Synthesis and characterization studies of NiO nanorods for enhancing solar cell efficiency using photon upconversion materials

We report the effect of calcination on the structural and optical properties of nanocrystalline NiO nanoparticles were successfully synthesized by virtue of a single source precursor method at mild reaction conditions between nickel nitrate and sodium hydroxide. Composition, structure and morphology of the products were analyzed and characterized by X-ray powder diffraction (XRD). The ultra-violet visible (UV–vis) absorption peaks of NiO exhibited a large blue shift and the luminescent spectra had a strong and broad emission band centered at 328 nm. The intense band gap was also observed, with some spectral tuning, to give a range of absorption energies from 2.60 to 3.41 eV. The various functional groups present in the NiO nanorods were identified by FTIR analysis. High resolution transmission electron microscopy (HRTEM) and the chemical composition of the samples the valence states of elements were determined by X-ray photoelectron spectroscopy (XPS) in detail. The electrochemical response of NiO proved that the nano-nickel has a high level of functionality due to its small size and higher electrochemical activity without any modifications. The above studies demonstrate the potential for the utilization of NiO nanoparticles as a promising material for opto-electronics applications.     

Effect of calcination temperature on Cu doped NiO nanoparticles prepared via wet-chemical method: Structural,optical and morphological studies

In the present study, NiO and Cu-doped NiO nanoparticles were successfully synthesized by wet chemical method at room temperature using sodium hydroxide (NaOH) as precipitating agent. The as-prepared Cu-doped NiO powder samples were subjected to three different calcination temperatures such as, 350 °C, 450 °C and 550 °C in order to investigate the impact of calcined temperatures on the phase formation, particle size and band gap evolution. The phase formation and crystal structure information of the prepared nanomaterials were examined by X-ray powder diffraction (XRD). XRD revealed the face-centered cubic (FCC) structure. Average crystalline size of pure and doped samples estimated using Scherer formula was found to be 15 nm and 9 nm respectively. With increase in the calcination temperature from 350 °C to 550 °C for the Cu doped NiO samples the particle size of the nanoparticles was found to increase from 4 nm to 9 nm respectively. The optical study for both pure and doped NiO nanoparticles was performed using an UV–Vis spectrophotometer in the wavelength range of 200–800 nm. The strong absorption in the UV region confirms the band gap absorption in NiO and was estimated from the UV–Vis diffuse reflectance spectra via Tauc plot. Systematic studies were also carried out to study the effect of calcination on the optical transmittance. Samples were also investigated using Raman and Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, morphology of the pure NiO and Cu-doped NiO Nanoparticles were examined by scanning electron microscope (SEM).     

Preparation and oxidation of an Y2O3-dispersed chromizing coating by pack cementation at 800 °C

Preparation and oxidation of an Y₂O₃-dispersed chromizing coating was investigated by chromizing an as-electrodeposited Ni-Y₂O₃ composite film using a conventional pack-cementation method but at a greatly decreased temperature (800 °C). For comparison, chromizing was also performed in the same condition on an as-deposited Ni film without Y₂O₃ particles. Oxidation at 900 °C indicated that compared to the Y₂O₃-free chromizing coating, the Y₂O₃-dispersed chromizing coating exhibited an increased oxidation resistance, due to the formation of purer and denser chromia scale. The Y₂O₃ effects on the coating formation and the coating oxidation behavior are discussed in detail.     

氩弧熔敷原位合成Ti（C,N）-TiB_2/Ni60A基复合涂层的组织与耐磨性

在Q235D钢表面采用氩弧熔敷技术制备了Ti（C,N）-TiB2增强Ni60A基复合涂层。利用SEM对复合涂层的显微组织进行了分析,Ti（C,N）颗粒呈花瓣状和不规则的球状,TiB2颗粒呈短棒状和六面体,并对其组织结构进行表征。利用显微硬度计和摩擦磨损试验机,对复合涂层的性能进行了测试和分析。涂层表面平均硬度达到了1250 HV。摩擦磨损实验表明,涂层的磨损机制主要为磨粒磨损,伴随着粘着磨损。     

Transformational behaviour of constrained shape memory alloys

The transformational behaviour of shape memory alloy (SMA) wires embedded into a fibre reinforced epoxy composite was investigated and is discussed in this article. The effects on the transformational temperatures, and heats of the embedded SMA wires and the generation of recovery stresses within the composites on heating are shown to be related to the reversible martensitic transformation of the SMA wires. This article details the effects of the constraining matrix on the transformations of self-accommodating and preferentially oriented martensite. It was found that there is little change in the transformation temperatures of the constrained SMA wires with increasing pre-strain, but that the measurable transformation heats decrease significantly with increasing pre-strain. It is concluded that the transformation of self-accommodating martensite is nearly not affected by the constrained matrix, whereas the transformation of the preferentially oriented martensite is suppressed.     

