Combined Promoting Effects of Specific Organic Functional Groups and Alumina Surface Characteristics for the Design of a Highly Efficient NiMo/Al_(2)O_(3) Hydrodesulfurization Catalyst

To prepare a highly efficient NiMo/Al_(2)O_(3) hydrodesulfurization catalyst,the combined effects of specific organic functional groups and alumina surface characteristics were investigated.First,the correlation between the surface characteristics of four different alumina and the existing Mo species states was established.It was found that the Mo equilibrium adsorption capacity can be used as a specific descriptor to quantitatively evaluate the changes in surface characteristics of different alumina.A lower Mo equilibrium adsorption capacity for alumina means weaker metal-support interaction and the loaded Mo species are easier to transform into MoS2.However,the Mo-O-Al bonds still exist at the metal-support interface.The introduction of cationic surfactant hecadecyl trimethyl ammonium bromide(CTAB)can further improve Mo species dispersion through electrostatic attraction with Mo anions and interaction of its alkyl chain with the alumina surface;meanwhile,the introduction of ethylenediamine tetraacetic acid(EDTA)can complex with Ni ions to enhance the Ni-promoting effect on Mo.Therefore,the NiMo catalyst designed using alumina with lower Mo equilibrium adsorption capacity and the simultaneous addition of EDTA and CTAB exhibits the highest hydrodesulfurization activity for 4,6-dimethyl dibenzothiophene because of its proper metal-support interaction and more well-dispersed Ni-Mo-S active phases.

Measurement of alumina film induced ablation of internal insulator in solid rocket environment

This study investigates the ablation of internal insulation induced by the deposition of an alumina film with different lateral film speeds.A sub-scale test solid rocket motor(SRM)was designed in an impinging jet configuration to form an alumina film on the sample and to encourage the lateral movement of the film by a high-speed wall jet.Fifteen static fire tests of the test SRM were conducted with six different jet velocities(V_(jet)=100 m/s,150 m/s,200 m/s,268 m/s,330 m/s,and 450 m/s)that indirectly affected the velocity of the wall jet and the deposition rate of alumina droplets.The ablation velocity was deduced from the difference in the sample thickness after a test using a coordinate measuring machine.The droplet deposition mass flux and wall jet velocity were obtained via two-phase flow simulation with the same jet velocity and effective pressure.As a result,the characteristics of alumina-induced ablation and the changes in ablation with jet velocities were obtained.The area within0.8×jet diameter was focused upon,where the ratio of ablation velocity to incoming alumina mass was constant for each jet velocity,and showed a similarity in jet structure.When the ablation velocity was increased from 2.05 to 9.98 mm/s with increasing jet velocity,the ratio of the ablation velocity and alumina mass flux decreased from 1.07×10^(-4)to 0.49×10^(-4)m^(3)/kg as Al_(2)O_(3)-C reactions became less efficient with a reduced residence time of the film.Because the decrease in residence time by the wall jet is more pronounced for slow reactions involved in Al_(2)O_(3)-C reactions,fast reactions in Al_(2)O_(3)-C reactions are less affected and result in a convergence of the volumetric rate of ablation per unit mass of alumina.

Piezoresistive behavior of elastomer composites with segregated network of carbon nanostructures and alumina

Electrically conductive elastomer composites(CECs)with segregated networks of conductive nanofillers show high potential in stretchable strain sensors due to balanced mechanical and electrical properties,yet the sensitivity at low strain is generally insufficient for practical application.Herein,we report an easy and effective way to improve the resistive response to low strain for CECs with segregated network structure via adding stiff alumina into carbon nanostructures(CNS).The CEC containing 0.7 wt%CNS and 5 wt%Al_(2)O_(3) almost sustains the same elasticity(elongation at break of~900%)and conductivity(0.8 S/m)as the control,while the piezoresistive sensitivity is significantly improved.Thermoplastic polyurethane(TPU)composites with a segregated network of hybrid nanofillers(CNS and Al_(2)O_(3))show much higher strain sensitivity(Gauge factor,GF-566)at low strain(45%strain)due to a local stress concentration effect,this sensitivity is superior to that of TPU/CNS composites(GF-11).Such a local stress concentration effect depends on alumina content and its distribution at the TPU particle interface.In addition,CECs with hybrid fillers show better reproducibility in cyclic piezoresistive behavior testing than the control.This work offers an easy method for fabricating CECs with a segregated filler network offering stretchable strain sensors with a high strain sensitivity.

