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1.
3Y-TZP/Al_2O_3复合粉末的相变研究 总被引:1,自引:0,他引:1
采用化学共沉淀法制备了 3Y -TZP/Al2 O3纳米级复合粉末 ,研究了Al2 O3含量和煅烧温度对粉末的相结构和ZrO2 晶格常数的影响 .研究表明 :80 0℃ ,1h煅烧的复合粉末只出现t-ZrO2 相 ,不出现Al2 O3的任何晶相 ,当Al2 O3质量分数不大于 10 %时 ,ZrO2 晶格常数随Al2 O3含量增加而减小 ,但当Al2 O3质量分数为 2 0 %时 ,ZrO2 晶格常数反而略有增大 ;当温度升至 12 0 0℃时 ,开始形成α -Al2 O3,Al2 O3对ZrO2 晶格常数的影响减小 ;当温度达到 14 5 0℃时 ,完成了向α-Al2 O3的转变 ,故Al2 O3不再对ZrO2 晶格常数产生影响 . 相似文献
2.
以溶胶–凝胶法制备的钛酸铝前驱体和固相合成法制备的纳米Fe2O3为原料,在不同温度煅烧保温2h制备出钛酸铝固溶体[Al2(1–x)Fe2xTiO5]。通过X射线衍射、电子探针分析并计算晶格常数和热分解率,研究了纳米Fe2O3含量以及烧成温度对烧后试样热分解性能的影响。结果表明:纳米Fe2O3很容易与Al2TiO5反应,形成固溶体,抑制钛酸铝陶瓷的热分解;随着纳米Fe2O3加入量的增加,Al2(1–x)Fe2xTiO5的晶格常数变大,热分解率降低,但当加入量超过10%时,Al2(1–x)Fe2xTiO5的晶格常数不变甚至减小,热分解率反而会增大;纳米Fe2O3作为添加剂可改善钛酸铝陶瓷的热分解性能。煅烧温度对钛酸铝的热分解率有很大影响,随着温度升高,热分解率降低,当温度大于1350℃时,钛酸铝陶瓷晶格常数保持不变,钛酸铝陶瓷的热分解率变化不大。 相似文献
3.
溶胶一凝胶法制备Al2O3一SiO2复合膜的微观结构分析 总被引:13,自引:0,他引:13
用溶胶-凝胶法制备了Al2O3-SiO2复合膜,通过XRD,FT-IR,N2吸附等手段研究化学组成和煅烧温度对复合膜的物相组成,化学结构以及微孔结构的影响,研究表明,在600℃下煅烧的合膜,随SiO2组分的减少,其物相从单纯无定形态演化为无定形态与γ-Al2O3纳米晶共存,比表面积从484.4m^2/g减小到197.7m^2/g,孔体积炎0.337cm^3/g减小到0.165cm^3/g,主要孔径范围2-4nm,微孔占总孔体积的17%-59%,当煅烧温度从200℃升高到1100℃,复合膜经历无定形态+γ-A1OOH,无定形态+γ-Al2O3到α-Al2O3+莫来石的晶相转变过程并逐渐致密化,比表面积和孔体积减小,孔径分布从双峰分布(200-600℃)变为单峰分布(800℃),孔隙在1100℃完全消失。 相似文献
4.
以ZrOCl2·8H2O和Y2O3为主要原料,采用醇-水溶液加热结合共沉淀法制备出Y2O3稳定的纳米ZrO2复合粉体.利用X射线衍射(XRD)分析和扫描电子显微镜(SEM)研究了复合粉体的物相组成和晶粒大小.结果显示,当Y2O3含量为2mol%时,复合粉体由单斜相ZrO2和少量四方相ZrO2组成;当Y2O3含量为3mol%、4mol%时,粉体全部由四方相ZrO2,组成.750℃~900℃煅烧时,复合粉体的物相组成变化不大,但四方相ZrO2,的晶粒尺寸随煅烧温度升高而增大. 相似文献
5.
