CaO掺杂对10NiO-NiFe2O4复合陶瓷烧结致密化的影响

采用冷压烧结技术制备了CaO掺杂的10NiO-NiFe2O4复合陶瓷,研究了CaO掺杂量及烧结温度对10NiO-NiFe2O4复合陶瓷物相组成、显微结构及致密度的影响。结果表明:当CaO掺杂量为0~4%(质量分数)时,烧结样品中主要含有NiO和NiFe2O4两种,CaO与10NiO-NiFe2O4陶瓷组分反应并形成低熔点相,且Ca2 离子固溶到基体组分中,促进致密化烧结,降低了烧结温度;当CaO掺杂量为4%时,过剩的CaO存在于陶瓷颗粒间,抑制了致密化过程的进行;于1 200℃烧结时,2?O掺杂样品的相对密度最大,达到98.75%,比未掺杂样品的相对密度提高近24%;当烧结温度从1 200当升高到1 400℃时,CaO掺杂量为0、0.5%和1.0%的样品相对密度提高20%以上,但当CaO掺杂量为2%和4%时,陶瓷样品相对密度反而下降,且晶粒明显长大。     

BaO掺杂对10NiO-NiFe2O4复合陶瓷烧结致密化的影响

利用冷压一烧结技术制备BaO掺杂的10NiO-NiFe2O4复合陶瓷,研究BaO掺杂量及烧结温度对10NiO-NiFe2O4复合陶瓷物相组成、显微结构及致密度的影响。结果表明：当BaO掺杂量（质量分数）为0,-4％时,烧结样品中主要含NiO和NiFe2O4,BaO与10NiO-NiFe2O4陶瓷组分反应并形成瞬时液相BaFe2O4和Ba2Fe2O5,且Ba2＋固溶到基体中,促进致密化烧结,降低了烧结致密化温度;1250℃烧结时,1％BaO掺杂样品的相对密度最大,达到98．90％,比未掺杂样品的相对密度提高6．27％;但当BaO掺杂量为2％和4％时,陶瓷样品相对密度基本不变。     

Nb2O5掺杂NiFe2O4陶瓷材料的显微结构和导电性能

以NiO、Fe2O3和Nb2O5为原料,采用固相烧结法合成陶瓷粉体,通过等静压-气氛烧结法制备Ni1-xNbxFe2O4(x=0,0.02,0.05,0.07,0.10,0.20)陶瓷试样,并对其进行导电性能测试。通过XRD、SEM、EDX、FTIR和XPS等分析手段对材料的物相组成、显微结构和微区成分进行表征,研究Nb2O5掺杂对陶瓷材料显微结构和导电性能的影响。结果表明:Nb2O5掺杂抑制NiFe2O4基体中NiO相的出现,过量时生成FeNbO4相;适量掺杂(x=0.05)有利于消除晶界孔隙,提高陶瓷的烧结密度;与未掺杂试样相比,掺杂Nb2O5的NiF2O4陶瓷材料的导电性均得到很大改善,其中掺杂量x=0.05的Ni0.95Nb0.05Fe2O4陶瓷试样在1 233 K的电导率较纯NiFe2O4的提高60%。     

Mn掺杂In2O3陶瓷材料的高温热电传输性能

利用放电等离子(SPS)烧结工艺制备Mn掺杂In2O3多晶陶瓷材料。通过测试热电传输性和观察微观结构,研究了掺杂工艺对SPS烧结多孔结构In2O3陶瓷传输性能的影响。结果表明,低浓度掺杂的样品在测试温度范围内能得到较高的电导率和热电势;掺杂试样In1.99Mn0.01O3在973 K可获得最高的热电功率因子4.0×10-4W.K-2.m-1,从而可知,控制In2O3中低浓度的Mn的掺杂量可获得较好的高温n型热电材料。     

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.     

Al2O3,CaO对多元掺杂YSZ电解质材料性能的影响

采用高温固溶法制备了Dy2O3,Sc2O3和Yb2O3多元掺杂YSZ材料,试样高温电导率得到大幅度提高(1000℃,0.18S/cm),但材料烧结性与机械强度有待改善.为此,在多元掺杂YSZ材料中继续掺入少量Al2O3和/或CaO以研究其影响.添加少量Al2O3提高了试样烧结密度( ～4.6%)和机械强度(～30%),而保持电导率变化不大;添加少量CaO虽然使烧结密度略微增大,但却降低了试样电导率(～50%)和机械强度.XRD分析显示试样保持稳定立方萤石结构,且晶格常数发生变化.显微结构分析表明,复合添加剂的掺入促进了晶粒的生长,晶粒尺寸较大.     

