]

The microstructure and micropillar compression responses of thin-walled Be–Al and Be–AlSi10Mg samples, produced by laser solid forming (LSF), were investigated. Both alloys resembled typical 3-D net-shaped structures. The Be–AlSi10Mg alloy exhibited coarser Be grains embedded in the refined Al net-like matrix owing to a broader solidification region. Owing to the multi-hardening by Si and Mg alloying, the yield strength of the system significantly increased from 150 MPa to 220 MPa. In addition, the failure mode changed from plastic fracture of the Al phase in Be–Al to brittle fracture of the Be phase in Be–AlSi10Mg during microcompression. Based on the theoretical calculation of the yield strength and fracture strength, grain size refinement by the non-uniform nucleation process was dominant factor affecting the Al matrix strength increment of Be–AlSi10Mg. Meanwhile, the critical resolved shear stress of Be was smaller than the ultimate strength of the Al phase strengthened by Si and Mg in the Be–AlSi10Mg alloy. Thus, the failure preferentially occurred in the Be phase rather than the Al phase. These results suggest that improving the fracture strength of the Be phase is important for obtaining high-performance Be–Al alloys after the strengthening of the Al phase by alloying additions and artificial aging measurements. [ABSTRACT FROM AUTHOR]