以Al(OH)3和ZrOCl2·8H2O为起始原料,以NH4HCO3为沉淀剂,在醇-水混合溶液中获得前驱体,将前驱体在空气中煅烧,制备了Al2O3-ZrO2复合粉体.探讨了不同煅烧温度对Al2O3-ZrO2复合粉体的物相组成和显微形貌的影响.采用综合热分析仪、X-射线衍射仪、扫描电镜等手段对粉体进行表征.结果表明:前驱体中含锆化合物主要以无定形的形式存在,当煅烧温度为600℃时,粉体中出现较强的t-ZrO2衍射峰,Al(OH)3的衍射峰肖失.当煅烧温度增加到1200℃时,粉体中主要存在α-Al2O3和t-ZrO2主晶相衍射峰.前驱体经600℃热处理后所制备的Al2O3-ZrO2复合粉体粒度分布均匀且大多数颗粒在50 ~ 100 nm之间;随着煅烧温度的升高,Al2O3-ZrO2复合粉体颗粒出现长大,且其显微形貌由球状颗粒为主逐渐向球状、片状以及短棒状等多样化结构过渡. 相似文献
6.
采用引入晶种的水热合成法制备α—Al3O3纳米粉 总被引:10,自引:1,他引:9
采用水热合成法制备α-Al3O3微粉时,水热处理温度需要在大于450℃下才能进行,这在工艺上难以实现,但引入与α-Al3O3具有等结构的晶种,可以增加成核密度,提高成核速率,降低成核的活化能,从而降低相变温度,使水热处理温度降低到200℃以下,并使粉末的煅烧温度降到930℃,实验结果表明,采用添加4%(inmass)α-Al3O3晶种的水热合成法制备的α-Al3O3为粒度分布均匀、颗粒近似球形的纳米级(68nm)的粉末。 相似文献
7.
以Si3N4和BN粉末为原料,Si3N4-BN复合粉末中BN的体积分数分别选定为10%、20%和30%,采用质量分数为2%的Al2O3和6%的Y2O3作为烧结助剂,分别在1500、1600和1650℃,压力50 MPa,保温5 min的条件下,采用放电等离子体烧结法制备了致密Si3N4-BN复合陶瓷。XRD结果和SEM分析表明:当煅烧温度为1650℃时,复合陶瓷中的α-Si3N4已完全转变为β-Si3N4;BN的加入抑制了复合陶瓷中Si3N4晶粒的生长而使结构细化;复合陶瓷的维氏硬度和断裂韧性随BN含量的增加而逐渐降低。 相似文献
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以板状刚玉、电熔白剐玉、工业Cr2O3微粉和金属Al粉为原料,热固性酚醛树脂为结合剂,在1 450℃保温6h埋炭烧成获得添加过渡相的Al-Al2O3复合滑板.结果表明:Cr2O3微粉在l450℃保温6h埋炭烧成后不能稳定存在,会转变为Cr3C2、Cr7C3或Al8Cr5铝铬金属间化合物,其存在状态由其添加量决定.复合滑板中(Al2OC)1-x(AlN)x、Al4O4C、Cr3C2及Cr7C3为增强相,Al8Cr5铝铬金属间化合物为塑性相.当Cr2O3微粉含量为3%(质量分数)时,复合滑板的组成为Al-Al4O4C-Al2O3;当添加Cr2O3微粉为6%、9%和12%时,复合滑板的组成为Al8Cr5-(Al2OC)1-x(AlN)x-Al2O3;当添加Cr2O3微粉为15%时,复合滑板的组成为Al8Cr5-Al2O3.当Cr2O3微粉含量为6%时,Al8Cr5-(Al2OC)1-x(AlN)x-Al2O3复合滑板物理性能最佳.在1 450℃保温6h埋炭烧成条件下,Cr2O3微粉表现为过渡相. 相似文献
10.
以异丙醇铝为原料,用聚乙二醇(PEG1000)络合溶胶-凝胶法合成了Al2O3纳米晶,并采用差热-热重分析、X射线衍射、透射电子显微镜等对络合前驱体及粉体进行表征;探讨了PEG1000及煅烧温度对纳米Al2O3相结构、粒子尺寸、形貌及分散性的影响规律.结果表明:PEG1000增强了纳米Al2O3粒子的分散性.干凝胶在600~900℃煅烧后得到γ-Al2O3相;在600℃煅烧条件下,得到γ-Al2O3粒子形貌为针状结构,长度约为50~60nm.随着煅烧温度的升高,γ-Al2O3针状粒子长度逐渐减小,在750℃煅烧后,得到γ-Al2O3粒子长度为20~30nm;在900℃煅烧条件下,γ-Al2O3粒子形貌为颗粒状,平均粒径尺寸为10nm;当干凝胶在1 000℃煅烧后得到θ-Al2O3和α-Al2O3的混合相,所得粒子平均粒径尺寸为20 nm;当干凝胶在1 200℃煅烧后,得到的Al2O3全部转化α-Al2O3相,制得的纳米Al2O3粒子尺寸均一且分散性良好. 相似文献
11.
