溅射功率对PET基表面沉积纳米铜膜特性影响

室温条件下采用射频磁控溅射法在涤纶(PET)平纹机织物表面沉积纳米Cu薄膜,借助原子力显微镜(AFM)分析溅射功率的变化对铜膜表面形貌、粒径的影响;同时研究不同溅射功率条件下制备的沉积纳米铜织物透光性能、导电性能及界面结合性能。实验结果表明,随着溅射功率增加,纳米铜膜颗粒大小、表面粗糙度随之减小,铜膜的均匀性、致密性先提高后下降;经Cu镀层处理的涤纶平纹织物对紫外光和可见光透射率明显低于原样,溅射功率提高能使样品屏蔽紫外线和可见光效果变好,但功率提高到120W后,屏蔽效果增加不明显;铜膜方阻随溅射功率提高而减小,导电性能增强,而铜膜与基材的剥离强力先增加后减少。     

直流溅射工艺参数对Mo薄膜结构及电性能的影响

采用直流磁控溅射法在SLG衬底上沉积Mo薄膜,对不同溅射功率和溅射工作气压下沉积的薄膜进行X射线衍射、SEM(扫描电子显微镜)、电阻率测试,讨论了工艺参数对沉积Mo薄膜相结构、表面微观形貌、薄膜沉积速率和电学性能的影响。结果表明,随着溅射功率的增加,薄膜的结晶性能变好,沉积速率提高,在沉积功率范围内薄膜均匀致密,表面无空隙,电阻率较低;随着溅射工作气压增加,薄膜结晶性能变差,沉积速率先增加后降低,在沉积工作气压范围内,薄膜致密;随气压降低,电阻率急剧减小。因此,较高的溅射功率和较低的工作气压沉积的Mo薄膜更适合作CIGS薄膜太阳电池的BC层(背接触层)。     

等离子体预处理对镀铜涤纶针刺毡性能的影响

采用射频磁控溅射技术在PET针刺毡表面沉积了纳米结构Cu薄膜,试图利用等离子体预处理的方法来改善薄膜与基材之间的结合牢度。采用扫描电子显微镜(SEM)对低温等离子体预处理前后基材表面形貌的变化进行了分析,同时利用静态液滴形状观察法和接触角测试分析了等离子体处理前后样品的润湿性能。采用X射线能谱仪(EDX)对纳米结构Cu薄膜进行了元素分布及定量分析。结合抗静电性能测试,采用冷热循环试验研究了Ar和O2等离子体预处理对Cu薄膜结合牢度的影响。研究发现,低温等离子体预处理不仅能改善沉积Cu薄膜PET针刺毡的抗静电性能,还能提高膜-基结合牢度和基材的润湿性能。用O2等离子体处理时,膜-基结合牢度和润湿性能较好。     

射频磁控溅射对PET基材制备铝薄膜的性能影响

针对传统制铝技术,为提高膜层结合力、阻隔性,采用射频磁控溅射镀铝工艺,制备纯铝高阻隔性膜层,在PET塑料薄膜表面沉积纯铝的实验.通过对射频电源功率和溅射气压等参数的改变,探究射频功率、溅射气压对薄膜结合力、阻隔性的影响.结果表明:薄膜沉积过程中的射频功率和溅射气压对磁控镀铝薄膜性能影响较大,在一定的溅射压力下,膜层的结...     

磁控溅射铜薄膜微观结构对其电爆性能的影响

采用直流磁控溅射法在不同溅射功率和工作气压条件下沉积Cu薄膜,对其进行X射线衍射、原子力显微镜、电阻率测试,分析了工艺参数对Cu薄膜的沉积速率、微观结构和电阻率的影响。通过紫外光刻技术将Cu薄膜制成桥箔,采用电爆测试平台获得Cu桥箔的电爆参数,研究了Cu薄膜的晶粒尺寸、择优取向对其电爆性能的影响。结果表明:随溅射功率的增大,Cu薄膜的沉积速率增加、晶粒尺寸增大、Cu(111)晶面择优取向特性变差,且电阻率降低;随溅射工作气压增大,Cu薄膜的沉积速率降低、晶粒尺寸减小、Cu(111)晶面择优取向越明显,且电阻率增加。对于相同桥区参数的Cu桥箔,晶粒尺寸越小,其爆发时刻就越早;Cu(111)晶面择优取向越明显,其爆发电流和峰值功率就会越大。     

