Resistive superconducting transition of κ-type BEDT-TTF organic superconductors in a magnetic field

The superconducting transition of the organic compoundsκ-(BEDT-TTF)₂ X is studied by resistive measurement in a magnetic field up to 10 T applied normal to the conducting plane. For the salts withX=Cu[N(CN)₂]Br andX=CuCN[N(CN)₂] the transition shows fanshaped broadening caused by superconductivity fluctuation. For theX=Cu(NCS)₂ salt the resistivity shows a peak in the transition region in a magnetic field below 4 T.This phenomenon is suppressed in defect-reduced samples for intralayer conduction. We discuss this peak in relation to the thermal fluctuation on the Josephson junction structures in this salt.     

Plastic deformation of bcc metal thin foils without dislocation

Heavy plastic deformation of fcc metal thin foils to fracture has been found recently to proceed without involving dislocations, and it results in the formation of high density of vacancy clusters. Thin foil specimens of bcc metals such as V and Mo were plastically deformed to fracture in in situ elongation experiments under an electron microscope. Morphology of thinning and fracture was found to be similar to fcc metals, and no dislocation was observed during heavy deformation. Electron diffraction analysis at the tip of a crack during deformation confirmed a large elastic deformation of up to 5%. Unlike in fcc metal thin foil specimens, point defect clusters were not observed near fractured tips. This difference is attributed to the difference in vacancy reaction, though the deformation in bcc metals without dislocation most likely does produce vacancies.     

Defect structure of gold introduced by high-speed deformation

The effect of deformation speed on defect structures introduced into bulk gold specimens at 298 K has been investigated systematically over a wide range of strain rate from ′=10⁻² to 10⁶ s⁻¹. As strain rate increased, dislocation structure changed from heterogeneous distribution, so-called cell structure, to random distribution. Also, stacking fault tetrahedra (SFTs) were produced at anomalously high density by deformation at high strain rate. The anomalous production of SFTs observed at high strain rate is consistent with the characteristic microstructure induced by dislocation-free plastic deformation, which has been recently reported in deformation of gold thin foils. Thus, the results of the present study indicate that high-speed deformation induces an abnormal mechanism of plastic deformation, which falls beyond the scope of dislocation theory. Numerical analysis of dislocation structure and SFTs revealed that the transition point of variation of deformation mode is around the strain rate of 10³ s⁻¹.     

回收PET共混物的非等温结晶和熔融行为

采用双螺杆挤出机制备了聚丙烯(PP)/回收聚对苯二甲酸乙二酯(r-PET)、r-PET/马来酸酐接枝PP(PP-g-MAH)和r-PET/甲基丙烯酸缩水甘油酯接枝PP(PP-g-GMA)共混物,并研究了共混物组成、熔融温度与时间以及降温速率对共混物非等温结晶与熔融行为的影响.结果表明,r-PET与PP共混,结晶温度均提高,这与组分间起到异相成核诱导结晶作用有关.r-PET结晶温度随PP-g-MAH用量增加而降低,但受PP-g-GMA用量影响较小;r-PET可提高PP-g-MAH结晶温度,但降低PP-g-GMA结晶温度.熔融温度提高,共混物中PP结晶温度和熔点均降低,r-PET熔融峰形和熔点取决于共混物的熔融温度及界面相互作用.     

不同干热环境对聚苯乙烯老化的严酷度差异

将聚苯乙烯(PS)材料在吉达和吐鲁番2种典型干热自然环境中进行自然暴晒,对PS材料在自然老化过程中的黄色指数、光泽度、雾度等光学性能和表面形貌进行了测试与表征,研究了PS在吉达和吐鲁番的老化行为差异。通过对吐鲁番和吉达两地的太阳辐照和温度2种关键环境条件的量化比较,计算出了2种干热环境的相对严酷度。结果表明,PS材料在干热环境自然老化的过程中出现了光学性能下降,表面颜色变黄,样品发生明显的老化失效的现象,此外,样品在吉达的光学性能下降幅度和颜色变黄程度均高于吐鲁番。通过比较PS材料在2个试验地点的光学性能差异,验证了吐鲁番相对吉达的环境严酷度为0.66。     

钎焊金刚石砂轮磨削石材中金刚石粒度对磨削力的影响研究

本文通过测量不同金刚石粒度的高频感应钎焊金刚石砂轮磨削花岗石过程中的磨削力，对砂轮所受的法向力和切向力进行了研究。对不同粒度条件下磨削深度、进给速度和砂轮线速度对磨削力的影响进行了分析。研究发现磨削力随砂轮线速度的增大而减小，随磨削深度和进给速度的增大而增大，磨削深度对磨削力的影响程度比进给速度大。小粒度金刚石磨削时，磨削三要素对磨削力的影响比大粒度金刚石磨削时大。     

瞬变 / 谐变一体化的大地电磁收发线圈设计

采用瞬变电磁法和谐变电磁法仪器观测地下空间数据并进行融合处理,能够提高探测成像能力,然而现有的瞬变电磁法和谐变电磁法仪器独立成套,必须配置多套仪器分次采集。设计了一种可满足瞬变/谐变两种模式使用的小型、大带宽、高灵敏度大地电磁收发线圈,为便携、浅层高分辨的瞬变/谐变一体化电磁探测系统开发奠定基础。首先,建立了空心线圈传感器等效电路模型,分析了线圈传感器的灵敏度和噪声特性,制作的传感器经过测试表明,在1 125 Hz处,灵敏度为23.12 mV/nT,等效磁噪声9.27 pT/√Hz,传感器带宽1 Hz～100 kHz;然后,通过公式和有限元软件对传感线圈偏心放置时收发耦合进行了计算,确定了收发线圈组合的最佳耦合位置,计算和仿真结果与实际位置分别相差0.21%和0.17%,有效对消了发射磁场(一次场)。构建了时间域和频率域电磁法探测系统,测试表明,设计的瞬变/谐变一体化收发线圈能够满足时间域和频率域电磁法两种探测模式使用。