Analysis of the Performances of a New Type of Alumina Nanocomposite Structural Material Designed for the Thermal Insulation of High-Rise Buildings

The sol-gel method is used to prepare a new nano-alumina aerogel structure and the thermal properties of this nanomaterial are investigated comprehensively using electron microscope scanning,thermal analysis,X-ray and infrared spectrometer analysis methods.It is found that the composite aerogel alumina material has a multi-level porous nano-network structure.When employed for the thermal insulation of high-rise buildings,the alumina nanocomposite aerogel material can lead to effective energy savings in winter.However,it has almost no energy-saving effect on buildings where energy is consumed for cooling in summer.

Influence of Firing Temperature on Properties of High Alumina Bricks

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.

Analysis of Corrosion Mechanisms of Low-cement or No-cement Al_(2)O_(3)-MgO Gunning Mix with Special Calcined Alumina in Rotary Slag Test

Al_(2)O_(3)-MgO and Al_(2)O_(3)-spinel low cement castables(LCC-AM and LCC-AS)have been extensively used in steel ladles as working linings.Nevertheless,the use of alumina-magnesia gunning mixes has been mainly kept for maintaining these castable linings,because of high rebound loss,poor green strength,high porosity and short life-span.Thanks to a high BET alumina(MC-G),it is now possible to develop a series of high-performance no-cement or low-cement Al_(2)O_(3)-MgO gunning mixes(NCG-AM or LCG-AM).The paper focuses on the BOF slag resistance of NCG-AM,LCG-AM,LCC-AM and LCC-AS.The corrosion mechanisms of rotary slag samples were studied by scanning electron microscopy(SEM/EDS).The results reveal different microstructures around MgO particles,depending on the four used compositions.Continuous and thicker spinel phases were formed in NCG-AM,which was proved to have the best corrosion resistance after the dynamic slag test.MC-G can provide a high diffusion flux of Al^(3+)in terms of kinetics and hence inhibits Kirkendall porosity around MgO particles.In addition,a continuous spinel phase acts like a pinning nail to reinforce the matrix and thus decreases erosion by slag.In contrast to NCG-AM,the porous spinel phase was found around unreacted MgO particles and some particles were carried away near the interface of LCC-AM and slag.The NCG-AM containing MC-G had been tested in two steel plants,and it extended the service life of the ladles up to 50%.In addition,this study suggests the potential application of NCG-AM as steel ladle linings.

Carbon dioxide reforming of methane over mesoporous nickel aluminate/γ-alumina composites

A series of x NiAl_2O_4/γ-Al_2O_3 composites with various Ni contents have been prepared via one-step partial hydrolysis of metal nitrate salts in the absence of surfactants and used for carbon dioxide reforming of methane. The characterization results demonstrated that the Ni Al_2O_4/γ-Al_2O_3 materials possessed mesoporous structures of uniform pore sizes; and the Ni^(2+) ions were completely reacted with alumina to Ni Al_2O_4 spinel in the matrices using N2 sorption, XRD, TEM, and XPS. The Ni Al_2O_4/γ-Al_2O_3 materials exhibited excellent catalytic properties and superior long-term stability for carbon dioxide reforming of methane. The effects of Ni content on the intrinsic activities and the amounts of coke disposition of the x NiAl_2O_4/γ-Al_2O_3 catalysts were discussed in detail for the carbon dioxide reforming of methane. The results revealed that the Ni particle sizes did not affect the intrinsic activity of metallic Ni, but smaller Ni particles could reduce the rate of coke deposition.