采用固相法制备了 Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3–BaTiO3–SrTiO3(NBT–KBT–BT–ST)陶瓷,该体系是按(1–2x)(0.8NBT–0.2KBT)–x(0.94NBT–0.06BT)–x(0.74NBT–0.26ST) (x = 0.10、0.20、0.25、0.30、0.35、0.40、0.45)组合而成的,研究了该系陶瓷的结构与电性能。结果表明:所有样品都处于三方–四方准同型相界区域。该系陶瓷在准同型相界附近表现出了优异的压电性能,压电常数 d33、机电耦合系数 kp和剩余极化强度 Pr随 x 的增加先升高后降低,其中 x=0.35 陶瓷的电性能最佳:d33= 210 pC/N,kp= 0.319,Pr= 39.3 μC/cm2,Ec= 20.2 kV/cm,是一种良好的无铅压电陶瓷候选材料。依据准同型相界组成的线性组合规律来寻找具有优异压电性能的 NBT–KBT–BT–ST 陶瓷准同型相界组成是可行的。 相似文献
12.
Graphite trifluoromethylsulfate C12SO3CF3, a new binary graphite salt is formed by the irreversible solvolysis of C8SO3F in a large excess of trifluoromethylsulfuric acid. The salt is identified as a stage one intercalation compound with a C0 value of 8.12 Å and characterised by microanalysis, epr and 19F NMR spectroscopy. Both Raman spectra, in the back scattering configuration, and IR spectra, in transmission as well as reflection geometries, are used to support an ionic formulation as C12+SO3CF3?. 相似文献
13.
The complex perovskite oxide Ba(Zn1/3Nb2/3)O3 (BZN) has been studied for its attractive dielectric properties which place this material interesting for applications as multilayer ceramics capacitors or hyperfrequency resonators. This material is sinterable at low temperature with combined glass phase–lithium salt additions, and exhibits, at 1 MHz very low dielectric losses combined with relatively high dielectric constant and a good stability of this later versus temperature. The 2 wt.% of ZnO–SiO2–B2O3 glass phase and 1 wt.% of LiF-added BZN sample sintered at 900 °C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant ?r of 39, low dielectrics losses (tan(δ) < 10−3) and a temperature coefficient of permittivity τ? of 45 ppm/°C−1. The 2 wt.% ZnO–SiO2–B2O3 glass phase and 1 wt.% of B2O3-added BZN sintered at 930 °C exhibits also attractive dielectric properties (?r = 38, tan(δ) < 10−3) and it is more interesting in terms of temperature coefficient of the permittivity (τ? = −5 ppm/°C). Their good dielectric properties and their compatibility with Ag electrodes, make these ceramics suitable for L.T.C.C applications. 相似文献
14.
A solid state metathesis approach has been applied to synthesize perovskite oxides such as BaTiO3, PbTiO3, K0.5Bi0.5TiO3 and Na0.5Bi0.5TiO3, these were characterized by powder XRD, IR and energy dispersive spectra (EDS). Potassium titanium oxalate and metal chlorides are used as the starting materials. X-ray analysis shows the formation of a single phase with tetragonal structure for BaTiO3, PbTiO3, K0.5Bi0.5TiO3 and a monoclinic structure for Na0.5Bi0.5TiO3. The Infrared spectra of these compounds show the characteristic band due to Ti–O octahedron for all the compounds. The EDS spectra show the relative ratio of the metal ions. The morphology of synthesized compounds was obtained from SEM measurements. 相似文献
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综述了Al2O3包覆LiNi(1/3)Co(1/3)Mn(1/3)O2锂离子电池正极材料的研究现状与进展,并评述了其制备方法和包覆改性;讨论了包覆改善该正极材料性能的机理;提出了这种正极材料的研发过程中的一些问题并对其未来的发展前景作了展望。 相似文献
17.
