Effects of Colloidal Silica Binder on Catalytic Activity and Adhesion of HZSM-5 Coatings for Structured Reactors

HZSM-5 coating using three colloidal silica binders, acidic colloidal silica （ACS）, neutral colloidal silica （NCS） and basic colloidal silica （BCS）, was prepared to study the effect of hinders on their adhesion and catalytic activity. Scanning electron microscopy characterization indicated that the zeolite coating using BCS shows the smoothest surface with higher homogeneity and adherence strength. The specific surface area, relative crystallization and acid site strength of zeolites are also dependent on the binder used. Catalytic cracking of supercritical n- dodecane over the series of zeolite coating with various binders indicated that HZSM-5 coating with BCS exhibits the highest and the most stable catalytic activity compared with other kinds of binders, and also exhibits a stable catalytic activity ascribed to its proper acid property and microstructure.

Three-dimensional Ordered Silica Colloidal Film Self-assembly Deposited on a VerticalSubstrate

A method for preparation of particle crystal film constructed from monodisperse silica colloidal particles in diameter of about 300 nm is reported. The films were prepared from an ethanol suspension by vertical deposition that relies on capillary forces to assemble colloidal crystal particles on a vertical substrate. The 3D ordered films were characterized by transmission spectra and scanning electric microscope (SEM). The effect of evaporation temperature, particle concentration and sintered temperature on the quality of colloidal particle crystal film was investigated.

Subsurface defect characterization and laser-induced damage performance of fused silica optics polished with colloidal silica and ceria

This paper mainly focuses on the influence of colloidal silica polishing on the damage performance of fused silica optics. In this paper, nanometer sized colloidal silica and micron sized ceria are used to polish fused silica optics. The colloidal silica polished samples and ceria polished samples exhibit that the root-mean-squared （RMS） average surface roughness values are 0.7 nm and 1.0 rim, respectively. The subsurface defects and damage performance of the polished optics are analyzed and discussed. It is revealed that colloidal silica polishing will introduce much fewer absorptive con- taminant elements and subsurface damages especially no trailing indentation fracture. The 355-nm laser damage test reveals that each of the fused silica samples polished with colloidal silica has a much higher damage threshold and lower damage density than ceria polished samples. Colloidal silica polishing is potential in manufacturing high power laser optics.

Polydisperse spherical colloidal silica particles：Preparation and application

A new industrial method has been developed to produce polydisperse spherical colloidal silica particles with a very broad particle size,ranging from 20-95 nm.The process uses a reactor in which the original seed solution is heated to 100 ℃,and then active silicic acid and the seed solution are titrated to the reactor continuously with a constant rate.The original seeds and the titrated seeds in the reactor will go through different particle growth cycles to form different particle sizes.Both the particles＇ size distribution and morphology have been characterized by dynamic light scattering（DLS）and the focus ion beam（FIB） system.In addition,the as-prepared polydisperse colloidal silica particle in the application of sapphire wafer＇s chemical mechanical polishing（CMP） process has been tested.The material removal rate（MRR） of this kind of abrasive has been tested and verified to be much faster than traditional monodisperse silica particles.Finally,the mechanism of sapphire CMP process by this kind of polydisperse silica particles has been investigated to explore the reasons for the high polishing rate.

Preparation of Organic/Inorganic Hybrid Polymer Emulsions with High Silicon Content and Sol-gel-derived Thin Films

A novel polymer/SiO2 hybrid emulsion(PAES)was prepared by directly mixing colloidal silica with polyacrylate emulsion(PAE)modified by a saline coupling agent.The sol-gel-derived thin films were obtained by addition of co-solvents into the PAES.The effects ofγ-methacryloxypropyltrimethoxysilane(KH-570)content and co-solvent on the properties of PAES films were investigated.Dynamic laser scattering(DLS)data indicate that the average diameter of PAES(96 nm)is slightly larger than that of PAE(89 nm).Transmission electron microscopy (TEM)photo discloses that colloidal silica particles are dispersed uniformly around polyacrylate particles and some of the colloidal silica particles are adsorbed on the surface of PAE particles.The crosslinking degree data and Fourier transform infrared(FT-IR)spectra confirm that the chemical structure of the PAES is changed to form Si-O-Si-polymer crosslinking networks during the film formation.Atomic force microscope(AFM)photos show the solvent induced sol-gel process of colloidal silica and the Si-based polymer distribution on the film surface of the dried PAES.Thermogravimetric analysis(TGA)curves demonstrate that the PAES films display much better thermal stability than PAE.

