The microstructure and its effects on the high temperature mechanical behavior of Cu-2.7%Al_2O_3 （volume fraction） dispersion strengthened copper （ADSC） alloy were investigated. The results indicate that fine alum...The microstructure and its effects on the high temperature mechanical behavior of Cu-2.7%Al_2O_3 （volume fraction） dispersion strengthened copper （ADSC） alloy were investigated. The results indicate that fine alumina particles are uniformly distributed in the copper matrix, while a few coarse ones are distributed on the grain boundaries. Tensile tests results show that Hall-Petch mechanism is the main contribution to the yield strength of ADSC alloy at room temperature. Its high temperature strength is attributed to the strong pinning effects of alumina particles on the grain and sub-grain boundaries with dislocations. The ultimate tensile strength can reach 237 MPa and the corresponding yield strength reaches 226 MPa at 700℃. Tensile fracture morphology indicates that the ADSC alloy shows brittleness at elevated temperatures. Creep tests results demonstrate that the steady state creep rates at 400 ℃ are lower than those at 700 ℃. The stress exponents at 400 ℃ and 700℃ are 7 and 5, respectively, and the creep strain rates of the ADSC alloy are controlled by dislocation core diffusion and lattice diffusion.展开更多
To prevent radioactive iodides from releasing into the environment in an accident of a nuclear power plant,silver-impregnated alumina(Ag/Al2O3)was fabricated,and its performance of radioactive iodine adsorption from h...To prevent radioactive iodides from releasing into the environment in an accident of a nuclear power plant,silver-impregnated alumina(Ag/Al2O3)was fabricated,and its performance of radioactive iodine adsorption from high-temperature gas was tested.The silver loadings on alumina were obtained by ICP-OES and the texture properties of Ag/Al2O3were characterized by N2adsorption-desorption.The Ag/Al2O3was of reduced specific surface(107.2 m2/g at 650?C).Crystalline phases of Ag/Al2O3were confirmed through XRD characterization.After calcination at 650?C for 2 h,the crystalline phase of Ag/Al2O3changed.The131I-removal efficiency of Ag/Al2O3was tested at 100,250,350,450 and 650?C,with good decontamination factor values for the radioactive iodine.Silver-impregnated alumina can be applied as adsorbents to remove radioactive iodine at high temperatures in nuclear accident.展开更多
To reduce production costs and make full and reasonable use of raw materials,high alumina bricks were prepared using tabular corundum and mullite as aggregates,sillimanite as intermediate particles,and white fused cor...To reduce production costs and make full and reasonable use of raw materials,high alumina bricks were prepared using tabular corundum and mullite as aggregates,sillimanite as intermediate particles,and white fused corundum powder,α-alumina micropowder,and Suzhou soil as the matrix,firing at different temperatures(1420,1440,1460,1480,1500 and 1520℃)for 4 h.The apparent porosity(AP),the bulk density(BD),the cold crushing strength(CCS),the thermal shock resistance(TSR),the refractoriness under load(RUL)and the creep rate of the samples were tested.The effects of the firing temperature on the creep rate(1450℃×50 h,under a load of 0.2 MPa)of the samples were studied.The results show that with the sillimanite addition of 22.5 mass%,the sample fired at 1460℃for 4 h performs the best comprehensive properties:the AP of 17.5%,the BD of 2.75 g·cm^(-3),the CCS of 100.5 MPa,the TSR number of 35 cycles,the RUL of 1682℃,and the creep rate of-0.428%,which can prolong the service life of furnaces.展开更多
