液体低温热导率的测试

介绍了非稳态法测试液体在低温下（－１００～５０℃）的热导率的测试原理、方法，测试了全氟三乙胺的低温热导率。为了提高测试的重复性，采用了相对比较法，并给出了测试装置及测试结果和误差分析。     

Carbon fibre cloth as an electrode material: electrical conductivity and mass transfer

The paper deals with carbon fibre cloth electrodes, employed in the fabrication of composite materials. The electrical conductivity of single bundles, groups of bundles and cloth is studied. Ohm's law applies to the electrical conduction in the direction of the fibre length, but bundle conductivity decreases with the number of fibres in the bundle. Electrochemical mass transfer between a flowing electrolyte and a cloth arranged as a flow-through or a flow-by porous electrode indicates the existence of double porosity in the material. Due to double porosity, only the external surface of the cloth works as an electrode. This finding shows that the material is not suitable for such an application.     

Evolution of the capillary network in a reactive powder concrete during hydration process

Ultrasonic waves in echographic mode, combined with autogenous shrinkage measurements, were used to study the evolution of the capillary network of reactive powder concrete (RPC) from the time after the mixing. Two characteristic porous classes have been identified: the first, between 10 and 20 nm, begins when the material reaches its solid hyperstatic state, and the second about 1 or 2 nm. The first class is associated with the porous space between the C-S-H hydrate clusters and the second with the internal porosity of the hydrate. The evolution of the active capillary radius as a function of the degree of hydration allows us to understand the strong interaction between the capillary network size and the chemical activity given by the dissipated calorimetric power curve. Indeed, the maximum point of the chemical activity marks the transition of the first class of pores to the second one. Finally, measurements of electrical conductivity through RPC samples show that after the maximum of the dissipated power, the curve of this electrical conductivity presents the same evolution as the capillary radius. As the electrical conductivity clearly depends on the evolution of the capillary network, the similarity between the results confirms our analysis in pore classes.     

掺杂聚苯胺的表面接枝共聚改性

化学氧化法制备的聚苯胺表面的亲水性差，本文在本征态和不同酸掺杂志聚苯胺的表面上接枝共聚丙烯丙烯酸和丙烯酰胺，明显地改善了聚苯胺的表面亲水性。结果显示，聚苯胺表面经过等离子体处理后，有利于丙烯酸和丙烯酰胺在聚苯胺表面上的接枝共聚，随着接枝量增多，导电率则随之有所下降，此外，利用ＳＥＭ和反射ＩＲ表征了改性反聚苯胺表面的形态和结构。     

Assessment of Capillary Rise from Shallow Groundwater by the Simulation Model SIMWASER Using Either Estimated Pedotransfer Functions or Measured Hydraulic Parameters

The performance of the water balance and crop growth model SIMWASER to estimate the water supply of a lawn by capillary rise from shallow ground water was investigated by using lysimeter measurements with a sandy and a clayey soil. Moreover the robustness of the model was evaluated by running it either with measured hydraulic soil parameters or with estimated pedotransfer functions (PTFs) derived from texture and bulk density. Simulations were performed for the years 1996–1998 with input data from the lysimeter station Berlin-Dahlem (Germany) for lysimeters containing undisturbed sandy or clayey soil monoliths, with groundwater at 135 cm depth. Simulated evapotranspiration and percolation/capillary rise were in good agreement with the measured data for all variants, while simulated soil water storage was acceptable only for the variants using hydraulic soil data based on laboratory measurements or using PTFs derived from known soil class and bulk density. PTFs based on mean total pore volume of the respective soil classes yielded soil water storages which were evidently too high; therefore they should be used with care and must be avoided at all in simulating the soil water balance of arid sites with shallow groundwater.     

制备方法对复合触头材料导电特性的影响

根据复合材料制备方法的各自特点 ,建立了计算复合触头材料电导率的三维单元网络模型。应用该模型研究了制备方法对材料电导率的影响 ,并与测量值进行了比较。结果表明了这种模型的可行性。     

水性聚氨酯电导率与聚沉值的研究

研究了软（硬）段含羧基的水性阴离子纳米聚氨酯体系的n(NCO)/n(OH)比值，COOH的质量分类，反离子各类，合成方法与电导率关系及产生的原因；探讨了该体系的n(NCO)/n(OH)值，COOH的质量分数，合成方法与临界聚沉值（Cc.c)的关系和规律。并分析，比较了软（硬）段含羧基的水性阴离子聚氨酯体系电导率与Cc.c二者关系，得出了随COOH的质量分数升高，二者变化相同，随n(NCO)/n(OH)比值升高,二者变化相反的结论。     

纳米4-H碳化硅薄膜的掺杂现象

对纳米晶SiC薄膜进行了P和B的掺杂,B掺杂效率比P高,其暗电导预前因子与激活能遵守Meyer-Neldel规则,并有反转Meyer-Neldel规则出现.掺杂效率比非晶态碳化硅薄膜高是纳米碳化硅薄膜的特点之一.非晶态中的隧穿和边界透射对输运有一定贡献.     

Stability of Standard Electrolytic Conductivity Solutions in Glass Containers

The stability of solutions having an electrolytic conductivity, κ, of 5 μS/cm to 100 000 μS/cm packaged in glass screw-cap bottles, glass serum bottles, and glass ampoules was monitored for 1 year to 2 years. The conductivity was determined by measuring the ac resistance of the solution. Mass loss was also monitored for solutions packaged in bottles. The solutions were prepared using KCl in water (κ ≥100 μS/cm) or KCl in 30 % (by mass) n-propanol 70 % (by mass) water (κ ≤ 15 μS/cm). The conductivity changes were compared by packaging type and by nominal κ. The main causes of the κ changes are evaporation (screw-cap bottles) and leaching (screw-cap bottles, serum bottles, and ampoules). Evaporation is determined from mass loss data; leaching occurs from the glass container with no change in mass. The choice of optimal packaging, which depends on the conductivity level, is the packaging in which κ changes the least with time. Ampoules are the most suitable packaging for standards having nominal κ values of 500 μS/cm to 100 000 μS/cm. Screw-cap bottles are most suitable for standards having a nominal κ of 5 μS/cm to 100 μS/cm.     

Development of High Thermal Conductivity Aluminum Nitride Ceramic

AIN ceramics with densities varying from 3.18 to 3.30 g/cm³ and room-temperature thermal conductivities varying from 88 to 193 W/m K were produced. Different sintering conditions, packing powders, AIN powder sources, carbon additive, and sintering times were evaluated, and the key processing parameters which cause the differences in density and thermal conductivity were identified. SEM, TEM, and EDS were used to characterize the correlation between thermal conductivity, microstructure, and processing parameters. The important parameters which control the thermal conductivity of AIN ceramics are discussed.