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.

Nano-alumina@cellulose-coated separators with the reinforcedconcrete-like structure for high-safety lithium-ion batteries

Separators play a critical role in the safety and performance of lithium-ion batteries.However,commercial polyolefin separators are limited by their poor affinity with electrolytes and low melting points.In this work,we constructed a reinforced-concrete-like structure by homogeneously dispersing nano-Al_(2)O_(3) and cellulose on the separators to improve their stability and performance.In this reinforcedconcrete-like structure,the cellulose is a reinforcing mesh,and the nano-Al_(2)O_(3) acts as concrete to support the separator.After constructing the reinforced-concrete-like structure,the separators exhibit good stability even at 200℃(thermal shrinkage of 0.3%),enhanced tensile strain(tensile stress of 133.4 MPa and tensile strains of 62%),and better electrolyte wettability(a contact angle of 6.5°).Combining these advantages,the cells with nano-Al_(2)O_(3)@cellulose-coated separators exhibit stable cycling performance and good rate performance.Therefore,the construction of the reinforced-concretelike structure is a promising technology to promote the application of lithium-ion batteries in extreme environments.

Formation mechanism of nanopores in dense films of anodic alumina

Constant-current anodization of pure aluminum was carried out in non-corrosive capacitor working electrolytes to study the formation mechanism of nanopores in the anodic oxide films.Through comparative experiments,nanopores are found in the anodic films formed in the electrolytes after high-temperature storage(HTS)at 130°C for 240 h.A comparison of the voltage-time curves suggests that the formation of nanopores results from the decrease in formation efficiency of anodic oxide films rather than the corrosion of the electrolytes.FT-IR and UV spectra analysis shows that carboxylate and ethylene glycol in electrolytes can easily react by esterification at high temperatures.Combining the electronic current theory and oxygen bubble mold effect,the change in electrolyte composition could increase the electronic current in the anodizing process.The electronic current decreases the formation efficiency of anodic oxide films,and oxygen bubbles accompanying electronic current lead to the formation of nanopores in the dense films.The continuous electronic current and oxygen bubbles are the prerequisites for the formation of porous anodic oxides rather than the traditional field-assisted dissolution model.

Effect of Slag Basicity on Alumina Dissolution and Diffusivity:A High-temperature Confocal Laser Scanning Microscopy Study

Alumina is one of the crucial and extensively utilized refractory components.As the refractory wear due to dissolution at elevated temperatures during operation is a major threat to refractory lifespan,quantifying dissolution is important for developing cost-effective and resource-efficient refractories.This study investigated the dissolution of alumina particles in two silicate and one calcium aluminate slags at 1450,1500,and 1550°C using high-temperature confocal laser scanning microscopy(HT-CLSM).Dissolution was quantified in terms of diffusivity,with all influencing factors,including Stefan flow and bath movement,incorporated into the determination process.The trends observed in total dissolution time and diffusivity in three slags at three experimental temperatures could not be explained solely on the basis of slag basicity.Two parameters,considering the influencing factors,were introduced to explain these trends.Furthermore,the linear trend observed in Arrhenius plots of diffusivities supports the diffusivity results.Additionally,good agreement between the diffusivities of alumina in one silicate slag obtained via CLSM and rotating finger test investigations verified the reliability of the results.

Effects of Different Raw Materials and Additions on Wave Transparency of Alumina Fiber Products

Fiber products for microwave kilns were prepared using alumina fibers with alumina contents of 72 mass%and 80 mass%,and calcined alumina powder(4-6μm)as the main raw materials,silica sol as the binder,and cationic starch as the flocculant.Effects of different raw materials and their additions on the wave transparency of fiber products were researched.The results show that as the alumina fiber(72%)addition increases,the heating rate of the samples first decreases and then increases,and the corresponding wave transparency of the sample first increases and then decreases.When the alumina fibers addition is 40 mass%and the alumina powder addition is 30 mass%,the prepared microwave kiln lining material has a higher mullite content,which improves the wave transparency of the sample.The sample prepared from alumina fibers with an alumina content of 80%has a suitable glass-mullite phase ratio,performs lower overall dielectric constant and good wave transparency,and is a suitable lining material for microwave kilns.

