Aluminum based metal matrix composites were fabricated using stir casting where silicon carbide and alumina were the reinforcements. Different types of properties (physical-density, mechanical-tensile, hardness, chemi...Aluminum based metal matrix composites were fabricated using stir casting where silicon carbide and alumina were the reinforcements. Different types of properties (physical-density, mechanical-tensile, hardness, chemical-corrosion etc.) were measured and compared with base metals/alloys. The properties were significantly varied. The highest density was obtained for pure aluminium with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-4032 alloy. The highest hardness was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for pure Al with 5% Al<sub>2</sub>O<sub>3</sub>. The highest strength was obtained for AA-6061 with 5% coarse SiC whereas the lowest was obtained for pure Al. The highest impact strength was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-6061. The corrosion resistance of all composites was lower than that of the base materials.展开更多
Al2O3-13%TiO2 (mass fraction) coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and cer...Al2O3-13%TiO2 (mass fraction) coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating: one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.展开更多
NF3 decomposition in the absence of water over Al2O3, Fe2O3, Co3O4 and NiO, and transition metal oxides (Fe203, CO3O4 and NiO) coated Al2O3 reagents was investigated. The results show that Al2O3 is an active reagent...NF3 decomposition in the absence of water over Al2O3, Fe2O3, Co3O4 and NiO, and transition metal oxides (Fe203, CO3O4 and NiO) coated Al2O3 reagents was investigated. The results show that Al2O3 is an active reagent for NF3 decomposition with 100% conversion lasting for 8.5 h at 400 ℃. Fe203, Co3O4 and NiO coated Al2O3 reagents are superior to bare Al2O3, and 5%Co3O4/Al2O3 has a high reactivity with NF3 full conversion maintaining for 10.5 h. It is suggested that the presence of transition metal oxide is beneficial to the reactivity of Al2O3, and results in a significant enhancement in the fluorination of Al2O3.展开更多
This paper presents the results of the comparative study of as cast microstructures and mechanical properties viz yield strength, ultimate tensile strength, elastic modulus, percentage elongation, hardness, percentage...This paper presents the results of the comparative study of as cast microstructures and mechanical properties viz yield strength, ultimate tensile strength, elastic modulus, percentage elongation, hardness, percentage porosity and fracture characteristic of 5 wt% SiC and Al2O3 particulate reinforced Al-4% Cu-2.5% Mg matrix composites. These composite materials were prepared through stir casting process. Quantitative metallographic techniques were utilized to determine the average grain size of particles. The microstructures and tensile fracture characteristic of the representative samples of the composites were examined using optical microscope (OM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) techniques. The experimental results demonstrate a fairly uniform distribution of 50.8 μm Al2O3 and 49.2 μm SiC spherical particles with some clustering in few areas. At the interfaces of Al2O3 and the matrix, MgO and MgAl2O4 were observed. Similarly, Al4C3 was formed at the interfaces between SiC and the matrix. The mechanical property test results revealed that, for the same weight percentage of reinforcement, Al-4% Cu-2.5% Mg/5 wt% SiC composite exhibit a 15.8%, 16.4%, 4.97% and 10.8% higher yield strength, ultimate tensile strength, elastic modulus, and hardness, respectively. On the other hand, even if some porosity was observed in the Al2O3 reinforced composite, the percentage elongation (ductility) was 31% higher than that of SiC rein-forced composite. The tensile specimen of SiC reinforced composite failed in a brittle fashion without neck formation, whereas the Al2O3 reinforced composite failed in a ductile fashion with noticeable neck formation.展开更多
This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,th...This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,the evolution of alumina fiber during the processing and the characteristics of the resultant PEO coating were investigated.The voltage response as a function of processing time was changed.Lower voltage in the presence of alumina fiber is responsible for the lower coating thickness.The morphology and phase composition of the coatings are also influenced by the incorporation of the fiber.Firstly,the fiber is embedded in the coating and interrupts the continuity of the coating.With increasing processing time,the fiber is found to be reactively incorporated in the coating.The intention to produce a MgAl_(2)O_(4)containing coating is achieved and it is mainly accumulated near the coating surface.However,due to the low number of fibers,the Al content is overall still low and only near to the fibers the MgAl_(2)O_(4)spinel phase can form.展开更多
