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1.
Spark Plasma Sintering (SPS) of NASICON Ceramics 总被引:1,自引:0,他引:1
Ji-Sun Lee Chae-Myung Chang Young IL Lee Jong-Heun Lee Seong-Hyeon Hong 《Journal of the American Ceramic Society》2004,87(2):305-307
Spark plasma sintering (SPS) method was used to obtain dense NASICON ceramics with a high-electrical conductivity, which was compared with conventional solid-state sintering. The fully dense NASICON was achieved at a relatively low-sintering temperature of 1100°C, whereas the apparent density of the specimen prepared by conventional sintering was 74% of the theoretical density. The highest conductivity of 1.8 × 10−3 Scm−1 at 25°C, which is comparable to the best value reported, was achieved using the SPS process. Considering the phase, density, and microstructure, it appears that there is more room for improved conductivity by controlling the amount of monoclinic zirconia and the resistive grain-boundary glass phase. 相似文献
2.
Fabrication of Dense Nanostructured Silicon Carbide Ceramics through Two-Step Sintering 总被引:3,自引:1,他引:3
Young-Il Lee Young-Wook Kim Mamoru Mitomo Doh-Yeon Kim 《Journal of the American Ceramic Society》2003,86(10):1803-1805
SiC powder compacts were prepared with Al2 O3 , Y2 O3 , and CaO powders. By two-step sintering, fully dense nanostructured SiC ceramics with a grain sizes of ∼40 nm were obtained. The grain size–density trajectories are compared with those of conventional sintering processes. 相似文献
3.
Grain growth in a high-purity ZnO with systematic additions of Sb2 O3 from 0.29 to 2.38 wt% was studied for sintering in air from 1106° to 1400°C. The results are discussed and compared with previous studies of pure ZnO and ZnO with Bi2 O3 additions in terms of the kinetic grain growth expression: Gn – Gn 0 = K 0 t exp(— Q/RT ). Additions of Sb2 O3 inhibited the grain growth of ZnO and increased the grain growth exponent ( n -value) to 6 from 3 for pure ZnO and 5 for the ZnO—Bi2 O3 ceramic. The apparent activation energy for the grain growth of ZnO also increased to about 600 kJ/mol from 220 kJ/mol for pure ZnO and 150 kJ/mol for the ZnO—Bi2 O3 ceramics. Both the grain growth exponent and the activation energy were independent of the Sb2 O3 content. Particles of the Zn7 Sb2 O12 spinel were observed on the grain boundaries and at the grain triple point junctions. It was also observed that the Sb2 O3 additions caused twin formation in each ZnO grain. It is concluded that both the Zn7 Sb2 O12 particles and the twins are responsible for the ZnO grain growth inhibition by Sb2 O3 . 相似文献
4.
Fabrication of Transparent Lead Lanthanum Zirconate Titanate Ceramics from Fine Powders by Two-Stage Sintering 总被引:1,自引:1,他引:1
Transparent lead lanthanum zirconate titanate (PLZT) ceramics were fabricated from fine powders using an inexpensive two-stage sintering technique. The powders were prepared by hydrolysis from low-cost inorganic precursors. In the two-stage sintering method, uniaxially pressed green pellets were densified to nearly theoretical values in an oxygen gas atmosphere during the first-stage sintering, at 1000°C for 1 h, and then residual, free lead oxide in the pellets was removed by second-stage sintering at 1100°C for 12 h. Transparent ceramic with an average grain size of 1.6 μm and a porosity of 1.3% was obtained. The transparency and dielectric characteristics of the present samples were compared with those of hot-pressed samples: The study of the polarization–field hysteresis loops of the present samples yielded a remanent polarization of 6.8 μC/m2 and a coercive field of 1.6 kV/cm. The low coercive field of PLZT ceramics could potentially reduce the driving voltage of electrooptic devices in many applications. 相似文献
5.
