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Role of in-situ Formed Nonoxides Bonded Phases in Property Improvement of Alumina ULC Castables

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China's Refractories 2013年第1期22卷 17-20页

作者： YU Renhong DU Penghui zhou ningsheng LI Cuixia High Temperature Materials Institute Henan University of Science and Technology Sinosteel Refractory Co. Ltd

In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon, embedded atmosphere. Using tabular alumina as aggregates, tabular alumina, SiC powders, Si powders, calcium aluminate cenwnt, microsilica and ultrafine α-A12 03 powders as matrix, alumina based ultra low cement （ULC） castables were prepared. Influences of Si powder addition at O, 4% , 6% , 8% alul 10% （in nutss ） on regular properties, cold modulus of rupture （CMOR）, hot modulus of rupture （HMOR）, thermal shock resistance （TSR） and microstructure of the castables after carbonization were investigated. After incorporation of Si powders and carbon embedded heating, the in-situ mullite and nonoxide phases such as SiAION and SiC can be fornwd by oxidation, nitridation or carbomlzation reaction. HMOR and TSR of the castables with in-situ nonoxides bonding are obviously improted. After carbon embedded heating, the HMOR at 1 400 ℃ increases from 1.6 MPa to 8. 3 MPa, and the residual CMOR ratio after thermal shock increases from 64. 9% to 137. 9% when Si addition increases from 0 to 10%.

关键词： alumina based castables silicon powder carbon embedding carbonization nonoxide

Effects of Spherical Aggregates Addition on Properties of Al2O3-SiO2 System Castables

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China's Refractories 2017年第1期26卷 13-17页

作者： YU Renhong LIU Pengcheng zhou Xiwen zhou ningsheng YANG Dahui DONG Gaofeng High Temperature Materials Institute Henan University of Science and Technology Luoyang 471003 China Yanshi City Guangming Hi-Tech Refractories Products Co. Ltd. Luoyang 471000 China

Compared with traditional aggregates,spherical aggregates with high flowability,easy control of particle size distribution and favor of dense packing and so on,are expected to replace traditional aggregates as important raw materials for future high performance refractories. Therefore,investigation of effects of spherical aggregates addition on properties of refractories becomes very meaningful. Using A70 mullite traditional aggregates and A70 mullite spherical aggregates, bauxite homogenization powder,microsilica,and calcium aluminate cement as raw materials,different AlO-SiOsystem low cement castables were prepared by replacing conventional aggregates with spherical aggregates. The effect of spherical aggregates addition on workability and mechanical properties of castables after heated at different temperatures was researched,and microstructure of the specimen was analyzed by SEM. Compared with traditional irregularly shaped aggregates,spherical aggregates endow castables with better flowability and easy pump ability. By introduction of spherical aggregates into the castables,flowability and pumpability are significantly improved,and water addition and ball completely sunk time are reduced. The introduction of spherical aggregates is favorable to density and cold crushing strength of castables,but unfavorable to CMOR. The effect of spherical aggregates addition on HMOR at1 400 ℃ can be negligible. Microstructure analysis showsthat the boundary bonding between spherical aggregates and matrix is strong,similar to the traditional aggregates.

关键词： spherical aggregates alumina silica sys-tem castables mechanical properties

Effect of MgCl2 Solution Impregnation Process on Properties of Alumina-spinel Castables

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China's Refractories 2019年第4期28卷 22-25页

作者： MENG Qingxin zhou ningsheng CHENG Xiangyi BAI Xuedong LI Tong High Temperature Materials Institute Henan University of Science and Technology

In order to improve the properties of purging plugs and to prolong their service life,this work attempted to impregnate alumina-spinel castables for purging plugs in refining ladle with saturated magnesium chloride solution under *** being impregnated for the first time,the specimens were treated in two different ways:(1)dried at 110℃for 24 h;(2)heated at 600℃for 3 *** they were impregnated for the second *** specimens were heated at 1550℃for 3 h,then the cold properties and the high temperature properties were tested according to corresponding *** results were compared and *** results show that:after being impregnated,the specimen have both better cold properties and high temperature properties,the microstructure analysis result proves that it is attributed to in situ formed ***,because MgO produced by MgCl2-6H20 decomposing above 527℃can hydrate and destroy specimen microstructure,which can make the properties of specimens impregnated in the second way get *** comprehensive consideration,the first scheme way is more suitable.

