An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has be...An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.展开更多
There are many brands of activated alumina powders in the market and the products from different manufacturers exist subtle differences. In this work, four brands of activated alumina powder which are the mainstream p...There are many brands of activated alumina powders in the market and the products from different manufacturers exist subtle differences. In this work, four brands of activated alumina powder which are the mainstream products in China with the same marked particle size of 2-3 μm were added to corundum castables to investigate the effect of different activated alumina powder on properties of corundum castables. It is found that the multi-peak distribution, round-shape particle,low impurities content of alumina powder are of great benefit to the improvement of the overall performance of castables.Obvious CA6 frame structure formed in castables matrix is conductive to improving the thermal shock resistance and high temperature strength of castables. One kind of domestic alumina micropowder studied in this work has good application value and prospect in corundum castables because of the excellent comprehensive performance.展开更多
To satisfy the requirements of alumina castables in specific environment and enhance their properties,alumina castables were prepared using tabular alumina,various alumina powders(07RAL,15RA,22RABL,40CA,99-20um,and 99...To satisfy the requirements of alumina castables in specific environment and enhance their properties,alumina castables were prepared using tabular alumina,various alumina powders(07RAL,15RA,22RABL,40CA,99-20um,and 99-325mesh),and calcium aluminate cement as main raw materials,and heat treating at 110,1000,1600℃,respectively.Their flowability and physical properties were tested,and the morphology was researched.The results show that compared with calcined alumina and tabular alumina powders,reactive alumina has higher specific surface area and better filling performance leading to lower water demand and higher viscosity,and the castables prepared with reactive alumina have higher CCS and CMOR after heat treating at 110,1000 and 1600℃as well as lower PLC than those with calcined alumina and tabular alumina powders.展开更多
To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al_(2)O_(3) micropowder),the fine powders with the median diameter of 50,30,10,and 5 pm,respecti...To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al_(2)O_(3) micropowder),the fine powders with the median diameter of 50,30,10,and 5 pm,respectively,were obtained by grinding industrial alumina powder(the median diameter of 80 pm),and the active alumina micropowders were prepared by firing the industrial alumina powders before and after grinding at 1320℃ for 5 h.The effect of the particle size of the industrial alumina powder on the microstructure and properties of the active alumina micropowder was researched.The results indicate that the initial particle size of the industrial alumina powder has a great influence on the grain morphology of the active alumina micropowder;when the median diameter is larger than 30 pm,the α-Al_(2)O_(3) grains show wormlike aggregates state after calcination and when it is around or less than 10 pm,the α-Al_(2)O_(3) are round,spherical and well dispersed grains with the particle size of 0.3-1.0 pm.With the initial particle size of the industrial alumina powder decreasing,the α-Al_(2)O_(3) phase transition rate increases and the true density gradually increases;moreover,the α-Al_(2)O_(3) powder shows better dispersity and flowability.展开更多
A zirconia alumina powder with a near spherical shape and an average size of 0.1～0.2 μm was prepared by co precipitation. XRD analysis shows that α Al 2O 3 phase may be directly transformed from amorphous in calcin...A zirconia alumina powder with a near spherical shape and an average size of 0.1～0.2 μm was prepared by co precipitation. XRD analysis shows that α Al 2O 3 phase may be directly transformed from amorphous in calcining the hydroxide composite. The ZrO 2 Al 2O 3 composite ceramics manufactured from this powder has the maximum fracture toughness of 9 MPa·m -1/2 at 15% ZrO 2 and 740 MPa fracture strength at 5% ZrO 2. Zirconia grains about 1 μm in diameter are dispersed uniformly in the alumina ceramic matrix.展开更多
The microstructures of nanosized alumina powders prepared by sol gel routine were systematically studied with transmission electron microscopy and X ray diffractometer. It was found that the morphologies of alumina ge...The microstructures of nanosized alumina powders prepared by sol gel routine were systematically studied with transmission electron microscopy and X ray diffractometer. It was found that the morphologies of alumina gel powders change in the orders of caterpillar thorn granular dumbbell shaped structures during calcining at temperatures from 20?℃ to 800?℃, 1?200?℃ and 1?300?℃. The caterpillar shaped structure composed of strings with a diameter of 5?nm.展开更多
