Search2011 Vol. 18, No. 6
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2011, vol. 18, no. 6, pp.
633-637.
https://doi.org/10.1007/s12613-011-0488-8
Abstract:
Planning and production optimization within multiple mines or several work sites (entities) mining systems by using fuzzy linear programming (LP) was studied. LP is the most commonly used operations research methods in mining engineering. After the introductory review of properties and limitations of applying LP, short reviews of the general settings of deterministic and fuzzy LP models are presented. With the purpose of comparative analysis, the application of both LP models is presented using the example of the Bauxite Basin Niksic with five mines. After the assessment, LP is an efficient mathematical modeling tool in production planning and solving many other single-criteria optimization problems of mining engineering. After the comparison of advantages and deficiencies of both deterministic and fuzzy LP models, the conclusion presents benefits of the fuzzy LP model but is also stating that seeking the optimal plan of production means to accomplish the overall analysis that will encompass the LP model approaches.
Planning and production optimization within multiple mines or several work sites (entities) mining systems by using fuzzy linear programming (LP) was studied. LP is the most commonly used operations research methods in mining engineering. After the introductory review of properties and limitations of applying LP, short reviews of the general settings of deterministic and fuzzy LP models are presented. With the purpose of comparative analysis, the application of both LP models is presented using the example of the Bauxite Basin Niksic with five mines. After the assessment, LP is an efficient mathematical modeling tool in production planning and solving many other single-criteria optimization problems of mining engineering. After the comparison of advantages and deficiencies of both deterministic and fuzzy LP models, the conclusion presents benefits of the fuzzy LP model but is also stating that seeking the optimal plan of production means to accomplish the overall analysis that will encompass the LP model approaches.
2011, vol. 18, no. 6, pp.
638-645.
https://doi.org/10.1007/s12613-011-0489-7
Abstract:
The kinetics of the chemical leaching of copper from low grade ore in ferric sulfate media was investigated using the constrained least square optimization technique. The experiments were carried out for different particle sizes in both the reactor and column at constant oxidation-reduction potential (Eh), pH values, and temperature. The main copper mineral was chalcopyrite. About 40% of Cu recovery is obtained after 7 d of reactor leaching at 85℃ using -0.5 mm size fraction, while the same recovery is obtained at 75℃ after 24 d. Also, about 23% of Cu recovery is obtained after 60 d of column leaching for +4–-8 mm size fraction whereas the Cu recovery is as low as about 15% for +8–-12.7 and +12.7–-25 mm size fractions. A 4-stage model for chalcopyrite dissolution was used to explain the observed dissolution behaviors. The results show that thick over-layers of sulphur components cause the parabolic behavior of chalcopyrite dissolution and the precipitation of Fe3+ plays the main role in chalcopyrite passivation. In the case of coarse particles, transformation from one stage to another takes a longer time, thus only two stages including the initial reaction on fresh surfaces and S0 deposition are observed.
The kinetics of the chemical leaching of copper from low grade ore in ferric sulfate media was investigated using the constrained least square optimization technique. The experiments were carried out for different particle sizes in both the reactor and column at constant oxidation-reduction potential (Eh), pH values, and temperature. The main copper mineral was chalcopyrite. About 40% of Cu recovery is obtained after 7 d of reactor leaching at 85℃ using -0.5 mm size fraction, while the same recovery is obtained at 75℃ after 24 d. Also, about 23% of Cu recovery is obtained after 60 d of column leaching for +4–-8 mm size fraction whereas the Cu recovery is as low as about 15% for +8–-12.7 and +12.7–-25 mm size fractions. A 4-stage model for chalcopyrite dissolution was used to explain the observed dissolution behaviors. The results show that thick over-layers of sulphur components cause the parabolic behavior of chalcopyrite dissolution and the precipitation of Fe3+ plays the main role in chalcopyrite passivation. In the case of coarse particles, transformation from one stage to another takes a longer time, thus only two stages including the initial reaction on fresh surfaces and S0 deposition are observed.
2011, vol. 18, no. 6, pp.