关键词： impregnation alumina-spinel castables purging plug

Effect of Mild-calcined Coal Gangue Additionon Hot Strength and Refractoriness Under Loadof Ultra Low Cement Castablesin Al_2O_3-SiO_2 System

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China's Refractories 2011年第3期20卷 18-21页

作者： FENG Sisi zhou ningsheng High Temperature Materials Institute Henan University of Science and Technology Luoyang 471003 China

This work explored the way to improve hot modulus q/＇ rupture （HMOR） and refractoriness under load （RUL） by adding mild-calcined coal gangue （MCG） in Al2O3 -SiO2 ultra low cement （ULC） castables, making use of the in-situ effect of the MCG during heating-up. The influence of respective additions of 5%, 10% and 1.5% of the MCG powders calcined at 700℃ was investigated on HMOR at 1400 ℃ and RUL of the castables. With increased addition of the MCG, HMOR and RUL become significantly enhanced. At 10% of the MCG addition, HMOR reaches 3 MPa, as compared to 0. 3 MPa in the case of no MCG addition. RUL of the specimens dried at 110 ℃for 24 h can be increased by some 270 ℃ with 10% of the MCG addition. RUL 0.11 the specimens preheated at 1 500℃ for 3 h maintains the growth trend with the MCG addition increasing. The microstructure of the heated castable samples was investigated by means of SEM. The in-situ formed needle-like and interlaced mullite in the matrix is contributive to the tmprovement.

关键词： Coal gangue Hot modulus of rupture Refractoriness under load Ultra low cement castable Alumina - silica system

Effect of Raw Bauxite Addition on Thermal Behaviour of Ultra-low Cement Al_2O_3-SiO_2 Castables

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China's Refractories 2009年第3期18卷 15-17页

作者： HOU Wanguo zhou ningsheng High Temperature Materials Institute Henan University of Science and Technology Luoyang 471003 China

This work investigated the thermo-gravimetric （TG） change and explosion resistance of ultra-low cement Al2O3 - SiO2 castables added with 0, 5%, 10%, 15% and 20% of 474 μm raw bauxite powders containing 72.8% Al2O3, respectively. The castables were prepared using white fused alumina as aggregate, powders of white fused alumina, fused mullite,α-Al2O3 ultrafines, 3% CA cement and 5% microsilica as the matrix portion. TG change of the castables was investigated by a thermo-gravimetric analyzer for large size specimen. When the raw bauxite addition is less than 10%, the mass-losing behavior of the castables is similar to that without raw bauxite, tending to reach a constant mass around 400 ℃ , before which the mass-loss is mild and producing little destructive influence. With more than 10% raw bauxite addition, however, the mass-loss increases significantly, and the temperature to reach a constant mass increases to 600 ℃ or higher, unfavorable to structural stabilization. With the raw bauxite addition up to 20% , no negative influence on explosion resistance is found.

关键词： Raw bauxite Thermo-gravimetric change,Explosion resistance ULC castables Alumina silicasystem

Effect of Zircon Addition on Properties of Low Carbon AL_2O_3-C Refractories

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China's Refractories 2014年第1期23卷 38-42页

作者： ZHANG Feifei YU Renhong zhou ningsheng High Temperature Materials Institute Henan University of Science and Technology

