MICROSTRUCTURE AND THERMAL STRESS RELAXATION OF ZrO_2－Ni FUNCTIONALLY GRADED MATERIAL

ＭＩＣＲＯＳＴＲＵＣＴＵＲＥＡＮＤＴＨＥＲＭＡＬＳＴＲＥＳＳＲＥＬＡＸＡＴＩＯＮＯＦＺｒＯ_２－ＮｉＦＵＮＣＴＩＯＮＡＬＬＹＧＲＡＤＥＤＭＡＴＥＲＩＡＬ￥ＺｈｕＪｉｎｇｃｈｕａｎ；ＹｉｎＺｈｏｎｇｄａ；ＬａｉＺｈｏｎｇｈｏｎｇ；ＬｉＪｉａｎ（Ｓｃｈｏ?..     

EFFECT OF MnO2 ADDITIVE ON PERFORMANCES OF NiFe2O4 SPINEL BASED INERT ANODE

1. Introduction Recent efforts to replace the carbon anode of the Hall-Héroult process with an oxygen-evolving, non-consumable anode started in the late 1960s. Aside from simplification of the process because no carbon anodes need to be manufactured and …     

HATi/Ti/HATi轴对称生物功能梯度材料的制备及其热应力缓和特性

用粉末冶金法制备出ＨＡＴｉ／Ｔｉ／ＨＡＴｉ 轴对称生物功能材料（ＦＧＭ） , 并测定了ＨＡＴｉ 复合体材料的力学性能和热膨胀系数。应用经典叠层板理论和热弹性力学理论分析了ＨＡ４０Ｔｉ／Ｔｉ／ＨＡ４０Ｔｉ 直接叠层体和轴对称ＦＧＭ 制备残余热应力。结果表明其微观组织呈对称型梯度化分布。ＦＧＭ 中间纯Ｔｉ 层具有最高的抗弯强度和断裂韧性（ 分别为９７１ ．９６ ＭＰａ 和２９ ．６９１ ＭＰａ·ｍ １／２） , 而表面层的弹性模量最低, 只有８７ ．７１ ＧＰａ。从生物医学应用的角度看, 力学性能如此分布的生物材料正是我们所期望的。其热膨胀系数随着ＨＡ 含量和温度的升高而增大。制备残余热应力强烈依赖于组成分布,组成对称梯度化分布导致了ＦＧＭ 中残余热应力也呈现对称梯度化分布, 并降低了其表面层制备残余拉应力。     

Electrical resistivity of NiFe_2O_4 ceramic and NiFe_2O_4 based cermets

NiFe2O4 ceramic and NiFe2O4 based cermets, expected to be used as the inert anodes in aluminum electrolysis, were prepared and their electrical resistivities were measured at different temperatures. The effects of temperature and composition on their electrical resistivities were investigated. The results indicate that the electrical resistivities of NiFe2O4 based cermets mainly depend on temperature, resistivity of ceramic matrix, composition and dispersion of the metal phase among ceramic matrix. The electrical resistivity of NiFe2O4 ceramic decreases from 10. 094 Ω · cm to 0. 475 Ω · em with increasing temperature from 573 K to 1 233 K. The electrical resistivities of NiFe2O4 based cermets are greatly lowered, but decrease with increasing the temperature with similar trend compared to that of NiFe2O4 ceramic. The resistivities of NiFe2O4 based cermets containing 5 % Ni, 5 % Cu and 5 % CuNi alloy are 0. 046 8, 0.066 8 and 0. 0532 Ω · cm at 1 233 K, respectively, which are all acceptable as inert anode materials compared to that of the current carbon anode used for aluminum electrolysis.     

