Search2018 Vol. 25, No. 11
Display Method:
New testing methodology for the quantification of rock crushability:Compressive crushing value (CCV)
2018, vol. 25, no. 11, pp.
1227-1236.
https://doi.org/10.1007/s12613-018-1675-7
Abstract:
Crushing is a size reduction process that plays a key role in both mineral processing and crushing-screening plant design. Investigations on rock crushability have become an important issue in mining operations and the manufacture of industrial crusher equipment. The main objective of this research is to quantify the crushability of hard rocks based on their mineralogical and mechanical properties. For this purpose, the mineralogical, physical, and mechanical properties of various hard rocks were determined. A new compressive crushing value (CCV) testing methodology was proposed. The results obtained from CCV tests were compared with those from mineralogical inspections, rock strength as well as mechanical aggregate tests. Strong correlations were found between CCV and several rock and aggregate properties such as uniaxial compressive strength (UCS), the brittleness index (S20), and aggregate impact value (AIV). Furthermore, the relationship between the mineralogical properties of the rocks and their CCVs were established. It is concluded that the proposed testing methodology is simple and highly repeatable and could be utilized as a pre-design tool in the design stage of the crushing process for rock quarries.
Crushing is a size reduction process that plays a key role in both mineral processing and crushing-screening plant design. Investigations on rock crushability have become an important issue in mining operations and the manufacture of industrial crusher equipment. The main objective of this research is to quantify the crushability of hard rocks based on their mineralogical and mechanical properties. For this purpose, the mineralogical, physical, and mechanical properties of various hard rocks were determined. A new compressive crushing value (CCV) testing methodology was proposed. The results obtained from CCV tests were compared with those from mineralogical inspections, rock strength as well as mechanical aggregate tests. Strong correlations were found between CCV and several rock and aggregate properties such as uniaxial compressive strength (UCS), the brittleness index (S20), and aggregate impact value (AIV). Furthermore, the relationship between the mineralogical properties of the rocks and their CCVs were established. It is concluded that the proposed testing methodology is simple and highly repeatable and could be utilized as a pre-design tool in the design stage of the crushing process for rock quarries.
2018, vol. 25, no. 11, pp.
1237-1245.
https://doi.org/10.1007/s12613-018-1676-6
Abstract:
Taking the joint matching coefficient (JMC) which represents the contact area ratio of the joint in rock masses as the key parameter, a one-dimensional contacted interface model (CIM-JMC) was established in this study to describe the wave propagation across a single joint. According to this model, the reflected and transmitted waves at the joint were obtained, and the energy coefficients of reflection and transmission were calculated. Compared with the modified Split Hopkinson pressure bar (SHPB) experiment, it was validated by taking the incident wave of the SHPB test as the input condition in the CIM-JMC, and the reflected and transmitted waves across the joint were calculated by the model. The effects of four sets of JMCs (0.81, 0.64, 0.49, and 0.36) on the transmission and reflection of the stress wave propagation across the joint were analyzed and compared with the experimental results. It demonstrated that the values of CIM-JMC could represent both the transmission and reflection of the stress wave accurately when JMC > 0.5, but could relatively accurately represent the reflection rather than the transmission when JMC < 0.5. By contrasting energy coefficients of joints with different JMCs, it was revealed that energy dissipated sharply along the decrease of JMC when JMC > 0.5.
Taking the joint matching coefficient (JMC) which represents the contact area ratio of the joint in rock masses as the key parameter, a one-dimensional contacted interface model (CIM-JMC) was established in this study to describe the wave propagation across a single joint. According to this model, the reflected and transmitted waves at the joint were obtained, and the energy coefficients of reflection and transmission were calculated. Compared with the modified Split Hopkinson pressure bar (SHPB) experiment, it was validated by taking the incident wave of the SHPB test as the input condition in the CIM-JMC, and the reflected and transmitted waves across the joint were calculated by the model. The effects of four sets of JMCs (0.81, 0.64, 0.49, and 0.36) on the transmission and reflection of the stress wave propagation across the joint were analyzed and compared with the experimental results. It demonstrated that the values of CIM-JMC could represent both the transmission and reflection of the stress wave accurately when JMC > 0.5, but could relatively accurately represent the reflection rather than the transmission when JMC < 0.5. By contrasting energy coefficients of joints with different JMCs, it was revealed that energy dissipated sharply along the decrease of JMC when JMC > 0.5.
