Search2010 Vol. 17, No. 2
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2010, vol. 17, no. 2, pp.
127-131.
https://doi.org/10.1007/s12613-010-0201-3
Abstract:
The production of MoO3 from Sarcheshmeh molybdenite concentrate via a pyro-hydrometallurgical process was studied. The molybdenite concentrate and sodium carbonate were premixed and fused under air atmosphere. Then the fused products were leached in water and the dissolved molybdenum was recovered as ammonium molybdate. The ammonium molybdate was then calcined to produce molybdic oxide. At the fusion stage, the effect of the mass ratio of carbonate to sulfide on the reaction products and the solubility of the products was investigated. The results show that during the fusion, sodium molybdate and sodium sulfate are the final reaction products and sodium sulfide is detected as an intermediate reaction product. By melting at 850℃ with 5wt% excess carbonate, the maximum solubility of the products is obtained. The molybdenum is recovered from the solutions as ammonium molybdate.
The production of MoO3 from Sarcheshmeh molybdenite concentrate via a pyro-hydrometallurgical process was studied. The molybdenite concentrate and sodium carbonate were premixed and fused under air atmosphere. Then the fused products were leached in water and the dissolved molybdenum was recovered as ammonium molybdate. The ammonium molybdate was then calcined to produce molybdic oxide. At the fusion stage, the effect of the mass ratio of carbonate to sulfide on the reaction products and the solubility of the products was investigated. The results show that during the fusion, sodium molybdate and sodium sulfate are the final reaction products and sodium sulfide is detected as an intermediate reaction product. By melting at 850℃ with 5wt% excess carbonate, the maximum solubility of the products is obtained. The molybdenum is recovered from the solutions as ammonium molybdate.
2010, vol. 17, no. 2, pp.
132-136.
https://doi.org/10.1007/s12613-010-0202-2
Abstract:
The extraction process of gold and silver from the gold clay ore containing arsenic and manganese was investigated. With the conventional technique, the leaching rates of gold and silver are 78.23% and 49.02%, respectively. To eliminate the negative effects of arsenic and manganese on cyanidation and increase the gold and silver leaching rates, a novel catalyst was added. The content of the catalyst used in the process was 8 g per 500 g org sample, the sample size was 60 μm and the pH value was kept between 10 and 11. Leaching with the catalyst for 3–5 h under certain conditions, the gold leaching rate increased to over 90% and the silver leaching rate increased to 80%–90%. The catalyst can effectively liberate gold and silver from the enclosure of arsenic and manganese and the industrial experiment has great significance to the development and utilization of the gold clay ore containing arsenic and manganese.
The extraction process of gold and silver from the gold clay ore containing arsenic and manganese was investigated. With the conventional technique, the leaching rates of gold and silver are 78.23% and 49.02%, respectively. To eliminate the negative effects of arsenic and manganese on cyanidation and increase the gold and silver leaching rates, a novel catalyst was added. The content of the catalyst used in the process was 8 g per 500 g org sample, the sample size was 60 μm and the pH value was kept between 10 and 11. Leaching with the catalyst for 3–5 h under certain conditions, the gold leaching rate increased to over 90% and the silver leaching rate increased to 80%–90%. The catalyst can effectively liberate gold and silver from the enclosure of arsenic and manganese and the industrial experiment has great significance to the development and utilization of the gold clay ore containing arsenic and manganese.
2010, vol. 17, no. 2, pp.
137-142.
https://doi.org/10.1007/s12613-010-0203-1
Abstract:
The effect of F, K, and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis (DTA) and X-ray diffraction (XRD). It has been identified that alkaline elements K and Na in the Baiyunebo ore instigate the formation of low melting point compounds Na2SiO3 and Na2O·Fe2O3 and the generation of molten state in the solid phase sintering. Element F in the Baiyunebo ore facilitates the formation of cuspidine compound 3CaO·2SiO2·CaF2 in the solid phase reaction. The cuspidine compound is kept in solid as one of the final products through the entire sintering process due to its high melting point. In the sintering process, CaF2 and SiO2 react with CaO first and form 3CaO·2SiO2·CaF2 and 3CaO·2SiO2, so the formation of ferrites, Na2O·Fe2O3, and 2CaO·Fe2O3 is inhibited.