EFFECT OF Cu-Ni CONTENT ON THE CORROSION RESISTANCE OF (Cu-Ni)/(10NiO-90NiFe2O4) CERMET INERT ANODE FOR ALUMINUM ELECTROLYSIS

(Cu-Ni)/(10NiO-9ONiFe2O4 ) cermet inert anodes containing metal Cu-Ni 0,5, 10, 15 and 20 wt pet were prepared and their corrosion resistance to Na3AlF6-Al2O3 melts was investigated. The results indicate that the content of metal Cu-Ni has little effect on the steady-state concentration of Ni in the electrolyte and the values could not be used to effectively differentiate their corrosion resistance. The steady-state concentration of Fe decreases from 304×10-8 to 168×10-6 and that of Cu increases from 21×10-6 to 71×10-6 with the content of metal Cu-Ni increasing from 0 to 20 wt pct. Post-examination shows that metallic phase Cu-Ni is corroded preferentially during electrolysis and many pores are left at the anode surface. Considering the corrosion resistance and electrical conductivity, the cermet containing metal Cu-Ni 5 wt pct should be selected and studied further.     

ZrO2／Ni阶梯热障涂层的热冲击行为

研究了ＺｒＯ２／Ｎｉ阶梯热障涂层在火焰喷烧和水淬炳途中热冲击条件下的失效行为,建立了梯度热障涂层在火焰喷烧和水淬热冲击条件下一维温度场应力场的解析模型,实验结果表明,涂层的抗热冲击能力在火焰喷烧条件下随层次折增加而增强,在水淬热冲击条件下却随层次的增加而降低,证实涂层的抗热冲击能力与热冲击条件有关,并取地表面换热系数的大小与方向,故评价涂层的抗热冲击能力时须合理选择热冲击条件,按梯度设计,能大大提     

NiFe2O4基金属陶瓷惰性阳极的腐蚀研究进展

综述了近年来国内外铝电解用NiFe2O4基金属陶瓷惰性阳极在阳极组元的溶解与分布、腐蚀率的预测与测定以及氧化物和金属相对阳极腐蚀的影响三个方面所做的研究工作。     

Results from 100 h electrolysis testing of NiFe2O4 based cermet as inert anode in aluminum reduction

1 Introduction Since the Hall-Héroult process was applied in aluminum production, an inert anode was always the target that the aluminum industry was seeking for in the new technology field[1]. Some selection criteria have been defined in order to ident…     

基于GA-BP的NiFe2O4基金属陶瓷阳极优化设计

采用BP神经网络对铝电解NiFe2O4基金属陶瓷惰性阳极的电解腐蚀过程进行了系统辨识。建立了以Al2O3质量浓度、电解温度、分子比、面积比和电流密度为输入,腐蚀率为输出的网络模型。在材料的设计中,采用了GA-BP优化方法,BP网络参与GA迭代计算时对个体的评价。应用结果表明,NiFe2O4基金属陶瓷惰性阳极的电解腐蚀率预测结果与实测值吻合;优化设计的结果与实验值很接近。     

Effect of adding methods of metallic phase on microstructure and thermal shock resistance of Ni/（90NiFe2O4-10NiO） cermets

Ball mixing and electroless plating were respectively used as the adding methods of metallic phase to prepare Ni/（90NiFe2O4-10NiO） cermets for the inert anode in aluminum electrolysis. The microstructure and thermal shock resistance of cermet samples were studied. The results show that, for the samples prepared by ball mixing method, aggregation of metallic phase is found in either the green blocks or sintered samples and the extent of aggregation increases with the increase of metal content. For 6.5Ni/（90NiFe2O4-10NiO） cermets prepared with electroless plating method, the homogeneous and fine metallic particles are found in either the green compacts or sintered samples, but the relative density and thermal shock residual strength decrease by 3% and 28%-58% respectively, compared with samples prepared with ball mixing method.     

Preliminary testing of NiFe_2O_4-NiO as ceramic matrix of cermet inert anode in aluminum electrolysis

1　INTRODUCTIONTheideaofusinginertanodes(alsocallednon consumableoroxygen evolvinganodes)inaluminumproductionisasoldastheHall H啨ｒｏｕｌｔｐｒｏｃｅｓｓ ,dat ingbacktothediscoveryofoneoftheinventors ,Hall[1] .Inertanodesareintendedtoreplacethecon sumablecarbonanodethatiscurrentlyused .Withacarbonanode ,thecellreactionisAl2 O3+ 3/ 2C =2Al+ 3/ 2CO2 (1)where　acryolite basedmelt(Na3AlF6 AlF3 CaF2 )atnear 96 0℃servesassolventforthealumina .Withaninertanode ,thecellreactionwillbeAl2 …     

