Acting mechanism of F,K,and Na in the solid phase sintering reaction of the Baiyunebo iron ore

The effect of F,K,and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis （DTA） and X-ray diffraction（XRD）.It has been identified that alkaline elements K and Na in the Baiyunebo ore instigate the formation of low melting point compounds Na2SiO3 and Na2O·Fe2O3 and the generation of molten state in the solid phase sintering.Element F in the Baiyunebo ore facilitates the formation of cuspidine compound 3CaO·2SiO2·CaF2 in the solid phase reaction.The cuspidine compound is kept in solid as one of the final products through the entire sintering process due to its high melting point.In the sintering process,CaF2and SiO2 react with CaO first and form 3CaO·2SiO2·CaF2 and 3CaO·2SiO2,so the formation of ferrites,Na2O·Fe2O3,and 2CaO·Fe2O3 is inhibited.

Fabrication of solid-phase-sintered Si C-based composites with short carbon fibers

Solid-phase-sintered Si C-based composites with short carbon fibers（Csf/SSi C） in concentrations ranging from 0 to 10wt% were prepared by pressureless sintering at 2100°C. The phase composition, microstructure, density, and flexural strength of the composites with different Csf contents were investigated. SEM micrographs showed that the Csf distributed in the SSi C matrix homogeneously with some gaps at the fiber/matrix interfaces. The densities of the composites decreased with increasing Csf content. However, the bending strength first increased and then decreased with increasing Csf content, reaching a maximum value of 390 MPa at a Csf content of 5wt%, which was 60 MPa higher than that of SSi C because of the pull-out strengthening mechanism. Notably, Csf was graphitized and damaged during the sintering process because of the high temperature and reaction with boron derived from the sintering additive B4C; this graphitization degraded the fiber strengthening effect.

Sintering kinetics of Ni_2FeSb powder alloys produced by mechanical milling

A ternary Ni2FeSb shape memory alloy was fabricated by powder metallurgy route. Sintering kinetics was estimated from dilatometry tests; whereas the microstructure and morphology of the powder and consolidated bulk samples were evaluated by XRD and SEM, respectively. Microhardness tests were performed on the surface of sintered samples. The results indicated that milling time has an effect on the shape and particle size as well as the homogeneity of the crystalline structures of the powders. Samples with longer milling time presented higher relative densities, better distribution of the elements on the alloy as well as the L21 and martensite phases, which will give the shape memory effect. The estimated activation energy values ranged from 109 to 282 kJ/mol at temperatures between 750 and 1273 K, indicating that sintering is controlled mainly by volume diffusion. Microhardness was improved by increasing the milling time and the heating rate.

Effect of La_2O_3 Addition on Hydration Properties of CaO Clinker

To obtain CaO clinker with high density, low po- rosity, and good hydration resistance, the effect of the La2 03 content on physical properties, such as sintering property and hydration resistance of CaO clinker was re- searched in this paper. Apparent porosity and bulk density were measured by Archimedes principle with kerosene as the medium. Two methods were used to test hydration resistance of CaO clinker. One was carried out in a hu- midity cabinet at 20℃ with 90% of relative humidity. Another was the boiling method. SEM and EDS charac- terization analyses of CaO clinker were pe.rformed to observe the microstructural information and the hydration mechanism was put forward. The results show that： （1） the specimen with 0.79 mass% of La2O3 addition has lower apparent porosity, and higher bulk density; （2） the hydration mass gain of CaO clinker with 0.79 mass% La2O3 addition is lower, which is less than 1% after 20 days ; （3） La2O3 mainly distributes in the grain boundary, attd a small amount of La203 dissolves in grains. The average grain size of CaO specimens with 0.79 mass% La2O3 addition sintered at 1 450℃, 1 550℃, and 1 650℃, is 44. 5 μm, 48. 6 μm, and 63. 5 μm , respectively; （4） solid solution is formed due to the similar ionic radius of La^3＋ and Ca^2＋, which promotes the sintering of CaO clinker and improves the hy- dration resistance simultaneously.

Sintering of solid waste generated in iron and steel manufacturing process in Shougang Jingtang

It is important to make full use of waste generated in the iron and steel manufacturing process for energy saving,emission reduction,low carbon production and a circular economy.Based on research on different kinds of industrial solid wastes from Shougang Jingtang,wastes have been optimized for use in sintering.At first,basic tests for all kinds of solid wastes that may be used in sintering were carried out,including chemical composition,calorific value of a fuel,holding time at high temperatures,the sintering pot test,etc.The results show that the appropriate solid waste ratios for current sintering conditions are：steel slag〈5%,scale 2.0%,environmental ash 2.0%,and cyclone ash 1.0%;blast furnace dry ash,sintering electric field ash,and steelmaking ash should not be circulated in sintering.As for the fuel structure,both coking ash and nut coke should be below 15%.By optimizing the addition of solid wastes,the damage of harmful elements to sintering and blast furnaces has been significantly reduced,which satisfies the demands for blast furnace materials and earns benefits.The utilization of solid wastes has made a contribution to the circular economy and sustainable development.

Phase evolution mechanism study and fabrication of PbMo_(6)S_(8) superconducting materials with two-step sintering process

PbMo6S 8 superconducting materials are considered to have great potential for practical applications at low temperatures and high fields due to their high upper critical field,low anisotropy,and low preparation cost.In this work,PbMo_(6)S_(8) bulks were prepared through a solid‐state sintering process using PbS,Mo,and MoS_(2) as raw materials.The phase evolution mechanism during the sintering of PbMo_(6)S_(8) was studied in detail.It was found that during sintering at 750℃ for 24 h,both the S and Pb atoms diffuse into the Mo and MoS_(2) particles,leading to the formation of the PbMo_(6)S_(8) phase.After sintering at 950℃ for 72 h,a high superconducting phase content was obtained in the bulk;however,numerous pores remained.Therefore,in order to obtain a higher density for the bulk,a two‐step sintering process was developed.Based on this technique,PbMo_(6)S_(8) bulks with a higher bulk density and a higher superconducting phase content were obtained.This study provides an effective method for the fabrication of high‐quality precursor powders,which can be the foundation for the future fabrication of PbMo_(6)S_(8) superconducting long wires or tapes for practical applications.