2018, vol. 25, no. 11, pp.
1246-1255.
https://doi.org/10.1007/s12613-018-1677-5
Abstract:
Although transport in porous media under the influence of chemistry and temperature is a common phenomenon, the dissolution and internal structure evolution of glauberite during in-situ mining have been unique and challenging. This uniqueness indicates the complexity of mineral dissolutions, whereas the challenge represents the characterization of pore development and evolution during the dissolution processes. To investigate the microstructure development of glauberite under the influence of chemistry and temperature, experimental studies were performed with fine cuboid specimens of 4 mm×4 mm×9 mm soaked in solutions of different concentrations (fresh water, half-saturated, and saturated brine). The evolutions of internal structures were monitored through a micro computed tomography system. The statistical analysis indicated that the concentration and temperature of solutions significantly influenced the evolutions of pore size, porosity, and specific surface area of glauberite. The results showed that the increase in the rates of pore size, porosity, and specific surface area declined with time when glauberite was saturated in fresh water. The main reason for pore parameter variation is the differential concentration of solution. However, in the half-saturated and saturated solutions, the increase in rate increased with time. These observations suggest that the chloride ions contained in the saline solution could facilitate the dissolution of glauberite, whereas the existence of salt effect could contribute to the dissolution of calcium sulfate. Compared with the results at 20℃ and 65℃, the studied parameters of glauberite have dramatically decreased when the mineral was soaked in the solutions at high temperature (95℃). This function was most striking in fresh water. The dissolution of glauberite soaked in fresh water or half-saturated brine solution was conditioned by the temperature and solution concentration. However, the dissolution of glauberite was less influenced by temperature at high concentrations. These findings may feature significant implication for the effective recovery of mineral resources by in-situ solution mining method.
Although transport in porous media under the influence of chemistry and temperature is a common phenomenon, the dissolution and internal structure evolution of glauberite during in-situ mining have been unique and challenging. This uniqueness indicates the complexity of mineral dissolutions, whereas the challenge represents the characterization of pore development and evolution during the dissolution processes. To investigate the microstructure development of glauberite under the influence of chemistry and temperature, experimental studies were performed with fine cuboid specimens of 4 mm×4 mm×9 mm soaked in solutions of different concentrations (fresh water, half-saturated, and saturated brine). The evolutions of internal structures were monitored through a micro computed tomography system. The statistical analysis indicated that the concentration and temperature of solutions significantly influenced the evolutions of pore size, porosity, and specific surface area of glauberite. The results showed that the increase in the rates of pore size, porosity, and specific surface area declined with time when glauberite was saturated in fresh water. The main reason for pore parameter variation is the differential concentration of solution. However, in the half-saturated and saturated solutions, the increase in rate increased with time. These observations suggest that the chloride ions contained in the saline solution could facilitate the dissolution of glauberite, whereas the existence of salt effect could contribute to the dissolution of calcium sulfate. Compared with the results at 20℃ and 65℃, the studied parameters of glauberite have dramatically decreased when the mineral was soaked in the solutions at high temperature (95℃). This function was most striking in fresh water. The dissolution of glauberite soaked in fresh water or half-saturated brine solution was conditioned by the temperature and solution concentration. However, the dissolution of glauberite was less influenced by temperature at high concentrations. These findings may feature significant implication for the effective recovery of mineral resources by in-situ solution mining method.
2018, vol. 25, no. 11, pp.
