Inorganic Precipitated Silica Gel. Part 1: Gelation Kinetics and Gel Properties

Precipitated silica (SiO₂) is industrially produced by mixing a silicate solution with acid in a semi‐batch process. Polycondensation of monomeric silica leads to the formation of particles which aggregate and eventually form a particulate gel. However, this is instantly fragmented by the mechanical energy input caused by the stirrer. Shrinkage and compaction of these fragments lead to the final product aggregates. It is the aim of this study to enable tailoring of the structure and size of these product particles via the process parameters. The present paper describes the influence of the parameters temperature, ionic strength, and composition, which affect the pH, on the properties of unstirred gels regarding their elasticity and thus their fragmentation behavior. Gelation time may be qualitatively estimated solely from the concentration of the feed materials.     

硅胶固载硫酸钛催化合成对羟基苯甲酸乙酯

以硅胶固载硫酸钛（Ti(SO4)2/SiO2）催化合成对羟基苯甲酸乙酯，考察了催化剂活性及最佳工艺条件。Ti(SO4)2在硅胶载体上的合适负载量为20％，对羟基苯甲酸用量0.1mol，适宜的醇酸摩尔比为3：1，固载催化剂用量为1.2g，115℃下回流反应3h，酯化率达91.6%。     

大孔容高比表面积硅胶的制备

采用硅酸钠和硫酸为原料,无水乙醇为交换剂,通过微波干燥制备大孔容高比表面积硅胶。研究了醇泡浴比、醇泡时间、微波干燥强度、微波干燥时间对硅胶孔径、孔容和比表面积的影响。研究结果表明,在醇泡浴比为2.5∶1.0,醇泡时间为30h,微波强度为550W,微波干燥时间为20min时可制备大孔容高比表面积的硅胶。     

沉淀法二氧化硅塑料薄膜开口剂的研制

以水玻璃和硫酸为原料采用沉淀法合成了二氧化硅塑料薄膜开口剂.在单因素实验的基础上,通过正交实验考查了添加剂浓度、硫酸浓度、反应温度、硫酸滴加速度对产物性能的影响.实验结果表明:当添加剂摩尔浓度为0.75 mol/L,硫酸滴加速度为0.25 mL/s,反应温度为70 ℃.硫酸摩尔浓度为0.5 mol/L.时得到的二氧化硅塑料薄膜开口剂性能较佳,其邻苯二甲酸二丁酯(DBP)吸收值为1.600 7 mL/g.通过红外光谱表征得出产物各特征峰与二氧化硅的标准谱图相符,SEM和X射线衍射表征证明所得产物为无定型二氧化硅,平均粒径约10μm.     

Intermolecular Dearomatization Reaction of Pyrroles Promoted by Silica Gel

An efficient synthesis of polysubstituted 2H‐pyrrole derivatives via a silica gel‐promoted intermolecular dearomative Michael addition of pyrroles with α,β‐unsaturated ketones has been developed. This transformation features environmentally benign promoter, high efficiency, wide substrate scope and mild reaction conditions.

     

硅胶柱层析法提纯大豆磷脂酰胆碱的研究

探讨了以大豆浓缩磷脂为原料,应用柱层析法提纯大豆磷脂酰胆碱(PC)的工艺过程.用TLC法考察了水、异丙醇与正己烷的体积配比,确定流动相适宜配比为正己烷:异丙醇:水(1:1:0.175,v/v/v).通过对固定相、流动相和上载量的考察,得到了柱层析最佳工艺条件:在空塔流速为0.382 cm·min-1,进样浓度为0.25 g浓缩磷脂·(mL流动相)-1的室温条件下,固定相选用100～200目粗孔2号硅胶,流动相为正己烷:异丙醇:水(1:1:0.16,v/v/v),最适上载量为0.086gPC·(g硅胶)-1.经高效液相色谱法定量分析,产品中磷脂酰胆碱纯度高达85%.     

