结构炭/炭复合材料力学性能及微观结构研究

采用四向编织、快速化学气相渗透致密化新工艺制备了炭／炭复合材料,其弯曲强度达３２０ＭＰａ。分析研究了这种材料的力学性能特征。利用ＳＥＭ和高分辨ＴＥＭ分析了基体炭、炭纤维／基体灰界面的精细结构,发现炭纤维呈单根被基体炭包围,基体现灰呈层片状,为二维有序的乱层石墨结构;在炭纤维与基体炭之间存在着过渡相,这一过渡相厚度的约几十纳米,随着与炭纤维之间距离的增大,它们之间形成的夹角由小变大,这一过渡相即为炭     

INTERFACE/INTERPHASE ENGINEERING OF POLYMERS FOR ADHESION ENHANCEMENT: PART II. THEORETICAL AND TECHNOLOGICAL ASPECTS OF SURFACE-ENGINEERED INTERPHASE-INTERFACE SYSTEMS FOR ADHESION ENHANCEMENT

Part I of this paper reviewed the theoretical principles of the macromolecular design of polymer interface/interphase systems for obtaining maximum adhesion and fracture performance of adhesively bonded assemblies. In Part II a novel, relatively simple and industry-feasible technology for surface-grafting connector molecules is demonstrated and discussed in detail and supported by a range of experimental examples. It is shown, in agreement with contemporary theory, that the use of chemically attached graft chemicals of controlled spatial geometry and chemical functionality enables a significant increase in the strength and fracture energy of the interphase, to the point of cohesive fracture of the substrate, or that of an adjacent medium such as adhesive, elastomer, or other material. This occurs even after prolonged exposure of investigated systems to adverse environments such as hot water.     

A STUDY OF CARBON BLACK DISTRIBUTION AND PROPERTIES IN BR/NBR BLENDS: ROLES OF COMMERCIAL HOMOGENIZER AND SLIPPING AGENT

Effects of commercial processing aids, Struktol NS60 (hydrocarbon resin) homogenizer and Struktol WB16 (a mixture of metal salt and a fatty acid amide) slipping agent on the distribution of carbon black and physical properties in BR/NBR blends have been investigated. It was found that Struktol 60NS and Struktol WB16 in blend systems migrate preferentially to BR phase due to the strong interaction between Struktol and BR phase, leading to a decrease in viscosity of BR phase and thus an increase in carbon black residing in BR phase. Mechanical properties of unfilled compounds are strongly affected by blend ratio and loading of processing aids. However, in the case of filled compounds, the influence of carbon black distribution in each phase of the blends override those blend ratio and additive loading effects.     

SURFACE PROPERTIES OF FUSED SALTS AND GLASSES: II, CONTACT ANGLE AND WORK OF ADHESION ON GOLD AND PLÁTINUM IN VARIOUS ATMOSPHERES

An apparatus is described which allows measurements to be made of the contact angle and the exact dimensions of a sessile drop of liquid resting on an electrode graphite surface in vacua or in nitrogen atmosphere. Temperatures up to 1100°C have been employed. Under these conditions, surface tension and gravity are the only forces acting on the drop, and the exact shape, surface, and volume may be computed from the tables of Bashforth and Adams. The method may be used with liquids having viscosities up to 600 poises, whereas the bubble-pressure method used by Jaeger is limited to liquids of viscosity less than 70 poises. On the basis of internal evidence, the surface-tension values obtained by the sessile-drop method are considered correct within 5%. They also agree with data by Jaeger, but are, roughly, twice as great as those of Washburn and Libmart, who used a ring method. The probable error in Washburn and Libman's work appears to be in their assumption of zero contact angle.     

PREDICTION OF CRITICAL PROPERTIES OF 1-HEXENE/HEXENE ISOMERS/CARBON DIOXIDE MIXTURES WITH A CUBIC EOS: SENSITIVITY TO MIXTURE COMPOSITION AND TO THE PATH OF APPROACH TO CRITICAL POINTS

Critical loci of 1hexene/CO₂ and (hexene isomer pseudo-component)/CO₂ binary mixtures, along with the critical properties of the ternary mixture of CO₂/l-hexene/(hexene isomer pseudo-component) were predicted using Gibbs' thermodynamic criteria for criticality in conjunction with the Peng-Robinson (P-R) EOS. Maximum deviation in the critical pressures of the l-hexene/CO₂ binary mixture is less than 2% from reported experimental values. The addition of hexene isomer to the l-hexene/CO₂ binary and the path of approach to mixture critical points are shown to have surprisingly strong effects on predicted mixture critical properties. For a given ternary mixture, multiple critical points are predicted depending upon the isopleth (either constant CO₂ mole fraction path or constant 1-hexene mole fraction path) along which the critical point is approached. Critical densities predicted along the CO₂ isopleth of approach to critical points are always smaller than the ones predicted along the 1-hexene isopleth of approach. Furthermore, upon hexene isomer addition to the l-hexene/CO₂ binary, whereas the predicted critical property surfaces of the ternary system vary monotonically along the CO₂ isopleth of approach, extrema in these surfaces are predicted when approaching the mixture critical points along 1-hexene isopleths. These anomalous predictions are attributed to the inability of the cubic EOS to accurately model the phase behavior near the critical point.     

Longitudinal diffusion and resistance to mass transfer as causes of nonideality in chromatography : J. J. van Deemter, F. J. Zuiderweg and A. Klinkenberg, Chem. Engng Sci. 5 271–289, 1956

The sharpness of separation in a gas-liquid chromatographic column is effected by longitudinal molecular diffusion, slowness to reach absorption equilibrium, and by flow irregularities in channels and across the column. The total effect of all these causes can be described by a simple equation which can be derived from the rigorous mathematical solution by introducing reasonable simplifying assumptions.