646-651.
https://doi.org/10.1007/s12613-011-0490-1
Abstract:
Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel. A typical synthesized Al2TiO5 inclusion was immersed in a CaO-SiO2-Al2O3 molten slag for different durations at 1823 K. The Al2TiO5 dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur. SiO2 diffuses or penetrates the inclusion more quickly than CaO, as indicated by the w(CaO)/w(SiO2) value in the reaction region. A liquid product (containing 0.7–1.2 w(CaO)/w(SiO2), 15wt%–20wt% Al2O3, and 5wt%–15wt% TiO2) forms on the inclusion surface when Al2TiO5 is dissolved in the slag. Al2TiO5 initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag. With increasing reaction time, the boundary reaches its largest distance, the Al2TiO5 dissolution rate equals the liquid product diffusion rate, and the dissolution process remains stable until the inclusion is completely dissolved.
Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel. A typical synthesized Al2TiO5 inclusion was immersed in a CaO-SiO2-Al2O3 molten slag for different durations at 1823 K. The Al2TiO5 dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur. SiO2 diffuses or penetrates the inclusion more quickly than CaO, as indicated by the w(CaO)/w(SiO2) value in the reaction region. A liquid product (containing 0.7–1.2 w(CaO)/w(SiO2), 15wt%–20wt% Al2O3, and 5wt%–15wt% TiO2) forms on the inclusion surface when Al2TiO5 is dissolved in the slag. Al2TiO5 initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag. With increasing reaction time, the boundary reaches its largest distance, the Al2TiO5 dissolution rate equals the liquid product diffusion rate, and the dissolution process remains stable until the inclusion is completely dissolved.
2011, vol. 18, no. 6, pp.
652-658.
https://doi.org/10.1007/s12613-011-0491-0
Abstract:
The change of inclusions and microstructure of 16Mn steel treated by Ce were observed, and the effect of austenitizing temperature on the microstructure was also examined. The results show that the inclusions are transformed from Si-Mn-Al composite oxide and MnS into AlCeO3, Ce2O2S, and MnS composite inclusions after being treated by Ce. Plenty of intragranular ferrites are formed in 16Mn steel containing ∼0.017wt% Ce. A large amount of intragranular acicular ferrites are formed after being austenitized for 20 min at 1473 K. The prior austenite grain size fit for the formation of intragranular acicular ferrites is about 120 μm.
The change of inclusions and microstructure of 16Mn steel treated by Ce were observed, and the effect of austenitizing temperature on the microstructure was also examined. The results show that the inclusions are transformed from Si-Mn-Al composite oxide and MnS into AlCeO3, Ce2O2S, and MnS composite inclusions after being treated by Ce. Plenty of intragranular ferrites are formed in 16Mn steel containing ∼0.017wt% Ce. A large amount of intragranular acicular ferrites are formed after being austenitized for 20 min at 1473 K. The prior austenite grain size fit for the formation of intragranular acicular ferrites is about 120 μm.
2011, vol. 18, no. 6, pp.
659-664.
https://doi.org/10.1007/s12613-011-0492-z
Abstract:
Zn-5wt% Al eutectic alloy was directionally solidified with different growth rates (5.32–250.0 μm/s) at a constant temperature gradient of 8.50 K/mm using a Bridgman-type growth apparatus. The values of eutectic spacing were measured from transverse sections of the samples. The dependences of the eutectic spacing and undercooling on growth rate are determined as λ=9.21V-0.53 and ΔT=0.0245V0.53, respectively. The results obtained in this work were compared with the Jackson-Hunt eutectic theory and the similar experimental results in the literature. Microhardness of directionally solidified samples was also measured by using a microhardness test device. The dependency of the microhardness on growth rate is found as Hv=115.64V0.13. Afterwards, the electrical resistivity (r) of the casting alloy changes from 40×10-9 to 108×10-9 Ω·m with the temperature rising in the range of 300–630 K. The enthalpy of fusion (ΔH) and specific heat (Cp) for the Zn-Al eutectic alloy are calculated to be 113.37 J/g and 0.309 J/(g·K), respectively by means of differential scanning calorimetry (DSC) from heating trace during the transformation from liquid to solid.
