Electrical conductivity of （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts

The effects of contents of AlF3 and Al2O3, and temperature on electrical conductivity of （Na3AlF6-40%K3AlF6）- AlF3-Al2O3 were studied by continuously varying cell censtant （CVCC） technique. The results show that the conductivities of melts increase with the increase of temperature, but by different extents. Every increasing 10 ℃ results in an increase of 1.85 × 10^-2, 1.86× 10^-2, 1.89 × 10^-2 and 2.20 × 10^-2 S/cm in conductivity for the （Na3AlF6-40%K3AlF6）-AlF3 melts containing 0%, 20%, 24%, and 30% AlF3, respectively. An increase of every 10 ℃ in temperature results an increase about 1.89× 10^-2, 1.94 × 10^-2, 1.95 × 10^-2, 1.99× 10^-2 and 2.10× 10^-2 S/cm for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts containing 0%, 1%, 2%, 3% and 4% Al2O3, respectively. The activation energy of conductance was calculated based on Arrhenius equation. Every increasing 1% of AlF3 results in a decrease of 0.019 and 0.020 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3 melts at 900 and 1 000 ℃, respectively. Every increase of 1% Al2O3 results in a decrease of 0.07 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts. The activation energy of conductance increases with the increase in content of AlF3 and Al2O3.     

Effect of TiB2 content on resistance to sodium penetration of TiB2／C cathode composites for aluminium electrolysis

TiB2/C cathode composites with various contents of TiB2 were prepared and their characterizations were observed and compared. The expansion of samples due to sodium and bath penetration was tested with a modified laboratory Rapoport apparatus and the appearances of the cut sections of specimens after electrolysis were studied.The results show that the mass of TiB2/C cathode composites with mass fraction of TiB2 less than 70% appreciably increases, but that of the composites with mass fraction of TiB2 more than 70% decreases slightly after being baked.The resistance to sodium and bath penetration of TiB2/C cathode composites increases with the increase of TiB2 content, especially in the composites with high TiB2 content. TiB2/C cathode composites have high resistance to the penetration of sodium and bath as well as good wettability by molten aluminum, and keep integrality and have little change of appearance after electrolysis, which indicates that TiB2/C cathode composites can be used as inert wettable cathode for aluminum electrolysis.     

铝电池的开发与应用进展

铝元素在地壳中的储量丰富,来源广泛,并且金属铝的安全性高,在离子电池领域中具有广阔的应用前景.尽管铝金属在离子电池中具有如此诱人的优势,但铝离子电池的能量密度、稳定性以及所使用的电解液安全性和成本依然制约其发展.对铝离子电池的最新工作进行梳理、分析和总结,并进一步探讨其作为新型储能体系的机遇和挑战.主要从正极材料、电解液及铝金属负极3个方面对近期的铝离子电池相关工作进行了总结,为开展高能量密度、高稳定性铝离子电池的研究奠定基础.

     

Effect of baking processes on properties of TiB2/C composite cathode material

Pitch and TiB₂/C green composite cathode material were respectively analyzed with simultaneous DSC-TGA, and effects of three baking processes of TiB₂/C composite cathode material, i.e. K25, K5 and M5, on properties of TiB₂/C composite cathode material were investigated. The results show that thermogravimetric behavior of pitch and TiB₂/C green composite cathode is similar, and appears the largest mass loss rate in the temperature range from 200 to 600°C. The bulk density variation of sample K5 before and after baking is the largest (11.9%), that of sample K25 is the second, and that of sample M5 is the smallest (6.7%). The crushing strength of sample M5 is the biggest (51.2 MPa), that of sample K25 is the next, and that of sample K5 is the smallest (32.8 MPa). But, the orders of the electrical resistivity and electrolysis expansion of samples are just opposite with the order of crushing strength. The heating rate has a great impact on the microstructure of sample. The faster the heating rate is, the bigger the pore size and porosity of sample are. Compared with the heating rate between 200 and 600° of samples K25 and K5, that of sample M5 is slower and suitable for baking process of TiB₂/C composite cathode material. Foundation item: Project (2005CB623703) supported by the Major State Basic Research and Development Program of China; Project (2008AA030502) supported by the National High-Tech Research and Development Program of China     

Effect of electrolysis superheat degree on anticorrosion performance of 5 Cu/（10NiO-NiFe2O4） cermet inert anode