This work studied the effects of firing temperatures on the refractory properties of insulating firebricks produced from a blend of hydrometallurgically purified clay, high alumina cement and sawdust. Twenty grams out...This work studied the effects of firing temperatures on the refractory properties of insulating firebricks produced from a blend of hydrometallurgically purified clay, high alumina cement and sawdust. Twenty grams out of a bulk (1000 Kg) of clay obtained from Ipetumodu in Nigeria was analyzed for size range, consequent upon which the remaining bulk was sieved to 100 μm, being the average size. The bulk was there after leached under a predetermined condition (1.6 mol/dm3 of oxalic acid at 70oC for 150 min and 200 rev/min agitation speed) and cylindrical samples (5 cm diameter by 5 cm high) containing different quantities of high alumina cement (5% - 20%) and sawdust (1% - 5%) were prepared, dried at 110oC and subsequently fired at 900oC, 1100oC, 1300oC and 1500oC, at the rate of 4oC/min and soaked for 2 hrs. These samples were subjected to different refractory tests (permanent linear change, modulus of rupture, bulk density, cold crushing strength and apparent porosity). Even though samples containing more than 20% alumina crumbled at elevated temperatures, it was still observed that the bricks performed to expectations at lower alumina contents, even at 1500oC. The sample containing 3% sawdust and 10% alumina cement however, gave the desired requirement for preparing good insulating firebricks with reliable phase integrity, as revealed by scanning electron microscopy (SEM).展开更多
In this paper, an experimental study was conducted in order to test the feasibility of sintering mullite directly from the high-alumina fly ash, without adding any extra material. The results show that the mullite con...In this paper, an experimental study was conducted in order to test the feasibility of sintering mullite directly from the high-alumina fly ash, without adding any extra material. The results show that the mullite contents in most sintered samples are over 70%. The samples sintered from the beneficiated fly ash have a higher content of mullite than those from the as-received fly ash under the same synthetic conditions. To obtain an equal amount of mullite, a higher sintering temperature is needed for the beneficiated fly ash than for the as-received fly ash. Considering the physical properties of sintered mullite, the favorable sintering temperature is 1400℃ for the as-received fly ash and 1500℃ for the beneficiated fly ash. A higher sintering temperature and a shorter holding time are profitable to sintering mullite. The orthogonal test confirmed that the dominant factor affecting mullite synthesis is sintering temperature, and that the most profitable matching conditions are 200 MPa-1500℃-3 h for the as-received fly ash and 200 MPa-1500 ℃-4 h for the beneficiated fly ash.展开更多
Self-propagating high-temperature synthesis (SHS) with reduction process was used to fabricate TiB2 powder from TiO2-B2O3-Mg system. The colloidal alumina-bonded TiB2 paste was prepared and coated on the cathode carbo...Self-propagating high-temperature synthesis (SHS) with reduction process was used to fabricate TiB2 powder from TiO2-B2O3-Mg system. The colloidal alumina-bonded TiB2 paste was prepared and coated on the cathode carbon blocks. Various properties of the baked paste such as the corrosive resistance, thermal expansion and wettability were tested. Experimental results showed that the colloidal alumina-bonded TiB2 coating could be well wetted by liquid aluminum; and the thermal expansion coefficient of the coated material was 5.8x10(-6) degreesC(-1) at 20-1000 degreesC, which was close to that of the traditional anthracite block cathode (4x10(-6) degreesC(-1)); the electrical resistivity was 8 mu Omega (.)m at 900 degreesC when the content of alumina in the coated material was about 9% in mass fraction. In addition, some other good results such as sodium resistance were also reported.展开更多
The traditional alumina-silicate raw materials, for example, clays, in the precalcining technique of cement production, have been replaced by low grade and high silica content sandstones, shales, and industrial waste ...The traditional alumina-silicate raw materials, for example, clays, in the precalcining technique of cement production, have been replaced by low grade and high silica content sandstones, shales, and industrial waste residues, including fly ashes, slag, and others. The results are the change of compositions and characteristics of raw materials applied and a great effect on cement calcination process and clinker formation. In this work, the cement clinker formation process of different alumina-silicate raw materials to replace clay raw material was studied by chemical analysis, X-ray diffraction, differential thermal analysis, and high temperature microscope based on