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Severe erosion wear is found on valve spools, which threatens the safety and reliability of these units. The use of the plasma beam spraying surfacing method can significantly improve the corrosion resistance and sealing performance of hydraulic valve spools, reduce material waste, and reduce maintenance costs. The effects of the co-addition of CeO2 and SiC particles on the morphology, surface cracks, microstructure, precipitated phases, and wear property of plasma-beam-sprayed Fe55-based coatings on 1025 steel were investigated using OM, EDS, ultra-deep field microscopy, and a wet sand rubber wheel friction tester, respectively. The dendrite exhibited a directional growth pattern perpendicular to the substrate and the transitional states of the microstructure with the co-addition of CeO2 and SiC particles. CeO2 or SiC reduced the liquid phase diffusion coefficient DL of Cr and C and resulted in a decrease in the G/R ratio. The dendrites changed into equiaxed grains. The main phase composition of the Fe55 welding layer was Cr7C3, γ-Fe. The martensite in the surfacing layer and the carbides formed Cr7C3, which can improve the hardness of the surfacing layer. The grain boundaries consisted mainly of a reticular eutectic structure. The uniform distribution of the Cr7C3 hard phase in the Fe55+1.5 wt% SiC+0.01 wt% CeO2 resulted in a uniformly worn surface. The sub-wear mechanisms during the friction process were micro-ploughing and micro-cutting. The hardness and toughness of Fe55+1.5 wt% SiC+0.01 wt% CeO2 were well-matched, avoiding excessive micro-cutting and microplastic deformation. A low content of CeO2 could lead to the formation of equiaxed grain and effectively improve the uniformity of the microstructure. The wear-resistant layer of Fe55+1.5 wt% SiC+0.01 wt% CeO2 can effectively improve the service life and long-term sealing performance of the valve spools. [ABSTRACT FROM AUTHOR]

The electrode configuration determines the thermophysical field during the electroslag remelting (ESR) process and affects the final microstructure of the ingot. In this work, ingot with a diameter of 400 mm was prepared with two electrode configuration modes of single power ESR process, namely one electrode (OE) and two series-connected electrodes (TSCE). Finite element simulation was employed to calculate the electromagnetic field, flow field and temperature field of the ESR system. The results show that the temperature of the slag pool and the metal pool of the TSCE process is lower and more uniform than that of the OE process. The calculated temperature distribution of the ingot could be indirectly verified from the shape of the metal pool by the experiment. The experimental results show that the depth of the metal pool in the OE ingot is about 160 mm, while the depth of the TSCE ingot is nearly 40 mm shallower than that of the OE ingot. Microstructural comparisons indicate that coarse eutectic carbides are formed in the center of the OE ingot, whereas more even eutectic carbides appear in the center of the TSCE ingot. In general, compared with the OE process, the TSCE process is preferred to remelt high speed steel ingots. [ABSTRACT FROM AUTHOR]

Activated sericite was prepared by thermal modification, acid activation and sodium modification, and it was characterized by X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC), N2 adsorption test, thermo-gravimetric analysis (TGA), nuclear magnetic resonance (NMR), and scanning electron microscope (SEM). The results indicated that the crystallinity of raw sericite decreased after thermal modification; the pores with sizes between 5 nm to 10 nm of thermal-modified sericite have collapsed and the surface area increased after thermal modification. The dissolving-out amount of Al3+ reached ca. 31 mg/g in the optimal processing conditions during acid activation; cation exchange capacity (CEC) of acid-treated sericite increased to 56.37 mmol/100 g meq/g after sodium modification compared with that of raw sericite (7.42 mmol/100 g). The activated sericite is a promising matrix for clay-polymer nanocomposites. [ABSTRACT FROM AUTHOR]

