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101.
Current high performance magnetic storage devices, i.e., hard disk drives, typically operate at elevated temperatures of nominally
45–60°C. As a consequence, understanding the thermal response of the materials used in the construction of the drive becomes
imperative. In this report, we focus on the thermal behavior of a common perfluoropolyether lubricant (ZDOL) used on the carbon-overcoated,
hard disk. In particular, we show that evaporative loss of this disk lubricant, as well as bonding of the lubricant to the
carbon-overcoated disk, can occur at the temperatures encountered in the hard-disk drive. Surface energy measurements show
that the interaction of the hydroxyl-terminated perfluoropolyether ZDOL occurs principally through the end-groups. On unannealed
disks, the interaction between this “mobile” lubricant and the carbon overcoat is characterized by hydrogen bonding with the
strength of these interactions being only slightly stronger than the intermolecular hydrogen bonding characteristic of bulk
ZDOL. Upon annealing at temperatures in the range of 60–150°C, the ZDOL lubricant becomes “bonded” to the disk. The surface
energy of the bonded lubricant is substantially lower than the mobile lubricant reflecting the increased interaction strength
that occurs as a result of bonding. Since the bonded state is the lower energy state, transitions from the mobile state to
the bonded state are thermodynamically favored. The kinetics of this bonding transition, as well as the kinetics of lubricant
evaporation were studied as a function of temperature. Using a model of two competing reaction channels, the activation energies
for both lubricant bonding and lubricant evaporation were determined to be 3.6 kcal/mole and 5.4 kcal/mole respectively. Ab
initio quantum chemical modelling was used to investigate possible interaction sites on the carbon surface. Both experiment
and theory indicate that interaction of the hydroxyl-terminated ZDOL to the carbon overcoat occurs via hydrogen bonding to
oxygenated species on the carbon overcoat, with a binding energy of 5–8 kcal/mole. An esterification reaction between the
hydroxyl end-groups of ZDOL with carboxyl groups on the carbon surface as a result of annealing is shown to be consistent
with the both the surface energy data and the kinetic data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
102.
《分离科学与技术》2012,47(7):1884-1895
Abstract Droplet size is a key factor in the treatment of oil‐in‐water (O/W) emulsions, because of its influence on emulsion properties. The addition of a coagulant salt generally causes emulsion destabilization, increasing the droplet size, and enhancing coalescence between oil droplets, which helps its further treatment. The influence of CaCl2 addition on droplet size distribution of a commercial O/W emulsion used in machining processes was studied in order to facilitate oil removal and to improve its further treatment by centrifugation, ultrafiltration (UF) and vacuum evaporation. The critical coagulation concentration (CCC) was observed at a CaCl2 concentration of 0.05 M. The quality of the final aqueous effluent, expressed as its chemical oxygen demand (COD) value, was compared for all treatments. The highest COD values were obtained for centrifugation, while the COD of the UF permeate was approximately constant for all UF trials. The best effluent quality was obtained by vacuum evaporation. A combination of these techniques should be appropriate for most industrial treatments of O/W emulsions, depending on the subsequent use of the resulting aqueous effluent. 相似文献
103.
Wei Zou Xiaozhou Cai Jianwen Li Xinyi Dai Haiquan Zhang Aijun Zhou Jingze Li Lijun Song Tomokazu Iyoda 《Surface & coatings technology》2012,206(22):4634-4638
Selective deposition of Ag onto nanostructured block copolymer film template of poly(ethylene oxide) and poly(methacrylate) with azobenzene mesogen (PEO-b-PMA(Az)) has been done by thermal evaporation technique. A hexagonally arranged pattern or ordered strip structure of the PEO nanocylinders dispersed in the PMA(Az) matrix appears on the pure copolymer film surface after thermal annealing at 140 °C or 110 °C, respectively. Atomic force microscopy confirms that the deposited Ag atoms prefer to wet PMA(Az) matrix domains on the film surface, and finally aggregate into discrete nanoparticles in both cases. An ordered porous metallic layer is created on the hexagonally patterned copolymer template surface due to the preferential interaction of Ag toward the PMA(Az) phase. Alternatively, ordered array of metallic chains is formed on the template featured with strip structure. While the nominal layer thickness of the deposited Ag is 50 nm, the ordered metallic nanostructure disappears, indicating the host copolymer template cannot guide the spatial distribution of the deposited metal any more. 相似文献
104.
