空心鼓状多级孔钛硅氧化物的合成及氧化-吸附脱硫性能研究

燃料油中的含硫化合物燃烧后会形成SO _x 排放到空气中,不仅引起环境污染,而且危害人类健康。因此,温和条件下的超深度脱硫技术已成为众多科研工作者关注的焦点。以表面活性剂-聚电解质形成的介观复合物为模板,成功合成了空心鼓状含钛多级孔结构二氧化硅材料。通过小角X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、氮气吸附-脱附以及紫外-可见光谱表征发现,所得到的含钛二氧化硅材料具有立方Pm-3n有序介观相态、多级介孔结构和较高骨架钛含量。由于多级介孔结构和丰富骨架钛活性位点的存在,该二氧化硅在室温下表现出优良的氧化脱硫催化活性和稳定性。此外,含钛二氧化硅对强极性氧化产物砜具有明显的吸附作用,实现了氧化-吸附一步法脱硫。     

乙醇辅助氨基改性NCR-MCM-48分子筛的制备及其对Cr(VI)的吸附性能

以稻壳灰提纯出的硅胶为无机组装硅源,乙醇为辅助试剂,通过水热合成法制备了CR-MCM-48分子筛,并对其氨基改性接枝制备NCR-MCM-48介孔分子筛。实验探讨了硅钠比、晶化温度、晶化时间及乙醇含量对CR-MCM-48介孔结构和形貌的影响。通过X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂吸附-脱附曲线和红外光谱(FT-IR)对合成材料进行了结构和形貌表征,并对NCR-MCM-48介孔材料吸附水溶液中Cr(VI)的性能进行了评价。结果表明,当物料摩尔比n(Si)∶n(CTAB)∶n(H₂O)∶n(NaOH)∶n(C₂H₅OH)=1.0∶0.65∶62∶0.625∶0.25,晶化温度为393 K,晶化时间为72 h,焙烧温度为823 K时,组装合成的CR-MCM-48介孔材料有序度最好。热力学分析结果表明,NCR-MCM-48对Cr(VI)的吸附是自发、吸热反应。在吸附温度为308 K、pH=2.0、吸附时间为150 min的条件下,NCR-MCM-48吸附剂对Cr(VI)的最大吸附容量为88.9 mg·g^-1。     

Synthesis of mesoporous LTA zeolites with large BET areas

Mesoporous LTA zeolites were successfully synthesized by performing a direct hydrothermal synthesis using tetraethylorthosilicate (TEOS) and an organosilane surfactant as the silicon source and the mesopore-generating agent, respectively. The as-synthesized materials were characterized using a complementary combination of X-ray diffraction, nitrogen adsorption–desorption measurements, scanning electron microscopy, and transmission electron microscopy. The characteristics of the samples are comparable with the materials synthesized with sodium metasilicate nonahydrate as the silicon source. The influence of the adding amount of the amphiphilic organosilane [3-(trimethoxysilyl)propyl]-tetradecyl-dimethylammonium chloride on the mesoporous and microporous properties of the samples were investigated. Our results indicate that the materials synthesized with TEOS possess a mesoporous-microporous hierarchical structure. Moreover, the synthesized materials have a large Brunauer–Emmett–Teller area of up to 244 m²/g and present consistent mesopore diameter distributions centered at approximately 4.6 nm. The results of thermogravimetric analysis prove that more amphiphilic surfactant molecules bond to the LTA zeolite framework surface synthesized using TEOS.     

Characteristics of vanadium-substituted mesoporous silica with wormhole framework structure: effects of vanadium content