Taguchi technique was used to predict the influence of processing parameters on the erosive wear behavior Al7034-T6composite reinforced with SiC and Al2O3particles in different mass fractions.These hybrid metal matrix...Taguchi technique was used to predict the influence of processing parameters on the erosive wear behavior Al7034-T6composite reinforced with SiC and Al2O3particles in different mass fractions.These hybrid metal matrix composites(HMMCs)werefabricated by using a simple technique called stir casting technique.Scanning electron microscope(SEM)was used to study thesurface morphology of the composite and its evolution according to processing time.The design of experiment(DOE)based onTaguchi’s L16orthogonal array was used to identify various erosion trials.The most influencing parameter affecting the wear rate wasidentified.The results indicate that erosion wear rate of this hybrid composite is greatly influenced more by filler content and impactvelocity respectively compared to other factors.This also shows the significant wear resistance with the increase in the filler contentsof SiC and Al2O3particles,respectively.展开更多
In0.4Ga0.6As channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with and without an Si-doped In0.49Ga0.51P barrier layer grown on semi-insulating GaAs substrates have been investigated for the firs...In0.4Ga0.6As channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with and without an Si-doped In0.49Ga0.51P barrier layer grown on semi-insulating GaAs substrates have been investigated for the first time. Compared with the In0.4Ga0.6As MOSFETs without an In0.49Ga0.51P barrier layer, In0.4Ga0.6As MOSFETs with an In0.49Ga0.51P barrier layer show higher drive current, higher transconductance, lower gate leakage current, lower subthreshold swing, and higher effective channel mobility. These In0.4Ga0.6As MOSFETs (gate length 2 μm) with an In0.49Ga0.51P barrier layer exhibit a high drive current of 117 mA/mm, a high transconductance of 71.9 mS/mm, and a maximum effective channel mobility of 1266 cm2/(V·s).展开更多
The tensile strength of squeeze casting ZA22/Al 2O 3 short fiber composite was measured with autograph AG 10TA universal testing machines made in Japan. The experimental results were analysed with the rule of mixtu...The tensile strength of squeeze casting ZA22/Al 2O 3 short fiber composite was measured with autograph AG 10TA universal testing machines made in Japan. The experimental results were analysed with the rule of mixture(ROM) model modified by Friend. The theoretical analysis agree well with the experimental results. Under the test condition of this study, the strengthening critical fiber volume fraction predicted is 34 5%. Because fiber volume fraction in the composite is under this value, the tensile strength of the composite is lower than that of ZA22 alloy matrix.展开更多
Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two k...Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two kinetic models have been published [2-5]. In order to distinguish a kinetics model based on the ad- sorption capacity of a solid from the one based on the concentration of a solution, Lagergren's first-order rate equation has been called pseudo-first-order [6-7]. The Lagergren's equation has been widely cited, but there are far more mistakes made in the quotation and in the reference section of papers, including the title, the author's name, journal title, year of publishing, volume, and page number [3]. In addition, the second order kinetic expression for the adsorption systems of divalent metal ions using sphagnum moss peat has been reported by Ho [8].展开更多
SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction (XRD), scanning electron microsco...SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and metallurgical microscope. The effects of technical parameters on the properties of the product were analyzed. The results indicate that the composite possesses a dense microstructure, composed of three interpenetrated phases. Of them, SiO2 layer prohibits the powdering of the composites; Mg promotes the wetting and infiltration of the system and Si restricts the interfacial reaction while improving the wetting ability between reinforcement and matrix.展开更多
SiC particulates reinforced alumina matrix composites were fabricated using Directed Metal Oxidation (DIMOX) process. Continuous oxidation of an Al-Si-Mg-Zn alloy with different interlayers (dopents) as growth promote...SiC particulates reinforced alumina matrix composites were fabricated using Directed Metal Oxidation (DIMOX) process. Continuous oxidation of an Al-Si-Mg-Zn alloy with different interlayers (dopents) as growth promoters, will encompasses the early heating of the alloy ingot, melting and continued heating to temperature in the narrow range of 950°C to 980°C in an atmosphere of oxygen. Varying interlayers (dopents) are incorporated to examine the growth conditions of the composite materials and to identification of suitable growth promoter. The process is extremely difficult because molten aluminum does not oxidize after prolonged duration at high temperatures due to the formation of a passivating oxide layer. It is known that the Lanxide Corporation had used a combination of dopents to cause the growth of alumina from molten metal. This growth was directed, i.e. the growth is allowed only in the required direction and restricted in the