The effect of F, K, and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis (DTA) and X-ray diffraction (XRD). It has been identified that alkaline elements K and Na in the Baiyunebo ore instigate the formation of low melting point compounds Na2SiO3 and Na2O·Fe2O3 and the generation of molten state in the solid phase sintering. Element F in the Baiyunebo ore facilitates the formation of cuspidine compound 3CaO·2SiO2·CaF2 in the solid phase reaction. The cuspidine compound is kept in solid as one of the final products through the entire sintering process due to its high melting point. In the sintering process, CaF2 and SiO2 react with CaO first and form 3CaO·2SiO2·CaF2 and 3CaO·2SiO2, so the formation of ferrites, Na2O·Fe2O3, and 2CaO·Fe2O3 is inhibited.
2010, vol. 17, no. 2, pp.
143-148.
https://doi.org/10.1007/s12613-010-0204-0
Abstract:
Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments. It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence inhibitor. It dramatically increases the peak concentration time, and greatly decreases the dead volume, and reduces the minimum residence time. The gas blowing location, gas flow rate, and porous plug area greatly influence the flow characteristics in the tundish; the gas blowing location near the baffle, smaller gas flow rate, and smaller porous plug area are better for improving the fluid flow characteristics. Using gas blowing can reduce the difference of flows at the middle outlets and side outlets for the multi-strand tundish. Bubbles produced by gas blowing can absorb small inclusions and provide the condition for inclusion collision and aggregation. Therefore, introducing gas blowing into a tundish and combining the turbulence inhibitor can improve inclusion floating and removal, and the cleanness of molten steel can be advanced.
Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments. It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence inhibitor. It dramatically increases the peak concentration time, and greatly decreases the dead volume, and reduces the minimum residence time. The gas blowing location, gas flow rate, and porous plug area greatly influence the flow characteristics in the tundish; the gas blowing location near the baffle, smaller gas flow rate, and smaller porous plug area are better for improving the fluid flow characteristics. Using gas blowing can reduce the difference of flows at the middle outlets and side outlets for the multi-strand tundish. Bubbles produced by gas blowing can absorb small inclusions and provide the condition for inclusion collision and aggregation. Therefore, introducing gas blowing into a tundish and combining the turbulence inhibitor can improve inclusion floating and removal, and the cleanness of molten steel can be advanced.
2010, vol. 17, no. 2, pp.
149-153.
https://doi.org/10.1007/s12613-010-0205-z
Abstract:
The steady laminar boundary layer flow adjacent to a vertical plate with prescribed surface temperature immersed in an incompressible viscous fluid, where the effect of thermal radiation was taken into consideration, was investigated. The governing partial differential equations were transformed into a system of ordinary differential equations using similarity transformation, before being solved numerically by the shooting method. Both assisting and opposing buoyant flows were considered. It is found that dual solutions exist for both cases. Moreover, numerical results show that the heat transfer rate at the surface decreases in the presence of the radiation effect.
The steady laminar boundary layer flow adjacent to a vertical plate with prescribed surface temperature immersed in an incompressible viscous fluid, where the effect of thermal radiation was taken into consideration, was investigated. The governing partial differential equations were transformed into a system of ordinary differential equations using similarity transformation, before being solved numerically by the shooting method. Both assisting and opposing buoyant flows were considered. It is found that dual solutions exist for both cases. Moreover, numerical results show that the heat transfer rate at the surface decreases in the presence of the radiation effect.
2010, vol. 17, no. 2, pp.
154-158.
https://doi.org/10.1007/s12613-010-0206-y
Abstract:
The nozzle clogging behavior of Ti-bearing IF steel was studied by metallographic analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). According to the experimental results, nozzle clogging primarily appears three layers. There are a lot of large-sized iron particles in the inner layer and mainly slag phase in the middle and outer layers. The principal clog constituents of the inner layer are loose alumina cluster inclusions and granular shaped alumina inclusions, containing iron particles. The clog constituents of the middle layer are mainly dendrite alumina inclusions. The primary phases existing in nozzle clogging are FeO·TiO2 and FeO·Al2O3 besides α-Al2O3 and α-Fe. The FeO·TiO2 phases among the deposits adhere the deposits together firmly enough to lead to the inferior castability of Ti-bearing ultra low carbon steel compared with that of Ti-free low carbon Al-killed steel.