在我国沿海海域,没有大量的气象浮标,但在岛屿或海边有大量的气象观测站,能否利用这些气象观测站获得的数据进行蒸发波导特性分析,值得深入研究.对比沿海岛屿实测数据与NCEP再分析数据,并将这两种数据输入NPS模型后发现蒸发波导高度的差异较大.但是对比气象浮标数据与NCEP数据,表明NCEP再分析数据用于蒸发波导统计分析是可信的,从而得出结论:沿海岛屿测量数据应用于蒸发波导统计特性研究的可信度较低.理论分析表明:成因是海陆交互作用的影响.但其气象参数的变化趋势与NCEP再分析数据的变化趋势比较一致,对于蒸发波导强弱和变化趋势的判定,仍有一定参考价值. 相似文献
105.
《Applied Thermal Engineering》2014,62(2):341-350
Microalgae, one of the important biofuel producers, have received considerable attention recently. Dewatering is one of the bottlenecks for its industrialization due to the dilute nature of the suspensions and the small cell size. Traditional liquid–solid separation processes are not efficient for dewatering of microalgae suspensions. In this study, falling film evaporation was employed for dewatering of microalgae suspension, which is a popular process for concentrating heat sensitive materials. The heat transfer coefficient was as high as 9414.20 W/m2 K with mass flow rate of 0.233 kg/s, ΔT of 1.21 °C, and microalgae concentration of 60 g/L. The falling film evaporation process can be made highly energy efficient if it is coupled with Mechanical Vapor Recompression (MVR) or Thermal Vapor Recompression (TVR) system. Heat and mass transfer characteristics of falling film evaporation of microalgae suspension have been investigated here. This will provide the fundamentals for future feasibility study of utilizing the falling film evaporation in the microalgal industry. 相似文献
106.
《Journal of Nuclear Science and Technology》2013,50(4):159-163
To present a simple method for calculating the worth of control rods in multiregion reactor cores, the well model approximation is applied to the finite difference diffusion code. The results of calculation are compared with experimental results obtained on the ōzenji Critical Facility, and also with calculations using transport equivalent constants. With its simplicity, the method proposed is accurate enough to suffice amply for most cases where only the reactivity is the end result sought, although the application of this method is limited to control rods inserted in the core region, and gives no information about the detailed neutron flux distribution around the control rod. 相似文献
107.
108.
《International Journal of Hydrogen Energy》2022,47(31):14339-14345
The ZnTe material has an unprecedented role in the fabrication of high efficiency CdTe thin film solar cells and optimization of hydrogen annealing induced physical properties of ZnTe films is next required step. Consequently, in the present work, the impact of Hydrogen annealing temperature on the structural, optical, electrical, topographical, morphological, and compositional properties of ZnTe films is explored. The ZnTe thin films (having 300 nm thickness) are grown via electron-beam evaporation technique on glass and ITO substrates followed by annealing at different temperatures under a Hydrogen atmosphere. The ZnTe films are found to crystallize in cubic phase with (111) predominant peak having crystallite size in the range of 19–28 nm, whereas annealed films demonstrated lower optical transmittance vis-à-vis to pristine films. The PL spectra exhibit two luminescence peaks with a stronger band at ~351 nm and a weaker band at ~450 nm. Ohmic behavior of ZnTe films is assured through I–V characteristics, while the AFM images revealed hill-like surface topographies. The FESEM image of pristine films demonstrated a homogeneous surface comprising spherical grains whereas annealed films have spherical, stone, and blisters like morphologies. The EDS patterns assured the Te element richness as well as successful ZnTe films deposition. The observed findings signify that the Hydrogen annealing at different temperatures notably modified the physical properties of ZnTe films. 相似文献
109.
Simulation results for continuous vacuum evaporation crystallization obtained by Aspen Plus and experimental results for semi‐batch vacuum evaporation crystallization are presented. In the crystallization experiments, the fixed heat duty was used to compare the water evaporation rates and crystal properties obtained at different pressures. The solution selected was aqueous glycine. It has the ability to form a number of different crystalline polymorphs, which allows it to exhibit a variety of different physical properties while maintaining its chemical properties. X‐ray diffraction results demonstrated that mainly the γ‐crystal form is produced under the conditions applied in vacuum evaporation crystallization. 相似文献
110.
介绍了机械压缩热泵蒸发技术在离子膜法烧碱装置淡盐水浓缩工艺中的应用,并说明该技术的应用可改变传统的盐水精制工艺,使离子膜法烧碱的生产工艺更趋合理。 相似文献