1256-1262.
https://doi.org/10.1007/s12613-018-1678-4
Abstract:
Hydrophobic flocculation pretreatment was performed to assess its effect on the recovery of fine cuprite in sulfidation-flotation. The results of the micro-flotation experiment showed that cuprite recovery is related to the particle size, and that an excessive content of fine particles (<18 μm) impacted the recovery of coarse particles. When hydrophobic flocculation pretreatment was used, the recovery of fine cuprite in sulfidation-flotation increased from 60.3% to 86.3% under optimum conditions (pH 9.5; sodium oleate concentration, 2×10-4 mol·L-1; stirring time, 6 min; stirring speed, 1600 r·min-1). The laser particle size analysis and optical microscopy results indicate that hydrophobic flocculation pretreatment effectively reduces the content of fine cuprite, and augments the apparent particle size in the pulp. We performed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and extended DLVO theory calculations to further support the interpretation of the results.
Hydrophobic flocculation pretreatment was performed to assess its effect on the recovery of fine cuprite in sulfidation-flotation. The results of the micro-flotation experiment showed that cuprite recovery is related to the particle size, and that an excessive content of fine particles (<18 μm) impacted the recovery of coarse particles. When hydrophobic flocculation pretreatment was used, the recovery of fine cuprite in sulfidation-flotation increased from 60.3% to 86.3% under optimum conditions (pH 9.5; sodium oleate concentration, 2×10-4 mol·L-1; stirring time, 6 min; stirring speed, 1600 r·min-1). The laser particle size analysis and optical microscopy results indicate that hydrophobic flocculation pretreatment effectively reduces the content of fine cuprite, and augments the apparent particle size in the pulp. We performed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and extended DLVO theory calculations to further support the interpretation of the results.
2018, vol. 25, no. 11, pp.
1263-1274.
https://doi.org/10.1007/s12613-018-1679-3
Abstract:
Mechanical activation processes on ilmenite concentrate were performed in three different energy levels. Iron powder as a reducing agent was added to ilmenite in the milling stage and the mechanically activated mixture was subjected to acid leaching. The leaching experiments were designed using the Taguchi method, and the optimum ranges were obtained. Furthermore, response surface methodology (RSM) was used to optimize the critical parameters in the leaching system to achieve the highest titanium (Ti) leachability. Based on the inductively coupled plasma-optical emission spectrometry (ICP-OES) results, maximum leaching recovery of Ti (80%) was obtained using activated Ti concentrates at a medium activation energy level, which is calculated to be 25.38 kJ/g, using 15vol% hydrochloric acid (HCl), a temperature of 70℃, leaching time of 3 h, and a solid-to-liquid ratio of 0.05 g·mL-1. Intensifying the milling energy from a low to high level led to a decrease in the mean crystallite size and also structure homogenization at the high energy level. According to the transmission electron microscopy (TEM) images, the mean grain size of the ilmenite/Fe nanocomposite was about 30 nm at the medium energy level sample. Finally, solvent extraction by tributyl phosphate (TBP) was performed on the leach liquor to separate dissolved Fe (the major impurity) from Ti, which led to 83% extraction recovery of Ti.
Mechanical activation processes on ilmenite concentrate were performed in three different energy levels. Iron powder as a reducing agent was added to ilmenite in the milling stage and the mechanically activated mixture was subjected to acid leaching. The leaching experiments were designed using the Taguchi method, and the optimum ranges were obtained. Furthermore, response surface methodology (RSM) was used to optimize the critical parameters in the leaching system to achieve the highest titanium (Ti) leachability. Based on the inductively coupled plasma-optical emission spectrometry (ICP-OES) results, maximum leaching recovery of Ti (80%) was obtained using activated Ti concentrates at a medium activation energy level, which is calculated to be 25.38 kJ/g, using 15vol% hydrochloric acid (HCl), a temperature of 70℃, leaching time of 3 h, and a solid-to-liquid ratio of 0.05 g·mL-1. Intensifying the milling energy from a low to high level led to a decrease in the mean crystallite size and also structure homogenization at the high energy level. According to the transmission electron microscopy (TEM) images, the mean grain size of the ilmenite/Fe nanocomposite was about 30 nm at the medium energy level sample. Finally, solvent extraction by tributyl phosphate (TBP) was performed on the leach liquor to separate dissolved Fe (the major impurity) from Ti, which led to 83% extraction recovery of Ti.
2018, vol. 25, no. 11, pp.