The nozzle clogging behavior of Ti-bearing IF steel was studied by metallographic analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). According to the experimental results, nozzle clogging primarily appears three layers. There are a lot of large-sized iron particles in the inner layer and mainly slag phase in the middle and outer layers. The principal clog constituents of the inner layer are loose alumina cluster inclusions and granular shaped alumina inclusions, containing iron particles. The clog constituents of the middle layer are mainly dendrite alumina inclusions. The primary phases existing in nozzle clogging are FeO·TiO2 and FeO·Al2O3 besides α-Al2O3 and α-Fe. The FeO·TiO2 phases among the deposits adhere the deposits together firmly enough to lead to the inferior castability of Ti-bearing ultra low carbon steel compared with that of Ti-free low carbon Al-killed steel.
2010, vol. 17, no. 2, pp.
159-166.
https://doi.org/10.1007/s12613-010-0207-x
Abstract:
Based on the production practice of medium carbon thin slabs in the CSP plant, the reasons and influencing factors for the formation of longitudinal cracks were investigated, and some industrial measures were taken to eliminate the cracks. The results show that the efficient solutions to reduce longitudinal cracks are improving the performance of the mold powder, stabilizing the mold heat flux, and maintaining a proper taper of the mold during casting. Proper pouring temperature and secondary cooling also play important roles in preventing longitudinal surface cracks.
Based on the production practice of medium carbon thin slabs in the CSP plant, the reasons and influencing factors for the formation of longitudinal cracks were investigated, and some industrial measures were taken to eliminate the cracks. The results show that the efficient solutions to reduce longitudinal cracks are improving the performance of the mold powder, stabilizing the mold heat flux, and maintaining a proper taper of the mold during casting. Proper pouring temperature and secondary cooling also play important roles in preventing longitudinal surface cracks.
2010, vol. 17, no. 2, pp.
167-172.
https://doi.org/10.1007/s12613-010-0208-9
Abstract:
The hot compression tests of Super304H austenitic heat resistant steel were carried out at 800–1200℃ and 0.005–5 s-1 using a Gleeble 3500 thermal-mechanical simulator, and its deformation behavior was analyzed. The results show that the flow stress of Super304H steel decreases with the decrease of strain rate and the increase of deformation temperature; the hot deformation activation energy of the steel is 485 kJ/mol. The hot deformation equation and the relationship between the peak stress and the deformation temperature and strain rate is obtained. The softening caused by deformation heating cannot be neglected when both the deformation temperature and strain rate are higher.
The hot compression tests of Super304H austenitic heat resistant steel were carried out at 800–1200℃ and 0.005–5 s-1 using a Gleeble 3500 thermal-mechanical simulator, and its deformation behavior was analyzed. The results show that the flow stress of Super304H steel decreases with the decrease of strain rate and the increase of deformation temperature; the hot deformation activation energy of the steel is 485 kJ/mol. The hot deformation equation and the relationship between the peak stress and the deformation temperature and strain rate is obtained. The softening caused by deformation heating cannot be neglected when both the deformation temperature and strain rate are higher.
2010, vol. 17, no. 2, pp.
173-178.
https://doi.org/10.1007/s12613-010-0209-8
Abstract:
According to the stress-strain curves of single-phase martensite and single-phase ferrite steels, whose compositions are similar to those of martensite and ferrite in low Si-Mn-Nb dual-phase steel, the stress-strain curve of the low Si-Mn-Nb dual-phase steel was simulated using the finite element method (FEM). The simulated result was compared with the measured one and they fit closely with each other, which proves that the FE model is correct. Based on the FE model, the microstress and microstrain of the dual-phase steel were analyzed. Meanwhile, the effective factors such as the volume fraction of martensite and the yield stress ratio between martensite and ferrite phases on the stress-strain curves of the dual-phase steel were simulated, too. The simulated results indicate that for the low Si-Mn-Nb dual-phase steel, the maximum stress occurs in the martensite region, while the maximum strain occurs in the ferrite one. The effect of the volume fraction of martensite (fM) and the yield stress ratio on the stress-strain curve of the dual-phase steel is small in the elastic part, while it is obvious in the plastic part. In the plastic part of this curve, the strain decreases with the increase of fM, while it decreases with the decrease of the yield stress ratio.
