Thermodynamics on formation of C, Al_4C_3 and Al_2O_3 in AlCl disproportionation process in vacuum to produce aluminum

The formation conditions of C, Al4C3 and Al2O3 in the Al Cl disproportionation process in vacuum to produce aluminum was investigated by thermodynamics analysis. It is demonstrated that the required temperatures for the reactions to form these impurities, the disproportionation of CO and the reactions of metallic aluminum with CO, decrease with decreasing pressure. The lg pCO-1/T diagram of metallic aluminum-CO system agrees with the experimental results, indicating that the reaction rate is very high and this system in vacuum is approximately in equilibrium; therefore, the equilibrium diagram can be used to predict the possible reactions in this system in vacuum.

Vacuum Ultraviolet Excited Photoluminescence Properties of Y_2O_2S:Eu^(3+),Bi^(3+) Phosphor

As an Hg-free lamp using phosphor, the Bi^3＋ and EH^3＋ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet（VUV） excitation were investigated. The VUV photoluminescent intensity of Y2O2S：Eu^3＋ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S：Eu^3＋,Bi^3＋ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S：Eu^3＋,Bi^3＋ at 147 nm is mainly because the Bi^3＋ acts as a medium and effectively performs the energy transfer process： Y^3＋-O^2-→Bi^3＋→Eu^3＋, while the intense emission band at 172 nm is attributed to the absorption of the characteristic ^1So-^1P1 transition of Bi^3＋ and the direct energy transfer from Bi^3＋ to Eu^3＋. The Y2O2S：Eu^3＋,Bi^3＋ shows excellent VUV optical properties compared with the commercial （Y,Gd）BO3：Eu^3＋. Thus, the Y2O2S：Eu^3＋,Bi^3＋ can be a potential red VUV-excited candidate applied in Hg-free lamps for backlight of liquid crystal display.

Synthesis and Tribological Behaviors of Ti_3SiC_2 Material Prepared by Vacuum Sintering Technique

The bulk Ti3SiC2 specimens with less than 1 wt% TiC impurity were prepared by vacuum sintering technique, and the average grain size was about 5-6 μm in the elongated direction. When the sintering temperature, soaking time and heating rate were 1 400 ℃, 1 h and 10℃·min-1, respectively, the highest relative density of Ti3SiC2 specimens could reach 97.8%. Meanwhile, the lowest coefficient of friction （COF） and wear rate （WR） of the Ti3SiC2 samples were 0.55 and 1.37×10-3 mm3（Nm）-1 at a sliding speed of 0.35 m/s, load pressure of 10 N and ambient condition, respectively. The COF of the Ti3SiC2 sample reduced with the increasing of the load pressure, while the WRs fluctuated little. The WR increased with the increasing of the sliding speed, and weakly influenced the COF. These changing behaviors could be attributed to the presence and coverage of the amorphous mixture oxide film ofTi, Si, A1, and Fe on the Ti3SiC2 friction surface. The self- antifriction mechanism led to reducing of the COF. The increasing of the WR was attributed to the wearing consumption.

Temperature-Dependent Emission of Pr^(3+)-Doped LaB_3O_6 under Vacuum Ultraviolet Excitation

The vacuum ultraviolet （VUV） luminescent properties of Pr^3＋ -activated LaB3O6 were investigated with highenergetic synchrotron radiation from 20 to 300 K. In the emission spectra, the parity-forbidden 4f^2→4f^2 and parity-allowed 4f5d→4f^2 transitions were observed simultaneously. In addition, it was also observed that the intensity of 4f5d→4f^2 emission bands increased relative to the intensity of 4f^2→4f^2 emissions with increasing temperature. The thermal equilibrium model of energy levels was employed with respect to the lowest 4f5d state and ^1S0 state of LaB3O6：Pr^3＋ , as a result of which the fitted curve had a good agreement with the experiment values, which clarified the physical nature of temperature-dependent emission characteristics of Pr^3＋ in LaB3O6.

Vacuum ultraviolet excited photoluminescence properties of Gd_2O_2CO_3:Eu^(3+) phosphor

The Gd2O2CO3：Eu^3＋ with type-Ⅱ structure phosphor was successfully synthesized via flux method at 400 ℃ and their photoluminescence properties in vacuum ultraviolet （VUV） region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO3^2- host absorption and charge transfer （CT） of Gd^3＋-O2^- were observed for Gd2O2CO3：Eu^3＋. Under 172 nm excitation, Gd2O2CO3：Eu^3＋ exhibited strong red emission with good color purity, indicating Eu^3＋ ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3：Eu^3＋ was （x=0.652, y=0.345）. The photoluminescence quenching concentration of Eu^3＋ excited by 172 nm for Gd2O2CO3：Eu^3＋ was about 5%. Gd2O2CO3：Eu^3＋ would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.

