Search2008 Vol. 15, No. 5
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2008, vol. 15, no. 5, pp.
521-527.
https://doi.org/10.1016/S1005-8850(08)60098-5
Abstract:
Previous mining excavation in upper sublevels left several mined-out areas in Haigou gold mine. To ensure safety of the main and auxiliary shafts and mining production in deeper sublevels, systematical studies on regularity, prediction, and control of ground pressure in the mine were carried out. Through 3D-numerical modeling and in-situ monitoring of acoustic emission, pressure and displacement, the ground pressure activity and the stability status of surrounding rock masses and the two shafts were assessed. Based on in-situ monitoring practice in Haigou mine,4 modes to judge rock stability according to the monitoring information of acoustic emission,pressure,and displacement were presented.
Previous mining excavation in upper sublevels left several mined-out areas in Haigou gold mine. To ensure safety of the main and auxiliary shafts and mining production in deeper sublevels, systematical studies on regularity, prediction, and control of ground pressure in the mine were carried out. Through 3D-numerical modeling and in-situ monitoring of acoustic emission, pressure and displacement, the ground pressure activity and the stability status of surrounding rock masses and the two shafts were assessed. Based on in-situ monitoring practice in Haigou mine,4 modes to judge rock stability according to the monitoring information of acoustic emission,pressure,and displacement were presented.
2008, vol. 15, no. 5, pp.
528-533.
https://doi.org/10.1016/S1005-8850(08)60099-7
Abstract:
Artificial neural network procedures were used to predict the combustible value (i.e. 100-Ash) and combustible recovery of coal flotation concentrate in different operational conditions. The pulp density,pH,rotation rate,coal particle size,dosage of collector,frother and conditioner were used as inputs to the network. Feed-forward artificial neural networks with 5-30-2-1 and 7-10-3-1 arrangements were capable to estimate the combustible value and combustible recovery of coal flotation concentrate respectively as the outputs. Quite satisfactory correlations of 1 and 0.91 in training and testing stages for combustible value and of 1 and 0.95 in training and testing stages for combustible recovery prediction were achieved. The proposed neural network models can be used to determine the most advantageous operational conditions for the expected concentrate assay and recovery in the coal flotation process.
Artificial neural network procedures were used to predict the combustible value (i.e. 100-Ash) and combustible recovery of coal flotation concentrate in different operational conditions. The pulp density,pH,rotation rate,coal particle size,dosage of collector,frother and conditioner were used as inputs to the network. Feed-forward artificial neural networks with 5-30-2-1 and 7-10-3-1 arrangements were capable to estimate the combustible value and combustible recovery of coal flotation concentrate respectively as the outputs. Quite satisfactory correlations of 1 and 0.91 in training and testing stages for combustible value and of 1 and 0.95 in training and testing stages for combustible recovery prediction were achieved. The proposed neural network models can be used to determine the most advantageous operational conditions for the expected concentrate assay and recovery in the coal flotation process.
2008, vol. 15, no. 5, pp.
534-537.
https://doi.org/10.1016/S1005-8850(08)60100-0
Abstract:
Because there are a lot of influences of alumina inclusions on the performance of rail steel,it is reasonable to adopt the deoxidization method with Al-free deoxidizer. According to the characteristics of Al-free deoxidization process,the control of aluminum content,the deoxidization with ladle furnace(LF) slag,the deoxidization process under vacuum by carbon,and the inclusions modification technology by calcium treatment were studied. All of them were applied to practical production. The results indicate that the adoption of Al-free deoxidization process leads to the total oxygen content in the steel below 20 ppm,which meets the requirement of clean rail steel.
Because there are a lot of influences of alumina inclusions on the performance of rail steel,it is reasonable to adopt the deoxidization method with Al-free deoxidizer. According to the characteristics of Al-free deoxidization process,the control of aluminum content,the deoxidization with ladle furnace(LF) slag,the deoxidization process under vacuum by carbon,and the inclusions modification technology by calcium treatment were studied. All of them were applied to practical production. The results indicate that the adoption of Al-free deoxidization process leads to the total oxygen content in the steel below 20 ppm,which meets the requirement of clean rail steel.
2008, vol. 15, no. 5, pp.
538-542.
https://doi.org/10.1016/S1005-8850(08)60101-2
Abstract:
It is essential for alumina production by alkaline process to know the behavior of minerals containing Al and Si in basic solution,and the behavior of SiO2 in the process of clinker leaching is an important portion. To study the behavior of SiO2 in the process of high concentration clinker leaching,experiments were carried out in home-made reactors. The results indicate that factors,such as temperature,time,Al2O3 concentration,as well as SiO2 concentration,have profound impact on the SiO2 and Al2O3 concen-tration of pregnant liquor during the high concentration leaching. However,sodium carbonate and free caustic soda concentrations have no remarkable effect on it,thus they are the secondary factors compared with Al2O3 concentration. The concentration of SiO2 in the pregnant liquor could be reduced to a lower level when the major effect parameters of this process are controlled properly.
It is essential for alumina production by alkaline process to know the behavior of minerals containing Al and Si in basic solution,and the behavior of SiO2 in the process of clinker leaching is an important portion. To study the behavior of SiO2 in the process of high concentration clinker leaching,experiments were carried out in home-made reactors. The results indicate that factors,such as temperature,time,Al2O3 concentration,as well as SiO2 concentration,have profound impact on the SiO2 and Al2O3 concen-tration of pregnant liquor during the high concentration leaching. However,sodium carbonate and free caustic soda concentrations have no remarkable effect on it,thus they are the secondary factors compared with Al2O3 concentration. The concentration of SiO2 in the pregnant liquor could be reduced to a lower level when the major effect parameters of this process are controlled properly.
