Ali Saidi
,
Kamran Azari
材料科学技术（英文）
Industrial application of microwave, as a heating source for material processing, was reviewed. The feasibility of carbothermic reduction of zinc oxide concentrate, as well as the effect of operating parameters was investigated, using a home style microwave oven at 2.45 GHz. Zinc oxide concentrate does not effectively absorb microwave energy, while any source of carbon, which is used as the reduction agent, absorbs microwave energy very well. In this respect coke breeze was found to be the best, and thus, coke was used both as the reducing agent and the absorbent of microwave energy. It was also found that any increase in the carbon content and size, increases the reduction rate. Increasing the microwave power and the size of the sample could also increase the reduction rate. Further investigation shows that when zinc oxide is exposed to the microwave for some time, the rate of the reduction by conventional method increases.
关键词:
Microwave
,
null
,
null
Yang Ju
,
Yasushi Ohno
,
Hitoshi Soyama
,
Masumi Saka
材料科学技术（英文）
A method for electrical characterization of doped silicon in a contactless fashion using high-frequency electromagnetic waves was presented. A focusing sensor was used to focus a 110 GHz microwave on the surface of a silicon wafer. The amplitude and phase of the reflection coefficient of the microwave signal were measured, by which electrical conductivity of the wafer was determined quantitatively, independent of the permittivity and thickness of the wafer. The conductivity obtained by this method agrees well with that measured by the conventional four-point-probe method.
关键词:
Conductivity
,
null
,
null
,
null
Shunhua WU
,
Guoqing WANG
,
Shuang WANG
,
D
,
an LIU
材料科学技术（英文）
The effect of Sn4+ (BaSnO3) B-site substitution on the microstructure and dielectric properties of Ba(Mg1/3Ta2/3O3 microwave ceramics was investigated. X-ray diffraction shows that a complex perovskite material Ba(Mg1/3Ta2/3)O3 was prepared. As Sn4+ content x increases in the (1-x) Ba(Mg1/3Ta2/3)O3-xBaSnO3 (x=0.00～0.20) system, the dielectric constant generally keeps unchanged, while TCF changes from positive to negative. Although the addition of Sn4+ reduces the ordering degree, Qf0 is still increased when the ceramics density increases. This trend implies that Qf0 of this system is mostly determined by ceramics density rather than ordering degree. After sintering at 1500℃ for 3 h, the system with x=0.15 was found to have excellent dielectric properties as follows: ε≈25, Qf0≥300,000 GHz at 7 GHz, TCF=-0.6×10-6℃.
关键词:
Ba(Mg1/3Ta2/3)O3
,
null
,
null
,
null
Shuwang DUO
,
Meishuan LI
,
Yaming ZHANG
材料科学技术（英文）
In order to study the atomic oxygen corrosion of spacecraft materials in low earth orbit environment, an atomic oxygen simulator was established. In the simulator, a 2.45 GHz microwave source with maximum power of 600 W was launched into the circular cavity to generate ECR (electron cyclotron resonance) plasma. The oxygen ion beam moved onto a negatively biased Mo plate under the condition of symmetry magnetic mirror field confine, then was neutralized and reflected to form oxygen atom beam. The properties of plasma density, electron temperature, plasma space potential and ion incident energy were characterized. The atomic oxygen beam flux was calibrated by measuring the mass loss rate of Kapton during the atomic oxygen exposure. The test results show that the atomic oxygen beam with flux of 1016~1017 atoms•cm-2•s-1 and energy of 5~30 eV and a cross section of Φ80 mm could be obtained under the operating pressure of 10¬-1~10-3 Pa. Such a high flux source can provide accelerated simulation tests of materials and coatings for space applications.