Vanadium-substituted wormhole framework structure (V-WMS) mesoporous silicas (V-WMS) with various Si/V ratios in the range of 15 and 200 were prepared at ambient temperature by neutral surfactant templating pathway. The materials were synthesized by using dodecylamine as a template and tetraethylorthosilicate as a silicon source. They were characterized by energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), N₂ adsorption–desorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared absorption spectroscopy (FT-IR) and ultraviolet-visible absorption spectroscopy. V-WMS samples shown characters of larger framework wall thickness, small crystallite domain sizes, and complementary textural mesoporosities in comparison with M41S materials. These mesoporous V-WMS samples exhibited irregularly shaped mesoscale fundamental particles which aggregated into larger particles. They also demonstrated better thermal stability than MCM-41. An absorption band of FT-IR at ca. 960 cm⁻¹ was assigned to the vibration of Si–O–V linkages. These samples also showed one strong UV–visible absorbance with overlapping maxima at about 255 nm. The results show that vanadium was incorporated into the structure of wormhole mesoporous silica (WMS). However, for V-WMS with high vanadium content (Si/V < 25), a broad shoulder in XRD pattern was observed at about 3–4°, suggesting the presence of impurity phase of vanadium species in the sample. The efforts in preparing V-WMS specimens by neutral-template synthesis route had led to new mesoporous silica molecular sieves with catalytically active vanadium centers.     

Synthesis of mesoporous Si/SiC with three-dimensional structure derived from C/silicalite-1 via magnesiothermic reduction

C/silicalite-1 composites were successfully synthesized by using industrial silica sol as silica source and multiwalled carbon nanotube (MWCNTs) as carbon source under hydrothermal method. Then, C/silicalite-1 composites were transformed into mesoporous Si/SiC through magnesiothermal reduction at relatively low temperature (650 °C). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer–Emmett–Teller analysis (BET). The XRD patterns and TEM micrographs exhibit that C/silicalite-1 composites are transformed into Si/SiC. The SEM images exhibit that Si/SiC keeps the three-dimensional structure of silicalite-1. BET analysis shows that the specific surface areas and mesoporous distribution of Si/SiC are 274 m²/g and 4.69 nm, respectively.     

气溶胶辅助自组装制备中空球形二氧化硅材料的机理及应用

以正硅酸乙酯（TEOS）和甲基三乙氧基硅烷（MTES）为混合硅源,不同配比条件下采用气溶胶辅助自组装技术制备高比表面积的中空介孔二氧化硅纳米颗粒（HMSNs）,并应用于原花青素（PC）的负载,以期提高其生物利用度。利用扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、红外图谱（FTIR）和粒径分析（DLS）等对载体颗粒的形成过程、结构特性以及负载性能进行探究,基于BET分析方法计算HMSNs的比表面积,并对孔径分布进行分析。结果表明,前体溶液水解的活性中间体缩合形成二氧化硅网络结构,同时雾化后的气溶胶液滴在径向浓度梯度自组装成球形结构,水解-缩合与自组装过程协同作用促进了分散性良好的介孔二氧化硅（MSNs）的形成。经退火处理、纯化操作去除模板剂NaCl和表面活性剂十六烷基三甲基溴化铵（CTAB）,最终获得具有中空结构的HMSNs。当TEOS/MTES的摩尔比为60/40时,HMSNs具有极大的比表面积（1083m²/g）和较大的孔容积（0.37cm³/g）,其孔径主要分布在2~4nm之间,PC在HMSNs上的负载量可达30.7mg/g。     

介孔SiO2薄膜的制备与表征

采用浸涂法,以载玻片为基底,十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,丙三醇为成膜干燥控制剂,制备出有序的介孔SiO2薄膜.利用X射线衍射仪(XRD)、红外光谱(IR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对其结构进行表征.XRD测试结果表明,合成的薄膜具有MCM-41介孔结...     

氮化硅薄膜生长随时间演化过程及其特性研究

氮化硅SiN_x薄膜凭借介电常数高和稳定性好的特点而被广泛应用于光电器件中,但薄膜的厚度对器件的性能有重要影响。针对此问题采用等离子体化学气相沉积技术,以高纯NH₃、N₂和SiH₄为反应气体,优化其他沉积参数,通过改变沉积时间来生长SiN_x薄膜。用X射线衍射谱(XRD),紫外-可见光光谱(UV-VIS)、傅里叶变换红外光谱(FTIR)和扫描电镜(SEM)对薄膜结构进行表征,详细研究了沉积时间与薄膜厚度的关系以及沉积时间对薄膜性能的影响。试验结果表明:所制备的样品为非晶SiN_x薄膜结构,薄膜厚度随沉积时间均匀增加;薄膜折射率随沉积时间的增加而增大,光学带隙基本不随时间变化。SEM测试结果表明,随着沉积时间增加,薄膜致密性与均匀性越来越好,氧含量也越来越少,说明薄膜致密性提高可以有效阻挡O原子进入薄膜,阻止后氧化现象的发生。     

