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131.
T. LalinskýAuthor VitaeG. VankoAuthor Vitae M. ValloAuthor Vitae M. Dr?íkAuthor VitaeJ. BrunckoAuthor Vitae J. JakovenkoAuthor VitaeV. KutišAuthor Vitae I. RýgerAuthor VitaeŠ. Haš?íkAuthor Vitae M. HusákAuthor Vitae 《Sensors and actuators. A, Physical》2011,172(2):386-391
We report on a piezoelectric response investigation of AlGaN/GaN circular high electron mobility transistor (C-HEMT) based ring gate capacitor as a new stress sensor device to be potentially applied for dynamic high-pressure sensing. A ring gate capacitor of C-HEMT with an additional ZnO gate interfacial layer was used to measure the changes in the piezoelectric charge induced directly by the variation of piezoelectric polarization of both gate piezoelectric layers (AlGaN, ZnO) for harmonic loading at different excitation frequences. Our experimental results show that about 10 nm thick piezoelectric ZnO layer grown on ring gate/AlGaN interface of C-HEMT can yield almost a 60% increase in the piezoelectric detection sensitivity of the device due to its higher piezoelectric coefficient. A three-dimensional CoventorWare simulation is carried out to confirm the increase in the measured piezoelectric response of ZnO based ring gate capacitor of C-HEMT. 相似文献
132.
R. PearceAuthor Vitae T. IakimovM. AnderssonAuthor Vitae L. HultmanAuthor VitaeA. Lloyd SpetzAuthor Vitae R. YakimovaAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(2):451-455
Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO2. Due to electron donation from SiC, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO2 detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n-p transition upon exposure to increasing concentrations of NO2 indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO2 making holes the majority carriers. 相似文献
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135.
针对SiC纤维的表面缺陷引起的低强度断裂问题,采用CVD技术对SiC纤维进行了C涂层.利用了XRD和SEM分别对无C涂层SiC纤维和C涂层SiC纤维的晶体结构和表面形貌进行了表征,对比了其抗拉强度.结果表明SiC由-SiC晶体组成,在(111)晶面方向上择优生长.涂C后SiC纤维表面光滑致密,表面缺陷较少,有效地降低了表面缺陷深度a值;涂C后SiC纤维的拉伸强度比无C涂层的抗拉强度增加了620MPa.因此,C涂层可以降低SiC纤维的表面缺陷,从而使SiC纤维的抗拉强度增加到2870MPa. 相似文献
136.
蒸汽过热炉耐火衬里操作时普遍存在缺陷,分析了缺陷产生的原因,并采用倾斜型纤维模块对耐火衬里的整体结构进行了改进设计.通过对传热模型的数值计算,证明此改进设计可行,改进后的结构能够提高过热炉的热效率. 相似文献
137.
针对两种典型耐火材料制品,利用有限元分析软件,使用APDL语言编写程序,研究了其钢包和中间包的温度和热应力分布规律.同时对其结构进行了优化,优化后的效果明显,有效地提高了其使用寿命. 相似文献
138.
Shoujun Wu Laifei Cheng Wenbin Yang Yongsheng Liu Litong Zhang Yongdong Xu 《Applied Composite Materials》2006,13(6):397-406
A layered graphitic CVD B-C coating was introduced between two CVD SiC coating layers. Microstructure and chemical characterization of the CVD B-C and the hybrid SiC/B-C/SiC multilayer coating was performed using SEM, EDS, XPS and XRD. Oxidation protection ability of the coating for the C/SiC composite was studied using a thermogravimetric analyzer (TGA) in the isothermal mode and by measuring residual flexural strength. The layered graphitic CVD B-C coating middle layer reduced the maximum crack width in the CVD SiC coating. The hybrid SiC/B-C/SiC multilayer coating provided a better oxidation protection for C/SiC composite than a three layer CVD SiC coating due to coating crack control and sealing effects at temperatures up to 1,300°C for 900 min. 相似文献
139.
SiO2 surface film is insufficient to protect SiC from the oxidation at widely varying partial pressures of oxygen, in particular in the presence of water vapor (e.g. in gas turbines) and also in other environments, e.g. during brazing for hard “tipping” of turbine blades. This work demonstrates that sol–gel alumina, coated on 0.5 mm coarse SiC grit, may form an acceptable, up to 10 μm thick “environmental barrier coating” EBC for some of these applications. The sol–gel has advantages over other methods (such as CVD) is the simplicity and low cost. We have used NH4OH pre-treatment to hydroxylate surface of SiC prior to applying alumina coating. Such modified SiC/SiO2 surface helped to deposit the positively charged alumina sol, and thus allowed to build thick coatings on the SiC grit. There is some indication that these coatings partially convert to mullite through reaction at the interface with the native silica on SiC. Oxidation resistance tests at 1200 °C were performed to show effectiveness of such coated SiC grit. 相似文献
140.