Evolution Of Phase Composition Research Articles

Transparent surface crystallized aluminosilicate glasses with an ultrahigh crack resistance

Overcoming inherent brittleness and poor crack resistance (CR) of inorganic glasses is crucial to widen their applications. By optimizing the thermal treatment scenarios, a transparent surface crystallized aluminosilicate glass with an ultrahigh CR (75.1 N) and high hardness (7.1 GPa) is fabricated. Compared with the as-prepared glass with the stoichiometric β-quartz s.s. composition (Li2O·Al2O3·2.5SiO2), a near 14 times enhancement in CR is exhibited, which could be one of the reported glasses with the highest CR. The evolution of phase compositions and morphologies with modifying thermal treatment protocols was revealed through characterization. And the processing parameter dependence behaviors of mechanical performances for these crystallized glasses is mainly ascribed to the alterations in grain size, preferred orientation, or fraction of β-spodumene s.s. and β-quartz s.s. crystal phases in the surface crystallized layer. These findings provide new insights for developing new transparent materials with ultrahigh crack resistance to fulfill the applications such as electronic screens.

Valorizing inherent resources from waste streams for in-situ CO2 capture and sequestration in the steel industry

The imperative need for decarbonization within the energy-intensive steel industry, a pivotal sector for meeting global warming mitigation targets, underscores the significance of deploying cost-effective CO2 capture and sequestration (CCS) measures. The substantial external costs and resource consumption associated with traditional CCS methods present practical challenges. Here, we proposed a pragmatic strategy to integrate CCS into the steel industry through recycling inherent resources from steelmaking waste streams for in-situ CCS (ICCS). The composites prepared from blast furnace slag (BFS) and steel slag (SS) demonstrated the capacity to capture a maximum of 2.77 mol/kg of CO2 from the simulated flowing flue gas at 75 °C, and the energy required could be sourced from steelmaking waste heat. Comprehensive characterizations revealed the evolution of phase compositions and pore structures in different BFS/SS-incorporated composites, providing insights into accelerating the carbonation by elevating temperatures and SS dosages. Notably, ICCS strategy was validated to offer significant potential in CO2 emission reduction (up to −570.0 kg CO2e/t) normalized by compressive strength of the conventional construction materials. Overall, ICCS strategy can minimize the external resource consumption and additional units for implementing collaborative waste recycling in the steel industry with significant environmental benefits.

Microstructure and Physico-Mechanical Properties of Biocompatible Titanium Alloy Ti-39Nb-7Zr after Rotary Forging

The evolution of microstructure, phase composition and physico-mechanical properties of the biocompatible Ti-39Nb-7Zr alloy (wt.%) after severe plastic deformation by rotary forging (RF) was studied using various methods including light optical microscopy, scanning and transmission electron microscopies, X-ray diffraction, microindentation, tensile testing and investigation of thermophysical properties during continuous heating. The hot-rolled Ti-39Nb-7Zr with initial single β-phase structure is subjected to multi-pass RF at 450 °C with an accumulated degree of true deformation of 1.2, resulting in the formation of a fibrous β-grain structure with imperfect 500 nm subgrains characterized by an increased dislocation density. Additionally, nano-sized α-precipitates formed in the body and along the β-grain boundaries. These structural changes resulted in an increase in microhardness from 215 HV to 280 HV and contact modulus of elasticity from 70 GPa to 76 GPa. The combination of strength and ductility of Ti-39Nb-7Zr after RF approaches that of the widely used Ti-6Al-4V ELI alloy in medicine, however, Ti-39Nb-7Zr does not contain elements with limited biocompatibility and has a modulus of elasticity 1.5 times lower than Ti-6Al-4V ELI. The temperature dependences of physical properties (elastic modulus, heat capacity, thermal diffusivity) of the Ti-39Nb-7Zr alloy after RF are considered and sufficient thermal stability of the alloy up to 450 °C is demonstrated.

Low-Temperature Synthesis of Bi2S3 Hierarchical Microstructures via Co-Precipitation and Digestive Process in Aqueous Medium.

