气氛对Al-MCM-41热稳定性的影响

研究了在不同气氛(氧气、氮气和氨气)条件下Al-MCM-41的热稳定性能,通过比表面积、孔径分布及X射线衍射对Al-MCM-41热稳定性的研究表明:在不同气氛条件下,Al-MCM-41的热稳定性有很大的差异,在氨气或氮气气氛下,处理温度高达1010℃条件下,Al-MCM-41仍然具有良好的介孔结构,但在氧气中介孔结构热稳定温度不超过900℃。     

有机波导制备工艺对乐甫波传感器性能的影响

研究了基于PMMA波导的乐甫波传感器,研究了器件的插损以及质量灵敏度随波导层厚度变化的关系.采用低浓度、低粘度的前驱溶液,多步旋涂工艺制备了PMMA波导薄膜,降低了器件的插损,实现了2.18/μm的"有效厚度",器件的质量灵敏度达705cm2/g,与前人相比提高了1倍.     

铝硅质介孔分子筛Al-MCM-41的合成与水热稳定性评价

以水玻璃为硅源,铝酸钠为铝源,以十六烷基三甲基溴化铵(C16H33(CH3)3NBr)为模板剂,在水热条件下合成出了Al-MCM-41介孔分子筛.研究了合成母液中SijO2:Al2O3摩尔比对合成Al-MCM-41的影响;合成过程中母液搅拌时间不同对样品孔序度的影响;以及铝引入到MCM-41骨架后,样品的水热稳定性评价.通过对样品的XRD表征和SAXS表征,得到如下结论:随母液中SiO2:Al2O3摩尔比的增加(30～50),Al-MCM-41分子筛孔容变大;母液搅拌时间越长,样品的孔序度越好;把铝引入到MCM-41骨架中,可有效改善MCM-41的水热稳定性.     

Esterification of levulinic acid into hexyl levulinate over dodecatungstophosphoric acid anchored to Al-MCM-41

Aluminum-substituted MCM-41 (Al-MCM-41) were hydrothermally synthesised and used as supports to fabricate the mesostructured H₃PW₁₂O₄₀ (HPW) solid acid catalysts via an impregnation method. The influences of various HPW loadings on the structures of the catalysts were verified by X-ray diffraction (XRD), nitrogen physisorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy and Fourier-transform infrared spectroscopy (FT-IR) measurements and their acidities were evaluated by infrared of pyridine adsorption (Py-IR) and temperature-programmed desorption of ammonia (NH₃-TPD) measurements. The optimisation of the reaction conditions for levulinic acid esterification with n-hexanol such as the reaction temperature and time, the reactant molar ratio, and the catalyst dosages was performed to maximise the conversion of levulinic acid. The effects of various HPW loadings on the conversion of levulinic acid were investigated under the optimised and harsh reaction conditions. The reusability of the catalysts was also investigated. The results showed that these catalysts retained the hexagonal mesoporous structure of Al-MCM-41 and the Keggin characteristic of HPW, although their textural parameters decreased with increasing loading of HPW. In particular, the catalysts were found to be efficient in the esterification of levulinic acid with n-hexanol, resulting in hexyl levulinate which could replace the petroleum-derived chemical feedstocks.     

硅烷修饰对环氧树脂/纳米介孔MCM-41复合材料性能的影响

用偶联剂将纳米介孔MCM-41粉体修饰后与环氧树脂溶液共混,制备出环氧树脂/MCM-41纳米复合材料.研究了偶联剂的含量和不同溶剂的修饰对纳米介孔MCM-41粉体分散性和复合材料力学性能的影响.结果表明,加入适量的偶联剂和在极性较小的介质中修饰,可制备出单分散的纳米介孔MCM-41颗粒增强的新型网络复合材料.偶联剂中的有机基团-(CH2)3-NH2不仅进入孔道、修饰了MCM-41的孔壁,而且使介孔分子筛保持了有序的孔道结构.环氧树脂高分子链与偶联修饰后的MCM-41颗粒的内、外表面以强烈的化学键结合,使MCM-41颗粒均匀分散在聚合物基体中,提高了材料的力学性能,其拉伸强度比基体树脂提高了69%,杨氏模量提高了90%.     

