Fabrication of double sided buried contact (DSBC) silicon solar cell by simultaneous pre-deposition and diffusion of boron and phosphorus

Double Sided Buried Contact (DSBC) silicon solar cells have recently been developed at the University of New South Wales. The processing sequence requires three high temperature steps. These three high temperature steps have been reduced to two by simultaneous pre-deposition and diffusion of boron and phosphorus using the spin-on sources. The preliminary results of DSBC cells fabricated by fewer (two) high temperature steps have demonstrated energy conversion efficiency close to 15% for planar substrates. This efficiency should translate into efficiency in excess of 17% with the inclusion of surface texturing.     

Development of an emitter for industrial silicon solar cells using the doped oxide solid source diffusion technique

The aim of this paper is to demonstrate for the first time the feasibility of fabricating large-area screen-printed monocrystalline silicon solar cells using the Doped Oxide Solid Source (DOSS) diffusion technique. This process was applied to form the n⁺p emitter junction from highly doped sources prepared in a POCl₃ ambient. The diffusions were performed under a pure nitrogen flow in the temperature range 900–1050°C. In this investigation attention was devoted to the influence of the source doping level on the fill factor. The solar cells were fabricated on industrial quality 4-inch Cz wafers using a simple processing sequence incorporating screen-printed contacts and a TiO₂ antireflection coating deposited by spin-on. Fill factors as high as 79% were obtained. The potential benefit of retaining for passivation purposes the thin residual oxide grown during phosphorus diffusion was evaluated. These first experiments led to a cell efficiency close to 10%.     

Hydrogen adsorption on calcium,potassium, and magnesium-decorations aluminene using density functional theory

A low-cost hydrogen storage with high capacity is still a bottleneck to achieve a hydrogen economy for a sustainable clean fuel cell vehicle. Aluminene has been identified as a potential hydrogen storage material due to its high surface area. In this work, calcium, potassium, and magnesium were introduced at low concentrations as interstitial dopants to planar aluminene to determine its effects on hydrogen adsorption using density functional theory. Results showed that these impurities can easily be chemisorped with absolute binding energies ranging from 0.95 eV to 3.50 eV on the top, bridge, and hollow sites of aluminene in ascending order. This chemisorption is validated by the overlapping of sp orbitals between the dopant atoms and aluminum as shown in the density of states. Electron transfer from the aluminum to the dopant atoms were observed in the charge density difference allowing reactivity of the hydrogen atoms to the dopants. These materials have zero magnetization and remained metallic. Furthermore, hydrogen molecules were physisorped near the dopants with absolute adsorption energies ranging from 23 meV to 81 meV which would be suitable as a storage material near room temperature. Finally, the calculated gravimetric densities show that aluminene with impurities at low concentrations can still be potential hydrogen storage materials.     

Integrated study of lead iodide crystal growth and doping processes

Due to its high atomic number, high density and wide band-gap energy, lead iodide is a promising nuclear-radiation detector material. The radiative transition in PbI₂ is mainly due to donor–acceptor pair (D–A) recombination associated with impurities, which suggests improving scintillating performance of lead iodide by doping certain impurities. Before the doping study, high-purity PbI₂ with the least undetermined impurities is obtained by purifying the commercial PbI₂ with zone-refining technique. After well mixed with certain dopants (AgI and LaI₃), the purified PbI₂ is used as starting material for single crystal growth by vertical Bridgman method. Numerical studies are conducted to study temperature fields in both zone-melting and Bridgman furnaces. The solid/liquid interface is determined according to the heat balance on the growth front. The results are found to agree well with experimental measurements. Distribution of impurity concentration in purified ingot is studied experimentally, while that in grown crystal is studied analytically. By comparing analytical solutions with experiments, the effective redistribution coefficients of dopants in lead iodide crystal are determined. We further conclude that diffusion-dominated mechanism of dopant redistribution accounts for the uniform distribution of dopants in crystal, and that the suppression of natural convection in the melt is critical. By integrated study of heat and mass transfer phenomena during purification and growth processes of lead iodide, important information is achieved for the understanding and improvement of hot-zone design in the furnaces as well as for the parametric optimization of both processes.     

