The main aim of this project was to come up with an efficient method for the purification of graphite to at least 99%. There has been an increasing demand for high-grade graphite products with up to 99.99% carbon that...The main aim of this project was to come up with an efficient method for the purification of graphite to at least 99%. There has been an increasing demand for high-grade graphite products with up to 99.99% carbon that has resulted in the development of various approaches to remove impurities even to parts per million range. Removal of impurities from 94% graphite is important to achieve a high-purity graphite product. Microwave irradiation was used to prepare high-purity graphite from 94% graphite concentrate. The results showed that microwave irradiation could enhance the fixed carbon of flake graphite to a higher level. Under the optimum conditions selected of 4 minutes’ reaction time and 100% microwave output (800 W), a graphite product with a fixed carbon content of 98.845% was obtained from flake graphite concentrate. According to XRD, FTIR and Handheld XRF analysis, impurities mainly composed of Fe, Co, Sr and Zr were present before treatment. After treatment under optimum conditions Fe, which was the major impurity in the sample was reduced from 3.566% to 1.031%. The ash content of graphite under optimum conditions was 1.55%. The crystal structure of flake graphite showed no change. It can be concluded from this study that graphite purification using microwave irradiation increases the carbon content of graphite.展开更多
The authors studied effect of cerium and lanthanum on crystallization parameters anti structure formation of cast iron.It was found that REM additives increased duration and temperature range of eutectic transforma- t...The authors studied effect of cerium and lanthanum on crystallization parameters anti structure formation of cast iron.It was found that REM additives increased duration and temperature range of eutectic transforma- tion and prevented primary graphite precipitation.The change in crystallization pattern of iron is due to the REM effect on graphite nucleation and growth.On the basis of microprobe analysis of REM distribution and the DTA results,a mechanism of the REM effect on iron crystallization and graphite morphology was suggested.展开更多
Using liquid quenching technique,the change of growth mode of graphite in cast iron melt was analysed.Based on the interface structure theory of crystal growth,the concept of multiplication of spiral growth steps was ...Using liquid quenching technique,the change of growth mode of graphite in cast iron melt was analysed.Based on the interface structure theory of crystal growth,the concept of multiplication of spiral growth steps was advanced and two basic multiplication models were given.It was proposed that multiplication of spiral steps is responsible for the change of growth mode of graphite in cast iron melt.The modifying elements such as Ce promote multiplication of spiral steps,which is regarded as the core of modification.Origination of screw dislocation and branch of the sector blocks in radius direction,both of which are essential to spheroidization of graphite in the melt,are caused by multiplication of spiral steps:and so is thickening of graphite plates.展开更多
Heterogeneous template-induced nucleation is a promising way to regulate protein crystallization events and could be employed for purification processes and crystallographic studies.Protein crystallization process wit...Heterogeneous template-induced nucleation is a promising way to regulate protein crystallization events and could be employed for purification processes and crystallographic studies.Protein crystallization process with graphite and graphene oxide,as heterogeneous templates,were investigated.More than 640 hanging drops with different concentrations of Lysozyme(30,50,70,100 mg/mL)and NaCl(0.7,0.9,1.1,1.3,1.5 M)were crystallised at 4 ℃ with or without graphite/graphene oxide templates.The induction times and crystallization process were observed under the microscope.The lysozyme in the solutions with graphite flakes nucleated faster under all the conditions than the lysozyme with equal experimental conditions without templates.The crystals preferred to grow around the edge of graphite flakes than on the flat surfaces.In the droplets with monolayer graphene oxide,more crystals appeared around gra-phene oxide particles,and the faster or slower nucleation processes with templates were dependent on the lysozyme and NaCl concentrations.Graphene oxide templates strongly inhibited nucleation at high lysozyme concentrations but promoted nucleation at low lysozyme concentrations.Both heterogeneous templates changed the crystal morphology and the crystallization kinetics.More crystals were observed in the solution with graphite templatesthan with graphene oxide templates and without any template.展开更多
Highly oriented pyrolitic graphite （HOPG） has high X-ray diffraction efficiency due to its unique mosaic crystal structure, and thus is very suitable for its application to X-ray Thomson scattering measurement of so...Highly oriented pyrolitic graphite （HOPG） has high X-ray diffraction efficiency due to its unique mosaic crystal structure, and thus is very suitable for its application to X-ray Thomson scattering measurement of solid-density plasmas. In this article, by using the K-shell X-ray source from laser-produced Ti plasma, the properties of the HOPG spectrometer are characterized and compared with those of the flat Pentaerythritol （PET） spectrometer. The results show that the diffraction efficiency of the HOPG spectrometer under focusing condition is an order higher than that of the PET spectrometer, while the spectral resolution of the HOPG is about 320, high enough to be used in the measurement of X-ray Thomson scattering spectra.展开更多
Bond-length-difference (BLD) analysis results show that austenrte and cementite containing Mg, Zr. S have very different valence electron structures from Fe -C austenite and cementite. We find that this difference is ...Bond-length-difference (BLD) analysis results show that austenrte and cementite containing Mg, Zr. S have very different valence electron structures from Fe -C austenite and cementite. We find that this difference is the tie of absorption hypothesis, surface tension hypothesis, undercooling hypothesis in graphite spheroidizing theory. By using "the model of valence electron theory of drag-like effect" in our previous paper in crystallization theory, the spheroidizing effect of Mg and Zr and the anti-spheroidizing effect of S can be explained with the valence electron structure data of phases. Therefore, electron theory of graphite spheroidizing can be advanced.展开更多
The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photonic crystal structure was studied using transfer matrix method. Transmission spectra calculations indicate that such a 2D...The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photonic crystal structure was studied using transfer matrix method. Transmission spectra calculations indicate that such a 2D structure has a common band gap from 0.202 to 0.2035 c/a for both H and E polarizations and for all off-plane angles form 0° up to 90°. The presence of such an absolute band gap implies that 2D graphite photonic crystal, which is much easier and more feasible to fabricate, can exhibit some properties of a three-dimensional (3D) photonic crystal.展开更多
文摘The main aim of this project was to come up with an efficient method for the purification of graphite to at least 99%. There has been an increasing demand for high-grade graphite products with up to 99.99% carbon that has resulted in the development of various approaches to remove impurities even to parts per million range. Removal of impurities from 94% graphite is important to achieve a high-purity graphite product. Microwave irradiation was used to prepare high-purity graphite from 94% graphite concentrate. The results showed that microwave irradiation could enhance the fixed carbon of flake graphite to a higher level. Under the optimum conditions selected of 4 minutes’ reaction time and 100% microwave output (800 W), a graphite product with a fixed carbon content of 98.845% was obtained from flake graphite concentrate. According to XRD, FTIR and Handheld XRF analysis, impurities mainly composed of Fe, Co, Sr and Zr were present before treatment. After treatment under optimum conditions Fe, which was the major impurity in the sample was reduced from 3.566% to 1.031%. The ash content of graphite under optimum conditions was 1.55%. The crystal structure of flake graphite showed no change. It can be concluded from this study that graphite purification using microwave irradiation increases the carbon content of graphite.