Aluminum and Activated Alumina Powder Additions on Microwave Synthesis of Al_(4)SiC_(4)

Aiming at improving the properties of magnesia carbon materials,silicon aluminum carbide(Al_(4)SiC_(4))containing materials were prepared using industrial aluminum powder,silicon carbide powder,and graphite as raw materials,and activated alumina powder as an additive,mixing thoroughly,pressing into cylinders and then firing at 1200℃for 30 min in a carbon embedded atmosphere by the microwave method.The effects of the aluminum powder addition(20%and 24%,by mass)and activated alumina powder addition(0,3%,5%and 7%,by mass)on the microwave synthesis of Al_(4)SiC_(4) as well as the effect of the obtained Al_(4)SiC_(4) containing material on the properties of magnesia carbon bricks were studied.The results show that:compared with the samples with 20%aluminum powder,those with 24%aluminum powder generate more Al_(4)SiC_(4).With the activated alumina powder addition increasing from 0 to 7%,the amount of Al_(4)SiC_(4) generated increases first and then decreases.Compared with the sample without activated alumina powder,the samples with activated alumina powder show lower bulk density and higher apparent porosity.With the activated alumina powder addition increasing from 3%to 7%,the bulk density of the samples increases first and then decreases,while the apparent porosity of the samples shows an opposite trend.The optimal additions are 24%aluminum powder and 5%activated alumina powder,and Al_(4)SiC_(4) synthesized in this sample has a hexagonal plate structure.With the synthesized Al_(4)SiC_(4) containing material added,the magnesia carbon brick has slightly increased cold modulus of rupture,basically the same modulus of elasticity and improved oxidation resistance.

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.

载铁活性氧化铝催化臭氧氧化处理废水COD的工艺研究

为了提高臭氧催化氧化技术对工业废水中有机污染物的去除效率,采用浸渍法,将铁负载于活性氧化铝上。当硝酸铁浓度为0.8 mol/L、臭氧量为5 g/h时,载铁活性氧化铝催化臭氧氧化工业废水有机污染物的去除率最大,约为56%。相比单独使用吸附和臭氧催化氧化技术,它大大提高了废水有机污染物的去除效果。因此载铁活性氧化铝催化臭氧氧化可作为高浓度工业废水去除有机污染物的一种有效方法。

纳米氧化铝改性地面井固井水泥水化机制研究

随着地面井固井技术发展加快,工程现场对于地面井固井水泥浆的早期流动性及凝结性能有了更高的要求。为了提高固井工程注水泥作业的顶替效率,改善固井工程现场作业应用情况,提出了纳米氧化铝颗粒改性固井水泥的方法,利用核磁共振技术对质量分数为0、0.05%、0.10%、0.15%及0.20%的纳米氧化铝改性水泥浆(水灰比为0.44)在不同水化龄期的水化反应变化特征进行了研究,探究了纳米氧化铝改性水泥的水相分布、物理结合水总信号量变化、峰形指数及迁移速率。结果表明:纳米氧化铝改性水泥浆在水化阶段的T2图谱会出现3个弛豫峰,分别对应絮凝结构填充水(0.1~10 ms)、毛细水(10 ms)、自由水(800~1000 ms);其物理结合水总信号随纳米氧化铝质量分数增加而逐步减少,其中质量分数为0.20%的纳米氧化铝改性水泥浆信号量减少速率最快;峰形指数呈现先上升后下降的趋势,当水化反应进行至600 min时,质量分数为0.20%的改性水泥浆变化速率最快,弛豫峰向短弛豫方向移动速率加快;结合迁移速率将纳米氧化铝改性固井水泥水化反应阶段划分,其水化机制分别作用在4个水化时期:①初始水化期(5~60 min),水化速率未发生明显改变;②加速水化期(60~600 min),纳米氧化铝使水泥浆中物理结合水转化为化学结合水所经历时间变短,水化进程加快,达到促进水泥水化的效果;③稳定水化期(600~1200 min),水泥体系趋于稳定;④延缓水化期(1200~1800 min),物理结合水转化为化学结合水速率变慢,水泥水化进程减慢。研究结论得到,纳米氧化铝改性水泥浆水化时期可以划分为4个阶段,分别起到物理填充、加速、稳定、延缓的作用。在加速期,纳米氧化铝促进水泥的早期流动,有利于水泥浆的泵送及流动,在延缓期,纳米氧化铝延缓水泥的进一步水化进程,利于发展早期强度。其中,质量分数为0.20%的纳米氧化铝改性水泥浆对于水泥水化进程影响最大,促进填充水向结合水的转化,在加速水化期间对于水泥浆水化反应加速程度最大,以此作为依据对现场固井水泥的制备及应用提供指导。

