氧化镧对镁橄榄石晶体结构及性能的影响_英文_

摘要： 以低品位菱镁矿与天然硅石为原料， 以氧化镧为添加剂， 通过固相反应烧结制备镁橄榄石 。 研究讨论了氧化 镧对镁橄榄石材料相组成 、 晶胞参数、 微观结构及常温性能的影响 。用 XＲD 和 SEM 法对烧后试样的相组成和显微 结构进行研究。利用 X’pert plus 软件对试样中镁橄榄石相的晶胞参数进行计算 。 按国家标准， 检测镁橄榄石试 样的体积密度、 显气孔率、 吸水率和常温耐压强度 。结果表明： 加入适量氧化镧可以促进了低品位菱镁矿轻烧氧化 镁粉与天然硅石中通过固相反应烧结合成制备镁橄榄石 。氧化镧加入量为 1． 2% 时， 镁橄榄石的晶胞体积最大， 镁 橄榄石中引入氧化镧所造成的结构缺陷加速了离子扩散速度， 而过量的氧化镧会进入晶界液相中 。 综合以上分
2 LUO Xudong1， ， QU Dianli1 ， XIE Zhipeng2 ， QIN Bin1 ， SONG Yang1
（ 1． Department of High Temperature Materials and Magnesium Ｒesource Engineering， Liaoning University of Science and Technology，Anshan 114051 ，China； 2． State Key Lab of New Ceramics and Fine Processing， Department of Materials Science and Engineering，Tsinghua University，Beijing 100084 ，China）
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Experimental
Specimen formulas and preparations The composition of the experimental based formula is as followed： 57wt% of active magnesia sintered from
第 32 卷 第 9 期 2013 年 9 月
硅
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BULLETIN OF THE CHINESE CEＲAMIC SOCIETY
Vol． 32 No． 9 September， 2013
Influence of La2 O3 on the Crystalline Structure and Property of Forsterite
3 析， 氧化镧的引入量为 1． 2% 时， 镁橄榄石材料综合性能最好， 其体积密度为 2． 44 g / cm ， 显气孔率为 23 % ， 吸水率
常温耐压强度为 30． 1 MPa。 为 9． 5 % ， 关键词： 低品位菱镁矿； 天然硅石； 镁橄榄石； 氧化镧
Foundation item： Key Project in the National Science and Technology Pilar Program during the Twelfth Fiveyear Plan Period（ 2012BAB06B00 ） Biography： LUO Xudong （ 1980） ，male，doctor． Major in refractories for iron and steel making． Email： luoxudong6393@ ustl． edu． cn
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专题论文
ቤተ መጻሕፍቲ ባይዱ
硅 酸 盐 通 报
第 32 卷
1
Introduction
Forsterite is a crystalline magnesium silicate with the chemical formula Mg2 SiO4 in the MgOSiO2 system which
belongs to the group of olivines［1］． The extremely low electrical conductivity of forsterite makes it an ideal material for tunable laser． It shows also good refractoriness due to high melting temperature，low thermal expansion，good chemical stability and excellent insulation properties even at high temperature［2，3］． Forsterite is widely synthesized via a solid phase reaction method that is more preferable in the synthesis of forsterite［4］． The high temperature and long reaction time are generally needed to facilitate reactant diffusion to form forsterite in the solid phase reaction． Therefore，the method of extra addition of mineralizer is often employed to decrease the sintering temperature and improve the properties of the synthetic． The properties of forsterite will be improved by the fluxing action of rare grade earth elements in sintering process［5］． The aim of the present study is to synthesize forsterite from lowmagnesite and nature silica． The influence of La2 O3 on crystalline structure of produced forsterite has been studied． Compared with the conventional synthetic techniques， this study is innovative in raw material， process and technology．
Abstract： The influence of La2 O3 on the crystalline structure of forsterite synthesized from lowgrade magnesite and natural silica is discussed． Xray diffraction （ XＲD ） and scanning electron microscopy （ SEM） were employed to characterize the crystalline structure and microstructure of each specimen． X’ Pert plus software was used to determine the lattice parameters of each specimen． Bulk density，apparent porosity，water absorption and cold crush strength of the test samples were tested according to standards issued by the ministry． The results show that appropriate La2 O3 addition is helpful to form forsterite． When the addition of La2 O3 is 1． 2wt% ，the cell bulk of forsterite reaches the highest，the defects caused by La2 O3 accelerate the diffusion rate of the cations． Excess La2 O3 will solve into the liquid on the grain boundary． In combination of XＲD，SEM and property analysis results，the optimal addition of La2 O3 is determined to be 1． 2% ． Corresponding，bulk density is 2． 44 g / cm3 ，apparent porosity is 23% ，water absorption is 9． 5% and cold crush strength is 30． 1 MPa． Key words： lowgrade magnesite； natural silica； forsterite； La2 O3
lowgrade magnesite，43wt% of natural silica［6］． On the basis formula，the La2 O3 content was increased to 0． 4wt% ，0． 8wt% ， 1． 2wt% ， 1． 6wt% and 2． 0wt% ，respectively． The specimens were numbered No． 1 （ the based formula） and No． 2No． 6 accordingly． The batching underwent vibration milling，semidry pressing，forming and drying． After being dried，the body materials were calcined under 1500 ℃ respectively，and the temperature was maintained for 2 h． 2． 2 Property test The crystal structure and the phase constitution were studied using Philips X＇ PertMPD Xray diffraction． The analysis conditions were Cu target （ Kα ） ，tube voltage of 40 kV and tube current of 100 mA． The crystal cell parameters and volume of forsterite was calculated by X ＇ Pert plus software． The crystal appearance and microstructure of specimens were observed in Japanese electronics JSM6480 LV scanning electron microscopy （ SEM） ． Properties of the test samples，such as bulk density，porosity，water absorption and cold crush strength， were tested．