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81.
Bart Vermang Hans Goverde Loic Tous Anne Lorenz Patrick Choulat Jorg Horzel Joachim John Jef Poortmans Robert Mertens 《Progress in Photovoltaics: Research and Applications》2012,20(3):269-273
Atomic layer deposition (ALD) of thin Al2O3 (≤10 nm) films is used to improve the rear surface passivation of large‐area screen‐printed p‐type Si passivated emitter and rear cells (PERC). A blister‐free stack of Al2O3/SiOx/SiNx is developed, leading to an improved back reflection and a rear recombination current (J0,rear) of 92 ± 6 fA/cm2. The Al2O3/SiOx/SiNx stack is blister‐free if a 700°C anneal in N2 is performed after the Al2O3 deposition and prior to the SiOx/SiNx capping. A clear relationship between blistering density and lower open‐circuit voltage (VOC) due to increased rear contacting area is shown. In case of the blister‐free Al2O3/SiOx/SiNx rear surface passivation stack, an average cell efficiency of 19.0% is reached and independently confirmed by FhG‐ISE CalLab. Compared with SiOx/SiNx‐passivated PERC, there is an obvious gain in VOC and short‐circuit current (JSC) of 5 mV and 0.2 mA/cm2, respectively, thanks to improved rear surface passivation and rear internal reflection. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
82.
Roberto Martini Valerie Depauw Mario Gonzalez Kris Vanstreels Kris Van Nieuwenhuysen Ivan Gordon Jef Poortmans 《Nanoscale research letters》2012,7(1):597
Because of its optical and electrical properties, large surfaces, and compatibility with standard silicon processes, porous silicon is a very interesting material in photovoltaic and microelectromechanical systems technology. In some applications, porous silicon is annealed at high temperature and, consequently, the cylindrical pores that are generated by anodization or stain etching reorganize into randomly distributed closed sphere-like pores. Although the design of devices which involve this material needs an accurate evaluation of its mechanical properties, only few researchers have studied the mechanical properties of porous silicon, and no data are nowadays available on the mechanical properties of sintered porous silicon. In this work we propose a finite element model to estimate the mechanical properties of sintered meso-porous silicon. The model has been employed to study the dependence of the Young’s modulus and the shear modulus (upper and lower bounds) on the porosity for porosities between 0% to 40%. Interpolation functions for the Young’s modulus and shear modulus have been obtained, and the results show good agreement with the data reported for other porous media. A Monte Carlo simulation has also been employed to study the effect of the actual microstructure on the mechanical properties. 相似文献
83.
Annabel Braem Bram Neirinck Jan Schrooten Omer Van der Biest Jef Vleugels 《Materials science & engineering. C, Materials for biological applications》2012,32(8):2292-2298
In implant technology, open porous Ti coatings are applied as functional surface layers on prosthetic devices to improve osseointegration. Since a successful clinical performance strongly depends on the (initial) quality of bone ingrowth in the porous structure, surface functionalization of the porous Ti to incorporate an additional osteoconductive capacity is recommended. In this paper, a bioactive glass–ceramic coating is applied into the open porous network of Ti coatings with a pore throat size of 1–20 μm through a sol–gel process. Using an all-alkoxide precursor route, homogeneous amorphous powders of three- (SiO2–CaO–P2O5) and four-component (SiO2–CaO–Na2O–P2O5) bioactive glass compositions are prepared. By sol impregnation followed by a heat treatment, it is possible to deposit a micrometer thin bioactive glass–ceramic layer on the walls of the internal pore surface, while the original porosity and the open pore structure of the Ti coatings are maintained. The tensile adhesion strength of the Ti/bioactive glass–ceramic composite coatings is 22 to 29 MPa, suggesting a good mechanical adhesion. 相似文献
84.
R Loris MH Dao-Thi EM Bahassi L Van Melderen F Poortmans R Liddington M Couturier L Wyns 《Canadian Metallurgical Quarterly》1999,285(4):1667-1677
The crystal structure of CcdB, a protein that poisons Escherichia coli gyrase, was determined in three crystal forms. The protein consists of a five-stranded antiparallel beta-pleated sheet followed by a C-terminal alpha-helix. In one of the loops of the sheet, a second small three-stranded antiparallel beta-sheet is inserted that sticks out of the molecule as a wing. This wing contains the LysC proteolytic cleavage site that is protected by CcdA and, therefore, forms a likely CcdA recognition site. A dimer is formed by sheet extension and by extensive hydrophobic contacts involving three of the five methionine residues and the C terminus of the alpha-helix. The surface of the dimer on the side of the alpha-helix is overall negatively charged, while the opposite side as well as the wing sheet is dominated by positive charges. We propose that the CcdB dimer binds into the central hole of the 59 kDa N-terminal fragment of GyrA, after disruption of the head dimer interface of GyrA. 相似文献
85.