Zn-5wt% Al eutectic alloy was directionally solidified with different growth rates (5.32–250.0 μm/s) at a constant temperature gradient of 8.50 K/mm using a Bridgman-type growth apparatus. The values of eutectic spacing were measured from transverse sections of the samples. The dependences of the eutectic spacing and undercooling on growth rate are determined as λ=9.21V-0.53 and ΔT=0.0245V0.53, respectively. The results obtained in this work were compared with the Jackson-Hunt eutectic theory and the similar experimental results in the literature. Microhardness of directionally solidified samples was also measured by using a microhardness test device. The dependency of the microhardness on growth rate is found as Hv=115.64V0.13. Afterwards, the electrical resistivity (r) of the casting alloy changes from 40×10-9 to 108×10-9 Ω·m with the temperature rising in the range of 300–630 K. The enthalpy of fusion (ΔH) and specific heat (Cp) for the Zn-Al eutectic alloy are calculated to be 113.37 J/g and 0.309 J/(g·K), respectively by means of differential scanning calorimetry (DSC) from heating trace during the transformation from liquid to solid.
2011, vol. 18, no. 6, pp.
665-670.
https://doi.org/10.1007/s12613-011-0493-y
Abstract:
A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process, and the semisolid die forging process, microstructures, and properties of the magnesium alloy mobile telephone shell were investigated. The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press. The microstructures were observed by optical microscopy, the hardness was analyzed with a model 450SVD Vickers hardometer, the mechanical properties was measured with a CMT5105 tensile test machine, and the fractograph of elongated specimens was observed by scanning electron microscopy (SEM). The results reveal that with the increase of die forging force, the microstructures of the product become fine and dense. A lower preheating temperature and a longer dwell time are favorable to the formation of fine and dense microstructures. The optimum process conditions of preparing mobile telephone shells with excellent surface quality and microstructures are a die forging force of 2000 kN, a die preheating temperature of 250℃, and a dwell time of 240 s. After solution treatment at 430℃ and aging at 220℃ for 8 h, the Vickers hardness is 61.7 and the ultimate tensile strength of the product is 193 MPa. Tensile fractographs show the mixing mechanisms of quasi-cleavage fracture and ductile fracture.
A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process, and the semisolid die forging process, microstructures, and properties of the magnesium alloy mobile telephone shell were investigated. The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press. The microstructures were observed by optical microscopy, the hardness was analyzed with a model 450SVD Vickers hardometer, the mechanical properties was measured with a CMT5105 tensile test machine, and the fractograph of elongated specimens was observed by scanning electron microscopy (SEM). The results reveal that with the increase of die forging force, the microstructures of the product become fine and dense. A lower preheating temperature and a longer dwell time are favorable to the formation of fine and dense microstructures. The optimum process conditions of preparing mobile telephone shells with excellent surface quality and microstructures are a die forging force of 2000 kN, a die preheating temperature of 250℃, and a dwell time of 240 s. After solution treatment at 430℃ and aging at 220℃ for 8 h, the Vickers hardness is 61.7 and the ultimate tensile strength of the product is 193 MPa. Tensile fractographs show the mixing mechanisms of quasi-cleavage fracture and ductile fracture.
2011, vol. 18, no. 6, pp.
671-675.
https://doi.org/10.1007/s12613-011-0494-x
Abstract:
Precipitation reactions in the differential scanning calorimetry (DSC) of an Al-Cu-Mg-Ag alloy were identified by analyzing the results from hardness test, electrical conductivity test, and transmission electron microscope (TEM) examination. It is discovered that thermal effects can be identified through selected area electron diffraction and bright-field images. The reaction peaks around 171, 231, and 276℃ can be attributed to a structural rearrangement of coherent zones, to the precipitation of Ω phases, and to the precipitation of Ω and θ' and possible combination with the transition of θ'→θ, respectively. In addition, the hardness and electrical conductivity of the alloy change proportionately with the progression of reactions during the heating process. This phenomenon can be attributed to the evolution of the microstructure.