5Cu/(10NiO-NiFe2O4) cermet inert anodes were prepared by cold-pressing and sintering process, and the effect of superheat degree of melting K3AlF6-Na3AlF6-AlF3 on their anticorrosion performance was studied under electrolysis conditions. The results show that, the fluctuation of cell becomes small with increasing of superheat degree, which is helpful to inhibit the formation of cathodic encrustation; the concentration of impurities from inert anode in bath goes up to certain degree, but it is far smaller than those in traditional high-temperature bath. Increasing the superheat degree of melting K3AlF6-Na3AlF6-AlF3 has unconspicuous effect on the contents of impurities in cathodic aluminum. The total mass fractions of Fe, Ni and Cu in aluminum are 15.38% and 15.09% respectively under superheat degree of 95 and 195 ℃. From micro-topography of anode used view, increasing the superheat degree can aggravate corrosion of metal Cu in inert anode, and has negative influence on electrical conductivity of electrode to some extent.     

Structure of Bi2O3-ZnO-B2O3 system low-melting sealing glass

Bi_2O_3-ZnO-B_2O_3 system glass is a kind of lead-free low melting sealing glasses. The structure of Bi_2O_3-ZnO-B_2O_3 system low-melting sealing glass was investigated by DSC, FT-IR, XRD and SEM. The results show that with the increase of B_2O_3 content, the transition temperature Tg and softening temperature T_f of Bi_2O_3-ZnO-B_2O_3 system low-melting sealing glasses increase, which leads to the liquid phase precipitation temperature increasing and promotes the structure stability in the glass. With increasing the heat treatment temperature, a large number of liquid phases appear in samples and the sinter efficiency of the samples increases. The FT-IR spectra of the glasses show the presence of some bands that are assigned to vibrations of Bi-O bond from [BO_3] pyramidal and [BiO_6] octahedral units and B-O from [BO_3] and [BO_4] units. With the decrease of B_2O_3 content, the crystallization tendency of the glass increases. In glass samples B_1 and B_2, crystallization starts at 460 ℃ and 540 ℃, respectively. Both of them precipitate Bi-(24)B_2O_(39) phases.     

Vaporization behavior of lead from the FeO-CaO-SiO2-Al2O3 slag system

Vaporization behavior (1163–1463 K) of lead in the slag system of FeO-CaO-SiO₂-Al₂O₃ with CaCl₂ was examined. A thermodynamic estimation with the principle of Gibbs free energy minimization showed that the major vapor species from the sample of the FeO-CaO-SiO₂-Al₂O₃ system+PbO+CaCl₂ were metallic Pb, PbCl, PbCl₂, and FeCl₂, at the experimental temperature range. The experimental results show that the mole ratio of vaporized Cl in lead chlorides to vaporized Pb, simply expressed as Cl/Pb, decreases with increasing temperature. The larger Cl/Pb means a larger ratio of gaseous PbCl₂, since metallic Pb and PbCl vapors are formed in a similar reduction atmosphere. The evaporation is initially rapid and becomes steady after holding for 10 min. Gaseous PbCl₂ is mainly formed during the heating period, and at the holding stage, it reacts with FeO to produce gaseous FeCl₂. With regard to slag composition, FeO content and basicity significantly affect the evaporation of lead. High FeO content and high basicity promotes the formation of metallic Pb and PbCl, whereas, it prohibits PbCl₂ evaporation.     

锂离子电池负极材料 Na2Li2Ti6O14的嵌脱锂过程动力学研究

为了研究钛酸钠锂(Na2Li2Ti6O14)负极材料嵌脱锂的动力学行为,用溶胶-凝胶法合成 Na2Li2Ti6O14负极材料,采用 X 射线衍射法(XRD)和电子显微镜(SEM)分别对材料进行物相分析和微观形貌的观察.采用恒流充放电测试、循环伏安法(CV)和恒电流间歇滴定法(GITT)研究了 Na2Li2Ti6O14的电化学性能和嵌脱锂过程动力学.研究结果表明,制备的 Na2Li2Ti6O14材料纯度高,结晶度良好,循环稳定性好;由不同扫描速率的循环伏安法测出的 Na2Li2Ti6O14中锂离子在氧化、还原峰对应的化学扩散系数 Da和 Dc分别为7.3×10-11和7.8×10-11cm2/s;由恒电流间歇滴定技术测得的锂离子在 Na2Li2Ti6O14电极中的扩散系数为10-11~10-8cm2/s.     

