With time concrete / reinforced concrete has become the popular material for construction. Modern industry utilizes this material a lot and has produced various beautiful, eye catching and amazing structures. Due to m...With time concrete / reinforced concrete has become the popular material for construction. Modern industry utilizes this material a lot and has produced various beautiful, eye catching and amazing structures. Due to modern requirements for living and developed construction industries, the old buildings (usually constructed with brick masonry) are demolished and are replaced with new modern buildings. Demolition of buildings results in waste materials which can create waste related problems and environmental issues. By using recycled aggregates weight of concrete can also be reduced, which can also solve problems related to self-weight of concrete. In this paper attempt has been made to use local used bricks from vicinity of Nawabshah, Pakistan, as coarse aggregate. Concrete cubes made with local recycled bricks are cast and tested for overall weight of concrete, moisture content, dynamic modulus of elasticity and compressive strength (nondestructive and destructive methods). The results showed that concrete derived from recycled aggregates attained lower strength than regular concrete. More detailed elaborated work is recommended with different mix ratios and different proportions recycled aggregates for better conclusions.展开更多
The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that Fe...The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.展开更多
Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the ...Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the high-temperature mechanical property and thermal shock resistance of low-carbon MgO-C bricks,a novel route of introducing ZrSiO_(4) powder into low-carbon MgO-C bricks was reported in such refractories with 2 wt.% flaky graphite.The results indicate that the low-carbon MgO-C brick with 0.5 wt.%ZrSiO_(4) addition has the maximum hot modulus of rupture at 1400℃ and the corresponding specimen fired in the carbon embedded atmosphere has the maximum residual strength ratio(98.6%)after three thermal shock cycles.It is found that some needle-like AlON and plate-like Al_(2)O_(3)-ZrO_(2) composites were in situ formed in the matrices after the low-carbon MgO-C bricks were coked at 1400℃,which can enhance the high-temperature mechanical property and thermal shock resistance due to the effect of fiber toughening and particle toughening.Moreover,CO_(2) emission of the newly developed low-carbon MgO-C bricks is reduced by 58.3% per ton steel after using them as the working lining of a 90 t vacuum oxygen decarburization ladle.展开更多
Due to thermal stability and excellent resistance to slag erosion,the used refractories can be recycled as the main raw material for some refractories.In this article the latest developments about used refractories in...Due to thermal stability and excellent resistance to slag erosion,the used refractories can be recycled as the main raw material for some refractories.In this article the latest developments about used refractories in metallurgical industry has been reviewed,focusing on the results reported in the past decade.The research and reutilization methods of used refractories were discussed.For the research of used refractories,the results of two aspects,the performance and surface corrosion characteristics,are summarized.Then,the advances in research on recycling technology of several main kinds of used refractories,such as MgO-C,Al2O3-SiC-C,Al2O3-MgO-C,magnesium-chrome,and corundum-spinel refractories were summarized and discussed in detail.Some results of the author’s group were reported等线accompanied by these comments.The microstructure and chemical composition were studied by scanning electron microscopy and energy dispersion spectra,and the properties of the refractories were analyzed.Afterwards,the scope of application of materials was determined according to the classification and analysis of refractories.Finally,the large-scale application of used refractories and an outlook is given to future developments of the entire recycling industry.展开更多
The paper analyzed the recycle condition and developing trend of used refractories China and other countries, irwluding research achievements of recycles of used refractories such as MgO-C bricks, Al2O3-MgO-C brics, A...The paper analyzed the recycle condition and developing trend of used refractories China and other countries, irwluding research achievements of recycles of used refractories such as MgO-C bricks, Al2O3-MgO-C brics, Al2O3-SiC-C castable and MgO-Cr2O3 bricks. Recycled refractories exhibit the same or even better properties as compared with the original. In addition, prospects for recycle of used refractories are also discusseded.展开更多