Precipitation reactions in the differential scanning calorimetry (DSC) of an Al-Cu-Mg-Ag alloy were identified by analyzing the results from hardness test, electrical conductivity test, and transmission electron microscope (TEM) examination. It is discovered that thermal effects can be identified through selected area electron diffraction and bright-field images. The reaction peaks around 171, 231, and 276℃ can be attributed to a structural rearrangement of coherent zones, to the precipitation of Ω phases, and to the precipitation of Ω and θ' and possible combination with the transition of θ'→θ, respectively. In addition, the hardness and electrical conductivity of the alloy change proportionately with the progression of reactions during the heating process. This phenomenon can be attributed to the evolution of the microstructure.
2011, vol. 18, no. 6, pp.
676-682.
https://doi.org/10.1007/s12613-011-0495-9
Abstract:
Based on the empirical electron surface model (EESM), the covalent electron density of dangling bonds (CEDDB) was calculated for various crystal planes of gold, and the surface energy was calculated further. Calculation results show that CEDDB has a great influence on the surface energy of various index surfaces and the anisotropy of the surface. The calculated surface energy is in agreement with experimental and other theoretical values. The calculated surface energy of the close-packed (111) surface has the lowest surface energy, which agrees with the theoretical prediction. Also, it is found that the spatial distribution of covalent bonds has a great influence on the surface energy of various index surfaces. Therefore, CEDDB should be a suitable parameter to describe and quantify the dangling bonds and surface energy of various crystal surfaces.
Based on the empirical electron surface model (EESM), the covalent electron density of dangling bonds (CEDDB) was calculated for various crystal planes of gold, and the surface energy was calculated further. Calculation results show that CEDDB has a great influence on the surface energy of various index surfaces and the anisotropy of the surface. The calculated surface energy is in agreement with experimental and other theoretical values. The calculated surface energy of the close-packed (111) surface has the lowest surface energy, which agrees with the theoretical prediction. Also, it is found that the spatial distribution of covalent bonds has a great influence on the surface energy of various index surfaces. Therefore, CEDDB should be a suitable parameter to describe and quantify the dangling bonds and surface energy of various crystal surfaces.
2011, vol. 18, no. 6, pp.
683-685.
https://doi.org/10.1007/s12613-011-0496-8
Abstract:
The electromagnetic properties of Ba2Co1.8Cu0.2Fe12O22 (Co2Y) and Ba3Co2Fe23.4Zn0.6O41 (Co2Z) were studied by measuring microwave scattering parameters. In the transmission spectra of Ba2Co1.8Cu0.2Fe12O22, a forbidden band emerges due to ferromagnetic resonance, and the permeability will turn to negative in the vicinity of the ferromagnetic resonance frequency. In the complex permittivity spectra of Ba3Co2Fe23.4Zn0.6O41, the negative permittivity can be obtained due to dielectric resonance. Therefore, Co2Y and Co2Z can be used to construct left-handed materials possessing negative permeability and negative permittivity simultaneously.
The electromagnetic properties of Ba2Co1.8Cu0.2Fe12O22 (Co2Y) and Ba3Co2Fe23.4Zn0.6O41 (Co2Z) were studied by measuring microwave scattering parameters. In the transmission spectra of Ba2Co1.8Cu0.2Fe12O22, a forbidden band emerges due to ferromagnetic resonance, and the permeability will turn to negative in the vicinity of the ferromagnetic resonance frequency. In the complex permittivity spectra of Ba3Co2Fe23.4Zn0.6O41, the negative permittivity can be obtained due to dielectric resonance. Therefore, Co2Y and Co2Z can be used to construct left-handed materials possessing negative permeability and negative permittivity simultaneously.
2011, vol. 18, no. 6, pp.
686-690.
https://doi.org/10.1007/s12613-011-0497-7
Abstract:
ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace. Structural characterization was carried out by transmission electron microscopy (TEM) and select-area electron diffraction (SAED), which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure. The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system. The three branches of a tetrapod serve as source, drain, and “gate”, respectively; while the fourth branch pointing upward works as the force trigger by vertically applying external force downward. The conductivity of each branch of ZnO-tetrapods increases 3–4 times under pressure. In such situation, the electrical current through the branches of ZnO tetrapods can be tuned by external force, and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.
ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace. Structural characterization was carried out by transmission electron microscopy (TEM) and select-area electron diffraction (SAED), which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure. The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system. The three branches of a tetrapod serve as source, drain, and “gate”, respectively; while the fourth branch pointing upward works as the force trigger by vertically applying external force downward. The conductivity of each branch of ZnO-tetrapods increases 3–4 times under pressure. In such situation, the electrical current through the branches of ZnO tetrapods can be tuned by external force, and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.
2011, vol. 18, no. 6, pp.
691-694.
https://doi.org/10.1007/s12613-011-0498-6
Abstract:
Long alumina fibers were prepared by sol-gel method. The spinning sol was obtained by mixing aluminum nitrate, tartaric acid, and polyvinylpyrrolidone with a mass ratio of 10:3:1.5. Thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibers. A little of α-Al2O3 phase is observed in the alumina precursor gel fibers sintered at 1273 K. The fibers with a uniform diameter can be obtained when sintered at 1473 K, and its main phase is also indentified as α-Al2O3.
Long alumina fibers were prepared by sol-gel method. The spinning sol was obtained by mixing aluminum nitrate, tartaric acid, and polyvinylpyrrolidone with a mass ratio of 10:3:1.5. Thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibers. A little of α-Al2O3 phase is observed in the alumina precursor gel fibers sintered at 1273 K. The fibers with a uniform diameter can be obtained when sintered at 1473 K, and its main phase is also indentified as α-Al2O3.
2011, vol. 18, no. 6, pp.
695-702.
https://doi.org/10.1007/s12613-011-0499-5
Abstract:
To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites, CNTs were coated by molybdenum layers using metal organic chemical vapor deposition, and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering. The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated. The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders. The electrical conductivity of the composites decreases with increasing Mo-CNT content. When the Mo-CNT content is 0.5wt%, the tensile strength and hardness of Mo-CNT/Al reach their maximum values. The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%, while the electrical conductivity only decreases by 7.1%, relative to sintered pure Al. The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.
To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites, CNTs were coated by molybdenum layers using metal organic chemical vapor deposition, and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering. The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated. The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders. The electrical conductivity of the composites decreases with increasing Mo-CNT content. When the Mo-CNT content is 0.5wt%, the tensile strength and hardness of Mo-CNT/Al reach their maximum values. The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%, while the electrical conductivity only decreases by 7.1%, relative to sintered pure Al. The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.
2011, vol. 18, no. 6, pp.
703-708.
https://doi.org/10.1007/s12613-011-0500-3
Abstract:
The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with time as the Al alloys infiltrate into SiCp preforms at different temperatures. The results show that infiltration of SiCp preforms by Al melt is a thermal activation process and there is an incubation period before the infiltration becomes stable. With the increase of Mg content in the Al alloys from 0wt% to 8wt%, the infiltration will become much easier, the incubation period becomes shorter and the infiltration rate is faster, but these effects are not obvious when the Mg content is higher than 8wt%. As for Si addition to the Al alloys, it has no obvious effect on the incubation period, but the infiltration rate increases markedly with the increase of Si content from 0wt% to 12wt% and the rate has no obvious change when the content is bigger than 12wt%. The effect of Mg and Si on the incubation period is related to the infiltration mechanism of Al pressureless infiltration into SiCp preforms and their impact on the infiltration rate is a combined result from viscosity and surface tension of Al melt and SiC-Al wetting ability.
The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with time as the Al alloys infiltrate into SiCp preforms at different temperatures. The results show that infiltration of SiCp preforms by Al melt is a thermal activation process and there is an incubation period before the infiltration becomes stable. With the increase of Mg content in the Al alloys from 0wt% to 8wt%, the infiltration will become much easier, the incubation period becomes shorter and the infiltration rate is faster, but these effects are not obvious when the Mg content is higher than 8wt%. As for Si addition to the Al alloys, it has no obvious effect on the incubation period, but the infiltration rate increases markedly with the increase of Si content from 0wt% to 12wt% and the rate has no obvious change when the content is bigger than 12wt%. The effect of Mg and Si on the incubation period is related to the infiltration mechanism of Al pressureless infiltration into SiCp preforms and their impact on the infiltration rate is a combined result from viscosity and surface tension of Al melt and SiC-Al wetting ability.
