Search2019 Vol. 26, No. 8
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2019, vol. 26, no. 8, pp.
925-937.
https://doi.org/10.1007/s12613-019-1809-6
Abstract:
Chemical oxygen generators (COGs) have been used worldwide in confined spaces as an emergency oxygen supply technology, mainly because they are independent and have a long shelf life. However, a number of challenges related to COGs remain unsolved, and a literature review of the current state of the technology is needed. First, the present article summarizes the basic information and applications of COGs, including their oxygen production mechanism, components, forming technology, and ignition system. Four current challenges encountered in applying COGs are discussed, along with the strategies adopted thus far to solve these problems, as found in the published literature. The literature survey reveals that, although much effort has been devoted to controlling the oxygen production rate and the heat output of COGs, the mechanism of producing toxic gases remains unclear and a reliable and safe ignition system has not been fully developed. Finally, future opportunities in the development of COGs are briefly listed.
Chemical oxygen generators (COGs) have been used worldwide in confined spaces as an emergency oxygen supply technology, mainly because they are independent and have a long shelf life. However, a number of challenges related to COGs remain unsolved, and a literature review of the current state of the technology is needed. First, the present article summarizes the basic information and applications of COGs, including their oxygen production mechanism, components, forming technology, and ignition system. Four current challenges encountered in applying COGs are discussed, along with the strategies adopted thus far to solve these problems, as found in the published literature. The literature survey reveals that, although much effort has been devoted to controlling the oxygen production rate and the heat output of COGs, the mechanism of producing toxic gases remains unclear and a reliable and safe ignition system has not been fully developed. Finally, future opportunities in the development of COGs are briefly listed.
2019, vol. 26, no. 8, pp.
938-945.
https://doi.org/10.1007/s12613-019-1810-0
Abstract:
To understand the migration mechanisms of phosphorus (P) during coal-based reduction, a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions. The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer (FE-EPMA) and using the basic principle of solid phase mass transfer, respectively. Experimental results showed that the P transferred from the slag to the metallic phase during reduction, and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface, the formation of Fe-P compounds at the slag-metal interface and P diffusing from the slag-metal interface to the metallic interior. The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases. The P content of the metallic phase increased with increasing reduction time and temperature, while that of the slag phase gradually decreased. The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed. P diffusion in the metallic phase was the controlling step of the P migration.
To understand the migration mechanisms of phosphorus (P) during coal-based reduction, a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions. The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer (FE-EPMA) and using the basic principle of solid phase mass transfer, respectively. Experimental results showed that the P transferred from the slag to the metallic phase during reduction, and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface, the formation of Fe-P compounds at the slag-metal interface and P diffusing from the slag-metal interface to the metallic interior. The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases. The P content of the metallic phase increased with increasing reduction time and temperature, while that of the slag phase gradually decreased. The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed. P diffusion in the metallic phase was the controlling step of the P migration.
2019, vol. 26, no. 8, pp.
946-952.
https://doi.org/10.1007/s12613-019-1804-y
Abstract:
The dissolution of copper and iron from chalcopyrite concentrate in the presence of ammonium persulfate (APS) and ammonium hydroxide was investigated under atmospheric leaching conditions. Experiments were designed by central composite design (CCD). Under the optimum leaching conditions ((NH4)2S2O8 concentration=328 g/L; NH4OH addition=16vol%; leaching temperature=321 K (48℃); leaching time=120 min; liquid-to-solid ratio=16; stirring speed=400 r/min), selective leaching was achieved. 98.14% of the copper was leached, whereas iron did not pass into the solution. X-ray diffraction analysis of the leaching residue showed that iron compounds were predominant. Given the leaching results, the fact that the leaching process does not include uneconomical leaching stages such as extended milling/mechanical activation or high pressures/temperatures, and the low copper dissolution conditions, the attained selective leaching yield may be remarkable.
