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排序方式: 共有105条查询结果,搜索用时 31 毫秒
21.
Azhar Iqbal Yousaf Iqbal Abdul Majeed Khan Safeer Ahmed 《Journal of Saudi Chemical Society》2018,22(4):449-458
This report describes the detailed structural and electrochemical characterization of a series of low content (0.01 to 0.05) Cu-Cr bi-metal doped LiMn2O4 cathode material synthesized by sol–gel method. The structural and morphological features were described using XRD, SEM, TEM, EDAX and FTIR techniques. The electron transfer and its feasibility were discussed through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The charge–discharge studies were performed to evaluate the capacity fading and rate capability. It was found that the electrochemical performance is very much dependent on the amount of Cu-Cr bi-metal doping and interestingly decreased the capacity fading with high cycleability. The sample with the least amount of dopants (i.e., LiCu0.01Cr0.01Mn1.98O4) demonstrated much improved capacity, cycleability and high rate capability. The LiCu0.01Cr0.01Mn1.98O4 cathode exhibited a discharge capacity of 112 mA h g?1 at very first cycle and retained 93 mA h g?1 after 100 cycles at a C rate of 0.3. Further, the same material at very high current density (5 C) retained 83% of the initial discharge capacity. The Cu-Cr doping stabilized the spinel structure by suppressing the Jahn-Teller distortion effect and Mn dissolution and the resultant material showed the workability of the cathodes for devices which work at substantially high C-rate of 5C. 相似文献
22.
Studies on thermal, thermal ageing and morphological characteristics of EPDM-g-VTES/LLDPE 总被引:1,自引:0,他引:1
A novel graft copolymer of vinyltriethoxysilane onto ethylene propylene diene terpolymer has been developed by grafting varying contents of VTES using dicumyl peroxide as an initiator in a twin-screw extruder. Grafting of VTES and EPDM has been ascertained using FTIR. The EPDM-g-VTES developed has been blended with different weight percentage of linear low density polyethylene [LLDPE] by melt mixing. Thermal, thermal ageing and morphological behaviour of the blends are studied with respect to the effect of blend composition, static vulcanization and dynamic vulcanization with varying quantities of VTES and LLDPE. The incorporation of silane moiety onto EPDM raises the inception and final decomposition temperature. The stability EPDM-g-VTES/LLDPE blend increases with increase in concentration of EPDM-g-VTES due to thermally stable Si-O-Si linkage. It was ascertain from SEM micrograph that EPDM-g-VTES/LLDPE blends lead to formation of interpenetrating crosslinked network during hot water treatment and by treatment with DCP, respectively. The linear, statically vulcanized, dynamically vulcanized and filled blends of EPDM-g-VTES/LLDPE have been characterized to assess the suitability of the blends for high performance applications. In addition, it is also observed that the incorporation of fillers improves thermal stability of the blends. 相似文献
23.
Graft polymerization of vinyltriethoxysilane (VTES) onto ethylene‐propylene‐diene terpolymer (EPDM) was carried out in toluene using dicumylperoxide (DCP) as initiator. Effects of various parameters (EPDM content, VTES content, reaction time, reaction temperature and initiator concentration) on the grafting efficiency of VTES onto EPDM were investigated. At the optimum grafting efficiency conditions, EPDM‐g‐VTES was developed by melt mixing in a twin screw extruder and then linear (l), statically vulcanized (s) and dynamically vulcanized (d) blends of EPDM‐g‐VTES with linear low‐density polyethylene (LLDPE) with varying percentage compositions were prepared by melt mixing in the twin screw extruder. The grafting of VTES onto EPDM and its crosslinking was confirmed by FT‐IR. The characterization of mechanical properties such as tensile strength, elongation at break, Young's modulus and hardness, differential scanning calorimetry (DSC) analysis and morphology were studied and compared for the EPDM‐g‐VTES/LLDPE blends. The study reveals that the dynamically vulcanized blend improves the mechanical and thermal properties due to the presence of efficient interaction between component polymers when compared with other blends. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
24.
