Hydrothermal synthesis of boehmites with various particle sizes and transition to α-Al2O3 powders by calcination

Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2 O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100 nm, 0.4-0. 6μm and 1μm in size were obtained respectively by changing the hydrothermal precursors and the pH value of hydrothermal slurry. Calcination of boehmite powders of 30-100 nm at 1250℃ for 1h resulted in the formation of single-phase α-Al2O3,and the products consisted of vermicular particles. The boehmite powders of 0.4-0.6μm were also fully converted to α-Al2O3 at 1250℃, and the products consisted of plate-like particles with the same size of 0. 4-0. 6μm. The boehmite powders of 1μm calcined at 1350℃ for 2h were still composed of a little proportions of transition aluminas besides α-Al2 O3, and the particles sintered severely. The reaction processes for the formation of crystalline boehmites under hydrothermal conditions and α-Al2O3 powders during calcination have been discussed.     

Hydrothermal synthesis of boehmites with various particle sizes and transition to α-Al2O3 powders by calcination

Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2 O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100 nm, 0.4-0. 6μm and 1μm in size were obtained respectively by changing the hydrothermal precursors and the pH value of hydrothermal slurry. Calcination of boehmite powders of 30-100 nm at 1250℃ for 1h resulted in the formation of single-phase α-Al2O3,and the products consisted of vermicular particles. The boehmite powders of 0.4-0.6μm were also fully converted to α-Al2O3 at 1250℃, and the products consisted of plate-like particles with the same size of 0. 4-0. 6μm. The boehmite powders of 1μm calcined at 1350℃ for 2h were still composed of a little proportions of transition aluminas besides α-Al2 O3, and the particles sintered severely. The reaction processes for the formation of crystalline boehmites under hydrothermal conditions and α-Al2O3 powders during calcination have been discussed.     

Mossbauer spectroscopic studies the characterization of three China coal and the corresponding fly-ashes and bottom ashes

Three fresh China coals （lignitie, bituminite and anthracite） from different geological origin and the corresponding fly and bottom ashes were studied by room temperature（RT） Mossbauer spectroscopy（MS）. The iron-bearing minerals were characterized to be mainly pyrite in all coal samples by the hyperfine parameters.Suphate（FeSO4·nH2O） was found in bituminite and anthracite coal.The MSssbauer spectra of the fly and bottom ashes as a result of pulverised coal combustion（PCC） in Xiaolongtan,Shuicheng and Luohuang Power Plants are comprised of superimposed sextets and doulets of oxides includes maghemite（γ-Fe2O3）, magnitite（Fe3O4）, haematite（α-Fe2O3）, magnesioferite （MgFe2O4）, Fe^3＋/Fe^2＋ -mullite, Fe^3＋ -glass silicate and metallic iron. The studies also show that iron-bearing minerals in coals are largely dependant on geological regions and coal rank, the composition of the corresponding fly and bottom ashes will not only depend on the type and mineralogy of the feed coal but also on the local nature of combustion.     

Single-crystal tungsten-based alloys with molybdenum and rhenium

1IntroductionAlloys of the W-Mo-Re and W-Re systems exhibit a unique combination of physical,chemical,and me-chanical properties.These alloys are multifunctional materials that can operate under severe conditions[1].The potentialities of the alloys can be widened by opti mizing their chemical compositions and structures.The preparation of the alloys inthe region of substitutional solid solutions inthe formof single crystals al-lows one toincrease their physical and mechanical properties and …     

Palladium-rare-earth metal alloys-advanced materials for hydrogen power engineering

