太阳选择性吸收涂层系列讲座(14) 活性环境空心阴极溅射特性与沉积Al_2O_3、ZnO掺杂和In_2O_3:Mo薄膜的应用(下)

<正>2.4 ZnO掺杂透明导电氧化物沉积透明导电氧化物薄膜,例如SnO2、ITO、ZnO,有很多应用,如建筑玻璃、汽车、显示器、光伏器件。制备掺杂氧化锌膜用射频或脉冲直流溅射陶瓷靶,它含有ZnO和2%(重量比)Al2O3,无论如何靶的代价是过高的,而能用的功率密度是有限的。最近反应磁控溅射Zn:Al靶受到关注,虽然它需电压控制和氧分压强的闭环控制以保证工作在金属/氧化物过渡模式。     

Ga、Al共掺杂及单掺杂ZnO基透明导电薄膜的研究

采用溶胶-凝胶旋涂法制备出Ga、Al共掺杂和单掺杂Zn O基透明导电薄膜[Zn O∶(Ga,Al)(GAZO),Zn O∶Al(AZO)和Zn O∶Ga(GZO)],利用XRD、SEM、AFM、四探针电阻率测试仪和可见分光光度计测试技术,分析薄膜的结构、表面形貌和光电性能等。结果表明:薄膜表面光滑,呈六方纤锌矿结构,且沿C轴择优取向;与单掺杂薄膜相比,Ga、Al共掺杂可促进晶体生长,细化晶粒,并在一定范围内提高薄膜的透光率。与纯Zn O薄膜相比,共掺杂和单掺杂薄膜的电阻率均明显降低。     

H2流量对直流磁控溅射低温沉积ZnO:Al薄膜结构与性能的影响

在Ar和H2的混合气氛下采用直流磁控溅射在玻璃衬底上低温沉积Al掺杂ZnO,即ZnO∶Al透明导电薄膜,研究H2流量(0～10sccm)对薄膜结构、形貌、光学和电学性能的影响。结果表明:不同H2流量下制备的ZnO∶Al薄膜均为高度C轴取向的六角纤锌矿结构,溅射过程中通入适量的H2能改善ZnO∶Al薄膜的结晶质量和表面形貌;所有薄膜在400～900nm范围内的平均透过率均高于85%;随着H2流量的增大,薄膜的载流子浓度升高,电阻率减小,达到10-4Ω.cm数量级。     

退火气氛对Al-F共掺杂ZnO薄膜结构和光电性能的影响

用射频磁控溅射法制备了Al-F共掺杂ZnO（ZnO（Al,F））透明导电薄膜,研究了不同退火气氛对ZnO（Al,F）薄膜的结构、电学和光学特性的影响。结果表明:在真空和还原性气氛中退火后的薄膜透光率呈现"蓝移"趋势,在空气中退火处理后的薄膜透光率则表现为"红移";在真空中,400℃×60min的退火处理,使ZnO（Al,F）薄膜的电阻率降低至1.41×10^-3Ω·cm,透光率则上升到93%以上,有效提高了薄膜的光电特性;所有退火气氛下,薄膜均具有（002）单一择优取向的多晶六方纤锌矿结构;薄膜的晶粒尺寸为25～30nm。     

活性环境空心阴极溅射特性与沉积Al2O3、ZnO掺杂和In2O3：Mo薄膜的应用（下）

透明导电氧化物薄膜，例如SnO2、ITO、ZnO，有很多应用，如建筑玻璃、汽车、显示器、光伏器件。制备掺杂氧化锌膜用射频或脉冲直流溅射陶瓷靶，它含有ZnO和2％（重量比）Al2O3，无论如何靶的代价是过高的，而能用的功率密度是有限的。最近反应磁控溅射Zn：Al靶受到关注，虽然它需电压控制和氧分压强的闭环控制以保证工作在金属／氧化物过渡模式。     

ZnO:Al绒面透明导电薄膜的制备及分析

利用中频脉冲磁控溅射方法,采用Al掺杂(质量百分比2%)的Zn(纯度99.99%)金属材料为靶材制备平面透明导电ZnO:Al(ZAO)薄膜。利用湿法腐蚀方法,将平面ZAO薄膜在0.5%的稀盐酸中浸泡一定时间后,形成表面凹凸起伏的绒面结构。研究了平面ZAO薄膜的结构特性以及衬底温度、溅射功率和腐蚀时间对绒面ZAO薄膜表面形貌的影响,并对腐蚀前后薄膜的电阻变化进行了分析。结果表明:高温、低功率条件下制备的绒面ZAO薄膜表面形貌较好,在硅薄膜太阳电池中具有潜在的应用前景。     