Vacuum relaxation and annealing-induced enhancement of mobility of regioregular poly(3-hexylthiophene) field-effect transistors

In order to enhance the performance of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）, RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and annealing. This paper reports that the crystal structure, the molecule interconnection, the surface morphology, and the charge carrier mobility of RR-P3HT films are affected by vacuum relaxation and annealing. The results reveal that the field-effect mobility of RR-P3HT FETs can reach 4.17×10^-2m^2/（V·s） by vacuum relaxation at room temperature due to an enhanced local self-organization. Furthermore, it reports that an appropriate annealing temperature can facilitate the crystal structure, the orientation and the interconnection of polymer molecules. These results show that the field-effect mobility of device annealed at 150 ℃ for 10 minutes in vacuum at atmosphere and followed by placement for 20 hours in vacuum at room temperature is enhanced dramatically to 9.00×10^-2m^2/（V·s）.

Tribological performances of Si_3N_4 ceramic in vacuum

The tribologieal performances between Si3N4 ceramic balls and GCr15 steel disks without lubrication both in air and in vacuum （6 × 10^-3Pa） are investigated. The results show that the friction coefficient and wear in vacuum are smaller than those in air. The friction mainly occurs between steel and steel in air because the steel is obvious to adhere on the ceramic surface. The ceramic and steel are hard to adhere in vacuum. The function of mechanical plough and the rotation of small wear particles in the contact region reduce the friction and wear between the ceramic and steel in vacuum.

亚微米球形Y_(2)O_(3)粉体及其透明陶瓷的制备

Y_(2)O_(3)以其优良的物理化学性质和在280 nm~8μm宽频段内的高透明性,而广泛应用于激光介质或光学窗口等领域。制备高透明的Y_(2)O_(3)陶瓷是目前的研究热点和难点,而高质量的粉体是制备高透明Y_(2)O_(3)陶瓷的关键,尿素均相沉淀法以其爆发成核和均匀可控的阴离子释放机制成为制备单分散颗粒的主要方法。本工作以硝酸钇和尿素为原料,采用尿素均相沉淀法制备了单分散、亚微米级的球形Y_(2)O_(3)粉体。采用不同方法研究了Y_(2)O_(3)前驱体和煅烧后粉体的结构、物相演变和形貌。前驱体的颗粒尺寸约为330 nm,800℃煅烧2 h得到的Y_(2)O_(3)粉体尺寸约为260 nm。在800℃煅烧后即可得到纯相的Y_(2)O_(3)粉体,粉体呈球形,分散性好,且粒径均匀。以该Y_(2)O_(3)粉体为原料,添加原子分数0.3%的Nb_(2)O_(5)为烧结助剂,在1780℃通过真空无压烧结成功制备了透明Y_(2)O_(3)陶瓷。材料的光学性质优良,即样品(厚度1 mm)的直线透过率在1100 nm处达到76.9%,在400 nm处达到65.6%。本工作为制备性能优良的Y_(2)O_(3)透明陶瓷提供了一种新的方法。

Optical and electrical properties of BaSnO_(3) and In_2O_(3) mixed transparent conductive films deposited by filtered cathodic vacuum arc technique at room temperature

For the crystalline temperature of BaSnO_(3)(BTO)was above 650℃,the transparent conductive BTO-based films were always deposited above this temperature on epitaxy substrates by pulsed laser deposition or molecular beam epitaxy till now which limited there application in low temperature device process.In the article,the microstructure,optical and electrical of BTO and In_(2)O_(3) mixed transparent conductive BaInSnO_(x)(BITO)film deposited by filtered cathodic vacuum arc technique(FCVA)on glass substrate at room temperature were firstly reported.The BITO film with thickness of 300 nm had mainly In_(2)O_(3) polycrystalline phase,and minor polycrystalline BTO phase with(001),(011),(111),(002),(222)crystal faces which were first deposited at room temperature on amorphous glass.The transmittance was 70%–80%in the visible light region with linear refractive index of 1.94 and extinction coefficient of 0.004 at 550-nm wavelength.The basic optical properties included the real and imaginary parts,high frequency dielectric constants,the absorption coefficient,the Urbach energy,the indirect and direct band gaps,the oscillator and dispersion energies,the static refractive index and dielectric constant,the average oscillator wavelength,oscillator length strength,the linear and the third-order nonlinear optical susceptibilities,and the nonlinear refractive index were all calculated.The film was the n-type conductor with sheet resistance of 704.7Ω/□,resistivity of 0.02Ω⋅cm,mobility of 18.9 cm2/V⋅s,and carrier electron concentration of 1.6×10^(19) cm^(−3) at room temperature.The results suggested that the BITO film deposited by FCVA had potential application in transparent conductive films-based low temperature device process.