The influence of three different Al2O3 powder on self-flowing alumina castable was studied. Maximum compaction of sample was computed by Andresen Equation. The result showed that the Al2O3 powder, which has much small...The influence of three different Al2O3 powder on self-flowing alumina castable was studied. Maximum compaction of sample was computed by Andresen Equation. The result showed that the Al2O3 powder, which has much smaller particle size ,could improve the microstructure and the mechanical properties of castable under room temperature and high temperature. With the same powder size,the room temperature strength of the castable added with Al2O3 powder proPerties of which were altered by adding mineralizing agent, was higher than that of the castable added with common Al2O3 powder, but the flowability of these three different castable was almost the same.展开更多
The research gap on the feasibility of basalt rock powder(BRP)and superfine sand(SS)in preparation of cement mortar is significant.This study examines probable changes occurred in the modified cement mortar due to inc...The research gap on the feasibility of basalt rock powder(BRP)and superfine sand(SS)in preparation of cement mortar is significant.This study examines probable changes occurred in the modified cement mortar due to incorporation of certain quantity of basalt rock powder and superfine sand in mixture proportion.The cement mortar included Portland cement,artificial sand and water as principal mixture constituents.Then,basalt rock powder and superfine sand were added as partial replacement materials for Portland cement and artificial sand respectively.Therefore,replacement percentages were 10%,15%,20%,25%and 30%when the basalt rock powder replaced Portland cement and in case the artificial sand was replaced by superfine sand,10%,20%,30%,40%and 50%.Then,the strength indexes such as flexural strength,compressive strength,ultrasonic pulse velocity and dynamic elastic modulus were investigated.The results show that the presence of basalt rock powder in mixture proportion increased the flexural and compressive strengths of cement mortar however the cement mortar that contained superfine sand illustrated inadequate mechanical performance as flexural and compressive strengths decreased remarkably.Moreover,when basalt rock powder and superfine sand were included together in mixture proportion,the cement mortar’s mechanical performance declined compared to that of the reference cement mortar.Despite the fact that basalt rock powder and superfine sand weakened the cement mortar’s mechanical properties,it was found that they can be added into the cement mortar as partial replacement of Portland cement and artificial sand in the following ratios:from 10%to 25%when basalt rock powder replaces Portland cement and from 10%to 20%when artificial sand is replaced by superfine sand.展开更多
The approach that contributes to the development of eco-materials in construction is the use of mineral powders,which can improve mechanical properties and reduce cement consumption.This article aims to study th...The approach that contributes to the development of eco-materials in construction is the use of mineral powders,which can improve mechanical properties and reduce cement consumption.This article aims to study the effect of substitution by mass of cement with mineral powders on the physicomechanical properties and microstructure of sand concretes.The used mineral powders are A:the limestone,B:the natural pozzolan,C:the hydraulic lime,D:(1/3 limestone+1/3 natural pozzolan+1/3 hydraulic lime),and E:(1/2 natural pozzolan+1/2 hydraulic lime).The studied percentages are 5%,10%and 15%,in both separated and combined states.The studied properties are workability,compressive strength,the elasticity modulus in compression,shrinkage and microstructure analysis.The objective is to target the optimal percentage of the substitution of cement with mineral powders,which ensures the best compromise between the main properties of the studied sand concretes.The obtained results show that the optimal percentage is in favor of the substitution of cement by 10%D(1/3 limestone,1/3 natural pozzolan and 1/3 hydraulic lime).Even the 15%of mineral powder D,presented similar performances compared to the sand concrete(without mineral powders).Finally,in the context of the development of eco-materials,it should be noted that the 10%D and 15%D(1/3 limestone,1/3 natural pozzolan and 1/3 hydraulic lime)contribute to decrease the use of cement and consequently to reduce of CO2 emissions.展开更多
The key reason for SO_(2) formation during the production of a residue hydrogenation catalyst support was identified and subsequent emission reduction solutions were then investigated and verified systematically.The r...The key reason for SO_(2) formation during the production of a residue hydrogenation catalyst support was identified and subsequent emission reduction solutions were then investigated and verified systematically.The results demonstrated that carbon-containing organic materials,including sesbania powder and cellulose,did not completely decompose over the temperature range of 350−600℃during the heating stage of the calcination process,but rather underwent a condensation reaction within the same temperature range to form carbon-containing species with a lower ratio of hydrogen to carbon and a higher condensation degree,which promoted the decomposition of sulfate to form SO_(2).Systematic experimental work revealed that three different measures,i.e.,applying the staged calcination method,reducing the heating rate,and increasing the air flow rate,during the calcination process could all achieve the effect of reducing SO_(2) emissions.展开更多
文摘An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.