According to the stress-strain curves of single-phase martensite and single-phase ferrite steels, whose compositions are similar to those of martensite and ferrite in low Si-Mn-Nb dual-phase steel, the stress-strain curve of the low Si-Mn-Nb dual-phase steel was simulated using the finite element method (FEM). The simulated result was compared with the measured one and they fit closely with each other, which proves that the FE model is correct. Based on the FE model, the microstress and microstrain of the dual-phase steel were analyzed. Meanwhile, the effective factors such as the volume fraction of martensite and the yield stress ratio between martensite and ferrite phases on the stress-strain curves of the dual-phase steel were simulated, too. The simulated results indicate that for the low Si-Mn-Nb dual-phase steel, the maximum stress occurs in the martensite region, while the maximum strain occurs in the ferrite one. The effect of the volume fraction of martensite (fM) and the yield stress ratio on the stress-strain curve of the dual-phase steel is small in the elastic part, while it is obvious in the plastic part. In the plastic part of this curve, the strain decreases with the increase of fM, while it decreases with the decrease of the yield stress ratio.
2010, vol. 17, no. 2, pp.
179-184.
https://doi.org/10.1007/s12613-010-0210-2
Abstract:
Ultra low carbon steels by the thermal mechanical control process (TMCP) with less Ni, Cr, and Mo contents have been developed for 550 MPa grade heavy gauge ship hulls and offshore structures. The relationships among microstructures, process, and properties of the studied steel have been investigated. A series of accurate control technologies have been developed for this kind of steel. Cu microalloying and TMCP+relaxation precipitation control (RPC)+accelerated cooling process were employed to optimize the mechanical properties and ensure the homogeneity of the 80-mm thick plate. The microstructures of thin plates slightly changed from surface to center, but the microstructures of the heavy gauge plate (80 mm) changed notably. Adopting the simple composition, it can meet the requirement of thin plates by adopting a few microalloys. As for thick plates (80 mm), a little higher Cu and Ni contents should be adopted. These steels can meet the needs without tempering. By these ways, the properties of the steels can be optimized, and the cost can be decreased notably.
Ultra low carbon steels by the thermal mechanical control process (TMCP) with less Ni, Cr, and Mo contents have been developed for 550 MPa grade heavy gauge ship hulls and offshore structures. The relationships among microstructures, process, and properties of the studied steel have been investigated. A series of accurate control technologies have been developed for this kind of steel. Cu microalloying and TMCP+relaxation precipitation control (RPC)+accelerated cooling process were employed to optimize the mechanical properties and ensure the homogeneity of the 80-mm thick plate. The microstructures of thin plates slightly changed from surface to center, but the microstructures of the heavy gauge plate (80 mm) changed notably. Adopting the simple composition, it can meet the requirement of thin plates by adopting a few microalloys. As for thick plates (80 mm), a little higher Cu and Ni contents should be adopted. These steels can meet the needs without tempering. By these ways, the properties of the steels can be optimized, and the cost can be decreased notably.
2010, vol. 17, no. 2, pp.
185-191.
https://doi.org/10.1007/s12613-010-0211-1
Abstract:
A new titanium alloy Ti12.5Zr2.5Nb2.5Ta (TZNT) for surgical implant application was synthesized and fully annealed at 700℃ for 45 min. The microstructure and the mechanical properties such as tensile properties and fatigue properties were investigated. The results show that TZNT mainly consists of a lot of lamella α-phase clusters with different orientations distributed in the original β-phase grain boundaries and a small amount of β phases between the lamella α phases. The alloy exhibits better ductility, lower modulus of elasticity, and lower admission strain in comparison with Ti6Al4V and Ti6Al7Nb, indicating that it has better biomechanical compatibility with human bones. The fatigue limit of TZNT is 333 MPa, at which the specimen has not failed at 107 cycles. A large number of striations present in the stable fatigue crack propagation area, and many dimples in the fast fatigue crack propagation area are observed, indicating the ductile fracture of the new alloy.
