Dynamic surface tension measurements on a molten metal-oxygen system: The behaviour of the temperature coefficient of the surface tension of molten tin

In order to point out the interactions of oxygen with a liquid metal and to study the influence of the actual operating conditions, dynamic surface tension measurements of a liquid test metal (tin), were performed under vacuum conditions by using the large drop method. This classical method has been improved by applying a new experimental procedure which allowed to obtain reliable surface tension measurements at high temperature as a function of time and varying the oxygen content. Further, complementary information on molten metal-oxygen interactions can be obtained. In particular, in this work, the trend of the surface tension temperature coefficient has been analysed as a function of different operative parameters, highlighting some crucial points such as the dependence of the temperature coefficient on the accuracy of the surface tension experimental data and the influence of the dissolved oxygen. It was demonstrated that the surface tension and its temperature coefficient do not depend on the quantity of dissolved oxygen when this is inside a certain range of values.     

溅射时氧分压对LaNiO3-x薄膜性能的影响

在较低的衬底温度(260 0C)和不同氧分压下,采用射频溅射在(111)Si衬底上制备出了具有(100)择优取向的 LaNiO3薄膜. SEM分析表明薄膜具有光滑连续的表面和均匀的晶粒尺寸. I-V特性表明薄膜均具有金属导电性,且随着氧分压的增加,电阻率逐步降低并达到一个稳定值 10Ω@μ m.实验结果同时表明,随着氧含量的增加,Ni、 La含量比单调增大,并且当溅射气氛中的氧气分压在 20%～30%范围时,Ni、 La含量比为 1:1而且比较稳定.当氧气分压为30%时,薄膜的晶面间距达到最小值.制备 LaNiO3薄膜的最佳氧气分压应该控制在 30%左右.     

表面张力温度系数对硅单晶生长的影响

利用有限元方法对硅单晶Czochralski(Cz)法生长炉内的流动和传输过程进行了全局数值模拟,研究了表面张力温度系数对硅单晶生长过程的影响,模拟的表面张力温度系数范围是(0～0.35)×10-3N/m·K.结果表明:随着表面张力温度系数的增加,由Marangoni效应驱动的熔体表面流动能强化熔体的自然对流,从而减小了通过熔体自由界面的温差,降低了加热器的功率.但是,结晶界面更凸向熔体,在结晶界面处晶体内的轴向温度梯度减小;对常规Cz炉,结晶界面处的平均氧浓度先减小然后增大,而对于具有气体导板的Cz炉,Marangoni效应总是使结晶界面处的平均氧浓度减小.     

Oxygen partial pressure dependence of the properties of MgZnO thin films during annealing

Undoped n-type MgZnO films were deposited on c-plane sapphire substrates by molecular-beam epitaxy and subsequently annealed in O₂ at different pressures. After annealing at 3.03 × 10⁵ Pa, oxygen content in the annealed films show increases and the films transform into p-type conduction. However, the decreases of oxygen content and the increases of electron concentration were obtained while the films annealed at 1.01 × 10⁵ Pa or 2.05 × 10⁻³ Pa. The changes in intensity of the emission peak located at 2.270 eV are similar to the changes of the oxygen content in the films annealed at different pressures. According to the defect levels and the relationship between photoluminescence spectra and annealing condition, it was suggested that this emission peak was related to interstitial oxygen (O_i). The obtained p-type conduction is attributed to that the O_i acceptor can compensate oxygen vacancy and interstitial zinc donor.     

Surface tension of pure liquid bismuth and its temperature dependence: Theoretical calculations

A theoretical method for calculating the surface tension of liquid metals as a function of temperature is proposed. A mathematical equation, based on statistical thermodynamics, is applied to calculate the surface tension of pure liquid bismuth, in the temperature range 545-620 K. The calculated surface tension of liquid bismuth was found to be 388 mJ/m², which is in excellent agreement with the reported experimental values (374-417 mJ/m²). The surface tension of bismuth decreases linearly with temperature, confirming a negative slope.     

Analytic dependence of density of liquid oxygen on temperature and pressure

On the basis of experimental data on the density of liquid oxygen, an approximate analytical relation is obtained for the range of temperatures 153°-83° K and pressures (78.5–196)·10⁵ N/m².Notation density, g/cm³ - p pressure, N/m² - T temperature, ° K     

变压吸附空分制氧过程非等温模拟

建立了变压吸附空分制氧过程非线性、非等温模型,并进行了数值模拟,计算结果与实测值吻合较好.在此基础上探讨了变压吸附过程中床层内温度和体积分数的动态行为,考察了吸附时间、吸附床高度、进气流速、清洗比等工艺参数对过程性能的影响.结果显示,对于本研究中的小型变压吸附装置,吸附热对产品气的影响不太大.     

Oxygen pressure and measurement temperature dependence of defects related bands in zinc oxide films

The ZnO films were fabricated by pulsed laser deposition at various oxygen pressure on single crystal silicon substrate. The structural and optical properties were investigated at various measurement temperature. The results showed that all the films have good c-axis preferred orientation. The different defects in films were fabricated which can be caused by various oxygen pressure. The films deposited at 1 Pa oxygen pressure have the most intense and narrow UV emission, and did not exhibit the deep band emission at the various measurement temperature. With the decrease of measurement temperature, the V_O-, O_i- and O_Zn-related band energy decreases, which is opposed to the V_Zn-related defects, meanwhile, the intensity of O_i-related emission peak has a sharp increase.     

