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排序方式: 共有132条查询结果,搜索用时 15 毫秒
21.
22.
E. M. S. Van Hamersveld J. J. G. S. Van Es A. L. German F. P. Cuperus P. Weissenborn A. -C. Hellgren 《Progress in Organic Coatings》1999,35(1-4):235-246
The combination of the characteristics of oil, or alkyd, emulsions and acrylic latexes in a waterborne binder has been the object of various studies in the past. Strategies for combining the positive properties of alkyds, e.g. autoxidative curing, gloss and penetration in wood, with the fast drying and gloss and color retention properties of acrylic latexes have mainly been directed towards the modification of the alkyd with an acrylate during alkyd synthesis followed by emulsification. This paper describes the preparation and application of oil-acrylic hybrid latexes as binders for waterborne coatings. The hybrid latexes were prepared using hydroperoxidized triglycerides as initiators for the mini-emulsion polymerization of acrylates in an Fe(II)/EDTA/SFS redox system. The particle morphology of hybrids initiated by fatty-acid hydroperoxides was compared with tert-butyl hydroperoxide-initiated systems. Cryo-TEM analysis indicated that, whereas tert-butyl hydroperoxide initiation resulted in the formation of heterogeneous particles, fatty-acid hydroperoxide-initiated hybrid particles showed no intra-particle heterogeneity. An AFM study of the film formation process of the oil/alkyd-acrylic hybrid latexes showed that phase separation occurred between the oil and the acrylic phases upon drying, resulting in films that consist of deformed acrylic particles embedded in a continuous matrix of oil. This results in a very smooth surface of the film. 相似文献
23.
Jie Dang Farzin Fatollahi-Fard Petrus Christiaan Pistorius Kuo-Chih Chou 《Metallurgical and Materials Transactions B》2018,49(1):123-131
In this study, reaction steps of a process for synthesis of titanium oxycarbide from titanium slag were demonstrated. This process involves the reduction of titanium slag by a methane-hydrogen-argon mixture at 1473 K (1200 °C) and the leaching of the reduced products by hydrofluoric acid near room temperature to remove the main impurity (Fe3Si). Some iron was formed by disproportionation of the main M3O5 phase before gaseous reduction started. Upon reduction, more iron formed first, followed by reduction of titanium dioxide to suboxides and eventually oxycarbide. 相似文献
24.
Viitanen P Suokas E Törmälä P Ashammakhi N 《Journal of materials science. Materials in medicine》2006,17(12):1267-1274
Due to inflammatory reactions complicating bioabsorbable devices, the aim of this study was to develop and characterize bioabsorbable
implants with anti-inflammatory drug releasing properties. Polylactide-co- glycolide (PLGA) 80/20 was compounded with diclofenac
sodium (DS) to produce rods. Thermal properties were analyzed using differential scanning calorimetry (DSC). Inherent viscosity
(ηinh) was measured to evaluate the drug effect on the extrude polymer. Drug release measurements were performed using UV-spectrophotometer.
Five parallel samples from each type of rods were examined, first at 6 hour intervals, then on daily basis, and later twice
a week. DS was released in 110 days from thinner rods and in 150 days from thicker rods. Drug release comprised a starting
peak, slow release phase, then a high release phase, and a burst release phase. DSC analysis showed that DS containing rods
had crystallinity in their structure. In conclusions, it is feasible to combine PLGA 80/20 and DS by using melt extrusion.
Released DS concentrations reached local therapeutic levels, but the release profile was complex and therapeutic levels were
not reached all the time. 相似文献
25.
Wei-Chun Cheng Yuan-Sheng Song Yu-Shan Lin Kuan-Fu Chen Petrus C. Pistorius 《Metallurgical and Materials Transactions A》2014,45(3):1199-1216
Lamellae of ferrite, kappa-carbide, and M23C6 carbide are involved in a eutectoid reaction of an Fe-C-Mn-Al alloy after isothermal holding at temperatures below 923 K (650 °C). These lamellar phases are product phases from the decomposition of austenite during the eutectoid reaction of the quaternary alloy, i.e., austenite → ferrite + kappa-carbide + M23C6 carbide. Since the Al concentration in the steel is higher than that of the eutectoid composition, proeutectoid ferrite and kappa-carbide appear in the austenite prior to the eutectoid reaction to reduce the Al content of the retained austenite. The retained austenite decomposes into ferrite, kappa-carbide, and M23C6 carbide during the eutectoid reaction. 相似文献
26.