A new titanium alloy Ti12.5Zr2.5Nb2.5Ta (TZNT) for surgical implant application was synthesized and fully annealed at 700℃ for 45 min. The microstructure and the mechanical properties such as tensile properties and fatigue properties were investigated. The results show that TZNT mainly consists of a lot of lamella α-phase clusters with different orientations distributed in the original β-phase grain boundaries and a small amount of β phases between the lamella α phases. The alloy exhibits better ductility, lower modulus of elasticity, and lower admission strain in comparison with Ti6Al4V and Ti6Al7Nb, indicating that it has better biomechanical compatibility with human bones. The fatigue limit of TZNT is 333 MPa, at which the specimen has not failed at 107 cycles. A large number of striations present in the stable fatigue crack propagation area, and many dimples in the fast fatigue crack propagation area are observed, indicating the ductile fracture of the new alloy.
2010, vol. 17, no. 2, pp.
192-198.
https://doi.org/10.1007/s12613-010-0212-0
Abstract:
The influences of 2.5wt% Mn addition on the microstructure and mechanical properties of the Cu-11.9wt%Al-3.8wt%Ni shape memory alloy (SMA) were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimeter (DSC). The experimental results show that Mn addition influences considerably the austenite-martensite transformation temperatures and the kind of martensite in the Cu-Al-Ni alloy. The martensitic transformation changes from a mixed xed β1→β'1+γ'1 transformation to a single β1→β'1 martensite transformation together with a decrease in transformation temperatures. In addition, the observations reveal that the grain size of the Cu-Al-Ni alloy can be controlled with the addition of 2.5wt% Mn and thus its mechanical properties can be enhanced. The Cu-Al-Ni-Mn alloy exhibits better mechanical properties with the high ultimate compression strength and ductility of 952 MPa and 15%, respectively. These improvements are attributed to a decrease in grain size. However, the hardness decreases from Hv 230 to Hv 140 with the Mn addition.
The influences of 2.5wt% Mn addition on the microstructure and mechanical properties of the Cu-11.9wt%Al-3.8wt%Ni shape memory alloy (SMA) were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimeter (DSC). The experimental results show that Mn addition influences considerably the austenite-martensite transformation temperatures and the kind of martensite in the Cu-Al-Ni alloy. The martensitic transformation changes from a mixed xed β1→β'1+γ'1 transformation to a single β1→β'1 martensite transformation together with a decrease in transformation temperatures. In addition, the observations reveal that the grain size of the Cu-Al-Ni alloy can be controlled with the addition of 2.5wt% Mn and thus its mechanical properties can be enhanced. The Cu-Al-Ni-Mn alloy exhibits better mechanical properties with the high ultimate compression strength and ductility of 952 MPa and 15%, respectively. These improvements are attributed to a decrease in grain size. However, the hardness decreases from Hv 230 to Hv 140 with the Mn addition.
2010, vol. 17, no. 2, pp.
199-203.
https://doi.org/10.1007/s12613-010-0213-z
Abstract:
Fe-based amorphous alloys with high iron content of 76at%–80at% were synthesized in the Fe-Mo-Si-P-C-B alloy system by the single roller melt-spinning technique. The amorphous ribbons exhibit high Vickers microhardness and good ductility, which can be indented and bent 180° without breaking. A number of shear bands could be observed around the indents and the bending traces. Studies on the magnetic properties of the amorphous alloys show that they possess high saturation magnetizations of 1.34–1.6 T, which increases with the increase of iron content. The core losses of these Fe-based amorphous alloys at various magnetic inductions were tested and found to be significantly dependent on their components. The Fe-Mo-Si-P-C-B amorphous alloys with excellent mechanical properties and soft magnetic properties have promising potential in functional applications.
Fe-based amorphous alloys with high iron content of 76at%–80at% were synthesized in the Fe-Mo-Si-P-C-B alloy system by the single roller melt-spinning technique. The amorphous ribbons exhibit high Vickers microhardness and good ductility, which can be indented and bent 180° without breaking. A number of shear bands could be observed around the indents and the bending traces. Studies on the magnetic properties of the amorphous alloys show that they possess high saturation magnetizations of 1.34–1.6 T, which increases with the increase of iron content. The core losses of these Fe-based amorphous alloys at various magnetic inductions were tested and found to be significantly dependent on their components. The Fe-Mo-Si-P-C-B amorphous alloys with excellent mechanical properties and soft magnetic properties have promising potential in functional applications.
2010, vol. 17, no. 2, pp.
