掺杂不同质量分数Y_2O_3、MgO对Al_2O_3陶瓷显微结构及介电性能的影响

利用放电等离子烧结技术制备了不同质量分数Y_2O_3单独掺杂及不同质量分数Y_2O_3、MgO共同掺杂的Al_2O_3陶瓷,研究了烧结助剂掺杂质量分数对Al_2O_3陶瓷显微结构及介电性能的影响。结果表明,孔隙率是影响Al_2O_3陶瓷介电性能的主要因素;单独掺杂质量分数为0.25% Y_2O_3时,Al_2O_3陶瓷得到最优的介电性能,介电常数(ε_r)为9.5±0.2,介质损耗(tanδ)稳定在10~(-3)数量级以内;同时掺杂Y_2O_3和MgO能进一步改善其介电性能,当两者质量分数均为0.25%时,得到最优值,介电常数(ε_r)为10.3±0.2,介质损耗(tanδ)稳定在8×10~(-4)以下。     

Effects of Nd, Sm, Gd, Dy, Er Dopant on Electrical Properties of BaTiO3 Ceramics

BaTiO3 ceramics doped with various quantities of Nd2O3, Sm2O3, Gd2O3, Dy2O3 and Er2O3 were prepared respectively ( the adulterate concentrations were 0. 001,0. 002, 0. 003, 0.005, 0. 007 mol fraction) through a sol-gel method and their electrical properties were researched. It is found that each adulteration of Nd2O3, Sm2O3 Gd2O3,Dy2O3 and Er2O3 all can make the resistivity of BaTiO3 ceramics decline , especially Sm2O3 and Gd2O3. When the addition of Sm2O3 is 0. 001 mol, the resistivity is the smallest, declining from 4.0 × 1012 to 6.5 × 103 Ω different kind of rare earth exhibits different regularity. The grain resistance of BaTiO3 ceramics doped with Sm2O3 or Gd2O3 exhibits a NTC effect, at the same time the grain boundary resistance has a PTC effect, and the grain boundary resistance is much larger than the grain resistance, so the PTC effects of BaTiO3 ceramics doped with Sm2O3 or Gd2O3 originate from the grain boundary. The additions of Nd2O3 , Gd2O3 or Er2O3 make the dielectric constant and the dielectric loss of BaTiO3 ceramics change evidently, especially Nd2O3. The dielectric constant is larger than that of pure BaTiO3 ceramics, on the other hand, the dielectric loss is much lower, which is useful in capacitor fields.     

精炼钢包用Al_2O_3-MgO-CaO系复相耐火材料的研发

为适应精炼钢包用耐火材料轻量化的发展需要,采用两步烧结法向Al_2O_3-MgO-CaO系复相耐火材料中添加La_2O_3,并对该耐火材料的抗LF精炼渣侵蚀性能进行了研究。结果表明,添加的La_2O_3优先固溶入Al_2O_3-MgO-CaO系复相耐火材料的晶相CaO·6Al_2O_3中,促使CaO·6Al_2O_3晶胞产生晶格畸变,有效抑制了CaO·6Al_2O_3晶粒沿基面的异常长大,进而有效地促进了Al_2O_3-MgO-CaO系复相耐火材料的烧结致密化。当添加La_2O_3的质量分数为4%,在1600℃保温2h烧成后,试样的气孔率由占总体积分数的19.2%下降至6.1%,体积密度由2.78g/cm3上升至3.18g/cm3,制得了含MgO·Al_2O_3、CaO·2Al_2O_3、CaO·6Al_2O_3晶相且呈现交织分布、显微结构致密的Al_2O_3-MgO-CaO系复相耐火材料,其抗LF精炼渣侵蚀性能与同等致密度的Al_2O_3-MgO质耐火材料相当。     

Thermodynamic Calculation of Inclusion Formation in Mg-Al-Si-O System of 430 Stainless Steel Melts

 A phase diagram was drawn through thermodynamic calculation to understand the equilibrium conditions of 2MgO·SiO2, MgO·Al2O3, 3Al2O3·2SiO2, and 2MgO·2Al2O3·5SiO2 formation in Mg-Al-Si-O system of 430 stainless steel melts at 1873 K. Further, the thermodynamic formation and transformation conditions of MgO·Al2O3 inclusion were discussed. The following results are obtained when wSi=026% and wO=10×10-5 in molten steel. The uniphase cordierite inclusion is difficult to exist stably; MgO·Al2O3 inclusion cannot be formed in case of wAl being less than 1×10-6; 3Al2O3·2SiO2 would change to MgO·Al2O3 and 2MgO·SiO2 in turn with increasing the Mg content when wAl is above 17×10-6; with the formation of MgO·Al2O3 inclusion, Al content increases with increasing Mg content when wMg is over 17×10-9. For equilibrium condition and calculated steel composition, 2MgO·SiO2 inclusion would be formed ultimately and MgO·Al2O3 is almost inexistent.     