In-Ceram alumina全瓷冠边缘和内部适合性的研究

随着In-Ceram alumina全瓷冠在临床上的广泛应用，其适合性的问题引起了越来越多的关注．因此本研究对其边缘和内部适合性进行了研究。为临床应用提供理论依据。

Application of Activated Alumina Powders in Corundum Castables

There are many brands of activated alumina powders in the market and the products from different manufacturers exist subtle differences. In this work, four brands of activated alumina powder which are the mainstream products in China with the same marked particle size of 2-3 μm were added to corundum castables to investigate the effect of different activated alumina powder on properties of corundum castables. It is found that the multi-peak distribution, round-shape particle,low impurities content of alumina powder are of great benefit to the improvement of the overall performance of castables.Obvious CA6 frame structure formed in castables matrix is conductive to improving the thermal shock resistance and high temperature strength of castables. One kind of domestic alumina micropowder studied in this work has good application value and prospect in corundum castables because of the excellent comprehensive performance.

Fabrication of Fibrous Mullite-alumina Ceramic with High Strength and Low Thermal Conductivity

Optimizing highly porous fibrous ceramics, like bird’s nest structure, were obtained by vacuum impregnation method with mullite fibers and alumina sol as raw material. The influences of impregnation cycles on the property of the sample, such as porosity, compressive strength and room-temperature thermal conductivity were explored. The experimental results show that the 3D skeleton structure of the sample was constructed by the randomly arranged mullite fibers and inorganic particles. The content of alumina can be adjusted effectively by impregnation times and it increases with increasing impregnation cycles. The thermal conductivity and compressive strength can also be controlled via tailored impregnation cycles. The compressive strength of fibrous ceramic ranged from 1.03 MPa to 5.31 MPa, while the porosity decrease slightly from 85.3% to 73.8%. In the same time, the thermal conductivity increase from 0.037 W/(m·K) to 0.217 W/(m·K), indicating that the fibrous ceramic with high impressive and low thermal conductivity can be fabricated by impregnation method.

Simultaneous determination of NaOH, Na_2CO_3 and Al_2O_3 in sodium aluminate solutions by flow injection titration

A flow injection titration method for simultaneous determination of hydroxide, carbonate and alumina in sodium aluminate solutions was proposed. 150?μL sample was injected and firstly reacted with a mixture of methyl orange, phenolphthalein and sulfosalicylic acid, and secondly, a mixture of chlorhydric acid, ammonium fluoride and phenolphthalein. Methyl orange and phenolphthalein in the first are the corresponding indicators for the determination of hydroxide and carbonate; sulfosalicylic acid is both the titrant and masking agent for aluminum. Ammonium fluoride in the second is complexing agent for alumina and makes it release corresponding amounts of hydroxide ion to aluminum; phenolphthalein is the corresponding indicator for the determination of hydroxide, carbonate and alumina. Chlorhydric acid is the titrant agent for the three. The proposed method can be employed to analyze aluminate solutions containing hydroxide 3.1 ～ 15.5?g/L -1 , carbonate 3.1 ～ 15.5?g/L -1 and alumina 0.51 ～ 1.02?g/L -1 with a sampling frequency of 30 samples per hour. 0.54% and 0.89% are the RSD of sodium oxide and of alumina respectively ( n = 11 ).