Fe/SiO2核壳复合粒子表面的XPS谱研究

采用XPS技术研究了Fe/SiO2核壳复合粒子的表面化学成分和电子结构。结果表明,表面化学成分仅由Si和O元素组成,表面Si存在4种电子结构,表面O存在5种电子结构。表面硅4种电子结构的Si2p电子结合能及归属为:102.91eV(51.18%)为Q4硅[Si(OSi)4],102.15eV(23.23%)为Q3硅[Si(OSi)3OH],103.98eV(18.70%)为Q2硅[Si(OSi)2(OH)2],101.35eV(6.89%)为Q1硅[Si(OSi)(OH)3];表面氧5种电子结构的O1s电子结合能及归属为:532.85eV(52.07%)为Q4硅基团中的氧,531.80eV(19.93%)为Q3硅基团中的氧,533.90eV(17.09%)为Q2硅基团中的氧,534.75eV(7.65%)为Q1硅基团中的氧,530.55eV(3.26%)为与金属铁核相互作用的氧。531.80和530.55eV的氧原子数(19.93% 3.26%=23.19%)与102.15eV的硅原子数(23.23%)非常相近,这不仅表明与金属铁核相互作用的表面氧为Q3硅基团中的氧,而且说明表面氧与金属铁核相互作用后O1s电子结合能会因为Fe给电子能力较大而降低。     

Ordered mesoporous aluminosilicates with very low Si/Al ratio and stable tetrahedral aluminum sites for catalysis

New and ordered 2D-hexagonal (p6mm) mesoporous aluminosilicates (CMI-11) have been synthesized in strongly alkaline media using aluminosilicate ester ((Bu^sO)₂-Al-O-Si-(OEt)₃) as single-source molecular precursor and CTMABr as surfactant and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption–desorption and ²⁷Al and ²⁹Si MAS NMR spectroscopy. These mesoproous aluminosilicates exhibit a very low Si/Al ratio of 1.9 and highly thermal stable tetrahedral aluminum sites in the mesoporous walls. ²⁷Al and ²⁹Si MAS NMR spectroscopy indicates that the pore walls of CMI-11 are fully condensed with molecular homogeneity of Si–O–Al linkage. These materials are highly important in catalysis, in particular for the petroleum processing and the bulky molecules treatment.     

Structure and Luminescence Properties of Eu<Superscript>3+</Superscript>-Doped Cubic Mesoporous Silica Thin Films

Eu³⁺ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol–gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu³⁺ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of ⁵D₀-⁷F₁ and ⁵D₀-⁷F₂ of Eu³⁺ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu³⁺ ions-doped mesoporous silica thin films increases linearly with increasing Eu³⁺ concentration.     

Hexagonal Mesoporous Silica with Noodle-Like Shape

Hexagonal mesoporous silica (HMS) was prepared at ambient temperature by using dodecylamine (DDA) as the surfactant and tetraethyl orthosilicate (TEOS) as the silica precursor. The HMS materials were characterized by X-ray powder diffraction, N₂ adsorption/desorption, scanning electron microscopy and transmission electron microscopy. The samples prepared at various addition rates of TEOS and various alcohol/water (R/H) ratios were investigated. As the addition rate of TEOS decreased, the size of HMS particles increased and the textural porosity decreased. Non-alcoholic solution was required to prepare non-spherical particles. The HMS with noodle-like structures was prepared in the absence of alcoholic solvent. These noodle-like particles were about 0.1m in diameter and about submicrometer to several micrometers in length.     

Preparation of spherical MCM-41 molecular sieve at room temperature: Influence of the synthesis conditions in the structural properties

A rapid and facile synthesis route to obtain mesoporous MCM-41 silica at room temperature under basic conditions using as template cetyltrimethylammonium bromide (CTAB) is reported. The synthesis variables such as reaction time, molar ratios of CTAB/TEOS and H₂O/ethanol in the initial gel composition were studied. Samples were characterized by X-ray diffraction, nitrogen adsorption–desorption analyses, scanning electron microscopy and transmission electron microscopy. It was found that reaction conditions affect the quality of the MCM-41 silica. This silica can be prepared at short periods of time, and it exhibited a uniform size and spherical morphology.     