The dissolution of copper and iron from chalcopyrite concentrate in the presence of ammonium persulfate (APS) and ammonium hydroxide was investigated under atmospheric leaching conditions. Experiments were designed by central composite design (CCD). Under the optimum leaching conditions ((NH4)2S2O8 concentration=328 g/L; NH4OH addition=16vol%; leaching temperature=321 K (48℃); leaching time=120 min; liquid-to-solid ratio=16; stirring speed=400 r/min), selective leaching was achieved. 98.14% of the copper was leached, whereas iron did not pass into the solution. X-ray diffraction analysis of the leaching residue showed that iron compounds were predominant. Given the leaching results, the fact that the leaching process does not include uneconomical leaching stages such as extended milling/mechanical activation or high pressures/temperatures, and the low copper dissolution conditions, the attained selective leaching yield may be remarkable.
2019, vol. 26, no. 8, pp.
953-962.
https://doi.org/10.1007/s12613-019-1824-7
Abstract:
Some basic properties of granules, including the granule size distribution, packed-bed permeability, and chemical composition of the adhering layer, were investigated in this study for four iron ore blends consisting of 5wt%, 25wt%, and 45wt% ultrafine magnetite and 25wt% ultrafine hematite concentrates. The effects of varying the sinter basicity (CaO/SiO2 mass ratio=1.4 to 2.2) and adding ultrafine concentrates on the variation of the adhering-layer composition and granule microstructure were studied. Moreover, the effect of adhering-layer compositional changes on sintering reactions was discussed in combination with pot sintering results of ore blends. Increasing sinter basicity led to an increase in the basicities of both the adhering layer and the fine part of the sinter mix, which were higher than the overall sinter basicity. When the sinter chemistry was fixed and fine Si-bearing materials (e.g., quartz sand) were used, increasing the amount of ultrafine ores in the ore blends tended to reduce the adhering-layer basicity and increase the SiO2 content in both the adhering layer and the fine part of the sinter mix, which will induce the formation of low-strength bonding phases and the deterioration of sinter strength. The adhering-layer composition in granules can be estimated in advance from the compositions of the -1 mm fractions of the raw materials.
Some basic properties of granules, including the granule size distribution, packed-bed permeability, and chemical composition of the adhering layer, were investigated in this study for four iron ore blends consisting of 5wt%, 25wt%, and 45wt% ultrafine magnetite and 25wt% ultrafine hematite concentrates. The effects of varying the sinter basicity (CaO/SiO2 mass ratio=1.4 to 2.2) and adding ultrafine concentrates on the variation of the adhering-layer composition and granule microstructure were studied. Moreover, the effect of adhering-layer compositional changes on sintering reactions was discussed in combination with pot sintering results of ore blends. Increasing sinter basicity led to an increase in the basicities of both the adhering layer and the fine part of the sinter mix, which were higher than the overall sinter basicity. When the sinter chemistry was fixed and fine Si-bearing materials (e.g., quartz sand) were used, increasing the amount of ultrafine ores in the ore blends tended to reduce the adhering-layer basicity and increase the SiO2 content in both the adhering layer and the fine part of the sinter mix, which will induce the formation of low-strength bonding phases and the deterioration of sinter strength. The adhering-layer composition in granules can be estimated in advance from the compositions of the -1 mm fractions of the raw materials.
2019, vol. 26, no. 8, pp.
963-972.
https://doi.org/10.1007/s12613-019-1813-x
Abstract:
The oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets (CVTP) with Cr2O3 addition were studied, and the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP with simulated coke oven gas (COG) injection were investigated. The results showed that the CS of the CVTP decreases and the porosity of the CVTP increases with increasing amount of Cr2O3 added. The Cr2O3 mainly exists in the form of (Cr, Fe)2O3 solid solution in the CVTP and as Fe-Cr in the reduced CVTP. The CS of the reduced CVTP increases and the RSI of the reduced CVTP decreases with increasing amount of Cr2O3 added. The limited aggregation and diffusion of metallic iron contribute to the formation of dense lamellar crystals, which leads to the slight decrease for reduction swelling behavior of reduced CVTP. This work provides a theoretical and technical basis for the utilization of CVTP and other Cr-bearing ores such as chromite with COG recycling technology.
The oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets (CVTP) with Cr2O3 addition were studied, and the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP with simulated coke oven gas (COG) injection were investigated. The results showed that the CS of the CVTP decreases and the porosity of the CVTP increases with increasing amount of Cr2O3 added. The Cr2O3 mainly exists in the form of (Cr, Fe)2O3 solid solution in the CVTP and as Fe-Cr in the reduced CVTP. The CS of the reduced CVTP increases and the RSI of the reduced CVTP decreases with increasing amount of Cr2O3 added. The limited aggregation and diffusion of metallic iron contribute to the formation of dense lamellar crystals, which leads to the slight decrease for reduction swelling behavior of reduced CVTP. This work provides a theoretical and technical basis for the utilization of CVTP and other Cr-bearing ores such as chromite with COG recycling technology.
2019, vol. 26, no. 8, pp.
973-982.
https://doi.org/10.1007/s12613-019-1812-y
Abstract:
Four bituminous coals and one anthracite were used in this study. On the basis of the similar volatile matter contents of the four bituminous coals, the effects of ash in coal on the microstructure, carbonaceous structure, and chemical composition of pulverized coal were studied. Thermogravimetric analysis was used to study the effect of the addition of anthracite on the combustibility of four different bituminous coals. The results showed that with the increase of ash content in pulverized coal, the microstructure of carbon particles in coal was not much different. However, the analysis results of Raman spectroscopy and X-ray diffraction pattern showed that as the ash content increased, the degree of graphitization of coal carbonaceous structure gradually decreased. The combustibility of the four bituminous coals were better than that of the anthracite. When bituminous coal and anthracite were mixed and burned, the combustibility of the mixed sample decreased as the ash content increased.
Four bituminous coals and one anthracite were used in this study. On the basis of the similar volatile matter contents of the four bituminous coals, the effects of ash in coal on the microstructure, carbonaceous structure, and chemical composition of pulverized coal were studied. Thermogravimetric analysis was used to study the effect of the addition of anthracite on the combustibility of four different bituminous coals. The results showed that with the increase of ash content in pulverized coal, the microstructure of carbon particles in coal was not much different. However, the analysis results of Raman spectroscopy and X-ray diffraction pattern showed that as the ash content increased, the degree of graphitization of coal carbonaceous structure gradually decreased. The combustibility of the four bituminous coals were better than that of the anthracite. When bituminous coal and anthracite were mixed and burned, the combustibility of the mixed sample decreased as the ash content increased.
2019, vol. 26, no. 8, pp.
983-991.
https://doi.org/10.1007/s12613-019-1814-9
Abstract:
Red mud is a type of highly alkaline waste residue produced in the process of alumina smelting by the Bayer process. Based on the idea of medium calcium content, solid wastes such as red mud and fly ash were used to prepare non-burnt bricks; and the mass ratio of CaO/SiO2 was selected in the range of 0.88-1.42. Mechanical properties and durability were investigated with a compressive strength test. X-ray diffractometry (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques were used to characterize the hydration characteristic. The environmental performance was analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP). The results indicated that the mechanical properties and the durability were optimal when the mass ratio of CaO/SiO2 was 1.23. The hydration products were mostly C-S-H gel, ettringite, Na4Ca(Si10Al16)O32·12H2O and Ca3Al2(SiO4)(OH)8. They were responsible for the strength development, and the CaO/SiO2 mass ratio of 1.23 had the best polymerized structure. The results of an environmental performance test showed that the heavy metals in the raw materials were well-solidified in the brick. Therefore, this paper provides an effective solution for use of solid wastes in building material.
Red mud is a type of highly alkaline waste residue produced in the process of alumina smelting by the Bayer process. Based on the idea of medium calcium content, solid wastes such as red mud and fly ash were used to prepare non-burnt bricks; and the mass ratio of CaO/SiO2 was selected in the range of 0.88-1.42. Mechanical properties and durability were investigated with a compressive strength test. X-ray diffractometry (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques were used to characterize the hydration characteristic. The environmental performance was analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP). The results indicated that the mechanical properties and the durability were optimal when the mass ratio of CaO/SiO2 was 1.23. The hydration products were mostly C-S-H gel, ettringite, Na4Ca(Si10Al16)O32·12H2O and Ca3Al2(SiO4)(OH)8. They were responsible for the strength development, and the CaO/SiO2 mass ratio of 1.23 had the best polymerized structure. The results of an environmental performance test showed that the heavy metals in the raw materials were well-solidified in the brick. Therefore, this paper provides an effective solution for use of solid wastes in building material.
2019, vol. 26, no. 8, pp.
