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Porous pure and Pd-doped SnO2 films are prepared using sol-gel synthesis with polystyrene (PS) microspheres as the template. Different characterizations are performed to analyze the microstructure and morphology of the films. The sensing performance of the films at various temperatures and hydrogen concentrations is investigated. Results show that high concentration of PS template significantly influences the continuity of films and the H2 sensing performance. The porous SnO2 film with 0.1 wt% PS microspheres exhibits the best performance. At 225 °C, the response magnitude of the porous 1 mol% Pd-doped SnO2 thin film to 1000 ppm H2 is 93.18, which is approximately 10.58 times of the pure sample.

Establishing an effective method to enhance the adhesion of mortar on recycled concrete aggregate (RCA) is key to the utilization of RCA. In this paper, a novel and simple approach for strengthening the mortar layer of RCA by treatment with a crystallizing agent (CA) was proposed, and the effects of different treatment regime on the density, water absorption, mineral composition, and microstructure of RCA were determined. Moreover, the performance of CA-treated RCA in recycled aggregate concrete (RAC) was investigated, and its mechanism of the treatment was explored at both the microscopic and macroscopic levels. The results showed that CA treatment significantly improved the overall performance of RCA by increasing the density and calcium silicate hydrate (C–S–H) content, which enhanced the properties of the new and old interfacial transition zones and enhanced the mechanical properties of the RAC. The improvements were attributed to the reaction of CA with calcium-rich hydration products in the mortar layer of RCA, which formed C–S–H precipitates. The newly-formed C–S–H filled the pores of RCA and blocked cracks, which improved the compactness of the RCA.

In this study, Laser Powder Bed Fusion (LPBF) Inconel 718 is subjected to various heat treatments, namely double aging, solid solution + double aging, and homogenization + solid-solution + double aging, to investigate the effect of heat treatment on room- and high-temperature tensile properties. The results show that all three heat treatments increase hardness and room-temperature tensile strength, but greatly reduce ductility. With an increase in tensile test temperature, the stress-induced Portevin-Le Chatelier (PLC) effect can effectively prevent the occurrence of oxidation at grain boundaries and maintain a certain ductility in the range of room temperature to 600 °C. However, when the temperature is 650 °C, the PLC effect disappears, resulting in a high-temperature embrittlement effect.

Based on sol-gel, multilayer porous Pd-WO3 composite thin films have been successfully prepared by utilizing a layer-by-layer deposition strategy. The crystal structure and microstructure were analyzed by various characterization methods. The sensing performance of the prepared films at different hydrogen concentrations and the temperature was studied. Results show that the performance of the hydrogen sensor can be improved greatly by the use of composite structure and soft template (Pluronic F127). The response performance of 1 mol% porous Pd-WO3 composite films was better than that of 2–10 mol% films. The porous Pd-WO3 composite films showed a high sensitivity (~346.5 times better than the sensitivity of pure WO3 films for 1000 ppm H2) and a fast response time (7 s) at the temperature of 250 °C. Porous Pd-WO3 composite films had good selectivity for hydrogen and stable sensing performance. The different response and recovery behavior of samples were contrasted and discussed to explain the effect of the special composite structure and porous structure on hydrogen sensing performance.

In this study, an Al-Mg-Sc-Zr alloy fabricated through selective laser melting (SLM) was subjected to a single-stage heat-treatment process and a two-stage heat-treatment process to determine the effect of heat treatment on the tensile properties and fatigue properties of the alloy at room temperature and high temperatures. The results indicated that heat treatment caused the precipitation of Al3(Sc, Zr), thus increasing the tensile strength. The dynamic strain aging of the SLM Al-Mg-Sc-Zr alloy disappeared as the tensile temperature increased. The alloy exhibited the highest tensile strength after it was subjected to the single-stage heat treatment at both room temperature and high temperatures owing to the precipitated phase distribution at the melting pool boundaries. However, fatigue resistance and high-temperature necking of the as-printed SLM Al-Mg-Sc-Zr alloy were problems that could not be resolved with the single-stage heat treatment. In the two-stage heat treatment, the precipitated phases exhibited a uniform distribution in the matrix, thereby reducing the high-temperature necking phenomenon. The two-stage heat treatment helped reduce the melting pool interface effect and strengthen the matrix, restricting the propagation of fatigue cracks and increasing the fatigue life of materials.