the characteristics of the alumina-silicate raw materials. The formation heat of the clinker was determined by the acid dissolution method. Influence of different alumina-silicate raw materials on the clinker burnability and formation process was studied. The results show that the changing of alumina- silicate raw materials, especially using industrial waste residues, can reduce the formation temperature of high temperature liquid phases, improve the burnability of raw materials, reduce the formation temperature and formation heat of clinker. And this study also observed the formation temperature and transformation of high temperature liquid phases in the heating process of raw materials by high temperature microscope.展开更多
基金Project(51271203)supported by the National Natural Science Foundation of Chinathe PPP project between the CSC(China Scholarship Council)and the DAAD(German Academic Exchange Service)+2 种基金Project(11JJ2025)supported by Hunan Provincial Natural Science Foundation of ChinaProject(YSZN2013CL06)supported by the Nonferrous Metals Science Foundation of HNG-CSUProject supported by the Aid program for Science Technology Innovative Research Team in Higher Educational Institutions of Hunan Province,China
文摘The microstructure and its effects on the high temperature mechanical behavior of Cu-2.7%Al_2O_3 （volume fraction） dispersion strengthened copper （ADSC） alloy were investigated. The results indicate that fine alumina particles are uniformly distributed in the copper matrix, while a few coarse ones are distributed on the grain boundaries. Tensile tests results show that Hall-Petch mechanism is the main contribution to the yield strength of ADSC alloy at room temperature. Its high temperature strength is attributed to the strong pinning effects of alumina particles on the grain and sub-grain boundaries with dislocations. The ultimate tensile strength can reach 237 MPa and the corresponding yield strength reaches 226 MPa at 700℃. Tensile fracture morphology indicates that the ADSC alloy shows brittleness at elevated temperatures. Creep tests results demonstrate that the steady state creep rates at 400 ℃ are lower than those at 700 ℃. The stress exponents at 400 ℃ and 700℃ are 7 and 5, respectively, and the creep strain rates of the ADSC alloy are controlled by dislocation core diffusion and lattice diffusion.
基金Supported by National Natural Science Foundation of China(No.21201013)
文摘To prevent radioactive iodides from releasing into the environment in an accident of a nuclear power plant,silver-impregnated alumina(Ag/Al2O3)was fabricated,and its performance of radioactive iodine adsorption from high-temperature gas was tested.The silver loadings on alumina were obtained by ICP-OES and the texture properties of Ag/Al2O3were characterized by N2adsorption-desorption.The Ag/Al2O3was of reduced specific surface(107.2 m2/g at 650?C).Crystalline phases of Ag/Al2O3were confirmed through XRD characterization.After calcination at 650?C for 2 h,the crystalline phase of Ag/Al2O3changed.The131I-removal efficiency of Ag/Al2O3was tested at 100,250,350,450 and 650?C,with good decontamination factor values for the radioactive iodine.Silver-impregnated alumina can be applied as adsorbents to remove radioactive iodine at high temperatures in nuclear accident.
文摘To reduce production costs and make full and reasonable use of raw materials,high alumina bricks were prepared using tabular corundum and mullite as aggregates,sillimanite as intermediate particles,and white fused corundum powder,α-alumina micropowder,and Suzhou soil as the matrix,firing at different temperatures(1420,1440,1460,1480,1500 and 1520℃)for 4 h.The apparent porosity(AP),the bulk density(BD),the cold crushing strength(CCS),the thermal shock resistance(TSR),the refractoriness under load(RUL)and the creep rate of the samples were tested.The effects of the firing temperature on the creep rate(1450℃×50 h,under a load of 0.2 MPa)of the samples were studied.The results show that with the sillimanite addition of 22.5 mass%,the sample fired at 1460℃for 4 h performs the best comprehensive properties:the AP of 17.5%,the BD of 2.75 g·cm^(-3),the CCS of 100.5 MPa,the TSR number of 35 cycles,the RUL of 1682℃,and the creep rate of-0.428%,which can prolong the service life of furnaces.
