Search2008 Vol. 15, No. 4
Display Method:
2008, vol. 15, no. 4, pp.
367-374.
https://doi.org/10.1016/S1005-8850(08)60070-5
Abstract:
The assay and recovery of rare earth elements (REEs) in the leaching process is being determined using expensive analytical methods: inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectroscopy (ICP-MS). A neural network model to predict the effects of operational variables on the lanthanum, cerium, yttrium, and neodymium recovery in the leaching of apatite concentrate is presented in this article. The effects of leaching time (10 to 40 min), pulp densities (30% to 50%), acid concentrations (20% to 60%), and agitation rates (100 to 200 r/min), were investigated and optimized on the recovery of REEs in the laboratory at a leaching temperature of 60℃. The obtained data in the laboratory optimization process were used for training and testing the neural network. The feed-forward artificial neural network with a 4-5-5-1 arrangement was capable of estimating the leaching recovery of REEs. The neural network predicted values were in good agreement with the experimental results. The correlations of R=l in training stages, and R=0.971, 0.952, 0.985, and 0.98 in testing stages were a result of Ce, Nd, La, and Y recovery prediction respectively, and these values were usually acceptable. It was shown that the proposed neural network model accurately reproduced all the effects of the operation variables, and could be used in the simulation of a leaching plant for REEs.
The assay and recovery of rare earth elements (REEs) in the leaching process is being determined using expensive analytical methods: inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectroscopy (ICP-MS). A neural network model to predict the effects of operational variables on the lanthanum, cerium, yttrium, and neodymium recovery in the leaching of apatite concentrate is presented in this article. The effects of leaching time (10 to 40 min), pulp densities (30% to 50%), acid concentrations (20% to 60%), and agitation rates (100 to 200 r/min), were investigated and optimized on the recovery of REEs in the laboratory at a leaching temperature of 60℃. The obtained data in the laboratory optimization process were used for training and testing the neural network. The feed-forward artificial neural network with a 4-5-5-1 arrangement was capable of estimating the leaching recovery of REEs. The neural network predicted values were in good agreement with the experimental results. The correlations of R=l in training stages, and R=0.971, 0.952, 0.985, and 0.98 in testing stages were a result of Ce, Nd, La, and Y recovery prediction respectively, and these values were usually acceptable. It was shown that the proposed neural network model accurately reproduced all the effects of the operation variables, and could be used in the simulation of a leaching plant for REEs.
2008, vol. 15, no. 4, pp.
375-378.
https://doi.org/10.1016/S1005-8850(08)60071-7
Abstract:
To obtain a better desulphurization effect in hot metal, suitable desulfurizers should be selected first according to thermodynamics. However, the effect of desulphurization is also strongly affected by kinetics. The conditions of different desulfurizers (Mg, CaC2, and lime) penetrating into hot metal, the rising up velocity in iron melt, residence time, and dissolving time are theoretically calculated and analyzed. The results are helpful to select the desulphurization process and equipment and to improve the desulphurization effect.
To obtain a better desulphurization effect in hot metal, suitable desulfurizers should be selected first according to thermodynamics. However, the effect of desulphurization is also strongly affected by kinetics. The conditions of different desulfurizers (Mg, CaC2, and lime) penetrating into hot metal, the rising up velocity in iron melt, residence time, and dissolving time are theoretically calculated and analyzed. The results are helpful to select the desulphurization process and equipment and to improve the desulphurization effect.
2008, vol. 15, no. 4, pp.
379-384.
https://doi.org/10.1016/S1005-8850(08)60072-9
Abstract:
Considering the characteristic of selective heating of microwave and the treatment of titania-bearing BF slag, a mathematical model for the heating of a slag specimen is developed. The temperature distribution in the specimen is studied by numerical simulation. The temperature in the center of the cylindrical slag specimen is the highest and the temperature decreases when the radius increases rapidly. In this case, the temperature rising rate decreases with heating time rapidly, and it tends to zero when the heating time is up to 150 s.
Considering the characteristic of selective heating of microwave and the treatment of titania-bearing BF slag, a mathematical model for the heating of a slag specimen is developed. The temperature distribution in the specimen is studied by numerical simulation. The temperature in the center of the cylindrical slag specimen is the highest and the temperature decreases when the radius increases rapidly. In this case, the temperature rising rate decreases with heating time rapidly, and it tends to zero when the heating time is up to 150 s.
2008, vol. 15, no. 4, pp.
385-388.
https://doi.org/10.1016/S1005-8850(08)60073-0
Abstract:
A similarity analysis for Marangoni convection induced flow over a vapor-liquid interface due to an imposed temperature gradient was carried out. The analysis assumes that the surface tension varies linearly with temperature but the temperature variation is a power law function of the location. The similarity solutions are presented numerically and the associated transfer characteristics are discussed.