K+掺杂改性的Ca3Co4O9基氧化物热电性能

用溶胶-凝胶法和放电等离子烧结(SPS)制备了层片状结构的(Ca1-xKx)3Co4O4陶瓷,烧结块体相对密度可达97%～99%.XRD(X-ray Diffraction)和SEM(Scanning Electronic Microscope)分析结果表明当K的掺杂量x＜0.08时为单一的Ca3Co4O9相,SPS烧结可以使样品带有一定的织构取向.在室温至700℃的范围内测量了不同K掺杂量时样品电导率和Seeback系数,测试结果表明,当K的掺入量小于0.06时,随着掺入量的增加,可以显著提高样品的电导率(400℃～700℃)和Seebeck系数.其中,700℃时(K0.06Ca0.94)3Co4O9样品的功率因子P=4.43×10-4W·m.-1K-2,与Ca3Co4O9(P=3.51×10-4W.m.-1K-2)相比提高了26.2%,表明K掺杂是改善Ca3Co4O9高温热电性能的有效途径之一.     

复合掺杂对YSZ电解质材料烧结性与电性能的影响

采用高温固溶法制备Sc2O3（Dy2O3）和Yb2O3复合掺杂YSZ电解质材料，研究了复合掺杂对YSZ烧结性和电性能的影响。结果表明：随着Sc2O3含量的增加，试样烧结密度降低（1600℃烧结密度由5．82g／cm^3降至5．24g／cm^3），而Dy2O3却能提高烧结密度（1600℃烧结密度由5．63g／cm^3增至5．86g／cm^3）：当掺杂总量x，％）为8～8．6时，材料电导率得到大幅度提高（1000℃时，0．18S／cm）；1nσ-1000／T呈现较好的线性关系，说明电导率σ与温度T之间关系符合Arrhenius公式；XRD分析表明复合掺杂YSZ电解质材料晶格常数有所增大，对提高电导率起积极作用；复合添加剂促进了晶粒生长，尤其是含Dy试样晶粒尺寸较大。     

烧结助剂对高气孔率SiC陶瓷结构和性能的影响

由叔丁醇、丙烯酰胺和SiC粉及烧结助剂组成固相含量为10%(体积分数)的陶瓷浆料,采用凝胶注模成型和无压烧结工艺制备多孔SiC陶瓷,研究Al2O3和Al2O3+SiO2这两种烧结助剂体系对多孔SiC陶瓷的气孔率、显微结构和力学性能的影响。结果表明:Al2O3+SiO2复合烧结助剂明显改善SiC陶瓷的烧结性能,与采用单一的Al2O3烧结助剂相比,SiC样品的烧结温度和莫来石的生成温度均降低50℃左右;两种不同的烧结助剂制成的试样中的气孔均呈很窄的单峰分布,中位孔径为2μm左右;随烧结温度的升高压缩强度增大,而气孔率变化不大;以Al2O3+SiO2为烧结助剂、在1 400℃烧结的试样的气孔率和强度分别达到70.57%和17.74 MPa。     

La~(3+)掺杂Y_2O_3透明陶瓷制备及发光性能

以Y2O3为基质材料,掺杂不同含量的La3+,采用机械力化学法制备纳米粉,粉体压制后在真空度1×10-3Pa下烧结得到La3+掺杂Y2O3透明陶瓷。采用透射电子显微镜(TEM)观察粉体一次颗粒形貌,扫描电镜(SEM)观察样品表面形貌,HV-1000型维氏硬度计测定样品硬度和断裂韧性,阿基米德法测定烧结后试样的相对密度,自动记录分光光度计测定试样透过率。结果表明:制备的La3+∶Y2O透明陶瓷透光率可达80%,掺杂La3+可以显著降低La3+∶Y2O3透明陶瓷的烧结温度;随着La2O3添加量的提高,样品透光率逐渐提高,但La2O3添加量过大会造成点阵畸变严重;随着La2O3添加量的提高,样品相对密度、维氏硬度和断裂韧性均逐渐提高,最后趋于平稳;随着保温时间延长,样品透光率也逐渐增大,继续增大保温时间,透光率趋于平缓。结合样品的透光率、相对密度、维氏硬度和断裂韧性考虑可知La2O3适合掺杂量、烧结温度和保温时间分别为10at%、1550℃和3h。     

