The Zn2＋, Ni2＋ and Co3＋ doped Sr14Cu24041 compounds were synthesized by standard solid state method. X-ray diffraction results show that the changes in lattice parameters are very small. Selected area electron diff...The Zn2＋, Ni2＋ and Co3＋ doped Sr14Cu24041 compounds were synthesized by standard solid state method. X-ray diffraction results show that the changes in lattice parameters are very small. Selected area electron diffraction patterns （EDPs） show that the diffraction spots corresponding to the CuO2 chain substructure are extended to streaks along a＊ and b＊ directions for all the samples, while the diffraction spots produced merely by the Cu203 ladder substructure are still very sharp. This means that the periodicities of chains in a＊ and b＊ directions are partially destroyed upon doping ofZn, Ni and Co due to that the initial phase of each chain becomes a random variable. The temperature dependence of magnetic properties was measured for every sample. And the number of dimers in CuO2 chain per formula unit （f.u.） and dimer coupling constant are obtained by fitting the temperature dependence of the magnetic susceptibility. It is found that the degree of initial phase disorder is related to the order degree of magnetic sequence in CuO2 chain. For the un-doped sample, the decoupling of dimers is weak, the magnetic sequence is slightly destroyed, and the streaks in EDP are also very weak, which implies the degree of initial phase disorder in CuO2 chain is very low. When Zn2~ and Ni2＋ ions are doped, the number of dimers per f.u. decreases, and the intensity of diffraction streaks increases in comparison with the corresponding spots. Furthermore, when the high spin magnetic ions Co3＋ are doped, the number of holes in Sr14Cu24041 decreases, the magnetic sequence is destroyed very seriously, and the spots in EDP are extended to streaks almost completely. The phenomenon that the diffraction spots ofCuO2 chain extend to streaks in EDP appears as evidence that the magnetic sequence in the CuO2 chain is destroyed by doping of Zn, Ni, Co.展开更多
Richard Wright was one of America’s greatest black writers andone of the first African American writers to achieve liter⁃ary fame and fortune.Black Boy(1945)ishis autobiographical novel,consisting of Southern Nightan...Richard Wright was one of America’s greatest black writers andone of the first African American writers to achieve liter⁃ary fame and fortune.Black Boy(1945)ishis autobiographical novel,consisting of Southern Nightand Fear and Honor,which tells the story of the protagonist's experiences in five different environments and his great changes.This thesis explores the interaction between space and characters.It finds that,on the one hand,space provides a place for the characters to move around,which af⁃fects them physically and psychologically and shapes their personality.On the other hand,characters make resistances against space,and their behavior and living conditions further reflect the characteristics of each space.Through research,the protagonist grows under the change of spaces,and such growth also highlights the characteristics of different spaces.The interaction between the two carries all the transitions between the stories.展开更多
Richard Wright was an African American novelist and critic,whose works were known for the themes of African Ameri-can and racist.And Black Boy(1945)is his autobiographical novel,which consists of two parts:Southern Ni...Richard Wright was an African American novelist and critic,whose works were known for the themes of African Ameri-can and racist.And Black Boy(1945)is his autobiographical novel,which consists of two parts:Southern Night and The Horror andthe Glory.It mainly tells about how the protagonist had transformed from an innocent child to a mature youth.This thesis analyzesBlack Boy from the perspective of spatial narrative.Firstly,it analyzes three kinds of narrative spaces:physical space,social spaceand psychological space.Physical space is the real and concrete environment in which the protagonist lives.The five physical spac-es have their own characteristics,which serve as the background of the whole story and foreshadow the growth of the protagonist.So-cial space refers to the current conditions of the society,including the social reality in the space and the values that people have.The social space in the book is full of class,racial discrimination and cultural differences,which is the epitome of the society.Psy-chological space is the subconscious activity of the protagonist’s inner world,including his inner monologue and psychological ac-tivities.The protagonist is eager to establish a world of freedom and equality.展开更多
A new process to synthesize polycrystalline samples of Sr14Cu24O41 was presented. Firstly, dry gel powder of Sr14Cu24O41 was synthesized by the citrates sol-gel method, using Sr（NO3）2, Cu（NO3）2, ethylene glycol an...A new process to synthesize polycrystalline samples of Sr14Cu24O41 was presented. Firstly, dry gel powder of Sr14Cu24O41 was synthesized by the citrates sol-gel method, using Sr（NO3）2, Cu（NO3）2, ethylene glycol and citrate acid as raw materials. Then, polycrystalline samples of Sr14Cu24O41 were prepared by solid-state reaction. Thermal Gravimetric and Differential Thermal Analysis（TG-DTA） showed that the temperature for solid-state reaction is at 942 ℃. The samples are identified to be single phase by X-ray Diffraction（XRD） and Scanning Electron Microscopy（SEM）. The SEM pictures showed that the first-step particles were at even size of about 100 nm by this technique. The electronic transport measurements showed that the doping compound were semiconductor with a crossover temperature T in the Arrhenius plot of the resistivity versus temprature.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.10674105 and 50471028)