1275-1285.
https://doi.org/10.1007/s12613-018-1680-x
Abstract:
AgSnO2 electrical contact materials doped with Bi2O3, La2O3, and TiO2 were successfully fabricated by the powder metallurgy method under different initial sintering temperatures. The electrical conductivity, density, hardness, and contact resistance of the AgSnO2/Bi2O3, AgSnO2/La2O3, and AgSnO2/TiO2 contact materials were measured and analyzed. The arc-eroded surface morphologies of the doped AgSnO2 contact materials were investigated by scanning electron microscopy (SEM). The effects of the initial sintering temperature on the physical properties and electrical contact properties of the doped AgSnO2 contact materials were discussed. The results indicate that the physical properties can be improved and the contact resistance of the AgSnO2 contact materials can be substantially reduced when the materials are sintered under their optimal initial sintering temperatures.
AgSnO2 electrical contact materials doped with Bi2O3, La2O3, and TiO2 were successfully fabricated by the powder metallurgy method under different initial sintering temperatures. The electrical conductivity, density, hardness, and contact resistance of the AgSnO2/Bi2O3, AgSnO2/La2O3, and AgSnO2/TiO2 contact materials were measured and analyzed. The arc-eroded surface morphologies of the doped AgSnO2 contact materials were investigated by scanning electron microscopy (SEM). The effects of the initial sintering temperature on the physical properties and electrical contact properties of the doped AgSnO2 contact materials were discussed. The results indicate that the physical properties can be improved and the contact resistance of the AgSnO2 contact materials can be substantially reduced when the materials are sintered under their optimal initial sintering temperatures.
2018, vol. 25, no. 11, pp.
1286-1293.
https://doi.org/10.1007/s12613-018-1681-9
Abstract:
CoCrCuFeNi-TiO was prepared by arc melting of the pure elements and Ti2CO powder under an Ar atmosphere. Both CoCrCuFeNi and CoCrCuFeNi-TiO alloys are composed of a face-centered cubic (fcc) solid solution, whereas the alloys of CoCrCuFeNi-TiO are basically composed of an fcc solid solution and TiO crystals. The microstructures of CoCrCuFeNi-TiO are identified as dendrite and interdendrite structures such as CoCrCuFeNi. The morphology of TiO is identified as an equiaxed crystal with a small amount of added Ti2CO. By increasing the amount of Ti2CO added, the TiO content was dramatically increased and part of the equiaxed crystals changed to a dendrite structure. A test of the oxidation resistance demonstrates that the oxidation resistance of CoCrCuFeNi-TiO is better than that of CoCrCuFeNi. However, as the TiO content increases further, a corresponding decrease is observed in the oxidation resistance.
CoCrCuFeNi-TiO was prepared by arc melting of the pure elements and Ti2CO powder under an Ar atmosphere. Both CoCrCuFeNi and CoCrCuFeNi-TiO alloys are composed of a face-centered cubic (fcc) solid solution, whereas the alloys of CoCrCuFeNi-TiO are basically composed of an fcc solid solution and TiO crystals. The microstructures of CoCrCuFeNi-TiO are identified as dendrite and interdendrite structures such as CoCrCuFeNi. The morphology of TiO is identified as an equiaxed crystal with a small amount of added Ti2CO. By increasing the amount of Ti2CO added, the TiO content was dramatically increased and part of the equiaxed crystals changed to a dendrite structure. A test of the oxidation resistance demonstrates that the oxidation resistance of CoCrCuFeNi-TiO is better than that of CoCrCuFeNi. However, as the TiO content increases further, a corresponding decrease is observed in the oxidation resistance.
2018, vol. 25, no. 11, pp.