m(ZnO)/m(B_(2)O_(3))质量比对低熔点封接玻璃Bi_(2)O_(3)-B_(2)O_(3)-ZnO结构、性能与润湿性的影响

针对真空玻璃封接的性能要求,本文采用高温熔融法制备了一种针对真空玻璃封接的铋系非晶无铅玻璃粉,通过高温X射线衍射、粉末X射线衍射、拉曼光谱、差式扫描量热仪、热膨胀测试和扫描电子显微镜等测试方法,研究了m(ZnO)/m(B_(2)O_(3))质量比对Bi_(2)O_(3)-B_(2)O_(3)-ZnO玻璃的网络结构、特征温度、热膨胀系数和封接温度的影响。结果表明,增加m(ZnO)/m(B_(2)O_(3))质量比可促进锌氧多面体由[ZnO_(4)]向[ZnO_(6)]转变,导致热膨胀系数降低,特征温度升高。当m(Bi_(2)O_(3))∶m(B_(2)O_(3))∶m(ZnO)质量比为80∶7∶13,玻璃具有较低的玻璃化转变温度T_(g)(371℃)和膨胀软化温度T_(f)(401℃),热膨胀系数为9.3×10^(-6)℃^(-1),封接温度为450℃,可满足真空玻璃封接对低熔点封接玻璃粉的要求。

掺杂Al_(2)O_(3)对LiNbO_(3)压电陶瓷组织和性能的影响研究

通过真空热压烧结法在900℃、35 MPa下保温120 min制备铌酸锂(LiNbO_(3),简称LN)压电陶瓷,研究掺杂不同含量的Al_(2)O_(3)对其压电性能的影响。通过物相、密度、微观组织、压电性能和介电性能分析发现,在0.5%~3%(摩尔分数)Al_(2)O_(3)掺杂量范围内,所有LN压电陶瓷样品的主体衍射峰位置相同、峰形尖锐,均为类钙钛矿结构;随着Al_(2)O_(3)掺杂量的增加,LN压电陶瓷晶粒尺寸逐渐减小,气孔增大、增多,密度和压电常数d_(33)均呈先增大后减小的趋势,均在Al_(2)O_(3)掺杂量为1%时达到最大,分别为4.65 g/cm^(3)和11.3 pC/N,此压电常数相较于激光烧结法制备的LN压电陶瓷提高了88.3%。在1 MHz测试频率下,LN压电陶瓷的相对介电常数随着Al_(2)O_(3)掺杂量的增加而逐渐增大。

Co_(3)O_(4)/TiO_(2) composite photocatalyst:Preparation and synergistic degradation performance of toluene

TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray electron spectroscopy,and fluorescence spectroscopy.At room temperature,with a relative humidity of 50.0%,the total gas flow rate of 1.0 L·min-1,the space velocity of 1.05×10^(4) h^(-1),and toluene volume concentration of 25.0µL·L^(-1),two 6 W vacuum ultraviolet lamps were used as light sources to catalyze,degrade,and mineralize toluene.The results show that the prepared catalyst is in the shape of nano-ribbons.The loading of Co_(3)O_(4) inhibits the recombina-tion of photogenerated electrons and holes and can effectively improve the catalytic performance.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%Co_(3)O_(4) has the best catalytic effect.When N2 was used as a carrier gas,the degradation rate of tol-uene was only 34.7%.The toluene degradation is mainly due to the photolysis of vacuum ultraviolet light.When air was used as a carrier gas,O_(3) was produced.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%and vacuum ultraviolet synergistical-ly promote toluene degradation.The highest degradation rate of toluene was 91.7%and the mineralization rate was 74.6%.The degradation rate of toluene was 2.6 times that of nitrogen as a carrier gas.

真空冷喷涂BaTiO_(3)颗粒加速过程研究

以BaTiO_(3)陶瓷颗粒为例,模拟了在不同真空冷喷涂工艺参数下的加速过程,探讨了工艺参数对颗粒速度的影响,并通过粒子成像测速装置进行验证,最后采用真空冷喷涂制备了BaTiO_(3)陶瓷涂层并测试涂层性能。模拟结果表明:颗粒速度随着气体压力和气体预热温度的增大而增大;在相同气体压力和预热温度下,颗粒粒径越小受弓形激波的影响越大;多颗粒的加速规律与单颗粒相似。粒子成像测速结果表明在0.2 MPa、300 K或373 K条件下,BaTiO_(3)颗粒速度与模拟结果分别相差约10.2%和8.1%。在该工艺参数下,采用真空冷喷涂制备得到2~3μm连续且致密的BaTiO_(3)涂层,结合力大小为8 N。研究结果表明,数值模拟结合粒子成像测速得到的工艺参数及其影响规律是可靠的,可用于指导柔性陶瓷薄膜的制备。