2008, vol. 15, no. 5, pp.
543-551.
https://doi.org/10.1016/S1005-8850(08)60102-4
Abstract:
A universal thermodynamic model of calculating the mass action concentrations of components in a ternary strong electrolyte aqueous solution has been developed based on the ion and molecule coexistence theory,and verified in the NaCl-KCl-H2O ternary system at 298.15 K. To compare the difference of the thermodynamic model in binary and ternary strong electrolyte aqueous solutions,the mass action concentrations of components in the NaCl-H2O binary strong electrolyte aqueous solution were also computed at 298.15K. A transformation coefficient was required to compare the calculated mass action concentration and reported activity because they were obtained at different standard states and concentration units. The results show that the transformation coefficients between calculated mass action concentrations and reported activities of the same components change in a very narrow range. The calculated mass action concentrations of components in the NaCl-H2O and NaCl-KCl-H2O systems are in good agreement with the reported activities. This indicates that the developed thermodynamic model can reflect the structural characteristics of solutions,and the mass action concentration also strictly follows the mass action law.
A universal thermodynamic model of calculating the mass action concentrations of components in a ternary strong electrolyte aqueous solution has been developed based on the ion and molecule coexistence theory,and verified in the NaCl-KCl-H2O ternary system at 298.15 K. To compare the difference of the thermodynamic model in binary and ternary strong electrolyte aqueous solutions,the mass action concentrations of components in the NaCl-H2O binary strong electrolyte aqueous solution were also computed at 298.15K. A transformation coefficient was required to compare the calculated mass action concentration and reported activity because they were obtained at different standard states and concentration units. The results show that the transformation coefficients between calculated mass action concentrations and reported activities of the same components change in a very narrow range. The calculated mass action concentrations of components in the NaCl-H2O and NaCl-KCl-H2O systems are in good agreement with the reported activities. This indicates that the developed thermodynamic model can reflect the structural characteristics of solutions,and the mass action concentration also strictly follows the mass action law.
2008, vol. 15, no. 5, pp.
552-555.
https://doi.org/10.1016/S1005-8850(08)60103-6
Abstract:
The fast cooling rate of thin ductile iron castings requires special consideration to produce carbide-free castings. Extraordinary care was taken to select the charge to produce castings of 100-mm long round bars with 16-mm diameter. The castings show the presence of carbides in the bars. Seven melts were made with different temperatures and with different compositions to get rid of carbides. After chemical analyses,it was found that the extra purity of the charge with less than 0.008wt% sulfur in the castings was the cause of carbides. To remove the carbides from the castings,sulfur should be added to the charge.
The fast cooling rate of thin ductile iron castings requires special consideration to produce carbide-free castings. Extraordinary care was taken to select the charge to produce castings of 100-mm long round bars with 16-mm diameter. The castings show the presence of carbides in the bars. Seven melts were made with different temperatures and with different compositions to get rid of carbides. After chemical analyses,it was found that the extra purity of the charge with less than 0.008wt% sulfur in the castings was the cause of carbides. To remove the carbides from the castings,sulfur should be added to the charge.
2008, vol. 15, no. 5, pp.
556-560.
https://doi.org/10.1016/S1005-8850(08)60104-8
Abstract:
The fine grained dual phase (FG-DP) steel with ferrite grains of 2-4.5 μm and martensite islands smaller than 3 μm was obtained through the mechanism of deformation-enhanced ferrite transformation (DEFT). Mechanical properties of the steel were tested at room temperature. The results indicated that with a similar volume fraction of martensite (about 20vol%),FG-DP steel exhibited a superior combination of higher strength and more rapid strain hardening at low strains compared with the coarse-grained dual phase (CG-DP) steel obtained by critical annealing. The combination of higher strength,large elongation,and more rapid strain hardening of FG-DP steel can be attributed to the fine ferrite grain and finely dispersed martensite islands. In addition,the uniformly distributed martensite islands in FG-DP steel have smaller interspacing compared with that of CG-DP steel. So,at the initial plastic deformation stage,the plastic deformation of ferrite was restrained and more pronounced load was transferred from ferrite to martensite. The plastic deformation of martensite in FG-DP steel started earlier.
The fine grained dual phase (FG-DP) steel with ferrite grains of 2-4.5 μm and martensite islands smaller than 3 μm was obtained through the mechanism of deformation-enhanced ferrite transformation (DEFT). Mechanical properties of the steel were tested at room temperature. The results indicated that with a similar volume fraction of martensite (about 20vol%),FG-DP steel exhibited a superior combination of higher strength and more rapid strain hardening at low strains compared with the coarse-grained dual phase (CG-DP) steel obtained by critical annealing. The combination of higher strength,large elongation,and more rapid strain hardening of FG-DP steel can be attributed to the fine ferrite grain and finely dispersed martensite islands. In addition,the uniformly distributed martensite islands in FG-DP steel have smaller interspacing compared with that of CG-DP steel. So,at the initial plastic deformation stage,the plastic deformation of ferrite was restrained and more pronounced load was transferred from ferrite to martensite. The plastic deformation of martensite in FG-DP steel started earlier.
2008, vol. 15, no. 5, pp.