Structure and photocatalytic activity studies of TiO2-supported over Ce-modified Al-MCM-41

Ce-Al-MCM-41, TiO₂/Al-MCM-41 and TiO₂/Ce-Al-MCM-41 materials with varying contents of Ce (by impregnation) and TiO₂ loaded (by solid-state dispersion) on Al-MCM-41 support are prepared. The Ce modified and TiO₂ loaded composite systems are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS) techniques. The DRS and XPS of low Ce content (0.2-0.5 wt.%) modified Al-MCM-41 samples are showing more characteristic of Ce³⁺ species wherein cerium in interaction with Al-MCM-41 and that of high Ce (0.8, 3.0 wt.%) content modified samples are showing the characteristic of both Ce⁴⁺and Ce³⁺species. A series of Ce-modified Al-MCM-41 and TiO₂ loaded composite catalysts are evaluated for photocatalytic degradation of phenol under UV irradiation. Low Ce content in Ce³⁺ state on Al-MCM-41 is showing good photoactivity in comparison with high Ce content samples and pure ceria. The composite TiO₂/Ce-Al-MCM-41 is showing enhanced degradation activity due decreased rate of electron-hole recombination on TiO₂ surface by the redox properties of cerium. The photocatalyst TiO₂/Ce-Al-MCM-41 with an optimum of 10 wt.% TiO₂ and 0.3 wt.% Ce is showing maximum phenol degradation activity. The possible mechanism of phenol degradation on the composite photocatalyst is proposed.     

Synthesis of Ag-AgBr/Al-MCM-41 nanocomposite and its application in photocatalytic oxidative desulfurization of dibenzothiophene

A series of Ag-AgBr/Al-MCM-41 nanocomposites were synthesized by dispersion of Ag-AgBr on mesoporous silica Al-MCM-41 obtained from natural bentonite. The synthesized Ag-AgBr/Al-MCM-41 composites with Ag nanoparticles growing on the surface of Al-MCM-41 were used for photocatalytic oxidative desulfurization of dibenzothiophene. The physical properties of Ag-AgBr/Al-MCM-41 were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Ultraviolet–visible diffuse reflection spectroscopy (UV–Vis DRS), photoluminescence (PL) emission spectra, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity results showed that in the presence of 40% Ag-AgBr/Al-MCM-41 photocatalyst the oxidative desulfurization of dibenzothiophene reached the maximum efficiency at 99.22% and the photocatalytic activity still keeps high level after four cycles.     

Preparation of mesoporous Al-MCM-41 with stable tetrahedral aluminum using ionic liquids as a single template

Mesoporous Al-MCM-41 materials were synthesized using room temperature ionic liquid 1-cethyl-3-methylimidazolium bromide ([C₁₆mim]Br) as a single template and characterized by X-ray diffraction, N₂ adsorption-desorption, ICP-AES, ²⁷Al MAS NMR and TEM technique. These mesoporous materials exhibit hexagonal p6m pore architectures, and possess high surface area and narrow pore distribution. All aluminum in as-synthesized samples exists in tetrahedral coordination. Upon calcination nearly all aluminum still remains the tetrahedral coordination even when the Si/Al ratio is as low as 15. This indicates that the tetrahedral aluminum of Al-MCM-41 is stable.     