文摘There are many brands of activated alumina powders in the market and the products from different manufacturers exist subtle differences. In this work, four brands of activated alumina powder which are the mainstream products in China with the same marked particle size of 2-3 μm were added to corundum castables to investigate the effect of different activated alumina powder on properties of corundum castables. It is found that the multi-peak distribution, round-shape particle,low impurities content of alumina powder are of great benefit to the improvement of the overall performance of castables.Obvious CA6 frame structure formed in castables matrix is conductive to improving the thermal shock resistance and high temperature strength of castables. One kind of domestic alumina micropowder studied in this work has good application value and prospect in corundum castables because of the excellent comprehensive performance.
文摘To satisfy the requirements of alumina castables in specific environment and enhance their properties,alumina castables were prepared using tabular alumina,various alumina powders(07RAL,15RA,22RABL,40CA,99-20um,and 99-325mesh),and calcium aluminate cement as main raw materials,and heat treating at 110,1000,1600℃,respectively.Their flowability and physical properties were tested,and the morphology was researched.The results show that compared with calcined alumina and tabular alumina powders,reactive alumina has higher specific surface area and better filling performance leading to lower water demand and higher viscosity,and the castables prepared with reactive alumina have higher CCS and CMOR after heat treating at 110,1000 and 1600℃as well as lower PLC than those with calcined alumina and tabular alumina powders.
文摘To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al_(2)O_(3) micropowder),the fine powders with the median diameter of 50,30,10,and 5 pm,respectively,were obtained by grinding industrial alumina powder(the median diameter of 80 pm),and the active alumina micropowders were prepared by firing the industrial alumina powders before and after grinding at 1320℃ for 5 h.The effect of the particle size of the industrial alumina powder on the microstructure and properties of the active alumina micropowder was researched.The results indicate that the initial particle size of the industrial alumina powder has a great influence on the grain morphology of the active alumina micropowder;when the median diameter is larger than 30 pm,the α-Al_(2)O_(3) grains show wormlike aggregates state after calcination and when it is around or less than 10 pm,the α-Al_(2)O_(3) are round,spherical and well dispersed grains with the particle size of 0.3-1.0 pm.With the initial particle size of the industrial alumina powder decreasing,the α-Al_(2)O_(3) phase transition rate increases and the true density gradually increases;moreover,the α-Al_(2)O_(3) powder shows better dispersity and flowability.
文摘A zirconia alumina powder with a near spherical shape and an average size of 0.1～0.2 μm was prepared by co precipitation. XRD analysis shows that α Al 2O 3 phase may be directly transformed from amorphous in calcining the hydroxide composite. The ZrO 2 Al 2O 3 composite ceramics manufactured from this powder has the maximum fracture toughness of 9 MPa·m -1/2 at 15% ZrO 2 and 740 MPa fracture strength at 5% ZrO 2. Zirconia grains about 1 μm in diameter are dispersed uniformly in the alumina ceramic matrix.
文摘The microstructures of nanosized alumina powders prepared by sol gel routine were systematically studied with transmission electron microscopy and X ray diffractometer. It was found that the morphologies of alumina gel powders change in the orders of caterpillar thorn granular dumbbell shaped structures during calcining at temperatures from 20?℃ to 800?℃, 1?200?℃ and 1?300?℃. The caterpillar shaped structure composed of strings with a diameter of 5?nm.
