An environmentally friendly method for synthesizing a dawsonite conversion film was developed to improve the corrosion resistance of AZ31 Mg alloy. The film was prepared by two steps： the AZ31 alloy was first immerse...An environmentally friendly method for synthesizing a dawsonite conversion film was developed to improve the corrosion resistance of AZ31 Mg alloy. The film was prepared by two steps： the AZ31 alloy was first immersed in an Al 2 （SO 4 ） 3 solution venting CO 2 gas to form a precursor film, and then the precursor film was treated in a Na 2 CO 3 solution dissolved with Al to obtain the dawsonite film. The surface morphology of the conversion film was observed with an environmental scanning electronic microscope. The chemical composition of the conversion film was analyzed by energy dispersive X-ray spectroscopy and X-ray diffractometry. Electrochemical and immersion tests were carried out to evaluate the protection effect of the conversion film on AZ31 alloy. There are some network-like cracks on the surface of the film. The conversion film is mainly composed of dawsonite NaAlCO 3 （OH） 2 , Al（OH） 3 and Al 5 （OH） 13 （CO 3 ）·5H 2 O, which can increase the corrosion potential and reduce the corrosion current density of the Mg substrate. After immersion tests, the film almost keeps intact, except for the localized narrow areas with several corrosion pits, while the bare material undergoes serious general corrosion. It is indicated that the dawsonite film can provide good protection to the magnesium alloy.展开更多
Fibrous activated alumina is widely applied in catalysts,adsorbents,and composite materials.This work presents a green approach in preparing the fibrous activated Al_(2)O_(3) with high purity and specific surface area...Fibrous activated alumina is widely applied in catalysts,adsorbents,and composite materials.This work presents a green approach in preparing the fibrous activated Al_(2)O_(3) with high purity and specific surface area through multistep phase transformation of aluminum-bearing substances using intermediate dawsonite as a template.Thermodynamic calculations and experimental results show that increasing the concentration of Na_(2)CO_(3) and(NH_(4))_(2)CO_(3) is remarkably beneficial to the formation of dawsonite and ammonium aluminum carbonate hydroxide,respectively.Based on determination of dissolution and precipitation mechanism,the ultrafine granular gibbsite is converted to the uniform fibrous dawsonite with a ratio of length to diameter over 50,and the fibrous dawsonite changes into the long fibrous ammonium aluminum carbonate hydroxide with a ratio of length to diameter is about 80 in above 70 g/L(NH_(4))_(2)CO_(3) solution.Furthermore,the activated alumina remains fibrous morphology after roasting ammonium aluminum carbonate hydroxide at a slow heating rate,plentiful open mesopore and weak aggregation of particles,which contributes to the high specific surface area of 159.37 m^(2)/g at 1273 K for the activated alumina.The complete transformation of dawsonite to ammonium aluminum carbonate hydroxide and high specific surface area contribute to the purity of the activated fibrous alumina above 99.9%with low Na and Fe content.展开更多
Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandston...Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.展开更多
Dawsonite, NaAtCO3 （OH）2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney （BGS） basin system in Australia. The origin of dawsonite is emphatically cont...Dawsonite, NaAtCO3 （OH）2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney （BGS） basin system in Australia. The origin of dawsonite is emphatically contrasted and analyzed through stable isotopic composition. Dawsonite δ^13C values ranging from -4. 0 × 10 -3 to 4. 1 × 10 -3 are remarkably consistent through the BGS basin system. The calculated 813C values of CO2 gas in isotopic equilibrium with dawsonite range from - 11.3 × 10 -3 to -4. 6 × 10 -3. These values indicate carbon of dawsonite came from inorganic CO2 gas accompanied by magmatie activity. In Hailaer Basin, the Dawsonite δ^13C values ranging from -4. 64×10 -3 to 2. 12 × 10 -3 are also consistent. The calculated δ^13 C values of CO2 gas in isotopic equilibrium with dawsonite range from - 11.82 × 10 -3 to -5. 11 ×10 -3. According to the coincidence of dawsonite-bearing well and CO2 gas well with mantle source, lying along deep fracture within or adjacent to Yanshanian granite, it is concluded that CO2 gas forming dawsonite is derived from mantle related to magmatie process during the Yanshanian. A little biologic origin carbon owing to petroleum charging intervened when dawsonite formed.展开更多
Clay minerals, especially authigene kaolinite, are abundant in the dawsonite-bearing sandstone from the Gudian and Qian＇an regions in the southern Songliao Basin. The relationship between dawsonite and kaolinite has ...Clay minerals, especially authigene kaolinite, are abundant in the dawsonite-bearing sandstone from the Gudian and Qian＇an regions in the southern Songliao Basin. The relationship between dawsonite and kaolinite has been investigated based on drilling data from 50 wells in the Jilin Oil Field and petrological cbaracteristics analyses on 23 core samples from the Gudian and Qian＇an regions. The study revealed a negative relationship between the content of dawsonite and kaolinite, suggesting that kaolinite was replaced by the dawsonite. Combined with thermodynamics and geochemical analysis published previously, it is concluded that kaolinite is unstable under CO2-rich environments and can transform into dawsonite.展开更多