A stereological method has been used to determine the degree of grain boundary-pore contact during sintering of Al2 O3 . Al2 O3 doped with 200 ppm MgO exhibits a degree of contact of 5.7 times that expected from random intersections with pores, while pure Al2 O3 shows a pore contact factor of 4.8. These data are larger than the values of 2.8 for sintered or hot-pressed UO2 , computed from published data, and values of 1.7 and 1.8 for sintered W and Cu powders, respectively. The degree of grain boundary-pore contact for each material remains constant throughout densification from pressed powder to near full density. 相似文献
6.
IVAN B. CUTLER 《Journal of the American Ceramic Society》1969,52(1):14-17
Analytical expressions for the initial sintering of glass powders were developed to describe shrinkage of powder compacts at a constant rate of heating. Data describing sintering of soda-lime glass spheres as measured by shrinkage of powder compacts at rates of heating from 0.46 to 2.91°C/min are consistent with the model analytical expressions. Compacts of glass spheres decreased in size exponentially with increasing temperature as predicted by the model. 相似文献
7.
以纳米h-BN和Si C粉为原料、B2O3为烧结助剂,利用放电等离子烧结(SPS)制备h-BN-Si C复相陶瓷,研究了烧结压力(20~50 MPa)对h-BN-Si C复相陶瓷结构与力学性能的影响。结果表明:在不同烧结压力下,h-BN-Si C复相陶瓷中h-BN晶粒的c轴倾向于平行压力方向,增大烧结压力能够提高复相陶瓷的致密化和力学性能,但较大的烧结压力(40 MPa)降低了c轴倾向于平行压力方向的取向度和断裂韧性。在40 MPa烧结压力时获得了较佳的综合性能,复相陶瓷的相对密度、抗弯强度和断裂韧性分别达到98%、289.2 MPa和3.45 MPa·m1/2,比同条件制备的纯h-BN陶瓷的抗弯强度和断裂韧性分别提高了约138.4%和64.3%。复相陶瓷断裂为典型的沿晶断裂模式,微裂纹及裂纹偏转提高了复相陶瓷的断裂韧性。 相似文献
8.
Jing Liu Zhijian Shen Mats Nygren Bo Su Tim W. Button 《Journal of the American Ceramic Society》2006,89(9):2689-2694
Nano-powders of BaTiO3 , SrTiO3 , Ba0.6 Sr0.4 TiO3 (BST64), and a mixture of the composition (BaTiO3 )0.6 (SrTiO3 )04 with particle sizes in the range of 60–80 nm were consolidated by spark plasma sintering (SPS). An experimental procedure is outlined that allows the determination of a "kinetic window," defined as the temperature interval within which the densification process can be kinetically separated from the grain growth one, enabling preparation of dense nanostructured ceramics. The width of this window varied from almost zero for BST64 to 125°C for the (BaTiO3 )0.6 (SrTiO3 )0.4 mixture. During the densification (sintering) of the (BaTiO3 )0.6 (SrTiO3 )04 mixture, BST64 is formed. The main part of this reaction occurs in a fully densified body through which suggesting that the constitutional phase(s) have a self-pinning effect on the grain growth. 相似文献
9.
《硅酸盐学报》2016,(2)
以蓟县锰方硼石重选尾矿为主要原料,采用低温烧结制备以单斜辉石为主晶相的微晶玻璃,探讨焙烧制度以及粉体粒径对微晶玻璃性能的影响。采用差热分析、X射线衍射分析和扫描电子显微镜观测等测试手段,对不同条件下制备的微晶玻璃样品性能、晶体结构和显微形貌变化进行了研究,分析了影响样品性能的主要因素以及尾矿中残余锰方硼石促进低温烧结微晶玻璃的机理。结果表明:当烧结温度为890℃时,形成直径约0.1~0.5μm、长度1~2μm,表面较平整的四方柱状结构的单斜辉石晶体。该微晶玻璃样品的抗折强度随着粉体粒径的减小而提高,当粉体的粒径d90达到5.71μm时,样品的抗折强度达128 MPa。尾矿中剩余的锰方硼石矿物是大幅度降低微晶玻璃烧结温度的关键成分。 相似文献
10.