Using tabular alumina as aggregate,tabular alumina fines,reactive alumina ultra-fines,aluminum powders,silicon powders,carbon black,flake graphite,B4 C and zircon fines as matrix,low carbon Al2O3-C refractories were *** of zircon powders additions （0,3%,5% and 7%,in mass,the same hereinafter） on properties,phase composition and microstructure were *** results show that the ZrO2-nitride can be in-situ formed through carbothermal reduction and nitridation in Al2O3-C *** the increase of zircon powder,the oxidation resistance of the Al2O3-C refractories improves obviously,the oxidized layer thickness decreases from 7.94 mm without zircon to 2.71 mm with 5% *** at 1 400 ℃ of the Al2O3-C refractories reaches the maximum 14.9 MPa when zircon addition is 5%.With the increase of zircon powder,the apparent porosity and bulk density change a little,CMOR and CCS increase.

关键词： carbothermal reduction and nitridation zircon alumina-carbon refractories zirconia-nitride oxidation resistance

The Future of the Refractory Industry,with a Chinese Perspective

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China's Refractories 2005年第4期14卷 3-7页

作者： Michel Rigaud zhou ningsheng YE Fangbao FIRE Ecole Polytechnique Mechanical Engineering Dept. University of Montreal Montreal Canada High Temperature Materials Institute Henan University of Science and Technology China High Temperature Ceramics Institute Zhengzhou University China

Globalization is a reality resulting in many changes in the refractory industry. In this paper some of the threats and opportunities, which are influencing the future prosperity of the refractory industry on a worldwide basis, are being evoked. Some key technical and management issues are underlined, in terms of adjusting the productivity-quality-cost to the customers requirements ; producing unshapes versus shapes; innovations supported by research; international profile for the import-export game; training and education. Consequences for China, who does play a dominant role due to the size of its internal market （ customers demand） and the magnitude of its production capability （including raw materials availability）, are being drawn.

关键词： Review Refractories industry Technology Management Market

Influence of Pore Forming Agent on Properties of Micro-pored CA_6-MA Material

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China's Refractories 2013年第2期22卷 24-28页

作者： LI Chunming zhou ningsheng BI Yubao High Temperature Materials Institute Henan University of Science and Technology

Micro-pored CA6 -MA lightweight material with CAM： MA mass ratio of 7：3 was prepared using Al（OH） 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite ＋ sweet potato starch as pore forming agent （PFA） with an addition of 10 mass%, 20 mass% and 30 mass%, respectively. The starting materials were dry mixed, wet co-milled in a ball mill for 1 h. slip cast into cylindrical specimens with a diameter of 60 ram. and then calcined at 1 450 ℃ for 3 h. With the increase of PFA addition,, apparent porosity increases, and bulk density decreases. The influence of different PFAs on properties of the micro-pored LW CAM -MA aggregate was investigated. The achieved CAM - MA, by adding 30% sweet potato starch, has a porosity of 76. 8%, bulk density of 0. 78 g · cm^ - 3 and median pore size of 1.90 μm.

关键词： micro-pored material calcium hexaluminate, spinel pore forming agent lightweight aggregate, refractory

Effect of ZrO_2-nitrides Composite Powder Addition on Oxidation Resistance of Al_2O_3-C Refractories

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China's Refractories 2011年第3期20卷 22-25页

作者： ZHANG Mengmeng YU Renhong zhou ningsheng High Temperature Materials Institute Henan University of Science and Technology Luoyang 471003 China

Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides composite powder addition on oxidation resistance of the Al2O3 - C refractories was investigated by measuring the thickness of oxidation layer. Phase compositions of the Al2O3 - C refractories before and after oxidation were investigated by X-ray diffraction （ XRD ）. Results show that the oxidation resistance of the Al2O3 - C refractories can be obviously improved by adding the synthesized ZrO2 - nitrides composite powder. The formation of mullite and zircon in the oxidation layer results in the densification of oxidation layer, which prevents oxygen diffusion and bnproves the oxidation resistance of the Al2O3 - C refractories.

关键词： Zirconia- nitrides composite powder Aluminacarbon refractories Oxidation resistance