Porous silicon as an intermediate layer for thin-film solar cell

The potential of porous silicon (PS) with dual porosity structure as an intermediate layer for ultra-thin film solar cells is described. It is shown that a double-layered PS with a porosity of % allows to grow epitaxial Si film at medium temperature (725°–800°C) and at the same time serves as a gettering/diffusion barrier for impurities from potentially contaminated low-cost substrate. A 3.5 μm thin-film cell with reasonable efficiency is realized using such a PS intermediate layer.     

液相包覆制备Ce-TZP陶瓷的力学性能与稳定行为

采用XRD、SEM、TEM等分析手段对由液相包覆工艺制备的Ce—TZP陶瓷的微结构进行了研究，并和共沉淀粉体制备的Ce—TZP陶瓷进行了对比分析．力学性能表明，同共沉淀粉体制备的Ce—TZP陶瓷相比，由液相包覆工艺制备的Ce—TZP陶瓷虽硬度下降，但断裂韧性改善；液相添加少量Al2O3硬度随之增加、断裂韧性显著提高．电镜分析表明，液相包覆工艺制备的Ce—TZP陶瓷晶粒尺寸分布宽化，一部分晶粒尺寸较大但CeO2含量低、易发生马氏体相转变晶粒的存在是断裂韧性改善的主要原因．陶瓷体中单斜相大晶粒与四方相之间的残余应力、添加少量Al2O3在晶界上易形成薄的非晶包裹层，是增加可相变四方相数量，提高断裂韧性的其它机制。     

Structural Basis of Cysteine Ligase MshC Inhibition by Cysteinyl-Sulfonamides

Mycothiol (MSH), the major cellular thiol in Mycobacterium tuberculosis (Mtb), plays an essential role in the resistance of Mtb to various antibiotics and oxidative stresses. MshC catalyzes the ATP-dependent ligation of 1-O-(2-amino-2-deoxy-α-d-glucopyranosyl)-d-myo-inositol (GlcN-Ins) with l-cysteine (l-Cys) to form l-Cys-GlcN-Ins, the penultimate step in MSH biosynthesis. The inhibition of MshC is lethal to Mtb. In the present study, five new cysteinyl-sulfonamides were synthesized, and their binding affinity with MshC was evaluated using a thermal shift assay. Two of them bind the target with EC₅₀ values of 219 and 231 µM. Crystal structures of full-length MshC in complex with these two compounds showed that they were bound in the catalytic site of MshC, inducing dramatic conformational changes of the catalytic site compared to the apo form. In particular, the observed closure of the KMSKS loop was not detected in the published cysteinyl-sulfamoyl adenosine-bound structure, the latter likely due to trypsin treatment. Despite the confirmed binding to MshC, the compounds did not suppress Mtb culture growth, which might be explained by the lack of adequate cellular uptake. Taken together, these novel cysteinyl-sulfonamide MshC inhibitors and newly reported full-length apo and ligand-bound MshC structures provide a promising starting point for the further development of novel anti-tubercular drugs targeting MshC.     

Three-dimensional phase-field simulation of microstructural evolution in three-phase materials with different interfacial energies and different diffusivities

The coarsening behavior of three-phase materials, such as eutectic alloys, is of high technological interest. In this study, 3D ternary three-phase polycrystalline materials were modeled to study the effect of bulk diffusion and phase arrangement on the coarsening kinetics. The diffusion mobilities were defined to be different in the three phases. By varying the phase boundary and grain boundary energies, microstructures with different phase arrangements were obtained, in which the different types of grains had a tendency to alternate or cluster. In all cases, a regime was reached where the average grain size follows a power growth law with growth exponent \(n=3\), indicating bulk diffusion-controlled coarsening. The overall growth rate and that of the individual phases were clearly affected by the phase arrangement, the magnitude of the phase boundary energy and the diffusion mobilities of the different phases. In all cases, the phase with the lowest diffusion mobility showed the highest growth rate and on average a larger number of grain faces. While the average number of grain faces became constant in time in systems with constant grain boundary energy, the average number of grain faces continued to increase during the whole simulation time when the grain boundary energy was misorientation dependent.     

A Mathematical Description of the Kinetics of the Electrophoretic Deposition Process for Al2O3-Based Suspensions

The yield during electrophoretic deposition is modeled incorporating the changing electric field over the suspension, due to a potential drop over the growing deposit, assessed from on-line measurements of the current flowing through the deposition cell and the conductivity of the suspension during electrophoretic deposition. The kinetic model is validated for Al₂O₃ suspensions with different powder loads based on methylethylketone with n -butylamine and ethanol with polyethyleneimine or HNO₃, suspensions with, respectively, a constant and a decreasing electric field during deposition. The need for a powder concentration correction, even at volume fractions down to 0.03, and the incorporation of a changing electric field is experimentally proven to be essential in order to describe the deposition yield more accurately than predicted from the Hamaker equation.     