1294-1303.
https://doi.org/10.1007/s12613-018-1682-8
Abstract:
Dissimilar joints comprised of copper-nickel and steel alloys are a challenge for manufacturers in modern industries, as these metals are not thermomechanically or chemically well matched. The present study investigated the effects of tool rotational speed and linear speed on the microstructure and mechanical properties of friction stir-welded C71000 copper-nickel and 340 stainless steel alloys using a tungsten carbide tool with a cylindrical pin. The results indicated that a rotational-to-linear speed ratio of 12.5 r/mm did not cause any macro defects, whereas some tunneling defects and longitudinal cracks were found at other ratios that were lower and higher. Furthermore, chromium carbide was formed on the grain boundaries of the 304 stainless steel near the shoulder zone and inside the joint zone, directing carbon and chromium penetration toward the grain boundaries. Tensile strength and elongation percentages were 84% and 65% of the corresponding values in the copper-nickel base metal, respectively.
Dissimilar joints comprised of copper-nickel and steel alloys are a challenge for manufacturers in modern industries, as these metals are not thermomechanically or chemically well matched. The present study investigated the effects of tool rotational speed and linear speed on the microstructure and mechanical properties of friction stir-welded C71000 copper-nickel and 340 stainless steel alloys using a tungsten carbide tool with a cylindrical pin. The results indicated that a rotational-to-linear speed ratio of 12.5 r/mm did not cause any macro defects, whereas some tunneling defects and longitudinal cracks were found at other ratios that were lower and higher. Furthermore, chromium carbide was formed on the grain boundaries of the 304 stainless steel near the shoulder zone and inside the joint zone, directing carbon and chromium penetration toward the grain boundaries. Tensile strength and elongation percentages were 84% and 65% of the corresponding values in the copper-nickel base metal, respectively.
2018, vol. 25, no. 11, pp.
1313-1319.
https://doi.org/10.1007/s12613-018-1684-6
Abstract:
Accelerated corrosion tests of the 7005-T4 aluminum alloy were conducted to determine a suitable service life prediction method by using alternating wet-dry cycles in three kinds of solutions. The morphology and composition analysis of the corrosion product revealed that slight corrosion occurred on the surfaces of the samples immersed in a 0.25wt% Na2S2O8 solution. However, pitting corrosion occurred on the surfaces of the samples immersed in a 3.5wt% NaCl solution, whereas exfoliation corrosion occurred on the surfaces of the samples immersed in a mixture of 0.25wt% Na2S2O8 and 3.5wt% NaCl solutions. A power exponent relationship was observed between the mass loss and exposure time of the 7005-T4 aluminum alloy immersed in the three kinds of solutions. In the mixture of 0.25wt% Na2S2O8 and 3.5wt% NaCl solutions, the mass loss of the aluminum alloy yielded the maximum value. Based on the calculation of the correlation coefficients, the alternating wet-dry procedure in a 3.5wt% NaCl solution could be used to predict the corrosion behavior of 7005-T4 aluminum alloy exposed in the atmosphere of Qingdao, China. The prediction model is as follows:T=104.28·t0.91, where T is the equivalent time and t is the exposure time.
Accelerated corrosion tests of the 7005-T4 aluminum alloy were conducted to determine a suitable service life prediction method by using alternating wet-dry cycles in three kinds of solutions. The morphology and composition analysis of the corrosion product revealed that slight corrosion occurred on the surfaces of the samples immersed in a 0.25wt% Na2S2O8 solution. However, pitting corrosion occurred on the surfaces of the samples immersed in a 3.5wt% NaCl solution, whereas exfoliation corrosion occurred on the surfaces of the samples immersed in a mixture of 0.25wt% Na2S2O8 and 3.5wt% NaCl solutions. A power exponent relationship was observed between the mass loss and exposure time of the 7005-T4 aluminum alloy immersed in the three kinds of solutions. In the mixture of 0.25wt% Na2S2O8 and 3.5wt% NaCl solutions, the mass loss of the aluminum alloy yielded the maximum value. Based on the calculation of the correlation coefficients, the alternating wet-dry procedure in a 3.5wt% NaCl solution could be used to predict the corrosion behavior of 7005-T4 aluminum alloy exposed in the atmosphere of Qingdao, China. The prediction model is as follows:T=104.28·t0.91, where T is the equivalent time and t is the exposure time.
2018, vol. 25, no. 11, pp.