核电高压加热器管端坡口加工工艺改进

针对火电高压加热器管端坡口加工质量较差、效率低的缺点,对核电高压加热器管端坡口的加工工艺进行改进,详细描述了工艺过程及对动力装置、夹具和刀具的改进,实现了刀片的快速装卸、定位及夹紧,改进后的加工工艺提高了加工质量、生产效率,为某型核电高压加热器的管端坡口加工提供了可靠的技术保障,具有良好的经济效益和应用价值。     

Experimental Thermal Performance Characterization of Flat Grooved Heat Pipes

ABSTRACT

The thermal characterization of aluminum flat grooved heat pipes is performed experimentally for different groove dimensions. Three heat pipes with groove widths of 0.2?mm, 0.4?mm, and 1.5?mm are used in the experiments. The effect of the amount of the working fluid is extensively studied for each groove width. The results reveal that, although all three succeed in dissipating the heat input through the phase change of the working fluid by continuous evaporation and condensation, the effectiveness of the heat transfer increases with reduced groove width. Furthermore, it is observed that there exists an optimum operating point, where the temperature difference between the heating and cooling sections is at a minimum, and the magnitude of this temperature difference is a strong function of the groove width. To the best of the authors’ knowledge, the combined effects of groove dimensions and the amount of the working fluid, from fully flooded to dry, is reported for the first time for aluminum flat grooved heat pipes.     

喷油泵柱塞控油槽设计的一种解析方法

直列式喷油泵柱塞控油槽通常采用斜槽和螺旋槽式，通过柱塞的往复运动与转动，改变油孔与控油槽的相对位置，使供油量发生变化来满足柴油机的运转要求。控油斜槽的设计一般采用作图法和解析法。作图法简单易行，但有较大误差；现有解析法运算较为复杂，工程设计中不易应用。柱塞控油斜槽设计的一种新的解析方法，不仅避免了作图法误差较大的缺点，还具有比现有解析法更方便、快捷的优点。     

Effects of doping on the optical fiber drawing process

Optical fibers are typically drawn from silica preforms, which usually consist of two concentric cylinders called the core and the cladding, heated in a high-temperature furnace. For optical communication purposes, the core generally has a higher average refractive index than the cladding to obtain total internal reflection. This paper investigates the effects of adding dopants to the core or to the cladding, to change the refractive index values, on the optical fiber drawing process. Employing an analytical/numerical model developed earlier to simulate the core-cladding structure of a typical optical fiber, the paper considers different dopants and the effects resulting from the consequent changes in properties, particularly the radiation absorption properties, on the temperature distributions, flow, neck-down profile, thermally induced defects and draw tension. The zonal method is applied to model the radiation transfer in the glass perform and the purge gas is taken as non-participating. The numerical model has been validated by comparing with results available in the literature, wherever possible. It is found that the effects are significant because of changes in refractive index and absorption of radiation, which give rise to significant changes in temperature and tension. These can, in turn, substantially affect fiber quality and characteristics. Therefore, for an accurate and realistic modeling of the process, the effects of property changes due to dopants on the draw process must be included.     

Growth of highly c-axis oriented Mg:ZnO nanorods on Al2O3 substrate towards high-performance H2 sensing

Highly c-axis oriented Mg:ZnO films were fabricated on Al₂O₃ substrate by radio frequency sputtering for different substrate temperatures. The crystal structure revealed that the Mg dopants are well integrated into ZnO wurtzite lattice. X-ray photoelectron spectroscopy measurements also confirmed the successful incorporation of Mg into ZnO. The substrate temperature exhibit significant influence on the optical absorbance and band gap of Mg:ZnO films. Scanning electron microscope images revealed the formation of Mg:ZnO nanorods with good crystalline quality. The films prepared at 1200 °C show well grown rods of Mg:ZnO due to strengthening of the preferred orientation of ZnO along the c-axis. The Mg:ZnO/Al₂O₃ films prepared at different temperature were tested for its sensing performance towards 200 ppm of H₂ at room temperature. The Mg:ZnO sensor prepared at 1200 °C revealed fast response and recovery time of about 85 s and 70 s, respectively. The response of the sensor was linear to H₂ concentration in the range of 100–500 ppm. It can be summarized that this high performance H₂ sensor has potential for use as a portable room temperature gas sensor.     

