Effect of SiC and Al2O3 particles on the electrodeposition of Zn, Co and ZnCo: II. Electrodeposition in the presence of SiC and Al2O3 and production of ZnCo–SiC and ZnCo–Al2O3 coatings

SiC or Al₂O₃ microsized particles were added to acid sulfate-based solutions for the electrodeposition of Zn, Co, and ZnCo. Initially, their effects on the electrochemical processes were evaluated. The Zn electrodeposition rate was increased in both SiC and Al₂O₃-loaded solutions. The Co electrodeposition rate was also increased by SiC. However, Al₂O₃ decreased it, especially at the beginning. Both SiC and Al₂O₃ influenced the electrodeposition of ZnCo positively at moderate loadings. The factors involved in producing ZnCo–SiC and ZnCo–Al₂O₃ composites were evaluated. ZnCo–SiC composites could be deposited with a higher [Co/Zn] ratio in the metal matrix than for pure ZnCo. In ZnCo–Al₂O₃, the [Co/Zn] ratio was smaller than in ZnCo and ZnCo–SiC. It was necessary to reduce the CoSO₄ concentration to improve the Al₂O₃ co-deposition. The variation in [Co/Zn] ratio could, in principle, be related to the effects of SiC and Al₂O₃ on the individual Zn and Co electrodeposition.     

Crystallographic characterization of silicon nitride ceramics sintered with Y2O3–Al2O3 or E2O3–Al2O3 additions

Silicon nitride ceramics were sintered using Y₂O₃–Al₂O₃ or E₂O₃–Al₂O₃ (E₂O₃ denotes a mixed oxide of Y₂O₃ and rare-earth oxides) as sintering additives. The intergranular phases formed after sintering was investigated using high-resolution X-ray diffraction (HRXRD). The use of synchrotron radiation enabled high angular resolution and a high signal to background ratio. Besides the appearance of β-Si₃N₄ phase the intergranular phases Y₃Al₅O₁₂ (YAG) and Y₂SiO₅ were identified in both samples. The refinement of the structural parameters by the Rietveld method indicated similar crystalline structure of β-Si₃N₄ for both systems used as sintering additive. On the other hand, the intergranular phases Y₃Al₅O₁₂ and Y₂SiO₅ shown a decrease of the lattice parameters, when E₂O₃ was used as additive, indicating the formation of solid solutions of E₃Al₅O₁₂ and E₂SiO₅, respectively.     

Al2O3-3Al2O3·2SiO2-ZrO2耐火材料的相组成

Al2O3-SiO2-ZrO2系耐火材料应用范围广,特别被用作陶瓷辊,具有力学强度高、抗热震性能优良、耐碱类化合物侵蚀和高温蠕变率低的特性。Al2O3-SiO2-ZrO2系耐火材料性能很大程度上取决于其结晶相和玻璃相的总量和化学成分,采用定量XRPD和XRF研究了原料中Al2O3/SiO2比和氧化铝颗粒尺寸分布对结晶相和玻璃相的总量及其化学成分的影响。耐火材料由莫来石、刚玉、ZrO2的多晶体和总量各异的玻璃相组成。莫来石含量及其晶胞参数和成分随烧成温度改变,但主要受原料中Al2O3/SiO2比的影响。     

Al2O3/Fe2O3吸附剂脱除硫化氢的性能

采用共沉淀法制备了氧化铝改性的氧化铁吸附剂,并采用比表面积(BET)、X射线衍射(XRD)技术对吸附剂进行了表征。在固定吸附床上,考察了制备条件及吸附条件对吸附剂脱除硫化氢性能的影响。结果表明,引入氧化铝能显著提高氧化铁对硫化氢的吸附净化能力。氧化铁与氧化铝质量比为1∶0.5,造孔剂十六烷基三甲基溴化铵(CTAB)质量分数为2%,焙烧温度500℃时,采用共沉淀法的负载氧化铝吸附剂的吸附效果最好。在气速20 mL/min,吸附温度80℃时,脱硫率和穿透硫容可分别达到99.3%和105 mg/g,其穿透硫容比未经改性的活性氧化铁提高了49.8 mg/g。     

Influence of Al2O3 whisker concentration on flexural strength of Al2O3(w)–ZrO2 (TZ-3Y) composite