other directions. The react nature of the dopants was a trade secret. Though it is roughly known that Mg and Si in the Al melt can aid growth, additional dopents used, the temperatures at which the process was carried out, the experimental configurations that aided directed growth were not precisely known. In this paper we have evaluated the conditions in which composites can be grown in large enough sizes for evaluation application and have arrived at a procedure that enables the fabrication of large composite samples by determining the suitable growth promoter (dopant). Scanning electron microscopic, EDS analysis of the composite was found to contain a continuous network of Al2O3, which was predominantly free of grain-boundary phases, a continuous network of Al alloy. Fabrication of large enough samples was done only by the inventor company and the property measurements by the company were confirmed to those needed to enable immediate applications. Since there are a large number of variable affecting robust growth of the composite, fabrication large sized samples for measurements is a difficult task. In the present work, to identify a suitable window of parameters that enables robust growth of the composite has been attempted.展开更多
1 Scope This standard specifies the classification, shape and dimensions, technical requirements, test methods, quality appraisal procedures, packing, marking, transportation, storage, and quality certificate of Al2O...1 Scope This standard specifies the classification, shape and dimensions, technical requirements, test methods, quality appraisal procedures, packing, marking, transportation, storage, and quality certificate of Al2O3- SiC - C bricks for hot metal pretreatment.展开更多
1 Scope This standard specifies the classification, techni- cal requirements, test methods, inspection rules, packing, marking, transportation, storage and quality certificate of Al2O3- SiC - C bricks for hot metal p...1 Scope This standard specifies the classification, techni- cal requirements, test methods, inspection rules, packing, marking, transportation, storage and quality certificate of Al2O3- SiC - C bricks for hot metal pretreatment.展开更多
This article shows main principles and presents ideas described in the scientific and technical literature, on the mechanism of interaction of microwave radiation with a solid phase materials, which were used as a bas...This article shows main principles and presents ideas described in the scientific and technical literature, on the mechanism of interaction of microwave radiation with a solid phase materials, which were used as a basis of creation of new perspective, energy efficient and environmentally safe technologies of preparation of heterogeneous catalysts for the reactions which were carried out under the influence of electro-magnetic radiation of microwave radiation. Author’s research results confirm possibilities of practical use of proposed method of hydrothermal oxidation of industrial low-dispersing of aluminum powders with presence of bulk phase of Al(ОН)<sub>3</sub>·nH<sub>2</sub>O, with further thermal treatment in microwave field for acquisition of armored А1/А1<sub>2</sub>О3<sub>3</sub> compositions, which effectively consume energy of microwave radiation. Due to the textured characteristics and thermo-transforming ability, synthesized components can be used as potential universal bearings of catalysts for reactions stimulated by electromagnetic radiation of (2.45 GHz) microwave frequency.展开更多
Owing to adjustable thermal expansion performance, BaO–CaO–Al_2O_3–B_2O_3–SiO_2(BCABS) glass has a promising commercialization prospect for intermediate temperature-solid oxide fuel cells(IT-SOFCs) sealing. Herein...Owing to adjustable thermal expansion performance, BaO–CaO–Al_2O_3–B_2O_3–SiO_2(BCABS) glass has a promising commercialization prospect for intermediate temperature-solid oxide fuel cells(IT-SOFCs) sealing. Herein, Al_2O_3 with two different contents was added into the same glass formulation, referred to as A and B glass, respectively. In terms of the non-isothermal crystallization kinetic behavior, the effect of Al_2O_3 as the unique intermediate was innovatively studied on the long-term performance of BCABS sealing glass. After the heat treatment at 1023 K for 100 h, the change of the network structure and the expansion coefficient of the glass were characterized. The results showed that the addition of Al_2O_3 as a network forming body could enhance the structure of glass, and increase the activation energy for glass transition, which could effectively inhibit the crystallization ability of sealing glass. Therefore, the B glass with the higher Al_2O_3 content showed the better long-term sealing ability, which was greatly beneficial for IT-SOFCs sealing.展开更多