Bismuth sulfide (Bi2S3) nanostructures have gained significant attention in the fields of catalysis, optoelectronics, and biomedicine due to their unique physicochemical properties. This paper introduces a simple and cost-effective method for producing Bi2S3 microstructures at low temperatures (25 and 70 °C). These microstructures are formed by the hierarchical self-assembly of Bi2S3 nanoparticles, which are typically 15-40 nm in size. The nanoparticles are synthesized by the co-precipitation of thioglycolic acid, thioacetamide, and bismuth nitrate in water. The study delves into the phase composition and morphological evolution of the microstructures, concerning the chemical composition of the solution and the synthesis temperature. X-ray analysis has confirmed the formation of single-phase bismuthinite Bi2S3. The synthesis process generates primary building blocks in the form of 15-40 nm Bi2S3 nanocrystals, which then go through a hierarchical self-assembly process to produce a range of micrometer-sized structures. A scanning electron microscopy examination revealed that the primary nanoparticles self-assemble into quasi-1D worm-like nanostructures, which then self-assemble to create sponge-shaped microstructures. These structures subsequently self-organize and refine into either flower- or dandelion-like microstructures, mostly depending on the synthesis temperature and the chemistry of the digestion medium.

The Integrated Preparation of Porous Tungsten Gradient Materials with a Wide Porosity Range

Porous tungsten gradient materials with ordered gradient variations in pore size have significant application value in the field of vacuum electronic devices. This work combines tape casting and dealloying methods to achieve the integrated preparation of porous tungsten gradient materials with a wide range of controllable porosity. The study focused on the phase composition and microstructure evolution during the preparation of porous tungsten gradient materials. The results show that the tape casting process allows for the precise and controllable thickness of each layer of the porous tungsten materials and uniform composition structure, while the stepwise dealloying of Fe and Ti enables a wide range of controllable porosity for the porous tungsten gradient materials. PVB, after thermal decomposition, provides a carbon source for the in situ reaction to form W-Fe-C compounds, and the surface diffusion behavior of W-Fe-C compounds at high temperatures improves the stratification of the porous tungsten gradient materials. This work provides a design concept for the integrated preparation of porous metal gradient materials.

Evolution of phase composition of cordierite-sapphirine ceramics in terms of the temperature dependence of Young’s modulus and damping determined via the impulse excitation technique (IET)

Ceramics from the magnesia-alumina-silica (MAS) system are common products of the ceramic industry. The phase composition of these systems can be rather complex, especially when feldspar is added as a flux, and thus attempts to correlate the composition and structure of these ceramics to their properties are quite rare, especially when considerable amounts of glass phase and sapphirine appear after firing. In this paper an attempt is made to correlate, for a talc-kaolin-alumina-feldspar mixture resulting in cordierite-sapphirine ceramics after firing to 1250 °C, the resulting elastic properties (Young’s modulus), as determined via the impulse excitation technique (IET), with the phase composition, determined via X-ray diffraction (XRD). Moreover, it is shown how the evolution of the phase composition and microstructure is reflected in the temperature dependence of Young’s modulus and damping during heating-cooling cycles with maximum temperatures ranging from 1000 to 1250 °C.

Microwave dielectric properties and chemical bond of novel spinel-structure Zn3Ga2SnO8 ceramics

A novel low-εr Zn3Ga2SnO8 ceramic was prepared, and the phase composition and microstructural evolution were investigated. According to Rietveld refinement, TEM, and Raman spectroscopy, Zn3Ga2SnO8 ceramics had a cubic spinel structure in which Zn1 occupied the tetrahedral sites, and Zn2/Ga1/Sn1 occupied the octahedral sites. The relative density and packing fraction significantly influence the εr and Q × f of Zn3Ga2SnO8 ceramics, respectively. Meanwhile, the P–V–L theory indicates that the contribution rate of Sn–O bonds to bond ionicity is 29.2 %, and that of Ga–O bonds to lattice energy is 37.5 %. The Zn3Ga2SnO8 ceramics exhibit the best microwave dielectric properties (εr = 10.6, Q × f = 88,725 GHz, and τf = −25.1 ppm/°C) when sintered at 1320 °C. Given these advantages, Zn3Ga2SnO8 ceramic has certain potential applications in millimeter-wave technology.

Effects of multilayer structure on the high-speed dry-cutting performance of AlCrBN/AlCrN multilayer coatings

To investigate the effects of different structures on the cutting performance of AlCrBN/AlCrN multilayer coatings, AlCrBN/AlCrN coatings with different multilayer structures (single layer, 10 bilayers, and 20 bilayers corresponding to T1 coating, T10 coating, and T20 coating) were synthesized using multi-arc ion plating technology. Grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM) results showed that the coatings were mainly composed of fcc-(Cr, Al) N phases located on the (111) and (200) crystal planes. All coatings exhibited a good indentation adhesion to the substrates. The hardness of the T10 coating (32.6 GPa) and T20 coating (31.2 GPa) was significantly higher than that of the T1 coating (28.0 GPa). Annealing experiments show that no phase composition evolution was revealed at 800 °C. High-speed milling tests imply that the milling life of the T10 coating (13 m) and the T20 coating (10 m) was increased by 62.5% and 25.0% compared to the T1 coating (8 m), respectively. In high-speed dry turning tests, the T10 coated tool also showed the longest lifetime (16 mins), an improvement of 23.1% over T1 or T20 coated tools (13 mins). SEM analyses of wear coated tools indicated that a multilayer structure enhanced their resistance to abrasion and adhesion wear, and led to better cutting performance, probably because of their excellent mechanical properties and thermal stability.