大尺寸NiFe2O4-10NiO/17Ni型金属陶瓷惰性阳极的制备

研究以PVA为主要成分的粘结剂体系的热分解特性对大尺寸粉末压坯脱脂行为的影响,发现PVA的不均匀热分解是造成大尺寸粉末压坯脱脂失效的原因之一,开发一种具有稳定热分解反应特性的新型粘结剂体系,实现大尺寸粉末压坯的无缺陷热脱脂;研究烧结气氛、金属相的添加对NiFe2O4-10NiO致密化行为的影响。结果表明：N2气氛烧结及加入Ni可有效提高NiFe2O4-10NiO陶瓷基体的烧结致密度,1350℃时于N2气氛中烧结的NiFe204．10NiO／5Ni型金属陶瓷材料的相对密度达到97．28％。采用优化工艺实现d120mmX140mm深杯状NiFe2O4-10NiO／17Ni金属陶瓷惰性阳极脱脂预烧坯的烧结,所得烧结坯平均相对密度为95．21％。     

ZnFe2O4基材料在NaF-AlF3-Al2O3熔盐中的腐蚀

采用锌铁尖晶石材料作为铝电解惰性阳极,考察了这种阳极在ＮａＦ－ＡｌＦ３－Ａｌ２Ｏ３熔盐中的腐蚀行为,阳极电视密度为０￣２．５Ａ／ｃｍ＾２。实验结果表明,锌铁尖晶石材料在阳极极化条件下的ＮａＦ－ＡｌＦ３－Ａｌ２Ｏ３熔盐中具有很好的耐腐蚀性能。在低电流密度下,阳极材料的腐蚀速度随电流密度的增大而增大,最高的腐蚀速度出现于０．５￣０．７５Ａ／ｃｍ＾２。此事,腐蚀速度随电流密度的增大而降低。实验证明,高阳     

Effect of Ni content on corrosion behavior of Ni/（10NiO-90NiFe2O4） cermet inert anode

Ni/（10NiO-90NiFe2O4） cermet inert anodes with metal Ni content of 0, 5, 10, 15 and 20 （mass fraction, %） were prepared and their corrosion behavior in Na3AlF6-Al2O3 melts was investigated in laboratory electrolysis tests. The results indicate that the content of metal Ni in anodes has little effect on the steady-state concentration of impurities Ni and Fe in electrolyte and the values range in （114-173）×10^-6 and （287-385）×10^-6, but the content of impurities in the metal aluminum manifolds. There is preferential corrosion for metal Ni in NiO-NiFe2O4 based cermet anodes. Considering the corrosion resistance and electrical conductivity, the cermet containing 5%Ni （mass fraction） behaves best among NiO-NiFe2O4 based cermet anodes studied, and should be further studied.     

两元P-型梯度结构热电材料FeSi_2/Bi_2Te_3的制备与性能

采用热浸焊法用纯Sn作为过渡层制备了P 型FeSi2 /Bi2 Te3 梯度结构热电材料并对其热电性能进行了测试。发现当热端温度在 5 10℃以下时 ,梯度结构热电材料的平均Seebeck系数保持恒定 ,达 2 2 0 μV/K至 2 5 0μV/K左右 ,显著高于单一均质材料 (Bi2 Te3 和 β FeSi2 )在相同温度范围内的平均Seebeck系数。梯度结构热电材料的输出功率较单种材料高 1.5至 2倍以上 ,且当材料经 190℃ ,10 0h与 2 0 0h的真空退火后 ,输出功率几乎不变。金相观察表明 ,在Sn层与两半导体界面处 ,没有明显的Sn扩散迹象 ,说明在所试验的条件下 ,用Sn作为过渡层热稳定性较好。     

Effect of metallic phase content on mechanical properties of （85Cu- 15Ni）/（10NiO-NiFe2O4） cermet inert anode for aluminum electrolysis