1320-1328.
https://doi.org/10.1007/s12613-018-1685-5
Abstract:
A high-entropy alloy-ceramic gradient composite of TiC-TiB2/75vol% Al0.3CoCrFeNi was successfully prepared by combustion synthesis under an ultra-high gravity field, which is a low-cost method with high efficiency. The ceramic particles were gradient distributed in the Al0.3CoCrFeNi matrix, and the hardness of the composite material gradually decreased along the thickness direction. The anti-penetration performance of the gradient composites was simulated using the ANSYS/LS-DYNA explicit simulation program. The results demonstrate that the distribution of the ceramic particles strongly affected the mechanical properties and the anti-penetration performance of the composites. With the same total ceramic volume fraction, the gradient composites exhibit better anti-penetration performance than the corresponding ceramic-metal interlayer composites. The more uneven the ceramic distribution, the greater the elastic modulus and yield stress of the surface layer and, thus, the better the anti-penetration performance.
A high-entropy alloy-ceramic gradient composite of TiC-TiB2/75vol% Al0.3CoCrFeNi was successfully prepared by combustion synthesis under an ultra-high gravity field, which is a low-cost method with high efficiency. The ceramic particles were gradient distributed in the Al0.3CoCrFeNi matrix, and the hardness of the composite material gradually decreased along the thickness direction. The anti-penetration performance of the gradient composites was simulated using the ANSYS/LS-DYNA explicit simulation program. The results demonstrate that the distribution of the ceramic particles strongly affected the mechanical properties and the anti-penetration performance of the composites. With the same total ceramic volume fraction, the gradient composites exhibit better anti-penetration performance than the corresponding ceramic-metal interlayer composites. The more uneven the ceramic distribution, the greater the elastic modulus and yield stress of the surface layer and, thus, the better the anti-penetration performance.
2018, vol. 25, no. 11, pp.
1329-1334.
https://doi.org/10.1007/s12613-018-1686-4
Abstract:
Ag nanoparticles were sputter-deposited on ammonium persulfate ((NH4)2S2O8) powder to obtain (NH4)2S2O8-Ag powder, which was used to synthesize the HCl-doped polyaniline-Ag (HCl-PANI-Ag) composite via a polymerization procedure. The Ag nanoparticles were dispersed in the HCl-PANI matrix, and their sizes mainly ranged from 3 to 6 nm. The Ag nanoparticles did not affect the structure of emeraldine salt in the composite, and they increased the ordered crystalline regions in the HCl-PANI matrix. The HCl-PANI-Ag composite had a conductivity of (6.8 ±0.1) S/cm, which is about four times larger than that of the HCl-PANI. The charge transport mechanism in the composite is explained by the three-dimensional Mott variable-range hopping (3D-Mott-VRH).
Ag nanoparticles were sputter-deposited on ammonium persulfate ((NH4)2S2O8) powder to obtain (NH4)2S2O8-Ag powder, which was used to synthesize the HCl-doped polyaniline-Ag (HCl-PANI-Ag) composite via a polymerization procedure. The Ag nanoparticles were dispersed in the HCl-PANI matrix, and their sizes mainly ranged from 3 to 6 nm. The Ag nanoparticles did not affect the structure of emeraldine salt in the composite, and they increased the ordered crystalline regions in the HCl-PANI matrix. The HCl-PANI-Ag composite had a conductivity of (6.8 ±0.1) S/cm, which is about four times larger than that of the HCl-PANI. The charge transport mechanism in the composite is explained by the three-dimensional Mott variable-range hopping (3D-Mott-VRH).
2018, vol. 25, no. 11, pp.
1335-1343.
https://doi.org/10.1007/s12613-018-1687-3
Abstract:
A systematic investigation was carried out to observe the deposition rate of a diamond-like carbon (DLC) coating on two stainless steel substrates by chemical vapor deposition (CVD). The objective of this research is to study the deposition behavior of the DLC coating and its tribological properties in different combinations of methane (CH4) and nitrogen, which were used as precursor gases. The results reveal that the deposition rate increases with increasing CH4 content up to 50vol%. The hardness of the DLC-deposited layer also increases while the friction coefficient decreases with increasing CH4 gas content up to 50% in the precursor gas mixture.