A novel method to improve the cycling performance of LiCo1/3Ni1/3Mn1/3O2 in lithium-ion batteries by 1.0 wt.% CeO2-coating is presented in this work. The crystalline structure and morphology of the synthesized powder have been characterized by XRD, SEM, TEM and their electrochemical performances were evaluated by CV, EIS and galvonostatic charge/discharge tests. It is found that CeO2 forms a layer on the surface of LiCo1/3Ni1/3Mn1/3O2 without destroying the crystal structure of the core material. Electrochemical test indicates that CeO2-coating could improve the cycling performance of LiCo1/3Ni1/3Mn1/3O2. At room temperature, the capacity retention of 1.0 wt.% CeO2-coated material is 93.2% after 12 cycles at 3.0 C while that of the bare sample is only 86.6%. ICP-OES proves the coating layer could protect the dissolution of the transition metal ions from LiCo1/3Ni1/3Mn1/3O2. From the analysis of EIS, the improvement of cycle ability could be attributed to the suppression of the reaction between cathode and electrolyte. 相似文献
18.
Ichiro Fujii Shin Ariizumi Shintaro Ueno Chikako Moriyoshi Yoshihiro Kuroiwa Satoshi Wada 《Ceramics International》2018,44(9):10657-10662
We fabricated xBaTiO3 (BT)/(1-x)[BaTiO3-Bi(Mg1/2Ti1/2)O3-BiFeO3] (BT-BMT-BF)?+?0.1?wt%MnCO3 composites by spark plasma sintering and investigated the effect of BT content x, BT powder size, and BT-BMT-BF composition on piezoelectric properties. For xBT/(1-x)(0.3BT-0.1BMT-0.6BF) +?0.1?wt%MnCO3 (x?=?0–0.75) composites with a 0.5-µm BT powder, the dielectric constant was increased with x, and the relative density was decreased at x?=?0.67 and 0.75, creating optimum BT content of x?=?0.50 with a piezoelectric constant d33 of 107?pC/N. When a larger 1.5-µm BT powder was utilized for the composite with x?=?0.50, the d33 value increased to 150?pC/N due to the grain size effect of the BT grains. To compensate for a compositional change from the optimum 0.3BT-0.1BMT-0.6BF due to partial diffusion between the BT and 0.3BT-0.1BMT-0.6BF grains, a 0.5BT/0.5(0.275BT-0.1BMT-0.625BF)?+?0.1?wt%MnCO3 composite with the 1.5-µm BT powder was fabricated. We obtained an increased d33 value of 166?pC/N. These results provided a useful composite design to enhance the piezoelectric properties. 相似文献
19.
WO3/Nb2O5-supported samples prepared by impregnation are characterised by X-ray diffraction (XRD), Raman spectroscopy and X-ray absorption spectroscopy (XAS) at the W–L3 absorption edge, as well as temperature programmed reduction (TPR) and FT-IR monitoring of pyridine adsorption. Results are compared with those obtained for WO3/Al2O3 samples prepared in the same conditions, showing that niobia is able to disperse tungsta better than alumina does. Formation of a crystalline WO3 needs larger tungsten contents on niobia than on alumina, since tungsten solution into niobia is easier than into alumina. Raman and XAS spectra recorded under ambient conditions suggest that similar WOx species are formed on both supports at tungsten contents 0.5–1 theoretical monolayers; however, TPR results for the low tungsten loaded samples indicate that, when reduction starts (always at temperatures higher than 700 K under H2/Ar flow) there is a larger concentration of tetrahedral [WO4] species on alumina, than on niobia. Samples with low tungsten loading have been tested in isopropanol decomposition and ethylene oxidation, following both processes by FT-IR of adsorbed species up to 673 K. Results show that adsorption of ethylene on WO3/Nb2O5 yields acetaldehyde and acetate at 473 K, while this adsorption is non-reactive either on the supports or on WO3/Al2O3. Isopropanol adsorbs dissociatively on both supports, leading to acetone and propene formation on tungsta–niobia, but only propene on tungsta–alumina, probably due to the larger reducibility of the tungsten-containing phases. 相似文献
20.
Sintering kinetics of the system Si3 N4-Y2O3 -Al2 O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si3 N4 were studied with additions of 4 to 17 wt% Y2 O3 and 4 wt% A12 O3 . Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si3 N4 and glass or β '-Si3 N4 , α '-Si3 N4 , and glass. The compositions and amounts of the residual glassy phases are estimated. 相似文献