纳米尺度下气体薄膜润滑理论研究

提出了依赖于逆Knudsen数的纳米尺度影响因子NP,修正了目前应用较为普遍的FK-Boltzmann模型,并给出了其数值计算结果.结果表明:当膜厚小于单个空气分子平均自由程时,由于纳米尺度效应的影响,流量因子有所减小,承载能力略微增加.

薄膜节流器动静混合径向气体轴承性能

对薄膜节流器动静混合径向气体轴承进行理论研究与数值仿真,建立薄膜节流器内气体流动模型并进行简化,采用流体阻抗法将薄膜节流器的流量表达式并与气体轴承小孔节流流量表达式联立,使用牛顿迭代法对非线性气体雷诺方程进行处理,采用有限差分法对上述方程进行离散化进而求解含有薄膜节流器小孔节流气体轴承的雷诺方程,得到薄膜节流器的气体流量分配规律,进而获得有转速和零转速下轴承承载力。数值仿真结果表明,节流器气腔高度和节流器出口直径是薄膜节流器设计的关键参数,气腔高度越小,节流器出口直径越小,承载能力越大;使用薄膜节流器后,各节流孔的入气压力均有所降低,但是各孔之间的入气压力差增大,进而显著提高气体轴承承载能力。

SnO_2基薄膜气体传感器制作与敏感性测试

在现有的粉末烧结型SnO2基气体传感器基础上研制了薄膜型SnO2基气体传感器,以抛光的耐热石英玻璃为基片,真空磁控溅射50～70nm厚度的SnO2薄膜,在SnO2薄膜上分别溅射不连续的ZnO、Al2O3、CeO2、InO2等薄膜,传感器背面溅射30μm的Ni80Cr20电阻合金作为传感器加热电阻,用薄膜热电偶测量传感器工作温度。测试了不同的复合膜对传感器灵敏度和选择性的影响,并对传感器的吸附与解吸速度进行了测试,薄膜传感器达到相同灵敏度所需的工作温度比粉末烧结型传感器下降100～150℃,吸附解吸速度比粉末烧结型快。

SnO2基薄膜气体传感器制作与敏感性测试

在现有的粉末烧结型SnO2基气敏传感器基础上研制了薄膜型SnO2基气体传感器，以抛光的丽热石英玻璃为基片，真空磁控溅射50～70nm厚度的SnO2薄膜，在SnO2薄膜上分别溅射不连续的ZnO、Al2O3、CeO2、InO2等薄膜，传感器背面溅射30μm的Ni80Cr20电阳合金作为传感器加热电阻，用薄膜热电偶测量传感器工作温度。测试了不同的复合瞑对传感器灵敏度和选择性的影响，并对传感器的吸附与解吸速度进行了测试，薄嗅传感器达到相同灵敏度所需的工作温度比粉末烧结型传感器下降100～150℃，吸附解吸速度比粉末烧结型快。

基于气体传感器阵列技术的中医电子鼻研究

基于第3代薄膜型气体传感器阵列技术的中医电子鼻(WES-ENO11103-A)是福建中医药大学客座教授吴青海自主研发的新型嗅诊仪。本文对电子鼻的基本组成和工作原理、医用电子鼻技术的发展概况、薄膜型气体传感器阵列技术的特点、自主研发的中医电子鼻简况及前期实验结果进行了介绍,以期为中医临床诊断提供无创、科学、简便、快捷的嗅诊仪器,推动中医诊断技术的发展。

金属催化剂对CO气敏薄膜特性影响的密度泛函法分析

根据密度泛函理论,采用总体能量平面波赝势方法,计算了CO气体敏感薄膜中几种常用金属催化剂(P T,PD,CU,A G)的能量最低晶面,并对CO在这些晶面上的吸附特性进行了研究.从结合能、C O键长、轨道布居、态密度等方面比较了C与金属成键强度及CO分子被活化程度.计算结果发现,CO在金属表面的吸附强度及金属对CO催化效果强弱的顺序是:P T>PD>CU>A G.得出结论:对于CO气体传感器,P T是通过金属催化剂添加提高灵敏度的最佳选择.

