In-situ SiN combined with etch-stop barrier structure for high-frequency AlGaN/GaN HEMT

The etch-stop structure including the in-situ SiN and AlGaN/GaN barrier is proposed for high frequency applications.The etch-stop process is realized by placing an in-situ SiN layer on the top of the thin AlGaN barrier.F-based etching can be self-terminated after removing SiN,leaving the AlGaN barrier in the gate region.With this in-situ SiN and thin barrier etch-stop structure,the short channel effect can be suppressed,meanwhile achieving highly precisely controlled and low damage etching process.The device shows a maximum drain current of 1022 mA/mm,a peak transconductance of 459 mS/mm,and a maximum oscillation frequency(fmax)of 248 GHz.     

自聚焦透镜高效批量加工的双面研磨抛光法研究

依据双面研磨抛光原理,提出了加工自聚焦透镜平面和斜面辅助工装设计.从工艺技术特点和生产实际过程等方面对设计的工装使用情况进行分析验证.多次大批量加工实践证明,该辅助工装的设计完全满足了自聚焦透镜高效批量加工技术要求,简化整个生产线工艺,减少工艺流程时间,降低材辅料的消耗成本,从而验证了双面研磨抛光法是一种实用的加工自聚焦透镜的新方法.     

溶胶-凝胶法合成超细Li_(2 x)RE_xSi_(1-x)O_3及其离子导电性

用溶胶 凝胶法合成了Li2 xRExSi1 -xO3(RE =Pr ,Nd ,Sm ,Gd ;x =0～ 0 15 ) ,用DTA TG ,XRD ,TEM及交流阻抗等技术对样品的结构、形貌、粒径及离子导电性等进行了观察和测试。其固溶体形成范围是 0 相似文献   

苯/二联苯为桥的噻吩-吡咯-噻吩结构:分子构型及电致变色性质

A series of multi-branched dithienylpyrrole (SNS) monomers with rigid phenyl (PhSNS) and biphenyl rings (BPhSNS) as bridges were designed and synthesized, and were fabricated to form cross-linked polymers (pPhSNS, pBPhSNS) by electrochemical polymerization. Cyclic voltammetry (CV) results showed that PhSNS and BPhSNS exhibited similar oxidative properties except for one new higher-potential oxidative peak appearing in the curves of PhSNS. Theoretical calculations indicated that it should be attributed to the different steric configuration between the two dithienylpyrrole (SNS) units in PhSNS. One SNS unit possessed a larger twist angle (40.2°) between thiophene and pyrrole rings than the other one (21.2°), which indicated that PhSNS possessed a relatively larger energy gap (~0.4 eV) between HOMO-1 and HOMO than BPhSNS, for which HOMO and HOMO-1 levels were of almost the same energy. However, both PhSNS and BPhSNS showed similar onset oxidation potentials. The CV curves of pPhSNS and pBPhSNS showed that they presented similar oxidative properties, which enabled their corresponding electrochemical polymers to exhibit similar electrochromic properties. The UV-vis spectra of the corresponding polymers showed that both pPhSNS and pBPhSNS possessed similar optical absorption and similar multicolor switching between yellow (-0.8 V), greyish-green (0.9 V) and gray (1.1 V) colors. Besides, pPhSNS and pBPhSNS showed fast switching times of 0.57 s and 0.93 s at 1100 nm, respectively and reasonable contrasts of 46% and 31% at 1100 nm, respectively. These investigations may help understand the relationship between structural configuration and the electrochemistry/electrochromic properties for polymer electrochromic (PEC) materials research.     