Sol—Gel法制备有机—无机复合光致变色膜

本文讨论了用ｓｏｌ－ｇｅｌ法在有机改性ＳｉＯ２基体中于室温下俘陷有机染料如螺吡喃或螺恶嗪，制备出具有光致变色功能的有机－无机复合膜。该膜层在可见光区的最大吸收峰位于６２０ｍｎ处。     

硅胶固载γ-氯丙基三甲氧基硅烷制备水不溶性杀菌剂中间体

采用硅胶作为水不溶性杀菌剂的载体 ;以γ 氯丙基三甲氧基硅烷作为联接硅胶和杀菌活性官能团的偶联剂 ;在硅胶上键合γ 氯丙基三甲氧基硅烷的最佳反应条件为 :使用二甲苯作反应溶剂 ,80℃反应 6h以上 ,原料硅胶最好要经丙酮处理 ,γ 氯丙基三甲氧基硅烷与硅胶的质量比为 1∶1即可。使用所研制的中间体制备的水不溶性杀菌剂用量 2mg mL时杀菌率达到 98%。     

正交试验优选硅胶洗涤工艺

用正交试验法对硅胶洗涤的工艺进行优选,以杂质洗涤率为指标,选用L9(34)正交试验表进行正交试验。结果表明:硅胶洗涤的最佳工艺条件为液固比(V水∶m硅胶)=3∶1、洗涤温度70℃、洗涤时间2 h,搅拌速率200 r/min。在此条件下洗涤2次,硅胶中95%以上的水溶性杂质被除去。     

Vickers Crack Nucleation of Glass Sheets Coated by Thin Silica Gel Layers

SiO₂ gel layers of different thickness have been deposited on glass sheets by dipping from gelling solutions with different concentrations of silicon alkoxide. Some mechanical properties of the coated samples such as hardness (H), elastic modulus (E), crack formation tendency, and tensile stress in the film (σ) have been measured by microindentation techniques and slide deflection. SiO₂ films deposited from more dilute solutions had lower H, E, and σ values, accounting for the observed higher resistance to crack nucleation in comparison with that found for samples prepared from more concentrated solutions.     

硅胶固载对甲苯磺酸催化合成肉桂酸正丁酯

研究了用硅胶固载对甲苯磺酸作催化剂催化合成肉桂酸正丁酯。获得了最佳反应条件 :肉桂酸用量为 0 .0 2mol,肉桂酸与正丁醇物质的量比为 1:2 .5 ,催化剂 1.5g ,反应时间 45min ,在此条件下酯化率可达 99.5 0 %。     

硅胶负载钨钼杂多酸催化合成聚缩季戊四醇乙二醛

以硅胶负载钨钼杂多酸为催化剂,乙二醛与季戊四醇为原料,合成了聚缩季戊四醇乙二醛,系统地研究了乙二醛与季戊四醇的摩尔比、催化剂用量、反应时间诸因素对收率的影响。结果表明：在n（醛）：n（季戊四醇）=1：18,催化剂的用量占反应物料总质量的1．5％,反应时间为2．5h条件下,聚缩季戊四醇乙二醛平均收率在67％。     

Preparation of Small-Particle-Size, Semiconductor CdS-Doped Silica Glasses by the Sol–Gel Process

The sol–gel process has been applied successfully to the preparation of small-particle-size CdS-doped silica glasses with a significant quantum size effect. Gels prepared through the hydrolysis of a complex solution of Si(OC₂H₅)₄ and Cd(CH₃COO)₂·2H₂O were heated at 500°C, then reacted with H₂S gas to form fine, hexagonal, CdS-microcrystal-doped glasses. The optical absorption edge is blue shifted by ∼0.4 eV compared with the bulk absorption value of CdS crystal. This result is interpreted in terms of a quantum-confinement effect of small crystal size.     

Synthesis of Silica Nanoparticles by Ultrasound‐Assisted Sol‐Gel Method: Optimized by Taguchi Robust Design

Silica nanoparticles were prepared by ultrasound‐assisted and conventional sol‐gel method. The synthesis procedures were designed and optimized by the Taguchi experimental design method. Molar concentrations of TEOS, H₂O, NH₄OH, and reaction temperature were chosen as main factors. The results showed that the molar concentration of ammonia is the main factor which affects the particle size of the silica nanoparticles. The chemical structure, size, and morphology of the product were investigated by X‐ray diffraction, Fourier transform infrared spectroscopy, laser light scattering, and scanning electron microscopy. By the optimum conditions of the ultrasound‐assisted sol‐gel method, silica nanoparticles with an average particle size of 13 nm were prepared.     