992-998.
https://doi.org/10.1007/s12613-019-1821-x
Abstract:
In this study, for the first time, direct copper production from copper sulfide was carried out via direct electrochemical reduction method using inexpensive and stable molten borax electrolyte. The effects of current density (100-800 mA/cm2) and electrolysis time (15-90 min) on both the cathodic current efficiency and copper yield were systematically investigated in consideration of possible electrochemical/chemical reactions at 1200℃. The copper production yield reached 98.09% after 90 min of electrolysis at a current density of 600 mA/cm2. Direct metal production was shown to be possible with 6 kWh/kg energy consumption at a 600 mA/cm2 current density, at which the highest current efficiency (41%) was obtained. The suggested method can also be applied to metal/alloy production from single-and mixed-metal sulfides coming from primary production and precipitated sulfides, which are produced in the mining and metallurgical industries during treatment of process solutions or wastewaters.
In this study, for the first time, direct copper production from copper sulfide was carried out via direct electrochemical reduction method using inexpensive and stable molten borax electrolyte. The effects of current density (100-800 mA/cm2) and electrolysis time (15-90 min) on both the cathodic current efficiency and copper yield were systematically investigated in consideration of possible electrochemical/chemical reactions at 1200℃. The copper production yield reached 98.09% after 90 min of electrolysis at a current density of 600 mA/cm2. Direct metal production was shown to be possible with 6 kWh/kg energy consumption at a 600 mA/cm2 current density, at which the highest current efficiency (41%) was obtained. The suggested method can also be applied to metal/alloy production from single-and mixed-metal sulfides coming from primary production and precipitated sulfides, which are produced in the mining and metallurgical industries during treatment of process solutions or wastewaters.
2019, vol. 26, no. 8, pp.
999-1004.
https://doi.org/10.1007/s12613-019-1818-5
Abstract:
The effects of shot peening on the mechanical properties of steel 1070 were studied to enhance the material's properties and surface characteristics. In this study, pressure and exposure time were the main parameters governing surface hardness and surface roughness. The optimal time duration and pressure were determined after several experimental trials. Changes in hardness and surface roughness were monitored as the pressure of the shot and the exposure time were varied. Furthermore, the microstructure was evaluated by scanning electron microscopy (SEM) and the images were enhanced by image processing techniques to evaluate the surface changes. Pareto charts were constructed to estimate the effects of pressure and time on both surface hardness and surface roughness. The novelty of this study is the concentration on engine blades which are frequently used in aircrafts to determine the optimal time-pressure combination for shot peening to achieve suitable mechanical and surface properties. The results show that shot peening pressure (up to 482.6 kPa for 7 min) has positive effect on enhancing the surface and mechanical properties for steel 1070 blades; however, an increase in either pressure or time above that level adversely affected both surface hardness and surface roughness.
The effects of shot peening on the mechanical properties of steel 1070 were studied to enhance the material's properties and surface characteristics. In this study, pressure and exposure time were the main parameters governing surface hardness and surface roughness. The optimal time duration and pressure were determined after several experimental trials. Changes in hardness and surface roughness were monitored as the pressure of the shot and the exposure time were varied. Furthermore, the microstructure was evaluated by scanning electron microscopy (SEM) and the images were enhanced by image processing techniques to evaluate the surface changes. Pareto charts were constructed to estimate the effects of pressure and time on both surface hardness and surface roughness. The novelty of this study is the concentration on engine blades which are frequently used in aircrafts to determine the optimal time-pressure combination for shot peening to achieve suitable mechanical and surface properties. The results show that shot peening pressure (up to 482.6 kPa for 7 min) has positive effect on enhancing the surface and mechanical properties for steel 1070 blades; however, an increase in either pressure or time above that level adversely affected both surface hardness and surface roughness.
2019, vol. 26, no. 8, pp.
