Gel preparation

Fig. 3.35 Mercury porosimetry intrusion-extrusion plots of alumina gels prepared from solutions of aluminium monohydrate in A, propan-2-ol (2-5w/v%) B, propan-2-ol (4-9w/v%) C, 2-methylpropan-2-ol (4-9 w/v%) D, 2-methylpropan-2-ol (9-5 w/v%) E,butan-2-ol (9-5 w/v%). -------, ascending, intrusion curve -----, descending, extrusion curve.

Gel preparation and crystalli2ation is represented schematically using the Na20—AI2O2—SiO2—H2O system as an example (1). 

Copolymers of sodium acrylate with sodium 2-acrylamido-2-methylpropane sulfonate (AMPS) or /V, /V- dim ethyl acryl am i de (52) have been used to prepare cross-linked systems at high temperatures and salinity. Chromium cross-linked gels, prepared from a 3 1 blend of partially hydrolyzed... 

To produce the titanium white mtile pigment, the hydrated Ti02 gel prepared in the presence of mtile seeds is calcined at temperatures of 900—930°C. This temperature is quite important because pigments having a particle size of 200—400 nm are produced at these temperatures. When the calcination is carried out at temperatures above 950°C, the particles of Ti02 become considerably larger and do not have optimum pigmentary properties. 

Si02 Na. Lower concentrations of silicate are used in silica gel preparation. In the absence of a coagulant, silica is not precipitated from solution at any pH... 

I. E. Neimark and R. Y. Sbeinfain, Silica Gel Preparation, Properties and Uses, Nauk Dumka, Kiev, CIS, 1973. 

The family of agarose-based gels, Sepharose, Sepharose CL, and Sepharose Fast Flow, are bead-formed gels prepared from 2, 4, or 6% agarose solutions. The matrix porosity decreases and rigidity of the bead structure increases with increasing agarose concentrations. The open pore structure and broad... 

When purchasing GPC/SEC columns it is imperative to realize that no manufacturer has a technical edge on another. The products are analogous, with the primary difference being price. When one buys a GPC/SEC column, it is the service of gel preparation and column packing that is really purchased. We have provided the formulae and directions for the preparation of GPC gels because we do not want our customers to pay for a service that they themselves can do for less. 

Pyridinium / -toluenesulfonate, 5°, 1 h." Similar selectivity can be achieved using a silica-alumina gel prepared by the solgel method. ... 

R. Azzam, Sandy Soil Plantation in Semi Arid Zones by Polyacrylamide Gel Preparation by Ionizing Radiation, lAEA-Contract No. 2596/RB, Progress Rpt July 1980-Oct. 1981, Vienna. 

In order to locate Ti02 mainly at the exterior surftice in the vicinity of macropores of the activated carbon, a modified sol-gel preparation method was employed. 

Fig. 137.—Equilibrium swelling ratio qm of poly-(methacrylic acid) gels prepared by copolymerizing methacrylic acid with 1, 2, and 4 percent (upper, middle, and lower curves, respectively) of divinylbenzene plotted against degree of neutralization i with sodium hydroxide. (Katchalsky, Lifson, and Eisenberg. )...

Transition-metal mixed oxides active in combustion catalysis have been prepared by two main procedures i) classical coprecipitation / calcination procedures starting from metal nitrates and/ or alkoxides ii) preparation based on the supercritical drying of gels prepared from organic complexes (alkoxides, acetylacetonates or acetates), producing aerogels . Details on the second preparation can be found in Ref. 13. 

R. D. Sydansk. Hydrocarbon recovery process utilizing a gel prepared from a polymer and a preformed crosslinking agent. Patent US 5415229,1995. 

A typical regimen for benzoyl peroxide use is to apply the product to clean, dry skin no more than two times a day. The strength and dosage form selected may vary from patient to patient depending on acne severity and the sensitivity of the patient s skin. Since gel preparations are the most potent dosage form, patients with dry or overly sensitive skin should... 

Figure 2. Linear shrinkage versus temperature at l°C/min heating rate for silica gels prepared by three different methods a) two-step acid hydrolysis, b) two-step base hydrolysis, c) colloidal process. (Reproduced with permission from Ref. 4. Copyright 1984 Wiley- Interscience.)...

Solid state MASS 29Si NMR spectra of dried gels prepared with 4 equivalents of water show a similar trend. QJ-Q4 species are evident in gels prepared under neutral conditions (41), whereas under more basic conditions, Q1 species are absent and Q2 species are greatly reduced relative to Q4 (see NMR results presented below). Thus the effects of restructuring are preserved in the fully dried gel. 

Chromium crosslinked gels prepared from a 3 1 blend of partially hydrolyzed polyacrylamide and guar gum have been found to have a higher strength and stability than gels prepared from the partially hydrolyzed polyacrylamide alone (222). 

Kesmez, O., Erdem Camurlu, H., Burunkaya, E. and Arpac, E. (2009) Sol-gel preparation and characterization of anti-reflective and self-cleaning Si02-Ti02 double-layer nanometric films. Solar Energy Materials and Solar Cells, 93, 1833-1839. 

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