561-567.
https://doi.org/10.1016/S1005-8850(08)60105-X
Abstract:
By means of supersonic fine particles bombarding (SFPB),a nanostructured surface layer up to 15 μm was fabricated on a 45 steel plate with ferrite and pearlite phases. To reveal the grain refinement mechanism of SFPB-treated 45 steel,microstructure features of various sections in the treated surface were systematically characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Grain size increases with an increase of depth from the treated surface. Plastic deformation and grain refinement processes are accompanied by an increase in strain. Plastic deformation in the proeutectoid ferrite phases has precedence over the pearlite phases. Grain refinement in the ferrite phases involves: the onset of dislocation lines (Dls),dislocation tangles (DTs) and dense dislocation walls (DDWs) in the original grains; the formation of fine lamellar and roughly equiaxed cells separated by DDWs; by dislocation annihilation and rearrangement,the transformation of DDWS into subboundaries and boundaries and the formation of submicron grains or subgrains; the successive subdivision of grains to finer and finer scale,resulting in the formation of highly misoriented nano-grains. By contrast,eutectoid cementite phase accommodated strain in a sequence as follows: onset of elongated,bended and shear deformation under deformation stress of ferrites,short and thin cementites with a width of about 20-50 nm and discontinuous length were formed. Shorter and thinner cementites were developed into ultra-fine pieces under the action of high density dislocation and strains. At the top surface,some cementites were decomposed under severe plastic deformation. Experimental evidences and analysis indicate that surface nanocrystallization of 45 steel results from dislocation activities,high strains and high strain rate are necessary for the formation of nanocrystallites.
By means of supersonic fine particles bombarding (SFPB),a nanostructured surface layer up to 15 μm was fabricated on a 45 steel plate with ferrite and pearlite phases. To reveal the grain refinement mechanism of SFPB-treated 45 steel,microstructure features of various sections in the treated surface were systematically characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Grain size increases with an increase of depth from the treated surface. Plastic deformation and grain refinement processes are accompanied by an increase in strain. Plastic deformation in the proeutectoid ferrite phases has precedence over the pearlite phases. Grain refinement in the ferrite phases involves: the onset of dislocation lines (Dls),dislocation tangles (DTs) and dense dislocation walls (DDWs) in the original grains; the formation of fine lamellar and roughly equiaxed cells separated by DDWs; by dislocation annihilation and rearrangement,the transformation of DDWS into subboundaries and boundaries and the formation of submicron grains or subgrains; the successive subdivision of grains to finer and finer scale,resulting in the formation of highly misoriented nano-grains. By contrast,eutectoid cementite phase accommodated strain in a sequence as follows: onset of elongated,bended and shear deformation under deformation stress of ferrites,short and thin cementites with a width of about 20-50 nm and discontinuous length were formed. Shorter and thinner cementites were developed into ultra-fine pieces under the action of high density dislocation and strains. At the top surface,some cementites were decomposed under severe plastic deformation. Experimental evidences and analysis indicate that surface nanocrystallization of 45 steel results from dislocation activities,high strains and high strain rate are necessary for the formation of nanocrystallites.
2008, vol. 15, no. 5, pp.
568-573.
https://doi.org/10.1016/S1005-8850(08)60106-1
Abstract:
By careful design of rolling schedule,ultra-fine (~2μm) ferrite grains in a low carbon high niobium (0.09wt%Nb) microalloying steel with average austenite grain sizes above 800 μm can be achieved in the simulated thin slab direct rolling process. The 5-pass deformation was divided into two stages: the refinement of austenite through complete recrystallization and the refinement of ferrite through dynamic strain-induced transformation. The effects of Nb in solution and strain-induced NbCN precipitates on the ferrite transformation were also extensively discussed.
By careful design of rolling schedule,ultra-fine (~2μm) ferrite grains in a low carbon high niobium (0.09wt%Nb) microalloying steel with average austenite grain sizes above 800 μm can be achieved in the simulated thin slab direct rolling process. The 5-pass deformation was divided into two stages: the refinement of austenite through complete recrystallization and the refinement of ferrite through dynamic strain-induced transformation. The effects of Nb in solution and strain-induced NbCN precipitates on the ferrite transformation were also extensively discussed.
2008, vol. 15, no. 5, pp.
574-579.
https://doi.org/10.1016/S1005-8850(08)60107-3
Abstract:
The mechanical properties of transformation induced plasticity (TRIP) steel are strongly affected by the conditions of iso-thermal bainitic processing. The multiphase microstructure of TRIP steel under different conditions of isothermal bainitic processing was investigated using OM,SEM,XRD and TEM. The volume fraction of retained austenite and the carbon content in austenite were determined quantitatively using X-ray diffraction patterns. The relationship between mechanical properties and isothermal bainitic processing parameters was investigated. The stability of retained austenite was analyzed by the volume fraction of retained austenite and the carbon content in retained austenite. The experimental results show that the multiphase microstructure consists of ferrite,bainite and metastable retained austenite.To obtain good mechanical properties,the optimal conditions of isothermal bainitic temperature and holding time are 410-430℃ and 180-240 s,respectively. After isothermal bainitic processing under the optimal conditions,the corresponding volume fraction of retained austenite is 5vol%-15vol%,which can provide enough retained austenite and plastic stability for austenite with high carbon content.