T. K. GUPTA 《Journal of the American Ceramic Society》1972,55(5):276-277
11.
Structure and Grain Coarsening During the Sintering of Alumina 总被引:2,自引:0,他引:2
The pore surface area ( S p ) and grain-boundary area ( S gb ) were measured during the sintering of undoped and doped (100 ppm MgO) alumina compacts. Since the presence of the additive affects only S gb (raising it at a given value of the density), pinning of the boundaries by solid-solution drag is the only additive function evidenced by the results. The importance of such pinning even at densities as low as 75% of theoretical is linked to the existence of microstructural inhomogeneities. 相似文献
12.
Xingyuan Guo Ping Xiao Jing Liu Zhijian Shen 《Journal of the American Ceramic Society》2005,88(4):1026-1029
Hydrothermal synthesis has been used to produce hydroxyapatite (HA) particles with high crystallinity. Such particles of nanorods were used to fabricate HA ceramic by using spark plasma sintering. X-ray diffraction, transmission electron microscope, scanning electron microscope, and the BET method have been used to examine crystallite size, crystallite shape, and the surface area of particles, and grain size of sintered HA ceramics. It was found that the morphology of the nanorods in the HA particles changed to a more equiaxed shape during sintering. 相似文献
13.
随着人们环保意识的增强,对环境质量的要求也愈来愈高。在城市生活污泥处理上,人们给予的关注程度逐渐提升。城市污泥主要来源于城镇集中式生活污水处理厂,其含有大量的无法消除的重金属元素以及大量的细菌和病原体等,对其进行科学地利用,有助于减少城市二次污染的产生。我国污泥处理技术处于探究阶段,处理方法的科学技术含量较低,因此,创新污泥处理方法,减少城市污染,对于推动城市的可持续发展具有重要的意义。文章对污泥烧结制陶粒技术进行研究,对处理技术的可行性进行分析,使污泥达到无害化、减量化、资源化,为创建绿色生态家园提供可参考的理论依据。 相似文献
14.
Mohamad A.A. Attia Roberto Orrù Francesco Delogu Selena Montinaro Sebastiano Garroni Emad M.M. Ewais Giacomo Cao 《Journal of the American Ceramic Society》2015,98(5):1453-1459
The effects produced by annealing Y2O3 nanopowders on their spark plasma sintering (SPS) behavior are systematically investigated in this work. It is found that the annealed powders display higher sinterability with respect to the as‐received ones. Indeed, the maximum densification level reached from pristine powders is about 97.5%, whereas density decreases when further increasing either the sintering temperature or the dwell time. In contrast, the density of SPS products obtained from pretreated powder monotonically increases with temperature and processing time, thus leading to fully dense materials in 30 min at 1050°C and 60 MPa. Correspondingly, it is found that the annealing treatment markedly inhibits grain coarsening during SPS. Thus, dense translucent samples with grain size below 100 nm can be attained from annealed powders. On the other hand, white‐opaque specimens with significantly coarser microstructures (up to 1‐μm‐sized grains) are obtained when pristine powders are directly processed under the same sintering conditions. Furthermore, it is observed that the annealing treatment of SPS samples in air allows for graphite contamination removal, whereas no improvement in term of light transmittance is produced. 相似文献
15.
Liang A. Xue 《Journal of the American Ceramic Society》1989,72(8):1536-1537
Free-energy analyses performed on closed particle-pore arrays show that the presence of an abnormal grain thermodynamically favors the shrinkage of large pores to which is is adjacent. This gives an explanation to the experimentally observed phenomenon of abnormal-grain-growth-promoted densification in barium titanate. 相似文献
16.