Yb2O3 and Y2O3 co-doped zirconia ceramics

A suspension stabilizer-coating technique was employed to prepare x mol% Yb₂O₃ (x = 1.0, 2.0, 3.0 and 4.0) and 1.0 mol% Y₂O₃ co-doped ZrO₂ powder. A systematic study was conducted on the sintering behaviour, phase assemblage, microstructural development and mechanical properties of Yb₂O₃ and Y₂O₃ co-doped zirconia ceramics. Fully dense ZrO₂ ceramics were obtained by means of pressureless sintering in air for 1 h at 1450 °C. The phase composition of the ceramics could be controlled by tuning the Yb₂O₃ content and the sintering parameters. Polycrystalline tetragonal ZrO₂ (TZP) and fully stabilised cubic ZrO₂ (FSZ) were achieved in the 1.0 mol% Y₂O₃ stabilised ceramic, co-doped with 1.0 mol% Yb₂O₃ and 4.0 mol% Yb₂O₃, respectively. The amount of stabilizer needed to form cubic ZrO₂ phase in the Yb₂O₃ and Y₂O₃ co-doped ZrO₂ ceramics was lower than that of single phase Y₂O₃-doped materials. The indentation fracture toughness could be tailored up to 8.5 MPa m^1/2 in combination with a hardness of 12 GPa by sintering a 1.0 mol% Yb₂O₃ and 1.0 mol% Y₂O₃ ceramic at 1450 °C for 1 h.     

ICT in teacher education in an emerging developing country: Vietnam’s baseline situation at the start of ‘The Year of ICT’

In many developing countries, integration of ICT is a key component of an educational reform agenda. These countries can draw on a tradition of research in the developed world on factors determining integration of ICT in education. In this tradition, this study investigates the current situation of ICT integration in teacher education in Vietnam, an emerging developing country at the beginning of integrating ICT in education. 783 educators of five Vietnamese teacher education institutions completed a questionnaire. This analysis illuminates teacher educators’ access to ICT, their intensity of use, their related skills, and their confidence in using ICT, as well as their conceptions of learning. Exploratory multiple regression analysis addresses the importance of these different factors at the level of the educator for use of ICT in teaching practice. Even though teacher educators adhere to a constructivist approach to student learning, the use of ICT applications in teaching practice remains limited, mostly replacing traditional teaching practices. The factors currently determining the use of ICT in teaching practice are ICT skills (β = .522) and computer confidence (β = .158). Suggestions are provided for the country to move beyond an access and skills based approach of integration of ICT in education and for emerging developing countries to cease the promise of ICT for education.     

High-temperature bending strength,internal friction and stiffness of ZrB2–20 vol% SiC ceramics

Dense ZrB₂–20 vol% SiC ceramics (ZS) were fabricated by hot pressing using self-synthesized high purity ZrB₂ and commercial SiC powders as raw materials. The high temperature flexural strength of ZS and its degradation mechanisms up to 1600 °C in high purity argon were investigated. According to the fracture mode, crack origin and internal friction curve of ZS ceramics, its strength degradation above 1000 °C is considered to result from a combination of phenomena such as grain boundary softening, grain sliding and the formation of cavitations and cracks around the SiC grains on the tensile side of the specimens. The ZS material at 1600 °C remains 84% of its strength at room temperature, which is obviously higher than the values reported in literature. The benefit is mainly derived from the high purity of the ZrB₂ powders.     

Formation of a Metastable Celsian-Cordierite Eutectic Structure During the Crystallization of a Ba-Osumilite Glass–Ceramic

This work addresses the formation conditions and stability of a celsian-cordierite eutectic structure produced during the crystallization of a barium magnesium aluminosilicate (BMAS) glass–ceramic with the Ba-osumilite stoichiometry. The melt-derived BMAS glass–ceramic was pulverized and subsequently hot pressed to produce sintered powder compacts, some of which were subjected to post-sintering heat treatments in air. The study of the devitrified BMAS glass revealed that a metastable celsian-cordierite eutectic structure resulted from the prolonged annealing of the BMAS glass–ceramic between 860° and 1000°C. The celsian-cordierite eutectic structure transformed to the thermodynamically stable Ba-osumilite phase when annealed at temperatures >1000°C.     

Advanced manufacturing concepts for crystalline silicon solar cells

An overview is given concerning current industrial technologies, near future improvements and medium term developments in the field of industrially implementable crystalline silicon solar cell fabrication. The paper proves that considerable improvements are still possible, both in efficiency and in production cost. The paper also proves that a lot of effort is being put worldwide on thinner substrates and on thin-film crystalline silicon cells deposited on cheap carriers, in order to save in substrate cost and in order to gain more independence from availability problems of silicon feedback