Spectrophotometric Determination of Prochlorperazine Maleate in Pure and Pharmaceutical Preparations
Tehseen Aman Zeeshan Majeed Asrar Ahmad Kazi Islam Ullah Khan 《Mikrochimica acta》2002,138(1-2):13-17
Prochlorperazine maleate reacts with 1-naphthylamine and sodium nitrite, after heating for 110 s at 80 °C to give an orange
red colour having maximum absorbance at 460 nm. The reaction is selective for prochlorperazine maleate with 0.01 mg/mL as
visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer’s
law from 0.01 mg/10 mL to 0.33 mg/10 mL of prochlorperazine maleate and the relative standard deviation is 0.68%. The quantitative
assessment of tolerable amounts of other drugs is also studied.
Received September 22, 2000. Revision June 19, 2001 相似文献
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Muhammad Muzammal Hussain Dr. Muhammad K. Majeed Prof. Haitao Ma Prof. Yunpeng Wang Dr. Adil Saleem Mina Lotfi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(2):e202103220
Organic resin cross-linking ZIF-67/SiO2 superhydrophobic (SHPB) multilayer coating was successfully fabricated on metal substrate. The perfluoro-octyl-triethoxy silane (POTS) modified ZIF-67 and SiO2 coating was applied on primary coated polytetrafluoroethylene (PTFE) and epoxy resin (EP) via spray coating method. Here, we present that the robust superhydrophobicity can be realized by structuring surfaces at two different length scales, with a nanostructure design to provide water repellence and a microstructure design to provide durability. The as-fabricated multilayer coating displayed superior water-repellence (CA=167.4°), chemical robustness (pH=1–14) and mechanical durability undergoing 120th linear abrasion or 35th rotatory abrasion cycle. By applying different acidic and basic corrosive media and various weathering conditions, it can still maintain superior-hydrophobicity. To get a better insight of interaction between inhibitor molecules and metal surface, density functional theory (DFT) calculations were performed, showing lower energy gap and increased binding energy of ZPS/SiO2/PTFE/EP (ZPS=ZIF-67+POTS) multilayer coating compared to the ZIF-67/SiO2/PTFE/EP, thereby supporting the experimental findings. Additionally, such coatings may be useful for applications such as anti-corrosion, self-cleaning, and anti-icing multi-functionalities. 相似文献
27.
Muhammad K. Majeed Guangyao Ma Yanxiu Cao Hongzhi Mao Dr. Xiaojian Ma Dr. Wenzhe Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11991-11997
Silicon (Si)-based anode materials with suitable engineered nanostructures generally have improved lithium storage capabilities, which provide great promise for the electrochemical performance in lithium-ion batteries (LIBs). Herein, a metal–organic framework (MOF)-derived unique core–shell Si/SiOx@NC structure has been synthesized by a facile magnesio-thermic reduction, in which the Si and SiOx matrix were encapsulated by nitrogen (N)-doped carbon. Importantly, the well-designed nanostructure has enough space to accommodate the volume change during the lithiation/delithiation process. The conductive porous N-doped carbon was optimized through direct carbonization and reduction of SiO2 into Si/SiOx simultaneously. Benefiting from the core–shell structure, the synthesized product exhibited enhanced electrochemical performance as an anode material in LIBs. Particularly, the Si/SiOx@NC-650 anode showed the best reversible capacities up to 724 and 702 mAh g−1 even after 100 cycles. The excellent cycling stability of Si/SiOx@NC-650 may be attributed to the core–shell structure as well as the synergistic effect between the Si/SiOx and MOF-derived N-doped carbon. 相似文献
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Ahmed M Seayad AM Jackstell R Beller M 《Journal of the American Chemical Society》2003,125(34):10311-10318
A highly chemo- and regioselective hydroaminomethylation of simple as well as functionalized alpha-olefins using a cationic rhodium precatalyst together with Xantphos as ligand is reported. Studies of the influence of ligands and reaction conditions led to an unprecedented selective hydroaminomethylation procedure. The novel procedure constitutes an economically attractive and environmentally favorable synthesis of secondary and tertiary aliphatic amines. 相似文献