含MO（MO=FeO,NiO）的低碱度CaO-MgO-Al2O3-SiO2熔渣电导率（英文）

作为有色冶金渣中有价金属回收基础,利用电化学交流阻抗谱法,测定低碱度MO(MO=FeO,NiO)-CaOMgO-Al2O3-SiO2五元熔渣体系的电导率。结果表明:随着熔渣体系温度的升高和MO浓度的增大,熔渣电导率增大。在1573～1773K下,(CaO+MgO)与(SiO2+Al2O3)质量比为0.47,当MO浓度小于12%时,熔渣电导率为1.4～14.4S/m。随着熔渣中MO浓度的增大,熔渣电导率增大的幅度增加。当熔渣中FeO和NiO浓度小于8%时,两种熔渣的电导率相差不大;当浓度达到12%时,含FeO的熔渣电导率明显大于含NiO的熔渣电导率。随着MO浓度的增加,电导活化能降低。     

Sb掺杂对Mg_2Si基化合物热电性能的影响(英文)

采用感应熔炼和真空热压的方法制备了Sb掺杂和未掺杂的Mg2Si基热电材料.研究了Sb掺杂对Mg2Si基热电材料的结构以及热电特性的影响.结果表明:通过Sb掺杂使得载流子浓度从3.07x1019 cm-3增加到1.25x1020 cm-3,电子有效质量也相应增加.测试了从室温到800 K下试样的Seebeck系数,电导率和热导率.结果显示,0.3 at%Sb掺杂使得电导率得到显著增加,在783 K时,ZT值达到0.7.     

Nanopowder synthesis of aluminum doped cadmium oxide via sol-gel calcination processing

The structural, optical and electrical properties of undoped and Al-doped CdO powder nanostructures prepared by sol-gel calcinations method have been investigated. X-ray diffraction (XRD) results revealed that pure and Al-doped CdO have the polycrystalline with face centered cubic (FCC) structure. The crystallite size for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 17.2, 15.9, 16.1, 16.3 and 16.8 nm, respectively. The optical band gap of the samples were determined from the diffused reflectance spectra and E_g values for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 1.89, 2.07, 2.03, 2.07 and 2.12 eV, respectively. The electrical conductivities of pure and Al-doped CdO were measured in the temperature range (290-420 K) and their temperature dependence was analyzed according to Arrhenius relation. The electrical conductivity results indicate that the electrical conductivity mechanism is controlled by thermally activated processes. The results showed that sol-gel calcinations technique can be effectively used to produce undoped and doped nanopowders.     

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.     

Constitutional Design and Dielectric Properties of BST Graded Ceramics

The effect of B203 dopant and SrTiO3 (ST) content on lattice parameters and ferro-paraelectric phase transition temperature (i.e. Curie point) of Ba1-xSrxTiO3 (BST, x=0～0.4) ceramics was investigated, and then BST graded ceramics with controllable transition temperature zone were fabricated and characterized for their dielectric properties. The results show that with the increase of ST content, c/a ratio and Curie point of both doped and undoped ceramics decreased linearly but with different rate of change, resulting from different ionic radiuses of Ba^2 , Sr^2 and B^3 . Moreover, both c/a ratio and Curie point of doped BST increased slightly in comparison with that of undoped ones while the Curie point changed scarcely with dopant amount rising, which perhaps means that for BST grains with different ST content, B2O3 solubility was different but limited and most of boron (B) did not incorporate into BST grains. Through controlling composition,transition temperature of graded ceramics can be designed. For doped graded ceramics sintered at 1250℃, its dielectric properties was much better than that of undoped one sintered at 1400℃, and Curie peak of both samples was broadened effectively via graded structure.     