430不锈钢尖晶石夹杂物控制的热力学分析

通过热力学计算,得出了硅脱氧430不锈钢熔体Fe-Mg-Al-Si-O体系MgO.Al2O3、2MgO.SiO2、3Al2O3.2SiO2和2MgO.2Al2O3.5SiO2的平衡相图,分析了控制尖晶石夹杂物形成与转变的热力学条件。结果表明:1 873 K时,当钢中Al的质量分数在1×10-6以下,钢水中基本不形成镁铝尖晶石;随钢水中溶解铝含量的逐渐降低,由尖晶石转变为2MgO.SiO2所需的溶解氧质量分数逐渐提高。当钢水中溶解镁的质量分数在2×10-6,控制钢水中w(Al)4×10-5、w(O)8×10-6时,对于抑制不锈钢尖晶石夹杂物的形成有利。     

Study on BaO-Sm2O3-TiO2 Microwave Dielectric Ceramics Doped with Bismuth and Zinc

BaO-Sm2O3-TiO2 microwave dielectric ceramics doped with Bi and Zn was studied. The experiment was based on BST microwave dielectric ceramics doped with Bi2O3, which is shown by Ba4(Sm1-yBiy)28/3Ti18O54. When y=0.15, ZnO was added and the effects of ZnO on this system were studied. The result shows that the dielectric characteristics of BST microwave dielectric ceramics are the most excellent when the content of ZnO is 3%, and the optimal sintering temperature is 1200 ℃.     

氧化钆对钛酸钡陶瓷结构和介电性能的影响

采用固相法制备得到了掺杂 1% (mol) Gd2 O3的钛酸钡陶瓷 ,并通过 X射线衍射分析和扫描电镜对其结构进行了表征。对其介电常数、介电损耗和室温电阻率进行了测定 ,结果表明 Gd2 O3掺杂 Ba Ti O3陶瓷的介电常数明显增加 ,介电损耗也有所升高 ,室温电阻率明显降低     

Effects of Rare-Earth La2O3 Addition on Microstructures and Electrical Properties of SrTiO3 Varistor-Capacitor Dual Functional Ceramics

Generally, metal oxide varistors used for the pro tection of electrical circuits are based on ZnO andTiO2[1,2]. ZnO varistor, which is widely used due toits high non linearity coefficient, is composed of ZnOceramics with minor oxide additive…     

Preparation and Performance of Al2 TiO5 -TiO2 -SiO2 Honeycomb Ceramics by Doping Rare Earth

A preferable honeycomb ceramics of Al2TiO5-TiO2-SiO2 doped by CeO2 and Er2O3 with high performance was prepared by means of extrusion molding and the effects of CeO2 and Er2O3 on the mechanical strength, thermal stability, and sintering temperature of ATS ceramics were mainly investigated. The experimental results and the microscopic analysis by scanning electron microscope, X-ray powder diffxaction, and TG-DSC showed that adding CeO2 and Er2O3 into ATS could prohibit the growth of their crystal grains and make their size uniform, which finally decrease its sintering temperature, and also enhance its mechanical performance as well as thermal stability. After the reforming, ATS doped by 0.5% CeO2 ＋0.5% Er2O3 was sintered at 1250 ℃, its bending strength reached to 177A MPa and thermal expansion coefficient was 3.8 ~ 10^-6/℃ at 25 - 1000℃, which provided a promising basis of making monolithic honeycomb catalyst of deNOx.     

Mg脱氧对船板结构钢中夹杂物的影响

研究了Mg脱氧对于船板结构钢中微米级夹杂物演变行为的影响.钢中典型夹杂物是中心为氧化物、外围为MnS的复合夹杂物.随着钢中Mg含量的增高,独立氧化物和独立硫化物的数量减少,氧化物和硫化物的复合夹杂物数量增多,同时夹杂物的尺寸减小、数量增加.随着钢中Mg含量从0升高到27 ×10^-4％、38×10^-4％、99 ×10^-4％,夹杂物中心氧化物成分的变化趋势是：Al2O3→（Mg-Al-Ti-O）→MgO.     

