Electrochemical study and electrodeposition of copper in the hydrophobic tri-n-octylmethylammonium chloride ionic liquid media

The electrodeposition of metallic Copper in binary mixture ionic liquid/organic solvent (tri-n-octylmethylammonium chloride (TOMAC))/chloroform (CHCl₃) was investigated. The electrochemical behavior of Cu(II) in TOMAC/CHCl₃ at glassy carbon working electrode at room temperature was studied by cyclic voltammetry and spectroscopy impedance. The results from the cyclic voltammetry showed that the electrodeposition of metallic Cu in the binary mixture ionic liquid/organic solvent was an irreversible process and was controlled by the diffusion of Cu(II) on a glassy carbon working electrode. The average value of αn_α was found to be 0.23 at 25 °C and the diffusion coefficient (D₀) of Cu(II) was calculated to be 7.12 10^− 9 cm²/s at room temperature. The performance of TOMAC ionic liquid such as internal resistance has been investigated with electrochemical impedance spectroscopy (EIS). The scanning electron microscopy (SEM) micrographs was used to observe that the copper plating was moderately dense and contains fine crystallites with average sizes of about 1 μm at room temperature. Energy dispersive X-ray analysis (EDAX) profile showed that the obtained film was copper.     

Low temperature synthesis of iodine-doped TiO2 nanocrystallites with enhanced visible-induced photocatalytic activity

Iodine-doped TiO₂ nanocrystallites (denoted as I-TNCs) were prepared via a newly developed triblock copolymer-mediated sol-gel method at a temperature of 393 K. I-doping, crystallization and the formation of porous structure have been simultaneously achieved. The obtained particles were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV-vis spectrophotometer. The results indicated that the as-prepared I-TNCs possessed a diameter of ca. 5 nm with anatase crystalline structure and a specific surface area of over 200 m² g⁻¹. The presence of iodine expanded the photoresponse in visible light range, and led to enrich in surface hydroxyl group on the TiO₂ surface. Compared with the commercial photocatalyst P25, the I-TNCs significantly enhanced the photocatalytic efficiency in the degradation of rhodamine B and 2,4-dichlorophenol, and the I-TNCs with 2.5 mol% doping ratio exhibited the best photocatalytic activity.     

Oxidation temperature dependent properties of MgO thin film on alumina

The magnesium oxide thin films were prepared by thermal oxidation (in air) of vacuum evaporated magnesium thin film on alumina. It was found that oxidation temperature (623 K, 675 K and 723 K) and thickness (103 nm and 546 nm) dependent effects were prominently manifested in the surface morphology. Electrical and microwave properties (8-12 GHz) of the MgO thin films were also carried out. X-ray diffraction showed orientation along (2 0 0) and (2 2 0) directions. Flowerlike morphology was observed from SEM and flake like morphology for films of higher thickness oxidized at higher temperatures. The magnesium oxide thin film showed NTC behavior. Microwave transmittance was found to increase with increase in oxidation temperature but was lower than alumina. Frequency and oxidation temperature dependent microwave permittivity was obtained. The microwave dielectric constant varied in the range 8.3-15.3.     

Relatively low temperature synthesis of graphene by radio frequency plasma enhanced chemical vapor deposition

We present a simple, low-cost and high-effective method for synthesizing high-quality, large-area graphene using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) on SiO₂/Si substrate covered with Ni thin film at relatively low temperatures (650 °C). During deposition, the trace amount of carbon (CH₄ gas flow rate of 2 sccm) is introduced into PECVD chamber and the deposition time is only 30 s, in which the carbon atoms diffuse into the Ni film and then segregate on its surface, forming single-layer or few-layer graphene. After deposition, Ni is removed by wet etching, and the obtained single continuous graphene film can easily be transferred to other substrates. This investigation provides a large-area, low temperature and low-cost synthesis method for graphene as a practical electronic material.     