A similarity analysis for Marangoni convection induced flow over a vapor-liquid interface due to an imposed temperature gradient was carried out. The analysis assumes that the surface tension varies linearly with temperature but the temperature variation is a power law function of the location. The similarity solutions are presented numerically and the associated transfer characteristics are discussed.
2008, vol. 15, no. 4, pp.
389-395.
https://doi.org/10.1016/S1005-8850(08)60074-2
Abstract:
Transmission electron microscopy (TEM) and physics-chemical phase analysis were employed to investigate the precipitates in high strength steels microalloyed with Ti produced by compact strip production (CSP). It was seen that precipitates in Ti microalloyed steels mainly included TiN, Ti4C2S2, and TiC. The size of TiN particles varied from 50 to 500 nm, and they could precipitate during or before soaking. The Ti4C2S2 with the size of 40-100 nm might precipitate before rolling, and the TiC particles with the size of 5-50 nm precipitated heterogeneously. High Ti content would lead to the presence of bigger TiC particles that precipitated in austenite, and by contrast, TiC particles that precipitated in ferrite and the transformation of austenite to ferrite was smaller. They were less than 30 nm and mainly responsible for precipitate strengthening. It should be noted that the TiC particles in higher Ti content were generally smaller than those in the steel with a lower Ti content.
Transmission electron microscopy (TEM) and physics-chemical phase analysis were employed to investigate the precipitates in high strength steels microalloyed with Ti produced by compact strip production (CSP). It was seen that precipitates in Ti microalloyed steels mainly included TiN, Ti4C2S2, and TiC. The size of TiN particles varied from 50 to 500 nm, and they could precipitate during or before soaking. The Ti4C2S2 with the size of 40-100 nm might precipitate before rolling, and the TiC particles with the size of 5-50 nm precipitated heterogeneously. High Ti content would lead to the presence of bigger TiC particles that precipitated in austenite, and by contrast, TiC particles that precipitated in ferrite and the transformation of austenite to ferrite was smaller. They were less than 30 nm and mainly responsible for precipitate strengthening. It should be noted that the TiC particles in higher Ti content were generally smaller than those in the steel with a lower Ti content.
Modeling of microstructure evolution and mechanical properties during hot-strip rolling of Nb steels
2008, vol. 15, no. 4, pp.
396-401.
https://doi.org/10.1016/S1005-8850(08)60075-4
Abstract:
An integrated metallurgical model was developed for Nb steels to predict the microstructure evolution and mechanical properties during the hot-strip rolling and cooling process. On the basis of the industrial data, the transformation kinetics, strength, and elongation rate were evaluated for different chemical compositions and processing parameters. The yield strength and tensile strength increase with increasing Nb content or decreasing finishing temperature. The bainite distributed in finer ferrite matrix, which is produced at relatively low coiling temperatures, can greatly increase the strength of steel, especially tensile strength, thereby decreasing the yield ratio. A reasonable agreement was found between the predicted and measured results. It indicates that the present models can be used to simulate the actual production process.
An integrated metallurgical model was developed for Nb steels to predict the microstructure evolution and mechanical properties during the hot-strip rolling and cooling process. On the basis of the industrial data, the transformation kinetics, strength, and elongation rate were evaluated for different chemical compositions and processing parameters. The yield strength and tensile strength increase with increasing Nb content or decreasing finishing temperature. The bainite distributed in finer ferrite matrix, which is produced at relatively low coiling temperatures, can greatly increase the strength of steel, especially tensile strength, thereby decreasing the yield ratio. A reasonable agreement was found between the predicted and measured results. It indicates that the present models can be used to simulate the actual production process.
2008, vol. 15, no. 4, pp.
402-406.
https://doi.org/10.1016/S1005-8850(08)60076-6
Abstract:
The scratch behaviors of two high speed steels (HSS) for hot rolls were studied by a Micro-combi Tester, and the emphasis was placed on researching the relations between the microstructure and the scratch resistance property of different HSS. The experimental results indicate that during the scratch process, the carbides are embedded into the matrix, the penetration depth of different HSS is closely related with the matrix hardness, i.e., the higher the matrix hardness, the better the scratch resistance property; and in the matrix, the fine, dispersive carbides are beneficial to form steady friction between the indenter and the scratched materials, but the coarser carbides are easier to fall into pieces.
The scratch behaviors of two high speed steels (HSS) for hot rolls were studied by a Micro-combi Tester, and the emphasis was placed on researching the relations between the microstructure and the scratch resistance property of different HSS. The experimental results indicate that during the scratch process, the carbides are embedded into the matrix, the penetration depth of different HSS is closely related with the matrix hardness, i.e., the higher the matrix hardness, the better the scratch resistance property; and in the matrix, the fine, dispersive carbides are beneficial to form steady friction between the indenter and the scratched materials, but the coarser carbides are easier to fall into pieces.
2008, vol. 15, no. 4, pp.
407-411.
https://doi.org/10.1016/S1005-8850(08)60077-8
Abstract:
The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.
The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.