Simulation of the Evolution of Phase Composition and Austenite Grain Size upon Multi-Pass Hot Deformation of Low-Alloy Steels

Simulation of the Evolution of Phase Composition and Austenite Grain Size upon Multi-Pass Hot Deformation of Low-Alloy Steels

Microstructure refinement and enhanced mechanical properties of wire arc additively manufactured RAFM steel via post heat treatments

Reduced activation ferritic/martensitic (RAFM) steel with high strength and neutron radiation damage resistance is deemed one of the promising structural materials for fusion blankets. In this study, RAFM steel tube was prepared through wire arc additive manufacturing, and the evolution of phase composition, microstructural features and mechanical properties during the as-built and heat treatment processes were investigated. The results show that the as-built state is predominantly composed of α-Fe, and the microstructure's morphology from bottom to top consists of alternating columnar grain regions, equiaxed coarse grain regions, and fine grain regions. Normalizing and tempering treatment eliminates the heterogeneous microstructure, resulting in the presence of M23C6 carbides enriched with Cr and W, as well as MX phases enriched with Ta and V. Partitioning heat treatment results in the formation of ultrafine martensitic, quenched martensite and bainitic microstructures. The mechanical properties of wire arc additively manufactured RAFM steel are influenced by variations in microstructure. The coarse-grained region formed in the as-built state represent weak links. Normalizing and tempering treatment reduces the strength while improving ductility. Partitioning heat-treated RAFM steel exhibited a high strength of 1.1 GPa and an elongation of approximately 10.9%. This study provides a method of combining additive manufacturing with heat treatment to enhance the strength and ductility of RAFM steel simultaneously.

Phase Composition and Phase Transformation of Additively Manufactured Nickel Alloy 718 AM Bench Artifacts

Additive manufacturing (AM) technologies offer unprecedented design flexibility but are limited by a lack of understanding of the material microstructure formed under their extreme and transient processing conditions and its subsequent transformation during post-build processing. As part of the 2022 AM Bench Challenge, sponsored by the National Institute of Standards and Technology, this study focuses on the phase composition and phase evolution of AM nickel alloy 718, a nickel-based superalloy, to provide benchmark data essential for the validation of computational models for microstructural predictions. We employed high-energy synchrotron X-ray diffraction, in situ synchrotron X-ray scattering, as well as high-resolution transmission electron microscopy for our analyses. The study uncovers critical aspects of the microstructure in its as-built state, its transformation during homogenization, and its phase evolution during subsequent aging heat treatment. Specifically, we identified secondary phases, monitored the dissolution and coarsening of microstructural elements, and observed the formation and stability of γ’ and γ” phases. The results provide the rigorous benchmark data required to understand the atomic and microstructural transformations of AM nickel alloy 718, thereby enhancing the reliability and applicability of AM models for predicting phase evolution and mechanical properties.

Influence of spraying power on microstructure, phase composition and nanomechanical properties of plasma-sprayed nanostructured Yb-silicate environmental barrier coatings

Currently, achieving high stability for environmental barrier coatings (EBCs) in service at higher operational temperatures (>1400 °C) remains a challenging issue. In our previous work, a nanostructured Yb-silicate coating was successfully fabricated, which could be a promising EBC candidate for CMC (Ceramics Matrix Composites) components protection at higher temperatures. However, there have been limited reports on the relationship between mechanical properties and spraying power for producing a nanostructured Yb-silicate coating. Therefore, this study delves into the microstructure, phase composition, and nanomechanical properties of nanostructured Yb-silicate coatings before and after heat treatment at different spraying powers. The results indicate that, due to the intricate interplay of microstructural and phase composition evolution, noticeable disparities in nanomechanical properties were observed in nanostructured Yb-silicate coatings before and after heat treatment. It is noted that the as-sprayed coating at 36 kW exhibits comparable nanomechanical properties to 45.5 kW, whereas the heat-treated coating demonstrates higher nanohardness and elastic modulus at 36 kW but greater damage tolerance at 45.5 kW. These findings offer a preliminary guidance for optimizing process parameters in nanostructured Yb-silicate coating's preparation, and laying the foundation for further researches.