The effect of pretreatment on Pd/Al2O3 catalysts for the catalytic oxidation of o-xylene at low temperature was studied by changing the pretreatment and testing conditions. The fresh and pretreated Pd/Al2O3 catalysts ...The effect of pretreatment on Pd/Al2O3 catalysts for the catalytic oxidation of o-xylene at low temperature was studied by changing the pretreatment and testing conditions. The fresh and pretreated Pd/Al2O3 catalysts were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results showed that the pretreatment dramatically changed the Pd/PdO ratio and then significantly affected the Pd/Al2O3 activity; while the pretreatment had not much influence on Pd particle size. The Pd/Al2O3 pre-reduced at 300~C/400~C, which has fully reduced Pd species, showed the highest activity; while the fresh Pd/Al2O3, which has fully oxidized Pd species, presented the worst performance, indicating the Pd chemical state plays an important role in the catalytic activity for the o-xylene oxidation. It is concluded that metallic Pd is the active species on the Pd/Al2O3 catalyst for the catalytic oxidation of o-xylene at low temperature.展开更多
文摘Aluminum based metal matrix composites were fabricated using stir casting where silicon carbide and alumina were the reinforcements. Different types of properties (physical-density, mechanical-tensile, hardness, chemical-corrosion etc.) were measured and compared with base metals/alloys. The properties were significantly varied. The highest density was obtained for pure aluminium with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-4032 alloy. The highest hardness was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for pure Al with 5% Al<sub>2</sub>O<sub>3</sub>. The highest strength was obtained for AA-6061 with 5% coarse SiC whereas the lowest was obtained for pure Al. The highest impact strength was obtained for AA-4032 with 5% Al<sub>2</sub>O<sub>3</sub> whereas the lowest was obtained for AA-6061. The corrosion resistance of all composites was lower than that of the base materials.
基金Project (59975046) supported by the National Natural Science Foundation of China
文摘Al2O3-13%TiO2 (mass fraction) coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating: one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.
基金supported by the National Natural Science Foundation of China (No. 20573089, 20976149)
文摘NF3 decomposition in the absence of water over Al2O3, Fe2O3, Co3O4 and NiO, and transition metal oxides (Fe203, CO3O4 and NiO) coated Al2O3 reagents was investigated. The results show that Al2O3 is an active reagent for NF3 decomposition with 100% conversion lasting for 8.5 h at 400 ℃. Fe203, Co3O4 and NiO coated Al2O3 reagents are superior to bare Al2O3, and 5%Co3O4/Al2O3 has a high reactivity with NF3 full conversion maintaining for 10.5 h. It is suggested that the presence of transition metal oxide is beneficial to the reactivity of Al2O3, and results in a significant enhancement in the fluorination of Al2O3.
文摘This paper presents the results of the comparative study of as cast microstructures and mechanical properties viz yield strength, ultimate tensile strength, elastic modulus, percentage elongation, hardness, percentage porosity and fracture characteristic of 5 wt% SiC and Al2O3 particulate reinforced Al-4% Cu-2.5% Mg matrix composites. These composite materials were prepared through stir casting process. Quantitative metallographic techniques were utilized to determine the average grain size of particles. The microstructures and tensile fracture characteristic of the representative samples of the composites were examined using optical microscope (OM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) techniques. The experimental results demonstrate a fairly uniform distribution of 50.8 μm Al2O3 and 49.2 μm SiC spherical particles with some clustering in few areas. At the interfaces of Al2O3 and the matrix, MgO and MgAl2O4 were observed. Similarly, Al4C3 was formed at the interfaces between SiC and the matrix. The mechanical property test results revealed that, for the same weight percentage of reinforcement, Al-4% Cu-2.5% Mg/5 wt% SiC composite exhibit a 15.8%, 16.4%, 4.97% and 10.8% higher yield strength, ultimate tensile strength, elastic modulus, and hardness, respectively. On the other hand, even if some porosity was observed in the Al2O3 reinforced composite, the percentage elongation (ductility) was 31% higher than that of SiC rein-forced composite. The tensile specimen of SiC reinforced composite failed in a brittle fashion without neck formation, whereas the Al2O3 reinforced composite failed in a ductile fashion with noticeable neck formation.
基金China Scholarship Council for the award of fellowship and funding (No. 201708510113)。
文摘This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,the evolution of alumina fiber during the processing and the characteristics of the resultant PEO coating were investigated.The voltage response as a function of processing time was changed.Lower voltage in the presence of alumina fiber is responsible for the lower coating thickness.The morphology and phase composition of the coatings are also influenced by the incorporation of the fiber.Firstly,the fiber is embedded in the coating and interrupts the continuity of the coating.With increasing processing time,the fiber is found to be reactively incorporated in the coating.The intention to produce a MgAl_(2)O_(4)containing coating is achieved and it is mainly accumulated near the coating surface.However,due to the low number of fibers,the Al content is overall still low and only near to the fibers the MgAl_(2)O_(4)spinel phase can form.