Functionally graded materials (FGMs) are characterized by continuous variation in their composition and structure with thickness or volume. Hence, the corresponding changes in the properties and functions of the FGMs can be investigated to create new materials. In this study, four-layered FGM specimens with three different compositions, i.e., Al 2 O 3 /(0, 5, 10, 15%) ZrO 2 , Al 2 O 3 /(0, 10, 20, 30%) ZrO 2 and Al 2 O 3 /(0, 15, 30, 45%) ZrO 2 , were designed. The ceramic specimens were hexagons whose sides were 11 mm long. Accordingly, 6061-T6 Al was used as a back plate. A ballistic test was conducted using 0.3″ armor-piercing bullets with an initial speed of 868 ± 15 m/s. Numerical simulation software, i.e., LS-DYNA, was employed to analyze stress transfer and the fracture of the FGM specimens under impact. The ballistic test showed that the Al 2 O 3 /(0, 5, 10, 15%) ZrO 2 FGM exhibited the best impact resistance performance. The investigation of microstructures through observation using a SEM did not show delamination in the FGM interlayer after impact. Furthermore, the abrasion between the ceramic and projectile increased. XRD analysis verified the phase transformation of ZrO 2 from the tetragonal phase to the monoclinic phase. This transition delayed crack growth and increased material toughness, thereby promoting the impact resistance performance of the FGMs. [ABSTRACT FROM AUTHOR]

Gradient concept is one of the solutions in advanced material design and structure control. Functionally graded materials (FGMs) are materials which change their composition, constitution or structure continuously along the direction of thickness; the property and function of those materials appear as changeable gradient characteristics. In this research, powder metallurgy method was used to make the functionally graded Al2O3-ZrO2 composite, which was backed with 6061-T6 aluminum alloy plate. For comparing purpose, we also make multilayer Al2O3-ZrO2 composite and pure Al2O3 composite under the same areal density. Based on NIJ IV standard, ballistic test was executed on the three kinds of samples by using 0.30? armor piercing projectile (AP). Finite element software ANSYS/LS-DYNA was also used to simulate stress distribution and fracture of these composites under impact. It was shown from ballistic test that FGM had the best impact resistant performance. Normally, multilayer ceramic structure will be fractured after impact because of the tensile wave caused by the interlayer. Through SEM observation, delamination was not found in the interlayer of FGM. This phenomenon reduced the tensile wave occurred in the interface between layers and delayed the crack propagation, resulting in a higher ballistic resistance capability structure. [ABSTRACT FROM AUTHOR]

The authors studied the solid-phase composition and morphology, pore structure, damage, and deterioration of microstructure, and nano-mechanical properties of cementitious materials in accelerated carbonation reaction. The solid-phase composition and morphology were investigated by X-ray diffraction (XRD), thermal gravimetric and differential scanning calorimetry (TG-DSC), and environmental scanning electron microscopy (ESEM). The characteristic of pore structure was obtained by mercury intrusion porosimetry (MIP) tests. Furthermore, the damage deterioration of microstructure was detected by X-ray computed tomography (XCT). Finally, the nano-mechanical properties were investigated by nanoindentation. These microstructure parameters have paved more precise way for the carbonation model. [ABSTRACT FROM AUTHOR]

High-entropy alloys have been proved to be potential candidate materials in the biomedical field due to their balanced mechanical properties and excellent biocompatibility. The effects of atomic ratios on the as-cast microstructural evolution, mechanical properties, and electrochemical property of TiZrTaNbSn high-entropy alloys were studied systematically. The crystal structure of TiZrTaNbSn high-entropy alloys is single BCC phase, and the microstructural evolution is based on atomic ratio. The dendric structure, peritectic structure, pseudo eutectic and equiaxed grain, which are associated with element segregation, can be obtained by non-equal atomic ratio. Ti30Zr20Ta20Nb20Sn10 alloy demonstrates a high compressive strength and fracture strain, which are 2,571.8 MPa and 12%, respectively, and the fracture behavior is quasi-cleavage faults. The Ti45Z35Ta5Nb5Sn10, Ti30Zr20Ta20Nb20Sn10 and Ti35Zr25Ta15Nb15Sn10 alloys show excellent corrosion resistance according to Nyquist diagram, polarization curves and corrosion morphology. Compared with TiZrTaNbSn alloy, the corrosion rate of Ti45Zr35Ta5Nb5Sn10 alloy increases by about 98.9%. It can be concluded that non-equal atomic ratios are effective for microstructure control and performance optimization. [ABSTRACT FROM AUTHOR]