On investigating the possibility of using alumina whisker reinforced 3 mol% Yttria stabilized Tetragonal Zirconia (TZ-3Y) composite for bioceramic applications, presented here is the influence of varying whisker concentration (2, 5, 10, 15 and 20 wt%) on flexural strength of the composite. Whiskers of hydrothermally synthesized Ammonium Aluminum Carbonate Hydroxide (AACH) were used for composite synthesis. These whiskers transformed in situ into alumina during sintering. It was found that with addition of alumina whiskers, strength was increased and reached a maximum value of 1212±60 MPa and 1325±65 MPa, in pure and 1 wt% CTAB added samples respectively, at a concentration of 10 wt% Al₂O₃ whiskers. The strength values of the synthesized composite can compete well with commercially available materials for dental applications.     

添加Al2O3溶胶改善Al2O3-MA浇注料的抗侵蚀性

以铝酸钙水泥(CAC)为结合剂的传统Al2O3-MA浇注料在热处理过程中生成CA6,导致浇注料产生膨胀而降低其抗渣性能。巴西研究人员制备了氧化铝溶胶(ColAlu)结合的Al2O3-MA浇注料,以提高其抗渣侵蚀性,并与水合氧化铝(HA)结合和铝酸钙水泥结合的Al2O3-MA浇注料进行了对比。     

An XRD, FTIR and TPD Investigation of NO2 Surface Adsorption Sites of δ, γ Al2O3 and Barium Supported δ, γ Al2O3

In this paper an XRD, FTIR and TPD investigation of NO₂ surface adsorption sites of , Al₂O₃ and barium supported , Al₂O₃ is reported. Aim of this study is to bring additional light on the surface structures involved in NOx adsorption. Two samples of barium supported aluminas have been prepared and aged at 800 °C. These samples were characterised in comparison with the relative alumina support. The XRD characterisation of these samples shows the presence of barium carbonate and barium aluminate supported on alumina. The comparison of the FTIR spectra, before and after NO₂ adsorption, has revealed the formation, upon NO₂ contact, of a complex variety of nitrate and nitrite groups. The thermal desorption of nitrate and nitrite species has been simultaneously studied by means of FTIR spectroscopy and by TPD technique. By comparing the structural, adsorptive and spectroscopic results obtained on alumina and on barium supported alumina samples, a hypothesis on the basic sites active in NO₂ adsorption and of the possible decomposition paths induced by thermal heating are proposed.     

Fe2O3/Ni2O3/Al2O3催化剂制备及其催化氧化靛蓝废水研究

以三氧化二铝为载体,采用浸渍沉淀法制备系列Fe2O3/Ni2O3/Al2O3催化剂。采用TG-DTA,XRD及ESEM等技术对催化剂进行表征,确定催化剂的最佳焙烧温度为460℃。以次氯酸钠为氧化剂,同时考察m(三氧化二镍)/m(三氧化二铝)、m(三氧化二铁)/m(三氧化二镍)、m(次氯酸钠)∶m(靛蓝废水)、pH对印染靛蓝废水处理的影响。结果表明:m(三氧化二镍)/m(三氧化二铝)=0.3,m(三氧化二铁)/m(三氧化二镍)=0.04,m(次氯酸钠)∶m(靛蓝废水)=1∶11,pH=7,反应温度为20℃,常压反应时间为2 h时,COD的去除率为95.3%。     

Densification and characterization of SiO2B2O3CaOMgO glass/Al2O3 composites for LTCC application

A glass/ceramic composite using lead-free low melting glass (SiO₂B₂O₃CaOMgO glass) with Al₂O₃ fillers was investigated. X-ray diffraction analysis revealed that the anorthite and cordierite phase appeared in the sintered composites. The dilatometric analysis showed that the onset of shrinkage took place at ∼624 °C for all the samples and the onset temperature was independent on the content of glass. The low melting glass significantly promoted densification of the composites and lowered the sintering temperature to ∼875 °C. The addition of 50 wt% glass sintered at 875 °C showed ε_r of 7.3, tan δ of 1.15×10⁻³, TEC of 5.41 ppm/°C, thermal conductivity of 3.56 W/m °C, and flexural strength of 184 MPa. The results showed that the SiO₂B₂O₃CaOMgO glass/Al₂O₃ composites were strong potential candidates for low temperature cofired ceramic substrate applications.     

