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11.
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The objective of this work is to study the thermal and mechanical properties of films based on blends of poly(vinyl alcohol) (PVA) with different weight percent of sorbitol. Solid-state PVA/sorbitol polymer membranes were prepared by a solution casting method. The characteristic properties of these polymer membranes were examined by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), nanoindentation methods and by Fourier Transform Infrared (FTIR) spectroscopy. It was found that the thermal properties (glass transition, Tg, melting point, Tm and decomposition temperature, Td) for PVA blends showed a decrease proportional to the sorbitol concentrations. The hardness and elastic modulus obtained from nanoindentation test were also found to decrease with increase in plasticizer concentration. FTIR confirmed the reduction in hydrogen bonding between PVA chains in favour of formation new bonding between the plasticizer and the PVA chains. 相似文献
13.
A hydrostatic pad is usually made up of a recess surrounded by a land. Viscous fluid is supplied under pressure to the recess. The land, being separated from the bearing surface by a relatively small clearance, will act as the hydraulic impedance needed to separate the required bearing pressure inside the recess from the pressure of the surrounding environment. If the pad is moved relative to the bearing surface, the film of fluid in the clearance, being viscous, will be sheared. This shearing action will initiate viscous shear stresses between the fluid layers and hence viscous drag between the moving pad and the bearing surface. The lands of the pad, having a much smaller clearance from the bearing surface, will be subjected to a much higher drag force than the recess. The power required to overcome such a drag force, and cause the required motion of the pad relative to the bearing surface, will be transformed mainly into heat. Sometimes, especially under high relative speeds and with small clearances, the generated heat can be detrimental to the bearing action, and if excessive, may lead to bearing failure. 相似文献
14.
M.E. Mohsin 《Tribology International》1981,14(1):47-54
This paper describes a hydrostatic bearing designed for high speed applications: the Total Cross Flow (TCF) bearing. The design features of this bearing are discussed and compared with conventionally designed hydrostatic bearings. The TCF bearing offers a number of important meritorious properties which are essential for high and ultra-high speed applications 相似文献
15.
Haris Mahmood Khan Chaudhry Haider Ali Tanveer Iqbal Saima Yasin Muhammad Sulaiman Hamayoun Mahmood Muhammad Raashid Mohsin Pasha Bozhong Mu 《中国化学工程学报》2019,27(10):2238-2250
Biodiesel utilization has been rapidly growing worldwide as the prime alternative to petrodiesel due to a global rise in diesel fuel demand along with hazardous emissions during its thermochemical conversion. Although, several debatable issues including feedstock availability and price, fuel and food competition, changes in land use and greenhouse gas emission have been raised by using edible as well as inedible feedstocks for the production of biodiesel. However, non-crop feedstocks could be a promising alternative. In this article, waste cooking oils have been recommended as a suitable option for biodiesel production bearing in mind the current national situation. The important factors such as the quantity of waste cooking oil produced, crude oil and vegetable oil import expenses, high-speed diesel imports, waste management issues and environmental hazards are considered. Moreover, process simulation and operating cost evaluation of an acid catalyzed biodiesel production unit are also conducted. The simulation results show that the production cost of waste cooking oil-based biodiesel is about 0.66USD·L-1. We believe that the present overview would open new pathways and ideas for the development of biofuels from waste to energy approach in Pakistan. 相似文献
16.
Pengyuan Fan Yangyang Zhang Yiwei Zhu Weigang Ma Kai Liu Xueting He Mohsin Ali Marwat Bing Xie Ming Li Haibo Zhang 《Journal of the American Ceramic Society》2019,102(7):4113-4126
0.75(Na0.5Bi0.5)TiO3–0.25SrTiO3 lead-free incipient piezoceramic is a promising candidate for actuator applications due to their large reversible electromechanical strains at the relatively low driving field of 40 kV/cm. In order to further reduce the driving field of 0.75(Na0.5Bi0.5)TiO–0.25SrTiO3 relaxor ceramic to meet the requirements for real actuators application, the relaxor/ferroelectric (RE/FE) 0-3 composite ceramics method was employed. The polarization and strain behaviors were examined as a function of the weight ratio of the relaxor/ferroelectric phases. It was found that 90 wt% 0.75(Na0.5Bi0.5)TiO3–0.25SrTiO3/10 wt% 0.96(Na0.84K0.16)1/2Bi1/2TiO3–0.04SrTiO3 RE/FE 0-3 type composite samples provided a high unipolar strain of 0.25% and the corresponding large-signal piezoelectric coefficient, d*33 of 833 pm/V at 30 kV/cm, which are 32% higher than the values of the pure 0.75(Na0.5Bi0.5)TiO3–0.25SrTiO3. The enhanced electric-field-induced strain at relatively lower field was attributed primarily to the reduction in the RE-FE phase transition electric field. It was also found that the RE/FE composite ceramics exhibited significantly reduced frequency dependence in the unipolar strain behavior at room temperature. 相似文献
17.