2011, vol. 18, no. 6, pp.
709-716.
https://doi.org/10.1007/s12613-011-0501-2
Abstract:
Gradient cemented carbides with the surface depleted in cubic phases were prepared following normal powder metallurgical procedures. Gradient zone formation and the influence of nitrogen introduction methods on the microstructure and performance of the alloys were investigated. The results show that the simple one-step vacuum sintering technique is doable for producing gradient cemented carbides. Gradient structure formation is attributed to the gradient in nitrogen activity during sintering, but is independent from nitrogen introduced methods. A uniform carbon distribution is found throughout the materials. Moreover, the transverse rupture strength of the cemented carbides can be increased by a gradient layer. Different nitrogen carriers give the alloys distinguishing microstructure and mechanical properties, and a gradient alloy with ultrafine-TiC0.5N0.5 is found optimal.
Gradient cemented carbides with the surface depleted in cubic phases were prepared following normal powder metallurgical procedures. Gradient zone formation and the influence of nitrogen introduction methods on the microstructure and performance of the alloys were investigated. The results show that the simple one-step vacuum sintering technique is doable for producing gradient cemented carbides. Gradient structure formation is attributed to the gradient in nitrogen activity during sintering, but is independent from nitrogen introduced methods. A uniform carbon distribution is found throughout the materials. Moreover, the transverse rupture strength of the cemented carbides can be increased by a gradient layer. Different nitrogen carriers give the alloys distinguishing microstructure and mechanical properties, and a gradient alloy with ultrafine-TiC0.5N0.5 is found optimal.
2011, vol. 18, no. 6, pp.
717-724.
https://doi.org/10.1007/s12613-011-0502-1
Abstract:
The brazing process of cubic boron nitride (CBN) grains and AISI 1045 steel with AgCuTi-TiC mixed powder as a filler material was carried out. The joining strength and the interfacial microstructure were investigated. The experimental results indicate that the spreading of the molten filler material on AISI 1045 steel is decreased with the increase of TiC content. A good interface is formed between the TiC particulates and AgCuTi alloy through the wetting behavior. In the case of AgCuTi+16wt% TiC, the strength of the brazed steel-to-steel joints reached the highest value of 95 MPa dependent upon the reinforcement effect of TiC particles within the filler layer. Brazing resultants of TiB2, TiB, and TiN are produced at the interface of the CBN grains and the AgCuTi-TiC filler layer by virtue of the interdiffusion of B, N, and Ti atoms.
The brazing process of cubic boron nitride (CBN) grains and AISI 1045 steel with AgCuTi-TiC mixed powder as a filler material was carried out. The joining strength and the interfacial microstructure were investigated. The experimental results indicate that the spreading of the molten filler material on AISI 1045 steel is decreased with the increase of TiC content. A good interface is formed between the TiC particulates and AgCuTi alloy through the wetting behavior. In the case of AgCuTi+16wt% TiC, the strength of the brazed steel-to-steel joints reached the highest value of 95 MPa dependent upon the reinforcement effect of TiC particles within the filler layer. Brazing resultants of TiB2, TiB, and TiN are produced at the interface of the CBN grains and the AgCuTi-TiC filler layer by virtue of the interdiffusion of B, N, and Ti atoms.
2011, vol. 18, no. 6, pp.
725-730.
https://doi.org/10.1007/s12613-011-0503-0
Abstract:
A novel approach to produce an intermetallic composite coating was put forward. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) analysis, microhardness test, and ball-on-disc wear experiment. XRD results indicate that some new phases FeAl, Fe0.23Ni0.77Al, and Ni3Al exit in the composite coating with the Al2O3 addition. SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures. The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating. The formation mechanism of the intermetallic compounds was also investigated.
A novel approach to produce an intermetallic composite coating was put forward. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) analysis, microhardness test, and ball-on-disc wear experiment. XRD results indicate that some new phases FeAl, Fe0.23Ni0.77Al, and Ni3Al exit in the composite coating with the Al2O3 addition. SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures. The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating. The formation mechanism of the intermetallic compounds was also investigated.