直流磁控溅射制备铝薄膜的工艺研究

采用直流磁控溅射方法，以高纯Al为靶材，高纯Ar为溅射气体，在玻璃衬底上成功地制备了铝薄膜，并对铝膜的沉积速率、结构和表面形貌进行了研究。结果表明：A1膜的沉积速率随着溅射功率的增大先几乎呈线性增大而后缓慢增大；随着溅射气压的增加，沉积速率先增大，在一定气压时达到峰值后继续随气压的增大而减小。X射线衍射图谱表明Al膜结构为多晶态；用扫描电子显微镜对薄膜进行表面形貌的观察，溅射功率为2600W，溅射气压为0．4Pa时制备的Al膜较均匀致密。     

沉积铜薄膜涤纶针刺过滤毡抗静电性能研究

在室温条件下,采用射频磁控溅射法在涤纶(PET)针刺过滤毡表面制备了纳米结构铜薄膜。通过正交试验分析了溅射主要工艺参数(工作气压、溅射功率和沉积时间)对PET滤料抗静电性能的影响,并以优化溅射工艺所制备抗静电过滤毡与纱线型涤纶防静电针刺过滤毡和混纺型涤纶防静电针刺过滤毡进行了性能比较。研究表明,经镀膜后PET过滤毡的抗静电性能得到了显著改善,并且抗静电性能明显优于纱线型和混纺型的抗静电过滤毡。通过对过滤性能的测试发现,沉积铜薄膜几乎不影响PET滤料的原有过滤性能。     

不同溅射功率下PEN/Ti纳米复合薄膜的制备及性能研究

采用直流磁控溅射法,在溅射气压为7.0×10~(-1) Pa和不同溅射功率(72～144W)下,制备出PEN/Ti纳米复合薄膜。研究了不同溅射功率对Ti膜微观组织、表面粗糙度、硬度及生长方式的影响规律。结果表明,直流磁控溅射法在PEN柔性衬底上沉积的钛膜是一种纳米多晶薄膜;随着溅射功率的增加,钛膜沉积速率及钛膜弹性模量皆升高,而钛膜表面粗糙度与钛膜晶粒尺寸均减小;溅射功率的增加将抑制钛膜柱状生长方式。在溅射气压为7.0×10~(-1) Pa,溅射功率为144 W时的工艺参数下,获得性能最佳的复合薄膜。     

磁控溅射法在涤纶织物上制备氟碳薄膜

用磁控溅射法在涤纶(PET)织物上制备纳米氟碳薄膜,研究了磁控溅射过程中不同PET织物布样、溅射功率、工作气压和基底温度对薄膜性能的影响。对氟碳膜的成膜组分进行了研究,并对溅射后的织物进行了拒水性能和抗紫外性能的测试和分析。     

磁控溅射工艺参数对涤纶织物表面沉积铜膜性能的影响

在室温条件下采用射频磁控溅射法在涤纶平纹机织物表面沉积纳米Cu薄膜,借助原子力显微镜(AFM)观察镀膜前后样品表面变化。通过分别改变镀膜时间、溅射功率和气体压强,研究其对样品透光性和导电性的影响。实验结果表明,经Cu镀层处理的涤纶平纹织物对紫外光和可见光的吸收能力明显优于原样。溅射压强增加,透光性能增强,铜膜方块电阻增加,导电性能减弱;镀膜时间延长和溅射功率增加,样品透射率降低,屏蔽紫外线和可见光效果明显,在溅射时间接近15min和溅射功率增加到120W后,样品屏蔽效果不明显,铜膜方块电阻随溅射功率增加而减小,导电性能增强。     

Real gas choked flow conditions at low reduced-temperatures

Real gas choked mass flux is calculated for a frictionless stream expanding isentropically until it reaches the speed of sound and without phase changes. The other parameters associated with the choked state are the pressure, density, temperature ratios, and the speed of sound. Departure of the choked mass flux from the ideal gas model is discussed first in absolute terms and then in relative terms, using the Principle of Corresponding States, for gases with boiling points in the low temperature range. Reduced-stagnation pressures are examined up to values of 30 for hydrogen, neon, nitrogen, argon, methane, krypton, xenon, and R-14 and up to 100 for ⁴He. The corresponding reduced-stagnation temperatures go down to 1.4 and in some cases down to 1.2 for nitrogen and argon. Also discussed are the limiting values of stagnation parameters for which no phase change occurs in the choked state. Compared to the ideal gas, the mass flux may almost double and the critical pressure ratio may decrease by an order of magnitude. The relevance of results is discussed qualitatively and quantitatively for Joule-Thomson cryocooling.     

