Facile synthesis of MgO–Mg2SiO4 composite ceramics with high strength and low thermal conductivity

The recycling of solid waste is a win-win solution for humans and nature. For this purpose, magnesite tailings and silicon kerf waste were employed to prepare MgO–Mg₂SiO₄ composite ceramics by solid-state reaction synthesis in the present work. Then, effects of sintering temperature and raw material ratio on as-prepared ceramics were systematically studied. As-prepared ceramics showed improvement in their relative density (from 47.55%–68.12% to 90.96%–95.25%) and cold compressive strength (from 7.34–118.66 MPa to 303.39–546.65 MPa) with the increase in sintering temperature from 1300 to 1600 °C. In addition, it was found that Si promoted synthesis process of Mg₂SiO₄ phase through transient liquid phase sintering and Fe₂O₃ accelerated sintering process through activation sintering. Consequently, the presence of Mg₂SiO₄ phase effectively improved the density and strength of MgO–Mg₂SiO₄ composite ceramic, while reducing its thermal conductivity. This work provides a potential reutilization strategy for magnesite tailings, and as-prepared products are expected to be applied in fields of construction, metallurgy, and chemical industry.     

Characterization of precipitates formed in X7R 0603 BME-MLCC during sintering

In the current study two different batches of X7R-0603 BME-MLCCs displayed dissimilar electrical performance, despite having the same chemical composition, tape casting, and sintering conditions; with the only difference between them being the ore deposits where the raw materials were extracted from to synthesize the BaTiO₃. Specifically, they presented different electrical response to highly accelerated life tests (HALT). Although the chemical analysis of each slip showed the same composition, the trace elements of the BaTiO₃ sources could have acted as dopants or produced different secondary phases. A search for precipitates in the two samples was conducted by means of Scanning (SEM) and Transmission Electron Microscopy (TEM) techniques. SEM observations confirmed the presence of precipitates formed within the structure of the MLCCs exhibiting the greatest decrement in their electrical resistance results during the HALT. In order to further characterize the observed precipitates, samples were prepared by Focused Ion Beam (FIB) lift-out method, to make TEM characterization of specific precipitates feasible. TEM studies were performed on the precipitates to obtain electron diffraction patterns and complementary Energy Dispersive X-Ray Spectroscopy (EDXS) chemical analysis. Based on the crystal and chemical data obtained, it can be concluded that the precipitates are a hexagonal anhydrous silicate oxyapatite phase with a stoichiometry of Ca₃Y₁₆Si₁₀O₁₃, and lattice parameters of a = 0.9353 nm and c = 0.6970 nm; this phase was not found in the JCPDS data base. Differences in raw materials coming from different ore deposits can produce undesired precipitates that affect the electrical performance of MLCCs.     

SJ5型烧结车改进

介绍了铁路运输分公司SJ₅型烧结车的运行状态,阐述了牙,型烧结车的结构,分析了该车各部分存在的问题,针对存在的问题采取了改进措施使问题得以解决。     

Pelletization and sintering of New Zealand titanomagnetite ironsand

Direct reduction (DR) of iron ore with hydrogen is a potential route for near-zero CO₂ steelmaking, but vertical shaft DR reactors require that iron ore fines must first be pelletized. This study reports an investigation of the pelletization and subsequent sintering behaviour of titanomagnetite (TTM) ironsand, which is the main iron ore feedstock for New Zealand’s steel industry. Initially green pellets were bound with bentonite and carboxymethyl-cellulose (Peridur), using an average ironsand particle size of 65 µm. The compressive strength of these pellets after sintering at 1200 °C in air for 2 hr was measured to be 976 N, meeting the expected feedstock requirements for a shaft reactor. This strength was attributed to interparticle bonding arising from extensive recrystallisation of titanohematite grains from oxidation of TTM, as well as the formation of a liquid bonding phase due to melting and diffusion of the binders. Building on these results, alternative binders were then explored in order to lower the required sintering temperature. A combination of both organic and inorganic binders was found to deliver optimum performance, wherein carboxymethyl-cellulose based binders provided strength in the green pellets, whilst inorganic binders, such as calcium borate or ground glass, promoted high sintered strengths.     