A review on carbon nanotube/polymer composites for organic solar cells

Carbon nanotubes (CNTs) have unique properties, such as their electrical conductivity, that enable them to be combined with conducting polymers to form composites for use in organic solar cells (OSCs). It is envisaged that the improved composite has a higher efficiency of green energy and will reduce the cost of these cells. The use of such alternative energy sources also drastically reduces overuse of fossil fuels and consequently limits environmental degradation. This review compares research and performance between conventional silicon solar cells and OSCs. It also discusses OSC photoexcitation and charge carrier generation with the incorporation of CNTs, physicochemical properties of the composites and other factors that affect the efficiencies of OSCs. In addition, properties of CNTs that favour their dispersion in polymer matrices as acceptors and charge carriers to the electrodes are covered. The effects of CNTs containing dopants, such as nitrogen and boron, on charge transfer are discussed. Also, the fabrication techniques of OSCs that include CNT/polymer composite processing and the methods of film deposition on the substrate are described. Finally, the case studies of OSCs containing polymers with single‐walled CNTs, double‐walled CNTs or multi‐walled CNTs are evaluated. Copyright © 2014 John Wiley & Sons, Ltd.     

Adaptation of drafting plotter for buried contact groove formation

Lasers (e.g. Nd-YAG) have been used extensively for groove formation both in laboratories and commercial production but the initial capital cost is high. The production throughput is also low and thus adds to the cost of the cell. To reduce cost and increase production throughput a drafting plotter has been adapted to serve as a mechanical scriber for groove formation. The adapted plotter can scribe cells in matrix form to reduce the human labour and increase the production throughput. The characterization of the scribing tips in conjunction with the plotter showed that the best yield for the scriber is obtained when the scribing tip is mounted at 78° to the stock. Of the seven characterized scribing tips, the 90° conical scriber has been found to give the same groove geometry as the laser. The application of the adapted plotter to cell fabrication did not show any significant deterioration in the electrical output parameters for the mechanically scribed cells when compared with laser scribed cells. This article reports the adaptation of the x-y table drafting plotter to form buried contact grooves.     

不锈钢中厚板激光全熔透焊的有限元模拟

运用有限元计算软件ABAQUS对16mm厚不锈钢板的激光全熔透焊的温度场和应力场进行了模拟.采用一体两面的复合焊接热源模型来刻画激光全熔透焊过程中的热输入特征,以柱状体热源代表焊接小孔传热模式,以2个超高斯面热源代表等离子体/金属蒸气云对熔池的辐射传热模式.结果表明:温度场模拟结果得到了与实验结果相一致的"沙漏状"焊缝;钢板内纵向残余应力最大,横向应力次之,板厚方向横向应力最小;纵向拉应力主要分布在焊缝两侧约25mm的区域内,最大值已超过材料的屈服强度;经测算,钢板焊后的角变形量仅为0.35°,这是由于激光焊接能量输入高且集中、可不用开坡口而一次性将钢板焊透.     