The stability of dawsonite is an important factor affecting the feasibility evaluation of CO_(2)geological storage.In this paper,a series of experiments on the interaction of CO_(2)-water-dawsonite-bearing sandstone w...The stability of dawsonite is an important factor affecting the feasibility evaluation of CO_(2)geological storage.In this paper,a series of experiments on the interaction of CO_(2)-water-dawsonite-bearing sandstone were carried out under different CO_(2)pressures.Considering the dissolution morphology and element composition of dawsonite after the experiment and the fluid evolution in equilibrium with dawsonite,the corrosion mechanism of dawsonite led by CO_(2)partial pressure was discussed.The CO_(2)fugacity of the vapor phase in the system was calculated using the Peng-Robinson equation of state combined with the van der Waals 1-fluid mixing rule.The experimental results indicated that the thermodynamic stability of dawsonite increased with the increase of CO_(2)partial pressure and decreased with the increase of temperature.The temperature at which dawsonite dissolution occurred was higher at higher f_(CO_(2)).There were two different ways to reduce dawsonite’s stability:the transformation of constituent elements and crystal structure damage.Dawsonite undergoes component element transformation and crystal structure damage under different CO_(2)pressures with certain temperature limits.Based on the comparison of the corrosion temperature of dawsonite,three corrosion evolution models of dawsonite under low,medium,and high CO_(2)pressures were summarized.Under conditions of medium and low CO_(2)pressure,as the temperature continued to increase and exceeded its stability limit,the dawsonite crystal structure was corroded first.Then the constituent elements of dawsonite dissolved,and the transformation of dawsonite to gibbsite began.At high CO_(2)pressure,the constituent elements of dawsonite dissolved first with the increase of temperature,forming gibbsite,followed by the corrosion of crystalline structure.展开更多
基金Project(50901082)supported by the National Natural Science Foundation of China
文摘An environmentally friendly method for synthesizing a dawsonite conversion film was developed to improve the corrosion resistance of AZ31 Mg alloy. The film was prepared by two steps： the AZ31 alloy was first immersed in an Al 2 （SO 4 ） 3 solution venting CO 2 gas to form a precursor film, and then the precursor film was treated in a Na 2 CO 3 solution dissolved with Al to obtain the dawsonite film. The surface morphology of the conversion film was observed with an environmental scanning electronic microscope. The chemical composition of the conversion film was analyzed by energy dispersive X-ray spectroscopy and X-ray diffractometry. Electrochemical and immersion tests were carried out to evaluate the protection effect of the conversion film on AZ31 alloy. There are some network-like cracks on the surface of the film. The conversion film is mainly composed of dawsonite NaAlCO 3 （OH） 2 , Al（OH） 3 and Al 5 （OH） 13 （CO 3 ）·5H 2 O, which can increase the corrosion potential and reduce the corrosion current density of the Mg substrate. After immersion tests, the film almost keeps intact, except for the localized narrow areas with several corrosion pits, while the bare material undergoes serious general corrosion. It is indicated that the dawsonite film can provide good protection to the magnesium alloy.
基金Project(51874372)supported by the National Natural Science Foundation of China。
文摘Fibrous activated alumina is widely applied in catalysts,adsorbents,and composite materials.This work presents a green approach in preparing the fibrous activated Al_(2)O_(3) with high purity and specific surface area through multistep phase transformation of aluminum-bearing substances using intermediate dawsonite as a template.Thermodynamic calculations and experimental results show that increasing the concentration of Na_(2)CO_(3) and(NH_(4))_(2)CO_(3) is remarkably beneficial to the formation of dawsonite and ammonium aluminum carbonate hydroxide,respectively.Based on determination of dissolution and precipitation mechanism,the ultrafine granular gibbsite is converted to the uniform fibrous dawsonite with a ratio of length to diameter over 50,and the fibrous dawsonite changes into the long fibrous ammonium aluminum carbonate hydroxide with a ratio of length to diameter is about 80 in above 70 g/L(NH_(4))_(2)CO_(3) solution.Furthermore,the activated alumina remains fibrous morphology after roasting ammonium aluminum carbonate hydroxide at a slow heating rate,plentiful open mesopore and weak aggregation of particles,which contributes to the high specific surface area of 159.37 m^(2)/g at 1273 K for the activated alumina.The complete transformation of dawsonite to ammonium aluminum carbonate hydroxide and high specific surface area contribute to the purity of the activated fibrous alumina above 99.9%with low Na and Fe content.