Investigation of the effect of ZrO2 and ZrO2/Al2O3 additions on the hot-pressing and properties of equimolecular mixtures of α- and β-Si3N4

In this work, hot-pressing of equimolecular mixtures of α- and β-Si₃N₄ was performed with addition of different amounts of sintering additives selected in the ZrO₂–Al₂O₃ system. Phase composition and microstructure of the hot-pressed samples was investigated. Densification behavior, mechanical and thermal properties were studied and explained based on the microstructure and phase composition. The optimum mixture from the ZrO₂–Al₂O₃ system for hot-pressing of silicon nitride to give high density materials was determined. Near fully dense silicon nitride materials were obtained only with the additions of zirconia and alumina. The liquid phase formed in the zirconia and alumina mixtures is important for effective hot-pressing. Based on these results, we conclude that pure zirconia is not an effective sintering additive. Selected mechanical and thermal properties of these materials are also presented. Hot-pressed Si₃N₄ ceramics, using mixtures from of ZrO₂/Al₂O₃ as additives, gave fracture toughness, K_IC, in the range of 3.7–6.2 MPa m^1/2 and Vicker hardness values in the range of 6–12 GPa. These properties compare well with currently available high performance silicon nitride ceramics. We also report on interesting thermal expansion behavior of these materials including negative thermal expansion coefficients for a few compositions.     

一种微孔化结构Al2O3-Cr2O3耐火材料

申请号:CN201310706638.8公开号:CN103693981A申请(专利权)人:中钢集团洛阳耐火材料研究院有限公司本发明属于耐火材料领域,提供一种微孔化结构的Al2O3-Cr2O3耐火材料,其特征采用直接加入Al2O3-Cr2O3造粒料替代现有技术中分别加入氧化铬绿微粉和烧结氧化铝微粉来作为制备基质的原料,利用造粒料中氧化铬绿含量均一、分散均匀的特性,避免氧化铬绿富集,使得固溶成孔大小均一,通过调整造粒料中氧化铬绿含量来达到控制孔径的目的,制得微孔化结构的Al2O3-     

La2O3的添加方式对Al2O3热稳定性的影响

采用3种不同添加方式制备La₂O₃改性的Al₂O₃材料La-Al₂O₃。La-Al₂O₃分别经500 ℃、1 000 ℃和1 200 ℃焙烧,采用物理吸附、X射线衍射和荧光光谱等对高温处理的La-Al₂O₃进行比表面积和结构表征。结果表明,La₂O₃的添加能有效抑制Al₂O₃在高温条件下向热力学稳定态α-Al₂O₃转变,同时提高高温处理后La-Al₂O₃比表面积,使Al₂O₃热稳定性得到明显提高。在3种La₂O₃添加方式中,La(NO₃)₃浸渍法效果最为显著,制得的La-Al₂O₃(N)材料经1 200 ℃焙烧4 h的比表面积为30 m²·g^－1,是未经改性的Al₂O₃样品经同等温度焙烧比表面积的2.2倍。     

Influences of La and Er on structure and properties of Bi2O3–B2O3 glass

Bi₂O₃·2B₂O₃ glasses doped with La₂O₃ and Er₂O₃ were prepared by the melting-quenching method with AR-grade oxides. IR analysis was used to investigate the glass network structure. The characteristic temperatures including the glass transition temperature (T_g), crystallization temperature (T_p), and melting temperature (T_m) were estimated by DSC. The coefficient of thermal expansion (α), mass density (D), and Vickers hardness (H_v) were also measured. The results show that the basic network structure of Bi₂O₃·2B₂O₃ glasses doped with rare-earth oxides consists of chains composed of [BO₃], [BO₄], and [BiO₆] units. La₂O₃ and Er₂O₃ act as network modifiers. As the doping concentrations of the rare-earth oxides were increased, T_g increased and α decreased, indicating that a more rigid glass was obtained. Er₂O₃ reduces the melting temperature and prevents glass crystallization. La₂O₃ contributes to the improvement of the microhardness of Bi₂O₃·2B₂O₃ glass.     

