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1.
In the present work, the effects of two different morphologies of zinc oxide nanoparticles (nanosheets and nanorods) were investigated by in-situ measurement of deposition weight, and current density. ZnO nanosheets and nanorods were synthesized by microwave-assisted method using co-surfactant route. The average thickness of obtained nanosheets, and the average diameter of nanorods were measured to be about 26 nm and 139 nm, respectively. ZnO films were obtained by electrophoretic deposition from suspension of nanoparticles in ethanol under different voltages. Results indicated that ZnO nanosheets tend to have greater deposition rate than ZnO nanorods under similar conditions. The compactness of the film obtained from nanosheet suspension was higher than the one obtained from nanorod suspension. However, the film obtained from ZnO nanorods displayed more uniformity at different voltages in comparison to the film obtained from ZnO nanosheets, which can be due to different active surface area, and also different way of motion under hydrodynamic forces in the suspension. 相似文献
2.
《Ceramics International》2019,45(14):17382-17386
High-density ZnO ceramics were prepared by a Two-Step Cold Sintering Process (TS-CSP) at an ultralow-temperature. The densification process of ZnO ceramics was demonstrated by TS-CSP. And the density, microstructure and electrical properties of the ZnO ceramics were investigated. The results indicate that most of the crystallization of ZnO ceramic can be completed in the first step of sintered at 150 °C/200 MPa for 30 min, with a relative density approaching 97.36%. This relative density was further improved to 99.43% after the second sintering step was deployed at 200 °C/200 MPa for 30 min, which displayed an average grains size of 1.5 μm and resistivity of 0.125 Ω cm. This work demonstrated an effective method to reduce CSP temperature and pressure in the production of high-performance ZnO ceramics. 相似文献
3.
ZnO nanowires with a periodic instability of diameter were successfully prepared by a thermal physical vapor deposition method.
The morphology of ZnO nanowires was investigated by SEM. SEM shows ZnO possess periodic bead-like structure. The instability
only appears when the diameter of ZnO nanowires is small. The kinetics and mechanism of Instability was discussed at length.
The appearance of the instability is due to negative feed-back mechanism under certain experimental conditions (crystallization
temperature, vapor supersaturation, etc). 相似文献
4.
《Journal of the European Ceramic Society》2020,40(5):1896-1901
BaTiO3:100xZnO composite ceramics with different ZnO particle sizes were prepared by using a conventional solid-state method. Phase constitution, microstructure and dielectric properties of BaTiO3:100xZnO composite ceramics are investigated. Compared to micrometer scaled ZnO particles, nanometer scaled ZnO particles tend to agglomerate at lower ZnO contents in the BaTiO3:100xZnO composite ceramics. The introduction of ZnO in BaTiO3 leads to the reduction of grain size, decrease of the tetragonality and shift of phase transition temperature. The optimum composition is BaTiO3 with 20 wt. % nanometer scaled ZnO particles, which has stable permittivity and low dielectric loss from -100 to 160 °C. The stable dielectric properties are proposed to be beneficiated from the stress induced multi-phase coexistence. 相似文献
5.
脉冲激光沉积技术(PLD)目前已成为一种重要的制备氧化锌(ZnO)薄膜的技术,但是由于脉冲瞬间沉积时不能避免产生液滴及形成大小不一的颗粒,因此在制备高质量ZnO薄膜的表面均匀性方面还存在一定弊端。文章采用PLD(KrF准分子激光器:波长248 nm,频率5 Hz,脉冲宽度20 ns)方法在衬底温度450℃和氧气流量10 sccm下以高纯ZnO为靶材、在单晶硅衬底表面沉积120 min成功生长了ZnO薄膜。扫描电子图像(SEM)显示ZnO薄膜表面有明显凸起的颗粒,文章通过俄歇能谱仪对ZnO薄膜进行了研究,分析了ZnO薄膜的表面成分及凸起颗粒微观区域的成分。实验结果表明制备的ZnO薄膜表面明显突起的颗粒为ZnO颗粒,文章为PLD法制备ZnO薄膜易形成大小不一的颗粒提供了理论依据。 相似文献
6.
ABSTRACTIt is difficult to dope Al into main grains of ZnO varistor ceramics, especially for small doping amount. Generally, all raw materials including Al dopant are directly mixed together and sintered into ceramics. However, in this direct doping process, Al is apt to stay in grain boundaries, and almost does not enter grains. This does harm to the electrical properties of ZnO varistors. In this paper, we proposed a two-step doping process. Al2O3 powder was first mixed only with a part of the ZnO powder and pre-sintered. The pre-sintered powder was mixed with other additives such as Bi2O3 and the rest ZnO. Then ZnO varistor ceramics were prepared via solid state sintering processes. Results showed that two-step doped ZnO varistors exhibited improved electrical properties with a significant increased nonlinear coefficient and a great decreased leakage current compared to directly doped ones because more Al was incorporated into ZnO grains. 相似文献
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8.