The mechanical properties of transformation induced plasticity (TRIP) steel are strongly affected by the conditions of iso-thermal bainitic processing. The multiphase microstructure of TRIP steel under different conditions of isothermal bainitic processing was investigated using OM,SEM,XRD and TEM. The volume fraction of retained austenite and the carbon content in austenite were determined quantitatively using X-ray diffraction patterns. The relationship between mechanical properties and isothermal bainitic processing parameters was investigated. The stability of retained austenite was analyzed by the volume fraction of retained austenite and the carbon content in retained austenite. The experimental results show that the multiphase microstructure consists of ferrite,bainite and metastable retained austenite.To obtain good mechanical properties,the optimal conditions of isothermal bainitic temperature and holding time are 410-430℃ and 180-240 s,respectively. After isothermal bainitic processing under the optimal conditions,the corresponding volume fraction of retained austenite is 5vol%-15vol%,which can provide enough retained austenite and plastic stability for austenite with high carbon content.
2008, vol. 15, no. 5, pp.
580-584.
https://doi.org/10.1016/S1005-8850(08)60108-5
Abstract:
To investigate the influence of stress alone on the stray field signals of ferromagnetic materials,the static tensile tests of 0.45%C steel and 45CrNiMoVA steel flat-shaped specimens were performed on an MTS810 hydraulic testing machine. Hp(y) signals,the normal component of spontaneous stray field,were measured during the testing process by an EMS-2003 metal magnetic memory diagnostic apparatus cooperated with a non-magnetic electric control displacement instrument. Fracture and microstructure were observed by a scanning electronic microscope and a transmission electron microscope,respectively. The relationships between axial applied stress or residual stress measured by X-ray diffraction method and Hp(y) were analyzed. The results indicate that some regular pattern of the magnetic curve is displayed only between applied stress and stray field signals. The magnetic ordering process stops due to dislocation pinning magnetic domain structure,and Hp(y) value unvaried nearly with applied load increasing in the plastic deformation stage.
To investigate the influence of stress alone on the stray field signals of ferromagnetic materials,the static tensile tests of 0.45%C steel and 45CrNiMoVA steel flat-shaped specimens were performed on an MTS810 hydraulic testing machine. Hp(y) signals,the normal component of spontaneous stray field,were measured during the testing process by an EMS-2003 metal magnetic memory diagnostic apparatus cooperated with a non-magnetic electric control displacement instrument. Fracture and microstructure were observed by a scanning electronic microscope and a transmission electron microscope,respectively. The relationships between axial applied stress or residual stress measured by X-ray diffraction method and Hp(y) were analyzed. The results indicate that some regular pattern of the magnetic curve is displayed only between applied stress and stray field signals. The magnetic ordering process stops due to dislocation pinning magnetic domain structure,and Hp(y) value unvaried nearly with applied load increasing in the plastic deformation stage.
2008, vol. 15, no. 5, pp.
585-589.
https://doi.org/10.1016/S1005-8850(08)60109-7
Abstract:
The fatigue crack propagation behavior of the LY12CZ aluminum alloy fastener involving a central hole in air or in 3.5wt% NaCl solution was investigated. The experimental results indicated that the corrosion fatigue crack growth rate decreased with the increasing loading frequency,and in a corrosive environment,the crack growth rate was slightly larger than that in air. Based on the experimental results,the virtual corrosion fatigue crack propagation tests were investigated and the stochastic process method and the AFGROW simulation method were presented. The normal process and lognormal process were considered for the stochastic process method based on the numerically fitted Paris equation. The distribution of crack size and the corresponding probabilistic model of crack length distribution for a given number of cycles can be found by integrating the stochastic process over time. Using the AFGROW software,the virtual simulation was carried out to analyze the corrosion fatigue crack growth behavior and the predicted crack growth curve was in good agreement with the experimental results.
The fatigue crack propagation behavior of the LY12CZ aluminum alloy fastener involving a central hole in air or in 3.5wt% NaCl solution was investigated. The experimental results indicated that the corrosion fatigue crack growth rate decreased with the increasing loading frequency,and in a corrosive environment,the crack growth rate was slightly larger than that in air. Based on the experimental results,the virtual corrosion fatigue crack propagation tests were investigated and the stochastic process method and the AFGROW simulation method were presented. The normal process and lognormal process were considered for the stochastic process method based on the numerically fitted Paris equation. The distribution of crack size and the corresponding probabilistic model of crack length distribution for a given number of cycles can be found by integrating the stochastic process over time. Using the AFGROW software,the virtual simulation was carried out to analyze the corrosion fatigue crack growth behavior and the predicted crack growth curve was in good agreement with the experimental results.
2008, vol. 15, no. 5, pp.
590-593.
https://doi.org/10.1016/S1005-8850(08)60110-3
Abstract:
Plasma surface alloying of element Nb in TiAl-based alloys and the oxidation behavior were studied. The composition and microstructure of the surface alloyed layers were investigated by means of scanning electron microscopy (SEM),energy dispersive X-ray analysis (EDX),and X-ray diffraction (XRD). The experimental results indicate that the diffusion layers are formed on the TiAl substrate during the plasma niobizing process. The result from oxidation resistance investigation shows that plasma niobizing greatly improves the oxidation resistance of TiAl compared with the untreated TiAl. The role of element Nb for improving the oxidation resistance is considered to be achieved by strengthening the activity of Al,which is induced by the plasma niobizing process.
Plasma surface alloying of element Nb in TiAl-based alloys and the oxidation behavior were studied. The composition and microstructure of the surface alloyed layers were investigated by means of scanning electron microscopy (SEM),energy dispersive X-ray analysis (EDX),and X-ray diffraction (XRD). The experimental results indicate that the diffusion layers are formed on the TiAl substrate during the plasma niobizing process. The result from oxidation resistance investigation shows that plasma niobizing greatly improves the oxidation resistance of TiAl compared with the untreated TiAl. The role of element Nb for improving the oxidation resistance is considered to be achieved by strengthening the activity of Al,which is induced by the plasma niobizing process.