In-situ magnesia-rich spinel fiber was formed resulting from the addition of ferrocene into MgO-C refractory matrixes. The formation of in-situ spinel fiber was detected to start at 1300 ℃. The amount, diameter and l...In-situ magnesia-rich spinel fiber was formed resulting from the addition of ferrocene into MgO-C refractory matrixes. The formation of in-situ spinel fiber was detected to start at 1300 ℃. The amount, diameter and length of the fibers increased with rising temperature. Ferrocene may have catalytic effects on the growth of the fibers in two aspects. First, the reaction between MgO and C and the decomposition of Al4C3 may be catalyzed at high temperature. Suitable concentration gaseous phase is then created for vapor-vapor reaction which could result in the in-situ formation of fibers. Second, Fe nanoparticle produced from ferrocene can act as catalytic droplets and catalyze the growth of the fibers. The fibers are formed via the vapor-liquid-solid and vapor-solid mechanisms. In terms of chemical thermodynamics, the partial pressure of CO and Mg（g） are found to play an important role in the in-situ fibers formation. Different concentration of vapors affects the size, amount and composition of the fibers at different temperatures. The mechanical properties of MgO-C brick was found to be improved by ferrocene addition.展开更多
Al_(4)SiC_(4)was prepared using Al powder,silicon carbide powder,and graphite as raw materials,and silicon as the additive by microwave sintering.Effects of silicon additions(0,5%,10%and 15%,by mass)on the phase compo...Al_(4)SiC_(4)was prepared using Al powder,silicon carbide powder,and graphite as raw materials,and silicon as the additive by microwave sintering.Effects of silicon additions(0,5%,10%and 15%,by mass)on the phase composition,microstructure,apparent porosity and bulk density of the Al_(4)SiC_(4)sample prepared with different aluminum additions(20%,25%,by mass)were researched.Then the developed Al_(4)SiC_(4)samples were applied to MgO-C bricks to investigate the effect on the oxidation resistance and mechanical properties of the MgO-C bricks.The results show that Al_(4)SiC_(4)can be synthesized at lower temperatures using the microwave sintering method.The sample with 20%aluminum addition has a lower Al_(4)SiC_(4)content than the one with 25%aluminum.When the silicon addition is 10%and the aluminum addition is 25%,the sample appears needlelike system,the porosity is only 28.69%,and the sample is dense.The developed Al_(4)SiC_(4)was added into MgO-C bricks as the antioxidant,which greatly increased the oxidation resistance and the mechanical properties of the MgO-C bricks.展开更多
文摘With time concrete / reinforced concrete has become the popular material for construction. Modern industry utilizes this material a lot and has produced various beautiful, eye catching and amazing structures. Due to modern requirements for living and developed construction industries, the old buildings (usually constructed with brick masonry) are demolished and are replaced with new modern buildings. Demolition of buildings results in waste materials which can create waste related problems and environmental issues. By using recycled aggregates weight of concrete can also be reduced, which can also solve problems related to self-weight of concrete. In this paper attempt has been made to use local used bricks from vicinity of Nawabshah, Pakistan, as coarse aggregate. Concrete cubes made with local recycled bricks are cast and tested for overall weight of concrete, moisture content, dynamic modulus of elasticity and compressive strength (nondestructive and destructive methods). The results showed that concrete derived from recycled aggregates attained lower strength than regular concrete. More detailed elaborated work is recommended with different mix ratios and different proportions recycled aggregates for better conclusions.
基金Item Sponsored by National Natural Science Foundation of China (51090382)
文摘The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.
基金Enterprise Research and Development Project of Beijing Lirr High-Temperature Materials Co.,Ltd.(2020-02)Key Scientific Research Project for Universities and Colleges in Henan Province(19A430028)+1 种基金the Excellent Youth Research Project of Anhui Province(2022AH030135)the PhD Research Funding of Suzhou University(2021BSK041).
文摘Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the high-temperature mechanical property and thermal shock resistance of low-carbon MgO-C bricks,a novel route of introducing ZrSiO_(4) powder into low-carbon MgO-C bricks was reported in such refractories with 2 wt.% flaky graphite.The results indicate that the low-carbon MgO-C brick with 0.5 wt.%ZrSiO_(4) addition has the maximum hot modulus of rupture at 1400℃ and the corresponding specimen fired in the carbon embedded atmosphere has the maximum residual strength ratio(98.6%)after three thermal shock cycles.It is found that some needle-like AlON and plate-like Al_(2)O_(3)-ZrO_(2) composites were in situ formed in the matrices after the low-carbon MgO-C bricks were coked at 1400℃,which can enhance the high-temperature mechanical property and thermal shock resistance due to the effect of fiber toughening and particle toughening.Moreover,CO_(2) emission of the newly developed low-carbon MgO-C bricks is reduced by 58.3% per ton steel after using them as the working lining of a 90 t vacuum oxygen decarburization ladle.