Ion migration behavior and its interaction with sintering environment in cation conductor during flash sintering

Flash sintering has been reported in various ceramics. Nevertheless, anion and cation conductors exhibit different flash-sintering behaviors, and the interaction mechanism between the conductive species and the sintering environment has remained unclear. Herein, we report the flash-sintering phenomena of a typical cation conductor, Na₃Zr₂(SiO₄)₂(PO₄) with anode region surrounded by air and NaNO₃ environments. The results prove that the ionic behavior and joule heating distribution can be controlled by changing the electrode environment. Four possible scenarios describing the ion migration behavior and interaction with the environment are proposed for providing a guidance for controlling the ion interaction behavior during flash sintering.     

Enhanced thermoelectric properties of Na and Mg co−doped BiCuSeO

A series of Bi_0.97?xNa_0.03Mg_xCuSeO (0 ≤ x ≤ 0.12) was fabricated by a two?step solid?state reaction and spark plasma sintering (SPS), and the influence of Mg²⁺ doping on the thermoelectric properties of Bi_0.97Na_0.03CuSeO was systematically investigated. The SPS processed?Bi_0.97?xNa_0.03Mg_xCuSeO had a ZrSiCuAs?type tetragonal crystal structure (space group P4/nmm). The Mg²⁺ doping appreciably enhanced the electrical conductivity due to the increase in hole concentration. Furthermore, the Mg²⁺ doping increased the grain boundary areas and bulk porosity and induced the strain field and mass fluctuations, thereby reducing the phonon thermal conductivity. We significantly improved the thermoelectric performance of Bi_0.97?xNa_0.03Mg_xCuSeO (0 ≤ x ≤ 0.12) by enhancing the thermoelectric power factor and by reducing the thermal conductivity.     

提高唐钢烧结矿强度指标的试验研究

烧结矿强度对高炉冶炼的影响至关重要。通过正交试验,探索了不同因素不同水平对烧结矿强度的影响,从而得出最佳烧结参数,以提高烧结矿的强度。     

硫酸渣的开发利用

硫酸渣的开发利用与资源、环境、经济问题密切相关 ,具有较好的社会效益和经济效益 ,以及重大的现实意义。为此 ,提出了硫酸渣合理的开发利用途径     

Cobalt powdersintering industry (stone cutting diamond wheels): a study of environmental-biological monitoring, workplace improvement and health surveillance

This communication deals with an aspect of occupational hygiene in a factory producing granite cutting diamond wheels by sintering, in moulds, of fine cobalt powder. The factory has been studied between 1988 and 1991; the Department of Preventive and Occupational Medicine of the Local Sanitary Unit of Reggio Emilia has followed the evolution of the local exhaust ventilation equipment supplied by the employer in that period. At the same time, the following measurements and observations were carried out: (a) cobalt exposure by personal sampling, (b) airborne cobalt measurements by area sampling, (c) biological monitoring of cobalt in urine, (d) health surveillance.     

Microwave versus conventional sintering: Estimate of the apparent activation energy for densification of α-alumina and zinc oxide

A comparative study between the conventional and 2.45 GHz microwave multimode sintering behavior of insulator (α-Al₂O₃) and semi-conductive ceramic (ZnO) was systematically investigated. The apparent activation energy of nonisothermal sintering was determined by way of the Arrhenius plot of densification data at constant heating rates (CHR) and the concepts of Master Sintering Curves (MSCs), respectively. During microwave densification process, the apparent activation energy was about 90 kJ/mol less than the value for conventional sintering of Al₂O₃ applying these two estimation methods. However, an opposite result was obtained in the case of ZnO, although its densification process had been also accelerated by microwave as well as Al₂O₃. The significant differences in activation energy give a good proof of the difference in diffusion mechanism induced by the electromagnetic field underlying microwave sintering.