薄膜厚度对ZnO:Ti透明导电薄膜光电性能的影响

利用直流磁控溅射法在室温水冷玻璃衬底上制备出可见光透过率高、电阻率低的掺钛氧化锌(ZnO∶Ti)透明导电薄膜。SEM和XRD研究结果表明,ZnO∶Ti薄膜为六角纤锌矿结构的多晶薄膜,且具有c轴择优取向。讨论了薄膜厚度对掺钛氧化锌透明导电薄膜光学、电学性能的影响。当薄膜厚度为835nm时,薄膜具有最低电阻率3.34×10-4Ω.cm。所制备薄膜附着性能良好,在波长为500～800nm的可见光中平均透过率均超过91%,ZnO∶Ti薄膜可用作薄膜太阳电池和液晶显示器的透明电极。     

磁控溅射有机聚合物衬底ZnO:Al透明导电膜的结构及光电性能研究

采用射频磁控溅射法在有机薄聚合物膜衬底上制备出铝掺杂的氧化锌 (ZnO :Al)透明导电膜 ,对薄膜的低温制备 (2 5～ 180℃ )、结构和光电特性进行了研究。制备薄膜为多晶膜 ,具有纯氧化锌的纤锌矿结构和 (0 0 2 )择优取向。制备薄膜在可见光区透过率达到 74 % ,最低电阻率为 8.5× 10 -4Ω·cm。     

低阻高透率ZnO透明导电薄膜

近年来透明ZnO导电薄膜的优良电性,低廉的制造成本以及简便的制备方法受到了重视。在热镜和多层光热转换系统中,它作为太阳电池的一部分,在取代ITO薄膜等方面具有诱人的应用前景。本文报道了用射频磁控溅射技术及低温处理制备得到的低电阻率和高透明度的ZnO薄膜。 以掺杂3wt％Al_2O_3的氧化锌陶瓷为靶材,用射频磁控溅射技术制备ZnO薄膜。溅射工艺条件见表1。     

直流磁控溅射有机衬底和玻璃衬底ZnO:Al薄膜结构特性

利用直流磁控溅射法在有机薄膜衬底和普通玻璃衬底上制备出了具有良好附着性的ZnO:Al薄膜,并分析了氧分压、溅射压强、沉积时间、温度对薄膜结构特性的影响.研究发现,铝掺杂的氧化锌薄膜是多晶膜,具有六角纤锌矿结构,ZnO:Al薄膜具有(002)择优取向.在同样的制备条件下,薄膜的晶化在普通玻璃上比在PET衬底上要好,但是在特定的条件下(沉积时间15min),在PET衬底上的要比普通玻璃衬底上的好.     

Preparation of CuInSe2 thin films with large grain by excimer laser ablation

Thin films of CuInSez (CIS) were prepared by XeCl excimer laser ablation on glass substrates. The deposition was carried out at 550°C and the target-substrate distance was changed from 15 to 60 mm. From XRD and EPMA measurements, all films showed the single-phase and stoichiometric chalcopyrite structure, independent of the distance. The deposition rate was large with the small distance. The surface morphology and cross-sectional SEM images were observed. The electrical conductivity measurements gave p-type conduction, and the mobility was improved with the smaller distance.     

Measurement and simulation of wall-wetted fuel film thickness

In gasoline engines, the quality of fuel mixture preparation in the intake has a strong influence on the performance and exhaust emission. This paper deals with the basic research on the fuel mixture preparation process, and reports the experimental and numerical investigations on characteristics of the wall-wetted fuel film. In the experiments, iso-octane mixed with 3-pentanone was injected against a flat wall. The film thickness on the wall was measured by using laser induced fluorescence (LIF) technique. The film area was measured with CCD camera. Influences of the injection duration, the impingement distance, and the impingement angle on the film thickness, film length, and film area are discussed. In the numerical simulation, the commercial computational fluid dynamics (CFD) software FLUENT was used. The results show that, in the radial direction, the film thickness increases to a peak around the impingement center and then decreases eventually reaching zero at the external edge. Enlarging the injection duration could expand the film area and make the fuel film thicker. As the impingement distance gets farther, the fuel film becomes thinner, and the film area becomes smaller. Minishing the impingement angle could expand the area of the thick part of the fuel film and meanwhile make the maximum film thickness smaller.     

直喷汽油机附壁油膜特性试验研究

运用激光诱导荧光法(LIF)定量分析了缸内直喷汽油机单孔喷油器喷雾撞壁的二维油膜特性。研究发现:燃油在壁面上向油膜铺展的方向聚集,并在边缘形成较厚的油膜。高喷射压力有助于形成质量较小且厚度较薄的油膜,同时减小喷射脉宽能进一步降低燃油附壁率。增加撞壁距离能同时减小油膜质量和油膜面积,然而油膜的平均厚度并未减小,对油膜蒸发并没有明显的促进作用。将喷射角度从15°增加到45°能够显著减少油膜质量和平均厚度。     

Experimental investigations of a double‐decker jet impingement/film structure's cooling effectiveness

Experiments were carried out to investigate the cooling coefficient of a laminar double‐decker jet impingement/film structure. Blowing rate M, the ratio of the jet impingement distance to the diameter of the jet hole H/D, the ratio of the distance between the jet hole and film hole to the diameter of the jet hole P/D were changed to study the rules of local cooling coefficient varying with these parameters. All the results show that a higher cooling coefficient was achieved under larger blowing rate conditions. There exists a proper range of H/D and P/D, which can result in a maximum cooling coefficient. It is verified that when H/D=0.5 and P/D=4, the maximum cooling coefficient can be achieved. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(4): 232–239, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20199     