204-207.
https://doi.org/10.1007/s12613-010-0214-y
Abstract:
With the addition of Si to replace some P, Pd40.5Ni40.5SixP19-x (x=0, 2.5, 5, 9.5, 14, and 19 in atomic number fraction) bulk glassy samples with the diameter of about 5 mm were successfully prepared by use of flux treatment and water quenching technology. With the increase of Si content, the glass forming ability of Pd40.5Ni40.5SixP19-x increases first for low Si content and then decreases for high Si content (Si≥9.5at%). The Pd40.5Ni40.5Si5P14 glassy alloy possesses the largest supercooled liquid region ΔT of 119 K, the largest reduced glass transition temperature of 0.621, and the largest γ parameter of 0.460, indicating that this glassy alloy possesses very large glass forming ability and very high thermal stability.
With the addition of Si to replace some P, Pd40.5Ni40.5SixP19-x (x=0, 2.5, 5, 9.5, 14, and 19 in atomic number fraction) bulk glassy samples with the diameter of about 5 mm were successfully prepared by use of flux treatment and water quenching technology. With the increase of Si content, the glass forming ability of Pd40.5Ni40.5SixP19-x increases first for low Si content and then decreases for high Si content (Si≥9.5at%). The Pd40.5Ni40.5Si5P14 glassy alloy possesses the largest supercooled liquid region ΔT of 119 K, the largest reduced glass transition temperature of 0.621, and the largest γ parameter of 0.460, indicating that this glassy alloy possesses very large glass forming ability and very high thermal stability.
2010, vol. 17, no. 2, pp.
208-213.
https://doi.org/10.1007/s12613-010-0215-x
Abstract:
The unusual glass-forming ability (GFA) of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported. The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr48Cu36Ag8Al8 alloy. High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature. The bulk metallic glass matrix composites were prepared by introducing extra Ta particles into the Zr48Cu36Ag8Al8 melt. The composites consist of Ta particles homogenously distributed in the Zr48Cu36Al8Ag8 metallic glass matrix. The optimum content of Ta powder is 10at% for the composite with the highest plasticity, which shows a plastic strain of 31%.
The unusual glass-forming ability (GFA) of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported. The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr48Cu36Ag8Al8 alloy. High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature. The bulk metallic glass matrix composites were prepared by introducing extra Ta particles into the Zr48Cu36Ag8Al8 melt. The composites consist of Ta particles homogenously distributed in the Zr48Cu36Al8Ag8 metallic glass matrix. The optimum content of Ta powder is 10at% for the composite with the highest plasticity, which shows a plastic strain of 31%.
2010, vol. 17, no. 2, pp.
214-219.
https://doi.org/10.1007/s12613-010-0216-9
Abstract:
Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 bulk metallic glass matrix composites, containing β-Zr dendrites, were fabricated by Bridgman solidification at the withdrawal velocity of 1.0 mm/s through a temperature gradient of ∼45 K/mm. Subjected to the increasing compressive strain rates, the monotonic increasing and decreasing were obtained for the maximum strength and the fracture strain, respectively. The results show that high strain rate may induce the insufficient time for the interaction between shear bands and the crystalline phase, and early fracture occurs as a result. The fractographs are consistent with the mechanical properties, and the failure mode of the present Zr-based composites is in agreement with the frame of the ellipse criterion.
Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 bulk metallic glass matrix composites, containing β-Zr dendrites, were fabricated by Bridgman solidification at the withdrawal velocity of 1.0 mm/s through a temperature gradient of ∼45 K/mm. Subjected to the increasing compressive strain rates, the monotonic increasing and decreasing were obtained for the maximum strength and the fracture strain, respectively. The results show that high strain rate may induce the insufficient time for the interaction between shear bands and the crystalline phase, and early fracture occurs as a result. The fractographs are consistent with the mechanical properties, and the failure mode of the present Zr-based composites is in agreement with the frame of the ellipse criterion.
2010, vol. 17, no. 2, pp.