2008, vol. 15, no. 4, pp.
412-419.
https://doi.org/10.1016/S1005-8850(08)60078-X
Abstract:
Two thermomechanical coupled elastic-plastic finite element (FE) models were developed for predicting the 12-pass continuous rolling process of GCrl 5 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by interpolation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.
Two thermomechanical coupled elastic-plastic finite element (FE) models were developed for predicting the 12-pass continuous rolling process of GCrl 5 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by interpolation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.
2008, vol. 15, no. 4, pp.
420-424.
https://doi.org/10.1016/S1005-8850(08)60079-1
Abstract:
Motivated by the application of (Ti, Al)N alloy compound in the coating layer, the ternary phase diagram of Ti-Al-N was analyzed by the calculation of the phase diagram (CALPHAD) technique. The isothermal sections of the Ti-Al-N ternary system were constructed and compared with the literature experimental results. The thermodynamic parameters of the Ti-Al-N ternary system and the related Ti-N and Al-N binary systems were adopted from literatures, whereas, those of the Ti-Al binary from the literatures were adjusted according to both the ternary and the binary phase equilibria. The consistency between the calculated results and the experimental data shows that considering the ternary thermodynamic relationship, the adjustments to the thermodynamic parameters of the related binaries are necessary.
Motivated by the application of (Ti, Al)N alloy compound in the coating layer, the ternary phase diagram of Ti-Al-N was analyzed by the calculation of the phase diagram (CALPHAD) technique. The isothermal sections of the Ti-Al-N ternary system were constructed and compared with the literature experimental results. The thermodynamic parameters of the Ti-Al-N ternary system and the related Ti-N and Al-N binary systems were adopted from literatures, whereas, those of the Ti-Al binary from the literatures were adjusted according to both the ternary and the binary phase equilibria. The consistency between the calculated results and the experimental data shows that considering the ternary thermodynamic relationship, the adjustments to the thermodynamic parameters of the related binaries are necessary.
2008, vol. 15, no. 4, pp.
425-429.
https://doi.org/10.1016/S1005-8850(08)60080-8
Abstract:
With the Voter-Chen version of embedded-atom model (EAM) potential and molecular dynamics, the melting of Ni3Al alloy was simulated by one-phase (conventional) and two-phase approaches. It is shown that the simulated melting point is dependent on the potential and the simulation method. The structures of the melts obtained by different simulation methods were analyzed by the pair correlation function, the coordination number, and the distribution of atom pair type (indexed by the Honeycutt-Andersen pair analysis technique). The results show that the structures are very similar.
With the Voter-Chen version of embedded-atom model (EAM) potential and molecular dynamics, the melting of Ni3Al alloy was simulated by one-phase (conventional) and two-phase approaches. It is shown that the simulated melting point is dependent on the potential and the simulation method. The structures of the melts obtained by different simulation methods were analyzed by the pair correlation function, the coordination number, and the distribution of atom pair type (indexed by the Honeycutt-Andersen pair analysis technique). The results show that the structures are very similar.
2008, vol. 15, no. 4, pp.
430-433.
https://doi.org/10.1016/S1005-8850(08)60081-X
Abstract:
The LY12CZ aluminum alloy specimens were corroded under the conditions of different test temperatures and exposure durations. After corrosion exposure, fatigue tests were performed. Scanning electron microscopy and optical microscope analyses on corrosion damage were carried out. The definition of surface corrosion damage ratio was provided to describe the extent of surface corrosion damage. On the basis of the measured data sets of the corrosion damage ratio, the probabilistic model of corrosion damage evolution was built. The corrosion damage decreased the fatigue life by a factor of about 1.25 to 2.38 and the prediction method of residual strength of the corroded structure was presented.
The LY12CZ aluminum alloy specimens were corroded under the conditions of different test temperatures and exposure durations. After corrosion exposure, fatigue tests were performed. Scanning electron microscopy and optical microscope analyses on corrosion damage were carried out. The definition of surface corrosion damage ratio was provided to describe the extent of surface corrosion damage. On the basis of the measured data sets of the corrosion damage ratio, the probabilistic model of corrosion damage evolution was built. The corrosion damage decreased the fatigue life by a factor of about 1.25 to 2.38 and the prediction method of residual strength of the corroded structure was presented.
2008, vol. 15, no. 4, pp.
434-439.
https://doi.org/10.1016/S1005-8850(08)60082-1
Abstract:
The influences of plastic deformation, aging treatment, and alloying elements on the texture of Cu-Cr-Zr alloys were ex- plored. The texture component and intensity of Cu-Cr-Zr alloys under various working conditions after aging treatment were characterized using the orientation distributing function (ODF). The influence of Zr content on the texture of Cu-Cr-Zr alloys was also analyzed. The reduction pass and deformation level were primary factors influencing the texture. Rolling texture appeared in a rolled plate and the fibrous textures of {111} and {001} were detected after 80% deformation. Fibrous texture with a main constituent of {111} improved the tensile strength of the alloy wire. The texture contents of {110}〈331〉 and {110}〈112〉 were predominated, whereas, those of {113}〈332〉 and {112}〈111〉 were in the minority in the Cu-Cr-Zr alloy with a higher Zr content (〉0.5wt%). However, in the samples with a lower Zr content (〈0.1wt%), the texture contents of {113}〈332〉, {112}〈111〉, and {111}〈110〉 were in the majority.