2008, vol. 15, no. 5, pp.
594-599.
https://doi.org/10.1016/S1005-8850(08)60111-5
Abstract:
The microstructure and composition of the residual liquid at different temperatures were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDX) associated with the Thermo-calc software calculation of the equilibrium phase diagrams of Inconel 718 and segregated liquid. The liquid density difference and Rayleigh number variation during solidification were estimated as well. It is found that the heavy segregation of Nb in liquid prompts the precipitation of δ and Laves phase directly from liquid and the resultant quenched liquid microstructure consists of pro-eutectic γ+eutectic,or complete eutectic according to the content of Nb from low to high. The liquid density increases with decreasing temperature during the solidification of Inconel 718 and the liquid density difference is positive. The largest relative Rayleigh number occurs at 1320℃ when the liquid fraction is about 40vol%.
The microstructure and composition of the residual liquid at different temperatures were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDX) associated with the Thermo-calc software calculation of the equilibrium phase diagrams of Inconel 718 and segregated liquid. The liquid density difference and Rayleigh number variation during solidification were estimated as well. It is found that the heavy segregation of Nb in liquid prompts the precipitation of δ and Laves phase directly from liquid and the resultant quenched liquid microstructure consists of pro-eutectic γ+eutectic,or complete eutectic according to the content of Nb from low to high. The liquid density increases with decreasing temperature during the solidification of Inconel 718 and the liquid density difference is positive. The largest relative Rayleigh number occurs at 1320℃ when the liquid fraction is about 40vol%.
2008, vol. 15, no. 5, pp.
600-604.
https://doi.org/10.1016/S1005-8850(08)60112-7
Abstract:
The effects of high magnetic field on the crystallization behavior of the Fe78Si13B9 metallic glass ribbon were studied. The samples were isothermal annealed for 30 min under high magnetic field and no field,respectively. Microstructure transformation during crystallization was identified by X-ray diffraction and transmission electron microscopy. It was found that the crystallizations of Fe78Si13B9 metallic glass processed under different conditions were that the precipitation of dendrite α-Fe(Si) and spherulite (Fe,Si)3B phases forms amorphous matrix and then the metastable (Fe,Si)3B phase transforms into the stable Fe2B phase. The grain size of the crystals is smaller and more homogeneous for the isothermal annealed samples under high magnetic field in comparison with that under no field indicating that the crystallization behavior of Fe78Si13B9 metallic glass is suppressed by high magnetic field.
The effects of high magnetic field on the crystallization behavior of the Fe78Si13B9 metallic glass ribbon were studied. The samples were isothermal annealed for 30 min under high magnetic field and no field,respectively. Microstructure transformation during crystallization was identified by X-ray diffraction and transmission electron microscopy. It was found that the crystallizations of Fe78Si13B9 metallic glass processed under different conditions were that the precipitation of dendrite α-Fe(Si) and spherulite (Fe,Si)3B phases forms amorphous matrix and then the metastable (Fe,Si)3B phase transforms into the stable Fe2B phase. The grain size of the crystals is smaller and more homogeneous for the isothermal annealed samples under high magnetic field in comparison with that under no field indicating that the crystallization behavior of Fe78Si13B9 metallic glass is suppressed by high magnetic field.
2008, vol. 15, no. 5, pp.
605-610.
https://doi.org/10.1016/S1005-8850(08)60113-9
Abstract:
A new method was reported for surface modification of an up-conversion luminescence material with hydrosulfide group. The factors that may influence the surface modification,such as reaction time,amount of catalyzer and modifier,and reaction solvent,were investigated. The optimal conditions were that the reaction time,the quantity of the basic catalyzer,the quantity of modifier and the volume of reaction solvent were 40 min,1.0,1.0,and 40 mL,respectively. The results indicated that hydrosulfide group content modified on the surface of up-conversion luminescence material reached to 0.1430 mmol/g,and this modified up-conversion luminescence material could be widely used in the study of structure of protein and the property of microenvironment.
A new method was reported for surface modification of an up-conversion luminescence material with hydrosulfide group. The factors that may influence the surface modification,such as reaction time,amount of catalyzer and modifier,and reaction solvent,were investigated. The optimal conditions were that the reaction time,the quantity of the basic catalyzer,the quantity of modifier and the volume of reaction solvent were 40 min,1.0,1.0,and 40 mL,respectively. The results indicated that hydrosulfide group content modified on the surface of up-conversion luminescence material reached to 0.1430 mmol/g,and this modified up-conversion luminescence material could be widely used in the study of structure of protein and the property of microenvironment.
2008, vol. 15, no. 5, pp.
611-617.
https://doi.org/10.1016/S1005-8850(08)60114-0
Abstract:
Cobalt-molybdenum (Co-Mo) amorphous alloy thin films were deposited on copper substrates by the electrochemical method at pH 4.0. Among the experimental electrodeposition parameters,only the concentration ratio of molybdate to cobalt ions ([MoO42-]/[Co2+]) was varied to analyze its influence on the mechanism of induced cobalt-molybdenum codeposition. Voltammetry was one of the main techniques,which was used to examine the voltammetric response,revealing that cobalt-molybdenum codeposition depended on the nature of the species in solution. To correlate the type of the film to the electrochemical response,various cobalt-molybdenum alloy thin films obtained from different [MoO42-]/[Co2+] solutions were tested. Crack-free homogeneous films could be easily obtained from the low molybdate concentrations ([MoO42-]/[Co2+]≈0.05) applying low deposition potentials. Moreover,the content of molybdenum up to 30wt% could be obtained from high molybdate concentration; in this case,the films showed cracks. The formation of these cracked films could be predicted from the observed distortions in the curves of electric current-time (j-t) deposition transients. The films with amorphous structure were obtained. The hysteresis loops suggested that the easily magnetized axis was parallel to the surface of the films. A saturation magnetization of 137 emu·g-1 and a coercivity of 87 Oe of the film were obtained when the deposition potential was -1025mV,and [ MoO42-]/[Co2+] was 0.05 in solution,which exhibited a nicer soft-magnetic response.