Preparation of Surface Dispersed WO3/BiVO4 Heterojunction Arrays and Their Photoelectrochemical Performance for Water Splitting.

In this work, a surface dispersed heterojunction of BiVO4-nanoparticle@WO3-nanoflake was successfully prepared by hydrothermal combined with solvothermal method. We optimized the morphology of the WO3 nanoflakes and BiVO4 nanoparticles by controlling the synthesis conditions to get the uniform BiVO4 loaded on the surface of WO3 arrays. The phase composition and morphology evolution with different reaction precursors were investigated in detail. When used as photoanodes, the WO3/BiVO4 composite exhibits superior activity with photocurrent at 3.53 mA cm-2 for photoelectrochemical (PEC) water oxidation, which is twice that of pure WO3 photoanode. The superior surface dispersion structure of the BiVO4-nanoparticle@WO3-nanoflake heterojunction ensures a large effective heterojunction area and relieves the interfacial hole accumulation at the same time, which contributes to the improved photocurrents together with the stability of the WO3/BiVO4 photoanodes.

Impacts of substituting magnesium with zinc on crystallization behaviors in an aluminosilicate glass.

A series of zinc-magnesium mixed aluminosilicate glasses with the molar composition (1-r)MgO·rZnO·Al2O3·2.5SiO2, where r = 0.00, 0.25, 0.50, 0.65, 0.75, and 1.00, were fabricated to probe the effects of substitution of magnesium with zinc on crystallization behaviors. Based on the evolution of phase compositions as revealed by calorimetric behaviors and X-ray diffraction patterns, a series of transparent surface crystallized glasses ranging from high transparency for the pure Zn-end member to heavy translucency for the pure Mg-end member were fabricated through heat treatment at the first crystallization peak temperature for 20 min. With the substitution of Mg with Zn, the evolution of morphology unveiled by optical microscopy is ascribed to the alteration of crystal phases formed from the sole metastable Zn-β quartz solid solution to the coexistence of polycrystal phases containing Zn-β quartz solid solution, μ-cordierite, or α-cordierite. These findings are very helpful for optimizing the performance of crystallized aluminosilicate glasses.

Progressive low-temperature volatilization control: Efficient separation of arsenic and antimony from smelter dust

Given the high toxicity of arsenic (As) and the strategic importance of antimony (Sb), the separation of As and Sb has become a pivotal concern in the disposal of arsenic‑antimony flue dust and other arsenic‑antimony hazardous wastes. In this study, we propose a controlled roasting process employing anthracite and sulfuric acid additives to efficiently separate As and Sb at relatively low temperatures. Thermodynamic calculations revealed that the interactive reactions between arsenic and antimony oxides in conventional pyrometallurgical processes were the primary hindrance to their effective separation. However, the synergistic effect of anthracite and sulfuric acid not only disrupted the interactive reactions but also promoted the high-efficiency volatilization of As at low temperatures, thereby creating favorable conditions for the separation of As and Sb. Furthermore, a series of comparative experiments and comprehensive analyses regarding the evolution of phase composition, valence state, and morphology were conducted, revealing the underlying mechanisms of the effects of temperature and carbon addition. Through optimization, 91.24 % of As was successfully volatilized, while the volatilization efficiency of Sb was significantly reduced to 9.43 % under optimal conditions, involving a roasting temperature of 400 °C, anthracite addition of 1.6 %, sulfuric acid dosage of 0.135 mL/g, and a roasting duration of 3 h.

Development of industrial-grade γ-C2S binder from limestone and sandstone: Preparation, properties, and microstructure