• The TGA and MD simulations are used to explore the influence of Na 2 O on the volatilization of fluoride. • The mechanism of the effect of Na 2 O on melt volatilization is analyzed in detail. • Providing a substantial theoretical and experimental basis for the volatilization of fluoride. Volatilization of fluorides is a common phenomenon and an environmental concern in metallurgy, welding, glass, and other industries. In order to understand the effect of Na 2 O on the volatilization behavior of fluorides in molten slags, thermogravimetric analysis together with molecular dynamic (MD) simulation was employed in the present study. The MD simulation results are consistent with the thermogravimetric analysis (TGA). That is, the increase of Na 2 O promotes the volatilization of fluoride. Investigation of melt microstructure showed that the diffusion of Na+ plays a key role in the volatilization of fluoride. The main contributing microstructural factors to the diffusion coefficient of Na+ are the extent of polymerization in Si O and Ca F networks and the Na F clustering. Collectively, this research offered a thorough understanding of the microstructure and process of fluorine volatilization in molten slags. [ABSTRACT FROM AUTHOR]

• Titanium/steel laminated composites form a tooth-like interface. • Stress can induce interface element diffusion at room temperature. • Shear stress induce the formation of nanocrystalline/amorphous mixed interface. • Normal stress induce the formation of interfacial transition zone. Titanium/steel laminated composites form a tooth-like interface which is subjected to alternating shear/normal stresses during cold roll bonding process. Interfacial shear stress promotes atomic diffusion and gives birth to nano-grains, resulting in an interface mixed with nanocrystalline and amorphous region. Interfacial normal stress introduces high dislocation density, resulting in an interfacial transition zone. [ABSTRACT FROM AUTHOR]

In the present work, the effects of aging treatment on the microstructures of a TC18 alloy are studied. The influence of aging treatment on the tensile properties and failure mechanisms is systematically analyzed. It is found that the size and morphology of the primary α (αp) phases are insensitive to aging temperature and time. Furthermore, the aging temperature and time dramatically influence the precipitation of the secondary α (αs) phases. Massive αs phases precipitate and gradually coarsen, and finally weave together by increasing the aging temperature or extending the aging time. The variations in αp and αs phases induced by aging parameters also affect the mechanical properties. Both yield strength (YS) and ultimate tensile strength (UTS) first increase and then decrease by increasing the aging temperature and time, while ductility first decreases and then increases. There is an excellent balance between the strengths and ductility. When the aging temperature is changed from 450 to 550 °C, YS varies from 1238.6 to 1381.6 MPa, UTS varies from 1363.2 to 1516.8 MPa, and the moderate elongation ranges from 9.0% to 10.3%. These results reveal that the thickness of αs phases is responsible for material strengths, while the content of α phases can enhance material ductility. The ductile characteristics of the alloy with coarser αs phases are more obvious than those with thinner αs phases. Therefore, the aging treatment is helpful for the precipitation and homogeneous distribution of αs phases, which are essential for balancing the strengths and ductility of the studied Ti alloy. [ABSTRACT FROM AUTHOR]