合成高密度烃类燃料研究进展

本文对合成高密度烃类燃料的进展进行了总结,分别对多环烃类燃料、高张力笼状烃类燃料和添加纳米级微粒的燃料进行了评述.以烃类物质为原料,通过聚合、加氢、异构等工艺合成的多环高密度燃料拥有较高的能量密度和较佳的稳定性能,是目前高密度燃 料的发展重点.高张力笼状烃类燃料和添加纳米级微粒的燃料拥有更大的密度(一般大于1g/ cm3)和燃烧热值,是极具发展前景的新一代燃料。     

硅的原子吸收光谱分析进展

对近十年来用原子吸收光谱法测定硅的情况进行评述．重点介绍用石墨炉测定硅时，为了避免硅与石墨炉中碳形成难熔碳化硅影响测定硅的灵敏度而使用的各种化学改进剂，涂层石墨管和一些新的实验技术．引用参考文献４２篇．     

一种基于PVC膜电极的电位式葡萄糖传感器的研制

以三庚基十二烷基碘代季铵盐为电活性物质的PVC膜电极, 对过氧化氢和六价钼的络合物具有良好的电位响应. 将葡萄糖氧化酶固定到PVC膜电极表面, 制备成电位式葡萄糖传感器. 在优化的实验条件下, 该传感器在葡萄糖浓度为2×10^－4～5×10^－3 mol/L范围内有线性响应, 检测下限为5×10^－5 mol/L. 另外该传感器具有较高的稳定性和良好的选择性, 抗坏血酸、尿酸和一些氨基酸未对测定产生干扰.     

基于纤维素的气凝胶材料

纤维素是自然界中储量最为丰富的一种天然高分子。作为继无机气凝胶和合成聚合物气凝胶之后的第三代气凝胶,纤维素基气凝胶材料兼具绿色可再生的纤维素材料和多孔气凝胶材料两者的优点,成为纤维素材料研究与应用中的一个热点。本文梳理了纤维素基气凝胶材料的发展脉络,综述了纤维素基气凝胶材料的研究进展。重点对纤维素基气凝胶的制备方法进行了总结,包括基于含水溶剂和无水溶剂的纤维素直接溶解法及源自植物纤维素和细菌纤维素的纤维素纳米纤维的水相分散法。介绍了纤维素基气凝胶力学性能的提高和功能性开发的最新研究结果。最后对纤维素基气凝胶材料的发展前景和研究方向进行了展望。     

氮掺杂石墨烯负载的硫化镉空心球纳米复合材料的光催化性能

通过无模板法一步合成了一种新型N掺杂石墨烯负载的CdS空心球复合材料. 采用X射线衍射、透射电镜、红外光谱、紫外-可见光谱、N₂吸附-脱附、荧光光谱和X射线光电子能谱等技术对该材料进行了表征, 并在可见光照射下测试了其在降解亚甲基蓝和水杨酸中的光催化性能. 结果表明, 相对于氧化石墨烯负载硫化镉空心球和单独的硫化镉空心球, 氮掺杂石墨烯负载的硫化镉空心球具有更高的光催化活性和稳定性. 这是由于氮掺杂的石墨烯能充当优异的电子受体和传输体, 从而抑制了载流子的复合. 另外发现, 羟基自由基是可见光下降解亚甲基蓝的主要活性物种.     

Unsymmetrical N and/or O-bridged calixarene derivatives: synthesis,structure and encapsulation of solvent molecules in the solid state

Eight unsymmetrical N and/or O-bridged calixarene derivatives were obtained by 1 (naphthalene-2,7-diol), 2 (bis(4-hydroxyphenyl)methanone), 3 (4,4′-methylenedianiline), 4 (3,3′-methylenedianiline), 5 (4,4′-oxydianiline) and 6 (4,4′-(perfluoropropane-2,2-diyl)dianiline) reacting with fragment a (4,4′-bis(dichloro-s-triazinyloxy)propane-2,2-diyldibenzene) and b (N,N′-bis(dichloro-s-triazinyl)-4,4′-methylenedianiline) under very mild reaction conditions via efficient fragment coupling strategy. We also obtained the crystal structure of 1a (tetraoxocalix[2](propane-2,2-diyldibenzene,naphthalene)[2]triazine) which can form a molecular capsule by two dimers with C–H?N and C–H?O quadruple hydrogen bonds, and it has the encapsulation ability toward solvent molecules.