Cobalt-molybdenum (Co-Mo) amorphous alloy thin films were deposited on copper substrates by the electrochemical method at pH 4.0. Among the experimental electrodeposition parameters,only the concentration ratio of molybdate to cobalt ions ([MoO42-]/[Co2+]) was varied to analyze its influence on the mechanism of induced cobalt-molybdenum codeposition. Voltammetry was one of the main techniques,which was used to examine the voltammetric response,revealing that cobalt-molybdenum codeposition depended on the nature of the species in solution. To correlate the type of the film to the electrochemical response,various cobalt-molybdenum alloy thin films obtained from different [MoO42-]/[Co2+] solutions were tested. Crack-free homogeneous films could be easily obtained from the low molybdate concentrations ([MoO42-]/[Co2+]≈0.05) applying low deposition potentials. Moreover,the content of molybdenum up to 30wt% could be obtained from high molybdate concentration; in this case,the films showed cracks. The formation of these cracked films could be predicted from the observed distortions in the curves of electric current-time (j-t) deposition transients. The films with amorphous structure were obtained. The hysteresis loops suggested that the easily magnetized axis was parallel to the surface of the films. A saturation magnetization of 137 emu·g-1 and a coercivity of 87 Oe of the film were obtained when the deposition potential was -1025mV,and [ MoO42-]/[Co2+] was 0.05 in solution,which exhibited a nicer soft-magnetic response.
2008, vol. 15, no. 5, pp.
618-621.
https://doi.org/10.1016/S1005-8850(08)60115-2
Abstract:
Magnetic Co-P thin films were prepared by electroless deposition. The experiment results show that the film thickness has a significant influence on the coercivity. While the film thickness varied from 300 nm to 5 μm,the coercivity dropped sharply from 45.36 to 22.28 kA/m. As the film thickness increased further,the coercivity varied slowly. When the thickness of the film was 300 nm,the deposited film could realize the coercivity as high as 45.36 kA/m,and the remanent magnetization as high as 800 kA/m.The Co-P films were deposited on the surface of magnetic drums of encoders,whose diameter was 40 mm,and then 512 magnetic poles were recorded,meaning that the magnetizing pitch was 0.245 mm. The testing results indicate that the output signals are perfect,the output waveforms are steady and the pulses account is integral. Compared with the γ-Fe2O3 coating,the Co-P thin film is suitable to be the magnetic recording media for the high resolution magnetic rotary encoder.
Magnetic Co-P thin films were prepared by electroless deposition. The experiment results show that the film thickness has a significant influence on the coercivity. While the film thickness varied from 300 nm to 5 μm,the coercivity dropped sharply from 45.36 to 22.28 kA/m. As the film thickness increased further,the coercivity varied slowly. When the thickness of the film was 300 nm,the deposited film could realize the coercivity as high as 45.36 kA/m,and the remanent magnetization as high as 800 kA/m.The Co-P films were deposited on the surface of magnetic drums of encoders,whose diameter was 40 mm,and then 512 magnetic poles were recorded,meaning that the magnetizing pitch was 0.245 mm. The testing results indicate that the output signals are perfect,the output waveforms are steady and the pulses account is integral. Compared with the γ-Fe2O3 coating,the Co-P thin film is suitable to be the magnetic recording media for the high resolution magnetic rotary encoder.
2008, vol. 15, no. 5, pp.
622-626.
https://doi.org/10.1016/S1005-8850(08)60116-4
Abstract:
Direct current metal filtered cathodic vacuum arc (FCVA) and acetylene gas (C2H2) were wielded to synthesize Ti-containing amorphous carbon films on Si (100). The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the (111) preferential crystallographic orientation exists in the film,and the main existing pattern of carbon is sp2. With increasing the acetylene flow rate,the contents of Ti and TiC phase of the film gradually reduce; however,the thickness of the film increases. When the substrate bias voltage reaches -600 V,the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa,respectively,and the friction coefficient of the film is 0.25.
Direct current metal filtered cathodic vacuum arc (FCVA) and acetylene gas (C2H2) were wielded to synthesize Ti-containing amorphous carbon films on Si (100). The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the (111) preferential crystallographic orientation exists in the film,and the main existing pattern of carbon is sp2. With increasing the acetylene flow rate,the contents of Ti and TiC phase of the film gradually reduce; however,the thickness of the film increases. When the substrate bias voltage reaches -600 V,the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa,respectively,and the friction coefficient of the film is 0.25.
2008, vol. 15, no. 5, pp.