文摘The authors studied effect of cerium and lanthanum on crystallization parameters anti structure formation of cast iron.It was found that REM additives increased duration and temperature range of eutectic transforma- tion and prevented primary graphite precipitation.The change in crystallization pattern of iron is due to the REM effect on graphite nucleation and growth.On the basis of microprobe analysis of REM distribution and the DTA results,a mechanism of the REM effect on iron crystallization and graphite morphology was suggested.
文摘Using liquid quenching technique,the change of growth mode of graphite in cast iron melt was analysed.Based on the interface structure theory of crystal growth,the concept of multiplication of spiral growth steps was advanced and two basic multiplication models were given.It was proposed that multiplication of spiral steps is responsible for the change of growth mode of graphite in cast iron melt.The modifying elements such as Ce promote multiplication of spiral steps,which is regarded as the core of modification.Origination of screw dislocation and branch of the sector blocks in radius direction,both of which are essential to spheroidization of graphite in the melt,are caused by multiplication of spiral steps:and so is thickening of graphite plates.
基金grateful to the UK EPSRC(Engineering and Physical Sciences Research Council)for support(EP/T005378/1).
文摘Heterogeneous template-induced nucleation is a promising way to regulate protein crystallization events and could be employed for purification processes and crystallographic studies.Protein crystallization process with graphite and graphene oxide,as heterogeneous templates,were investigated.More than 640 hanging drops with different concentrations of Lysozyme(30,50,70,100 mg/mL)and NaCl(0.7,0.9,1.1,1.3,1.5 M)were crystallised at 4 ℃ with or without graphite/graphene oxide templates.The induction times and crystallization process were observed under the microscope.The lysozyme in the solutions with graphite flakes nucleated faster under all the conditions than the lysozyme with equal experimental conditions without templates.The crystals preferred to grow around the edge of graphite flakes than on the flat surfaces.In the droplets with monolayer graphene oxide,more crystals appeared around gra-phene oxide particles,and the faster or slower nucleation processes with templates were dependent on the lysozyme and NaCl concentrations.Graphene oxide templates strongly inhibited nucleation at high lysozyme concentrations but promoted nucleation at low lysozyme concentrations.Both heterogeneous templates changed the crystal morphology and the crystallization kinetics.More crystals were observed in the solution with graphite templatesthan with graphene oxide templates and without any template.
基金supported by National Natural Science Foundation of China(Nos.11175197)CAS Innovative Project of China(KJCX2-YW-N36)Ministry of Education of China(IRT1190)
文摘Highly oriented pyrolitic graphite （HOPG） has high X-ray diffraction efficiency due to its unique mosaic crystal structure, and thus is very suitable for its application to X-ray Thomson scattering measurement of solid-density plasmas. In this article, by using the K-shell X-ray source from laser-produced Ti plasma, the properties of the HOPG spectrometer are characterized and compared with those of the flat Pentaerythritol （PET） spectrometer. The results show that the diffraction efficiency of the HOPG spectrometer under focusing condition is an order higher than that of the PET spectrometer, while the spectral resolution of the HOPG is about 320, high enough to be used in the measurement of X-ray Thomson scattering spectra.
文摘Bond-length-difference (BLD) analysis results show that austenrte and cementite containing Mg, Zr. S have very different valence electron structures from Fe -C austenite and cementite. We find that this difference is the tie of absorption hypothesis, surface tension hypothesis, undercooling hypothesis in graphite spheroidizing theory. By using "the model of valence electron theory of drag-like effect" in our previous paper in crystallization theory, the spheroidizing effect of Mg and Zr and the anti-spheroidizing effect of S can be explained with the valence electron structure data of phases. Therefore, electron theory of graphite spheroidizing can be advanced.
基金This work was supported by the National Natural Science Foundation under Grant No. 10274078. Y. Li is the author to whom the correspondence should be addressed,
文摘The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photonic crystal structure was studied using transfer matrix method. Transmission spectra calculations indicate that such a 2D structure has a common band gap from 0.202 to 0.2035 c/a for both H and E polarizations and for all off-plane angles form 0° up to 90°. The presence of such an absolute band gap implies that 2D graphite photonic crystal, which is much easier and more feasible to fabricate, can exhibit some properties of a three-dimensional (3D) photonic crystal.