金属陶瓷惰性阳极材料的制备及性能

为了找到制备金属陶瓷惰性阳极材料的合理方法,采用一次烧结和两次烧结这两种制备方法制备惰性阳极材料,比较了这两种方法制备的材料的密度、电导率、腐蚀率、抗弯强度以及抗热震性等性能.通过比较发现两次烧结制备出的材料性能较好.两次烧结得到的阳极试样中金属银能够较好的沿着陶瓷颗粒的轮廓分布,而形成了联通的网状结构.这样的结构不仅能够使得导电电子形成连通的通路,从而提高试样的电导率,还能提高材料的力学性能和抗热震性.两次烧结得到的试样密度要高于一次烧结得到的试样,这对提高试样的抗腐蚀性和电导率有利.     

Preparation of TiO2/Al-MCM-41 mesoporous materials from coal-series kaolin and photodegradation of methyl orange

TiO₂/Al-MCM-41 mesoporous materials were prepared via sol-gel method by loading titania onto Al-MCM-41 mesoporous molecular sieve by hydrothermal treatment from coal-series kaolin as raw material. The TiO₂/Al-MCM-41 mesoporous materials were characterized by XRD, FT-IR, HRTEM, N₂ adsorption-desorption and the photocatalytic degradation of methyl orange solution under visible light irradiation. The results showed that the TiO₂/Al-MCM-41 mesoporous materials possessed a high surface area of 369.9–751.3 m²/g and a homogeneous pore diameters of 2.3–2.8 nm. The titania crystalline phase was anatase, and the particles size of TiO₂ increased with TiO₂ content. The Al-MCM-41 mesoporous materials exhibited excellent photodegradation activity under visible-light irradiation for methyl orange.     

Effect of preparation conditions on the properties of bioactive glasses for testing SBF

A simulated body fluid (SBF) with ion concentrations similar to body fluid, proposed by Kokubo et al., is widely used to evaluate bone-bonding potential through the formation of an apatite layer. To be confident of the evaluation of the potential for the apatite formation in SBF, standard substrates are required. Although Na₂O–CaO–SiO₂ glasses have been focused upon as candidate standard substrates, it has not been clarified whether the preparation conditions of the glasses affect their apatite formation potential in SBF. In this study, Na₂O–CaO–SiO₂ glasses were prepared by a conventional melting–quenching method with different melting periods and annealing processes to examine their properties, including apatite formation in SBF. The Na₂O–CaO–SiO₂ glasses show reproducible apatite-forming ability when prepared using moderate melting and annealing processes, and can be useful substrates to test the reproducibility of SBF.     

a-Si:H薄膜的制备工艺对其光电特性的影响

采用MW-ECR CVD方法制备的a-SiH薄膜在模拟太阳光照射下进行光敏性(σp.σ d)和光致衰退测试.对比了有、无热丝辅助沉积的薄膜的光电特性,得出沉积温度是影响薄膜光敏性的主要因素,而适当温度的热丝辅助对于薄膜的光致衰退有一定延缓作用.     

Influence of raw powder preparation routes on properties of hydroxyapatite fabricated by 3D printing technique

A comparison between two routes of raw powder preparation, namely spray drying and grinding, for 3D printing of hydroxyapatite was carried out. Hydroxyapatite particles prepared by the spray drying technique were spherical in shape whereas the grinding route gave irregular-shaped agglomerates. Spray-dried powders had higher tap density than milled powders, however milled powders yielded 3DP specimens with greater green density and strength. After sintering at 1300 °C for 1 and 5 h, samples fabricated from milled powders showed a 32% higher in sintered density, a 20% lower in porosity and approximately two times higher flexural modulus and strength than samples fabricated from spray-dried powders. This difference was related to the better packing characteristics of milled powders which promoted improved inter- and intra-particle densification during high temperature sintering compared to the spray-dried powders which yielded only high intra-particle densification, but lower inter-particle densification.     