M. Mitomo M. Tsutsumi H. Tanaka S. Uenosono F. Saito 《Journal of the American Ceramic Society》1990,73(8):2441-2445
The microstructures of gas-pressure-sintered materials from β-Si3 N4 powder were characterized in terms of the diameter and aspect ratio of the grains. The size distributions of diameters in materials fabricated by heating for 1 h at 1850° to 2000°C were nearly constant when they were normalized by average diameters because of normal grain growth. The rate-determining step in the densification and grain growth was expected to be the diffusion of materials through the liquid phase. The activation energy for grain growth was 372 kJ/mol. The average aspect ratio of the grains was 3 to 4, whereas that of large grains was smaller because of shape accommodation. The fracture toughness was about the same as that of material from α-Si3 N4 powder despite the smaller aspect ratio of the grains 相似文献
17.
18.
ZnO ceramics used as varistors are prepared with bismuth oxide as an essential additive. Some of its effects during the first step of liquid-phase sintering remain unexplained. Therefore, in this work, we characterize the Bi distribution and identify the Bi-rich phases in spherical Bi-chemically-doped ZnO powders. By a suitable method of differential thermal analysis conducted during sintering, we detect thermal phenomena. Characterization of ceramics quenched during sintering allows us to describe them and to analyze their influence on sintering. We also study the parameters which determine the occurrence of these events during sintering. 相似文献
19.
Zirconia–titanium (ZrO2 –Ti) composites have been considered potential thermal barrier graded materials for applications in the aerospace industry. Powder mixtures of Ti and 3 mol% Y2 O3 partially stabilized ZrO2 in various ratios were sintered at 1500°C for 1 h in argon. The microstructures of the as-sintered composites were characterized by X-ray diffraction and transmission electron microscopy/energy-dispersive spectroscopy. Ti reacted with and was mutually soluble in ZrO2 , resulting in the formation of α-Ti(O, Zr), Ti2 ZrO, and/or TiO. These oxygen-containing phases extracted oxygen ions from ZrO2 , whereby oxygen-deficient ZrO2 was generated. For relatively small Ti/ZrO2 ratios, specimens with ≤30 mol% Ti, TiO were formed as oxygen could be sufficiently supplied by excess ZrO2 . For the specimens with ≥50 mol% Ti, lamellar Ti2 ZrO was precipitated in α-Ti(Zr, O), with no TiO being found. Both m -ZrO2− x and t -ZrO2− x were found in specimens with ≤50 mol% Ti; however, only c -ZrO2− x was formed in the specimen with 70 mol% Ti. As ZrO2 was gradually dissolved into Ti, yttria was retained in ZrO2 because of the very limited solubility of yttria in α-Ti(O, Zr) or TiO. The concentration of retained yttria and the degree of oxygen deficiency in ZrO2 increased with the Ti content. The complete dissolution of ZrO2 into Ti was followed by the precipitation of Y2 Ti2 O7 in the specimen with 90 mol% Ti. 相似文献
20.
Rapid Prototyping of Piezoelectric Ceramics via Selective Laser Sintering and Gelcasting 总被引:5,自引:0,他引:5
Dong Guo† Long-tu Li Kai Cai Zhi-lun Gui Ce-wen Nan 《Journal of the American Ceramic Society》2004,87(1):17-22
This article presents a new lost mold rapid prototyping method which combines selective laser sintering (SLS) and gelcasting techniques for fabricating piezoelectric ceramics. SLS was used to fabricate sacrificial molds of the desired structure of the ceramic part. Then aqueous PZT (lead zirconate titanate) suspension was cast in the mold and solidified in situ through formation of a three-dimensional network gel. Because the polymer mold can be easily removed at the initial stage of sintering and the gelcast PZT body has a high green strength, the desired geometry of the PZT part can be completely retained after sintering of the ceramics. Complex-shaped PZT parts were successfully fabricated after using concentrated PZT suspension with low viscosity. Densities and electrical properties, such as the d 33 , the relative permittivity ε, the dielectric loss tg δ and the electromechanical coupling factor K p of the gelcast PZT parts were also compared with those of the die-pressed PZT samples. The results indicated that the gel-forming process did not deteriorate the electrical properties of the samples, if proper dispersant was selected in developing concentrated ceramic slurry. 相似文献