G Camus M Nys JR Poortmans I Venneman T Monfils G Deby-Dupont A Juchmès-Ferir C Deby M Lamy J Duchateau 《Canadian Metallurgical Quarterly》1998,7(6):413-415
Splenic injury is the most common abdominal organ injury in children who sustain blunt trauma and may result from apparently minor injuries. We present two cases of delayed diagnosis of splenic injury in children who fell from a moderate height of less than 10 feet. Careful physical examination and close follow-up with reevaluation are necessary to identify children with possible splenic injury after relatively minor blunt trauma. 相似文献
86.
Processing of ultrafine ZrO2 toughened WC composites 总被引:1,自引:0,他引:1
Olivier Malek Bert Lauwers Yeczain Perez Patrick De Baets Jef Vleugels 《Journal of the European Ceramic Society》2009,29(16):3371-3378
The interrelationships between the dispersion of the secondary ZrO2 phase and the material properties of WC-based composites with up to 10 vol% of ZrO2 are investigated. The homogeneity of the ultrafine WC–nanometric ZrO2 powder mixtures was optimized by means of multidirectional milling and bead milling. In an alternative route, zirconium butoxide was used as a ZrO2 source. The composites were fully densified by means of pulsed electric current sintering (PECS), also known as spark plasma sintering, within a few minutes at 1700 °C allowing to maintain an ultrafine grained microstructure combining a hardness of 2600 kg/mm2 with an indentation toughness of 6 MPa m1/2. The ZrO2 content and Y2O3 stabilization were found to strongly influence the mechanical properties and especially strength of the WC–ZrO2 composites. 相似文献
87.
88.
Willem F. Nieuwenhuizen Ilse Duivenvoorden Peter J. Voshol Patrick C. N. Rensen Wim van Duyvenvoorde Johannes A. Romijn Jef J. Emeis Louis M. Havekes 《European Journal of Lipid Science and Technology》2007,109(10):994-997
The prevalence of dyslipidemia and obesity resulting from excess energy intake and physical inactivity is increasing. The liver plays a pivotal role in the systemic lipid homeostasis. Effective, natural dietary interventions that lower plasma lipids and promote liver health are needed. APOE*3Leiden mice were fed a Western‐type diet, supplemented with different sphingolipids, to determine their effect on plasma lipids and liver steatosis. Hepatic lipid levels and lipid‐related gene expression were also determined. Dietary sphingolipids dose‐dependently lowered both plasma cholesterol (C) and triglycerides (TG) in APOE*3Leiden mice. 1% Phytosphingosine (PS) reduced C and TG by 57 and 58%, respectively. PS (a) decreased the absorption of dietary C and free fatty acid but did not affect the intestinal TG lipolysis, (b) increased hepatic VLDL‐TG production whereas plasma lipolysis was not affected; and (c) increased the hepatic uptake of VLDL remnants. Hepatic mRNA levels indicated enhanced hepatic lipid synthesis and VLDL and LDL uptake. Livers of PS (1%) fed mice were lighter (?22%), less pale, and contained less cholesteryl ester (?61%) and TG (?56%). Furthermore, markers for liver inflammation (SAA) and liver damage (ALAT) were decreased by 74% and 79%, respectively in PS‐fed mice. Sphingolipids lower plasma C and TG and protect the liver from fat‐ and cholesterol‐induced steatosis. In a preliminary small double‐blind cross‐over study with six middle‐aged slightly overweight male volunteers the daily supplementation of one gram of PS to the diet resulted in a ?9.8% (p = 0.0074) and – 13.2% (p = 0.0002) reduction of total C and LDL‐C, respectively. The C/HDL‐C ratio was not significantly affected (p = 0.0571). Due to the relatively low pre‐study levels of TG in the human volunteers, and the individual variability of TG levels, the TG lowering in humans was not significant in this first small study, but per individual there was a clear trend in TG lowering. 相似文献
89.
G. Beaucarne S. Bourdais A. Slaoui J. Poortmans 《Solar Energy Materials & Solar Cells》2000,61(3):301
In this paper, we study the diffusion of impurities from three types of foreign substrates (graphite, alumina and mullite) during thermal chemical vapour deposition (CVD) of a polycrystalline Si film. For this we use a rapid thermal CVD (RTCVD) system and characterization techniques such as secondary ion mass spectroscopy (SIMS) and deep level transient spectroscopy (DLTS). Results show that, in the case of materials like graphite, metallic contaminants can freely outdiffuse into the deposited layer and the environment. In contrast, the ceramic substrates release only a very limited amount of contaminants during the CVD process, making the need of a diffusion barrier much less severe. 相似文献
90.
David Cheyns Hans Gommans Mathieu Odijk Jef Poortmans Paul Heremans 《Solar Energy Materials & Solar Cells》2007,91(5):399
In order to improve photon harvesting, two small molecule organic solar cells are placed in series on top of each other. These stacked cells need an efficient recombination center in between both cells. In this study we test vacuum deposited metal layers as recombination centers with pentacene and buckminsterfullerene (C60) as donor and acceptor, respectively. S-shaped curves are visible in the I–V characteristics when using thin layers of aluminum, indicating a barrier for extraction inside the device. Thin metal layers of gold or silver result in an increased open-circuit voltage without the appearance of these S-shaped features. 相似文献