Nikola Kanas Sathya Prakash Singh Magnus Rotan Mohsin Saleemi Michael Bittner Armin Feldhoff Truls Norby Kjell Wiik Tor Grande Mari-Ann Einarsrud 《Journal of the European Ceramic Society》2018,38(4):1592-1599
Due to high figure of merit, Ca3Co4 ? xO9 + δ (CCO) has potential as p-type material for high-temperature thermoelectrics. Here, the influence of processing including solid state sintering, spark plasma sintering and post-calcination on stability, microstructure and thermoelectric properties is reported. By a new post-calcination approach, single-phase materials were obtained from precursors to final dense ceramics in one step. The highest zT of 0.11 was recorded at 800 °C for CCO with 98 and 72% relative densities. In situ high-temperature X-ray diffraction in air and oxygen revealed a higher stability of CCO in oxygen (~970 °C) than in air (~930 °C), with formation of Ca3Co2O6 which also showed high stability in oxygen, even at 1125 °C. Since achievement of phase pure high density CCO by post-calcination method in air is challenging, the phase stability of CCO in oxygen is important for understanding and further improvement of the method. 相似文献
18.
Minkyung Kim Mohsin Ali Raza Anjum Min Choi Hu Young Jeong Sun Hee Choi Noejung Park Jae Sung Lee 《Advanced functional materials》2020,30(40)
Ultrasmall Co9S8 nanoparticles are introduced on the basal plane of MoS2 to fabricate a covalent 0D–2D heterostructure that enhances the hydrogen evolution reaction (HER) activity of electrochemical water splitting. In the heterostructure, separate phases of Co9S8 and MoS2 are formed, but they are connected by Co–S–Mo type covalent bonds. The charge redistribution from Co to Mo occurring at the interface enhances the electron‐doped characteristics of MoS2 to generate electron‐rich Mo atoms. Besides, reductive annealing during the synthesis forms S defects that activates adjacent Mo atoms for further enhanced HER activity as elucidated by the density functional theory (DFT) calculation. Eventually, the covalent Co9S8–MoS2 heterostructure shows amplified HER activity as well as stability in all pH electrolytes. The synergistic effect is pronounced when the heterostructure is coupled with a porous Ni foam (NF) support to form Co9S8–MoS2/NF that displays superior performance to those of the state‐of‐the‐art non‐noble metal electrocatalysts, and even outperforms a commercial Pt/C catalyst in a practically meaningful, high current density region in alkaline (>170 mA cm?2) and neutral (>60 mA cm?2) media. The high HER performance and stability of Co9S8–MoS2 heterostructure make it a promising pH universal alternative to expensive Pt‐based electrocatalysts for practical water electrolyzers. 相似文献
19.
Efficient Hydrogen Evolution Reaction Catalysis in Alkaline Media by All‐in‐One MoS2 with Multifunctional Active Sites 下载免费PDF全文
Mohsin Ali Raza Anjum Hu Young Jeong Min Hee Lee Hyeon Suk Shin Jae Sung Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(20)
MoS2 becomes an efficient and durable nonprecious‐metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from 1T‐phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS2‐based catalysts targeting only a single or few of these characteristics, the all‐in‐one MoS2 catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH3 molecules into MoS2 sheets affords ammoniated MoS2 (A‐MoS2) that predominantly comprises 1T‐MoS2 and exhibits an expanded interlayer spacing. The subsequent reduction of A‐MoS2 results in the removal of intercalated NH3 and H2S to form an all‐in‐one MoS2 with multifunctional active sites mentioned above (R‐MoS2) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS2‐based electrocatalysts. In particular, a hybrid MoS2/nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high‐current region (>25 mA cm?2), demonstrating that R‐MoS2‐based materials can potentially replace Pt catalysts in practical alkaline HER systems. 相似文献
20.