Hydrogen of no less than 99. 999 % (vol. fraction) purity is a principal power media of hydrogen power engineering. A single method for the preparation of high purity hydrogen consists in its separation from vapour-gas mixtures via the selective diffusion of hydrogen through a palladium membrane. The rate of hydrogen diffusion and the strength and stability during the operation in aggressive gases are important characteristics of palladium membranes. The increase in the strength, plasticity, and hydrogen-permeability of membrane alloys can be reached by alloying palladium with the formation of solid solutions.The formation of wide ranges of palladium-rare-earth metal (REM) solid solutions is an interesting feature of palladium. Earlier, we have shown that the alloying of Pd with REM substantially increases the rate of hydrogen diffusion and markedly increases the strength of palladium on retention of the adequate plasticity.In this work, we have studied alloys of the Pd-Y and Pd-Y-Me systems. It was shown that the following conditions should be satisfied to prepare high-quality alloys exhibiting high service properties: (1)the use of high-purity components (whose purity is no less than 99.95%, mass fraction), in particular,high-purity Y prepared by vacuum distillation, and (2) holding the reached purity for the final product.For this purpose, we suggested a cycle of manufacturing operations including the preparation of a vacuumtight foil of 50 (m thick as the final stage.The hydrogen-permeability of the alloys was measured at different temperatures and hydrogen pressures. The instability of operation of binary Pd-Y alloys w alloying the composition with a Ⅷ Group metal. For example, the alloy of the optimum composition Pd-8Y-Me in the annealed state exhibits the following mechanical properties: HV= 75 kg/mm2 , σu = 58 kg/mm2 , and δ= 20%. Its hydrogen-permeability (QH2) measured as a function of the temperature exceeds that of the Pd-23Ag alloy (that is widely used by foreign companies) by a factor of 1.5-2; it is 3.6-4.7 m3/m2 hMPa0.5 at 300-600℃, respectively.The alloys exhibiting the high hydrogen-permeability combined with the high mechanical properties shows promise as materials for diffusion hydrogen purification devices whose productivity reaches tens thousands nm3/h.     

Palladium-rare-earth metal alloys-advanced materials for hydrogen power engineering

Hydrogen of no less than 99. 999 , (vol. fraction) purity is a principal power media of hydrogen power engineering. A single method for the preparation of high purity hydrogen consists in its separation from vapour-gas mixtures via the selective diffusion of hydrogen through a palladium membrane. The rate of hydrogen diffusion and the strength and stability during the operation in aggressive gases are important characteristics of palladium membranes. The increase in the strength, plasticity, and hydrogen-permeability of membrane alloys can be reached by alloying palladium with the formation of solid solutions.The formation of wide ranges of palladium-rare-earth metal (REM) solid solutions is an interesting feature of palladium. Earlier, we have shown that the alloying of Pd with REM substantially increases the rate of hydrogen diffusion and markedly increases the strength of palladium on retention of the adequate plasticity.In this work, we have studied alloys of the Pd-Y and Pd-Y-Me systems. It was shown that the following conditions should be satisfied to prepare high-quality alloys exhibiting high service properties: (1)the use of high-purity components (whose purity is no less than 99.95,, mass fraction), in particular,high-purity Y prepared by vacuum distillation, and (2) holding the reached purity for the final product.For this purpose, we suggested a cycle of manufacturing operations including the preparation of a vacuumtight foil of 50 (m thick as the final stage.The hydrogen-permeability of the alloys was measured at different temperatures and hydrogen pressures. The instability of operation of binary Pd-Y alloys w alloying the composition with a Ⅷ Group metal. For example, the alloy of the optimum composition Pd-8Y-Me in the annealed state exhibits the following mechanical properties: HV= 75 kg/mm2 , σu = 58 kg/mm2 , and δ= 20,. Its hydrogen-permeability (QH2) measured as a function of the temperature exceeds that of the Pd-23Ag alloy (that is widely used by foreign companies) by a factor of 1.5-2; it is 3.6-4.7 m3/m2 hMPa0.5 at 300-600℃, respectively.The alloys exhibiting the high hydrogen-permeability combined with the high mechanical properties shows promise as materials for diffusion hydrogen purification devices whose productivity reaches tens thousands nm3/h.     

Study on the reaction activity of CuO／γ-Al2O3 for dry flue gas desulfurization

The copper oxide bed regenerable adsorber process can efficiently remove sulfur dioxide (SO2) and sulfur trioxide (SO3) and reduce nitrogen oxides (NOx) from flue gas with no solid or liquid byproducts. This paper investigates the dry flue gas desulfurization activities of the CuO/γ-Al2O3 under different operation conditions finding that the dispersion degree of copper oxide can achieve a threshold value, which is 0.47mg/m^2 carriers. The conclusion confirms that the sulfur capacity of desulfurizer is associated with flue gas‘ space velocity, reaction temperature, copper content and the structure of sorbent pellet, etc. And with the condition of the desulfurization reaction temperature 673 K, the space velocity 11 200 h^-1 and the S/Cu mole ratio under 1, the sulfur removal efficiency can go upwards to 95%.     