基金supported by the National Natural Science Foundation of China(Nos.42072130,41872152).
文摘Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.
文摘Dawsonite, NaAtCO3 （OH）2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney （BGS） basin system in Australia. The origin of dawsonite is emphatically contrasted and analyzed through stable isotopic composition. Dawsonite δ^13C values ranging from -4. 0 × 10 -3 to 4. 1 × 10 -3 are remarkably consistent through the BGS basin system. The calculated 813C values of CO2 gas in isotopic equilibrium with dawsonite range from - 11.3 × 10 -3 to -4. 6 × 10 -3. These values indicate carbon of dawsonite came from inorganic CO2 gas accompanied by magmatie activity. In Hailaer Basin, the Dawsonite δ^13C values ranging from -4. 64×10 -3 to 2. 12 × 10 -3 are also consistent. The calculated δ^13 C values of CO2 gas in isotopic equilibrium with dawsonite range from - 11.82 × 10 -3 to -5. 11 ×10 -3. According to the coincidence of dawsonite-bearing well and CO2 gas well with mantle source, lying along deep fracture within or adjacent to Yanshanian granite, it is concluded that CO2 gas forming dawsonite is derived from mantle related to magmatie process during the Yanshanian. A little biologic origin carbon owing to petroleum charging intervened when dawsonite formed.
基金Supported by project of the National Science Foundation of China(Nos.41172091,40672074)
文摘Clay minerals, especially authigene kaolinite, are abundant in the dawsonite-bearing sandstone from the Gudian and Qian＇an regions in the southern Songliao Basin. The relationship between dawsonite and kaolinite has been investigated based on drilling data from 50 wells in the Jilin Oil Field and petrological cbaracteristics analyses on 23 core samples from the Gudian and Qian＇an regions. The study revealed a negative relationship between the content of dawsonite and kaolinite, suggesting that kaolinite was replaced by the dawsonite. Combined with thermodynamics and geochemical analysis published previously, it is concluded that kaolinite is unstable under CO2-rich environments and can transform into dawsonite.
基金The authors thank the editors and two anonymous reviewers for their careful check and helpful comments and modification of the manuscript.This study is financially supported by the National Natural Science Foundation of China(Grants Nos.42072130 and 41872152).
文摘The stability of dawsonite is an important factor affecting the feasibility evaluation of CO_(2)geological storage.In this paper,a series of experiments on the interaction of CO_(2)-water-dawsonite-bearing sandstone were carried out under different CO_(2)pressures.Considering the dissolution morphology and element composition of dawsonite after the experiment and the fluid evolution in equilibrium with dawsonite,the corrosion mechanism of dawsonite led by CO_(2)partial pressure was discussed.The CO_(2)fugacity of the vapor phase in the system was calculated using the Peng-Robinson equation of state combined with the van der Waals 1-fluid mixing rule.The experimental results indicated that the thermodynamic stability of dawsonite increased with the increase of CO_(2)partial pressure and decreased with the increase of temperature.The temperature at which dawsonite dissolution occurred was higher at higher f_(CO_(2)).There were two different ways to reduce dawsonite’s stability:the transformation of constituent elements and crystal structure damage.Dawsonite undergoes component element transformation and crystal structure damage under different CO_(2)pressures with certain temperature limits.Based on the comparison of the corrosion temperature of dawsonite,three corrosion evolution models of dawsonite under low,medium,and high CO_(2)pressures were summarized.Under conditions of medium and low CO_(2)pressure,as the temperature continued to increase and exceeded its stability limit,the dawsonite crystal structure was corroded first.Then the constituent elements of dawsonite dissolved,and the transformation of dawsonite to gibbsite began.At high CO_(2)pressure,the constituent elements of dawsonite dissolved first with the increase of temperature,forming gibbsite,followed by the corrosion of crystalline structure.