文摘This work studied the effects of firing temperatures on the refractory properties of insulating firebricks produced from a blend of hydrometallurgically purified clay, high alumina cement and sawdust. Twenty grams out of a bulk (1000 Kg) of clay obtained from Ipetumodu in Nigeria was analyzed for size range, consequent upon which the remaining bulk was sieved to 100 μm, being the average size. The bulk was there after leached under a predetermined condition (1.6 mol/dm3 of oxalic acid at 70oC for 150 min and 200 rev/min agitation speed) and cylindrical samples (5 cm diameter by 5 cm high) containing different quantities of high alumina cement (5% - 20%) and sawdust (1% - 5%) were prepared, dried at 110oC and subsequently fired at 900oC, 1100oC, 1300oC and 1500oC, at the rate of 4oC/min and soaked for 2 hrs. These samples were subjected to different refractory tests (permanent linear change, modulus of rupture, bulk density, cold crushing strength and apparent porosity). Even though samples containing more than 20% alumina crumbled at elevated temperatures, it was still observed that the bricks performed to expectations at lower alumina contents, even at 1500oC. The sample containing 3% sawdust and 10% alumina cement however, gave the desired requirement for preparing good insulating firebricks with reliable phase integrity, as revealed by scanning electron microscopy (SEM).
基金This work was financed by the National Natural Science Foundation of China （Grant No. 40672103 , 40575065） the Program for New Century Excellent Talents in University of the Chinese Ministry of Education. The authors sincerely thank Professor Li Kaiqi for his constructive suggestions and useful discussions.
文摘In this paper, an experimental study was conducted in order to test the feasibility of sintering mullite directly from the high-alumina fly ash, without adding any extra material. The results show that the mullite contents in most sintered samples are over 70%. The samples sintered from the beneficiated fly ash have a higher content of mullite than those from the as-received fly ash under the same synthetic conditions. To obtain an equal amount of mullite, a higher sintering temperature is needed for the beneficiated fly ash than for the as-received fly ash. Considering the physical properties of sintered mullite, the favorable sintering temperature is 1400℃ for the as-received fly ash and 1500℃ for the beneficiated fly ash. A higher sintering temperature and a shorter holding time are profitable to sintering mullite. The orthogonal test confirmed that the dominant factor affecting mullite synthesis is sintering temperature, and that the most profitable matching conditions are 200 MPa-1500℃-3 h for the as-received fly ash and 200 MPa-1500 ℃-4 h for the beneficiated fly ash.
文摘Self-propagating high-temperature synthesis (SHS) with reduction process was used to fabricate TiB2 powder from TiO2-B2O3-Mg system. The colloidal alumina-bonded TiB2 paste was prepared and coated on the cathode carbon blocks. Various properties of the baked paste such as the corrosive resistance, thermal expansion and wettability were tested. Experimental results showed that the colloidal alumina-bonded TiB2 coating could be well wetted by liquid aluminum; and the thermal expansion coefficient of the coated material was 5.8x10(-6) degreesC(-1) at 20-1000 degreesC, which was close to that of the traditional anthracite block cathode (4x10(-6) degreesC(-1)); the electrical resistivity was 8 mu Omega (.)m at 900 degreesC when the content of alumina in the coated material was about 9% in mass fraction. In addition, some other good results such as sodium resistance were also reported.
基金Funded by the National Basic Research Program of China("973"Program)(No.2009CB623102)the National High Technology Research and Development Program of China("863"Program)(No.2013AA031602)
文摘The traditional alumina-silicate raw materials, for example, clays, in the precalcining technique of cement production, have been replaced by low grade and high silica content sandstones, shales, and industrial waste residues, including fly ashes, slag, and others. The results are the change of compositions and characteristics of raw materials applied and a great effect on cement calcination process and clinker formation. In this work, the cement clinker formation process of different alumina-silicate raw materials to replace clay raw material was studied by chemical analysis, X-ray diffraction, differential thermal analysis, and high temperature microscope based on the characteristics of the alumina-silicate raw materials. The formation heat of the clinker was determined by the acid dissolution method. Influence of different alumina-silicate raw materials on the clinker burnability and formation process was studied. The results show that the changing of alumina- silicate raw materials, especially using industrial waste residues, can reduce the formation temperature of high temperature liquid phases, improve the burnability of raw materials, reduce the formation temperature and formation heat of clinker. And this study also observed the formation temperature and transformation of high temperature liquid phases in the heating process of raw materials by high temperature microscope.
