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141.
将水玻璃为硅源所制备的纳米孔硅气凝胶与苯乙烯单体用微波加热合成法制备出SiO2气凝胶核/聚苯乙烯壳复合微球.用顺序间隔取样测试方法试验复合微球的密度、转化率和包覆率与微波合成温度、时间和聚合体系各组分变化情况,分析讨论了影响变化因素和原因.通过TEM和FE-SEM对复合微球进行结构与形貌表征.结果表明,优选体系组分配比为SiO2气凝胶3g、苯乙烯21g、乙醇水溶剂配比为380g∶20g、引发剂4.2g及稳定剂2g,微波合成工艺参数为加热功率500W,加热时间40min、加热温度60℃.在此工艺条件下合成,复合微球合成转化率是67.1%、包覆率为32.7%,制备出的核壳结构复合微球的粒径约为100~200nm、震实密度为0.353g/cm3,且表面凹凸不平状似"草莓"的微粒. 相似文献
142.
A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated. The pre-reduced pellets, with a porous structure, and fine particles are carburized homogeneously at 400-650 ℃ in a CO atmosphere. The carburized carbon not only acts reaction as a reduction agent, but also absorbs microwave in the reduction process. Hence, the carburized pre-reduced pellets can be rapidly reduced by microwave heating. There are three procedures involved in the process, namely, gas-based pre-reduction, low-temperatttre carburization and deep reduction by microwave heating. Carburized pre-reduced iron ore pellets show a rapid temperature rise that is twice as fast as the results for pre-reduced pellets in the laboratory. This not only improves the efficiency of the microwave heating, but also accelerates the reduction of iron oxides. The temperature of the pre-reduced pellets rises to 1050 ℃ in 45 min when the carburization rate is 2.02%, and the metallization rate and compressive strength reach 94.24% and 1725 N/pellet, respectively. 相似文献
143.
基于0.15μm砷化镓(GaAs)工艺建立一种电感模型,并用高频结构模拟器(High Frequency Structure Simulator,HFSS)仿真验证,并在此基础上设计一种微波功率放大器,并用高级系统设计软件(Advanced Design System,ADS)进行仿真。仿真结果显示在812GHz频率范围内,饱和输出功率大于21.9dBm,1dB压缩点输出功率大于20dBm,功率增益大于26dB,功率附加效率大于34%,稳定系数大于1。 相似文献
144.
以玉米须为原料,对玉米须总皂苷的提取方法进行研究.考察有机试剂浸提法、超声法、微波法对玉米须总皂苷提取率的影响,并对这三种方法的动力学特性进行对比.试验结果表明:有机溶剂浸提法提取玉米须总皂苷得率较高,但有机溶剂用量较大,实验时间较长;微波法和超声法试验相对简单,时间较短、温度较低、提取速率较快.因此,微波法和超声法作为玉米须总皂苷的提取方法值得推广. 相似文献
145.
Egor M. Kostyukhin Alexander L. Kustov Nikolay V. Evdokimenko Andrey I. Bazlov Leonid M. Kustov 《Journal of the American Ceramic Society》2021,104(1):492-503
Lanthanum orthoferrite powders were synthesized via one-step hydrothermal reactions under mild conditions using microwave and conventional heating. The use of microwave irradiation during the synthesis allows one to obtain nanocrystalline LaFeO3 with a higher yield and reduced crystallite and particle size within a 16 times shorter duration (3 hours) at a lower temperature of 220°C as compared to the conventional heating. The catalytic decomposition of nitrous oxide was performed over both samples, it was shown that the sample obtained under microwave conditions demonstrates enhanced activity as a catalyst: N2O decomposes completely at 700°C over the catalyst formed at microwave conditions, while the comparative catalyst prepared by conventional heating reaches a lower conversion of only 60% at the same temperature and catalytic reaction conditions. 相似文献
146.
Kang Du Yan-Bo Guo Fei Wang Jun Fan Xiao-Chuan Wang Wen-Zhong Lu Wen Lei 《Journal of the American Ceramic Society》2021,104(2):974-984
Ca1+2xSnSi2x+yO3+6x+2y (0.1 ≤ x ≤ 0.9; 0.1 ≤ y ≤ 0.9) microwave dielectric ceramics were prepared through traditional solid-state reaction sintered at 1450°C–1500°C for 5 hours. The Ca3SnSi2O9 second phase replaced the SnO2 second phase of the Ca1+2xSnSi2xO3+6x (x = 0, y = 0) ceramics by controlling the ratio of Ca:Sn:Si. The cracks of CaSnO3 (x = 0, y = 0) ceramic were inhibited, the microwave dielectric properties were optimized by introducing the Ca3SnSi2O9 second phase, and the CaSnO3-Ca3SnSi2O9 mixture system existed at (0.1 ≤ x ≤ 0.9, y = 0). The CaSnSiO5 phase with positive τf value was related to the Si-rich in CaSnSiyO3+2y (x = 0; 0.1 ≤ y ≤ 0.9), and the coexistence of three and four phases was obtained at CaSnSiyO3+2y (0.1 ≤ y ≤ 0.9) ceramics. The CaSnSiO5 phase appeared at CaSnSiyO3+2y (0.3 ≤ y ≤ 0.9) ceramics. The CaSnSiyO3+2y (y = 0.8) ceramic with 49.2 wt% CaSnSiO5 phase exhibited excellent microwave dielectric properties: εr = 11.06, Q × f = 57,500 GHz (at 11.5 GHz), and τf = +8.1 ppm/°C. 相似文献
147.