220-224.
https://doi.org/10.1007/s12613-010-0217-8
Abstract:
Samples with the nominal stoichiometry Li1.05Cr0.1Mn1.9O4-zFz (z=0, 0.05, 0.1, 0.15, and 0.2) were synthesized via the solid-state reaction method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge/discharge, and slow rate cyclic voltammetry (SSCV) techniques. The results show that the pure spinel phase indexed to Fd3m can be obtained when z=0, 0.05, and 0.1. The substitution of F for O with z≤0.1 contributes to the increase of initial capacity compared with Li1.05Cr0.1Mn1.9O4 spinels. However, when the F-dopant content is designed to be 0.15 and 0.2, the Li1.05Cr0.1Mn1.9O4-zFz samples deliver relatively low capacity and poor cycling properties at 55℃.
Samples with the nominal stoichiometry Li1.05Cr0.1Mn1.9O4-zFz (z=0, 0.05, 0.1, 0.15, and 0.2) were synthesized via the solid-state reaction method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge/discharge, and slow rate cyclic voltammetry (SSCV) techniques. The results show that the pure spinel phase indexed to Fd3m can be obtained when z=0, 0.05, and 0.1. The substitution of F for O with z≤0.1 contributes to the increase of initial capacity compared with Li1.05Cr0.1Mn1.9O4 spinels. However, when the F-dopant content is designed to be 0.15 and 0.2, the Li1.05Cr0.1Mn1.9O4-zFz samples deliver relatively low capacity and poor cycling properties at 55℃.
2010, vol. 17, no. 2, pp.
225-228.
https://doi.org/10.1007/s12613-010-0218-7
Abstract:
YVO4:Er3+, Yb3+ with varying Yb3+ concentrations were prepared by a precipitation method. The results of X-ray diffraction (XRD) show that all the samples have a tetragonal zircon structure; the calculated average crystallite sizes are in the range of 14–22 nm. The lattice constants and cell volume of the samples decrease slightly with the increase in Yb3+ concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green emission is observed, which is attributed to the 2H11/2 → 4I15/2 and 4S3/2→4I15/2 transitions of Er3+, and the red emission peaks in 650–675 nm can be ignored. The emission intensity for the sample depends on the Yb3+ concentration. These results reveal that the upconversion processes of YVO4:Er3+, Yb3+ are related to the structure and the doping Yb3+ concentration of the sample.
YVO4:Er3+, Yb3+ with varying Yb3+ concentrations were prepared by a precipitation method. The results of X-ray diffraction (XRD) show that all the samples have a tetragonal zircon structure; the calculated average crystallite sizes are in the range of 14–22 nm. The lattice constants and cell volume of the samples decrease slightly with the increase in Yb3+ concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green emission is observed, which is attributed to the 2H11/2 → 4I15/2 and 4S3/2→4I15/2 transitions of Er3+, and the red emission peaks in 650–675 nm can be ignored. The emission intensity for the sample depends on the Yb3+ concentration. These results reveal that the upconversion processes of YVO4:Er3+, Yb3+ are related to the structure and the doping Yb3+ concentration of the sample.
2010, vol. 17, no. 2, pp.
229-233.
https://doi.org/10.1007/s12613-010-0219-6
Abstract:
The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers. In the antiferromagnetic coupled [Pt(0.5 nm)/Co(0.4 nm)]n /NiO(1.1 nm)/[Co(0.4 nm)/Pt(0.5 nm)]n multilayers with perpendicular anisotropy, the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers. In demagnetized states, relatively shifted domain walls in the two Co/Pt multilayers are observed, with net ferromagnetic stripes formed between them for the repetition number n less than 5, and the stripe width decreases with the increase of n. The occurrence of these features can be attributed to the competition between the interlayer coupling and magnetostatic energies.
The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers. In the antiferromagnetic coupled [Pt(0.5 nm)/Co(0.4 nm)]n /NiO(1.1 nm)/[Co(0.4 nm)/Pt(0.5 nm)]n multilayers with perpendicular anisotropy, the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers. In demagnetized states, relatively shifted domain walls in the two Co/Pt multilayers are observed, with net ferromagnetic stripes formed between them for the repetition number n less than 5, and the stripe width decreases with the increase of n. The occurrence of these features can be attributed to the competition between the interlayer coupling and magnetostatic energies.
2010, vol. 17, no. 2, pp.