基于连续模型和离散模型的微尺度三维凸台轴承的气体润滑分析

为了考察应用图案化盘片实现超高密度磁存储时磁头/磁盘界面气体润滑设计理论的有效性,本文设计了1种三维凸台轴承构型,分别使用直接模拟蒙特卡罗方法(DSMC)和气体分子薄膜润滑理论(MGL)方法进行了模拟计算,考察了相对滑动速度、轴承最小间隙、凸台高度和入射速度方向对气体轴承压力分布的影响.结果表明:对于三维凸台微尺度气体轴承,MGL方法的计算结果依然与DSMC方法的结果相差不大.存在凸台接触,轴承间隙为零的情况下,气体轴承仍然具有一定的承载能力,且压力分布形状随凸台高度的变化表现出与常规非接触式气体轴承不同的规律.

ZnO Films Synthesized by Solid-Source Chemical Vapor Deposition with c-Axis Parallel to Substrate

ZnO films with c -axis parallel to the substrate are reported.ZnO films are synthesized by solid-source chemical vapor deposition,a novel CVD technique,using zinc acetate dihydrate (solid) as the source material.The properties are characterized by X-ray diffraction,atomic force microscopy and transmission spectra.The parallel oriented ZnO films with mixed orientation for (100) and (110) planes are achieved on glass at the substrate temperature of 200℃ and the source temperature of 280℃,and a qualitative explanation is given for the forming of the mixed orientation.AFM images show that the surface is somewhat rough for the parallel oriented ZnO films.The transmission spectrum exhibits a high transmittance of about 85% in the visible region and shows an optical band gap about 3.25eV at room temperature.

Development of CO2 Selective Poly（Ethylene Oxide）-Based Membranes： From Laboratory to Pilot Plant Scale

Membrane gas separation is one of the most promising technologies for the separation of carbon dioxide （CO2） from various gas streams. One application of this technology is the treatment of flue gases from combustion processes for the purpose of carbon capture and storage. For this application, poly（ethylene oxide）-containing block copolymers such as Pebax or PolyActiveTM polymer are well suited. The thin-film composite membrane that is considered in this overview employs PolyActiveTM polymer as a selective layer material. The membrane shows excellent CO2 permeances of up to 4 m^3（STP）.（m^2·h·bar）^-1 （1 bar = 105 Pa） at a carbon dioxide/nitrogen （CO2/N2） selectivity exceeding 55 at ambient temperature. The membrane can be manufactured reproducibly on a pilot scale and mounted into fiat-sheet membrane modules of different designs. The operating performance of these modules can be accurately predicted by specifically developed simulation tools, which employ single-gas permeation data as the only experimental input. The performance of membranes and modules was investigated in different pilot plant studies, in which flue gas and biogas were used as the feed gas streams. The investigated processes showed a stable separation performance, indicating the applicability of PolyActiveTM polymer as a membrane material for industrialscale gas processing.

A Mass Transfer Model Based on Individual Bubbles and an Unsteady State Film Mechanism

A gas-liquid mass transfer model based on an unsteady state film mechanism applied to a single bubble is presented. The mathematical model was solved using Laplace transform to obtain an analytical solution of concentration profile in terms of the radial position r and time t. The dynamic mass transfer flux was deduced and the influence of the bubble size was also determined. A mathematical method for deducing the average mass transfer flux directly from the Laplace transformed concentration is presented. Its accuracy is verified by comparing the numerical results with those from the indirect method. The influences of the model parameters, namely, the bubble size R, liquid film thickness δ, and the surface renewal constant s on the average mass transfer flux were investigated. The proposed model is useful for a better understanding of the mass transfer mechanism and an optimum design of gas-liquid contact equipment.