Effect of La2O3-Dopant on Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb2O5-TiO2 System Ceramics

With the development of microwave integratedsystem for wireless communication, requirements ofthe microwave device are combined with high dielec tric constants (εr), low dielectric losses (Q = 1/tanδ) and near zero temperature coefficient for stabili ty and frequency selectivity[1,2]. But it is hard to findmaterials that satisfy all above mentioned requiredcharacteristics. In general, a ceramic with a high di electric constant has a larger positive temperature coef fi…     

MnO_2掺杂BaTi_4O_9陶瓷微波介电性能研究

采用传统固相反应法合成BaTi_4O_9粉体,复合掺杂质量分数为0~0.16%MnO_2,在空气气氛下常压烧结制备BaTi_4O_9陶瓷。研究了MnO_2对BaTi_4O_9陶瓷的相组成、微观形貌、烧结特性及介电性能的影响。X射线衍射分析和扫描电子显微镜观察表明,Mn完全固溶到BaTi_4O_9陶瓷中;随着MnO_2掺杂量的增加,晶粒更加均匀,BaTi_4O_9陶瓷更加致密,介电常数略微降低,品质因数和谐振频率温度系数先显著提高继而降低;MnO_2掺杂BaTi_4O_9陶瓷发生Ti位取代,高温烧结时在一定程度上抑制了Ti~(4+)还原为Ti~(3+),从而改善BaTi_4O_9陶瓷微波介电性能。在烧结温度1250℃,保温时间4 h,掺杂MnO_2质量分数为0.08%时,BaTi_4O_9陶瓷微波介电性能最优,介电常数(εr)为34.56,品质因数(Q·f,中心频率5 GHz)为49097,谐振频率温度系数(τ_f)为14.997×10~(-6)/℃,相对密度最大,达97%。     

高速铁路车轴用25CrMoVNi超低氧钢RH精炼过程非金属夹杂物的行为

25CrMoVNi钢由120 t EAF-LF-RH脱气-φ600 mm圆坯连铸工艺生产,EAF出钢时加Al预脱气使[Al]s≥0.030%,并加入石灰造渣预精炼,LF精炼时炉渣表面加Al粒扩散脱氧,LF精炼渣的组成为（/%）:53~57CaO,10~13SiO₂,27~28Al₂O₃,6~9MgO,0.09~0.10MnO。RH脱气精炼结果表明,RH后T[O]由脱气前0.001 3%~0.001 5%降至0.000 5%;钢中TCa由0.001 9%降至0.000 9%~0.001 7%;夹杂物发生MgO·Al₂O₃→（MgO）z（CaO）x（Al₂O₃）y→（CaO）x（Al₂O₃）y的转变;最后以尖晶石类固相夹杂物数量迅速减少,以钙铝酸盐类的液相夹杂物数量呈现出先增加后减少,钢中夹杂物由6.7个/mm²下降至2.7个/mm²     

Ni0．5Zn0．5La0．05Fe1.95O4铁氧体的制备与吸波性能研究

采用高分子凝胶法制备了Ni0．5Zn0．5La0．05Fe1.95O4铁氧体。当煅烧温度为600℃时,立方晶系尖晶石结构的Ni0．5Zn0．5La0．05Fe1.95O4相初步形成。掺杂稀土La后,Ni0．5Zn0．5La0．05Fe1.95O4铁氧体的吸波性能显著提高,吸收峰向高频移动,其电磁波反射率小于～10dB的频宽可达2．7GHz,最小反射率为-15．6dB。     

Effect of La2O3 on Microstructure and Transmittance of Transparent Alumina Ceramics

Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities （T. D. ） with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at twavelength range of 300 - 800 nm.     