A systematic investigation was carried out to observe the deposition rate of a diamond-like carbon (DLC) coating on two stainless steel substrates by chemical vapor deposition (CVD). The objective of this research is to study the deposition behavior of the DLC coating and its tribological properties in different combinations of methane (CH4) and nitrogen, which were used as precursor gases. The results reveal that the deposition rate increases with increasing CH4 content up to 50vol%. The hardness of the DLC-deposited layer also increases while the friction coefficient decreases with increasing CH4 gas content up to 50% in the precursor gas mixture.
2018, vol. 25, no. 11, pp.
1344-1353.
https://doi.org/10.1007/s12613-018-1688-2
Abstract:
zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole, were applied on AA2024 via a sol-gel method using the dip-coating technique. Next, the coatings were annealed at 150℃ after each dipping period. The phases and morphologies of the coatings were investigated using grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). The corrosion properties were evaluated using electrochemical methods, including polarization and electrochemical impedance techniques in 3.5wt% NaCl solution. The obtained results confirm the formation of homogeneous and crack free zirconia-benzotriazole-based nanostructured coatings. The average roughness values for zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole nanostructured coatings were 30, 8, and 6 nm, respectively. The presence of alumina as a stabilizer on zirconia coating was found to have a beneficial impact on the stability of the corrosion resistance for different immersion times. In fact, the addition of alumina resulted in the dominance of the healing behavior in competition with the corrosion process of zirconia-benzotriazole nanostructured coating.
zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole, were applied on AA2024 via a sol-gel method using the dip-coating technique. Next, the coatings were annealed at 150℃ after each dipping period. The phases and morphologies of the coatings were investigated using grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). The corrosion properties were evaluated using electrochemical methods, including polarization and electrochemical impedance techniques in 3.5wt% NaCl solution. The obtained results confirm the formation of homogeneous and crack free zirconia-benzotriazole-based nanostructured coatings. The average roughness values for zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole nanostructured coatings were 30, 8, and 6 nm, respectively. The presence of alumina as a stabilizer on zirconia coating was found to have a beneficial impact on the stability of the corrosion resistance for different immersion times. In fact, the addition of alumina resulted in the dominance of the healing behavior in competition with the corrosion process of zirconia-benzotriazole nanostructured coating.
2018, vol. 25, no. 11, pp.
1354-1361.
https://doi.org/10.1007/s12613-018-1689-1
Abstract:
By mixing preheated high-aluminum bronze powders with different amounts of Al2O3 powder, a low-pressure cold-sprayed coating was prepared and sprayed onto a Cr12MoV steel substrate. The hardness of the coating and the bonding strength between the coating and the substrate were tested with a HV-1000 microhardness tester and a mechanical universal testing machine. The surface microstructure, cross-section and tensile fracture surface of the coating were observed with a scanning electron microscope (SEM). Correspondingly, the influences of the preheat treatment temperature of the bronze powder and the Al2O3 content on the coating performance were investigated. The results indicate that the hardness of bronze powders decreased and the coating deposition rate increased after the preheating treatment of the bronze powder. The Al2O3 content in the mixed powders contributed to the deformation of bronze powders during the spraying process. This trend resulted in varied performance of the coating.
By mixing preheated high-aluminum bronze powders with different amounts of Al2O3 powder, a low-pressure cold-sprayed coating was prepared and sprayed onto a Cr12MoV steel substrate. The hardness of the coating and the bonding strength between the coating and the substrate were tested with a HV-1000 microhardness tester and a mechanical universal testing machine. The surface microstructure, cross-section and tensile fracture surface of the coating were observed with a scanning electron microscope (SEM). Correspondingly, the influences of the preheat treatment temperature of the bronze powder and the Al2O3 content on the coating performance were investigated. The results indicate that the hardness of bronze powders decreased and the coating deposition rate increased after the preheating treatment of the bronze powder. The Al2O3 content in the mixed powders contributed to the deformation of bronze powders during the spraying process. This trend resulted in varied performance of the coating.
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