Influence of ultrasonic on the coking amount of catalyst （Ni/γ-Al2O3） for the dry reforming of benzene

The Influence of ultrasonic treatment on the coking amount of a nickel-based catalyst （Ni/γ-Al2O3） for the reaction of reforming with carbon dioxide of Benzene was investigated. The results show that ultrasonic treatment modify the pore size distribution of the catalysts significantly and also reduce the amount of coke formed on the catalyst. The reduction in the coking amount is not sensitive to the power output of the ultrasonic treatment device in the power range tested （120 W and 500 W）.     

Effect of additive V2O5 on sintering mechanism and properties of inert anodes of NiFe2O4 spinel

In order to improve the properties of inert anode of NiFe2O4 spinel, some additive V2O5 was added to raw materials-powders of NiO and Fe2O3. The powders of NiO, Fe2O3 were mixed with slight amount of V2O5, then they are moulded and sintered at 1200℃ for 6h. The sintering mechanism of powders of NiO and Fe2O3 with some additive V2 O5 was researched. The effect of V2O5 on density, electrical conductivity and corrosion resistance of inert anode of NiFe2O4 spinel was studied at the same time. The results show that the sintering mechanism for powders of NiO and Fe2O3 with some additive V2O5 is liquid-phase sintering. Additive V2O5 can increase the density of the samples, especially it improves the corrosion resistance of the samples remarkably. When the amount of V2 O5 is 1.5 ,, the sample''s corrosion rate is 1/80 of that of sample without V2 O5. But the electrical conductivity of the samples with V2O5 is lower than that of the sample without V2O5.     

高纯超细氧化铝粉的制备(Ⅱ)--煅烧过程对氧化铝粉性能的影响

煅烧温度和时间对氧化铝粉的晶型和形貌有很大影响;氧化铝粉晶型的转变顺序及温度为:无定形氢氧化铝600℃,5h→无定形氧化铝800℃,5h→γ-Al22O3(θ-Al2O3,η-Al2O3)1000℃,5h→δ-Al2O3(θ-Al2O3,κ-Al2O3)1100℃,5h→α-Al2O3;将分散的氢氧化铝粉在1150℃煅烧5 h后制得球形的α-Al2O3粉末.     

Highly effective sorbents obtained by treating agrowaste products in cold plasma

Sorbents are widely used in purification of various liquids and gases, offering a universal means for wastewater and air cleaning. The most promising sorbents are those obtained from agrowaste products such as rice or buckwheat husk. Processing of husk in cold plasma modifies the composition, structure and surface properties of the raw material and raises its porosity, thus substantially improving the sorption properties of the final product.Husk as a raw material for producing sorbents has the following advantageous properties: (1) appropriate chemical composition; (2) low cost; (3) high dispersity, due to which there is no need in any special treatment of the material prior to its exposing to plasma; (4) scaly structure and developed porous surface ensuring a high surface-to-volume ratio. The best properties are displayed by the sorbents obtained in cold plasma under reduced pressures of 53.2 Pa. The raw naterial traverses the region occupied by the plasma and, as it does so, it gets heated up to a temperature of 250 - 350 ℃. The whole process involves two stages: combustion of the raw material and modification of its properties under the action of the plasma. The combustion proceeds due to the oxygen contained in the starting material. During the combustion, the hydrogen contained in the starting material and some part of the carbon also burn out.The resultant scaly sorbent is accumulated in a cooler. The scales are black; they range in sizes from 1mm to 5 mm.The sorbents obtained are remarkable for their useful properties and outperform most of the traditional sorbents used in modern industry. The starting materials are inexpensive, and their resources are almost unlimited. The sorbents have rather a low production cost (1.8-2.5($)/kg). The sorbents can be used for cleaning hydrosphere from water pollutants on a large scale. The degree of cleaning water surface from oil products with sorbents was a subject of investigation. The highest degree of purification the sewages up to 96.6, was observed in those cases where sorbents obtained from rice and buckwheat husk were used. Another advantageous feature of the sorbents stems from the practical good that can be benefited from their utilization. The sorbents saturated with pollutants can be used as fuel or in producing asphalt concrete. The sorbents may prove useful in pharmaceutical and food industries. Most advantageous conditions for producing such sorbents are available in rice-growing countries such as China, India, Japan and Korea.     