CaF2-CaO-Al2O3-SiO2-MgO五元渣的表面张力及其在镍基合金电渣重熔的应用

试验研究了五元渣（/%:50~65CaF₂,6~15CaO,18~30Al₂O₃,4~10SiO₂,1~7MgO）的组元含量、熔渣温度（1330~1463℃）对表面张力的影响。结果表明,随熔渣温度升高,其表面张力下降,1463℃五元渣的表面张力为0.372~0.418 N/m。60CaF₂-15CaO-6SiO₂-18Al₂O₃-5MgO具有较低的表面张力（0.375 N/m）,较好的流动性和低粘度值。3 t电渣炉熔炼镍基合金Inconel 600和625的工业应用结果表明,电渣锭成分均匀,[O]≤20×10^-6,[N]≤50×10^-6,平均电耗从原ANF-6渣重熔的1933 kWh/t降至1 326 kWh/t。     

Effects of Doping CeO2, Er2O3 on Properties of TiO2-SiO2 Ceramics for Catalyst Supporter of deNOx

Effects of doping CeO2 and Er2O3 on the mechanical strength, thermal expansion coefficient, sintering temperature of TiO2-SiO2 ceramics were investigated. The experimental results and the microscopic analysis of SEM, XRD, TG-DSC, FT-IR and TEM show that adding CeO2 and Er2O3 into TiO2-SiO2 ceramics can prohibit the growth of its crystal grains, make their size uniform and form them into a dense structure, which finally enhance its mechanical behaviors, and the lower thermal expansion coefficient that leads to an excellent property of thermal shock resistance. After the reforming TiO2-SiO2 ceramics doped by CeO2 was sintered at 1380 ℃, the bending strength reached to 83 MPa, and the thermal expansion coefficient was 9.8×10-6/℃ within the temperature range of 25～800 ℃, which provides a promising basis of making equipped honeycomb catalyst of deNOx.     

Effects of La~（3＋） on osteogenic and adipogenic differentiation of primary mouse bone marrow stromal cells

In order to elucidate the action of La3+ on bone metabolism,effects of La3+ on the osteogenic and adipogenic differentiation of pri-mary mouse bone marrow stromal cells(BMSCs) were studied by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) test,alkaline phosphatase(ALP) activity measurement,mineralized function,oil red O stain and measurement.The results showed that La3+ pro-moted the proliferation of BMSCs except at 1×10-10 and 1×10-6 mol/L.The effect of La3+ on the osteogenic differentiation depended on con-centrations at the 7th day,but the osteogenic differentiation was inhibited at any concentration at the 14th day.La3+ promoted the formation of mineralized matrix nodules except at 1×10-8 and 1×10-5 mol/L.La3+ inhibited adipogenic differentiation except at 1×10-10 and 1×10-7 mol/L at the 10th day,and inhibited adipogenic differentiation except at 1×10-9 mol/L at the 16th day.These findings suggested that La3+ might have protective effect on bone at appropriate dose and time.This would be valuable for better understanding the mechanism of the effect of La3+ on bone metabolism.     

超低氧齿轮钢非金属夹杂物控制热力学计算及应用

 利用热力学软件计算了齿轮钢氧含量与夹杂物成分的关系、夹杂物转变条件。结果表明,超低氧20 CrMoH钢中具有较高塑性的非金属夹杂物成分为：SiO2 0%~10%、Al2O3 22%~55%、CaO 42%~60%、MgO 5%~10%,与之平衡的时钢液中铝含量在0.020%左右,钙含量>0.7×10-6,氧含量在0.0005%左右;选择组成为CaO>40%、Al2O3≤37%、MgO10%、(%CaO+%MgO)/%SiO2为10、SiO2含量尽量低的渣系,钢中Al2O3、MgO•Al2O3夹杂物可转变为低熔点的钙铝酸盐。上述结果在工业试验中得到了验证。     

LF精炼渣碱度变化对304不锈钢夹杂物成分的影响

采用氧氮分析仪、扫描电镜、金相显微镜等分析手段,系统研究LF精炼渣系对304系不锈钢全氧质量分数wT[O]、夹杂物数量、尺寸及成分的影响。研究结果表明,当LF精炼渣碱度由1.5升高至2.6时,LF出站溶解氧质量分数w[O]由11.6×10~(-6)降低至4.8×10~(-6),铸坯wT[O]由47×10~(-6)降低至24×10~(-6),铸坯夹杂物总数量降低,但当量直径不大于10μm的夹杂物所占比率由77.7%增加至95.1%。热力学计算结果表明:在钢液中各元素达到平衡状态时,渣系碱度越高,低熔点夹杂物2MgO·2Al_2O_3·5SiO_2生成区域越小,MgO·Al_2O_3尖晶石类夹杂物生成区域越大,与生产试验结果一致。随着LF炉渣碱度升高,铸坯夹杂物成分中MgO和Al_2O_3的质量分数分别升高了14.4%和9.1%,当碱度不大于1.9时,铸坯中不会存在镁铝尖晶石。