As-cast microstructures and behavior at high temperature of chromium-rich cobalt-based alloys containing hafnium carbides

Hafnium is often used to improve the high temperature oxidation resistance of superalloys but not to form carbides for strengthen them against creep. In this work hafnium was added in cobalt-based alloys for verifying that HfC can be obtained in cobalt-based alloys and for characterizing their behavior at a very temperature. Three Co–25Cr–0.25 and 0.50C alloys containing 3.7 and 7.4 Hf to promote HfC carbides, and four Co–25Cr– 0 to 1C alloys for comparison (all contents in wt.%), were cast and exposed at 1200 °C for 50 h in synthetic air. The HfC carbides formed instead chromium carbides during solidification, in eutectic with matrix and as dispersed compact particles. During the stage at 1200 °C the HfC carbides did not significantly evolve, even near the oxidation front despite oxidation early become very fast and generalized. At the same time the chromium carbides present in the Co–Cr–C alloys totally disappeared in the same conditions. Such HfC-alloys potentially bring efficient and sustainable mechanical strengthening at high temperature, but their hot oxidation resistance must be significantly improved.     

Chitosan-collagen/organomontmorillonite scaffold for bone tissue engineering

A novel composite scaffold based on chitosan-collagen/organomontmo-rillonite (CS-COL/OMMT) was prepared to improve swelling ratio, biodegradation ratio, biomineralization and mechanical properties for use in tissue engineering applications. In order to expend the basal spacing, montmorillonite (MMT) was modified with sodium dodecyl sulfate (SDS) and was characterized by XRD, TGA and FTIR. The results indicated that the anionic surfactants entered into interlayer of MMT and the basal spacing of MMT was expanded to 3.85 nm. The prepared composite scaffolds were characterized by FTIR, XRD and SEM. The swelling ratio, biodegradation ratio and mechanical properties of composite scaffolds were also studied. The results demonstrated that the scaffold decreased swelling ratio, degradation ratio and improved mechanical and biomineralization properties because of OMMT.     

Capacitance based mass metering for cryogenic fluids

This paper describes a method for measuring the mass of cryogenic fluids in on-board rocket propellant tanks or ground storage tanks. Linear approximations to the Clausius-Mossotti relationship serve as the foundation for a capacitance based mass sensor, regardless of fluid density stratification or tank shape. Sensor design considerations are presented along with the experimental results for a capacitance based mass gage tested in liquid nitrogen. This test data is shown to be consistent with theory resulting in a demonstrated mass measurement accuracy of ±0.75% and a deviation from linearity of less than ±0.30% of full scale mass. Theoretical accuracies are also shown to be ±0.73% for hydrogen and ±1.39% for oxygen for a select range of pressures and temperatures.     

Equipment using a “static-analytic” method for solubility measurements in potentially hazardous binary mixtures under cryogenic temperatures

A new apparatus designed to study, at cryogenic temperatures, thermodynamic equilibria of potentially explosive binary systems such as hydrocarbon-oxygen mixtures is described herein. This equipment has an equilibrium cell which was especially designed to minimize hazards while allowing accurate phase equilibrium measurements. Reliability of results, obtained with this equipment has been verified by working on the nitrogen-propane system, for which data are already available in literature, over a large range of compositions and at various temperatures. Four isothermal curves describing liquid phase compositions at 109.98, 113.77, 119.75 and 125.63 K have been determined. Our experimental data are represented within 2% in compositions and in pressures through the Peng-Robinson equation of state implying Mathias-Copeman alpha function and Huron-Vidal mixing rule. Comparisons to literature allow pointing out: good agreement is observed with Kremer and Knapp data (1983) while the three sets of Poon and Lu data (1974) presenting systematic positive deviation are consequently judged as suspicious.     