The influences of plastic deformation, aging treatment, and alloying elements on the texture of Cu-Cr-Zr alloys were ex- plored. The texture component and intensity of Cu-Cr-Zr alloys under various working conditions after aging treatment were characterized using the orientation distributing function (ODF). The influence of Zr content on the texture of Cu-Cr-Zr alloys was also analyzed. The reduction pass and deformation level were primary factors influencing the texture. Rolling texture appeared in a rolled plate and the fibrous textures of {111} and {001} were detected after 80% deformation. Fibrous texture with a main constituent of {111} improved the tensile strength of the alloy wire. The texture contents of {110}〈331〉 and {110}〈112〉 were predominated, whereas, those of {113}〈332〉 and {112}〈111〉 were in the minority in the Cu-Cr-Zr alloy with a higher Zr content (〉0.5wt%). However, in the samples with a lower Zr content (〈0.1wt%), the texture contents of {113}〈332〉, {112}〈111〉, and {111}〈110〉 were in the majority.
2008, vol. 15, no. 4, pp.
440-443.
https://doi.org/10.1016/S1005-8850(08)60083-3
Abstract:
The magnesium-lithium (Mg-Li) alloy exhibits two phase structures between 5.7wt% and 10.3wt% Li contents, consisting of the a (hcp) Mg-rich and the β (bcc) Li-rich phases, at room temperature. In the experiment, Mg-5Li-2Zn, Mg-9Li-2Zn, Mg-16Li-2Zn, Mg-22Li-2Zn, Mg-5Li-2Zn-2Ca, Mg-9Li-2Zn-2Ca, Mg-16Li-2Zn-2Ca, and Mg-22Li-2Zn-2Ca (wt%) were melted. During the melting process, the flux, which was composed of lithium chloride (LiCl) and lithium fluoride (LiF) in the proportion of 3:1 (mass ratio) and argon gas were used to protect the alloys from oxidation. The microstructure, mechanical properties, and cold-rolling workability of the wrought alloys were studied. The crystal grain of the alloys (adding Ga) is fine. The hardness of the studied alloys decreases with an increase in element Li. The density of the studied alloys is in the range of 1.187 to 1.617 g/cm3. The reduction of the Mg-16Li-2Zn and Mg-22Li-2Zn alloys can exceed 85% at room temperature. The Mg-9Li-2Zn-2Ca alloy was heat treated at 300℃ for 8, 12, 16, and 24 h, respectively. The optimum heat treatment of the Mg-9Li-2Zn-2Ca alloy is 300℃×12h by metallographic observation and by studying the mechanical properties of the alloys.
The magnesium-lithium (Mg-Li) alloy exhibits two phase structures between 5.7wt% and 10.3wt% Li contents, consisting of the a (hcp) Mg-rich and the β (bcc) Li-rich phases, at room temperature. In the experiment, Mg-5Li-2Zn, Mg-9Li-2Zn, Mg-16Li-2Zn, Mg-22Li-2Zn, Mg-5Li-2Zn-2Ca, Mg-9Li-2Zn-2Ca, Mg-16Li-2Zn-2Ca, and Mg-22Li-2Zn-2Ca (wt%) were melted. During the melting process, the flux, which was composed of lithium chloride (LiCl) and lithium fluoride (LiF) in the proportion of 3:1 (mass ratio) and argon gas were used to protect the alloys from oxidation. The microstructure, mechanical properties, and cold-rolling workability of the wrought alloys were studied. The crystal grain of the alloys (adding Ga) is fine. The hardness of the studied alloys decreases with an increase in element Li. The density of the studied alloys is in the range of 1.187 to 1.617 g/cm3. The reduction of the Mg-16Li-2Zn and Mg-22Li-2Zn alloys can exceed 85% at room temperature. The Mg-9Li-2Zn-2Ca alloy was heat treated at 300℃ for 8, 12, 16, and 24 h, respectively. The optimum heat treatment of the Mg-9Li-2Zn-2Ca alloy is 300℃×12h by metallographic observation and by studying the mechanical properties of the alloys.
2008, vol. 15, no. 4, pp.
444-450.
https://doi.org/10.1016/S1005-8850(08)60084-5
Abstract:
A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton (CA) approach to predict crystallization behaviour that is linked to thermal and electrical simulations to enable the study of the data writing and erasing processes. The CA approach is shown to be able to predict the evolution of the microstructure during the rapid heating and cooling cycles pertinent to data storage technology, and maps crystallization behaviour on the nanoscale. A simple example based on possible future nonvolatile phase-change random access solid-state memory is presented.