《Ceramics International》2020,46(3):3023-3027
The dense NaZr2(PO4)3 (NZP) ceramics were successfully prepared by a microwave sintering process with x wt.% ZnO as a sintering aid (where x = 0, 0.5, 1.0, 2.0 and 3.0). The effects of ZnO additive on the crystal structure, microstructure and sintering behavior of as-prepared NZP ceramics were systematically investigated. The single NZP phase can be achieved in the wide temperature range of 900–1200 °C holding for 2 h by microwave-sintering technology. The addition of ZnO sintering aid would not noticeably change the crystal structure of NZP. Importantly, ZnO additive significantly promoted the densification and 1.0 wt% ZnO-added sample possessed the maximum relative density of 96.5% after sintering at 1100 °C, considerably higher than that of pure NZP sample. Besides, the Vickers hardness of the above sample could attain near 800 MPa, which is about four times as hard as the pure NZP ceramics without ZnO additive. It was suggested that the combination of microwave sintering with appropriate addition of ZnO sintering aid would provide a convenient and efficient method for rapid fabrication of dense NZP ceramics. 相似文献
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10.
This research was conducted in order to study the effect of ZnO nanoparticulate addition on the properties of 0.9 Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 [PMNT] ceramics. The PMNT ceramics were prepared by a solid-state reaction. The ZnO nanoparticles were added into PMNT ceramics
to form PMNT/xZnO (x = 0, 0.05, 0.1, 0.5, and 1.0 wt.%). The PMNT/xZnO ceramics were investigated in terms of phase, microstructure, and mechanical and electrical properties. It was found that
the density and grain size of PMNT ceramics tended to increase with an increasing amount of ZnO content. Moreover, a transgranular
fracture was observed for the samples containing ZnO, while pure PMNT ceramics showed only a intergranular fracture. An addition
of only 0.05 wt.% of ZnO was also found to enhance the hardness and dielectric and ferroelectric properties of the PMNT ceramics. 相似文献
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12.
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
13.
Ke Gan Yanjiao Gai Yali Wang Jie Cui Yuju Lu Xiaoyan Zhang Jingjing Liu Jie Xu Jinlong Yang 《International Journal of Applied Ceramic Technology》2020,17(1):274-284
A direct coagulation casting method for silicon carbide ceramic suspension using dispersant crosslink reaction is reported. Polymer electrolyte (polyethyleneimine, PEI) was used as dispersant to prepare silicon carbide suspension. Common food additives (carboxymethyl cellulose, CMC) were used to coagulate the electrosteric stabilized silicon carbide suspension. There was a well disperse silicon carbide suspension with 0.2 wt% PEI at pH = 5-6. Influence of coagulant on viscosity and zeta potential of the silicon carbide suspension was investigated. It indicates that the high solid loading silicon carbide suspension can be destabilized and coagulated at elevated temperature. It can be attribute to the gradual decrease of electrosteric force due to the crosslink reaction between PEI and CMC. Silicon carbide wet green body with compressive strength of 1.99 MPa could be demolded at 70°C which is higher than that prepared by traditional DCC and dispersant reaction method for nonoxide ceramics. Dense silicon carbide ceramics with relative density above 98.8% and 99.3% had been prepared by liquid phase pressureless and hot pressed sintering, respectively. 相似文献
14.
Yuan-Chung Wang Ing-Chi Leu † Min-Hsiung Hon 《Journal of the American Ceramic Society》2004,87(1):84-88
An integrated process combining the preparation of ZnO nanoparticles and the formation of ZnO coatings using electrophoretic deposition (EPD) is reported. The work focuses on the deposition kinetics of nanocrystalline ZnO coatings on copper electrodes during EPD by direct measurement of the thickness of the deposited layer. The experimental results show that the EPD process is a powerful route to fabricate uniform coatings with desired thickness and excellent surface smoothness, which might be attributed to small particle size and narrow size distribution. On the other hand, the deposition kinetics changes with applied voltage and deposition time. The deposition thickness increases with increasing applied voltage and deposition time. In a short deposition time, the deviation of deposition rate between the theoretical and experimental values is caused by voltage drops during deposition, and the discrepancy increases with the applied voltage. Moreover, the increasing voltage drop and depletion of the suspension lead to decreasing current and lower deposition rate after longer deposition time. The critical transition time of deposition kinetics is found to exponentially decrease with increasing applied voltage. 相似文献
15.