Zhe Xiong Bin Tang Xing Zhang Chengtao Yang Zixuan Fang Shuren Zhang 《Journal of the American Ceramic Society》2021,104(4):1726-1739
The effects of LB glass on the sintering behavior, structure, and dielectric properties for the Ba3.75Nd9.5Ti17.5(Cr0.5Nb0.5)0.5O54 (BNTCN) ceramic were investigated. The results showed that the LB glass, as an effective sintering aid, successfully lowered the sintering temperature of BNTCN ceramic by formation of the liquid phase. Furthermore, the change of the structure and decrease in grain size had influences on the electrical conductivity, thermal stability, and microwave dielectric properties for the BNTCN ceramics doped LB glass. Finally, the excellent microwave dielectric properties with εr = 73.4, Q × f = 5277 GHz, and τf = +7.1 ppm/°C were obtained for samples sintered at 950°C when x = 5, indicating the BNTCN ceramic doped with 5 wt% LB glass is a promoting LTCC material. 相似文献
148.
Xiao-Qiang Song Wen Lei Fei Wang Tao Chen Shi-Wo Ta Zhen-Xiao Fu Wen-Zhong Lu 《Journal of the American Ceramic Society》2021,104(4):1740-1749
A gillespite-structured MCuSi4O10 (M = Ba1-xSrx, Sr1-xCax) ceramics with tetrahedral structure (P4/ncc) were prepared by solid-state reaction method. X-ray diffraction and thermogravimetry with differential scanning calorimetry (TG-DSC) were employed to study the phase synthesis process of BaCuSi4O10. Pure BaCuSi4O10 phase was obtained at 1075°C and decomposed into BaSiO3, BaCuSi2O6, and SiO2 when calcined at 1200°C. The relationships between the crystal structure and microwave dielectric properties of MCuSi4O10 ceramics were revealed based on the Rietveld refinement and P-V-L complex chemical bond theory. The dielectric constant (εr) decreased linearly with decreasing total bond susceptibility and ionic polarizability. Quality factor (Q × f) was closely dependent on bond strength and lattice energy. The temperature coefficient of resonant frequency (τf) was controlled by the stability of [CuO4]6− plane in MCuSi4O10. Optimum microwave dielectric properties were obtained for SrCuSi4O10 when sintered at 1100°C for 3 hours with a εr of 5.59, a Q × f value of 82 252 GHz, and a τf of −41.34 ppm/°C. Thus, SrCuSi4O10 is a good candidate for millimeter-wave devices. 相似文献
149.
Xing Zhang Cheng Liu Liang Shi Wenhao Xu Hongyang Zhang Rui Zeng Huaiwu Zhang 《Journal of the American Ceramic Society》2021,104(11):6054-6063
Ti4+-modified MgZrNb2O8 (MgZr1-xTixNb2O8, x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized using the traditional solid-state reaction method. Pure MgZr1–xTixNb2O8 was detected without any secondary phase via the X-ray diffraction patterns. According to the sintering behavior and the surface morphology results, the introduction of Ti4+ reduced the sintering temperature and promoted the grain growth. The correlations between the dielectric properties and the crystal structure were analyzed through the Rietveld refinement and Raman spectroscopy. The slight shifts of the Raman peaks, corresponding to different vibration modes, were induced by the substitution of Ti4+ for Zr4+ and related to the improved quality factor. In general, the sample of MgZr0.9Ti0.1Nb2O8 sintered at 1320°C for 4 h exhibited promising microwave dielectric properties with an ultra-high Q × f value of 130 123 GHz (at 7.308 GHz, 20°C), which is potential for 5G communication applications. 相似文献
150.
微波辅助化学已成为备受关注的研究课题,但微波反应动力学模型缺乏系统的研究严重阻碍了微波在化学工业化上的应用,微波化学反应在化学工程化的放大设计及应用缺乏基础依据。以偶氮二异丁脒盐酸盐(AIBA)分解反应为例,通过选择合适的溶剂调整其复配比例,得到一系列具有不同沸点的混合溶剂作为反应介质,使反应在混合溶剂沸点下进行,以保证反应过程中微波的持续作用来研究微波反应动力学。从微波作用下动量传递、热量传递和质量传递的影响因素进行考虑,选择了对微波化学反应必须和充分的因素,包括微波功率密度 p、黏度 μ、密度ρ、反应物的浓度 CA、温度 T、热导率 λ、损耗角正切δ 和微波辐射频率f。采用量纲分析方法,通过模型分析建立了微波分解反应动力学模型。通过大量的实验数据进行拟合,回归出特定反应的模型参数。该模型估算值与实验值的误差较小,相关性较高,具有一定的预测能力可解决微波反应过程放大的基础性问题,有望用于指导微波工业化生产。 相似文献