文摘Taguchi technique was used to predict the influence of processing parameters on the erosive wear behavior Al7034-T6composite reinforced with SiC and Al2O3particles in different mass fractions.These hybrid metal matrix composites(HMMCs)werefabricated by using a simple technique called stir casting technique.Scanning electron microscope(SEM)was used to study thesurface morphology of the composite and its evolution according to processing time.The design of experiment(DOE)based onTaguchi’s L16orthogonal array was used to identify various erosion trials.The most influencing parameter affecting the wear rate wasidentified.The results indicate that erosion wear rate of this hybrid composite is greatly influenced more by filler content and impactvelocity respectively compared to other factors.This also shows the significant wear resistance with the increase in the filler contentsof SiC and Al2O3particles,respectively.
基金the National Basic Research Program of China(Grant Nos.2011CBA00605 and 2010CB327501)the National Natural Science Foundation of China(Grant No.61106095)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011ZX02708-003)
文摘In0.4Ga0.6As channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with and without an Si-doped In0.49Ga0.51P barrier layer grown on semi-insulating GaAs substrates have been investigated for the first time. Compared with the In0.4Ga0.6As MOSFETs without an In0.49Ga0.51P barrier layer, In0.4Ga0.6As MOSFETs with an In0.49Ga0.51P barrier layer show higher drive current, higher transconductance, lower gate leakage current, lower subthreshold swing, and higher effective channel mobility. These In0.4Ga0.6As MOSFETs (gate length 2 μm) with an In0.49Ga0.51P barrier layer exhibit a high drive current of 117 mA/mm, a high transconductance of 71.9 mS/mm, and a maximum effective channel mobility of 1266 cm2/(V·s).
文摘The tensile strength of squeeze casting ZA22/Al 2O 3 short fiber composite was measured with autograph AG 10TA universal testing machines made in Japan. The experimental results were analysed with the rule of mixture(ROM) model modified by Friend. The theoretical analysis agree well with the experimental results. Under the test condition of this study, the strengthening critical fiber volume fraction predicted is 34 5%. Because fiber volume fraction in the composite is under this value, the tensile strength of the composite is lower than that of ZA22 alloy matrix.
文摘Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two kinetic models have been published [2-5]. In order to distinguish a kinetics model based on the ad- sorption capacity of a solid from the one based on the concentration of a solution, Lagergren's first-order rate equation has been called pseudo-first-order [6-7]. The Lagergren's equation has been widely cited, but there are far more mistakes made in the quotation and in the reference section of papers, including the title, the author's name, journal title, year of publishing, volume, and page number [3]. In addition, the second order kinetic expression for the adsorption systems of divalent metal ions using sphagnum moss peat has been reported by Ho [8].
基金National Natural Science Foundation of China (50372037)Scientific Research Foundations of Shaanxi University of Science and Technology (SUST-B14)
文摘SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and metallurgical microscope. The effects of technical parameters on the properties of the product were analyzed. The results indicate that the composite possesses a dense microstructure, composed of three interpenetrated phases. Of them, SiO2 layer prohibits the powdering of the composites; Mg promotes the wetting and infiltration of the system and Si restricts the interfacial reaction while improving the wetting ability between reinforcement and matrix.