Gas gap thermal switches using neon or hydrogen and sorption pump

The very low pressure obtained thanks to adsorption phenomenon at low temperature can be used to build cryogenic heat switches, which offer the possibility to make or break thermal contact between two parts of a cryogenic system. The ON (conducting) and OFF (insulating) states of the switch are obtained by varying the gas pressure between two copper blocks separated by a gap of 100 μm. This pressure is controlled by acting upon the temperature of a small sorption pump (activated charcoal) connected to the gap space. For a “high” sorption pump temperature, the gas previously adsorbed in the sorption pump is released to the gap between the two blocks, allowing a good thermal conduction through the gas (ON state). On the opposite, cooling the sorption pump allows a very good vacuum between the copper blocks, which efficiently break the thermal contact (OFF state). Experimental thermal characteristics (Conductance in the ON and OFF state, ON-OFF switching temperature) of such a “Gas Gap Heat Switch” are described using hydrogen or neon as exchange gas and are compared with theoretical calculations.     

Development of No-Vent™ liquid hydrogen storage system for space applications

A number of technological advances required to store and maintain normal-boiling-point and densified cryogenic liquids, including liquid hydrogen, under zero boil-off conditions in-space, for long periods of time, have been developed. These technologies include (1) thermally optimized compact cryogen storage systems that reduce environmental heat leak to the lowest-temperature cryogen, which minimizes cryocooler size and input power, and (2) actively-cooled shields that surround the storage systems and intercept heat leak. The processes and tools used to develop these technologies are discussed. A zero boil-off liquid hydrogen storage system technology demonstrator for validating the actively-cooled shield technology is presented.     

Development of a miniature cryogenic fluid circuit and a cryogenic micropump

This article presents the development of a miniaturized cryogenic fluid circuit for distributed cooling of low-temperature tracking detectors in high-energy physics (HEP). The heart of the circuit is a prototype cryogenic micropump. This volumetric pump is compatible with cooling powers of about 10-100 W, and capable of producing pressure heads of up to around 0.3 MPa. Besides detector and electronics cooling in HEP, potential applications are found in the field of superconductor technology.     

Integrated Resonant Self-Pumped Loop and pulse tube cryocooler for cryogenic cooling distribution

Cooling distribution is a vital technology concerning cryogenic thermal management systems for many future space applications, such as in-space, zero boil-off, long-term propellant storage, cooling infrared sensors at multiple locations or at a distance from the cryocooler, and focal-plane arrays in telescopes. These applications require a cooling distribution technology that is able to efficiently and reliably deliver cooling power (generated by a cryocooler) to remote locations and uniformly distribute it over a large-surface area. On-going efforts by others under this technology development area have not shown any promising results.This paper introduces the concept of using a Resonant Self-Pumped Loop (RSPL) integrated with the proven, highly efficient pulse tube cryocooler. The RSPL and pulse tube cryocooler combination generates cooling power and provides a distributive cooling loop that can be extended long distances, has no moving parts, and is driven by a single linear compressor. The RSPL is fully coupled with the oscillating flow of the pulse tube working fluid and utilizes gas diodes to convert the oscillating flow to one-directional (DC) steady flow that circulates through the cooling loop. The proposed RSPL is extremely simple, lightweight, reliable, and flexible for packaging. There are several requirements for the RSPL to operate efficiently. These requirements will be presented in this paper. Compared to other distributive cooling technologies currently under development, the RSPL technology is unique.     

Helium liquefaction with a commercial 4 K Gifford-McMahon cryocooler

This paper describes helium liquefaction using a commercial cryocooler with 1.5 W cooling power at 4.2 K (Sumitomo model RDK415D with compressor CSW-71D, consuming 6.5 kW electrical power), equipped with heat exchangers for precooling the incoming gas. No additional cooling power of cryoliquids or additional Joule-Thomson stages were utilized. Measurements of the pressure dependence of the liquefaction rate were performed. A maximum value of 83.9 g/h was obtained for 2.25 bar stabilized input pressure. Including the time needed to cool the liquefied helium to 4.2 K at 1 bar after filling the bottle connected to the cold head, and correcting for heat screen influences, this results in a net liquefaction rate of 67.7 g/h. Maintaining a pressure close to 1 bar above the bath during liquefaction, a rate of 55.7 g/h was obtained. The simple design enables many applications of the apparatus.