文摘The influence of three different Al2O3 powder on self-flowing alumina castable was studied. Maximum compaction of sample was computed by Andresen Equation. The result showed that the Al2O3 powder, which has much smaller particle size ,could improve the microstructure and the mechanical properties of castable under room temperature and high temperature. With the same powder size,the room temperature strength of the castable added with Al2O3 powder proPerties of which were altered by adding mineralizing agent, was higher than that of the castable added with common Al2O3 powder, but the flowability of these three different castable was almost the same.
基金The authors would like to acknowledge the support of National Natural Science Foundation of China for providing research fund to conduct present study(No.51168031 and 51468039).
文摘The research gap on the feasibility of basalt rock powder(BRP)and superfine sand(SS)in preparation of cement mortar is significant.This study examines probable changes occurred in the modified cement mortar due to incorporation of certain quantity of basalt rock powder and superfine sand in mixture proportion.The cement mortar included Portland cement,artificial sand and water as principal mixture constituents.Then,basalt rock powder and superfine sand were added as partial replacement materials for Portland cement and artificial sand respectively.Therefore,replacement percentages were 10%,15%,20%,25%and 30%when the basalt rock powder replaced Portland cement and in case the artificial sand was replaced by superfine sand,10%,20%,30%,40%and 50%.Then,the strength indexes such as flexural strength,compressive strength,ultrasonic pulse velocity and dynamic elastic modulus were investigated.The results show that the presence of basalt rock powder in mixture proportion increased the flexural and compressive strengths of cement mortar however the cement mortar that contained superfine sand illustrated inadequate mechanical performance as flexural and compressive strengths decreased remarkably.Moreover,when basalt rock powder and superfine sand were included together in mixture proportion,the cement mortar’s mechanical performance declined compared to that of the reference cement mortar.Despite the fact that basalt rock powder and superfine sand weakened the cement mortar’s mechanical properties,it was found that they can be added into the cement mortar as partial replacement of Portland cement and artificial sand in the following ratios:from 10%to 25%when basalt rock powder replaces Portland cement and from 10%to 20%when artificial sand is replaced by superfine sand.
文摘The approach that contributes to the development of eco-materials in construction is the use of mineral powders,which can improve mechanical properties and reduce cement consumption.This article aims to study the effect of substitution by mass of cement with mineral powders on the physicomechanical properties and microstructure of sand concretes.The used mineral powders are A:the limestone,B:the natural pozzolan,C:the hydraulic lime,D:(1/3 limestone+1/3 natural pozzolan+1/3 hydraulic lime),and E:(1/2 natural pozzolan+1/2 hydraulic lime).The studied percentages are 5%,10%and 15%,in both separated and combined states.The studied properties are workability,compressive strength,the elasticity modulus in compression,shrinkage and microstructure analysis.The objective is to target the optimal percentage of the substitution of cement with mineral powders,which ensures the best compromise between the main properties of the studied sand concretes.The obtained results show that the optimal percentage is in favor of the substitution of cement by 10%D(1/3 limestone,1/3 natural pozzolan and 1/3 hydraulic lime).Even the 15%of mineral powder D,presented similar performances compared to the sand concrete(without mineral powders).Finally,in the context of the development of eco-materials,it should be noted that the 10%D and 15%D(1/3 limestone,1/3 natural pozzolan and 1/3 hydraulic lime)contribute to decrease the use of cement and consequently to reduce of CO2 emissions.
基金support from the China Petrochemical Corporation(Sinopec Group 121043-2).
文摘The key reason for SO_(2) formation during the production of a residue hydrogenation catalyst support was identified and subsequent emission reduction solutions were then investigated and verified systematically.The results demonstrated that carbon-containing organic materials,including sesbania powder and cellulose,did not completely decompose over the temperature range of 350−600℃during the heating stage of the calcination process,but rather underwent a condensation reaction within the same temperature range to form carbon-containing species with a lower ratio of hydrogen to carbon and a higher condensation degree,which promoted the decomposition of sulfate to form SO_(2).Systematic experimental work revealed that three different measures,i.e.,applying the staged calcination method,reducing the heating rate,and increasing the air flow rate,during the calcination process could all achieve the effect of reducing SO_(2) emissions.
