The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is...The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co_3W_3C (M_6 C type). The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M_6C→M_12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W_2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.展开更多
Poly(ethylene- co -chlorotrifluoroethylene) with a 1∶1 molar ratio of ethylene and chlorotrifluoroethylene in composition, PECTFE, is a statistically alternating copolymer widely used in cable coating industry. PECTF...Poly(ethylene- co -chlorotrifluoroethylene) with a 1∶1 molar ratio of ethylene and chlorotrifluoroethylene in composition, PECTFE, is a statistically alternating copolymer widely used in cable coating industry. PECTFE has been commonly characterized as a semicrystalline polymer with crystals melting at 238 ℃. Differential scanning calorimetry, thermal mechanical analysis and dynamic mechanical analysis indicated that PECTFE undergoes a reversible solid-solid transition during cooling and heating in the temperature range between 100 ℃ and 200 ℃. Based on detailed structural analysis via wide angle X-ray diffraction and electron diffraction techniques, we proposed that PECTFE possesses a hexagonal phase above 200 ℃( a =0 60 nm, c =0 49 nm) and an orthorhombic phase( a =0 99 nm, b =0 57 nm, c =0 49 nm) at room temperature.展开更多
In order to study the structure transition during calcination, nano-titania powders prepared by hydrolyzing precipitation approach and calcined at 300, 400, 500, 600 and 700 ℃ were characterized by XRD, TEM and elect...In order to study the structure transition during calcination, nano-titania powders prepared by hydrolyzing precipitation approach and calcined at 300, 400, 500, 600 and 700 ℃ were characterized by XRD, TEM and electron diffraction(ED), respectively. The results show that titania powders calcined below 500 ℃ are almost composed of anatase, rutile appears below 500 ℃ and its ratio increases gradually with increase of calcin temperature; nano-titania particles are smaller than 40 nm mostly and the dispersion is related to calcining temperature; the inter-planar distances of nano-anatase single crystalline change gradually when calcing temperature increases to 500 ℃; so do that of nano-rutile single crystalline when calcining temperature charges from 600 to 700 ℃. The conclusions can be drawn that the temperature of transformation from anatase to rutile is below 500 ℃ and the process carries on gradually. Both inter-planar distances and the structure of nano-titania transform gradually with increasing calcing temperature.展开更多
深部咸水含水层具有巨大的CO_(2)封存潜力,研究致密砂岩CO_(2)-水两相驱替机制对实现高效安全的CO_(2)咸水层封存具有重要意义。对两个具有不同孔隙结构特征的低渗透砂岩开展了CO_(2)-水两相驱替试验,利用核磁共振(nuclear magnetic res...深部咸水含水层具有巨大的CO_(2)封存潜力,研究致密砂岩CO_(2)-水两相驱替机制对实现高效安全的CO_(2)咸水层封存具有重要意义。对两个具有不同孔隙结构特征的低渗透砂岩开展了CO_(2)-水两相驱替试验,利用核磁共振(nuclear magnetic resonance,NMR)和磁共振成像(magnetic resonance imaging,MRI)技术对气驱和吸水两个阶段气水两相的分布进行了定量及可视化研究,分析了岩芯孔径分布、非均质性及渗透率差异等对两相驱替特征的影响机制。研究表明在气驱阶段CO_(2)相优先被捕获在较大的孔隙中,大孔分布较多的岩芯表现出更高的CO_(2)饱和度;但在吸水阶段小孔占比更高、渗透率更低的岩芯内捕获的CO_(2)相不易被水驱走,表现出更高的CO_(2)封存效率;岩芯局部渗透率变化对最终的残余气分布影响显著,渗透率较低的区域具有更高的最终残余气饱和度和封存效率。研究可进一步完善CO_(2)咸水含水层封存项目中的储层优选、高效封存以及安全性评估等理论体系。展开更多
基金Projects(50323008, 50574104) supported by the National Natural Science Foundation of ChinaProject (04JJ3084) supported by the Natural Science Foundation of Hunan Province, China
文摘The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co_3W_3C (M_6 C type). The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M_6C→M_12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W_2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.
文摘Poly(ethylene- co -chlorotrifluoroethylene) with a 1∶1 molar ratio of ethylene and chlorotrifluoroethylene in composition, PECTFE, is a statistically alternating copolymer widely used in cable coating industry. PECTFE has been commonly characterized as a semicrystalline polymer with crystals melting at 238 ℃. Differential scanning calorimetry, thermal mechanical analysis and dynamic mechanical analysis indicated that PECTFE undergoes a reversible solid-solid transition during cooling and heating in the temperature range between 100 ℃ and 200 ℃. Based on detailed structural analysis via wide angle X-ray diffraction and electron diffraction techniques, we proposed that PECTFE possesses a hexagonal phase above 200 ℃( a =0 60 nm, c =0 49 nm) and an orthorhombic phase( a =0 99 nm, b =0 57 nm, c =0 49 nm) at room temperature.
文摘In order to study the structure transition during calcination, nano-titania powders prepared by hydrolyzing precipitation approach and calcined at 300, 400, 500, 600 and 700 ℃ were characterized by XRD, TEM and electron diffraction(ED), respectively. The results show that titania powders calcined below 500 ℃ are almost composed of anatase, rutile appears below 500 ℃ and its ratio increases gradually with increase of calcin temperature; nano-titania particles are smaller than 40 nm mostly and the dispersion is related to calcining temperature; the inter-planar distances of nano-anatase single crystalline change gradually when calcing temperature increases to 500 ℃; so do that of nano-rutile single crystalline when calcining temperature charges from 600 to 700 ℃. The conclusions can be drawn that the temperature of transformation from anatase to rutile is below 500 ℃ and the process carries on gradually. Both inter-planar distances and the structure of nano-titania transform gradually with increasing calcing temperature.
文摘深部咸水含水层具有巨大的CO_(2)封存潜力,研究致密砂岩CO_(2)-水两相驱替机制对实现高效安全的CO_(2)咸水层封存具有重要意义。对两个具有不同孔隙结构特征的低渗透砂岩开展了CO_(2)-水两相驱替试验,利用核磁共振(nuclear magnetic resonance,NMR)和磁共振成像(magnetic resonance imaging,MRI)技术对气驱和吸水两个阶段气水两相的分布进行了定量及可视化研究,分析了岩芯孔径分布、非均质性及渗透率差异等对两相驱替特征的影响机制。研究表明在气驱阶段CO_(2)相优先被捕获在较大的孔隙中,大孔分布较多的岩芯表现出更高的CO_(2)饱和度;但在吸水阶段小孔占比更高、渗透率更低的岩芯内捕获的CO_(2)相不易被水驱走,表现出更高的CO_(2)封存效率;岩芯局部渗透率变化对最终的残余气分布影响显著,渗透率较低的区域具有更高的最终残余气饱和度和封存效率。研究可进一步完善CO_(2)咸水含水层封存项目中的储层优选、高效封存以及安全性评估等理论体系。