A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton (CA) approach to predict crystallization behaviour that is linked to thermal and electrical simulations to enable the study of the data writing and erasing processes. The CA approach is shown to be able to predict the evolution of the microstructure during the rapid heating and cooling cycles pertinent to data storage technology, and maps crystallization behaviour on the nanoscale. A simple example based on possible future nonvolatile phase-change random access solid-state memory is presented.
2008, vol. 15, no. 4, pp.
451-456.
https://doi.org/10.1016/S1005-8850(08)60085-7
Abstract:
The effect of electromagnetic stirring on the microstructure and wear behavior of coatings has been investigated. A series of iron-based coatings were fabricated by the plasma-transferred arc cladding process by applying different magnetic field currents. The microstructure and wear resistance of the composite coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and wet sand rubber wheel abrasion tester. The experimental results showed that the microstructure of the coatings was mainly the γ-Fe matrix and (Cr, Fe)7C3 carbide reinforced phase. The coatings were metallurgically bonded to the substrate. With increasing magnetic field current, the amount of the block-like (Cr, Fe)TC3 carbide reinforced phase increased at first, reached a local maximum, and then decreased sharply. When the magnetic field current reached 3 A, the block-like (Cr, Fe)TC3 carbides with high volume fraction were uniformly distributed in the matrix and the coating displayed a high microhardness and an excellent wear resistance under the wear test condition.
The effect of electromagnetic stirring on the microstructure and wear behavior of coatings has been investigated. A series of iron-based coatings were fabricated by the plasma-transferred arc cladding process by applying different magnetic field currents. The microstructure and wear resistance of the composite coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and wet sand rubber wheel abrasion tester. The experimental results showed that the microstructure of the coatings was mainly the γ-Fe matrix and (Cr, Fe)7C3 carbide reinforced phase. The coatings were metallurgically bonded to the substrate. With increasing magnetic field current, the amount of the block-like (Cr, Fe)TC3 carbide reinforced phase increased at first, reached a local maximum, and then decreased sharply. When the magnetic field current reached 3 A, the block-like (Cr, Fe)TC3 carbides with high volume fraction were uniformly distributed in the matrix and the coating displayed a high microhardness and an excellent wear resistance under the wear test condition.
2008, vol. 15, no. 4, pp.
457-460.
https://doi.org/10.1016/S1005-8850(08)60086-9
Abstract:
In order to investigate the anticorrosion performance of the organic coating/metal system, electrochemical impedance spectra (EIS) were measured in the 3.5wt% NaCl solution, the chemical component and the formation of corrosion products scale were analyzed by laser Raman microspectroscopy, and the pattern of the organic coating/metal system was observed by scanning electron microscopy (SEM). The characteristics and the delamination process of the organic coating/metal system were investigated systematically, and the emphases were on the transportation of the corrosive medium and the changes of the coating/metal interface. The results show that the impedance decreases at the initial immersion, then increases at the middle-immersion, and again decreases at last, which is related to the corrosion products scale. The concentration of Cl in the coating, which destroys the corrosion products scale, increases with the immersion time.
In order to investigate the anticorrosion performance of the organic coating/metal system, electrochemical impedance spectra (EIS) were measured in the 3.5wt% NaCl solution, the chemical component and the formation of corrosion products scale were analyzed by laser Raman microspectroscopy, and the pattern of the organic coating/metal system was observed by scanning electron microscopy (SEM). The characteristics and the delamination process of the organic coating/metal system were investigated systematically, and the emphases were on the transportation of the corrosive medium and the changes of the coating/metal interface. The results show that the impedance decreases at the initial immersion, then increases at the middle-immersion, and again decreases at last, which is related to the corrosion products scale. The concentration of Cl in the coating, which destroys the corrosion products scale, increases with the immersion time.
2008, vol. 15, no. 4, pp.
461-467.
https://doi.org/10.1016/S1005-8850(08)60087-0
Abstract:
To improve the durability as well as to reduce the cost of anodes, the IrO2+MnO2 composite coating anodes for NaCIO production were prepared by thermal decomposition. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) were carried out to investigate the morphologies, element distribution, and microstructure. The anodic polarization curves were employed to study the effect of sintering temperature on the Cl2 evolution reaction (CER) of the electrodes. The accelerated life tests (ALT) and electrochemical impedance spectroscopy measurement (EIS) were utilized to investigate the stability. The rules of NaCIO production were also studied by the static electrolysis experiment. The results indicate that sintering temperature has a significant influence on the CER properties as well as the ALT values of the electrodes. The electrode prepared at 400℃ has the best CER properties and the longest ALT value.
