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991.
The electrical resistivity and morphology of high impact polystyrene (HIPS)/styrene‐butadiene‐styrene triblock copolymer (SBS)/carbon black (CB) blends were studied. Their antistatic sheets were prepared by both compression‐molding and extrusion calendaring process, with their surface morphology observed using scanning electron microscopy (SEM). The SEM images reveal better dispersion of CB achieved in extrusion‐calendering, resulting in low percolation threshold values in HIPS composites. Higher compression ratio and higher drawing speed (corresponding lower sheet thickness) are beneficial to get better CB dispersion, leading to decreased conductivity for the antistatic sheets. SEM images indicate that strong shear forces in extrusion tend to break the conductive network of CB, resulting in increased surface resistivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
992.
采用粉末冶金法制备了碳纳米管增强环氧/石墨复合材料,并研究了酸洗处理对复合材料弯曲强度、硬度和导电性能的影响。结果表明:与未处理碳纳米管相比,酸处理的碳纳米管增加了环氧/石墨复合材料的弯曲强度和硬度,降低了电阻率。酸处理的碳纳米管增强环氧/石墨复合材料的弯曲强度达到21.9MPa,比未添加碳纳米管时提高了近22%;同时复合材料的硬度达到最大值21.7HS,比未添加碳纳米管时提高了近10%;复合材料的电阻率达到了最小值45036μΩ·cm,比未添加碳纳米管时复合材料的电阻率降低了近17%。 相似文献
993.
Silver‐coated copper nanowires (AgCuNWs) are prepared by chemical plating method with copper nanowires (CuNWs) and Ag‐amine reagent. The prepared AgCuNWs with silver content of 66.52 wt.%, diameter 28–33 nm exhibited improved anti‐oxidation behaviour. The silver coating on AgCuNWs can effectively reduce the formation of copper oxide under room temperature. The temperature at which nanowires begin to gain weight can be improved from 85 to 230°C and the maximum weight gain can be decreased from 20.3% to 3.2% by applying silver coating. The volume electrical resistivity of the AgCuNWs filled low‐density polyethylene nanocomposites is lower than that of the CuNWs filled low‐density polyethylene nanocomposites with same volume percentage of fillers because the silver content in the AgCuNWs is not oxidised during compression moulding. © 2012 Canadian Society for Chemical Engineering 相似文献
995.
Composites consisting of carbon fibers (CF) and carbon particles (CP) in polypropylene (PP) matrix were melt-compounded. Composites
were analyzed for their mechanical, electrical and thermal properties. Results indicate that the addition of these fillers
improved the mechanical properties of the composites. Thermal conductivity was enhanced as the concentration of fillers was
increased. Carbon fibers render the composites electrically conductive so we observed a percolation threshold near 10 wt.%
of CF for PP/CF (PP and CF composite) and near 25 wt.% of CP for PP/CP (PP and carbon particle composite). All the results
indicated that carbon fibers are more effective in improving the properties as compare to the carbon particles. 相似文献
996.
Multiwalled carbon nanotube/polycaprolactone nanocomposites (MWNT/PCL) were prepared by in situ polymerization, whereby as‐received MWNTs (P‐MWNTs) and purified MWNTs (A‐MWNTs) were used as reinforcing materials. The A‐MWNTs were purified by nitric acid treatment, which introduced the carboxyl groups (COOH) on the MWNT. The micrographs of the fractured surfaces of the nanocomposites showed that the A‐MWNTs in A‐MWNT/PCL were better dispersed than P‐MWNTs in PCL matrix (P‐MWNT/PCL). Percolation thresholds of the P‐MWNT/PCL and A‐MWNT/PCL, which were studied by rheological properties, were found at ~2 wt % of the MWNT. The conductivity of the P‐MWNT/PCL was between 10?1 and 10?2 S/cm by loading of 2 wt % of MWNT although that of the A‐MWNT/PCL reached ~10?2 S/cm by loading of 7 wt % of MWNT. The conductivity of the P‐MWNT/PCL was higher than that of the A‐MWNT/PCL at the entire range of the studied MWNT loading, which might be due to the destruction of π‐network of the MWNT by acid treatment, although the A‐MWNT/PCL was better dispersed than the P‐MWNT/PCL. The amount of the MWNT at which the conductivity of the nanocomposite started to increase was strongly correlated with the percolation threshold. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1957–1963, 2007 相似文献
997.
998.
采用电阻率法研究水泥水化过程 总被引:35,自引:4,他引:35
用无接触电阻率测定仪测定了不同水灰比水泥浆基体的电阻率随时间变化的特征曲线ρ(t)-t,研究了普通硅酸盐水泥的水化特性。研究表明:基体电阻率ρ(t)是液相电阻率ρ0(t)和孔隙率φ的函数。实验结果说明:根据基体电阻率曲线的特征点将水泥水化过程划分为溶解期、诱导形成期和诱导期、凝结硬化期3个阶段。钙矾石包裹层的形成导致水化进入诱导期,渗透压导致包裹层的破裂,使水化进入凝结硬化期。溶解期电阻率的下降主要与水泥浆体中液相离子浓度的增加相关。诱导形成期和诱导期电阻率变化小,此时液相离子浓度和孔隙率的变化都较小,凝结硬化期电阻率的上升主要与水泥浆体孔隙率的下降相关。 相似文献
999.
在1300~1500℃和30MPa压力下,热压摩尔比为n(TiC)∶n(Ti)∶n(Al)∶n(Si)=2∶1∶(1~1.1)∶(0.2~0.1)的混合粉末,可以得到纯度达98%(质量分数)以上的致密块体碳化铝钛(Ti3AlC2)材料。掺加的Si均匀分布在基体中,形成固溶体。当掺加Si的摩尔比为0.2时,固溶体的化学式为Ti2.76Al0.78Si0.22C2。烧结试样的晶体为层片状结构,1300℃和1400℃时,烧结试样的晶粒尺寸分别为10~15μm和20~30μm。材料的Vicker硬度为3.3~5.0GPa,弹性模量为289GPa,抗压强度为785MPa,抗弯强度为375MPa,断裂韧性为7.0MPa·m1/2。25℃时,电导率为3.1×106S·m-1,热容为125.4J/(mol·K),热导率为27.5W/(m·K),热膨胀系数为8.8×10-6K-1。 相似文献
1000.