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排序方式: 共有142条查询结果,搜索用时 453 毫秒
51.
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We have investigated interfacial chemistry in a 100 nm Ni on PTFE (polytetrafluoroethylene) bilayer system induced by 120 MeV Au ions with fluences varying from 1 × 1012 to 5 × 1013 ions/cm2. In-situ quadrupole mass analysis (QMA) shows emission of Fluorine (F) and different fluorocarbons (CxFy) such as CF, CF3, C2F3 etc. during irradiation. Electron spectroscopy for chemical analysis (ESCA) studies show that Ni reacts with chemically reactive species such as F−/F and CxFy ions or radicals emitted during irradiation forming NiF2 and metal-polymer complexes (-CFNi-). Rutherford backscattering spectrometry (RBS) was used to analyze the atomic transport at the interface and strong interface mixing is observed at the ion fluence 5 × 1013 ions/cm2. Atomic force microscopy (AFM) studies before and after irradiation show that surface roughness is increased from 6.9 to 12.4 nm with increasing fluence. Observed results have been explained on the basis of the chemical reactions taking place within molten ion tracks in the polymer and hot zones around the ion paths created in the Ni film. The studies show that swift heavy ion irradiation introduces strong chemical alteration in the system and induces chemical reactions within the ion track, which enhance ion beam mixing in Ni-PTFE bilayer systems. 相似文献
53.
Piyanuch Sommani Hiroshi Tsuji Hiroko Sato Junzo Ishikawa 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(19):3231-3234
We have investigated the irradiation effect of negative-ion implantation on the changes of physical surface property of polytetrafluoroethylene (PTFE) for controlling the adhesion property of stem cells. Carbon negative ions were implanted into PTFE sheets at fluences of 1 × 1014-1 × 1016 ions/cm2 and energies of 5-20 keV. Wettability and atomic bonding state including the ion-induced functional groups on the modified surfaces were investigated by water contact angle measurement and XPS analysis, respectively. An initial value of water contact angles on PTFE decreased from 104° to 88° with an increase in ion influence to 1 × 1016 ions/cm2, corresponding to the peak shifting of XPS C1s spectra from 292.5 eV to 285 eV with long tail on the left peak-side. The change of peak position was due to decrease of C-F2 bonds and increase of C-C bonds with the formation of hydrophilic oxygen functional groups of OH and CO bonds after the ion implantation. After culturing rat mesenchymal stem cells (MSC) for 4 days, the cell-adhesion properties on the C−-patterned PTFE were observed by fluorescent microscopy with staining the cell nuclei and their actin filament (F-actin). The clear adhesion patterning of MSCs on the PTFE was obtained at energies of 5-10 keV and a fluence of 1 × 1015 ions/cm2. While the sparse patterns and the uncontrollable patterns were found at a low fluence of 3 × 1014 ions/cm2 and a high fluence of 3 × 1015 ions/cm2, respectively. As a result, we could improve the surface wettability of PTFE to control the cell-adhesion property by carbon negative-ion implantation. 相似文献
54.
Theoretical and Experimental Studies on Acetylene Absorption in a Polytetrafluoroethylene Hollow‐Fiber Membrane Contactor 下载免费PDF全文
The separation of acetylene from a gas mixture was investigated using a polytetrafluoroethylene hollow‐fiber membrane contactor and 1‐methyl‐2‐pyrrolidinone as absorbent. The effects of the gas velocity, the liquid velocity, the feed gas concentration, and the module length on the acetylene mass transfer were investigated. The results showed that the acetylene mass transfer flux increased with increasing liquid velocity, gas velocity, and feed gas concentration, but decreased with increasing membrane module length. A mathematical model was used to predict the wetting extent of the membrane and the mass transfer resistance in the acetylene mass transfer process. The wetting extent of the membrane was found to increase with increasing liquid velocity and to be effectively restrained with increasing gas velocity. The liquid phase resistance and the wetted‐membrane phase resistance controlled the acetylene mass transfer in the acetylene absorption process. The acetylene absorption efficiency was maintained at 90 % for 114 h of the C2H2 membrane absorption–thermal desorption cycle process. 相似文献
55.