The influence of growth temperatures on the characteristics of GaN nanowires

This paper presents the investigation of the properties of GaN nanowires synthesized from Ni-catalyzed chemical vapour deposition method under various growth temperatures. The influence of the growth temperatures on the morphological, structural and optical characteristics of the synthesized GaN nanowires was investigated in this work. Field-emission scanning electron microscopy images revealed that the 950 °C was the optimal growth temperature for synthesizing uniform, straight and smooth morphology of GaN nanowires. X-ray diffraction results demonstrated that the synthesized low dimensional GaN structures have the hexagonal wurtzite structure. Ultraviolet and blue emissions were detected from photoluminescence measurements. In addition, phonon replicas with the energy separation of 90 meV have been observed at the lower energy of the blue emission region in photoluminescence spectra.     

抑制损伤发展的CO_2激光修复技术及机理研究

熔石英表面激光损伤发展问题一直制约着激光器的运行通量。采用CO2激光在线熔融修复损伤点,修复后形成一个光滑的高斯坑,去除了损伤点中的裂纹,平滑了凹凸不平的表面,并且在紫外脉冲激光作用下,修复斑再次产生损伤的阈值高于熔石英元件的损伤生长阈值。因此CO2熔融修复技术能有效地抑制损伤发展。通过分析CO2激光作用下熔石英表面的温度分布,讨论修复坑的形成过程,确定激光参数对修复效果的影响,为寻找最佳修复参数提供理论基础。同时利用原子力显微镜(AFM)、轮廓仪细致分析损伤点和修复斑的微细结构,采用有限差分时域方法计算损伤点和修复斑周围的光强分布,探索消除裂纹和平滑表面对抑制损伤生长的作用。     

高温及超高温热管的启动特性和传热极限

根据局部高温、高热流加热等特殊场合的需求,设计、加工了钠高温热管及锂超高温热管,并对热管的启动和极限特性进行了研究。高温及超高温热管能够顺利启动,但启动时应注意可能到来的声速传热极限。端部加热启动时,端部附近管体部分会形成一段等效的加热段,可以将工质从启动时的固体状态到全部熔化形成相变传热及流动循环的时间确定为启动时间。热管的传热极限特性表明,超高温热管应工作在更高的温度和更大的热流密度。热管的结构和工艺优化有利于启动和运行。     

包层模谐振特种光纤及传感特性研究

研究了一种具有双包层结构的包层模谐振特种光纤,该特种光纤具有一个低折射率内包层,基于耦合模原理,纤芯模与包层模之间发生谐振耦合,从而获得具有带阻特性的传输光谱.系统介绍了包层模谐振光纤的制备、传输原理及其弯曲、溶液折射率、折射率/温度双参量等传感特性.实验和理论研究结果表明,包层模谐振特种光纤对于弯曲、溶液折射率参量具...     

Arbitrary amplitude dust-acoustic solitary waves in a dusty plasma with flat-topped ion distribution

The properties of arbitrary amplitude dust-acoustic (DA) solitary waves (SWs) in a dusty plasma containing warm adiabatic dust fluid, isothermal electrons and ions following flat-topped velocity distribution is studied by the pseudo-potential approach. The effects of dust temperature and flat-trapped ions are found to significantly modify the basic features of DA-SWs as well modify the parametric regime for the existence of rarefactive solitary waves. The pseudo-potential for small amplitude limit is also analytically analyzed, and the numerical results are found to agree with analytical results.     

Milling time and BPR dependence on permeability and losses of Ni0.5Zn0.5Fe2O4 synthesized via mechanical alloying process

Ni_0.5Zn_0.5Fe₂O₄ has been synthesized using mechanical alloying method with two variables (milling time and ball-to-powder weight ratio (BPR)) were varied in order to study its effect on the magnetic properties of the material. The effects of these two variables were studied using XRD, SEM, TEM and later by impedance analyzer with the frequency range from 1 MHz to 1.8 GHz. The results obtained however show that there are no significant trends to relate the milling time and BPR with the permeability and losses of the material studied. After being sintered at 1150 °C, all the effects of alloying process seem to diminish.