Numerical simulation of 3D viscous flow field of air cooled turbine blades with coolant mixing

To improve thrust and reduce oil consumption of aero-engines, the temperature at turbine inlet is becoming higher and higher, which leads to heavy thermal load of vanes. To efficiently cool the vanes, the mass of coolant with its maximum gas mass flow exceeding to 20% of main stream, has to be increased. In the pres- ent paper, a two-stage turbine with and without coolant mixing was simulated by CFX-TASCflow. Simulation resuits indicate that the flow field structure with coolant is obviously different from that without coolant, and the former has characteristics of lower-speed main flow, reduced mach number, weaker shock intensity and decreased stage efficiency.

Structure and Oxygen Sensing Properties of TiO_2 Porous Semiconductor Thin Films

Semiconductor-type TiO2 oxygen sensing thin films were synthesized using tetrabutyl titanate （Ti （OBu）4） as precursor and diethanolamine （DEA） as complexing agent by the sol-get process. The porous and oxygen sensing TiO2 films were obtained by the addition of polyethylene glycol （PEG）. The micrographs of scanning electron microscope （SEM） show that the pores of the sample about 400-600 nm in size with PEG（2 000 g/mol） are larger than those about 300 nm in size with PEG（ 1 000 g/mol）, while the density of pores is lower. The results also indicate that increasing the content of PEG properly is beneficial to the formation of porous structure. With the increasing content of PEG from 0 g to 2.5 g, the oxygen sensitivity increases from 330 to more than 1 000 at 800 ℃, from 170 to more than 1 000 at 900℃, and the response time to O2 and H2 are about 1.5 s and less than 1s, respectively.

Role of CuO-ZnO Heterojunctions in Gas Sensing Response of CuO-ZnO Thick Films

The CuO-doped ZnO thick films were prepared by the screen printing technique. The CuO doped ZnO composite materials were obtained by mixing AR grade （99.9% pure） Zinc Oxide powder mechanochemically in acetone medium with various weight percentages of Copper Chloride （CulCI2.2H20） powder （1, 3, 5, 7 and 9wt.%）. The prepared materials were sintered at 1,000 ℃ for 12 h in air ambience and ball milled to ensure sufficiently fine particle size. The films were characterized by different techniques with respect to their surface morphology and compositional property by means of SEM （scanning electron microscope） and EDXA （energy dispersive x-ray analysis）. The surface morphology of the films was studied by SEM and it shows the films are porous in nature and petal-shaped grains of sizes varies from 220 nm to 250 nm were observed. The final composition of each film was determined by the EDXA analysis. The gas response of undoped ZnO and CuO doped ZnO films was studied for different gases such as CO, C12, NH3, Ethanol, H2S and LPG at operating temperature ranging from 50 ℃ to 400 ℃. The 7wt.% CuO-doped ZnO film shows good response to H2S gas （100 ppm） at 250 ℃.

Study of Plasma and Ion Beam Sputtering Processes

The effects of plasma （ions, electrons） and other energetic particles are now widely used for substrate cleaning as well as to assist and control thin film growth and various applications. In this work, historical review of the plasma and its various types are given and described. Different types of gas discharge and plasma production are also discussed in detail. Furthermore, technique of ion beam extraction from a plasma source for sputtering process by using a suitable electrode is carefully studied and given. In further consequence, a general review about the physics and mechanism of sputtering processes is studied. Different types of sputtering techniques are investigated and clarified. Theoretical treatment for determination of sputtering yield for low and high atomic species elements as a function of energy from 100 to 5,000 eV are studied and discussed. Finally, various applications of plasma-and-ion beam sputtering will also be mentioned and discussed.

