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991.
992.
Mathematical simulation of wet spinning coagulation process: Dynamic modeling and numerical results
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Nan Xu Yongsheng Ding William E. Schiesser Mayuresh V. Kothare 《American Institute of Chemical Engineers》2016,62(9):3432-3440
A dynamic model of polymer wet spinning coagulation process is proposed in this article. The model is based on the double diffusion phenomenon, phase separation process, continuity balance, and momentum balance of the entire coagulation process. The uniqueness of the model lies in its dynamic feature. The model can simulate the system's dynamic response to variations in system inputs/parameters. Steady‐state system solutions can also be produced as the long‐time solutions of the dynamic model; a settling time can be observed at the same time. This paper employs a computationally efficient method of lines numerical algorithm for solving the dynamic model. A simulation experiment on a selected non‐solvent‐solvent‐polymer ternary system is carried out to verify the model as well as the numerical method. The dynamic simulation results are analyzed and discussed. At the end of the article, h‐refinement and p‐refinement are used to confirm the spatial convergence of the numerical solutions. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3432–3440, 2016 相似文献
993.
Development of thermally conductive polymer matrix composites by foaming‐assisted networking of micron‐ and submicron‐scale hexagonal boron nitride
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Thermally conductive polymer matrix composite (PMC) foams with effective thermal conductivities (keff) higher than their solid counterparts have been developed for the first time. Using a material system consists of low density polyethylene and micron‐scale or submicron‐scale hexagon boron nitride platelets as a case example, this article demonstrates that foaming‐assisted filler networking is a feasible processing strategy to enhance PMC's keff, especially at a low hBN loading. Parametric studies were conducted to identify the structure‐to‐property relationships between foam morphology (e.g., cell population density, cell size, and foam expansion) and the PMC foam's keff. In particular, there exists an optimal cell size to maximize the PMC foam's keff for foams with up to 50% volume expansion. However, an optimal cell size is absent for PMC foams with higher volume expansion. X‐ray diffraction (XRD) analyses reveal that both the presence of hBN platelets and foam expansion promoted the crystallization of LDPE phase. Moreover, the XRD spectra also provide evidence for the effect of foam expansion on the orientation of hBN platelets. Overall, the findings provide new directions to design and fabricate thermally conductive PMC foams with low filler contents for heat management applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42910. 相似文献
994.
Transfer function and working principle of a pressure/temperature sensor based on carbon black/silicone rubber composites
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Pressure/temperature sensitive silicon rubber (SR) filled with carbon black (CB) was prepared by a liquid mixing method. The transfer function of a pressure/temperature sensor based on CB/SR was derived by general effective media theory. The results show that the transfer functions coincided well with the experimental data, and the negative pressure coefficient of the resistance/positive temperature coefficient of resistance are shown. The working principles of these two kinds of sensors are different. The working principle of the pressure sensor based on CB/SR was related to the volume fraction of CB. With increasing volume fraction of CB, the working principle of this kind of pressure sensor varied from a piezo‐resistive effect to a strain effect. In addition, the working principle of the temperature sensor based on CB/SR was that the resistivity changed with temperature; this was not related to the volume fraction of CB. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42979. 相似文献
995.
Xiaoyu Ding Jianhua Liu Tequila A. L. Harris 《American Institute of Chemical Engineers》2016,62(7):2508-2524
Slot die coating is a pre‐metered process commonly used for producing thin and uniform films. It is an important film fabrication method for applications where precise coating is required. A major concern in slot die coating processes is how to determine the operating limits to set the appropriate range of operating parameters, including coating speed, flow rate, vacuum pressure, coating gap, liquid viscosity and surface tension, etc. Operating limits directly determine the effectiveness and efficiency of the process. In this article, the current state of academic research on operating limits in slot die coating processes is reviewed. Specifically, the theories, mechanisms, and empirical conclusions related to the limits on vacuum pressure, the low‐flow limit, the limit of wet thickness for zero‐vacuum‐pressure cases, the limit of dynamic wetting failure, and the limits of coating speed for a specific flow rate are reviewed. The article concludes with some recommendations for future work. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2508–2524, 2016 相似文献
996.
Facile growth of 1‐D nanowire‐based WO3 thin films with enhanced photoelectrochemical performance
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A flame reactor embedded with a constant tungsten wire feeding system to prepare one‐dimensional (1‐D) nanostructured tungsten oxide thin film for photoelectrochemical (PEC) water splitting was developed. Photoactive vertically‐aligned nanowire‐based WO3 thin films could be obtained with a controlled thickness via a flame vapor deposition process followed by air‐annealing. The PEC performances of WO3 photoelectrodes for different thin film thicknesses were examined. The optimum thickness of WO3 thin film was found to be about 7.2 μm for PEC water splitting based on incident photon‐to‐current efficiency plots and I–V curves. The WO3 prepared with optimum thickness showed better PEC performance than those of recently reported nanostructured WO3 photoanodes. © 2015 American Institute of Chemical Engineers AIChE J, 62: 421–428, 2016 相似文献
997.
Large Piezoelectricity and Ferroelectricity in Mn‐Doped (Bi0.5Na0.5)TiO3‐BaTiO3 Thin Film Prepared by Pulsed Laser Deposition
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Qianru Lin Rui Ding Qian Li Yee Yan Tay Danyang Wang Yun Liu Yizhong Huang Sean Li 《Journal of the American Ceramic Society》2016,99(7):2347-2353
Mn‐doped (Bi0.5Na0.5)0.94Ba0.06TiO3 (MnBNBT) thin films were prepared on SrRuO3 (SRO)‐coated (001) SrTiO3 (STO) single crystal substrates by pulsed laser deposition under different processing conditions. Structural characterization (i.e., XRD and TEM) confirms the epitaxial growth of STO/SRO/MnBNBT heterostructures. Through the judicious control of deposition temperature, the defect level within the films can be finely tuned. The MnBNBT thin film deposited at the optimized temperature exhibits superior ferroelectric and piezoelectric responses with remanent polarization Pr of 33.0 μC/cm2 and piezoelectric coefficient d33 of 120.0 ± 20 pm/V. 相似文献
998.
Li2O–MgO–TiO2 ternary system is an important microwave dielectric ceramic material with excellent properties and prospect in both scientific research and application. A phase diagram of the Li2O–MgO–TiO2 ternary system was established in this article, based on earlier research results and our present work. Microwave dielectric properties with compositions in different regions of the phase diagram have been analyzed. We found that the 0.33 Li2MgTi3O8–0.67 Li2TiO3 ceramics sintered at 1200°C exhibited excellent dielectric properties: Q × f value = 80 476 GHz (at 7.681 GHz), εr = 24.7, τf = +3.2 ppm/°C. We also designed two ceramic systems in the Li‐rich region of the Li2O–MgO–TiO2 ternary system, which received little attention in the past decades, because many excellent single‐phase ceramics, such as Li2MgTiO4, Li2MgTi3O8 and MgTiO3, have been found in the Ti‐rich region. The ceramic systems have low sintering temperatures but also relatively poor dielectric properties. 相似文献
999.
1000.