Schematic illustration showing the evolution of network structure for the cured and uncured PCS. • The microstructure of SiC-based ceramic could be precisely tailored via thermal-oxidative curing. • Either excessive or insufficient cross-linking could cause the micropores to collapse. • PCS membranes had high thermal stability and oxidation resistance at 500 °C. • The optimized PCS membrane had excellent gas permeation properties and displayed high performances for H 2 /C 3 H 8 separations. In this study, the physicochemical properties and microstructural variations of polycarbosilane (PCS) were systematically investigated at curing temperatures of 150–350 °C and pyrolysis temperatures of 350–850 °C. Oxidative cross-linking remarkably enhanced the thermal stability of the PCS structure. Elemental composition and microstructure of the final ceramic material could be precisely tailored via the air curing process. Cross-linking by air curing that is either excessive or insufficient could cause the micropores of the resulting ceramic material to collapse or disappear. The most promising PCS-derived membranes, which were cured at 250 °C and then pyrolyzed at 750 °C, had high thermal stability and oxidation resistance at 500 °C in addition to excellent permeation properties: H 2 permeance of 1–2 × 10−6 mol/(m2 s Pa) at 500 °C with H 2 /N 2 selectivity of 31 and H 2 /C 3 H 8 selectivity of 1,740; and, CO 2 permeance of 1.8 × 10−6 mol/(m2 s Pa) at 27 °C with CO 2 /CH 4 selectivity of 40. Moreover, permeance and selectivity in an equimolar H 2 /C 3 H 8 mixture at 500 °C were approximately the same as those in single gases, suggesting the separation mechanism could be ascribed to molecular sieving. This is the first study to propose the concept of tailoring the microstructure of SiC-based membranes by controlling the curing process. [ABSTRACT FROM AUTHOR]

Macroscopic properties of sandstone are commonly attributed to the degradation of its microstructure during heating treatment processes. However, few previous studies have focused on comprehensive observations on how the microstructure of sandstone changes with temperature. In this study, a kind of sandstone containing quartz, albite, calcite, and laumontite (little), was collected from Linyi (Shandong Province, China) to observe the microstructure degradation changes with temperature by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and thermo-gravimetric analyses (TGA). Firstly, 10 groups of sandstone samples were heated from 25 °C to 900 °C. Then, some core micro-parameters including lattice constant, full width at half maximum (FWHM), micro-strain, dislocation density, TGA curve changes and failure characteristic of the mineral were analyzed comprehensively. Finally, the underlying mechanism causing the microscopic thermal damage at different temperature intervals was also discussed. The results showed that: (1) quartz, the framework component of this sandstone, underwent an α- to β-phase change over the temperature range from 400 °C to 600 °C. This phenomenon caused the lattice constant, micro-strain, dislocation density and TGA curve to decrease sharply during this interval, leading to the microstructure deterioration of sandstone; (2) calcite underwent a decomposition reaction between 600 °C and 800 °C, and resulted in the XRD pattern peak, lattice constant, micro-strain and TGA curve dropping continuously. It destroyed further the internal microstructure of sandstone and produced numerous inter-granular cracks around quartz crystals; (3) further examination found that the decomposition reactions of minerals presented non-synchronized characteristics due to the different sensitivities of minerals to temperature, which led to thermal stress, thermal fracturing of minerals, and thermal reactions happening in different temperature intervals. [ABSTRACT FROM AUTHOR]

Steel fiber-reinforced ultra-high-performance concrete (UHPC) is becoming an important type of concrete reinforcement. After mixing with the reinforced steel fibers, the UHPC has perfect flex resistance, shear strength, crack resistance, shock resistance, and anti-seepage. In this study, the influence of straight, corrugated, and hooked brass-coated steel fibers (BCSFs) on the microstructure, mechanical properties, and crack expansion mechanism of ultra-high-performance concrete (UHPC) with varying content of 1–6 wt.% under different curing times were investigated. Field emission scanning electron microscopy and energy dispersive X-ray spectrometry were employed to characterize the microstructure of the BCSF-reinforced UHPC mix specimens. X-ray computed tomography was employed to determine the porosity of the BCSF-reinforced UHPC mix specimens. The obtained results indicate the flexural strength and compressive strength of BCSF-reinforced UHPC mix specimens are enhanced, along with increasing the content of BCSFs reinforcement with different shapes (straight, corrugated, and hooked). The embedded BCSFs play a major role in the adhesive property and stress transfer of the BCSFs–UHPC matrix interface. Different from many studies, the flexural strength of mix UHPC with straight BCSFs is higher than those with corrugated and hooked BCSFs. However, the compressive strength of UHPC with corrugated BCSFs is higher than those with straight and hooked BCSFs. The flexural strength of mix UHPC with 6 wt.% straight BCSFs at 28 days reaches the maximum value of 26.2 MPa, and the compressive strength of UHPC with 6 wt.% corrugated BCSFs at 28 days reaches the maximum value of 142.3 MPa. With the increase in straight BCSF content from 1 wt.% to 6 wt.%, the porosity in mix UHPC reduces gradually from 18.4% to 8.3%. The length of average crack spacing is dependent on the straight BCSF content. With the increase in straight BCSF content from 1 wt.% to 6 wt.%, the average crack length reduces gradually from 34.2 mm to 12.1 mm, and the average crack width reduces gradually from 0.78 mm to less than 0.1 mm. During crack extension, part of the energy in the UHPC mixture specimen with the 6 wt.% BCSF content flows into the crack tip region converted into the work dissipated during the bridging process. The crack propagation resistance of the UHPC mixture with straight BCSFs was improved compared with those with corrugated and hooked BCSFs. The bond strength between the BCSFs and UHPC matrix was enhanced by using vibrational mixing, and the brass film coated on the BCSFs contributes to increase the flexural and compressive strength of the UHPC mixture. [ABSTRACT FROM AUTHOR]