Piezoelectric properties of niobium-doped 18PMN-41PZ-41PT ceramics

The effects of various amounts of excess niobium ions added to the 18PMN-41PZ-41PT three-component ceramics system on the crystal structure, microstructure, polarization versus electric field, strain versus electric field and piezoelectric properties, have been studied. It was found that addition of niobium ions to 18PMN-41PZ-41PT induced a change in the crystal structure from rhombohedral to tetragonal phase. The excessive niobium ions also formed a micro-second phase which existed in the grain boundary, which could refine and uniform the grain. The refined and uniformed microstructure was found to increase the remanent polarization, saturation strain, planar coupling coefficient, K _p, and mechanical quality factor, the best value of K _p being 69%.     

Piezoelectric properties of hot-pressed 18PMN-41PZ-41PT ceramics

Piezoelectric ceramics of 18PMN-41PZ-41PT were sintered by hot-pressing and normal sintering methods. The microstructure, density, P-E curve and S-E curve were also compared. The best hot-pressing condition for 18PMN-41PZ-41PT material was obtained at a temperature of 1000 °C and a pressure of 700 kg cm⁻²; it could achieve 99.66% theoretical density and a fine, uniform microstructure as a result of a 200–300 °C decrease in the sintering temperature. A higher coercivity was attained with the density increase. The fine, uniform microstructure also enhanced the increase in polarization and strain.     

制备方法对W-10%Ti合金组织性能的影响

以高纯钨粉、钛粉和TA2钛片为原料,分别采用液相烧结法和熔渗法制备了Ti含量为10%的W-Ti合金;测量了W-10%Ti合金的密度和杂质(C、N和O)含量,研究了不同方法制备的W-Ti合金的相组成和微观形貌.结果表明,熔渗法制备的W-Ti合金致密度达94%以上,相结构由含有较多富Ti相的固溶体β(W/Ti)组成;液相烧结的合金致密度为90%左右,组织相对均匀;两种方法制备的合金杂质(C、N和O)含量均较低.探讨了液相烧结制备W-10%Ti合金时固溶体扩散形成的机理.     

γ-Al2O3多孔膜的制备与性能研究

以无机盐AlCl3·6H2O为初始原料,采用溶胶-凝胶法通过调节pH值控制溶胶体系的稳定性制备出具有耐高温、耐腐蚀性的γ-Al2O3微孔膜,利用差热、BET和SEM对薄膜的组成、结构和表面形貌进行了分析表征.并对溶胶制备过程中的主要影响因素以及膜制备过程中膜性能的各种影响因素进行了深入探讨.     

IPMC人工肌肉的制备工艺研究

为了降低成本并改善材料性能,采用导电性良好的Ag作为IPMC人工肌肉两侧金属电极,利用还原法制备IPMC,并设计了测试IPMC人工肌肉性能的平台,对样件使用寿命进行测试。结果表明,改良后的制备工艺,使制备周期缩短了30%,IPMC样件制备质量均能达到使用要求;未经表面保水处理的IPMC在空气中的动作次数为60次左右,而经过表面保水处理的IPMC在空气中的动作次数可以提高到90次,对IPMC表面经过保水处理可以使其使用寿命提高50%左右。     

Textural features of highly ordered Al-MCM-41 molecular sieve studied by X-ray diffraction,nitrogen adsorption and transmission electron microscopy

The preparation of a Al-MCM-41 mesoporous materials has been carried out using silica-gel and pseudoboehmite as silica and aluminum sources, respectively, and surfactant cetyltrimethylammonium bromide as structure template. The textural properties of the calcined Al-MCM-41 were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ isothermal adsorption measurements. The hexagonal structure parameter a_o was calculated based on d₍₁₀₀₎ XRD reflection as 4.75 nm. TEM images revealed the formation of a well-ordered Al-MCM-41. Accordingly, nitrogen adsorption measurements (BJH) showed a material with very narrow distribution and medium pore diameter of 3.14 nm. Mesopore volume based on adsorbed nitrogen was 0.51 cm³ g^− 1. Through a combination of XRD and N₂ adsorption data, the thickness of the channel walls of 1.61 nm could be calculated.