Highly effective sorbents obtained by treating agrowaste products in cold plasma

Sorbents are widely used in purification of various liquids and gases, offering a universal means for wastewater and air cleaning. The most promising sorbents are those obtained from agrowaste products such as rice or buckwheat husk. Processing of husk in cold plasma modifies the composition, structure and surface properties of the raw material and raises its porosity, thus substantially improving the sorption properties of the final product.Husk as a raw material for producing sorbents has the following advantageous properties: (1) appropriate chemical composition; (2) low cost; (3) high dispersity, due to which there is no need in any special treatment of the material prior to its exposing to plasma; (4) scaly structure and developed porous surface ensuring a high surface-to-volume ratio. The best properties are displayed by the sorbents obtained in cold plasma under reduced pressures of 53.2 Pa. The raw naterial traverses the region occupied by the plasma and, as it does so, it gets heated up to a temperature of 250 - 350 ℃. The whole process involves two stages: combustion of the raw material and modification of its properties under the action of the plasma. The combustion proceeds due to the oxygen contained in the starting material. During the combustion, the hydrogen contained in the starting material and some part of the carbon also burn out.The resultant scaly sorbent is accumulated in a cooler. The scales are black; they range in sizes from 1mm to 5 mm.The sorbents obtained are remarkable for their useful properties and outperform most of the traditional sorbents used in modern industry. The starting materials are inexpensive, and their resources are almost unlimited. The sorbents have rather a low production cost (1.8-2.5($)/kg). The sorbents can be used for cleaning hydrosphere from water pollutants on a large scale. The degree of cleaning water surface from oil products with sorbents was a subject of investigation. The highest degree of purification the sewages up to 96.6% was observed in those cases where sorbents obtained from rice and buckwheat husk were used. Another advantageous feature of the sorbents stems from the practical good that can be benefited from their utilization. The sorbents saturated with pollutants can be used as fuel or in producing asphalt concrete. The sorbents may prove useful in pharmaceutical and food industries. Most advantageous conditions for producing such sorbents are available in rice-growing countries such as China, India, Japan and Korea.     

Preparation and properties of nano-composite ceramic coating by thermo chemical reaction method

Nano-composite ceramic coating was fabricated on Q235 steel through thermo chemical reaction method. Structure of the coating was analyzed and the properties were tested. The results show that a few of new ceramic phases, such as MgAI2O4, ZnAI2O4, AI2SiO5, Ni3Fe and Fe3AI, are formed on the coating during the process of solidifying at 600 ℃. The ceramic coating is dense and the high bonding strength is obtained. The average bonding strength between the coating and matrix could be 14.22 MPa. The acid resistance of the coating increase by 8.8 times, the alkali resistance by 4.1 times, the salt resistance bv 10.3 times, and the wear resistance bv 2.39 times.     

Effect of the directional crystallization on microstructure of Ti46Al-5Nb-1W

Ti-Al based intermetallic alloys are promising for various applications in aerospace and automobile industry. Their favorable properties, such as low density and good corrosion resistance, are accompanied on the other hand by low toughness and very difficult metallurgy. One of the possibilities to improve the toughness of Ti-46Al-5Nb-1W (%, at. fraction) alloy consists in change of their microstructure into lamellar microstructure, which can be reached moreover by directional crystallization. This experiment is described in this paper. Samples of the Ti-46Al-5Nb-1W (%, at. fraction) alloy prepared by plasma and vacuum-induction metallurgy were subjected to directional crystallization. Cooling rates were constant and ranged from 5.56 × 10-6 m/s to 1.18 × 10 -4 m/s. Directional crystallization has been accomplished in ceramic tubes made of corundum-Al2O3. The samples were studied by metallographic and chemical analysis.Lamellar microstructure of the samples was found to consist of α2- and γ-phase lamellas. Moreover, ceramic particles Al2O3 were found to be present in the samples. Distribution of the alloying elements in the samples was homogenous.     