To improve the durability as well as to reduce the cost of anodes, the IrO2+MnO2 composite coating anodes for NaCIO production were prepared by thermal decomposition. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) were carried out to investigate the morphologies, element distribution, and microstructure. The anodic polarization curves were employed to study the effect of sintering temperature on the Cl2 evolution reaction (CER) of the electrodes. The accelerated life tests (ALT) and electrochemical impedance spectroscopy measurement (EIS) were utilized to investigate the stability. The rules of NaCIO production were also studied by the static electrolysis experiment. The results indicate that sintering temperature has a significant influence on the CER properties as well as the ALT values of the electrodes. The electrode prepared at 400℃ has the best CER properties and the longest ALT value.
2008, vol. 15, no. 4, pp.
468-473.
https://doi.org/10.1016/S1005-8850(08)60088-2
Abstract:
The cathode materials LiMn2O4 and rare earth elements La-doped or La and F dual-doped spinel lithium manganese oxides.were synthesized by the citric acid-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis (DTA) and thermogravimetry (TG) measurements, X-ray diffraction (XRD), scanning electronic microscope (SEM), cyclic voltammetry (CV), and charge-discharge test. XRD data shows that all the samples exhibit the same pure spinel phase, and the LiLa0.01Mn1.99O3.99F0.01 and LiLao.olMnl.9904 samples have smaller lattice parameters and unit cell volume than LiMn2O4. SEM indicates that LiLa0.01Mn1.99O3.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn2O4, LiLa0.01Mn1.99O4, and LiLa0.01Mn1.99O3.99F0.01 are 129.9, 122.8, and 126.4 mAh·g-1, and the capacity losses of the initial values after 50 cycles are 14.5%, 7.6%, and 8.0%, respectively The CVs show that the La and F dual-doped spinel displays a better reversibility than LiMn2O4.
The cathode materials LiMn2O4 and rare earth elements La-doped or La and F dual-doped spinel lithium manganese oxides.were synthesized by the citric acid-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis (DTA) and thermogravimetry (TG) measurements, X-ray diffraction (XRD), scanning electronic microscope (SEM), cyclic voltammetry (CV), and charge-discharge test. XRD data shows that all the samples exhibit the same pure spinel phase, and the LiLa0.01Mn1.99O3.99F0.01 and LiLao.olMnl.9904 samples have smaller lattice parameters and unit cell volume than LiMn2O4. SEM indicates that LiLa0.01Mn1.99O3.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn2O4, LiLa0.01Mn1.99O4, and LiLa0.01Mn1.99O3.99F0.01 are 129.9, 122.8, and 126.4 mAh·g-1, and the capacity losses of the initial values after 50 cycles are 14.5%, 7.6%, and 8.0%, respectively The CVs show that the La and F dual-doped spinel displays a better reversibility than LiMn2O4.
2008, vol. 15, no. 4, pp.
474-479.
https://doi.org/10.1016/S1005-8850(08)60089-4
Abstract:
Large advancement has been made in understanding the nucleation and growth of chemical vapor deposition (CVD) diamond, but the adhesion of CVD diamond to substrates is poor and there is no good method for quantitative evaluation of the adhesive strength. The blister test is a potentially powerful tool for characterizing the mechanical properties of diamond films. In this test, pressure was applied on a thin membrane and the out-of-plane deflection of the membrane center was measured. The Young's modulus, residual stress, and adhesive strength were simultaneously determined using the load-deflection behavior of a membrane. The free-standing window sample of diamond thin films was fabricated by means of photolithography and anisotropic wet etching. The research indicates that the adhesive strength of diamond thin films is 4.28±0.37 J/m2. This method uses a simple apparatus, and the fabrication of samples is very easy.
Large advancement has been made in understanding the nucleation and growth of chemical vapor deposition (CVD) diamond, but the adhesion of CVD diamond to substrates is poor and there is no good method for quantitative evaluation of the adhesive strength. The blister test is a potentially powerful tool for characterizing the mechanical properties of diamond films. In this test, pressure was applied on a thin membrane and the out-of-plane deflection of the membrane center was measured. The Young's modulus, residual stress, and adhesive strength were simultaneously determined using the load-deflection behavior of a membrane. The free-standing window sample of diamond thin films was fabricated by means of photolithography and anisotropic wet etching. The research indicates that the adhesive strength of diamond thin films is 4.28±0.37 J/m2. This method uses a simple apparatus, and the fabrication of samples is very easy.
2008, vol. 15, no. 4, pp.
480-483.
https://doi.org/10.1016/S1005-8850(08)60090-0
Abstract:
The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 um and with the center hole as small as 60 um.
The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 um and with the center hole as small as 60 um.
2008, vol. 15, no. 4, pp.
484-488.
https://doi.org/10.1016/S1005-8850(08)60091-2
Abstract:
The silicon assistant method to increase the reaction yield of carbothermal reduction of silica at a lower temperature is reported. The effect of silicon on the carbothermal reduction process has been investigated in detail. Compared with traditional reduction, the introduction of silicon can change the reaction path and further increase the conversion of silicon carbide at a lower temperature. It is considered that the assistant reduction consists of three steps: vaporizing and melting of silicon, formation of silicon monoxide, and synthesis of silicon carbide. The morphology of the synthesized SiC powders through the silicon assistant method can be affected apparently by the experimental temperature.