Pressureless sintered Al2O3–SiC nanocomposites

Al₂O₃ + 5 vol% SiC composite ceramics were prepared via a conventional powder processing route followed by pressureless sintering. Commercially available Al₂O₃ and SiC powders were milled together in an aqueous suspension. The slurry was freeze granulated, and green bodies were obtained by cold isostatic pressing of the granules. Pressureless sintering was carried out in a nitrogen atmosphere at 1750 and 1780 °C. Near full density (>99%) was achieved at 1780 °C. Densification at the lower sintering temperature was promoted by smaller additions of MgO. Vickers hardness and indentation fracture toughness varied around 18 GPa and 2.3 MPa m^1/2 after sintering at 1780 °C. Transmission electron microscopy revealed that the SiC particles were located predominantly to the interior of the matrix grains and well distributed throughout the composite microstructures. The intragranular particles had sizes in the range 50–200 nm while the intergranular particles were larger, typically 200–500 nm in diameter.     

V2O5、NiO、Fe2O3和钒渣对Al2O3/MgAl2O4的腐蚀机理

研究了V2O5、NiO、Fe2O3和钒渣对Al2O3和MgAl2O4尖晶石的腐蚀。把Al2O3和MgAl2O4试样分别同上述氧化物一起从室温加热到1 400℃、1 450℃和1 500℃,加热速率为10℃.min-1。用XRD和SEM对每个系统的腐蚀机理进行了分析。结果显示,所研究的氧化物对Al2O3的影响弱于对MgAl2O4的影响。氧化铝被NiO侵蚀形成NiAl2O4尖晶石,MgAl2O4尖晶石被V2O5侵蚀形成MgV2O6。本文还观察到钒渣中的成分Fe2O3、Mg、Ni、V和Fe分散到了Al2O3结构中。另一方面,Fe2O3、Ca、S、Si、Na、Mg、V和Fe分散到了MgAl2O4结构中。最后,把得到的结果与FactSage软件的预测结果进行了对比。     

Dehydrogenation of propane in the presence of N2O over In2O3―Al2O3 mixed oxide catalysts

Dehydrogenation of propane coupled with N₂O over a series of binary In₂O₃―Al₂O₃ mixed oxides was investigated. In contrast to the poor performance for sole N₂O decomposition, a remarkable synergy was identified between N₂O decomposition and propane dehydrogenation. Among the catalysts tested, the In₂O₃―Al₂O₃ sample containing a 20 mol% In₂O₃ showed the highest activity for propane dehydrogenation in the presence of N₂O. Moreover, stability far superior to those of the conventional iron-based materials was observed, attributable to the moderate surface acidity of the In―Al―O composite. The essential role of N₂O is suggested to generate active oxygen species facilitating propane dehydrogenation.     

气相氟化四氯乙烯的ZnF2/Al2O3催化剂

采用浸渍法制备了ZnO/Al2O3催化剂,考察了载体Al2O3的焙烧温度对催化剂性能的影响。并对催化剂进行了X射线衍射（XRD）、Raman光谱、氨气程序升温脱附（NH3-TPD）和BET表征。结果表明：随着Al2O3焙烧温度升高,从900 ℃开始,?-Al2O3逐渐向?-Al2O3和α-Al2O3转变,1100 ℃焙烧样品中?-Al2O3的XRD峰强度达到最大。当温度继续升高,?-Al2O3将转变成α-Al2O3。Al2O3载体经过1100 ℃焙烧制得的ZnF2/Al2O3催化剂催化性能最高,当反应温度为300 ℃时,四氯乙烯的转化率为45.7%,HCFC-123(2,2-二氯-1,1,1-三氟乙烷)和HCFC-124(2-氯-1,1,1,2-四氟乙烷)的总选择性为48.2%。     

Al2O3包覆LiNi0.5Mn0.5O2的电化学性能

通过溶胶-凝胶法在LiNi0.5Mn0.5O2表面包覆一层Al2O3,采用X射线衍射(XRD),扫描电镜(SEM),恒电流充放电和电化学阻抗谱(EIS)对材料的结构和形貌及电化学性能进行了研究。实验结果表明,经过包覆后,有效地抑制了电解液对正极材料的侵蚀,包覆量为1.0%(质量分数)放电容量略有提高,循环性能也得到明显改善。因此包覆是一种改善LiNi0.5Mn0.5O2材料的电化学性能的有效方法。