一种简便实用的钢铁防锈擦涂磷化液的研制

为了对机电设备及零部件的局部磷化,研制了一种用擦涂方法进行磷化的磷化液,分析讨论了复合促进剂对磷化成膜速度和磷化膜性能的影响.该磷化液游离酸度稳定、常温下操作、工艺简单.磷化膜层致密耐蚀且厚度均匀、可调,外观呈银白或银灰色.可用作耐磨、耐蚀膜层,也可用作有机涂层的基底.     

微弧氧化处理改善7N01-T5铝合金搅拌摩擦焊接头的耐蚀性能

利用微弧氧化技术在7N01-T5铝合金搅拌摩擦焊(FSW)接头表面制备陶瓷涂层.通过SEM和XRD技术测试微弧氧化涂层的微观形貌、物相组成等,并采用中性盐雾试验研究微弧氧化及封孔处理对焊接接头耐蚀性能的影响.结果表明,微弧氧化可在FSW接头区域生成均匀的陶瓷涂层;陶瓷涂层表面残留许多火山口状放电微孔和熔融烧结痕迹,并且主要由α-Al2O3与y-Al2O3两相构成;微弧氧化涂层具有较好耐腐蚀性,沸水封孔能生成水合氧化铝,使孔壁膨胀、孔径变小,进一步增强涂层的耐蚀能力,经96 h盐雾腐蚀后的单位面积失重量仅为2.6 mg.     

Oxygen partial pressure dependence of memory effect of sputtered nc-Al/α-Al2O3 thin films

Nanocrystalline aluminum embedded in amorphous dielectric alumina matrix thin films (nc-Al/α-Al₂O₃) was synthesized via reactive magnetron sputtering. The nc-Al/α-Al₂O₃ films at different oxygen partial pressures were sputtered on p-type Si substrates from a pure Al target in the mixed ambient of Ar and O₂. Both deposition rate and aluminum concentration increase as the oxygen partial pressure decreases. X-ray photoelectron spectroscopy and high-resolution transmission electron microscope studies give the confirmation of nanocrystalline Al embedded in amorphous Al₂O₃ matrix. This nanocomposite thin film exhibits memory effect as a result of charge trapping. The flat band voltage value depends on the Al nanocrystal concentration which is related to oxygen partial pressure.     

可膨胀石墨在膨胀型防火涂料中的性能研究

膨胀型防火涂料是防火涂料中的主要类型,具有低烟、少毒、无卤化的特点,受热时发生膨胀,生成导热系数较小的炭质层.延缓热量向基材的蔓延,呈高效的阻燃效果,为灭火赢得宝贵的时间,是实现阻燃剂无卤化的很有希望的途径之一,近年来已经被广泛用于建筑结构的防火处理。     

Oxidation behaviors of Nb-15W and Nb-15W-10Cr alloys fabricated by vacuum hot-pressing sintering

Vacuum hot-pressing sintering (VHPS) was used for fabricating Nb-15W and Nb-15W-10Cr (at.%) alloys under 30 MPa for 60 min at 1800 °C in pure argon atmosphere. Microstructure and oxidation resistance of both materials were investigated. Microstructure analysis showed that the as-sintered Nb-15W alloy only consisted of α-Nb (W) solid solution and the as-sintered Nb-15W-10Cr alloy composed of α-Nb (W, Cr) solid solution and small amount cubic type NbCr₂ Laves phase due to addition of 10 at.% Cr. The oxidation at 1300 °C for 4 h exhibited that the addition of 10 at.% Cr increased the oxidation rate of Nb-15W alloy. The effects of Cr on the oxidation behaviors are discussed in detail.