铝粉还原污酸中砷新工艺研究

由于硫化精矿中砷含量越来越高,致使烟气处理过程产生的污酸中砷含量也越来越高,同时污酸中含有铜、铁等有价金属。目前污酸除砷方法多以除砷为目的,形成的含砷渣属于危废,还需要二次处理。本研究研发了还原除砷新工艺,首先向污酸中加入硫化砷渣进行脱铜预处理并回收铜,然后用铝粉还原脱铜后液中的砷回收砷,最后向脱砷液中加入硫酸钾回收铝,还原后液回收还原剂后采用两段中和法处理。试验研究结果表明,在加入铜离子摩尔量1.1倍的硫化砷渣、反应温度85℃、反应时间3 h的条件下,污酸中的铜含量由2000 mg/L降至196 mg/L,硫化铜渣返熔炼配料系统;在还原温度70℃、还原时间2 h,还原剂用量1.8倍的条件下,砷的还原率大于96%,还原后液中的砷含量低于300 mg/L,得到的砷渣品位大于95%,可用于后续制备高品位单质砷;在硫酸钾用量1.1倍、反应温度常温、反应时间2 h的条件下,溶液含铝3.6 g/L,得到的明矾可达到《工业硫酸铝钾》(HG/T2565—2007)一等品标准。该方法除砷效果好,且能将污酸中的砷转变为具有经济价值的砷产品,还不会产生硫化氢气体,具有应用推广价值。

氧化铝填料对绝缘涂层导热性能的影响

以高模数硅酸钾溶液为基料,氧化铝为导热绝缘填料,加入硅丙乳液、消泡剂,制备有机无机复合硅酸盐导热绝缘涂层。通过测试硅酸盐涂层的导热系数、体积电阻率、孔隙率、孔径分布和元素分布变化,研究绝缘硅酸盐涂层导热性能。结果表明,适当提高氧化铝的质量分数,硅酸盐绝缘涂层的导热性能提升。氧化铝填料球形形貌和大粒径更有利硅酸盐绝缘涂层的导热性能提升。当填料为粒径2.9μm的球形氧化铝,且质量分数在37.5%时,涂层的导热系数最高达1.072 W/(m·K),体积电阻率大于10^(8)Ω·m,此时涂层的导热绝缘性能达到最佳。

氧化硼对Al_(2)O_(3)-SiC-C质浇注料力学性能的影响

为了利用氧化硼“间接烧结”特性,进一步提升Al_(2)O_(3)-SiC-C质浇注料的力学性能,以氧化硼(≤0.075 mm)为助烧剂,制备了以FM60莫来石颗粒、致密刚玉、碳化硅、α-Al_(2)O_(3)微粉等为主要原料的浇注料,探究了氧化硼细粉加入量(加入质量分数分别为0、0.2%、0.4%和0.6%)对Al_(2)O_(3)-SiC-C质浇注料结构与性能的影响。结果表明,添加氧化硼细粉会显著提升浇注料的加水量,但其有利于晶须状莫来石的生成,从而加强骨料和基质间的结合强度,试样的力学性能得到明显提升。但当氧化硼细粉加入量提高至0.6%(w)时,试样中莫来石晶须长径比减小,试样的强度降低。综合以上结果,氧化硼最佳加入量为0.4%(w)。

