Effect of thermal history on the crystallization behaviour of polyetheretherketone by the dynamic viscoelastometer

The effect of thermal history on the crystallization behaviour of PEEK is investigated by the dynamic viscoelastometer. The crystallization behaviour of PEEK shows significant influence on the α peak in the tan δ and the storage modulus. The α peak temperature is rapidly increased at shorter times with the annealing temperature at 160°C or higher, and is then constant. The storage modulus is more gently reduced in the α transition region as the annealing temperature is higher, and becomes then a constant value. It is suggested that the reduction in the storage modulus corresponds to some defect in the crystal structure of PEEK.     

Novel application of reactive blending: tailoring morphology of PBT/SAN blends

Reactive blending has been usually utilized to stabilize morphology and to improve the properties of multi-component polymer blends by generating copolymers in situ at the interface. However, the present study on blends composed of poly(butylene terephthalate) (PBT) and functionalized styrene-acrylonitrile random copolymer (SAN) demonstrates another possibility for this method, i.e. tailoring morphology and thereby controlling the properties of polymer blends. By varying reaction conditions it was demonstrated that blends could be formed having the same ratio of [PBT]/[SAN] but which possessed completely different microstructural forms: a sea-island morphology with and without micelles, a corded dispersed phase morphology, and a highly oriented, layer-like morphology.     

<Emphasis Type="Italic">In Situ</Emphasis> Study of Reduction Process of CuO Paste and Its Effect on Bondability of Cu-to-Cu Joints

A bonding method utilizing redox reactions of metallic oxide microparticles achieves metal-to-metal bonding in air, which can be alternative to lead-rich high-melting point solder. However, it is known that the degree of the reduction of metallic oxide microparticles have an influence on the joint strength using this bonding method. In this paper, the reduction behavior of CuO paste and its effect on Cu-to-Cu joints were investigated through simultaneous microstructure-related x-ray diffraction and differential scanning calorimetry measurements. The CuO microparticles in the paste were gradually reduced to submicron Cu₂O particles at 210–250°C. Subsequently, Cu nanoparticles were generated instantaneously at 300–315°C. There was a marked difference in the strengths of the joints formed at 300°C and 350°C. Thus, the Cu nanoparticles play a critical role in sintering-based bonding using CuO paste. Furthermore, once the Cu nanoparticles have formed, the joint strength increases with higher bonding temperature (from 350°C to 500°C) and pressure (5–15 MPa), which can exceed the strength of Pb-5Sn solder at higher temperature and pressure.     

Development and evaluation of a palm-sized optical PM2.5 sensor

A new palm-sized optical PM_2.5 sensor has been developed and its performance evaluated. The PM_2.5 mass concentration was calculated from the distribution of light scattering intensity by considering the relationship between scattering intensity and particle size. The results of laboratory tests suggested that the sensor can detect particles with diameters as small as ～0.3 µm and can measure PM_2.5mass concentrations as high as ～600 µg/m³. Year-round ambient observations were conducted at four urban and suburban sites in Fukuoka, Kadoma, Kasugai, and Tokyo, Japan. Daily averaged PM_2.5 mass concentration data from our sensors were in good agreement with corresponding data from the collocated standard instrument at the Kadoma site, with slopes of 1.07–1.16 and correlation coefficients (R) of 0.90–0.91, and with those of the nearest observatories of the Ministry of the Environment of Japan, at 1.7–4.1 km away from our observation sites, with slopes of 0.97–1.23 and R of 0.89–0.95. Slightly greater slopes were observed in winter than in summer, except at Tokyo, which was possibly due to the photochemical formation of relatively small secondary particles. Under high relative humidity conditions (>70%), the sensor has a tendency to overestimate the PM_2.5 mass concentrations compared to those measured by the standard instruments, except at Fukuoka, which is probably due to the hygroscopic growth of particles. This study demonstrates that the sensor can provide reasonable PM_2.5 mass concentration data in urban and suburban environments and is applicable to studies on the environmental and health effects of PM_2.5.

Copyright © 2018 American Association for Aerosol Research     

Rate enhancement of amines in the photopolymerization of methyl methacrylate under oxygen

The photopolymerization of methyl methacrylate was accelerated by amines such as N,N-dimethylbenzylamine, triethylamine, and diethylamine under nitrogen, in which additional initiating radicals were generated by the reaction of the amines with excited MMA. Enhanced rates were observed under oxygen for this photopolymerization in the presence of amines. Because UV spectra of the amines under oxygen indicated that the amines form charge-transfer complexes with oxygen, the rate enhancement was ascribed to photodecomposition of complexes that yield radical species. Molecular weights of polymers obtained in the photopolymerization in the presence of amines decreased under oxygen, supporting the assumed mechanism. © 1998 Society of Chemical Industry     

All-solid-state Z-scheme in CdS-Au-TiO2 three-component nanojunction system

Natural photosynthesis, which achieves efficient solar energy conversion through the combined actions of many types of molecules ingeniously arranged in a nanospace, highlights the importance of a technique for site-selective coupling of different materials to realize artificial high-efficiency devices. In view of increasingly serious energy and environmental problems, semiconductor-based artificial photosynthetic systems consisting of isolated photochemical system 1 (PS1), PS2 and the electron-transfer system have recently been developed. However, the direct coupling of the components is crucial for retarding back reactions to increase the reaction efficiency. Here, we report a simple technique for forming an anisotropic CdS-Au-TiO2 nanojunction, in which PS1(CdS), PS2(TiO2) and the electron-transfer system (Au) are spatially fixed. This three-component system exhibits a high photocatalytic activity, far exceeding those of the single- and two-component systems, as a result of vectorial electron transfer driven by the two-step excitation of TiO2 and CdS.     

绕击雷侵入波下1 100 kV电气设备的绝缘配合研究

用电气几何模型(A-W theory)和EMTP程序定量研究了中国特高压变电站设备的绝缘配合问题。与出厂雷电冲击试验电压波形不同,由绕击雷电侵入波在主变压器上产生的电压波形在波头有高频振荡且波尾时间长。考虑多重雷的绕击雷电侵入波,在线路入口安装瓷柱式避雷器和罐式避雷器可以更好地保护断路器和高抗。     

X型聚丙烯纤维力学性能试验研究

针对日本生产的X型聚丙烯纤维,采用微机控制电子万能试验机,对其抗拉强度、断裂伸长率、弹性模量等力学指标进行了试验,并与分别经过pH值为12.5的碱溶液和120℃的烘箱处理后的纤维力学性能进行了对比.试验结果表明:① X型聚丙烯纤维拉伸强度高、弹性模量大、延性好;②纤维耐碱、耐热性能好,经碱溶液处理后,纤维拉伸强度、弹性模量和断裂伸长率分别达到处理前的93.8%、96.3%、89.6%;经耐热处理后,纤维拉伸强度、弹性模量和断裂伸长率分别达到处理前的98.7%、99.4%、93.4%.     

Ion beam modification of TiO2 films prepared by Cat-CVD for solar cell

The effects of nitrogen ion bombardment on TiO₂ films prepared by the Cat-CVD method have been studied to improve the optical and electrical properties of the material for use in Si thin film solar cells. The refractive index n and the dark conductivity of the TiO₂ film increased with irradiation time. The refractive index n of the TiO₂ film was changed from 2.1 to 2.4 and the electrical conductivity was improved from 3.4 × 10^− 2 to 1.2 × 10^− 1 S/cm by the irradiation. These results are due to the formation of Ti-N bonds and oxygen vacancies in the film.