627-632.
https://doi.org/10.1016/S1005-8850(08)60117-6
Abstract:
A new coating on lining in industrial furnace for energy saving has been developed. Properties and microstructure of the coatings were revealed by emissivity instrument,X-ray diffraction (XRD),transmission electron microscope (TEM) and scanning electron microscope (SEM),respectively. The result indicates that the emissivity of coatings is higher than 0.90 and the thickness of coatings is about 200 μm. ZrO2,Cr2O3 and SiC in the coating benefit practical applications of coatings at high temperature with durable high emissivity and the continuous structure between the coatings and the substrate makes the coatings high cohesion and excellent adhesion for both specimens with and without sintering at high temperature. Result from laboratory experiment shows that the heating speed of specimen with coating is higher than that of controlled specimen and the temperature increases 30℃ during the heating. The average temperature drop of specimen with coatings has a 13.5% improvement in the cooling speed. The application of coatings on the checker brick in a blast furnace of 1750m3 indicates that the coating causes the blast temperature to an average increase of 28℃,reduces the fluctuation of blast temperature before the blowing-in and leads to a fuel saving of 10% approximately.
A new coating on lining in industrial furnace for energy saving has been developed. Properties and microstructure of the coatings were revealed by emissivity instrument,X-ray diffraction (XRD),transmission electron microscope (TEM) and scanning electron microscope (SEM),respectively. The result indicates that the emissivity of coatings is higher than 0.90 and the thickness of coatings is about 200 μm. ZrO2,Cr2O3 and SiC in the coating benefit practical applications of coatings at high temperature with durable high emissivity and the continuous structure between the coatings and the substrate makes the coatings high cohesion and excellent adhesion for both specimens with and without sintering at high temperature. Result from laboratory experiment shows that the heating speed of specimen with coating is higher than that of controlled specimen and the temperature increases 30℃ during the heating. The average temperature drop of specimen with coatings has a 13.5% improvement in the cooling speed. The application of coatings on the checker brick in a blast furnace of 1750m3 indicates that the coating causes the blast temperature to an average increase of 28℃,reduces the fluctuation of blast temperature before the blowing-in and leads to a fuel saving of 10% approximately.
2008, vol. 15, no. 5, pp.
633-637.
https://doi.org/10.1016/S1005-8850(08)60118-8
Abstract:
Metal and nano-ceramic nanocomposite coatings were prepared on the gray cast iron surface by the electrodeposition method. The Ni-Co was used as the metal matrix,and nano-Al2O3 was chosen as the second-phase particulates. To avoid poor inter-face bonding and stress distribution,the gradient structure of biology materials was found as the model and therefore the gradient composite coating was prepared. The morphology of the composite coatings was flatter and the microstructure was denser than that of pure Ni-Co coatings. The composite coatings were prepared by different current densities,and the 2-D and 3-D morphologies of the surface coatings were observed. The result indicated that the 2-D structure became rougher and the 3-D surface density of apices became less when the current density was increased. The content of nanoparticulates reached a maximum value at the current density of 40mA·cm-2,at the same time the properties including microhardness and wear-resistance were analyzed. The microhardness reached a maximum value and the wear volume was also less at the current density of 40mA·cm-2. The reason was that nano-Al2O3 particles caused dispersive strengthening and grain refining.
Metal and nano-ceramic nanocomposite coatings were prepared on the gray cast iron surface by the electrodeposition method. The Ni-Co was used as the metal matrix,and nano-Al2O3 was chosen as the second-phase particulates. To avoid poor inter-face bonding and stress distribution,the gradient structure of biology materials was found as the model and therefore the gradient composite coating was prepared. The morphology of the composite coatings was flatter and the microstructure was denser than that of pure Ni-Co coatings. The composite coatings were prepared by different current densities,and the 2-D and 3-D morphologies of the surface coatings were observed. The result indicated that the 2-D structure became rougher and the 3-D surface density of apices became less when the current density was increased. The content of nanoparticulates reached a maximum value at the current density of 40mA·cm-2,at the same time the properties including microhardness and wear-resistance were analyzed. The microhardness reached a maximum value and the wear volume was also less at the current density of 40mA·cm-2. The reason was that nano-Al2O3 particles caused dispersive strengthening and grain refining.
2008, vol. 15, no. 5, pp.
638-643.
https://doi.org/10.1016/S1005-8850(08)60119-X
Abstract:
The spin transport property of a ferromagnet (FM)/insulator (Ⅰ)/resonant tunneling diode (RTD) heterostructure was studied. The transmission coefficient and spin polarization in a multilayered heterostructure was calculated by a Schrödinger wave equation. An Airy function formalism approach was used to solve this equation. Based on the transfer matrix approach,the transmittivity of the structure was determined as a function of the Feimi energy and other parameters. The result shows that the spin polarization induced by the structure oscillates with the increasing Fermi energy of the FM layer. While the thickness of the RTD is reduced,the resonant peaks become broad. In the heterostructure,the spin polarization reaches as high as 40% and can be easily controlled by the external bias voltage.
The spin transport property of a ferromagnet (FM)/insulator (Ⅰ)/resonant tunneling diode (RTD) heterostructure was studied. The transmission coefficient and spin polarization in a multilayered heterostructure was calculated by a Schrödinger wave equation. An Airy function formalism approach was used to solve this equation. Based on the transfer matrix approach,the transmittivity of the structure was determined as a function of the Feimi energy and other parameters. The result shows that the spin polarization induced by the structure oscillates with the increasing Fermi energy of the FM layer. While the thickness of the RTD is reduced,the resonant peaks become broad. In the heterostructure,the spin polarization reaches as high as 40% and can be easily controlled by the external bias voltage.
2008, vol. 15, no. 5, pp.