Deformation of carbon nanotubes colliding with a silicon surface and its dependence on temperature

Using molecular dynamics simulation, we investigated the carbon nanotubes (CNTs) colliding with a silicon surface at a speed of 600 m/s, mimicking cold spray experiments of CNTs. Depending on temperature (300-900 K), the CNT is deposited on or bounces off the surface after impact on the surface. The CNT was more deformed as its temperature rose. The deformation of CNT was maximal for the collision geometry where the long axis of CNT lies parallel to the surface plane. However, its vibrational energy was maximal when the CNT collided with its long axis perpendicular to the surface.     

Oxygen partial pressure dependence of the structural properties of CdO thin films deposited by a modified reactive vacuum evaporation process

Thin films of cadmium oxide were thermally deposited on glass substrates at partial pressures of oxygen, pO₂ in the range 1.33×10⁻² to 0.133 Pa at a substrate temperature of 160 °C. Energy dispersive analysis of X-ray fluorescence (EDAX) revealed that the CdO films deposited at pO₂ value of 4.00×10⁻² Pa were nearly stoichiometric. X-ray diffractometry (XRD) confirmed the polycrystalline nature of the film structure. All the films showed an fcc structure of the NaCl-type, as the dominant phase. The films exhibited preferred orientation along the (1 1 1) diffraction plane. The texture coefficients calculated for the various planes at different oxygen partial pressures (pO₂) indicated that the maximum preferred orientation of the films occurred along the (1 1 1) plane at an oxygen partial pressure of 4.00×10⁻² Pa. This was interpreted in terms of oxygen chemisorption and desorption processes. The lattice parameters determined from the diffraction peaks were in the range 4.655–4.686 Å. The average lattice parameter a₀ found by extrapolation using the Nelson–Riley function was 4.696 Å. Both the lattice parameter and the crystallite size were found to increase with increased partial pressure of oxygen. On the other hand, the strain and dislocation density were found to decrease as the partial pressure of oxygen was raised. A maximum (80%) in the optical transmittance at λ=600 nm and minimum in the electrical resistivity (9.1×10⁻⁴ Ω cm) of the films occurred at an optimum partial pressure of oxygen of 4.00×10⁻² Pa. The results are discussed.     

Temperature dependence of the surface tension for binary mixtures ofn-butanenitrile +n-alkanes

The differential capillary-rise method was used to determine the orthobaric surface tension of binary liquid mixtures ofn-butanenitrile mixed withn-pentane,n-hexane, andn-heptane, throughout the composition range. at 293.15, 303.15, 313.15, 323.15, 333.15. and 343.15 K. Furthermore, the system withn-hexane was also studied al 263.15 K. i.e., 19 K above its upper critical solution temperature, over the whole composition range. For each binary system the surface tension changes regularly with both temperature and composition between the values of the pure components. The results are discussed in terms of deviations from surface ideality and related to the large positive deviations observed for bulk properties of the same systems.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Determination of the adsorption character of cellulose fibres using surface tension and surface charge

The reactivity and adsorption properties of cellulose fibres are critical for successful treatment because behavior during the finishing process is determined by both structure and surface properties. The fine structure of natural cellulose fibres i.e. cotton, is different from the regular viscose, modal and new types of regenerated cellulose fibres i.e. lyocell, which are clarified by different hydrophilic/hydrophobic character of fibres and different adsorption properties. Tensiometry, seldom used in fibre characterization was used to obtain the differences in the adsorption properties of different cellulose fibres. The surface tension, contact angle and adsorption were measured, and then compared with various methods for determining water adsorption. Currently some additional methods especially sensitive to surface properties (electrokinetic properties of fibres) are being applied in order to characterize the adsorption character and reactivity of the fibre surfaces. The streaming potential was measured due to the fact that the interaction properties are strongly influenced by electric charges on the surface, and from these values the zeta potential (ζ) was calculated as a function of the pH and the surfactant concentration in the liquid phase. As with the results of fibre reactivity and adsorption properties obtained by conventional methods, the electrokinetic character of the materials and their adsorption ability determined using the tensiometry also show the same phenomena. The natural fibres have the smaller hydrophilic character and they are less reactive than the regenerated ones, so the ζ_max of cotton is the highest and the contact angle ϕ the greatest [1, 2, 3] Electronic Publication     

基底温度和氧分压对直流磁控溅射制备的ZnO∶Al薄膜性能的影响

利用直流磁控溅射法在玻璃衬底上制备了ZnO:A l(ZAO)透明导电薄膜。详细研究了沉积时的基片温度、氧分压强对膜的透光率和电阻率的影响。结果表明:ZAO薄膜具有六角纤锌矿结构且呈c轴择优取向,晶粒垂直于衬底方向柱状生长;衬底温度和氧分压对薄膜的电阻率有很大影响;基底温度对薄膜的可见光透过率影响不大,但随氧分压的增大而增大;在衬底温度为250℃、氧分压为1%时,薄膜有最优化的电阻率和平均透光率,分别达到8.35×10-4Ω.cm和85.2%。     

氧分压对氧化镍薄膜表面形貌和光电性能的影响

采用射频溅射法在SnO2衬底上生长了NiOx薄膜,制备的薄膜是非理想化学计量的微晶薄膜.研究了氧分压对NiOx薄膜的溅射速率、表面形貌和光学电学特性的影响.研究结果显示,O2分压在1∶10时,可得到最快的沉积速率;低的氧分压沉积的薄膜表面比较疏松;随着氧含量的增加,方块电阻呈上升趋势,当氧分压达到一定值时,膜电阻又开始下降;随着氧分压的升高,颜色会逐渐加深,透射率降低.