Reaction dynamics in the combustion synthesis system of Al-CrO3-Al2O3-NaF-N2-O2

A new material with heat-resistant and adiabatic characteristics and high strength was prepared using the combustion synthesis method by mixed powders of CrO3, Al, Al2O3, and NaF in atmospheric gas. The reaction dynamic process of the Al-CrO3-NaF-Al2O3-N2-O2 new material system by the combustion synthesis method was discussed based on the observation results by SEM, EDS, and XRD in combination with the combustion front quenching method （CFQM） and the relation curves between reaction free enthalpies and the corresponding temperatures. The combustion synthesis mechanism and the formation reasons of the phase in the combustion product were analyzed.     

Electrical resistivity of TiB2/C composite cathode coating for aluminum electrolysis

1INTRODUCTIONThere are many disadvantages in the presentHall-Heroult electrolytic process[1],such as highenergy consumption,low unit productivity and se-rious environmental pollution and so on,especiallythe high energy consumption of per ton alumin-ium,which ranges from13MW·h to15MW·h,and the energy efficiency is less than50%[2].Therefore,low-energy consumption aluminumre-duction cell has been a research focus for interna-tional aluminum companies and institutes.Thedrained cathode cel…     

K2Ti2O5对汽车尾气中碳烟的催化氧化性能研究

通过溶胶凝胶法制备了K2Ti2O5催化剂,并利用XRD,SEM,BET等方法进行了表征。利用程序升温反应对K2Ti2O5的碳烟催化氧化性能进行了研究。结果表明,K2Ti2O5具有一定的碳烟催化氧化活性。同时,一定量的NOx有助于K2Ti2O5的催化氧化活性,说明K2Ti2O5是一种潜在的可同时去除NOx和碳烟的新型催化剂。由于K2Ti2O5对碳烟具有较高的催化氧化活性、较好的抗水性和低廉的价格,因此是一种具有较好发展前景的汽车尾气净化催化剂。     

Effects of heat treatment temperature on crystallization and thermal expansion coefficient of Li2O-Al2O3-SiO2

The basic glass of Li₂O-Al₂O₃-SiO₂ system using P₂O₅ as nucleator was prepared by means of conventional melt quenching technology, and the heat-treatment process was determined by using differential thermal analysis. The crystalline phases and the microstructure of the glass-ceramics were investigated by using X-ray diffraction and scanning electron microscopy. The results show that the glass based on Li₂O-Al₂O₃-SiO₂ oxides using P₂O₅ as nucleator can be prepared at lower melt temperature of 1450°C and the glass-ceramics with lower thermal expansion coefficient of 21.6 × 10⁻⁷°C⁻¹ can also be obtained at 750°C. The glass-ceramics contain a few crystal phases in which the main crystal phase is β-quartz solid solution and the second crystal phase is β-spodumene solid solution. When the heat treatment temperature is not higher than 650°C, the transparent glass-ceramics containing β-quartz solid solution can be prepared. β-quartz solid solution changes into β-spodumene solid solution at about 750°C. And the appearance of the glass-ceramics changes from translucent, part opaque to complete opaque with increasing temperature.     

Densification and sintering dynamics of 10NiO-NiFe2O4 composites doped with CaO

The effects of CaO content in the range from 0 to 4.0%, and sintering temperature on the phase composition, relative density and electrical conductivity of 10NiO-NiFe2O4 composites doped with CaO were studied. The results show that there is no change of structure for NiO or NiFe2O4; there is apparent oxygen absorbing and releasing behavior during the heating process in air for 10NiO-NiFe2O4 composites. Introduction of CaO can accelerate the densification of 10NiO-NiFe2O4 composites. The maximum value of relative density is 98.75% for composite doped with 2.0% CaO and sintered at 1 200 ℃, which is beyond about 20% for the undoped composites. The sintering activated energy of sample containing 2% CaO decreases by 15.87 kJ/mol, compared with that of the undoped sample.     