644-648.
https://doi.org/10.1016/S1005-8850(08)60120-6
Abstract:
Pure titanate nanotubes and titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions were synthesized by the hydrothermal method. In this process,titanate nanotubes were first prepared synchronously with doping Fe3+/Ni2+/Mn2+ ions. The morphology,structure,thermal stability and magnetic property of titanate nanotubes were characterized by X-ray diffraction (XRD),transmission electron microscope (TEM),and magnetic measurement. The titanate nanotubes transformed into the anatase titania nanocrystals,and further the mixture of anatase and rutile titania along with increasing temperature. The results indicate that the titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions are paramagnetic behaviors.
Pure titanate nanotubes and titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions were synthesized by the hydrothermal method. In this process,titanate nanotubes were first prepared synchronously with doping Fe3+/Ni2+/Mn2+ ions. The morphology,structure,thermal stability and magnetic property of titanate nanotubes were characterized by X-ray diffraction (XRD),transmission electron microscope (TEM),and magnetic measurement. The titanate nanotubes transformed into the anatase titania nanocrystals,and further the mixture of anatase and rutile titania along with increasing temperature. The results indicate that the titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions are paramagnetic behaviors.
2008, vol. 15, no. 5, pp.
649-653.
https://doi.org/10.1016/S1005-8850(08)60121-8
Abstract:
In an effort to incorporate the low thermal conductivity of the silica aerogel and the superior structure strength of the xonotlite,a composite material of these two was produced. It was synthesized under vacuum condition and dried by supercritical drying technique. The thermal conductivity of the new material,which is at 298K with the gas pressure ranging from 1.01×105 to 1×10-2 Pa,was measured using the transient hot-strip method. The mechanism of the low thermal conductivity was studied. The results indicate that the low thermal conductivity mainly results from the significant decrease of gaseous thermal conductivity of the new material due to the restriction of the motion of gas molecules in its fine structures. The formation of the fine structures is because the new material takes the pore structure of the silica aerogel which consists of mainly nanometer-sized pores.
In an effort to incorporate the low thermal conductivity of the silica aerogel and the superior structure strength of the xonotlite,a composite material of these two was produced. It was synthesized under vacuum condition and dried by supercritical drying technique. The thermal conductivity of the new material,which is at 298K with the gas pressure ranging from 1.01×105 to 1×10-2 Pa,was measured using the transient hot-strip method. The mechanism of the low thermal conductivity was studied. The results indicate that the low thermal conductivity mainly results from the significant decrease of gaseous thermal conductivity of the new material due to the restriction of the motion of gas molecules in its fine structures. The formation of the fine structures is because the new material takes the pore structure of the silica aerogel which consists of mainly nanometer-sized pores.
2008, vol. 15, no. 5, pp.
654-658.
https://doi.org/10.1016/S1005-8850(08)60122-X
Abstract:
Micropipe and step structures on 6H-SiC (0001) surface were investigated by an atomic force microscopy (AFM). On the facet,all micropipes examined are the origins of spiral steps,indicating that dislocations intersect the surface at these points. Micropipes are empty-core super-dislocations as originally described by Frank. The micropipe radius increases with the square of the dislocation Burgers vector. From the center to the periphery,step structures change with different surface inclinations. Regular step is observed within the central faceted area. Step bunching and atomically rough surfaces are observed within the peripheral convex area. If the inclination with respect to the (0001) plane is large enough,step bunching of 15R-SiC can be observed.
Micropipe and step structures on 6H-SiC (0001) surface were investigated by an atomic force microscopy (AFM). On the facet,all micropipes examined are the origins of spiral steps,indicating that dislocations intersect the surface at these points. Micropipes are empty-core super-dislocations as originally described by Frank. The micropipe radius increases with the square of the dislocation Burgers vector. From the center to the periphery,step structures change with different surface inclinations. Regular step is observed within the central faceted area. Step bunching and atomically rough surfaces are observed within the peripheral convex area. If the inclination with respect to the (0001) plane is large enough,step bunching of 15R-SiC can be observed.
2008, vol. 15, no. 5, pp.
659-664.
https://doi.org/10.1016/S1005-8850(08)60123-1
Abstract:
Submicron copper microcrystal was synthesized by reducing Cu2O with hydrazine hydrate as reducer in aqueous solution,and was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The shapes of copper microcrystal depend on additives. Cubic copper particles were observed when the inorganic salt containing Cl-,such as NH4Cl,NaCl,or KCl,was added into the reaction system. By combined use of NH4Cl and polyvinylpyrrolidone (PVP),the proportion of cubic copper particle number exceeded 90%,and the particle size is 0.1-0.5μrn. While other inorganic salt without Cl-,such as Na2SO4 or (NH4)2SO4,had little effect on the shapes of the copper particles. The growth mechanism of metallic copper crystal in aqueous solution was analyzed. It is suggested that the formation of cubic copper crystals is ascribed to the selective adsorption of Cl- on copper crystal (100) faces.
Submicron copper microcrystal was synthesized by reducing Cu2O with hydrazine hydrate as reducer in aqueous solution,and was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The shapes of copper microcrystal depend on additives. Cubic copper particles were observed when the inorganic salt containing Cl-,such as NH4Cl,NaCl,or KCl,was added into the reaction system. By combined use of NH4Cl and polyvinylpyrrolidone (PVP),the proportion of cubic copper particle number exceeded 90%,and the particle size is 0.1-0.5μrn. While other inorganic salt without Cl-,such as Na2SO4 or (NH4)2SO4,had little effect on the shapes of the copper particles. The growth mechanism of metallic copper crystal in aqueous solution was analyzed. It is suggested that the formation of cubic copper crystals is ascribed to the selective adsorption of Cl- on copper crystal (100) faces.
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