Sb2O3掺杂对ZnO压敏陶瓷晶界特性和电性能的影响 总被引:7,自引:1,他引:6
制备了掺有Sb2O3不同掺杂量ZnO压敏陶瓷样品,采用扫描电镜对样品进行显微结构分析,研究了Sb2O3掺杂浓度对ZnO压缩电阻显微结构和性能的影响,测量了样品的电性能,由样品C-V特性的测量计算出晶界参数,并由此讨论了陶瓷性能与晶界特性的相关性。研究发现,在ZnO压敏陶瓷样品中掺杂适量的Sb2O3可以提高ZnO压敏陶瓷样品的非线性性能,但当Sb2O3的摩尔分数超过0.088%时,电性能反而优化,这是因为Sb2O3掺杂浓度不同会引起晶界势垒高度、施主浓度与陷阱密度的变化,因此Sb2O3掺杂量要控制在适当的范围内。 相似文献
16.
This research was conducted to study the effect of ZnO nano-particulate modification on properties of Pb(Zr0.52Ti0.48)O3 (PZT)–(Bi3.25La0.75)Ti3O12 (BLT) ceramics prepared by a mixed-oxide solid-state sintering method. ZnO nano-particulate was added into PZT–BLT ceramics to obtain PZT–BLT/xZnO (x = 0, 0.1, 0.5 and 1.0 wt%). The PZT–BLT/xZnO ceramics were investigated in terms of phase, microstructure, physical, electrical, and mechanical properties. Tetragonality of PZT–BLT crystal structure tended to increase with increasing ZnO content. ZnO addition obviously increased the density of PZT–BLT ceramics while the grain size slightly decreased. Intergranular fracture mode was observed for pure PZT–BLT ceramic while the samples contained ZnO nano-particles showed a mixed-mode inter-/trans-granular fracture. Addition of ZnO also affected hardness and fracture toughness values. Addition of ZnO nano-particulate into PZT–BLT ceramics was found to improve room temperature dielectric constant but did not have a significant effect on ferroelectric properties. These observed results were expected to be caused by the behaviors similar to a donor-doped system. 相似文献
17.
Hao Tang Yaxuan Liu Da Bian Yongxin Guo Yongwu Zhao 《International Journal of Applied Ceramic Technology》2020,17(6):2612-2621
In this paper, a solvothermal method is used to prepare nano-sized zinc oxide-graphene oxide (ZnO–GO) hybrid, and the ZnO–GO hybrid is characterized by X-ray diffraction analysis, Raman, Fourier transform infrared spectroscopy, and scanning electron microscopy. In addition, chemically bonded phosphate ceramics coatings with different content of ZnO–GO hybrid are prepared on the stainless steel through the sol-gel method. The corrosion performance of the coatings is evaluated by electrochemical properties and the analysis of the surface and cross morphology of the coating. Results indicate ZnO–GO hybrid significantly enhances the compactness and corrosive behavior of the coating because the overlapping structure of GO flake improves the barrier performance of the coating. Besides, ZnO nanoparticles on the surface of GO can react with aluminum dihydrogen phosphate binder, in that case the adhesion between GO and the coating is improved. 相似文献
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19.
Eu3+ doped glass ceramics embedding ZnO quantum dots (QDs) were successfully prepared by a sol–gel method. High-resolution transmission electron microscopy (HRTEM) observations revealed that ZnO QDs with size of 3–6 nm precipitated homogeneously among the SiO2 glassy matrix after thermal treatment of the precursor sample. Such glass ceramics show a high transparency in the visible-infrared range due to the much smaller size of the ZnO QDs than the wavelength of the visible light. The emission and excitation spectra of the samples with various ZnO contents were studied. Based on Judd–Ofelt theory, the intensity parameter Ω2 was evaluated to investigate the change of the environment around Eu3+ in samples with and without QDs. 相似文献
20.
A. Salar Elahi M. Ghoranneviss 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(4):773-779
Large-area boron doped multi-layer carbon is synthesized by the plasma enhanced chemical vapour deposition (PECVD) using boron oxide powder and ethanol vapor. We have reviewed the carbon molecular crystals preparation by the PECVD method. The three main synthesis methods of carbon nanocrystals (CNCs) are the arc discharge, the laser ablation and the chemical vapour deposition with a special regard to the later one. By two different methods, ZnO layers were coated on the tubes. RF sputtering was one of the ways to directly deposit ZnO thin layer on the MWCNCs. On the other hand, we used thermally physical vapour deposition for making thin Zn film to oxidize it later. Scanning electron microscopy and also Raman spectroscopy measurements of the prepared samples confirmed the presence of ZnO nanolayers on the CNC bodies. 相似文献