Dependence of Optical Absorption in Silicon Nanostructures on Size of Silicon Nanoparticles

The amorphous silicon nanoparticles （Si NPs） embedded in silicon nitride （SiNx） films prepared by helicon wave plasma-enhanced chemical vapor deposition （HWP-CVD） technique are studied. From Raman scattering investigation, we determine that the deposited film has the structure of silicon nanocrystals embedded in silicon nitride （nc-Si/SiNx） thin film at a certain hydrogen dilution amount. The analysis of optical absorption spectra implies that the Si NPs is affected by quantum size effects and has the nature of an indirect-band-gap semiconductor. Further, considering the effects of the mean Si NP size and their dispersion on oscillator strength, and quantum-confinement, we obtain an analytical expression for the spectral absorbance of ensemble samples. Gaussian as well as lognormal size-distributions of the Si NPs are considered for optical absorption coefficient calculations. The influence of the particle size-distribution on the optical absorption spectra was systematically studied. We present the fitting of the optical absorption experimental data with our model and discuss the results.

杉杉推出纳米西服

在日前开幕的CHIC男装展会上,杉杉集团的展位吸引了众多的目光。最被人们津津乐道是该集团今年首推的纳米西服。 据了解,纳米西服是杉杉西服有限公司全面引进中科院二元协同纳米界面双疏处理技术所开发出的中高端时尚西服。据专家介绍,通过这种新技术处理,服装面料及成衣表面将形成类似气体薄膜的保护层,

The effect of working gas pressure and deposition power on the properties of molybdenum films deposited by DC magnetron sputtering

Molybdenum films were deposited on Corning 7059 glass substrates by DC magnetron sputtering with different working gas pressures and sputtering powers.The structure and morphology,residual stress and adhesion,resistivity and optical reflectance of the as-deposited Mo films were investigated.The results show that Mo films deposited with high working gas pressure and low sputtering power have a spherical surface morphology,small grain size,residual compressive stress and a good adhesion,high resistivity and low optical reflectance.With the working gas pressure decreased and the sputtering power increased,Mo films have elongated spindle-shape or diamond flake shape surface morphology,the grain size is increased,with residual stress changed from tensile to compressive,a poor adhesion,resistivity decreased and optical reflectance increased.

The fabrication and optimization of OTFT formaldehyde sensors based on Poly(3-hexythiophene)/ZnO composite films

Formaldehyde(HCHO),a colorless and pungent-smelling gas,is confirmed be a huge threat to human health.The detection of formaldehyde is necessary and important.The Poly(3-hexythiophene)(P3HT)/ZnO organic-inorganic composite thin film was fabricated and used as the sensitive layer of organic thin film transistors(OTFT) by spray-deposited method to detect HCHO at room temperature.The process parameters such as P3HT/ZnO weight ratios and airbrushed masses were optimized.The results showed that P3HT/ZnO OTFT exhibited good sensing response to HCHO.Airbrushed mass of 1ml was the optimal mass,and the 1:1 and 1:5 weight ratios of P3HT/ZnO exhibited better sensing properties compared with others.OTFT gas sensors based on P3HT/ZnO composite film provides a novel promising approach to the detection of HCHO.

Hydrogen bonding in hydrogenated amorphous silicon thin films prepared at different precursor gas temperatures with undiluted silane

Hydrogen bonding configurations and hydrogen content in hydrogenated amorphous silicon (a-Si:H) thin films prepared at different precursor gas temperatures with undiluted silane have been investigated by means of Fourier transform infrared (FTIR) spectroscopy.The results show that the gas temperature before precursor gases entering the glow-discharge zone re-markably influences the hydrogen bonding configurations and the hydrogen content in a-Si:H thin films.The hydrogen content decreases from 18% down to 11% when increasing the gas temperature from room temperature (RT) to 433 K.Meanwhile,the clustered hydrogen at the physical film surface or at the internal surfaces of the microvoids decreases,indicating that a-Si:H thin films are densified at higher precursor gas temperatures.For a-Si:H thin films deposited at gas temperature of 433 K,the isolated silicon-hydrogen bonding configuration is predominant in the testing films.