1005-1012.
https://doi.org/10.1007/s12613-019-1806-9
Abstract:
In the present work, the friction stir back extrusion (FSBE) process was used as a novel method for the fabrication of AA6063 aluminum alloy wire. Scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), tensile and hardness tests were performed. The FSBE via the rotational speed of 475 r/min resulted in fine equiaxed grains, and the mean grain size decreased from 179.0 μm to 15.5 μm due to the occurrence of dynamic recrystallization (DRX). Heat generated by the FSBE changed the size and volume fraction of the Mg2Si precipitated particles. The minimum particle size and maximum volume fraction obtained in the sample were processed by rotational speeds of 475 and 600 r/min, respectively. The 475-r/min sample had the maximum hardness value due to having the lowest grain size (i.e., 15.5 μm) and the presence of many fine Mg2Si precipitates in the aluminum matrix. With increasing rotational speed up to 600 r/min, the hardness decreased, owing to the growth of both grains and precipitates. The FSBE process with a rotational speed of 475 r/min increased the tensile strength (from 150 to 209 MPa) and ductility (from 21.0% to 30.2%) simultaneously.
In the present work, the friction stir back extrusion (FSBE) process was used as a novel method for the fabrication of AA6063 aluminum alloy wire. Scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), tensile and hardness tests were performed. The FSBE via the rotational speed of 475 r/min resulted in fine equiaxed grains, and the mean grain size decreased from 179.0 μm to 15.5 μm due to the occurrence of dynamic recrystallization (DRX). Heat generated by the FSBE changed the size and volume fraction of the Mg2Si precipitated particles. The minimum particle size and maximum volume fraction obtained in the sample were processed by rotational speeds of 475 and 600 r/min, respectively. The 475-r/min sample had the maximum hardness value due to having the lowest grain size (i.e., 15.5 μm) and the presence of many fine Mg2Si precipitates in the aluminum matrix. With increasing rotational speed up to 600 r/min, the hardness decreased, owing to the growth of both grains and precipitates. The FSBE process with a rotational speed of 475 r/min increased the tensile strength (from 150 to 209 MPa) and ductility (from 21.0% to 30.2%) simultaneously.
2019, vol. 26, no. 8, pp.
1013-1019.
https://doi.org/10.1007/s12613-019-1815-8
Abstract:
The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al-13Si-7.5Cu-1Mg alloy were investigated. The microstructures of alloys before and after conform processing and aging were compared by transmission electron microscopy and scanning electron microscopy, respectively. The results reveal that the primary phases were broken and refined by intense shear deformation during conform processing. After the conform-prepared Al-13Si-7.5Cu-1Mg alloy was subjected to solid-solution treatment at 494℃ for 1.5 h and aging at 180℃ for 4 h, its hardness improved from HBS 115.8 to HBS 152.5 and its ultimate tensile strength increased from 112.6 to 486.8 MPa. Its wear resistance was also enhanced. The factors leading to the enhanced strength, hardness, and wear resistance of the alloy were discussed in detail.
The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al-13Si-7.5Cu-1Mg alloy were investigated. The microstructures of alloys before and after conform processing and aging were compared by transmission electron microscopy and scanning electron microscopy, respectively. The results reveal that the primary phases were broken and refined by intense shear deformation during conform processing. After the conform-prepared Al-13Si-7.5Cu-1Mg alloy was subjected to solid-solution treatment at 494℃ for 1.5 h and aging at 180℃ for 4 h, its hardness improved from HBS 115.8 to HBS 152.5 and its ultimate tensile strength increased from 112.6 to 486.8 MPa. Its wear resistance was also enhanced. The factors leading to the enhanced strength, hardness, and wear resistance of the alloy were discussed in detail.
2019, vol. 26, no. 8, pp.
1020-1030.
https://doi.org/10.1007/s12613-019-1805-x
Abstract:
This paper describes an investigation of the effect of ZrO2 nanoparticles on the abrasive properties, crystalline texture developments, and tribocorrosion behavior of Ni-P nanostructured coatings. In the investigation, Ni-P and Ni-P-ZrO2 nanostructured coatings are deposited on St52 steel via the electroless method. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), cyclic-static polarization tests in 3.5wt% NaCl solution, the tribocorrosion test (by back-and-forth wear in electrochemical cell), and the microhardness test using the Vickers method were performed to characterize and analyze the deposited coatings. The results of this study showed that the addition of ZrO2 nanoparticles to the Ni-P electroless bath produced the following:a sharp increase in wear and hardness resistance, the change of the wear mechanism from sheet to adhesive mode, the reduction of pitting corrosion resistance, significant reduction in the tribocorrosion protective properties, change in the preferred orientation of the crystalline texture coating from (111) to (200), increase in the sedimentation rate during the deposit process, and a sharp increase in the thickness of the Ni-P nanostructured coatings.