关键词:
Atomic oxygen
,
null
,
null
,
null
JunhHua WU
材料科学技术（英文）
Microwave dielectric measurements over the broad bandwith of 10 MHz to 20 GHz were conducted on composites comprising bundles of single-walled carbon nanotubes (SWNT) embedded in an epoxy matrix, in comparison to the nano-graphite and MWNT. It is found that both relative real and imaginary permittivity of the nanocomposites are strong functions of the SWNT concentration, showing large, wide dielectric and electrical response. Distinct resonance around 1.5 GHz is observed at high SWNT concentrations, accompanied by the downshift of the resonance frequency with increasing concentration. Largely, the SWNT-epoxy composites share the behavior of the MWNT owing to structural similarity, much more effective than the nano-graphite. The remarkable, broadband dielectric and electrical properties of the nanotubes acquired in the work originate from their unique seamless graphene architectures, modeled by two major contributions, dielectric relaxation/resonance and electronic conduction, which is substantiated by the agreement between theoretical analysis and experimental results. The carbon nanotube composites are prospective for microwave applications and offer experimental evidence for fundamental studies in low-dimensional systems.
关键词:
Single-walled carbon nanotube
,
carbon
,
nanotube
,
Dielectric
黄延强
催化学报
doi:10.1016/S1872-2067(12)60587-7
采用溶胶-凝胶法制备了Co取代的Ba2MghCoxFe12O22(x=0.0～2.0)催化剂,并考察了其在高浓度N2O (30 vol％)分解反应中的催化活性.结果表明,Co的取代显著提高了Ba2Mg2Fe12O22催化剂活性,当x=2时,N2O的完全分解温度从1123 K降至973 K;提高催化剂焙烧温度会导致其表面积降低,进而降低其催化活性；但采用微波加热则能显著提高催化剂活性.
关键词:
一氧化二氮
,
分解
,
六铁酸盐
,
Ba2Mg2Fe12O22
,
钴
,
微波
黄珊
,
王继刚
,
刘松
,
张玥晨
,
钱柳
,
梁杰
新型炭材料
以Si粉、SiO2粉和人造石墨为原料，在1480℃、4 kW、80 min的真空微波辐照条件下快速高效地合成SiC纳米线。利用SEM、TEM、XRD等对所得产物的微观结构解析表明，在未使用催化剂的条件下，基于气固( VS)机制可成功制备出β型SiC。根据坩埚中的部位不同，所得SiC呈现出不同的形貌。坩埚上层的产物呈亮绿色，较为纯净，主要为直径约150 nm的纳米棒，并含有部分微米级SiC晶粒，表面氧化迹象不明显。其余部分产物呈灰绿色，主要是直径为20~50 nm的SiC/SiO2同轴纳米线(表层的SiO2厚度约2 nm)，并夹杂有未反应完全的石墨和SiO2。利用波长为240 nm的激发光分别对SiC纳米棒和同轴纳米线的光致发光特性的测试表明，两者均可观察到峰位在390 nm左右的发射峰，此结果与所报道的β-SiC纳米材料的发光性能相比，蓝移程度更高。
关键词:
微波法
,
碳化硅
,
纳米线
,
结构表征
,
光致发光
朱福良
,
杨志
,
赵金平
,
赵薪
新型炭材料
doi:10.1016/S1872-5805(16)60011-2
采用简单的微波辅助的方法成功制备了硫/膨胀石墨复合材料。膨胀石墨可以用作锂硫电池中阴极的微型容器及集流体。通过控制硫与膨胀石墨的配比成功控制了复合材料中硫颗粒的大小。当硫与膨胀石墨的比例为10∶1时，可以得到相对较均匀的硫颗粒。同时研究了不同条件下所制样品的锂硫电池性能。结果表明，硫的含量与硫颗粒的大小对锂硫电池的容量非常重要。当硫与膨胀石墨的比例为10∶1时，在0.1 C放电速率下，复合材料具有最高的放电容量1020 mAh·g-1。
关键词:
膨胀石墨
,
锂硫电池
,
微波
,
硫颗粒尺寸