混杂增强(CNTs+TiB2)/Cu复合材料制备与性能

本文以碳纳米管（CNTs）和TiB2颗粒作为增强相,首先利用球磨、表面吸附和热压烧结相结合技术制备具有层叠结构的CNTs/Cu复合材料,改善了CNTs在铜基复合材料中易团聚问题。CNTs/Cu复合材料的致密度和导电率随CNTs含量增加而降低,抗拉强度和伸长率随CNTs含量增加先升高后降低,当含量为0.1 wt.%时综合性能最优,致密度、导电率和抗拉强度分别为97.57%、91.2 %IACS和252 MPa。而球磨后热压烧结的1 wt.% TiB2/Cu复合材料致密度、导电率和抗拉强度分别为97.61%、58.3 %IACS和436 MPa。在此基础上,将TiB2颗粒原位引入到具有层叠结构的CNTs/Cu复合材料,制备获得混杂增强(CNTs+TiB2)/Cu复合材料。相比单一CNTs（或TiB2）增强铜基复合材料,(CNTs+TiB2)/Cu复合材料的强度提升显著。其中,(0.1 wt.% CNTs+1 wt.% TiB2)/Cu复合材料的导电率和抗拉强度分别为56.4 %IACS和531 MPa,相比1 wt.% TiB2/Cu,其导电率仅降低3.3%,而抗拉强度则升高21.8%。这主要归因于片层间CNTs可起承担和传递载荷作用,同时片层间弥散分布的TiB2颗粒可以钉扎位错,两种强化机制共同作用使(CNTs+TiB2)/Cu复合材料的抗拉强度显著提升。     

含Ca阻燃镁合金的高温氧化行为

Ca的加人大大提高了镁合金的燃点,当Ca含量大于1.7%时,Mg-Ca合金能在1 173 K的高温下暴露于大气中30min而不燃烧.SEM和XRD分析表明:合金表面生成了主要由氧化钙和氧化镁组成的复杂氧化膜,氧化膜内侧组织主要是Mg2Ca,该氧化膜具有保护性,但薄厚不一,极不规则.高温氧化动力学研究显示:该合金在673 K和873 K氧化符合抛物线规律,而在773 K氧化遵循立方规律.热力学计算结果表明:在Mg-2.5Ca合金中从室温到1 143 K温度范围内Ca都比镁优先与氧结合生成CaO,当Ca含量降低到一定程度时,镁又与氧结合生成MgO,所以形成了MgO CaO的复合保护膜.     

The effect of sintering temperature on some properties of Cu-SiC composite

Copper matrix composites reinforced with 1 wt.%, 2 wt.%, 3 wt.% and 5 wt.% SiC particles were fabricated by powder metallurgy method. Cu and Cu-SiC powder mixtures were compacted with a compressive force of 280 MPa and sintered in an open atmospheric furnace at 900-950 °C for 2 h. Within the furnace compacted samples were embedding into the graphite powder. The presence of Cu and SiC components in composites was verified by XRD analysis. Optical and SEM studies showed that Cu-SiC composites have a uniform microstructure in which silicon carbide particles are distributed uniformly in the copper matrix. The results of the study on mechanical and electrical conductivity properties of Cu-SiC composites indicated that with increasing SiC content (wt.%), hardness increased, but relative density and electrical conductivity decreased. The highest electrical conductivity of 98.8% IACS and relative density of 98.2% were obtained for the Cu-1 wt.%SiC composite sintered at 900 °C and this temperature was defined as the optimum sintering temperature.     

Influence of the various doping elements on the microwave dielectric loss of silica

This article presents an evaluation of the influence of various doping elements on the dielectric loss of silica glass. Based on the Anderson-Stuart model, the temperature dependence of the electrical conductivity activation energy was investigated; then, comparisons of microwave dielectric loss of silica doped by various elements such as Li₂O, Na₂O, K₂O, CaO, MgO and Al₂O₃ are presented. At 1373 K, the dielectric loss of silica doped with Li₂O was found to be 10 times more than that the undoped one. The order in the impact of the doping elements on the microwave dielectric loss was found to be Li₂O > Na₂O > K₂O > MgO > CaO > Al₂O₃. This work is of importance with regard to applications that employ silica glass at conditions that involve especially high temperature and also in the microwave frequency range.