基金National Key R&D Program of China(Grant No.2018YFC1901504)National Natural Science Foundation of China(Grant No.51872268).
文摘Due to thermal stability and excellent resistance to slag erosion,the used refractories can be recycled as the main raw material for some refractories.In this article the latest developments about used refractories in metallurgical industry has been reviewed,focusing on the results reported in the past decade.The research and reutilization methods of used refractories were discussed.For the research of used refractories,the results of two aspects,the performance and surface corrosion characteristics,are summarized.Then,the advances in research on recycling technology of several main kinds of used refractories,such as MgO-C,Al2O3-SiC-C,Al2O3-MgO-C,magnesium-chrome,and corundum-spinel refractories were summarized and discussed in detail.Some results of the author’s group were reported等线accompanied by these comments.The microstructure and chemical composition were studied by scanning electron microscopy and energy dispersion spectra,and the properties of the refractories were analyzed.Afterwards,the scope of application of materials was determined according to the classification and analysis of refractories.Finally,the large-scale application of used refractories and an outlook is given to future developments of the entire recycling industry.
文摘The paper analyzed the recycle condition and developing trend of used refractories China and other countries, irwluding research achievements of recycles of used refractories such as MgO-C bricks, Al2O3-MgO-C brics, Al2O3-SiC-C castable and MgO-Cr2O3 bricks. Recycled refractories exhibit the same or even better properties as compared with the original. In addition, prospects for recycle of used refractories are also discusseded.
基金Funded by the National Natural Science Foundation of China (No.50872125)
文摘In-situ magnesia-rich spinel fiber was formed resulting from the addition of ferrocene into MgO-C refractory matrixes. The formation of in-situ spinel fiber was detected to start at 1300 ℃. The amount, diameter and length of the fibers increased with rising temperature. Ferrocene may have catalytic effects on the growth of the fibers in two aspects. First, the reaction between MgO and C and the decomposition of Al4C3 may be catalyzed at high temperature. Suitable concentration gaseous phase is then created for vapor-vapor reaction which could result in the in-situ formation of fibers. Second, Fe nanoparticle produced from ferrocene can act as catalytic droplets and catalyze the growth of the fibers. The fibers are formed via the vapor-liquid-solid and vapor-solid mechanisms. In terms of chemical thermodynamics, the partial pressure of CO and Mg（g） are found to play an important role in the in-situ fibers formation. Different concentration of vapors affects the size, amount and composition of the fibers at different temperatures. The mechanical properties of MgO-C brick was found to be improved by ferrocene addition.
文摘Al_(4)SiC_(4)was prepared using Al powder,silicon carbide powder,and graphite as raw materials,and silicon as the additive by microwave sintering.Effects of silicon additions(0,5%,10%and 15%,by mass)on the phase composition,microstructure,apparent porosity and bulk density of the Al_(4)SiC_(4)sample prepared with different aluminum additions(20%,25%,by mass)were researched.Then the developed Al_(4)SiC_(4)samples were applied to MgO-C bricks to investigate the effect on the oxidation resistance and mechanical properties of the MgO-C bricks.The results show that Al_(4)SiC_(4)can be synthesized at lower temperatures using the microwave sintering method.The sample with 20%aluminum addition has a lower Al_(4)SiC_(4)content than the one with 25%aluminum.When the silicon addition is 10%and the aluminum addition is 25%,the sample appears needlelike system,the porosity is only 28.69%,and the sample is dense.The developed Al_(4)SiC_(4)was added into MgO-C bricks as the antioxidant,which greatly increased the oxidation resistance and the mechanical properties of the MgO-C bricks.