The role of crystalline phase on fracture and microstructure evolution of polytetrafluoroethylene (PTFE) 总被引:1,自引:0,他引:1
Polytetrafluoroethylene (PTFE) is a semi-crystalline polymer, which has been employed in a range of engineering applications due to its extremely low coefficient of friction, resistance to corrosion, and excellent electrical insulation properties. Despite failure-sensitive applications such as surgical implants, aerospace components, motor seals, and barriers for hazardous chemicals, the mechanisms of crack propagation in PTFE have received limited coverage in the literature. Moreover, PTFE exhibits complex crystalline phase behavior that includes four well-characterized phases with both local and long range order. Three crystalline structures (phases II, IV, and I) are observed at atmospheric pressure with transitions between them occurring at 19 and 30 °C. This observation provides a unique opportunity for investigation of the effects of a polymers crystalline phase on fracture and microstructure evolution. Moreover, due to the presence of three unique ambient pressure phases near room temperature, it is essential to develop an understanding of the effects of temperature-induced phase transitions on fracture mechanisms of PTFE to prevent failure over the normal range of operating temperatures. In this work, we present values for the J-integral fracture toughness of PTFE for a range of temperatures and loading rates employing the single specimen normalization technique. Crack propagation in PTFE is found to be strongly phase dependent with a brittle-to-ductile transition in the crack propagation behavior associated with the two room temperature phase transitions. Increases in fracture toughness are shown to result from the onset of stable fibril formation bridging the crack plane and increased plastic deformation. The stability of drawing fibrils is primarily determined by temperature and crystalline phase with additional dependence on loading rate and microstructure anisotropy. [LAUR-05-0004] 相似文献
56.
57.
Superhydrophobic polytetrafluoroethylene thin films with hierarchical roughness deposited using a single step vapor phase technique 总被引:1,自引:0,他引:1
Sushant Gupta Arul Chakkaravarthi Arjunan Sudipta Seal Rajiv K. Singh 《Thin solid films》2009,517(16):4555-3265
Superhydrophobic polytetrafluoroethylene films with hierarchical surface roughness were deposited using pulse electron deposition technique. We were able to modulate roughness of the deposited films by controlling the beam energy and hence the electron penetration depth. The films deposited at higher beam energy showed contact angle as high as 166°. The scanning electron and atomic force microscope studies revealed clustered growth and two level sub-micron asperities on films deposited at higher energies. Such dual-scale hierarchical roughness and heterogeneities at the water-surface interface was attributed to the observed contact angle and thus its superhydrophobic nature. 相似文献
58.
Anh Tuan Pham Tomohiro BabaTatsuki Sugiyama Toshio Shudo 《International Journal of Hydrogen Energy》2013
In a proton exchange membrane (PEM) methanol electrolyzer, the even supply of reactant to and the smooth removal of carbon dioxide from the anode are very important in order to achieve a high hydrogen production performance. An appropriate design of flow field and gas diffusion layer (GDL) is a key factor in satisfying the above requirements. Previous research has shown that hydrogen production performance of the PEM methanol electrolyzer cell was largely improved with a porous flow field made of sintered spherical metal powder compared with a conventional groove type flow field. Based on this improvement, the current study investigated the influence of polytetrafluoroethylene (PTFE) treatment of the anode GDL on hydrogen production performance of the PEM methanol electrolyzer with porous metal flow fields. Influences of operating conditions such as methanol concentration and cell temperature with the flow field were also investigated. 相似文献
59.
聚四氟乙烯加工技术、填充改性及应用进展 总被引:1,自引:0,他引:1
选择聚四氟乙烯(PTFE)为论述对象,概述了聚四氟乙烯的特性和相关的成型加工技术,综述了目前聚四氟乙烯材料的主要填充改性方法,并简述了聚四氟乙烯材料的应用现状,最后还对聚四氟乙烯材料的发展方向及其应用前景进行了展望。 相似文献
60.
Hirotaka Kinoshita Susumu Yonezawa Jae-Ho Kim Masayuki Kawai Masayuki Takashima Toshihide Tsukatani 《Journal of power sources》2008,183(2):464-470
At about 50 wt% Ni content, Ni-plated polytetrafluoroethylene (Ni-PTFE) particles show conductivity of 300 S m−1 when plated on 25 μm PTFE particles. For this study, Ni-PTFE particles were formed into the Ni-PTFE plate using heat treatment at 350 °C after 300 kg cm−2 pressing. The Ni-PTFE plate displayed electrical conductivity and gas permeability. The plate was used as an electrode in an alkaline fuel cell (AFC). In terms of the current density, AFC using the Ni-PTFE electrode plated with Pt or Pd by immersion plating showed improved performance. 相似文献