During the automatic powder‐feeding process, the hollow granulated mold fluxes are easily broken due to insufficient granule strength, which leads to dust pollution and the deterioration of the properties of mold fluxes during the continuous casting. Herein, a drum‐type granule strength testing device, laser granule size analyzer, and scanning electron microscope are used to analyze the attrition mechanism of three kinds of hollow granulated mold fluxes and the effect of microstructure on the attrition mechanism. The results show that: 1) the result of the drum‐type granule strength test is in good agreement with the practical application effect of mold fluxes; 2) abrasion has dominated the breakage of three kinds of mold fluxes and the dust pollution is caused by the generation of a large number of granules with granule sizes ranging from 20 to 80 μm; 3) the uniform and dense surface film structure on the surface of mold flux effectively inhibits the abrasion and improves the granule strength of mold flux; and 4) the difference in granule size and solubility of different raw materials in the spray granulation process leads to the deposition of Na2CO3, binder, and carbon black on the surface to form the film structure. [ABSTRACT FROM AUTHOR]

In this article, the feasibility of preparing high-density polyethylene (HDPE)/copper (Cu) composites by submerged friction stir processing was investigated. The results showed that the Cu powders were dispersed with the flow of matrix in the action of stir. The surface layer of the composites was more uniform than core, and the advancing side was more homogenous than retreating side. The crystalline content of HDPE/Cu composites was higher than the processing materials without Cu powders. Compared with the matrix, the tensile strength of composites was lower, however, higher than that processing samples under the same processing parameters. The microhardness of composites was higher than either the matrix of the sample without Cu powders. [ABSTRACT FROM AUTHOR]

Sol-gel-derived organosilica membranes with different linking groups consisting of 2 carbon atoms (ethane, ethylene, and acetylene) were fabricated using bis(triethoxysilyl)ethane (BTESE), bis(triethoxysilyl)ethylene (BTESEthy), and bis(triethoxysilyl)acetylene (BTESA). No research group has ever proposed tailoring the microstructure and permeation properties of bridged organosilica membranes as a way to control the bond angles. In this study, however, we found that increases in the Si–O–Si and Si–C–C bond angles contributed to the formation of a loose and uniform structure, which was suggested by the blue shift of Si–O–Si and Si–C–C bonds in the FT-IR spectra. BTESA membranes featured a more open and accessible pore structure, which was suitable for the separation of C 3 H 6 /C 3 H 8. The present study provides a novel way to design the microstructure and permeation properties of organosilica membranes via controlling the bond angles in the network structure. Image 1 • Microstructure of organosilica membranes can be tailored via controlling the bond angles. • BTESA membrane shows great potential prospect in C 3 H 6 /C 3 H 8 separation. • This study provides a novel strategy to design the structure of membranes for specific separation system. [ABSTRACT FROM AUTHOR]