Influence of Setting Accelerating Agents on Properties of Colloidal Alumina Bonded Corundum Castables

In order to improve the flow ability and early-stage strength of colloidal alumina bonded corundum castables,the colloidal alumina with 20%of solid content was used as the binder,and tabular corundum aggregates and fines,and active alumina micropowder CL370 as the main starting materials.Influences of setting accelerating agents(magnesia fines and sodium meta-aluminate)on the linear change rate,the modulus of rupture and the microstructure of corundum castables after different heat-treatments were researched.The results show(1)cement bonded corundum castables have the highest modulus of rupture after 24 h of demolding,and colloidal alumina bonded corundum castables have the lowest one;both magnesia fines and sodium meta-aluminate can improve the strength after 24 h of demolding;(2)after firing at 1000℃for 3 h,the modulus of rupture of all specimens decreases,even lower than that after 24 h of demolding;(3)after firing at 1600℃for 3 h,the castable specimen added with 0.1 mass%magnesia fines has the highest modulus of rupture;the tabular phases appear interwovenly in the specimen;(4)taking the comprehensive properties into account,0.1 mass%of magnesia fines is appropriate,and the addition of sodium meta-aluminate shall be lower than 0.3%.

Development of Na-beta alumina batteries at Pacific Northwest National Laboratory:From tubular to planar

Na-beta alumina batteries are one of the most promising technologies for renewable energy storage and grid applications. Na-beta alumina batteries can be constructed in either tubular or planar designs, depending on the shape of the beta-alumina solid electrolyte. The tubular designs have been widely studied and developed since the 1960 s primarily because of their ease of sealing. However, planar designs are considered superior to tubular designs in terms of power output, cell packing, ease of assembly, thermal management, and other characteristics. Recently, Pacific Northwest National Laboratory has begun to develop high-performance planar Na-beta alumina batteries. In this paper, we provide an overview on the basic battery electrochemistry, solid electrolyte synthesis and fabrication, and our recent progress in developing planar batteries. Future trends for further technology improvement will also be presented.

Influence of Reactive Alumina and Calcined Alumina on properties of Free Flowing Castables

Reactive alumina is a well-established group of raw materials for refractory castables to improve their rheological behavior.In this article the influence of bimodal reactive alumina and standard(<325#)calcined alumina on workability,packing density and strength of alumina based castables is examined.It will be shown that there is a significant effect on water demand and apparent density of the castable,which is depending on the percentage of reactive alumina on the one hand and on the type of reactive alumina on the other hand.The effect of the alumina on setting time and cold crushing strength has shown to be insignificant in this set of experiments.

Effects of Four Kinds of Alumina Micropowder on Properties of Al_(2)O_(3)-C Refractories

In order to further improve the strength and the thermal shock resistance of Al_(2)O_(3)-C materials for steel ladle slide gates,the effects of four kinds of alumina micropowders(unimodal activated alumina micropowder 07RAL,unimodal activated alumina micropowder 15RA,bimodal activated alumina micropowder 22RABL,and calcined alumina micropowder 40CA)on the density,the strength and the thermal shock resistance of Al_(2)O_(3)-C materials were studied.The results show that the density,the strength and the thermal shock resistance of Al_(2)O_(3)-C materials can be improved with the introduction of activated alumina micropowders.Among them,the specimen with bimodal activated alumina micropowder shows the best comprehensive performance,especially the hot modulus of rupture.Its actual application results in steel mills show that the average service life of the Al_(2)O_(3)-C slide plates prolongs,and the problems of cast hole reaming,plate oxidation,roughening and cracking during the use of slide plates are obviously improved.

Effect of Industrial Alumina Powder Particle Size on Preparation of Active α-Al_(2)O_(3) Micropowder

To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al_(2)O_(3) micropowder),the fine powders with the median diameter of 50,30,10,and 5 pm,respectively,were obtained by grinding industrial alumina powder(the median diameter of 80 pm),and the active alumina micropowders were prepared by firing the industrial alumina powders before and after grinding at 1320℃ for 5 h.The effect of the particle size of the industrial alumina powder on the microstructure and properties of the active alumina micropowder was researched.The results indicate that the initial particle size of the industrial alumina powder has a great influence on the grain morphology of the active alumina micropowder;when the median diameter is larger than 30 pm,the α-Al_(2)O_(3) grains show wormlike aggregates state after calcination and when it is around or less than 10 pm,the α-Al_(2)O_(3) are round,spherical and well dispersed grains with the particle size of 0.3-1.0 pm.With the initial particle size of the industrial alumina powder decreasing,the α-Al_(2)O_(3) phase transition rate increases and the true density gradually increases;moreover,the α-Al_(2)O_(3) powder shows better dispersity and flowability.