This paper describes an investigation of the effect of ZrO2 nanoparticles on the abrasive properties, crystalline texture developments, and tribocorrosion behavior of Ni-P nanostructured coatings. In the investigation, Ni-P and Ni-P-ZrO2 nanostructured coatings are deposited on St52 steel via the electroless method. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), cyclic-static polarization tests in 3.5wt% NaCl solution, the tribocorrosion test (by back-and-forth wear in electrochemical cell), and the microhardness test using the Vickers method were performed to characterize and analyze the deposited coatings. The results of this study showed that the addition of ZrO2 nanoparticles to the Ni-P electroless bath produced the following:a sharp increase in wear and hardness resistance, the change of the wear mechanism from sheet to adhesive mode, the reduction of pitting corrosion resistance, significant reduction in the tribocorrosion protective properties, change in the preferred orientation of the crystalline texture coating from (111) to (200), increase in the sedimentation rate during the deposit process, and a sharp increase in the thickness of the Ni-P nanostructured coatings.
2019, vol. 26, no. 8, pp.
1031-1037.
https://doi.org/10.1007/s12613-019-1816-7
Abstract:
In the present work, mechanical alloying of a powder mixture of nickel and graphite (up to 15wt%) was carried out in an attrition mill under a nitrogen atmosphere. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The 15wt% graphite dissolved into the nickel (exceeding the negligible solid solubility in the nickel-carbon system), thereby forming a supersaturated solid solution of graphite in a nickel matrix. The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions. A three-step graphite dissolution mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the crystallite size (62 to 43 nm), lattice strain (0.12% to 0.3%), and lattice parameter (0.3533 to 0.3586 nm), which led to the formation of the supersaturated solid solution, were also evaluated and discussed.
In the present work, mechanical alloying of a powder mixture of nickel and graphite (up to 15wt%) was carried out in an attrition mill under a nitrogen atmosphere. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The 15wt% graphite dissolved into the nickel (exceeding the negligible solid solubility in the nickel-carbon system), thereby forming a supersaturated solid solution of graphite in a nickel matrix. The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions. A three-step graphite dissolution mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the crystallite size (62 to 43 nm), lattice strain (0.12% to 0.3%), and lattice parameter (0.3533 to 0.3586 nm), which led to the formation of the supersaturated solid solution, were also evaluated and discussed.
2019, vol. 26, no. 8, pp.
1038-1046.
https://doi.org/10.1007/s12613-019-1807-8
Abstract:
The corrosion resistance behavior of a highly dispersed MgO-MgAl2O4-ZrO2 composite refractory material is examined by testing with high-basicity and low-basicity RH (Ruhrstahl-Hereaeus) slags. The composite material exhibits greater resistance to the RH slags than the traditional MgO-Cr2O3 composite, MgO-ZrO2 composite, and MgO-MgAl2O4-ZrO2 composite. On the basis of the microstructural analysis and mechanisms calculations, the corrosion resistance behavior of the MgO-MgAl2O4-ZrO2 composite is attributable to its highly dispersed structure, which helps protect the high activity of ZrO2. When in contact with the slag, ZrO2 reacts with CaO to form the stable phase CaZrO3, which protects MgAl2O4 against corrosion, thereby enhancing the corrosion resistance of the composite.
The corrosion resistance behavior of a highly dispersed MgO-MgAl2O4-ZrO2 composite refractory material is examined by testing with high-basicity and low-basicity RH (Ruhrstahl-Hereaeus) slags. The composite material exhibits greater resistance to the RH slags than the traditional MgO-Cr2O3 composite, MgO-ZrO2 composite, and MgO-MgAl2O4-ZrO2 composite. On the basis of the microstructural analysis and mechanisms calculations, the corrosion resistance behavior of the MgO-MgAl2O4-ZrO2 composite is attributable to its highly dispersed structure, which helps protect the high activity of ZrO2. When in contact with the slag, ZrO2 reacts with CaO to form the stable phase CaZrO3, which protects MgAl2O4 against corrosion, thereby enhancing the corrosion resistance of the composite.
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