Influence of different drying techniques, namely, vacuum drying, oven drying (40 °C) and D-drying on the composition and microstructure of the calcium sulfoaluminate (CSA) cement was investigated in this study. The vacuum drying and oven drying were performed after the samples were immersed in acetone or ethanol. The results show that D-drying decomposes ettringite (AFt) greatly. Following solvent replacement, oven drying slightly decomposes AFt when compared with the vacuum dried sample, possibly due to the carbonation of AFt in the oven drying process. The decomposition of AFt due to D-drying and oven drying affects both the compositional and microstructural analysis of CSA hydrates. In addition, the soaking time of the samples in the solvents has no effect on the thermogravic (TG) analysis of the hydration products of CSA cement, which indicates that the CSA cement hydrates have no interaction with the solvents.

We used selective laser melting (SLM) Inconel 718 (coded AS) to carry out three heat treatment processes: (1) double aging (coded A), (2) solid solution + A (coded SA), (3) homogenization + SA (coded HSA) in order to investigate the effects of microstructure changes and tensile strength enhancement on erosion resistance. The as-SLM IN718 and three heat-treated specimens were subjected to clarify the effects of erosion-induced phase transformation on tensile mechanical properties. All heat-treated specimens showed better erosion resistance than as-SLM IN718 did at all impact angles. The as-SLM IN718 and the three heat-treated specimens produced new &gamma, &prime, phase or metal-oxide via particle erosion, which increased the surface hardness of the material. The thickness of the erosion affected zone is 200 &mu, m, which is the main cause of tensile embrittlement.

The addition of termiticides in concrete is gaining in popularity as method to prevent the degradation of concrete material and structure by the penetration and attack from termiticides, while the effect of which has not been systematically investigated yet. In this paper, the effects of five new generation termiticides on workability and hardened property of cementitious paste and mortars, in terms of minislump, compressive and flexural strength, were investigated. Moreover, the hydration characteristics, including microstructure and hydration products of the cementitious pastes with the termiticides were determined by X-ray diffraction test (XRD) and scanning electron microscopy (SEM). The results illustrated that the incorporation of the termiticides increased the workability while it decreased the compressive and flexural strengths of both paste and mortar. Moreover, the addition of termiticides did not affect the type and quantity of hydration products, especially for the calcium hydroxide. The exception was imidacloprid, in which it damaged the microstructure of cement paste. Based on the investigation, two termiticides, in terms of bifenthrin and chlorpyrifos, were identified as the termiticides with better performance in preparing termite-resistant concrete.

The novel selective laser melting (SLM) Al-Ni-Cu-Fe-Zr-Sc alloy has high temperature stability, but the segregation of the melting pool boundary limits its potential applications. Because conventional heat treatment with a solid solution at 530 °C is inappropriate for the SLM Al-Ni-Cu-Fe-Zr-Sc alloy, this study used hyper-high-temperature solid-solution treatment at three temperatures (560, 570, and 580 °C for 1 h) to investigate the evolution of the melting pool structure. An artificial aging treatment was applied at 175 °C for 6 h to investigate the precipitation mechanism. The results indicated that as-printed presented a bimodal microstructure consisting of a coarse-grained (CG) region and a fine-grained (FG) region. The hyper-high-temperature solid-solution treatment promoted the decomposition of the melting pool boundary and expansion of FG region. The FG region was composed of Ni-, Cu-, and Fe-rich equiaxed grains. After aging treatment, Al9Fe(Cu)Ni and Al3(Sc, Zr) nano-scale strengthening phases could be found in the FG region. The decomposition of the melting pool boundary, bimodal microstructure, and nano-scale phases can strengthen the matrix and increase hardness. In addition, the mechanism of element diffusion in melting pool was also explored to confirm that heat treatment can reduce material deterioration caused by boundary precipitation. These characteristics mitigate the disadvantages of the SLM Al-Ni-Cu-Fe-Zr-Sc alloy in terms of its strength directionality and establish its potential for use in aerospace applications.