The silicon assistant method to increase the reaction yield of carbothermal reduction of silica at a lower temperature is reported. The effect of silicon on the carbothermal reduction process has been investigated in detail. Compared with traditional reduction, the introduction of silicon can change the reaction path and further increase the conversion of silicon carbide at a lower temperature. It is considered that the assistant reduction consists of three steps: vaporizing and melting of silicon, formation of silicon monoxide, and synthesis of silicon carbide. The morphology of the synthesized SiC powders through the silicon assistant method can be affected apparently by the experimental temperature.
2008, vol. 15, no. 4, pp.
489-494.
https://doi.org/10.1016/S1005-8850(08)60092-4
Abstract:
The preparation of natural brucite nanofibers through dispersion by the wet process is described. The test results indicate that brucite fibers can be well dispersed by using sodium dioctyl sulfosuccinate (OT) as the dispersant at a dispersant/fiber mass ratio of 0.15:1, dispersing for 30 min at a water/solid mass ratio of 20:1. The prepared nanofibers were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). It is shown that the prepared single brucite nanofiber is around 30 nm in diameter and the talus of the nonsingle brucite nanofibers is about 50-150 nm in diameter. Natural brucite mineral fibers were treated by the dispersion method to obtain nanomaterials. These fibers have significant advantages over artificial nanofibers both in yield and in cost.
The preparation of natural brucite nanofibers through dispersion by the wet process is described. The test results indicate that brucite fibers can be well dispersed by using sodium dioctyl sulfosuccinate (OT) as the dispersant at a dispersant/fiber mass ratio of 0.15:1, dispersing for 30 min at a water/solid mass ratio of 20:1. The prepared nanofibers were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). It is shown that the prepared single brucite nanofiber is around 30 nm in diameter and the talus of the nonsingle brucite nanofibers is about 50-150 nm in diameter. Natural brucite mineral fibers were treated by the dispersion method to obtain nanomaterials. These fibers have significant advantages over artificial nanofibers both in yield and in cost.
2008, vol. 15, no. 4, pp.
495-499.
https://doi.org/10.1016/S1005-8850(08)60093-6
Abstract:
The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that these factors affected the corrosion behaviors of silicon wafers to different degrees and had their suitable parameters that made the maximum corrosion rate of the wafers. The corrosion potential of (100) sttrface was lower than that of(111), whereas the current density of (100) was much higher than that of(111).
The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that these factors affected the corrosion behaviors of silicon wafers to different degrees and had their suitable parameters that made the maximum corrosion rate of the wafers. The corrosion potential of (100) sttrface was lower than that of(111), whereas the current density of (100) was much higher than that of(111).
2008, vol. 15, no. 4, pp.
500-504.
https://doi.org/10.1016/S1005-8850(08)60094-8
Abstract:
CuO/γ-Al2O3 has been considered as a promising and recycling sorbent to remove sulfur dioxide from flue gas. In this study, a series of CuO/γ-Al2O3 sorbents with different CuO loadings were prepared by impregnation. The monolayer coverage of CuO supported on γ-Al2O3 determined by X-ray quantitative analysis was 0.275 g CuO/g (γ-Al2O3). Below the monolayer coverage, CuO was found highly dispersed on γ-Al2O3. Thermogravimetric technique was used to study sulfation kinetics and sulfation recycling. It was found that the Langmuir kinetic adsorption model described well the experimental data at the rapid sulfation region of the CuO/γ-Al2O3 sorbent. The adsorption activation energy was 19.98 kJ/mol and the pre-exponential factor was 9.97×10-5 s-1·Pa-1. The CuO/γ-Al2O3 sorbent has shown good performance on regeneration, but long sulfation time might cause the deactivation of the CuO/γ-Al2O3 sorbent. It was also seen that the sulfated γ-Al2O3 support could not be reduced at 400℃.
CuO/γ-Al2O3 has been considered as a promising and recycling sorbent to remove sulfur dioxide from flue gas. In this study, a series of CuO/γ-Al2O3 sorbents with different CuO loadings were prepared by impregnation. The monolayer coverage of CuO supported on γ-Al2O3 determined by X-ray quantitative analysis was 0.275 g CuO/g (γ-Al2O3). Below the monolayer coverage, CuO was found highly dispersed on γ-Al2O3. Thermogravimetric technique was used to study sulfation kinetics and sulfation recycling. It was found that the Langmuir kinetic adsorption model described well the experimental data at the rapid sulfation region of the CuO/γ-Al2O3 sorbent. The adsorption activation energy was 19.98 kJ/mol and the pre-exponential factor was 9.97×10-5 s-1·Pa-1. The CuO/γ-Al2O3 sorbent has shown good performance on regeneration, but long sulfation time might cause the deactivation of the CuO/γ-Al2O3 sorbent. It was also seen that the sulfated γ-Al2O3 support could not be reduced at 400℃.