真空熔炼及热压烧结Sb_2Se_3热电材料的微结构研究

采用石英管真空封装高纯度的Sb粉和Se粉,在800℃下熔炼8h,冷却后制成Sb2Se3粉末,在真空下进行热压烧结(470℃,60 MPa)并保温0.5 h,制备出Sb2Se3块体材料。运用XRD、SEM和EDS法对材料物相、形貌和成分进行了表征。结果表明,真空熔炼合成粉末和热压烧结块体材料的XRD图谱与Sb2Se3的标准衍射图谱(01-072-1184)相对应;Sb2Se3热压块体材料在平行和垂直于热压方向的断面上都分布着大量的层片状结构,平行于热压方向的断面上层片状结构沿某一方向择优生长,而在垂直于热压方向的断面上层片状结构分布更均匀,结晶更充分;材料中Sb和Se的原子百分比分别为40.68%、59.32%,接近于2∶3。

内氧化制备Cu-Al_2O_3复合材料新工艺的研究

提出了一种在低真空度下内氧化制备Cu -Al2 O3合金粉 ,以热锻为后续致密化手段 ,辅以其它工序制备Cu -Al2 O3复合材料的新工艺 ,并进行了初步的试验研究与理论分析。研究结果表明 :在低真空度下内氧化 ,有助于增大内氧化速率、细化Al2 O3粒子并有助于Al2 O3粒子的弥散分布 ;热锻具有显著的致密化作用 ,可代替冷变形作为致密化手段。与现有的内氧化制备工艺相比 ,本文提出的新工艺具有工艺简单、成本低。

低压制备纳米Sb_2O_3粉的研究

用低压蒸发普通 Sb2 O3的方法制备出了纳米 Sb2 O3,分析了生成 Sb2 O3的热力学条件 ,对抑制 Sb2 O3的分解做了详细的理论分析 ,确定了制备纳米 Sb2 O3的温度条件和压力条件 ,证明在一定的氧分压情况下 Sb2 O3是不会分解的 ,测定了 Sb2 O3的粒度和粒度分布 。

真空内氧化法制备α-Al_2O_3/Cu复合材料

对 Cu O-Al体系进行热力学和动力学分析的基础上 ,采用将 Cu O和 Al粉末压块的方法加入到真空条件的 Cu液中使其发生化学反应 ,生成 Al2 O3增强颗粒而获得复合材料。对复合材料进行了扫描电镜观察及 X射线衍射分析 ,并测试了 Al2 O3含量对复合材料电导率的影响。结果表明 ,内氧化法是制备 Al2 O3/ Cu复合材料较理想的方法 ;Al2 O3/ Cu复合材料用于高强度高导电领域时 Al2 O3含量应小于 1 .85 wt%

LT-3铝合金真空钎焊钎缝微观组织分析

对LT-3铝合金真空钎焊工艺进行了研究,利用显微硬度仪、扫描电镜和X射线衍射仪对未焊接母材和钎缝中生成的相和组织进行了分析,并对钎焊接头的断口形貌进行了分析。结果表明:钎缝的显微硬度平均值要比芯层显微硬度的平均值高24.5MHV;钎缝中生成了网状的共晶组织和多种新的金属间化合物;钎缝断裂过程属于混合断裂,断口界面上可以看到多种断裂形貌。

真空铝热还原法生产金属锶──SrCO_3热分解

碱土金属碳酸盐是所有碳酸盐中最稳定的一族·在热力学分析的基础上 ,研究了SrCO3 在各种条件下的热分解规律·实验结果表明 ,添加Al2 O3 ,碳或减少系统分压均可降低SrCO3的分解温度 ,其中添加Al2 O3 的影响最大·当向SrCO3 中添加碳时 ,除降低其分解温度外 ,所产生的CO还可重复利用·

YSZAl_2O_3电解质膜管制备及其应用

以吡啶为分散剂 ,采用真空注浆法制备出膜厚为 0 .2mm、长度为 35mm的致密YSZ Al2 O3 电解质膜管 ,研究了烧结温度对样品致密度和离子电导率的影响 ,确定了获得电解质膜管综合性能的最佳烧结温度范围。用 16 5 0℃烧结 2h制备的致密YSZ Al2 O3 电解质膜管组装成固体氧化物燃料电池 ,以氢气为燃料 ,研究了电池在 6 0 0～ 85 0℃电池的电性能。实验结果表明 ,真空注浆法可制备出具有高密度和高电导率的YSZ Al2 O3 电解质膜管 ,经 16 0 0℃烧结 2h其相对密度已达理论密度的 99.0 % ,接近理论密度。单电池的开路电压最大值为 1.16 4V ,85 0℃时输出功率为 0 .42W。