The mechanical properties of the geo-materials are greatly affected by the internal micro structure system. Multiscale modelling and analysis are considered as an effective tool for revealing the mechanical process. Aiming at the problems of the light intensity decrease and the uneven illumination, a Retinex scale optimized image enhancement algorithm is proposed, based on the light reflection model and Retinex theory. Based on the Retinex theory, a Monte-Carlo random geometric numerical model of the microstructure is established, with some soil specimens in South China as the study object. After that, three-axis consolidation process of soft soil materials are simulated, which are compared with the experimental data. The results showthat: the Retinex scale optimized image enhancement algorithm can accurately estimate the illumination component, eliminate the influence of the uneven illumination, improve the contrast of image and retain the details of the microstructure simultaneously. The random field model with this algorithm is simple and effective, the image becomes clearer, and the contrast ratio is improved, after using Retinex algorithm to enhance the CT image of rock and soil. The threshold segmentation of the enhanced image, and the fidelity between the enhanced image and the original image, are higher than that of the homomorphic filtering method and histogram equalization method, which explained that the algorithm could preserve the microstructure information of the micro image well. The result of numerical simulation is similar with the one obtained from conventional three axis consolidation test, which proves that the simulation result is reliable. [ABSTRACT FROM AUTHOR]

Abstract: In this work, dandelion-like NiCo2O4 mesoporous microspheres were uniformly assembled from slim nanowires via a large-scale and template-free method. The Brunauer–Emmett–Teller (BET) surface area of NiCo2O4 microspheres was determined to be about 35.2m2 g−1 with dominant pore diameter of 10.9nm and narrow size distribution of 8–20nm. Furthermore, the electrochemical properties of NiCo2O4 microspheres were evaluated by cycle voltammetric (CV) and galvanostatic charge–discharge (GCD) measurements. The results demonstrated that the NiCo2O4 microspheres exhibited high specific capacitance (372Fg−1 at 1Ag−1), good rate capability, and excellent cycling stability (88.3% retention after 2000 cycles). In principle, this synthetic approach could be extended for the fabrication of other microstructure materials for promising electrode candidates in energy storage devices. [Copyright &y& Elsevier]

The evolution of the physicochemical properties of allylhydridopolycarbosilane (AHPCS) was systematically investigated via DLS, TG, FTIR, XRD, and EDS. AHPCS-derived membranes were prepared by coating AHPCS sols onto porous substrates, which was then followed by pyrolysis at 300–800 °C. The pre-crosslinking by thermal curing significantly increased the colloidal sol size of AHPCS in toluene solutions, which effectively reduced penetration into substrates and enhanced the gas permeation. Furthermore, the pore structure of AHPCS-derived membranes could be precisely tailored by the pyrolysis temperatures, and the results indicated that the structure of membranes could be roughly classified into one of three types: a dense polymer structure, a loose transitional structure, and a denser ceramic structure (here, the term 'dense/denser' refers to the small/smaller pore structure, while the 'loose' refers to the large pore structure). AHPCS-derived membranes prepared at 300–800 °C under a N 2 flow displayed superior H 2 permeance of (0.2–5) × 10−6 mol/(m2 s Pa) at 200 °C with good H 2 /N 2 selectivity of 12–56. Ceramic SiC membranes prepared at 700 °C showed an attractive H 2 permeance of (2–4) × 10−6 mol (m2 s Pa)−1 at 200 °C with H 2 /N 2 selectivity of 16–22, H 2 /SF 6 selectivity higher than 10,000, and N 2 /SF 6 selectivity higher than 800. Moreover, the structure of the ceramic SiC membranes was highly stable with good oxidation resistance at 500 °C under air. AHPCS membranes prepared at 300–800 °C had different pore structures that exhibited a high level of quality and a variety of permeation properties that could provide many options for membrane materials over a wide range of applications. Schematic illustration for the evolution of the network structure for AHPCS pyrolyzed at different temperatures. Image 1 • The microstructures of the AHPCS-derived membranes were precisely tailored via control of the pyrolysis temperatures. • The pre-crosslinked AHPCS effectively reduced the penetration into substrates and enhanced the permeation. • Ceramic SiC membranes showed good oxidation resistance at 500 °C under air. • AHPCS membranes prepared at 300–800 °C with different pore structures have excellent gas permeation properties. [ABSTRACT FROM AUTHOR]