This paper developed a cost-effective and highly carbonatable industrial-grade γ-C2S binder sintered from limestone and sandstone, aiming to advance the industrialization of γ-C2S binder in construction fields. The carbonation behavior of the industrial-grade γ-C2S binder, including the evolution of carbonation kinetics, compressive strength, phase composition, and microstructure with carbonation duration was studied. Results showed that a temperature of 1400 °C and limestone-to-sandstone mass ratio of 2.1 can be regarded as the optimal sintering regime, which can secure a relatively complete self-pulverization of industrial-grade γ-C2S binder. The industrial-grade γ-C2S binder had a milder carbonation reaction, which can reduce the evaporation of water and lead to 48% greater compressive strength, compared to that sintered from analytically pure reagents. During carbonation, the proportion of γ-C2S phase significantly decreased, while the proportions of CaCO3 and silica gel notably increased in the first 1 h, followed with a slight change in proportions of those phases with the carbonation further extending to 24 h. Similarly, the degree of carbonation rapidly increased to 36.3% in the first 1 h, followed with a slight increase to 43.7% at 24 h. The carbonation of industrial-grade γ-C2S, accompanied with the precipitation of CaCO3 on γ-C2S phase surface and the bond of silica gel among CaCO3 grains, contributed to the formation of nacre-bionic interlocking brick-mud microstructure. This led to the rapid enhancement of compressive strength with carbonation of industrial-grade γ-C2S.

Self-cleaning performance of autoclaved photocatalytic cement pastes: Insights into phase composition, microstructure and aluminum incorporation in C–S–H

This study attempts to comprehend mechanisms that enhance the photocatalytic properties of autoclaved cementitious pastes. The photocatalytic self-cleaning performance, phase composition, microstructure, optical properties, and silicate chain properties are characterized and analyzed. The results indicate that the silica source and alumina play significant roles in the evolution of phase composition and microstructure, which consequently affects the photocatalytic self-cleaning performance. The impacts of in-situ generated cement hydrates on the photocatalytic performance of cementitious materials are discussed for the first time, as well as the mechanisms governing the different morphologies of C–S–H crystals with the addition of different oxides. For the first time, the role of aluminum incorporation in the C–S–H network and major factors at different stages on the photocatalytic performance of cementitious materials are discussed. Finally, a systematic understanding of the photocatalytic properties of autoclaved cementitious materials is established. These results provide insights into the development of photocatalytic cementitious materials with tailored performances.

Evolution of microstructure and properties of Ba(Mg1/3Ta2/3)O3 thermal barrier material exposed to CMAS corrosion

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si2O8, Ba2MgSi2O7, BaTa2O6, Ba2Si4O10, etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m−1 · k−1 to 1.67 W m−1 · k−1. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10−6 K−1 to 10.95 × 10−6 K−1. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies.

The effect of low-energy high-current pulsed electron beam irradiation on the structure, phase composition and mechanical properties of Ni3Al and Ni3Al-TiC composites

Using scanning and transmission electron microscopy, X-ray diffraction, indentation and bending tests we studied the evolution of microstructure, phase composition and mechanical properties of TiC-free Ni3Al and Ni3Al-TiC composites (TiC content was 10 and 30 vol%) fabricated by self-propagating high-temperature synthesis (SHS) under pressure induced by low-energy high-current pulsed electron beam (LEHCEB) irradiation with the surface energy density of 8, 12 and 18 J/cm2. It was found that the irradiation results in the improvement of phase composition of the near-surface layer by way of the increase of yield of SHS reaction. LEHCEB irradiation enables formation of nanocomposite structure in the near-surface layer of Ni3Al-TiC composites with decreased grain size of Ni3Al matrix, refined TiC particles and increased volume fraction of TiC. This structure leads to the increase of microhardness but decrease of strength under bending. Two mechanisms of TiC particles refining are suggested. The effect of surface energy density on the manifestation degree of the found phenomena is discussed. The contribution of different hardening mechanisms to the overall hardening is considered.

Low electric field induced large electromechanical properties of BiFeO3-BaTiO3-based ceramics via phase composition modulation

The development of high-temperature lead-free piezoelectric ceramics with excellent electromechanical properties under low field remains a key challenge. A series of 0.995(xBiFeO3-(1-x)BaTiO3)-0.005Bi(Zn0.5Hf0.5)O3 ceramics were designed via modulating phase composition. The excellent electromechanical properties of d33⁎ = 511 pm/V (45 kV/cm) at room temperature and S = 0.476% (d33⁎ = 1190 pm/V, 40 kV/cm) at 120 ℃ were achieved in the x= 0.67 ceramic owing to the synergistic contribution of phase composition and domain evolution. The XRD results verify that the x= 0.67 ceramic is dominated by the pseudocubic phase. The PFM results in the x= 0.67 and 0.71 ceramics confirm that the domain structures consist of nanodomains with strong and weak piezoelectric responses. More importantly, the temperature and voltage-dependent domain evolution testify the nanodomains are easier to switch in the x= 0.67 ceramic. This work provides a strategy to optimize the electromechanical performance at the low field and a deeper understanding of BF-BT-based piezoceramics.