The manufacturing of concrete using seawater provides a promising method to overcome shortages of fresh water and provides both economic and environmental benefits. However, the effects of superplasticiser on seawater-blended concrete, particularly from fresh to hardened properties, have not been thoroughly explored, which hinders the performance-based design of seawater-blended concrete. In this study, based on the water-film theory, the effects of two typical polycarboxylate superplasticisers (PCEs) on the hydrated characteristics and hardened properties of seawater-blended cement were systematically investigated. Water film thickness (WFT) was first analysed to determine the dispersion performance of the PCEs in seawater. The hydration heat was monitored using isothermal conduction calorimetry, and the products were analysed using X-ray diffraction, thermogravimetric analysis, and derivative thermogravimetry. Microstructures were investigated using scanning electron microscopy with energy-dispersive spectroscopy. In addition to compressive strength testing, the pore structures of the seawater-blended cementitious materials were analysed using mercury intrusion porosimetry. The results indicated that the incorporation of PCEs slightly increases the WFT in cement mixed with tap water and seawater. Furthermore, although seawater increased the hydration heat and densified the microstructures of the specimens with both PCEs, the hydration products were not influenced. Additionally, the compressive strength of cement with tap water and seawater decreased as a result of the increase in the proportion of capillary pores induced by incorporating PCEs.

The incorporation of silica fume provides the solution to solve the low silica content of municipal solid waste incinerator fly ash, which hinders its utilisation in manufacturing alkali-activated solid waste incinerator fly ash. This paper reported the effect of silica fume and sodium silicate nature on the hardened properties, including compressive strength, hydration product and microstructure of alkali-activated municipal solid waste incinerator fly ash. In addition to characterising the property of municipal fly ash, the effect of silica fume in compressive strength of alkali-activated municipal solid waste incinerator fly ash under different sodium silicate dosage and modulus was investigated and its hydration products were determined by XRD and SEM. The results demonstrated that adding silica fume significantly improved the compressive strength by promoting the formation of C–S–H hydration product. Moreover, a higher sodium silicate content and modulus resulted in a higher compressive strength. The concentration of leachable heavy metals from harden specimen with 10% SF specimen was significantly reduced to the value which is much lower than the recommendation from Chinese standards.

In this study, powder bed fusion Ti-6Al-4V alloy flake was subjected to heat treatment at 800 &deg, C for 4 h for inducing the complete transformation of the &alpha, &rsquo, phase into the &alpha, +&beta, phases. An erosion experiment with 450 &micro, m mean particle diameter of Al2O3 particles at a 90&deg, impact on both the as- powder bed fusion (PBF) Ti-6Al-4V and the 4-h 800 &deg, C heat-treated specimens to clarify the particle erosion-induced phase transformation behavior and its effect on mechanical properties. Particle erosion-induced phase transformation to the &alpha, phase was observed on both the as-PBF Ti-6Al-4V and the heat-treated specimens. It brought about a sequential formation from the surface to the bottom: (1) a surface softened zone, (2) a hardened zone, and (3) a hardness stabilization zone. The as-PBF Ti-6Al-4V was positively eroded by erosion particles, decreasing strength and ductility. In the case of the heat-treated specimens, we found decreased strength yet an increased ductility.

Al-Ni-Cu alloys are used in energy, automotive, and aerospace industries because of their excellent mechanical properties, corrosion resistance, and high-temperature stability. In this study, Al-Ni-Cu alloy powder was subjected to selective laser melting (SLM). The SLM Al-Ni-Cu alloy was manufactured using appropriate printing parameters, and its properties were investigated. The results revealed that the As-printed material exhibited a typical melting pool stack structure, with an ultimate tensile strength of 725 MPa but a high brittleness effect (low ductility). After traditional heat treatment, the melting pool structure did not completely disappear. The strengthening phase Al7Cu23Ni precipitated from the boundary of the melting pools, thus, the Al-Ni-Cu alloy maintained high strength (&gt, 500 MPa) and considerably increased ductility (&gt, 10%). The SLM Al-Ni-Cu alloy has considerable industrial application potential, therefore, increasing the heat treatment temperature or extending the heat treatment time in the future works can promote the decomposition of the melting pool boundary and solve the problem related to the aggregation behavior of the precipitation phase, thereby improving the fatigue life of the alloy.