单分散大粒径介孔二氧化硅微球的制备及表征

以正硅酸四乙酯(TEOS)为硅源、N,N-二甲基甲酰胺(DMF)为乳化致孔剂,采用酸催化法得到部分缩合的聚硅酸乙酯(PES),再经碱进一步催化得到介孔二氧化硅微球。分析了酸催化剂用量、旋蒸温度对PES粘度及聚合程度的影响以及PES粘度对二氧化硅微球粒径的影响,并研究了氨水用量、乳化致孔剂种类、乳化致孔剂用量以及搅拌速度和后处理方式对二氧化硅微球性质的影响。利用扫描电子显微镜、旋转粘度计、氮吹吸附仪、傅里叶变换红外光谱仪等对所得微球进行表征。结果表明,所制备的介孔二氧化硅微球球形完整,粒径分布均匀,纯度高,微球平均孔径为10.164 4 nm,孔体积为1.023 023 cm³/g,比表面积为396.528 1 m²/g。     

石墨/TinO2n-1复合材料的制备及性能

在常压下,以钛白粉为原料,石墨为还原剂,采用碳热还原法制备了石墨/Ti_nO_2n-1复合材料。采用XRD系统分析了碳热还原过程中钛的价态变化规律;采用XPS、SEM、TEM分析了特定样品的形貌、结构和元素组成。XRD分析结果表明,控制不同的还原条件,可以得到不同n值的石墨/Ti_nO_2n-1复合材料,且还原过程的物相转变顺序为：TiO₂（锐钛型）、TiO₂（金红石型）、Ti₉O₁₇、Ti₈O₁₅、Ti₆O₁₁、Ti₅O₉和Ti₄O₇。在还原温度为1250℃,还原时间为20min,碳钛比为5∶10的条件下所制备的石墨/Ti_nO_2n-1复合材料的电阻率最低,其值为0.1465Ω·cm。吸附/光降解实验表明,石墨/Ti_nO_2n-1复合材料对亚甲基蓝的吸附能力比纯石墨显著增强,吸附去除率为纯石墨的1.40~3.20倍;石墨/Ti_nO_2n-1复合材料对亚甲基蓝具有光催化降解活性,但是其光降解能力低于锐钛型TiO₂;复合材料的催化降解速率常数最大值为0.0047min^-1。     

溶胶-凝胶法制备γ-缩水甘油醚丙基三甲氧基硅烷/正硅酸乙酯杂化材料研究

采用溶胶-凝胶工艺制备γ-缩水甘油醚丙基三甲氧基硅烷/正硅酸乙酯(GPTMS/TEOS)杂化材料,采用正交实验法对H2O与S i的摩尔比、GPTMS与TEOS摩尔比、水解时间等影响材料性能的因素进行了优化,用热失重(TGA)和动电位扫描法研究分析了该材料的结构、耐热及防腐保护性能。结果表明:当GPTMS∶TEOS=1∶3(摩尔比),H2O∶S i=11.25∶1(摩尔比)时,该材料的耐热性及防腐保护性能最优,X射线衍射分析表明,该材料结构为非晶态结构。     

Controlling the textural parameters of mesoporous carbon materials

The mesoporous carbon materials prepared by inorganic templating technique using mesoporous silica, SBA-15 as a template and sucrose as a carbon source, have been systematically investigated as a function of sucrose to mesoporous silica composition, with a special focus on controlling the mesoporous structure, surface morphology and the textural parameters such as specific surface area, specific pore volume and pore size distribution. All the materials have been unambiguously characterized by XRD, N₂ adsorption–desorption isotherms, high-resolution transmission electron microscopy, high-resolution field emission scanning electron microscopy, and Raman spectroscopy. It has been found that the porous structure, morphology and the textural parameters of the mesoporous carbons materials, CMK-3-x where x represent the sucrose to silica weight ratio, can be easily controlled by the simple adjustment of concentration of sucrose molecules. It has also been found that the specific surface area of the mesoporous carbon materials systematically increases with decreasing the sucrose to silica weight ratio. Moreover, the specific pore volume of the materials increases from 0.57 to 1.31 cm³/g with decreasing the sucrose to silica weight ratio from 5 to 1.25 and then decreases to 1.23 cm³/g for CMK-3-0.8. HRTEM and HR-FESEM also show a highly ordered pore structure and better surface morphology for CMK-3-1.25 as compared to other materials prepared in this study. Thus, it can be concluded that the sucrose to silica weight ratio of 1.25 is the best condition to prepare well ordered mesoporous carbon materials with good textural parameters, pore structure and narrow pore size distribution.     