Catalytic performances of kaoline and silica alumina in the thermal degradation of polypropylene

Polypropylene was cracked thermally and catalytically in the presence of kaoline and silica alumina in a semi batch reactor in the temperature range 400℃～550℃ in order to obtain suitable liquid fuels.The dependencies between process temperatures,types of catalyst,feed compositions and product yields of the obtained fuel fractions were found.It was observed that up to 450℃ thermal cracking temperature,the major product of pyrolysis was liquid oil and the major product at other higher temperatures(475℃～550℃) are viscous liquid or wax and the highest yield of pyrolysis product is 82.85% by weight at 500℃.Use of kaoline and silica alumina decreased the reaction time and increased the yield of liquid fraction.Again the major pyrolysis product in catalytic pyrolysis at all temperatures was low viscous liquid oil.Silica alumina was found better as compared to kaoline in liquid yield and in reducing the reaction temperature.The maximum oil yield using silica alumina and kaoline catalyst are 91% and 89.5% respectively.On the basis of the obtained results hypothetical continuous process of waste polypropylene plastics processing for engine fuel production can be presented.

Study on Microstructure of Alumina Based Rare Earth Ceramic Composite

Analysis techniques such as SEM, TEM and EDAX were used to investigate the microstructure of rare earth reinforced Al2O3/(W, Ti)C ceramic composite. Chemical and physical compatibility of the composite was analyzed and interfacial microstructure was studied in detail. It is found that both Al2O3 and (W, Ti)C phases are interlaced with each other to form the skeleton structure in the composite. A small amount of pores and glass phases are observed inside the material which will inevitably influence the physical and mechanical property of the composite. Thermal residual stresses resulted from thermal expansion mismatch can then lead to the emergence of dislocations and microcracks. Interfaces and boundaries of different types are found to exist inside the Al2O3/(W, Ti)C rare earth ceramic composite, which is concerned with the addition of rare earth element and the extent of solid solution of ceramic phases.

Studies on the Catalytic Properties of Magnesia Supported on γ-Alumina

We have shown that MgO can be dispersed on γ Al 2O 3 with different loadings. The observed dispersion capacity of MgO on the surface of γ Al 2O 3 is higher than the theoretical monolayer dispersion value. The surface area and the maximum in the pore size distribution gradually decrease with the increase in MgO content at low loadings. The surface area and the maximum in the pore size distribution of MgO/ γ Al 2O 3 decrease more rapidly when the MgO content is large because the pores of γ Al 2O 3 become blocked. When small amounts of MgO are dispersed on the surface of γ Al 2O 3, the catalyst is very active and shows a good selectivity for the synthesis of glycol ethers.

The Role of Vanadia for the Selective Oxidation of Benzyl Alcohol over Heteropolymolybdate Supported on Alumina

A series of 12-molybdophosphoric acid (MPA) supported on V2O5 dispersed γ-Al2O3 catalysts with different vanadia loadings were prepared by impregnation and characterized by N2 adsorption-desorption, X-ray diffraction, temperature-programmed reduction, in situ laser Raman spectroscopy, UV-Vis diffused reflectance spectroscopy, scanning electron microscopy, and temperature-programmed desorption of NH3 techniques. Their catalytic activities were evaluated for the vapor phase aerobic oxidation of benzyl alcohol. The catalysts exhibited high catalytic activity and the conversion of benzyl alcohol depended on the vanadia content while the catalyst with 15 wt% V2O5 content showed optimum activity. The characterization results suggest the presence of well-dispersed V2O5 and partially disintegrated Keggin ions of MPA on the support. In situ Raman studies showed a reduced Mo(IV) species when the catalysts were calcined at high temperatures. The high oxidation activity of the catalysts is related to the synergistic effect between MPA and V2O5.