不同开槽方式的椭圆瓦轴承润滑性能对比研究

为解决某电厂开槽椭圆瓦轴承在运行过程中存在温度过高的问题,考虑紊流、质量守恒边界等效应建立了轴承的热流体动力学润滑分析模型,采用有限元法求解了轴承性能,对比得出了四种不同开槽方式的椭圆瓦轴承对润滑性能(膜厚、膜压、膜温、功耗和流量等)的影响规律。结果表明:相对于上下瓦均不开槽(光滑表面)轴承,下瓦开中心槽导致油膜承载面积减小,油膜厚度大幅降低,油膜压力和油膜温度均显著升高;上瓦开槽对轴承性能影响较小,整体上降低了摩擦功耗,但略微增加油膜温度。     

Low-temperature growth of highly crystallized transparent conductive fluorine-doped tin oxide films by intermittent spray pyrolysis deposition

Following the procedure by Sawada et al. (Thin Solid Films 409 (2002) 46), high-quality SnO₂:F films were grown on glass substrates at relatively low temperatures of 325–340°C by intermittent spray pyrolysis deposition using a perfume atomizer for cosmetics use. Even though the substrate temperature is low, as-deposited films show a high optical transmittance of 92% in the visible range, a low electric resistivity of 5.8×10⁻⁴ Ω cm and a high Hall mobility of 28 cm²/V s. The F/Sn atomic ratio (0.0074) in the films is low in comparison with the value (0.5) in the sprayed solution. The carrier density in the film is approximately equal to the F-ion density, suggesting that most of the F-ions effectively function as active dopants. Films’ transmittance and resistivity show little change after a 450°C 60 min heat treatment in the atmosphere, evidencing a high heat resistance. The SnO₂:F films obtained in this work remove the difficulty to improve the figure of merit at low synthesis temperatures.     

Analysis on flow structure and improvement of heat transfer in 3D circular tube with varying axial groove turbulator configurations

Using passive devices are an efficient method to enhance streamline behavior when liquid flows through the circular pipe. The interrupted structure groove is usually used to change the flow patterns. In this analysis, a heat performance numerical technique is applied to study the characteristics of fluid flow and heat transfer of the circular pipe using different axial groove geometrical configurations with different axial groove numbers, including 2, 3, and 4, under different conditions. The number of annular grooves and circumferential positions are the important parameters to analyse with varying operating conditions, with the Reynolds number (Re) range from 1500 to 23,000. A three-dimensional coordinate pipe system is applied using tetrahedron grids. The discretization equations are obtained by deriving algebraic approximations to integral conservation equations. Results observed that using this type of passive method has a low effect on pressure dope compared to the normal one (smooth pipe). The flow change occurs near and closed to the axial groove parameters. Moreover, the Nusselt number (Nu) value for the groove turbulators was higher than the normal one, about 14.5%–21%. The friction factor (f) value for the groove turbulators was higher than the normal one, were about 7.5%–24%. Most friction losses are caused by dynamical pressure dissipation owing to more viscous losses closed to the wall surfaces. The improvement of heat performance using this type of passing method was more than 1.2%.     

柴油机气缸套密封胶圈环槽温度测量研究

本文介绍了采用自制热电偶测量柴油机气缸套密封胶圈环槽温度的研究。研究采用电火花微孔钻孔设备,在气缸套密封胶圈环槽位置打盲孔,并焊接热电偶,引出连接线,在柴油机试验台架上进行温度测量。分析测量结果,为气缸套密封胶圈的选择提供依据。     

PCBN刀具在活塞铸铁环槽加工中的应用

根据PCBN刀具材料的力学、物理、化学性能以及铝活塞铸铁镶环的性能及特点,结合铝活塞铸铁环槽的加工方式,采用试验研究对比了粘合剂比例和刀具角度对PCBN刀具寿命的影响。结果表明,粘合剂占比为20%时刀具使用寿命最高,较粘合剂占比10%时使用寿命提高近5.9倍;而将刀具由单侧偏角改为双侧偏角后,使用寿命也提高了近2倍。本文研究对提高铝活塞铸铁环槽加工效率及延长刀具使用寿命有重要的现实意义。     

Stability, durability, and reusability studies on transition metal-doped Co–B alloy catalysts for hydrogen production