文摘The Zn2＋, Ni2＋ and Co3＋ doped Sr14Cu24041 compounds were synthesized by standard solid state method. X-ray diffraction results show that the changes in lattice parameters are very small. Selected area electron diffraction patterns （EDPs） show that the diffraction spots corresponding to the CuO2 chain substructure are extended to streaks along a＊ and b＊ directions for all the samples, while the diffraction spots produced merely by the Cu203 ladder substructure are still very sharp. This means that the periodicities of chains in a＊ and b＊ directions are partially destroyed upon doping ofZn, Ni and Co due to that the initial phase of each chain becomes a random variable. The temperature dependence of magnetic properties was measured for every sample. And the number of dimers in CuO2 chain per formula unit （f.u.） and dimer coupling constant are obtained by fitting the temperature dependence of the magnetic susceptibility. It is found that the degree of initial phase disorder is related to the order degree of magnetic sequence in CuO2 chain. For the un-doped sample, the decoupling of dimers is weak, the magnetic sequence is slightly destroyed, and the streaks in EDP are also very weak, which implies the degree of initial phase disorder in CuO2 chain is very low. When Zn2~ and Ni2＋ ions are doped, the number of dimers per f.u. decreases, and the intensity of diffraction streaks increases in comparison with the corresponding spots. Furthermore, when the high spin magnetic ions Co3＋ are doped, the number of holes in Sr14Cu24041 decreases, the magnetic sequence is destroyed very seriously, and the spots in EDP are extended to streaks almost completely. The phenomenon that the diffraction spots ofCuO2 chain extend to streaks in EDP appears as evidence that the magnetic sequence in the CuO2 chain is destroyed by doping of Zn, Ni, Co.
文摘Richard Wright was one of America’s greatest black writers andone of the first African American writers to achieve liter⁃ary fame and fortune.Black Boy(1945)ishis autobiographical novel,consisting of Southern Nightand Fear and Honor,which tells the story of the protagonist's experiences in five different environments and his great changes.This thesis explores the interaction between space and characters.It finds that,on the one hand,space provides a place for the characters to move around,which af⁃fects them physically and psychologically and shapes their personality.On the other hand,characters make resistances against space,and their behavior and living conditions further reflect the characteristics of each space.Through research,the protagonist grows under the change of spaces,and such growth also highlights the characteristics of different spaces.The interaction between the two carries all the transitions between the stories.
文摘Richard Wright was an African American novelist and critic,whose works were known for the themes of African Ameri-can and racist.And Black Boy(1945)is his autobiographical novel,which consists of two parts:Southern Night and The Horror andthe Glory.It mainly tells about how the protagonist had transformed from an innocent child to a mature youth.This thesis analyzesBlack Boy from the perspective of spatial narrative.Firstly,it analyzes three kinds of narrative spaces:physical space,social spaceand psychological space.Physical space is the real and concrete environment in which the protagonist lives.The five physical spac-es have their own characteristics,which serve as the background of the whole story and foreshadow the growth of the protagonist.So-cial space refers to the current conditions of the society,including the social reality in the space and the values that people have.The social space in the book is full of class,racial discrimination and cultural differences,which is the epitome of the society.Psy-chological space is the subconscious activity of the protagonist’s inner world,including his inner monologue and psychological ac-tivities.The protagonist is eager to establish a world of freedom and equality.
基金the National Natural Science Foundation of China(No.10474074)State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology)(No.WUT 2004 M03)
文摘A new process to synthesize polycrystalline samples of Sr14Cu24O41 was presented. Firstly, dry gel powder of Sr14Cu24O41 was synthesized by the citrates sol-gel method, using Sr（NO3）2, Cu（NO3）2, ethylene glycol and citrate acid as raw materials. Then, polycrystalline samples of Sr14Cu24O41 were prepared by solid-state reaction. Thermal Gravimetric and Differential Thermal Analysis（TG-DTA） showed that the temperature for solid-state reaction is at 942 ℃. The samples are identified to be single phase by X-ray Diffraction（XRD） and Scanning Electron Microscopy（SEM）. The SEM pictures showed that the first-step particles were at even size of about 100 nm by this technique. The electronic transport measurements showed that the doping compound were semiconductor with a crossover temperature T in the Arrhenius plot of the resistivity versus temprature.