文摘SiC particulates reinforced alumina matrix composites were fabricated using Directed Metal Oxidation (DIMOX) process. Continuous oxidation of an Al-Si-Mg-Zn alloy with different interlayers (dopents) as growth promoters, will encompasses the early heating of the alloy ingot, melting and continued heating to temperature in the narrow range of 950°C to 980°C in an atmosphere of oxygen. Varying interlayers (dopents) are incorporated to examine the growth conditions of the composite materials and to identification of suitable growth promoter. The process is extremely difficult because molten aluminum does not oxidize after prolonged duration at high temperatures due to the formation of a passivating oxide layer. It is known that the Lanxide Corporation had used a combination of dopents to cause the growth of alumina from molten metal. This growth was directed, i.e. the growth is allowed only in the required direction and restricted in the other directions. The react nature of the dopants was a trade secret. Though it is roughly known that Mg and Si in the Al melt can aid growth, additional dopents used, the temperatures at which the process was carried out, the experimental configurations that aided directed growth were not precisely known. In this paper we have evaluated the conditions in which composites can be grown in large enough sizes for evaluation application and have arrived at a procedure that enables the fabrication of large composite samples by determining the suitable growth promoter (dopant). Scanning electron microscopic, EDS analysis of the composite was found to contain a continuous network of Al2O3, which was predominantly free of grain-boundary phases, a continuous network of Al alloy. Fabrication of large enough samples was done only by the inventor company and the property measurements by the company were confirmed to those needed to enable immediate applications. Since there are a large number of variable affecting robust growth of the composite, fabrication large sized samples for measurements is a difficult task. In the present work, to identify a suitable window of parameters that enables robust growth of the composite has been attempted.
文摘1 Scope This standard specifies the classification, shape and dimensions, technical requirements, test methods, quality appraisal procedures, packing, marking, transportation, storage, and quality certificate of Al2O3- SiC - C bricks for hot metal pretreatment.
文摘1 Scope This standard specifies the classification, techni- cal requirements, test methods, inspection rules, packing, marking, transportation, storage and quality certificate of Al2O3- SiC - C bricks for hot metal pretreatment.
文摘This article shows main principles and presents ideas described in the scientific and technical literature, on the mechanism of interaction of microwave radiation with a solid phase materials, which were used as a basis of creation of new perspective, energy efficient and environmentally safe technologies of preparation of heterogeneous catalysts for the reactions which were carried out under the influence of electro-magnetic radiation of microwave radiation. Author’s research results confirm possibilities of practical use of proposed method of hydrothermal oxidation of industrial low-dispersing of aluminum powders with presence of bulk phase of Al(ОН)<sub>3</sub>·nH<sub>2</sub>O, with further thermal treatment in microwave field for acquisition of armored А1/А1<sub>2</sub>О3<sub>3</sub> compositions, which effectively consume energy of microwave radiation. Due to the textured characteristics and thermo-transforming ability, synthesized components can be used as potential universal bearings of catalysts for reactions stimulated by electromagnetic radiation of (2.45 GHz) microwave frequency.
基金financially supported by the research project of National Natural Science Foundation of China (Grant Nos.51662015 and 51462011)
文摘Owing to adjustable thermal expansion performance, BaO–CaO–Al_2O_3–B_2O_3–SiO_2(BCABS) glass has a promising commercialization prospect for intermediate temperature-solid oxide fuel cells(IT-SOFCs) sealing. Herein, Al_2O_3 with two different contents was added into the same glass formulation, referred to as A and B glass, respectively. In terms of the non-isothermal crystallization kinetic behavior, the effect of Al_2O_3 as the unique intermediate was innovatively studied on the long-term performance of BCABS sealing glass. After the heat treatment at 1023 K for 100 h, the change of the network structure and the expansion coefficient of the glass were characterized. The results showed that the addition of Al_2O_3 as a network forming body could enhance the structure of glass, and increase the activation energy for glass transition, which could effectively inhibit the crystallization ability of sealing glass. Therefore, the B glass with the higher Al_2O_3 content showed the better long-term sealing ability, which was greatly beneficial for IT-SOFCs sealing.
基金supported by the Ministry of Science and Technology of China (No. 2012AA062702,2010AA64905)the National Natural Science Foundation of China (No. 21077117)
文摘The effect of pretreatment on Pd/Al2O3 catalysts for the catalytic oxidation of o-xylene at low temperature was studied by changing the pretreatment and testing conditions. The fresh and pretreated Pd/Al2O3 catalysts were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results showed that the pretreatment dramatically changed the Pd/PdO ratio and then significantly affected the Pd/Al2O3 activity; while the pretreatment had not much influence on Pd particle size. The Pd/Al2O3 pre-reduced at 300~C/400~C, which has fully reduced Pd species, showed the highest activity; while the fresh Pd/Al2O3, which has fully oxidized Pd species, presented the worst performance, indicating the Pd chemical state plays an important role in the catalytic activity for the o-xylene oxidation. It is concluded that metallic Pd is the active species on the Pd/Al2O3 catalyst for the catalytic oxidation of o-xylene at low temperature.