2011, vol. 18, no. 6, pp.
731-740.
https://doi.org/10.1007/s12613-011-0504-z
Abstract:
The influences of cupric ion concentration (5–35 g/L), current density (500–2000 A/m2), circulation rate of the electrolyte solution (15–120 mL/min), and temperature (25–60℃) on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated. Two industrial processes, electrorefining (ER) cells with a synthetic electrolyte and electrowinning (EW) cells with an original solution of copper mineral leaching, were utilized to produce copper powders. Finally, the statistical full factorial method of design of experiments (DOE) was employed to investigate the interaction or the main effects of processes. The results show that increasing the copper concentration and temperature can increase the grain size, apparent density, and electrical energy consumption. On the other hand, increasing the current density and circulation rate of the electrolyte can decrease them. This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.
The influences of cupric ion concentration (5–35 g/L), current density (500–2000 A/m2), circulation rate of the electrolyte solution (15–120 mL/min), and temperature (25–60℃) on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated. Two industrial processes, electrorefining (ER) cells with a synthetic electrolyte and electrowinning (EW) cells with an original solution of copper mineral leaching, were utilized to produce copper powders. Finally, the statistical full factorial method of design of experiments (DOE) was employed to investigate the interaction or the main effects of processes. The results show that increasing the copper concentration and temperature can increase the grain size, apparent density, and electrical energy consumption. On the other hand, increasing the current density and circulation rate of the electrolyte can decrease them. This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.
2011, vol. 18, no. 6, pp.
741-747.
https://doi.org/10.1007/s12613-011-0505-y
Abstract:
The spout-fluidizing characteristics of high-carbon ferromanganese powders with different sizes and masses were studied via a plexiglass spout-fluidized bed with an inner diameter of 30 mm and a height of 1000 mm. The relationships between bed voidage and such parameters as bed height, particle size, fluidizing air velocity, and air flow were obtained. Experimental results show that the powder material with high density can be fluidized in the spout-fluidized bed where the particle size is a key factor influencing the quality of fluidization.
The spout-fluidizing characteristics of high-carbon ferromanganese powders with different sizes and masses were studied via a plexiglass spout-fluidized bed with an inner diameter of 30 mm and a height of 1000 mm. The relationships between bed voidage and such parameters as bed height, particle size, fluidizing air velocity, and air flow were obtained. Experimental results show that the powder material with high density can be fluidized in the spout-fluidized bed where the particle size is a key factor influencing the quality of fluidization.
2011, vol. 18, no. 6, pp.
748-752.
https://doi.org/10.1007/s12613-011-0506-x
Abstract:
To synthesize pure γ-La2S3 at lower temperature, lanthanide complex La(Et2S2CN)3·phen, containing La-S bond, was chosen as the precursors to decompose. The obtained samples were characterized by X-ray power diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) with an energy dispersive spectrometer and UV-Vis diffuse reflectance spectra. The decomposition mechanism of the lanthanide complex was studied by thermogravimetric analyses (TGA). The results show that the obtained samples are cubic phase particles with sizes among 20–50 nm and the band gap is 2.97 eV, which is bigger than that of its bulk crystal. TG/DTG results indicate that La(Et2S2CN)3·phen decomposed to γ-La2S3 via La4(Et2S2CN)3 as an intermediate product.
To synthesize pure γ-La2S3 at lower temperature, lanthanide complex La(Et2S2CN)3·phen, containing La-S bond, was chosen as the precursors to decompose. The obtained samples were characterized by X-ray power diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) with an energy dispersive spectrometer and UV-Vis diffuse reflectance spectra. The decomposition mechanism of the lanthanide complex was studied by thermogravimetric analyses (TGA). The results show that the obtained samples are cubic phase particles with sizes among 20–50 nm and the band gap is 2.97 eV, which is bigger than that of its bulk crystal. TG/DTG results indicate that La(Et2S2CN)3·phen decomposed to γ-La2S3 via La4(Et2S2CN)3 as an intermediate product.
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