2008, vol. 15, no. 4, pp.
505-508.
https://doi.org/10.1016/S1005-8850(08)60095-X
Abstract:
A novel Ti/Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 composite was successfully prepared by infiltrating the melt into sintered Ti preform. It shows that the introduction of Ti particles into the composite results in an increase in elastic strain to 3% and an enhancement of the strength up to 2.1 GPa. High specific strength has been obtained because of the decrease in density of the composite. It is suggested that an improvement in the mechanical properties of the composite may be attributed to the generation of multiple shear bands and some deformation in the Ti particles.
A novel Ti/Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 composite was successfully prepared by infiltrating the melt into sintered Ti preform. It shows that the introduction of Ti particles into the composite results in an increase in elastic strain to 3% and an enhancement of the strength up to 2.1 GPa. High specific strength has been obtained because of the decrease in density of the composite. It is suggested that an improvement in the mechanical properties of the composite may be attributed to the generation of multiple shear bands and some deformation in the Ti particles.
2008, vol. 15, no. 4, pp.
509-513.
https://doi.org/10.1016/S1005-8850(08)60096-1
Abstract:
An inexpensive fly ash (FA), which is from a waste product, was employed to prepare fly ash/epoxy composites. The purpose of this study is to characterize the contributions of matrix viscoelasticity, hollow structure characteristic (porosity), and filler/matrix interface friction to the high vibration damping capacity of such composites. The damping properties of the composites were investigated in the temperature range of-40 to 150℃ and in the frequency range of 10 to 800 Hz by using a tension-compression mode. The results indicate that the peak value of damping loss factor (tan3) for the fly ash/epoxy composites can reach 0.70-0.90 in test specification, and the attenuation of damping loss factor is inconspicuous with increasing frequency. In addition, scanning electron microscope (SEM) was used to observe the morphology of the fly ash as well as its distribution in the matrix, which will help to analyze the effect of fly ash on the damping properties of the fly ash/epoxy composites.
An inexpensive fly ash (FA), which is from a waste product, was employed to prepare fly ash/epoxy composites. The purpose of this study is to characterize the contributions of matrix viscoelasticity, hollow structure characteristic (porosity), and filler/matrix interface friction to the high vibration damping capacity of such composites. The damping properties of the composites were investigated in the temperature range of-40 to 150℃ and in the frequency range of 10 to 800 Hz by using a tension-compression mode. The results indicate that the peak value of damping loss factor (tan3) for the fly ash/epoxy composites can reach 0.70-0.90 in test specification, and the attenuation of damping loss factor is inconspicuous with increasing frequency. In addition, scanning electron microscope (SEM) was used to observe the morphology of the fly ash as well as its distribution in the matrix, which will help to analyze the effect of fly ash on the damping properties of the fly ash/epoxy composites.
2008, vol. 15, no. 4, pp.
514-520.
https://doi.org/10.1016/S1005-8850(08)60097-3
Abstract:
The spherulite morphology of the rolled and subsequent heat-treated isotactic polypropylene (iPP) was observed by polarized microscopy, and the crystallinity evolution of materials was also measured by the wide angle X-ray scattering (WAXS). Rolling led to the oblate spherulites in the deformed iPP samples. The sheared crystalline lamellae broke apart into sets of crystalline blocks during rolling. As a result, the crystallinity of the iPP samples was greatly reduced during deformation, which induced the unclear spherulites and spherulite boundaries. Subsequent heat treatment resulted in the strong reerystallization of the rolled iPP samples. But the recrystaUizatinn in this work only meant the rearrangement of the macromolecule along the unbroken crystalline lamellae and the existing small crystalline blocks in the deformed spherulites. Heat treatment did not change the shape of the spherulites formed during deformation. The recrystallization also resulted in very clear spherulites and spherulite boundaries.
The spherulite morphology of the rolled and subsequent heat-treated isotactic polypropylene (iPP) was observed by polarized microscopy, and the crystallinity evolution of materials was also measured by the wide angle X-ray scattering (WAXS). Rolling led to the oblate spherulites in the deformed iPP samples. The sheared crystalline lamellae broke apart into sets of crystalline blocks during rolling. As a result, the crystallinity of the iPP samples was greatly reduced during deformation, which induced the unclear spherulites and spherulite boundaries. Subsequent heat treatment resulted in the strong reerystallization of the rolled iPP samples. But the recrystaUizatinn in this work only meant the rearrangement of the macromolecule along the unbroken crystalline lamellae and the existing small crystalline blocks in the deformed spherulites. Heat treatment did not change the shape of the spherulites formed during deformation. The recrystallization also resulted in very clear spherulites and spherulite boundaries.
Submit Manuscript
E-mail alert
RSS
