共查询到20条相似文献,搜索用时 453 毫秒
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采用H2、NH3和H2 NH3等离子体在沉积氮化硅薄膜之前对多晶硅片进行预处理,采用等离子增强化学气相沉积(PECVD)制备氮化硅薄膜,然后印刷烧结.利用准稳态光电导衰减法(QSSPCD)、傅里叶红外光谱仪(FT-IR)和紫外可见近红外分光光度计(UV-VIS)等手段研究了等离子体预处理对多晶硅少子寿命的影响以及等离子体预处理对氮化硅薄膜FTIR光谱的影响和多晶电池性能的影响.结果表明:经等离子体预处理后多晶硅的少子寿命有所提高,使用H2 NH3混合等离子体预处理后,制备的多晶电池的性能有明显提高,短路电流能提高约7%. 相似文献
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采用等离子体增强化学沉积的方法(PECVD),在低衬体温度下制备不同厚度的双面氮化硅薄膜,通过准稳态电导法(QSSPCD)测试non-diffused和diffused硅片沉积不同厚度双面氮化硅薄膜烧结前后的少子寿命,研究发现,氮化硅薄膜厚度在17 nm左右的时候,背面钝化效果有所下降,超过26 nm的时候,效果基本一致.non-diffused烧结后的少子寿命下降很大,而diffused与之相反.结果表明,采用氮化硅作为背面钝化介质膜,可以改善材料的少子寿命,背面钝化膜可以选择在26~75 nm之间. 相似文献
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PECVD SiO_2-SiN_X叠层钝化膜的研究 总被引:1,自引:0,他引:1
首先使用正交设计法对SiN_X和SiO_2膜的PECVD(等离子体增强化学气相沉积)特性进行了研究,分别得到了两种膜的最佳沉积条件。然后使用PECVD在P型多晶硅片发射极上沉积了SiO_2-SiN_X叠层钝化膜,并与SiN_X单层钝化膜进行比较。通过测试硅片在退火前后少子寿命的变化,考察了两种钝化膜对太阳电池发射极的钝化效果,结果表明SiO_2-SiN_X叠层膜具有更好的钝化效果。利用反射率测试仪测试了两种膜的反射率,其反射率曲线基本相同。最后,测量了采用该叠层膜制作的太阳电池的量子效率和电性能,其短路电流和开路电压均比采用SiN_X单层膜的电池要好,转换效率提高了0.25%。 相似文献
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主要研究在晶体硅衬底上采用干氧氧化法生长SiO2薄膜,通过改变非晶SiO2薄膜的生长温度、时间以及气体流量等参数优化工艺条件,增强对硅片的钝化作用,提高光生少数载流子寿命.实验发现在840℃下生长的非晶SiO2薄膜对硅片钝化效果最佳,可将硅片少子寿命提高约90%.此外,为优化SiO2/SiNx双层膜的减反射作用,采用Matlab程序计算SiO2/SiNx双层膜的反射谱,从理论上获得最优的膜系组合.实验发现生长有SiO2钝化膜的SiO2/SiNx双层膜太阳电池相对单层SiNx膜太阳电池,短路电流和开路电压分别提高了0.2A和8mV,转换效率提高约9%. 相似文献
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The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°, −5°, +5°, +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods. 相似文献
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A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified. 相似文献
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As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied. 相似文献
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Water pumping has been one of the main applications for wind power in the past and despite the spread of mains-electric pumps, more than a million windpumps remain in regular use. This paper reviews the general technical and economic requirements for pumping water using wind energy and by way of example gives an overview of the development of the new ITP wind-pump. It then considers the future prospects for this kind of technology. 相似文献
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Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials 总被引:4,自引:0,他引:4
Ronnen Levinson Paul Berdahl Hashem Akbari William Miller Ingo Joedicke Joseph Reilly Yoshi Suzuki Michelle Vondran 《Solar Energy Materials & Solar Cells》2007,91(4):304-314
We describe methods for creating solar-reflective nonwhite surfaces and their application to a wide variety of residential roofing materials, including metal, clay tile, concrete tile, wood, and asphalt shingle. Reflectance in the near-infrared (NIR) spectrum (0.7–2.5 μm) is maximized by coloring a topcoat with pigments that weakly absorb and (optionally) strongly backscatter NIR radiation, and by adding an NIR-reflective basecoat (e.g., one colored with titanium dioxide rutile white) if both the topcoat and the substrate weakly reflect NIR radiation. Coated steel and glazed clay-tile roofing products achieved NIR reflectances of up to 0.50 and 0.75, respectively, using only cool topcoats. Gray-cement concrete tiles achieved NIR reflectances as high as 0.60 with coatings colored by NIR-scattering pigments. Such tiles could attain NIR reflectances of up to 0.85 by overlaying a white basecoat with a topcoat colored by NIR-transparent organic pigments. Granule-surfaced asphalt shingles achieved NIR reflectances as high as 0.45 when the granules were covered with a white basecoat and a cool color topcoat. 相似文献
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The thermal decay of an initially hot isothermal water body contained in a tank was studied. Analytical solutions (including a group-theoretic solution) were obtained for the one-dimensional heat conduction equation with heat loss from the sides of the tank. The convective heat transfer coefficient was assumed not to be constant over the surface of the tank but to vary with space and time. A very good agreement was obtained between the group-theoretic solution and a numerical solution using the Crank-Nicholson finite difference scheme. The analytical results are discussed in terms of the underlying physical mechanisms. 相似文献
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Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden. 相似文献
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通过对稻秆原料进行常规特性分析和EDX元素含量分析,发现钾在稻秆无机元素中占有重要地位。参考原料化学分馏法和土壤中钾的分类与测试方法,给出了对生物质原料及其燃烧产物中钾的定性与定量简易方法。通过程序控温型固定床对稻秆先进行缓慢氧化,然后以100℃为间隔从400~900℃进行成灰,并分别测试其成灰率、有效钾和全钾的份额。结合稻秆原料及其灰中钾的份额分析,进行了稻秆灰中有效钾转化与释放的计算,发现有效钾在700~800℃之间有快速的释放和形态转变。稻秆灰的XRD分析结果表明秸秆灰中钾主要以KCl、K_2SO_4形式存在,得到了钾以盐的形式进行转化与释放的机理。该文中燃烧温度对钾转化与释放的影响规律对设计秸秆电厂时的炉型选择和燃烧参数确定有一定参考价值。 相似文献