Supersulfated cement (SSC) is a kind of environment-friendly and energy-saving cement, which is almost entirely made of industrial waste and could consume a lot of phosphogypsum (PG), which has great potential for industrial application. The calcination treatment at the temperature of 150 °C, 350 °C, 600 °C, 800 °C with calcination time of 0.5 h, 1 h, 1.5 h, 2 h is used to improve the performance of PG. The phase transformation of PG, the removal of soluble phosphorus impurities, and the hydration properties of SSC containing PG with or without modification are investigated, including the water requirement of normal consistency and setting time, the compressive strength, the pH value of pore solution and the microstructure performance of pastes. The relationship between these properties and calcination pretreatment processes are established as well. The results show that the calcination pretreatment of PG reduced the adverse effects of impurities in PG and changed the gypsum phase to prepare SSCs with higher performance in all aspects. While the modification effect varied with calcination temperature and calcination time, 90% of the setting time was shortened after calcination temperature of 350 °C for 2 h, which makes the PG-incorporated SSC meet the requirements of existing standard. And high temperature treatment showed the best modification effect on strength, especially after calcination at 600 °C for 2 h, both early and later strength was significantly increased, which was almost twice of the reference specimen. Besides, more formed hydration products and the denser microstructure were observed in the specimen with high temperature treated PG. Moreover, the slight decreases of 90-day compressive strength in some specimens were observed, which could be due to the carbonation of the specimen.

In this study, the physical triggered self-healing cementitious composites were prepared by mixing the epoxy resin based microcapsules with the cement, and its mechanical properties and microstructure were investigated as well. The effects of the different content of the microcapsules, proportion of prepressing stress, confining pressure and curing days on the mechanical parameters and microstructure of cementitious composite were carried out by the triaxial compression test and the mercury intrusion porosimetry (MIP) tests. The results indicated that the strength, cohesion, internal friction angle of specimens gradually decreased with an increase in microcapsules content or with an increasing of preloading stress, and the deterioration degree gradually increased with an increase in the microcapsule content or the preloading stress, but peak strain increased to vary degree. The mechanical parameters of the healed samples were repaired to different degrees compared with damaged samples. Microcapsules have significant and positive influences on the healing rates and recovery rates of mechanical properties, pore structure. The healing effect of cementitious materials was improved with increasing microcapsule content. However, the effects of microcapsules on microstructure of sound samples has to be considered.

Monodispersed SiO 2 /Y 2 O 3 :Eu 3+ core–shell submicrospheres were prepared through a simply homogeneous precipitation method. SEM, TEM, and Zetasizer analysis indicated the regular microstructures and uniform size distributions of obtained submicrospheres. FTIR spectra showed that the Y 2 O 3 :Eu 3+ shell had linked to the silica surface by forming a Si–O–Y bond. XRD patterns characterized the crystal structures of deposited Y 2 O 3 :Eu 3+ shell after heat treatment. Photoluminescence studies showed that the thickness of Y 2 O 3 :Eu 3+ shell had greatly affected the luminescent property of coated particles.

A simple approach to control the self-assembly of ZnS nanocrystals into well-defined, uniform, three-dimensional, micrometer-scale, solid ellipsoidal structures with rattle-type, multishelled, and hollow architectures is presented. There is no surfactant or small molecule to assist the self-assembly of the nanocrystals. A possible mechanism of the controlled self-assembly is proposed. The growth process can be divided into two stages: 1) the formation of ellipsoidal architectures via oriented aggregation, the growth kinetics of which is primarily attributed to the charge-charge, charge-dipole, and dipole-dipole interactions of preformed ZnS nanocrystals; and 2) Ostwald ripening, which results in multishelled, rattle-type, and hollow structures. This self-assembly concept is also applicable to other metal sulfides.

A series of Ag‐doped Tl2Ba2Ca2Cu3Oy superconducting oxides were prepared by a solid‐state reaction and the influence of Ag2O content, with a varying molar ratio which ranged from 0 to 1.0, was also investigated. The normal‐state resistance of the samples decreased with an increase in the content of Ag2O additive, while the critical superconducting temperatures of the Ag‐doped samples increased once the Ag2O content was increased. The doping of the silver oxide was indicated from the results of the x‐ray diffraction pattern to be favorable to the formation of the three CuO layers with a high‐Tc phase Tl2Ba2Ca2Cu3Oy. The diamagnetic property of the samples was also confirmed by the magnetic measurements to become enhanced by doping with silver oxide. The platelike grains of Tl2 Ba2CaCu2Oy phase were observed from scanning electron micrographs to be primarily present in the undoped sample, while the amount of the needlelike Tl2Ba2Ca2Cu3Oy grain increased with an increase in the doping amount of Ag2O.

In present study the influence of several factors on the texture of Bi-based superconductor prepared by powder in tube (PIT) method has been studied. The grain growth of 2212 and 2223 phases during the heat-treatment process leads to obvious improvement of their texture degrees. The texture of mother phase 2212 is well beneficial to improving these texture degrees. These results are analyzed based on the mechanism of the minimum interface energy texture formation that was raised in the early works.