234-240.
https://doi.org/10.1007/s12613-010-0220-0
Abstract:
Spark plasma sintering was used to fabricate Al/diamond composites. The effect of sintering temperature on the microstructure and thermal conductivity (TC) of the composites was investigated with the combination of experimental results and theoretical analysis. The composite sintered at 550℃ shows high relative density and strong interfacial bonding, whereas the composites sintered at lower (520℃) and higher (580–600℃) temperatures indicate no interfacial bonding and poor interfacial bonding, respectively. High relative density and strong interfacial bonding can maximize the thermal conductivity of Al/diamond composites, and taking both effects of particle shape and inhomogeneous interfacial thermal conductance into consideration can give a fairly good prediction of composites’ thermal conduction properties.
Spark plasma sintering was used to fabricate Al/diamond composites. The effect of sintering temperature on the microstructure and thermal conductivity (TC) of the composites was investigated with the combination of experimental results and theoretical analysis. The composite sintered at 550℃ shows high relative density and strong interfacial bonding, whereas the composites sintered at lower (520℃) and higher (580–600℃) temperatures indicate no interfacial bonding and poor interfacial bonding, respectively. High relative density and strong interfacial bonding can maximize the thermal conductivity of Al/diamond composites, and taking both effects of particle shape and inhomogeneous interfacial thermal conductance into consideration can give a fairly good prediction of composites’ thermal conduction properties.
2010, vol. 17, no. 2, pp.
241-245.
https://doi.org/10.1007/s12613-010-0221-z
Abstract:
The effects of charging and outgassing on the friction and wear of Ni-P amorphous and nanocrystalline coatings were studied under ambient humidity and temperature. The results indicate that hydrogen charging can greatly decrease the volume loss during friction and increase the wear durability. However, the wear durability can be restored after outgassing. There are many cracks on the brittle nanocrystalline before charging, and no crack appears after charging, but there are only a few cracks on the outgassed sample. This indicates that hydrogen charging can inhibit the crack formation during friction for the brittle Ni-P nanocrystalline. For the charged sample, after the surface layer was removed by polishing, the wear track and the friction coefficient are consistent with those of an uncharged sample. The friction coefficient of the charged amorphous coating is very small within the first 140 s and then increases suddenly to the value corresponding to the uncharged sample. The absorbed surface layer lubricates the surface, reduces the friction coefficient, and improves the wear durability.
The effects of charging and outgassing on the friction and wear of Ni-P amorphous and nanocrystalline coatings were studied under ambient humidity and temperature. The results indicate that hydrogen charging can greatly decrease the volume loss during friction and increase the wear durability. However, the wear durability can be restored after outgassing. There are many cracks on the brittle nanocrystalline before charging, and no crack appears after charging, but there are only a few cracks on the outgassed sample. This indicates that hydrogen charging can inhibit the crack formation during friction for the brittle Ni-P nanocrystalline. For the charged sample, after the surface layer was removed by polishing, the wear track and the friction coefficient are consistent with those of an uncharged sample. The friction coefficient of the charged amorphous coating is very small within the first 140 s and then increases suddenly to the value corresponding to the uncharged sample. The absorbed surface layer lubricates the surface, reduces the friction coefficient, and improves the wear durability.
2010, vol. 17, no. 2, pp.
246-250.
https://doi.org/10.1007/s12613-010-0222-y
Abstract:
The Mo substrate with Zr interlayer, namely composite substrate, was employed to solve the problem of crack formation in the freestanding diamond film deposition. Freestanding diamond films deposited on the composite substrates by the direct current arc plasma jet chemical vapor deposition (CVD) method were investigated with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. In addition, the stress distribution during the large area freestanding diamond film deposition on the composite substrate was analyzed based on the finite element model ANSYS. The results reveal that Zr interlayer can be easily destroyed during the post-deposition cooling process, which is helpful for stress release and crack avoiding in diamond films.
The Mo substrate with Zr interlayer, namely composite substrate, was employed to solve the problem of crack formation in the freestanding diamond film deposition. Freestanding diamond films deposited on the composite substrates by the direct current arc plasma jet chemical vapor deposition (CVD) method were investigated with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. In addition, the stress distribution during the large area freestanding diamond film deposition on the composite substrate was analyzed based on the finite element model ANSYS. The results reveal that Zr interlayer can be easily destroyed during the post-deposition cooling process, which is helpful for stress release and crack avoiding in diamond films.
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