Long-Wave and Integral Boundary Layer Analysis of Falling Film Flow on Walls With Three-Dimensional Periodic Structures

Falling films exhibit very complex wavy patterns, which depend on the properties of the liquid, the Reynolds number, the wall inclination angle, and the distance from the film inlet. The film hydrodynamics governs the heat and mass transfer in the liquid films. Our vision is to control and enhance heat and mass transport by using walls with specific microscale topographies that influence the falling film flow, stability, and wavy pattern. In this work, long-wave theory and integral boundary layer approximation are used for modeling the falling film flow on walls with three-dimensional periodic microstructures. The wall topography is periodic both in the main flow direction and in the transverse direction. Examples of such microstructures are longitudinal grooves with sinusoidal path (or meandering grooves) and herringbone structures. The effects of the Reynolds number, the wall inclination angle, and the longitudinal and transverse periods of the structure on the shape of liquid–gas interface are investigated. It is shown that, as opposed to straight grooves in longitudinal direction, grooves with meandering paths may lead to significant interface deformations.     

非对称多孔喷油器撞壁喷雾特性的试验与模拟

采用高速阴影摄像技术对直喷汽油机非对称多孔喷油器进行了撞壁喷雾特性研究.分析了撞壁距离和撞壁角度对撞壁喷雾贯穿距和半径的影响.利用计算流体力学CFD(Computational Fluid Dynamics)技术研究了撞壁距离与撞壁角度对撞壁喷雾粒径SMD(Sauter Mean Diameter)、壁面油膜厚度以及壁面油膜面积的影响.结果表明,撞壁距离与撞壁角度对撞壁喷雾有着重要影响,在试验条件下较佳的撞壁距离大约为26.1,mm,即压缩/进气上止点前后60°CA左右,较合适的撞壁角度应该是75°左右.此外,喷雾离开喷嘴3,ms后,撞壁距离为26.1,mm时,撞壁喷雾粒径SMD平均较撞壁距离18.1,mm时大了约1,μm,而比撞壁距离47.1,mm时小了约14,μm;撞壁角度为75°时,撞壁喷雾粒径SMD平均较撞壁角度60°时小了约5,μm,而比撞壁角度90°时大了约1.6,μm.     

Electrolyte creepage in galvanic cells II. Transport mechanism at high pressures

A mechanism for electrolyte creep is presented, explaining the high pressure that the electrolyte film can generate in the sealing zone of an alkaline cell. Also, the drop formation at the film front in creep experiments is explained. We assume that alkali atoms, underpotential deposited from the continuous electrolyte film, diffuse a short distance along the metal surface and again react with air and humidity to form a drop of electrolyte. The velocity of the whole film movement depends on the equivalent conductivity of the alkali ions in the continuous electrolyte film.     

Spatial distribution of high-density microwave plasma for fast deposition of microcrystalline silicon film

The high-density microwave plasma utilizing a spokewise antenna was successfully applied to fast deposition of highly crystallized and photoconductive microcrystalline silicon (μc-Si:H) film at low temperatures. Among various deposition parameters, spatial distribution of ion energy (IDF) mainly determines film crystallinity. The best crystallinity was obtained at the axial distance, Z from the quartz glass plate, where the spread of mean ion energy is minimum. By optimizing the axial distance, Z and total pressure, highly crystallized and photoconductive μc-Si:H film could be fabricated with a high deposition rate of 47 Å/s at 50 mTorr in SiH₄ and Ar plasma.     

Effects of the layout of film holes near the vane leading edge on the endwall cooling and phantom cooling of the vane suction side surface

In the current research, effects of the layout of film holes near the first-stage vane leading edge on the endwall cooling and phantom cooling of the vane suction side surface were numerically studied. The computational results indicate that the case with a positive film-hole angle achieves a higher cooling effectiveness level on the endwall and vane suction side surface compared to the case with a corresponding negative film-hole angle. Furthermore, the location of the film hole has a significant influence on the cooling performance of the endwall and vane suction side surface. In addition, the case with a smaller distance from film holes to the vane stagnation also attains a slightly higher cooling effectiveness (phantom cooling effectiveness) on the vane suction side surface.     

Three-dimensional numerical investigation on wall film formation and evaporation in port fuel injection engines

ABSTRACT

Wall film formation and evaporation were studied on a flat wall inside a constant-volume vessel using a three-dimensional numerical method. The computation was based on the discrete phase model (DPM) of spray dispersion, a spray–wall interaction model coupled with an enhanced wall film evaporation sub-model, in which the operating conditions of cold wall are considered for port fuel injection (PFI) engines. The influence of impacting parameters including injection pressure, the impingement distance from the injector and the impinged wall, injection duration, impingement angle, and wall temperature was discussed.