The partially disentangled polymer samples prepared are expected to crystallize easier than bulk polymers,which can be attributed to much fewer interchain entanglements within and between particles.Poly(vinyl chloride...The partially disentangled polymer samples prepared are expected to crystallize easier than bulk polymers,which can be attributed to much fewer interchain entanglements within and between particles.Poly(vinyl chloride) (PVC) samples were prepared by freeze-extracting the solutions in various solvents and with varying concentrations.The results of FTIR analysis showed that when the concentrations of the solutions were lower than the overlap concentration c*,the PVC samples prepared from the good solvent had more ordered structure due to much fewer interchain entanglements.While the concentrations of the solutions were higher than c*,the PVC samples prepared from the bad solvents had more ordered structure.展开更多
介绍了含长周期堆垛有序结构(Long period stacking order,简称LPSO结构)的Mg-RE-Zn(-Zr)合金的研究现状,重点分析了Mg-Gd-Zn(-Zr)合金中14H-LPSO结构的最新研究进展,综述了等通道角挤压和搅拌摩擦加工工艺在镁合金强韧化中的应用现状,...介绍了含长周期堆垛有序结构(Long period stacking order,简称LPSO结构)的Mg-RE-Zn(-Zr)合金的研究现状,重点分析了Mg-Gd-Zn(-Zr)合金中14H-LPSO结构的最新研究进展,综述了等通道角挤压和搅拌摩擦加工工艺在镁合金强韧化中的应用现状,提出了当前Mg-Gd-Zn(-Zr)合金研究需解决的主要问题和未来研究方向,展望了等通道角挤压和搅拌摩擦加工工艺在Mg-Gd-Zn(-Zr)合金强韧化方面的应用前景。展开更多
It was demonstrated that some level of order exists in glassy poly(ethylene terephthalate) by depolarized light intensity(DLI) technique, but this order is different from that in crystalline PET. The degree of order i...It was demonstrated that some level of order exists in glassy poly(ethylene terephthalate) by depolarized light intensity(DLI) technique, but this order is different from that in crystalline PET. The degree of order in glassy PET decrease with increasing temperature between 288-343 K. The active energy of this transition is about 22 56 kJ/mol. The IR analysis indicated that this order relates to gauche structure of the ethyleneglycol fragments. The decrease of order with temperature comes from the increase of distance between the order segments.展开更多
用高分辨透射电子显微技术(high resolution transmission electron microscopy,HRTEM)和选区电子衍射(selected area electron diffraction,SAED)技术对具有A位复合钙钛矿结构的0.94(Na1/2Bi1/2)TiO3(BNT)–0.06BaTiO3(BNBT6)陶瓷的显...用高分辨透射电子显微技术(high resolution transmission electron microscopy,HRTEM)和选区电子衍射(selected area electron diffraction,SAED)技术对具有A位复合钙钛矿结构的0.94(Na1/2Bi1/2)TiO3(BNT)–0.06BaTiO3(BNBT6)陶瓷的显微结构进行了深入研究。沿[001],[011]和[111]3个晶带轴方向的SAED花样分析结果表明:A位Bi3+和Na+可以形成2种不同的有序结构——1/2{110}和1/2{111}超结构。据此,建立了BNT的1/2{110}和1/2{111}有序结构模型,其中1/2{110}型有序是由Bi3+层和Na+层沿[110]方向交替排列而形成,1/2{111}型有序是由Bi3+层和Na+层沿[111]方向交替排列而形成。利用多层法,通过计算机模拟了1/2{111}有序结构沿[001],[011]和[111]3个方向的HRTEM像,与实验拍摄的HRTEM像对照,验证了所建立的1/2{111}有序结构模型的正确性。同时,采用快速Fourier变换(fast Fourier transformation,FFT)技术,由1/2(330)和1/2(330)超晶格反射斑点获得的一维晶格像,揭示了沿[110]方向局部Bi3+层和Na+层扭曲导致的位错和反相畴界(anti-phase boundary,APB),APB的存在表明结构中存在着Bi3+层和Na+层沿[110]方向的交替排列,证实BNBT6中存在着1/2{110}有序结构。BNBT6有序结构的HRTEM研究表明:A位Bi3+和Na+的化学有序是导致超晶格反射的主要原因。展开更多
文摘The partially disentangled polymer samples prepared are expected to crystallize easier than bulk polymers,which can be attributed to much fewer interchain entanglements within and between particles.Poly(vinyl chloride) (PVC) samples were prepared by freeze-extracting the solutions in various solvents and with varying concentrations.The results of FTIR analysis showed that when the concentrations of the solutions were lower than the overlap concentration c*,the PVC samples prepared from the good solvent had more ordered structure due to much fewer interchain entanglements.While the concentrations of the solutions were higher than c*,the PVC samples prepared from the bad solvents had more ordered structure.
文摘介绍了含长周期堆垛有序结构(Long period stacking order,简称LPSO结构)的Mg-RE-Zn(-Zr)合金的研究现状,重点分析了Mg-Gd-Zn(-Zr)合金中14H-LPSO结构的最新研究进展,综述了等通道角挤压和搅拌摩擦加工工艺在镁合金强韧化中的应用现状,提出了当前Mg-Gd-Zn(-Zr)合金研究需解决的主要问题和未来研究方向,展望了等通道角挤压和搅拌摩擦加工工艺在Mg-Gd-Zn(-Zr)合金强韧化方面的应用前景。
文摘It was demonstrated that some level of order exists in glassy poly(ethylene terephthalate) by depolarized light intensity(DLI) technique, but this order is different from that in crystalline PET. The degree of order in glassy PET decrease with increasing temperature between 288-343 K. The active energy of this transition is about 22 56 kJ/mol. The IR analysis indicated that this order relates to gauche structure of the ethyleneglycol fragments. The decrease of order with temperature comes from the increase of distance between the order segments.
文摘用高分辨透射电子显微技术(high resolution transmission electron microscopy,HRTEM)和选区电子衍射(selected area electron diffraction,SAED)技术对具有A位复合钙钛矿结构的0.94(Na1/2Bi1/2)TiO3(BNT)–0.06BaTiO3(BNBT6)陶瓷的显微结构进行了深入研究。沿[001],[011]和[111]3个晶带轴方向的SAED花样分析结果表明:A位Bi3+和Na+可以形成2种不同的有序结构——1/2{110}和1/2{111}超结构。据此,建立了BNT的1/2{110}和1/2{111}有序结构模型,其中1/2{110}型有序是由Bi3+层和Na+层沿[110]方向交替排列而形成,1/2{111}型有序是由Bi3+层和Na+层沿[111]方向交替排列而形成。利用多层法,通过计算机模拟了1/2{111}有序结构沿[001],[011]和[111]3个方向的HRTEM像,与实验拍摄的HRTEM像对照,验证了所建立的1/2{111}有序结构模型的正确性。同时,采用快速Fourier变换(fast Fourier transformation,FFT)技术,由1/2(330)和1/2(330)超晶格反射斑点获得的一维晶格像,揭示了沿[110]方向局部Bi3+层和Na+层扭曲导致的位错和反相畴界(anti-phase boundary,APB),APB的存在表明结构中存在着Bi3+层和Na+层沿[110]方向的交替排列,证实BNBT6中存在着1/2{110}有序结构。BNBT6有序结构的HRTEM研究表明:A位Bi3+和Na+的化学有序是导致超晶格反射的主要原因。