固体酸催化剂Ga2(SO4)3/硅胶催化合成尼泊金庚酯

采用自制的固体酸催化剂硅胶固载硫酸镓非均相催化合成了防腐剂尼泊金庚酯,考察了催化剂用量、醇酸物质的量比、回流反应时间、带水剂种类及催化剂重复使用性等因素对酯收率的影响.适宜反应条件为:对羟基苯甲酸0.05 mol,醇酸物质的量比5∶1,催化剂2.0g,环己烷10mL,反应时间5h,尼泊金庚酯收率达94.7％.该催化剂活...     

硅胶柱层析法分离提纯双基药中的硝化甘油

探讨了以双基药为原料,采用柱层析法分离提纯来获取少量硝化甘油的工艺方法。结果表明,以乙醚为提取溶剂、二氯甲烷为流动相,45~75μm的层析用粗孔硅胶为固定相,空塔流速约为0.764 cm/min的条件下进行层析柱分离提纯,可获取克量级的硝化甘油。经高效液相色谱法分析,所得硝化甘油纯度高,未见杂峰。     

Synthesis of Si-N and B-N Preceramic Coatings on Silica Gel by Chemical Surface Coating: A Porosity Study

Silica gel has been modified by successive gas reactions with (SiCl₄-NH₃) and (BCl₃-NH₃) in order to obtain Si-N and B-N preceramic polymers, which are chemically bound to the substrate surface. The effect of the polymer synsthesis on the porosity characteristics of the substrate is determined as a function of the number of applied modification cycles, using N₂ adsorption-desorption isotherms recorded at 77 K. The elemental analysis data in combination with the adsorption isotherms yield a more detailed picture of the density and the homogeneity of the coatings. Using the pore size distributions, the contribution of pore blocking and pore narrowing can be calculated as a function of the amount of reaction cycles. A new calculation method for the pore blocking and pore narrowing, which is not based on any pore shape model, is also presented and compared with the former calculation method.     

CeO_2-Ga_2O_3/硅胶的制备及其催化酯化性能研究

制备了铈改性酯化催化剂CeO2-Ga2O3/硅胶,通过催化丙酸与异丁醇的酯化反应考察了其催化酯化性能,并采用IR分析对催化剂进行了表征。催化剂的适宜制备条件为CeO2∶Ga2O3∶硅胶=2.7∶20∶77.3(质量比),500℃焙烧2h。该催化剂对丙酸异丁酯的合成有良好的催化活性,0.20mol丙酸,催化剂用量1.0g,醇酸物质的量比1.4,反应时间90min,酯化率可达98.4%。     

溶胶-凝胶法制备二氧化钛凝胶的影响因素分析

研究了用溶胶-凝胶法制备二氧化钛溶胶的过程，以钛酸丁酯为前驱物，无水乙醇为溶剂，分析了不同的反应条件对凝胶时间的影响。通过实验得到了制备透明稳定凝胶的条件为：反应温度在20～40℃范围内；pH值为2—5；反应物的配比为：醇／钛酸丁酯（摩尔比）为10，水／钛酸丁酯（摩尔比）为3～4，冰醋酸／钛酸丁酯（摩尔比）为1。     

The Mechanical Behaviour of Polyimide/Copper Laminates Part 2: Peel Energy Measurements

The mechanical peel behaviour of laminates consisting of polyimide films adhered to copper foil using a modified acrylic adhesive has been studied over a wide range of test rates and temperatures. The laminates were prepared from polyimide films which had been subjected to either a “high-thermal history” or a “low-thermal history” treatment during the production of the film. The measured peel energies of the laminates could be superimposed to give a master curve of peel energy versus the reduced rate of peel test, Ra_T , where R is the rate of peel test and a_T is the time-temperature shift factor. The appropriate shift factors were a function of the test temperature and were mainly deduced from tensile tests conducted on the bulk adhesive. The “high-thermal history” laminates gave higher peel energies and the locus of failure of the laminates was mainly by cohesive fracture through the adhesive layer. At low values of log₁₀ Ra_T , i.e. Low rates of peel and high test temperatures, the “low-thermal history” laminates also failed in the adhesive layer and possessed similar peel energies to those measured for the “high-thermal history” laminates. However, at high log₁₀ Ra_T values, the peel energies measured for the “low-thermal history” laminates were lower and showed a wider scatter. These arose from a different locus of failure occurring in these “low-thermal history” laminates when tested under these conditions. Namely, it was found that most of these laminates failed in a weak boundary layer in the outer regions of the “low-thermal history” polyimide film.