Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and...Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity ( i H c) increases while the saturation magnetization( σ s) and remanence ( σ r) decrease. The Curie temperature for the as cast Nd 60 Fe 30- x Al 10 Co x alloys increases from 451 K for x =0 to 468 K for x =10. Some precipitation of crystalline phases does not affect the hard magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized.展开更多
The liquid crystalline behavior of anisotropic solutions in 100% sulphuric acid of aromatic copolyamide obtained by low-temperature solution copolycondensation of terephthalic acid chloride (TPC), p-phenylene diamine ...The liquid crystalline behavior of anisotropic solutions in 100% sulphuric acid of aromatic copolyamide obtained by low-temperature solution copolycondensation of terephthalic acid chloride (TPC), p-phenylene diamine (PPD) and 4, 4'-diamino-diphenylether (DAPE) has been studied by optical microscopy and X-ray diffraction. The effects of inherent viscosity, concentration of copolyamide in sulphuric acid, the content of the third monomer (DAPE) and sequence distribution of copolyamide on the critical concentration, isotropic temperature, phase diagram and texture of liquid crystal were investigated. The schlieren texture was observed and the results of X-ray diffraction indicate that the concentrated solutions of copolyamide exhibit nematic liquid crystalline behavior.展开更多
The synthesis and phase behavior of a series of 4'-alkyloxy -4-hydroxy biphenyls were discribed.The effects of reaction conditions on the yields of products were investigated.The characterizations of thermotropic ...The synthesis and phase behavior of a series of 4'-alkyloxy -4-hydroxy biphenyls were discribed.The effects of reaction conditions on the yields of products were investigated.The characterizations of thermotropic liquid crystalline products for the type and thermal properties are discussed through the use of differential scanning calorimetry,polarizing microscopy.展开更多
The Nd_(60)Fe_(20)Al_8Co_(10)B_2 alloy was prepared by suction casting of the molten alloy into a copper mold under argon atmosphere. The micro-structural and magnetic property changes in the Nd_(60)Fe_(20)Al_8Co_(10)...The Nd_(60)Fe_(20)Al_8Co_(10)B_2 alloy was prepared by suction casting of the molten alloy into a copper mold under argon atmosphere. The micro-structural and magnetic property changes in the Nd_(60)Fe_(20)Al_8Co_(10)B_2 alloy during crystallization were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and the vibrating sample magnetometer (VSM). The precipitation and Nd-rich and Fe-rich phases have no significant effect on the intrinsic coercitity for Nd_(60)Fe_(20)Al_8Co_(10)B_2 alloy annealed below 723 K. However, the growth of Fe-rich phase decreases the saturate magnetization and remanence of the alloy. The hard magnetic behavior is disappeared when the alloy is fully crystallized.展开更多
In this work, the effects of annealing conditions on the microstructure of polypropylene（PP） precursor films and further on the porous structure and permeability of stretched membranes were investigated. Combination...In this work, the effects of annealing conditions on the microstructure of polypropylene（PP） precursor films and further on the porous structure and permeability of stretched membranes were investigated. Combinations of WAXD, FTIR, DSC and DMA results clearly showed the crystalline orientation and crystallinity of the precursor film increased with annealing temperature, while the molecular chain entanglements in the amorphous phase decreased. Changes in the deformation behavior suggested more lamellar separation occurred for the films annealed at higher temperatures. Surface morphologies of the membranes examined by SEM revealed more pore number and uniform porous structure as the annealing temperature increased. In accordance with the SEM results, the permeability of the membranes increased with annealing temperature. On the other hand, it was found that 10 min was almost enough for the annealing process to obtain the microporous membranes with an optimal permeability.展开更多
文摘Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity ( i H c) increases while the saturation magnetization( σ s) and remanence ( σ r) decrease. The Curie temperature for the as cast Nd 60 Fe 30- x Al 10 Co x alloys increases from 451 K for x =0 to 468 K for x =10. Some precipitation of crystalline phases does not affect the hard magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized.
文摘The liquid crystalline behavior of anisotropic solutions in 100% sulphuric acid of aromatic copolyamide obtained by low-temperature solution copolycondensation of terephthalic acid chloride (TPC), p-phenylene diamine (PPD) and 4, 4'-diamino-diphenylether (DAPE) has been studied by optical microscopy and X-ray diffraction. The effects of inherent viscosity, concentration of copolyamide in sulphuric acid, the content of the third monomer (DAPE) and sequence distribution of copolyamide on the critical concentration, isotropic temperature, phase diagram and texture of liquid crystal were investigated. The schlieren texture was observed and the results of X-ray diffraction indicate that the concentrated solutions of copolyamide exhibit nematic liquid crystalline behavior.
文摘The synthesis and phase behavior of a series of 4'-alkyloxy -4-hydroxy biphenyls were discribed.The effects of reaction conditions on the yields of products were investigated.The characterizations of thermotropic liquid crystalline products for the type and thermal properties are discussed through the use of differential scanning calorimetry,polarizing microscopy.
文摘The Nd_(60)Fe_(20)Al_8Co_(10)B_2 alloy was prepared by suction casting of the molten alloy into a copper mold under argon atmosphere. The micro-structural and magnetic property changes in the Nd_(60)Fe_(20)Al_8Co_(10)B_2 alloy during crystallization were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and the vibrating sample magnetometer (VSM). The precipitation and Nd-rich and Fe-rich phases have no significant effect on the intrinsic coercitity for Nd_(60)Fe_(20)Al_8Co_(10)B_2 alloy annealed below 723 K. However, the growth of Fe-rich phase decreases the saturate magnetization and remanence of the alloy. The hard magnetic behavior is disappeared when the alloy is fully crystallized.
基金financially supported by the National Natural Science Foundation of China(No.51273132)Chinese Scholarship Council(CSC)
文摘In this work, the effects of annealing conditions on the microstructure of polypropylene（PP） precursor films and further on the porous structure and permeability of stretched membranes were investigated. Combinations of WAXD, FTIR, DSC and DMA results clearly showed the crystalline orientation and crystallinity of the precursor film increased with annealing temperature, while the molecular chain entanglements in the amorphous phase decreased. Changes in the deformation behavior suggested more lamellar separation occurred for the films annealed at higher temperatures. Surface morphologies of the membranes examined by SEM revealed more pore number and uniform porous structure as the annealing temperature increased. In accordance with the SEM results, the permeability of the membranes increased with annealing temperature. On the other hand, it was found that 10 min was almost enough for the annealing process to obtain the microporous membranes with an optimal permeability.