Structure and mechanical properties of ZrO2-mullite nano-ceramics in SiO2-Al2O3-ZrO2 system

ZrO2-mullite nano-ceramics were fabricated by in-situ controlled crystallizing from SiO2-Al2O3-ZrO2 amorphous bulk. The thermal transformation sequences of the SiO2-Al2O3-ZrO2 amorphous bulk were investigated by X-ray diffraction, infrared spectrum, scanning electron microscope and differential scanning calorimetric. And the mechanical properties of the nano-ceramics were studied. The results show that the bulks are still in amorphous state at 900 ℃ and the t-ZrO2 forms at about 950 ℃ with a faint spinel-like phase which changes into mullite on further heating. ZrO2 and mullite become major phases at 1 100 ℃ and an amount of m-ZrO2 occur at the same time. The sample heated at 950 ℃ for 2 h and then at 1 100 ℃ for 1 h shows very dense and homogenous microstructure with ball-like grains in size of 20-50 nm. With the increase of crystallization temperature up to 1 350 ℃, the grains grow quickly and some grow into lath-shaped grains with major diameter of 5 μm. After two-step treatment the highest micro-hardness, flexural strength and fracture toughness of the samples are 13.72 GPa, 520 MPa and 5.13 MPa·m1/2, respectively.     

Hot Deformation Behavior of Mg2[KG-*2]B2[KG-*2]O5 Whiskers Reinforced Al Composite

The hot deformation behavior of Mg2B2O5w/Al composite was investigated by compression test at different temperatures and different strain rates. The constitutive equation was established by taking peak stresses as the function of temperatures and strain rates. It was found that the hyperbolic sine law creep equation is in good agreement with the experimental results and can be applied to all flow stresses under various deformation conditions. The apparent activation energy of the composite is 138. 64 kJ /mol, which is approximately equal to that of lattice self-diffusion of pure Al.     

固体酸SO42-／TiO2-La2O3催化合成乙酸正丁酯

采用低温（-15℃）陈化法制备SO42-/TiO2-La2O3稀土掺杂固体酸（STL）,用于催化合成乙酸正丁酯,研究醇酸摩尔比、反应时间、催化剂用量等因素对酯化率的影响。结果表明：当n（正丁醇）：n（乙酸）=1．5：L,反应时间为2h,催化剂用量占反应物总质量的1．4％时,乙酸正丁酯的酯化率可达99．5％。     

CCTO掺杂对BaTiO3-Nb2O5-Co3O4陶瓷系统介电性能的影响

以BaTiO3-Nb2O5-Co3O4(BTNC)系统陶瓷为研究对象,研究了掺杂CaCu3Ti4O12(CCTO)对该系统陶瓷介电性能的影响.结果表明,在20～85℃温度范围内,BT系统中CC-TO掺杂量为3.0%时,体系平均介电常数>2 600,温度稳定性△C/C≤4.7%;在20～125℃温度范围内,BTNC系统中CCTO掺杂量为2.0%时,体系的平均介电常数>2 700,温度稳定性△C/C≤10%;CCTO掺杂量为4.0%时,平均介电常数>2 200,温度稳定性△C/C≤4.7%.     

Fe3O4@MSCe/H2O2多相芬顿体系的分解性能及放热规律研究

以5～8 mm粒径半焦为载体,制备了半焦负载Fe_3O_4复合材料(Fe_3O_4@MSCe),采用SEM、XPS、XRD和FTIR对样品的物化性质和价键结构进行了表征,并研究了Fe_3O_4@MSCe/H_2O_2多相Fenton体系的分解性能和放热规律.结果表明:Fe_3O_4@MSCe保留了半焦的多孔形态,Fe_3O_4均匀且牢固地负载于半焦颗粒表面;在pH=7.8～11.2碱性条件下,均保持了较好的分解活性;在[H_2O_2]=0.25 mol/L、Fe_3O_4@MSCe投加量为533g·L~(-1)、pH=7.8、T_0=30℃反应条件下,300 mL浓度为0.04 mol·L~(-1)的邻苯二胺溶液的分解率为90.9%,溶液温度升高数值为7.1℃,表现出较好的分解性能和放热特性,为解决现有芬顿技术存在的问题和污水处理的能源化利用提供了技术支撑.     

Effect of metallic content on mechanical property of Ni/（10NiO-NiFe2O4 ） cermets

1 INTRODUCTIONThe use of inert or non-consumable anodes forreplacement of consumable carbon anodes in Hall-H啨roult electrolysis cells for the production of alu-minum has been a technical and commercial goalfor many decades .In the present process ,consumable carbon an-odes are used,andthe anode product is CO2. Withaninert anode ,the cell reaction will be :Al2O3=2Al +23O2(1)The basic requirements for aninert anode are :1) to exhibit a lowcorrosion rate in the high tem-perature melts an…