Bart G. Muuse F. Petrus Cuperus Johannes T. P. Derksen 《Journal of the American Oil Chemists' Society》1994,71(3):313-317
Dimorphotheca pluvialis is increasingly recognized as an interesting industrial new oilseed crop because it contains up to 60% of the unusual fatty
acid dimorphecolic acid (9-hydroxy,10t,12t-18∶2) (DA) for which new applications are being developed. In this paper, the yield, composition and quality are evaluated
for dimorphotheca oils (DMO) which were recovered by pressing, conventional solvent extraction and supercritical carbon dioxide
extraction (SCE). Mechanical pressing of the seeds required high temperatures and resulted in an oil recovery of only 40%,
whereas the extraction protocols yielded more than 95%. Oil recovery by pressing of winged seed was even more difficult than
that of unwinged seeds; hence, solvent extraction of winged seeds was preferred. The dark-colored DMO, recovered by expelling
or by extraction with organic solvents, needed further refining to remove pigments and gums, whereas the light yellow-colored
SCE DMO did not require further refining. SCE oil had a low phospholipid content (11 mg P/kg). Pressed oil (95 mg P/kg) and
hexaneor pentane-extracted DMO (200 mgP/kg) had much higher phospholipid contents. Peroxide andp-anisidine values were low for freshly recovered oils, but increased after storage, especially in the SCE oil, due to the
low concentration of natural antioxidants in SCE DMO, such as tocopherols. The DA content of the oils recovered by the various
techniques showed only minor differences, except that supercritical carbon dioxide had slightly decreased solubilizing power
for tri- and di-dimorphecolin as compared to hexane and pentane. 相似文献
27.
Petrus J. Janse van Rensburg Albert A. Groenwold Derren W. Wood 《Structural and Multidisciplinary Optimization》2013,47(1):135-147
The use of flywheel rotors for energy storage presents several advantages, including fast response time, high efficiency and long cycle lifetime. Also, the fact that the technology poses few environmental risks makes it an attractive solution for energy storage. However, widespread application of tailorable circumferentially wound composite flywheel rotors is hampered by the relatively low energy density that these rotors have been able to achieve. This contributes to high capital cost, which currently makes the flywheels prohibitively expensive for many applications. With the materials that are currently available, there seems to be ample room for improvement in the energy density achieved by composite flywheel rotors. To this aim, some of the design methods that have previously been proposed are herein studied, and our findings suggest that the manner in which the optimization problem is formulated is crucial to the design of high energy density flywheels. A new problem formulation is proposed, which is shown to lead to notable improvements in certain cases. By making use of the proposed problem formulation, flywheel rotors can be designed to consistently achieve high energy density relative to the materials that are made available. This can contribute towards lowering the cost of flywheel systems, and making flywheel energy storage viable for a wider range of applications. 相似文献
28.
Proton exchange membrane (PEM) fuel cells operated with hydrogen and air offer promising alternative to conventional fossil fuel sources for transport and stationary applications because of its high efficiency, low‐temperature operation, high power density, fast start‐up and potable power for mobile application. Power levels derivable from this class of fuel cell depend on the operating parameters. In this study, a three‐dimensional numerical optimisation of the effect of operating and design parameters of PEM fuel cell performance was developed. The model computational domain includes an anode flow channel, membrane electrode assembly and a cathode flow channel. The continuity, momentum, energy and species conservation equations describing the flow and species transport of the gas mixture in the coupled gas channels and the electrodes were numerically solved using a computational fluid dynamics code. The effects of several key parameters, including channel geometries (width and depth), flow orientation and gas diffusion layer (GDL) porosity on performance and species distribution in a typical fuel cell system have been studied. Numerical results of the effect of flow rate and GDL porosity on the flow channel optimal configurations for PEM fuel cell are reported. Simulations were carried out ranging from 0.6 to 1.6 mm for channel width, 0.5 to 3.0 mm for channel depth and 0.1 to 0.7 for the GDL porosity. Results were evaluated at 0.3 V operating cell voltage of the PEM fuel cell. The optimisation results show that the optimum dimension values for channel depth and channel width are 2.0 and 1.2 mm, respectively. In addition, the results indicate that effective design of fuel gas channel in combination with the reactant species flow rate and GDL porosity enhances the performance of the fuel cell. The numerical results computed agree well with experimental data in the literature. Consequently, the results obtained provide useful information for improving the design of fuel cells. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
29.
Theresa Coetsee Johannes Nell Petrus Christiaan Pistorius 《Metallurgical and Materials Transactions B》2017,48(3):1463-1485
Slag chemistry applied in the AlloyStream process differs from that used in the production of high carbon ferromanganese in the submerged arc furnace. In process development of the AlloyStream process, several pilot plant and demonstration plant campaigns were completed. Slag samples were selected from the samples collected at each tap, throughout the four month pilot plant campaign. Phase characterization of these samples is reported here, and the results are interpreted in terms of the slag chemistry operational options in the AlloyStream process. 相似文献
30.