（85Cu-15Ni）/（10NiO-NiFe2O4） cermets were prepared with Cu-Ni mixed powders as toughening metallic phase and 10NiO-NiFe2O4 as ceramic matrix. The phase composition, microstructure of composite and the effect of metallic phase content on bending strength, hardness, fracture toughness and thermal shock resistance were studied. X-ray diffraction analysis indicates the coexistence of （Cu-Ni）, NiO and NiFe2O4 phases in the cermets. Within the content range of metallic phase from 0% to 20% （mass fraction）, the maximal bending strength （176.4 MPa） and the minimal porosity （3.9%） of composite appear at the metallic phase content of 5%. The fracture toughness increases and Vickers＇ hardness decreases with increasing metal content. When the thermal shock temperature difference （At） is below 200 ℃, the loss rate of residual strength for 10NiO-NiFe2O4 ceramic is only 8%, but about 40% for （85Cu-15Ni）/（10NiO-NiFe2O4）cermets. As At is above 200 ℃, the residual strength sharply decreases for sample CN0 and falls slowly for samples CN5-CN20.     

Effect of BaO addition on electric conductivity of xCu/10NiO-NiFe2O4 cermets

The effects of BaO addition on the phase composition, relative density and electric conductivity of xCu/10NiO-NiFe2O4 （x=5, 10） eermets were studied, which were prepared with cold isostatic pressing-sintering process. The results show that the relative densities of 5Cu/10NiO-NiFe2O4 cermet doped with 1% BaO （mass fraction） and 10Cu/10NiO-NiFe2O4 cermet doped with 1% BaO sintered at 1 473 K in nitrogen atmosphere, are increased by about 9.86% and 9.75% compared with the undoped BaO cermets, respectively. And the electric conductivities 22.79 S/cm of 5Cu/10NiO-NiFe2O4 cermets adding 1% BaO and 23.10 S/cm of 10Cu/10NiO-NiFe2O4 cermets adding 1% BaO are obtained, which are 2.21 times and 1.47 times of those of undoped samples, respectively. Moreover, the 10Cu/10NiO-NiFe2O4 cermets doped with 1% BaO have a maximum σ0 of 58.91 S/cm and electric conductivity of 23.10 S/cm at 1 233 K. Maybe low melting-point phases of BaFe2O4 and Ba2Fe2O5 have an excellent electric conductivity in xCu/10NiO-NiFe2O4 （x=5, 10） cermets at 1 233 K.     

Effect of Structural Parameters on the Thermal Stress of a NiFe2O4-Based Cermet Inert Anode in Aluminum Electrolysis

Inert anode has been a hot issue in the aluminum industry for many decades. With the help of FEA(finite element analysis) software ANSYS,a model was developed to simulate the thermal stress distribution working condition of an inert anode. To reduce its thermal stress,the effect of some parameters on the thermal stress distribution was investigated,including the anode height,the anode radius,the hole depth,the hole radius,and the radius of inner chamfer and outer chamfer. The results showed that in the actual working condition of an inert anode,there existed a large axial tensile stress near the tangent interface between the anode and bath,which was the major cause of anode breaking. Increasing the anode height and reducing the hole depth properly seemed to be beneficial for the stress distribution. With the increase of anode radius,the stress distribution became better first and then deteriorated,the reasonable value was between 0.045 to 0.06m. The hole radius had a significant effect on the stress and a smaller radius would reduce the thermal stress. The effect of the radius of the inner chamfer and the outer chamfer was less than other parameters.     

PROPERTIES OF W/Cu FGMS CONTAINING 1%TiC OR 1%La2O3 PREPARED USING GSUHP

W / Cu functionally gradient materials (FGMs) containing 1%La_2O_3 and 1%TiC were prepared using graded sintering under ultra-high pressure (GSUHP). The specimens have been found to exhibit low porosity (11.57% and 11.35%, respectively). Shearing strength of the specimens between layers is good. Moreover, the specimens have still demonstrated good performance in testing thermal-shock resistance. When power density of laser is 200MWm~(-2), the specimens have been tested for thermal-shock resistance (1000 times); the specimens that contained 1%La_2O_3 were not subjected to damage, whereas those that contained 1%TiC began to crack. Finally, effect of additives on thermal-shock resistance was also preliminarily discussed.