New materials and biologically active preparations on the basis of (organilthio) chloroacetylene

(Organylthio)chloroacetylenes [RSC≡CCl, 1], the object of our systematic research, provide a promising source of new classes of polyfunctional compounds of acetylenic and polyheterocyclic seriesamong which biologically active substances, monomers and precursors for the preparation of new materials possessing a whole complex of valuable properties have been recognized.     

New materials and biologically active preparations on the basis of (organilthio) chloroacetylene

(Organylthio)chloroacetylenes [RSC≡CCl, 1], the object of our systematic research, provide a promising source of new classes of polyfunctional compounds of acetylenic and polyheterocyclic seriesamong which biologically active substances, monomers and precursors for the preparation of new materials possessing a whole complex of valuable properties have been recognized.……     

Gradient nature shaping of the 20X2H4A steel structure as a carbonitriding result

The study of the shaping of the gradient structure nature appearing in constructional alloy martensite20X2H4Asteel(0.2%C,2%Cr,4%Ni),as a result of surface saturation by carbon and nitrogen(carboni-triding)at920℃inindustrial conditions is madein present work by methods of optical and transmission e-lectron microscopy.20X2H4Asteel is a multiphase material,consisting inαandγphases,and cementite(Fe,Cr)3C,al-loyed by Cr in initial state butαandγphases,(Fe,Cr)3C carbide and(Cr,Fe)23(C,N)…     

Effect of the directional crystallization on microstructure of Ti46Al-5Nb-1W

Ti-Al based intermetallic alloys are promising for various applications in aerospace and automobile industry. Their favorable properties, such as low density and good corrosion resistance, are accompanied on the other hand by low toughness and very difficult metallurgy. One of the possibilities to improve the toughness of Ti-46Al-5Nb-1W (,, at. fraction) alloy consists in change of their microstructure into lamellar microstructure, which can be reached moreover by directional crystallization. This experiment is described in this paper. Samples of the Ti-46Al-5Nb-1W (,, at. fraction) alloy prepared by plasma and vacuum-induction metallurgy were subjected to directional crystallization. Cooling rates were constant and ranged from 5.56 × 10-6 m/s to 1.18 × 10 -4 m/s. Directional crystallization has been accomplished in ceramic tubes made of corundum-Al2O3. The samples were studied by metallographic and chemical analysis.Lamellar microstructure of the samples was found to consist of α2- and γ-phase lamellas. Moreover, ceramic particles Al2O3 were found to be present in the samples. Distribution of the alloying elements in the samples was homogenous.     

Solvothermal synthesis and reaction mechanism of CoO nanoparticles

Pure CoO nanoparticles have been synthesized using solvothermal method at 150℃ with Co(CH3COO)2 · 4H2O and anhydrous ethanol as reactants. SEM, TEM and XRD were employed to characterize the size, morphology and crystalline structure of the as-synthesized CoO nanoparti cles. It is revealed that the CoO nanoparticles are of octahedron configuration in face-centered cubic (FCC) structure with a lattice constant of 0. 426 nm and have an average particle size of about 50 nm. Typically, when the concentration of Co(CH3COO)2·4H2O in CH3CH2OH reduces from 0.24 mol/L to 0.08 mol/L, the size of CoO nanoparticles decreases from 500 nm to 50 nm. Based on the results of IR analysis of the finished reaction liquid and XRD of products, the reaction mech anism of the solvothermal system has been discussed.     

Solvothermal synthesis and reaction mechanism of CoO nanoparticles

Pure CoO nanoparticles have been synthesized using solvothermal method at 150℃ with Co(CH3COO)2 · 4H2O and anhydrous ethanol as reactants. SEM, TEM and XRD were employed to characterize the size, morphology and crystalline structure of the as-synthesized CoO nanoparti cles. It is revealed that the CoO nanoparticles are of octahedron configuration in face-centered cubic (FCC) structure with a lattice constant of 0. 426 nm and have an average particle size of about 50 nm. Typically, when the concentration of Co(CH3COO)2·4H2O in CH3CH2OH reduces from 0.24 mol/L to 0.08 mol/L, the size of CoO nanoparticles decreases from 500 nm to 50 nm. Based on the results of IR analysis of the finished reaction liquid and XRD of products, the reaction mech anism of the solvothermal system has been discussed.