利用热刺激放电(Thermally Stimulated Discharge,TSD)电流谱、在线电荷TSD、电荷等温衰减测量和衰减全反射(Attenuated Total Reflection,ATR)红外光谱分析,本文系统地研究了经化学表面处理(萃取、氧化及氢氟酸)的聚丙烯(PP)孔洞驻极...利用热刺激放电(Thermally Stimulated Discharge,TSD)电流谱、在线电荷TSD、电荷等温衰减测量和衰减全反射(Attenuated Total Reflection,ATR)红外光谱分析,本文系统地研究了经化学表面处理(萃取、氧化及氢氟酸)的聚丙烯(PP)孔洞驻极体膜的电荷储存稳定性及电荷稳定性提高的原因.结果表明:经适当地氧化和氢氟酸室温处理试样的TSD电流谱中在温位约为184℃处出现原膜所没有的非常强的新峰,电荷热稳定性得到显著的提高,这一电荷热稳定性通过高温充电工艺得到进一步地改善;适当延长室温下氢氟酸处理的时间或延长氧化时间,都会使处理膜的电荷稳定性得到提高.理论分析表明在线电荷TSD测量法可给出线性升温过程中电荷重心及驻极体电荷量变化的综合信息,结合TSD电流谱和初始电荷重心位置的测量,可精确地考察线性升温过程中电荷重心的在线变化.展开更多
The grain-size dependence of wear resistance of WC-Co cemented carbides(with mean WC grain sizes of 2.2μm,1.6μm,0.8μm and 0.4μm,respectively)was investigated under different tribological conditions.The results sho...The grain-size dependence of wear resistance of WC-Co cemented carbides(with mean WC grain sizes of 2.2μm,1.6μm,0.8μm and 0.4μm,respectively)was investigated under different tribological conditions.The results showed that the grain size had opposite effects on wear resistance of the cemented carbides in dry sliding wear and microabrasion tests.In the former condition,with decrease of WC grain size hence the increase of hardness,plastic deformation,fracture,fragmentation and oxidation were all mitigated,leading to a drastic decrease in the wear rate.In the latter condition,pull-out of WC grains after Co removal dominated the wear,so that the hardness of cemented carbide was not a core factor.As a result,the wear resistance of the cemented carbide generally showed a decreasing trend with decrease of the grain size,except for a slight increase in the ultrafine-grained cemented carbide.Single-pass scratching of the cemented carbides under various loads indicated the same failure mechanism as that in the sliding wear tests.Furthermore,the reasons for severe surface oxidation of the coarse-grained cemented carbides were disclosed.展开更多
文摘利用热刺激放电(Thermally Stimulated Discharge,TSD)电流谱、在线电荷TSD、电荷等温衰减测量和衰减全反射(Attenuated Total Reflection,ATR)红外光谱分析,本文系统地研究了经化学表面处理(萃取、氧化及氢氟酸)的聚丙烯(PP)孔洞驻极体膜的电荷储存稳定性及电荷稳定性提高的原因.结果表明:经适当地氧化和氢氟酸室温处理试样的TSD电流谱中在温位约为184℃处出现原膜所没有的非常强的新峰,电荷热稳定性得到显著的提高,这一电荷热稳定性通过高温充电工艺得到进一步地改善;适当延长室温下氢氟酸处理的时间或延长氧化时间,都会使处理膜的电荷稳定性得到提高.理论分析表明在线电荷TSD测量法可给出线性升温过程中电荷重心及驻极体电荷量变化的综合信息,结合TSD电流谱和初始电荷重心位置的测量,可精确地考察线性升温过程中电荷重心的在线变化.
基金supported financially by the National Natural Science Foundation of China (Nos.51601004,51631002,51425101 and 51621003)the China Scholarship Council (201806545002)the Program of Top Disciplines Construction in Beijing (No. PXM2019_014204_500031)
文摘The grain-size dependence of wear resistance of WC-Co cemented carbides(with mean WC grain sizes of 2.2μm,1.6μm,0.8μm and 0.4μm,respectively)was investigated under different tribological conditions.The results showed that the grain size had opposite effects on wear resistance of the cemented carbides in dry sliding wear and microabrasion tests.In the former condition,with decrease of WC grain size hence the increase of hardness,plastic deformation,fracture,fragmentation and oxidation were all mitigated,leading to a drastic decrease in the wear rate.In the latter condition,pull-out of WC grains after Co removal dominated the wear,so that the hardness of cemented carbide was not a core factor.As a result,the wear resistance of the cemented carbide generally showed a decreasing trend with decrease of the grain size,except for a slight increase in the ultrafine-grained cemented carbide.Single-pass scratching of the cemented carbides under various loads indicated the same failure mechanism as that in the sliding wear tests.Furthermore,the reasons for severe surface oxidation of the coarse-grained cemented carbides were disclosed.