Dual template approach for the synthesis of hierarchically mesocellular carbon foams

We demonstrated a simple and effective dual-templating approach for the synthesis of hierarchically mesocellular carbon foams by using nonionic surfactant of sorbitan monooleate and silica colloid particles as sacrificial templates, and resorcinol/ formaldehyde as carbon source. The representative carbon foam has dual mesopore sizes of 4 and 10 nm, and possesses the specific surface area of 580 m^2/g and the total pore volume of 0.80 cm^3/g.

High-quality SiO_2 Colloidal Crystal Fabricated by Controllable Vertical Deposition Method

Monodispersed silica microspheres with diameter of 353nm were assembled into photonic crystal in ethanol colloidal suspensions of varied silica volume fraction at different temperature and humidity by means of controllable vertical deposition method. The surface morphology and optical properties were studied by SEM and UV-Vis-NIR. It was found that the high-quality silica colloidal photonic crystals were obtained from ethanol solutions with environment temperature between 45℃ and 55℃, humidity between 66% and 76%, the volume fraction of microspheres is between 0.8% and 1.5%. The ordered close-packed photonic crystal fabricated by controllable vertical deposition method had the two photonic bandgaps in the visible light band and near infrared band.

Grouting of Waste of the Baikal Pulp and Paper Mill to Reduce the Technogenic Impact to the Baikal Lake Ecosystem

Research is devoted to the problem of recycling waste of the Baikal Pulp and Paper Mill, whose activity has caused serious damage to the ecological environment of Lake Baikal and its environs. Grouting waste production is currently the most effective possible decision to the problem of pollutants, such as sludge-lignin and ash, in water objects and groundwater. The results on the grouting of liquid and solid waste from the Baikal Pulp and Paper Mill, represented by sludge lignin and ash, are presented. Cement, liquid glass, colloidal silica, ammonium persulfate, hydrogen peroxide were used as the main hardeners. Samples were formed by mixing the original waste with astringent. The strength in time, shrinkage, resistance to water were studied. Samples formed on the basis of colloidal silica solution have a maximum uniaxial compressive strength of 0.4 - 0.5 MPa, on the basis of liquid glass—0.2 - 0.3 MPa. Adding fine sand increases the strength by 1.5 - 1.7 times. Samples based on ammonium persulfate and hydrogen peroxide do not have sufficient strength. Adding fine quartz sand increases the strength up to 1.0 - 1.2 MPa.

A novel cleaner for colloidal silica abrasive removal in post-Cu CMP cleaning

A novel cleaning solution, named FA/O alkaline cleaner, was proposed and demonstrated in the removal of colloidal silica abrasives. In order to remove both the chemical and physical absorbed colloidal silica abrasives, an FA/OII chelating agent and non-ionic surfactant were added into the cleaner. By varying the concentration of chelating agent and non-ionic surfactant, a series of experiments were performed to determine the best cleaning results. This paper discusses the mechanism of the removal of colloidal silica abrasives with a FA/O alkaline cleaner. Based on the experiment results, it is concluded that both the FA/OII chelating and non-ionic surfactant could benefit the removal of colloidal silica abrasives. When the concentration of FAJOII chelating agent and FA/O non-ionic surfactant reached the optima value, it was demonstrated that silica abrasives could be removed efficiently by this novel cleaning solution.