SLA打印制备融合TPMS氧化铝陶瓷支架结构优化设计研究

三周期最小表面(TPMS)结构具有优异的力学性能与生物医学性能,设计制造合适的TPMS骨支架结构能为骨修复、骨替代、骨愈合的临床治疗提供可能。本文基于人体骨组织结构参数分别设计了以P、G、D三种类型为主的TPMS支架及其不同融合系数K值影响下的融合TPMS支架,采用紫外立体光刻技术(SLA)打印制备了陶瓷生坯,通过脱脂与烧结后处理获得了成型氧化铝陶瓷支架,并对支架模型与成型陶瓷试样分别进行了有限元仿真与实验测试。结果表明:1)陶瓷支架具有相对光滑的表面与较高的成型精度,其整体形态与设计模型基本一致,侧面比顶面稍显粗糙。2)与单类型结构相比,融合TPMS结构支架表现出较好的抗压强度与应力分布。其中,当融合系数K=4时,P与G结构融合支架支架的力学性能最优,抗压强度为71.72 MPa,最大应力与平均应力分别为141.90和13.214 MPa;3)融合结构的渗透性均弱于单类型结构,且不同融合系数K值的结构支架渗透性也不同,结合数值模拟与实验数据,当融合系数K=1、2时,P与G结构、P与D结构融合支架渗透性表现较好。综上,当融合系数K=1时,P与G结构融合支架同时具备较优的力学性能和渗透性,适合作为人体骨支架结构类型。

草状氧化铝微结构渐变折射率的计算及实验研究

针对草状氧化铝的微纳结构对折射率的影响,采用台体计算法与柱体计算法计算氧化铝的体积,使用Clausius-Mossotti方程式与MATLAB软件拟合计算微纳结构的折射率变化,使用TFC软件进行拟合,最终计算出草状氧化铝的渐变折射率,研究其微结构的形貌特征及渐变折射率的分布,计算其可见光减反射性能。采用电子束沉积氧化铝薄膜,通过对沉积温度、水煮工艺等参数的优化,获得了不同结构的草状氧化铝纳米薄膜,制备了可见光波段420~680 nm的减反射薄膜。

电子束设备蒸镀铝膜工艺的研究

利用电子束蒸镀设备沉积高质量铝膜是薄膜工艺的一个难题。为此,提出一种采用改造的三氧化二铝坩埚作为蒸镀铝膜的衬锅,通过三次添加物料预熔再蒸镀来沉积铝膜的方法,研究了不同蒸镀速度对铝膜电阻率、晶粒形貌和成分组成的影响。结果表明:凸起状的熔融铝液面能有效增大其与坩埚壁的接触角,基本消除铝膜中的三氧化二铝杂质;随着蒸镀速度的增加,铝膜晶粒尺寸逐渐增大,而平均电阻率呈下降趋势;采用本方法能够制备出纯度99.9%,电阻率最低为3.4×10^(-6)Ω·cm的铝膜。

铝灰碱法烧结熟料溶出过程及超声协同作用研究

二次铝灰碱法烧结熟料溶出过程是回收氧化铝的重要环节,当溶出过程关键参数控制不当,会造成氧化铝溶出率低、能耗较高。为了提高氧化铝溶出率,了解氧化铝溶出机制,降低溶出过程能耗,探究了二次铝灰碱法焙烧熟料常压溶出过程中温度、时间、液固比与熟料中氧化铝溶出率的关系及熟料中NaAlO_(2)溶出过程动力学,考察了施加超声对氧化铝溶出率的影响。结果表明:熟料溶出过程优化参数为溶出温度为80℃、溶出时间为15 min、液固比(体积质量比,mL/g)为15,氧化铝溶出率可达92.3%;溶出动力学表明,NaAlO_(2)溶出过程受内扩散控制,表观活化能为13.45 kJ/mol;发现施加超声可在相同氧化铝溶出率下降低溶出温度至70℃并缩短溶出时间至9 min。该研究结果可为二次铝灰碱性焙烧熟料溶出过程降低能耗和提高效率提供新的理论参考和基础数据。