Preparation of Spherical Hexagonal Mesoporous Silica

A series of hexagonal mesoporous silica (HMS) have been synthesized by the neutral assemble pathway in water-alcohol cosolvent systems, using dodecylamine (DDA) and tetraethyl orthosilicate (TEOS) as the starting materials. These materials were characterized with powder X-ray diffraction, nitrogen sorption measurement, differential thermal analysis, and transmission electron microscopy. The XRD patterns of these samples exhibited a strong intense reflection at low angle, suggesting the excellent mesostructures of the samples. The particle size of HMS decreased and the morphology of HMS exhibited high textural porosity as the HMS was prepared with high addition rate of TEOS. The particle size of HMS prepared without aging was smaller than that aged for 18 h, due to the reaction time of TEOS was not enough to form complete particles. Addition of NaCl and HCl hindered the formation of HMS mesoporous structure. In contrast, addition of 1-butanol did not affect the formation of HMS mesoporous structure. The sphereical HMS silica with uniform size has been synthesized by adjusting DDA and TEOS concentrations. The shape of HMS became larger and more spherical as the concentrate on of DDA decreased. The stirring rate of the reaction mixture had no effect on either the shape or the size of the spheroid HMS silicas. However, the particles started to crack at higher stirring rates.     

Effect of Composition on Crystallization of Y/Yb–Si–Al–O–N B-Phase Glasses

The effect of a partial or full replacement of yttrium by ytterbium on the crystallization of an oxynitride B-phase parent glass with composition (e/o) 35Y/Yb:45Si:20Al:83O:17N has been investigated by thermal analysis, X-ray diffractometry and analytical transmission electron microscopy. Single B-phase formation was extended to higher temperatures by low ytterbium:yttrium ratios, while a full replacement resulted in a two-phase B- and J-phase glass–ceramic. The B-phase crystals took up a substantial range of composition that was dependent on the substitution level, and yttrium/ytterbium was always clearly anti-correlated with silicon. Some aluminum was accommodated in the dendritic J-phase crystals, and their yttrium/ytterbium content varied between 64 and 79 cation%.     

Mesostructured SiO2-doped TiO2 with enhanced thermal stability prepared by a soft-templating sol–gel route

Mesostructured SiO₂–TiO₂ mixed oxides have been prepared by a soft-templating sol–gel route, using a non-ionic triblock copolymer as structure-directing agent. Tetraethylorthosilicate (TEOS) and titanium tetraisopropoxide (TTIP) have been employed as Si and Ti sources, respectively. Using a prehydrolysis TEOS step allows mixed oxides to be produced with a homogeneous porosity and with no phase segregation, in a wide range of Si/Ti compositions. Both the hydrolysis molar ratio and the silicon content have been found to be important factors determining the final properties of these materials. For instance, mixed oxides containing low silicon concentrations exhibit N₂ physisorption isotherms typical of mesoporous materials, although with an important contribution of microporosity. On the other hand, increasing the hydrolysis molar ratio makes more difficult to reach a total dispersion of SiO₂ through the TiO₂ matrix. Even with low SiO₂ loadings, the thermal stability is effectively enhanced, when compared to the equivalent pure TiO₂ materials, as a consequence of a delay in the titania crystallization to anatase. Thus, after calcination at 300 °C for 3 h, mixed oxides containing low Si/Ti ratios (20/80) show BET surface area in the range 290–346 m²/g, while pure TiO₂ materials largely collapse under the same treatment and their BET surface area drop strongly to values around 125 m²/g. This synthesis route, therefore, provides mesoporous TiO₂-rich materials with enhanced stability and textural properties, which is of high interest for applications as catalysts and supports.