Preparation of Ag2O modified silica abrasives and their chemical mechanical polishing performances on sapphire

The chemical mechanical polishing (CMP) process has become a widely accepted global planarization technology.The abrasive material is one of the key elements in CMP.In the presented paper,an Ag-doped colloidal SiO2 abrasive is synthesized by a seed-induced growth method.It is characterized by time-of-flight secondary ion mass spectroscopy and scanning electron microscopy to analyze the composition and morphology.The CMP performance of the Ag-doped colloidal silica abrasives on sapphire substrates is investigated.Experiment results show the material removal rate (MRR) of Ag-doped colloidal silica abrasives is obviously higher than that of pure colloidal silica abrasives under the same testing conditions.The surfaces that are polished by composite colloidal abrasives exhibit lower surface roughness (Ra) than those polished by pure colloidal silica abrasives.Furthermore,the acting mechanism of Ag-doped colloidal SiO2 composite abrasives in sapphire CMP is analyzed by X-ray photoelectron spectroscopy,and analytical results show that element Ag forms Ag2O which acts as a catalyst to promote the chemical effect in CMP and leads to the increasing of MRR.

Synthesis of colloid silica coated with ceria nano-particles with the assistance of PVP

In this paper, a facile synthesis of 100 nm commercial colloid silica coated with nano-ceria core-shell composite particles by the precipitation method using ammonium cerium nitrate and urea as a precipitator with polyvinylpyrrolidone （PVP） as an assistant was briefly introduced. The results showed that the colloid silica was surrounded by nano-ceria uniformly forming the core-shell composite particles. The synthesis process was further discussed and optimized. It was found that the type and quantity of surfactant played a key role in the process. PVP connected the surface of colloid silica and that of the ceria precursor.

Particle Shape Dependence of Rheological Behavior for Colloid-polymer Mixtures

The effect of particle shape on the rheological behavior of small particle-large polymer chain mixture solutions has been investigated with two model colloidal silica dispersions, one of which is ellipsoidal（BINDZIL20/440） and the other is spherical（TM40）. It was found that BINDZIL20/440 series showed shear-thickening at lower shear rates and had a lower upper limit in PEO concentration to demonstrate shear-thickening phenomena. The particle shape was identified as the major factor accounting for these differences. This work enables one to control the rheological behavior of colloid-polymer mixture through simply changing particle geometry instead of performing surface modifications, which could be especially useful in cases where only certain chemicals are allowed, for example in vivo applications.

Synthesis of SiO_2@SiO_2 core-shell microspheres using urea-formaldehyde polymers as the templates for fast separation of small solutes and proteins

Superficially porous core-shell silica microspheres （CSSMs） have been a great success for the fast separation of small molecules and proteins in recent years. In this paper, the CSSMs were synthesized by an improved polymerization-induced colloid aggregation （PICA） method using urea-formaldehyde polymers as the templates. The agglomeration of the functionalized silica core was avoided by the surface modification through reflux with ureidopropyltrimethoxysilane in the neutral ethanol solution at 80 ~C, and the secondary nucleation of the silica nanoparticles during the preparation process could also be inhibited via the optimization of the reaction conditions, such as pH, temperature, colloidal silica sol concentration and the reaction time. The controllable shell thickness and pore size of the synthesized monodisperse CSSMs were successfully obtained by adjusting the weight ratio of silica core/colloidal silica sol and the particle size of colloidal silica sol, respectively. The C18-modified CSSMs with different pore sizes were used to separate small solutes and proteins. The higher efficient separation and relatively low back pressure of the synthesized core-shefi column demonstrate that the CSSMs have a great ootential aoolication for fast HPLC

Effect of anions from calcium sources on the synthesis of nano-sized xonotlite fibers

The xonotlite fibers were synthesized via the hydrothermal synthesis method with CaO and SiO_2 as the raw materials and the molar ratio of Si/Ca of 1.0. Effect of anions from various calcium sources on the microstructure of the xonotlite fibers is studied in this paper. These obtained products were characterized by X-ray diffraction(XRD), transmission electron microscope(TEM) and scanning electron microscope(SEM) techniques to investigate their crystalline phase, crystal structure and morphology. The results indicate that anion from various calcium sources has little influence on the crystalline phases of xonotlite fibers but poses a great impact on their morphologies. Xonotlite fibers with single crystal characteristics and large aspect ratio of 50—100 were successfully fabricated from CaCl_2 as calcium material at 225 °C for 15 h. The existence of Cl-anion in the CaO-SiO_2-H_2O system significantly contributes to the formation of xonotlite crystal.