In addition to high catalytic efficiency the catalyst must also comprise important features like high stability in severe conditions, ability to be recycled several times and should have high tolerance against deactivation. This work is oriented specifically to study these properties of already developed efficient transition-metal doped Co–B alloy catalyst. Various transition metals, namely Ni, Fe, Cu, Cr, Mo, and W, were singly added as dopants in Co–B catalyst by chemical reduction of the corresponding metal salts. These alloy catalysts were calcinated, in Ar atmosphere, at 673, 773, and 873 K in order to investigate the stability of the powders at elevated temperatures. The catalytic performances of these treated catalyst powders were tested for H₂ generation by catalytic hydrolysis of sodium borohydride (NaBH₄). The alloy powders were exposed to ambient condition for several days to test their tolerance against deactivation and self life. After separation from the reaction course and after rinsing, the catalyst powders were tested for several cycles to evaluate the reusability property. The observed changes in the catalytic activity were discussed on the basis of structural and morphological variations. The Co–B catalyst, when doped with Ni, Mo, and W metals showed high stability and resistance against deterioration, as function of both time and use, as compared to Cr- and Fe-doped alloy powders. A much lower performance with respect to calcination temperature, holding time, and number of cycles was established for Cu doped Co–B catalyst powder.     

Thermal and hydraulic characteristics of turbulent nanofluids flow in a rib–groove channel

Thermal and hydraulic characteristics of turbulent nanofluids flow in a rib–groove channel are numerically investigated. The continuity, momentum and energy equations were solved by means of a finite volume method (FVM). The top and bottom walls of the channel are heated at a constant temperature. Nine different rib–groove shapes are considered in this study, which are three different rib shapes with three different groove shapes including rectangular, triangular and trapezoidal and they are interchanged with each other. Four different types of nanoparticles Al₂O₃, CuO, SiO₂, and ZnO with different volume fractions in the range of 1% to 4% and different nanoparticle diameters in the range of 25 nm to 80 nm, are dispersed in different base fluids (water, glycerin, engine oil) are used. In this study, several parameters such as different Reynolds numbers in the range of 5000 < Re < 20000, and different rib–groove aspect ratios in the range of 0.5 ≤ AR ≤ 4 are also examined to identify their effects on the heat transfer and fluid flow characteristics. The results indicate that the rectangular rib–triangular groove has the highest Nusselt number among other rib–groove shapes. The SiO₂ nanofluid has the highest Nusselt number compared with other nanofluid types. The Nusselt number increased as the nanoparticle volume fraction, Reynolds number and aspect ratio increased; however, it decreased as the nanoparticle diameter increased. It is found that the glycerin–SiO₂ shows the best heat transfer enhancement compared with other tested base fluids.     

Novel front end processing method of industrial beet juice extraction for biofuels and bioproducts industries

Conventional raw beet juice extraction in food-grade crystal sugar production is a highly involved and energy intensive process, which includes beets washing, thawing of frozen beets, cossettes slicing, and high temperature denaturation and diffusion. Industrial beets, a new feedstock bred for non-food industrial use, processing for biofuel and bioproducts applications can use less stringent quality requirements and simplify the juice extraction process. A novel simplified front end processing (FEP), which is less expensive, energy efficient, and involved only common equipment (hammer mill and basket press), was developed and tested. The hammer mill pulverized the beets and basket press extracted the juice. Four beet conditions (fresh, frozen, thawed and fresh-frozen) and four presses with water addition were tested for juice extraction. The juice concentration had decreased with the increased number of presses, and the fitted exponential equations (R² ≥ 0.97) determined the juice concentration as a function of number of presses. Frozen beets consistently produced significantly high concentration juice followed by fresh-frozen, thawed, and fresh beets. Freezing had a beneficial effect in increasing the cumulative approximate sugar extracted. Two presses for fresh (92%) and three for frozen (97%) beets extracted the most available sugars. Future research may focus on water temperature, beet particle size, juice for extraction, microbial stability, energy economics, and products utilization. This new FEP efficiently extracts industrial beet juice and has direct scope in industry deployment as well as enhances the potential of the fuel generated being recognized as an advanced biofuel by the renewable fuel standards.