Surface modification whiskers

The type and degree of these interactions affect Si3N4-SiC interfaces through modification of whisker surfaces and changes in the thickness and crystallinity of the interfacial layer. 

The ideal conditions of whisker-reinforced resin are as follows whiskers are dispersed evenly in a matrix, separated from each other, and are well wetted by matrix resin. Surface modification of whiskers is needed to improve the dispersion... 

In the in situ polymerization method, first inorganic whiskers are evenly dispersed in monomers and then polymerized using a method similar to bulk polymerization. In this method, surface modification of whiskers and preparation of composites take place at the same time. 

Surface modification of fibrils reported in the literature are mainly hydrophobica-tion reactions aimed at compatibilization with nonpolar polymer matrices. Hence, much of the work concerns modification of whiskers that are easier to mix into composites than MFC. However, methods for introduction of specific functionalities, as part of other applications of MFC, have also been reported. 

Surface modification reactions OTC (GC) 139 etching HCl i O leaching HCl 140 particle depcaition 143 whisker formation 142 Surfactant mobile phases (LC) 408... 

Surface modification reactions are used to improve the wettability of glass surfaces by polar stationary phases and to Improve the extent of deactivation by sllylation" [138-146,166]. Miaaiuua procedures have been investigated but only a few are in use. Of these, the most important reactions are etching by hydrogen chloride, leaching with aqueous hydrochloric acid, formation of whiskers and solution deposition of a layer of solid particles. Because of the high purity and thinness of the... 

Capillary Modification. The capillary was etched with a fluoride compound at high temperature to prepare a whisker column with a 1000-fold increased inner surface area as compared to an unmodified capillary... 

Interactions between CNRs and hydrophilic matrices are usually satisfactory [119] due to the presence of the hydrophilic cellulose surface. The simplest technique to process a nanocomposite material is using water suspensions of whiskers because of their high stabihty and the expected high level of dispersion of the whiskers within the host matrix in the resulting films. But this technique is mostly restricted to hydrophilic polymeric material. Another alternative to processing nanocomposites using whiskers is the addition of surfactants and chemical modification of the whiskers by substistuents so that they will be compatible in hydrophobic matrix [120,121]. Some chemical modifications of the surface of cellulose whiskers that increase its hydrophobicity include surface acylation [122] and... 

Nanometric monocrystals of chitin, commonly referred to as whiskers, are prepared by acid hydrolysis of chitin obtained from various sources such as squid pen chitin, riftia tubes, crab shells and shrimp shells. The surface of crab shell whiskers was chemically modified with alkenyl succinic anhydride (ASA) and phenyl isocyanate (PI). TEM images in Figure 14.3 show that after surface chemical modification the chitin fragments seem to be entangled, and individual whiskers are difficult to observe. 

Cellulose whiskers without surface modification display strong interactions and have been reported as difficult to disperse in water. Sulfate-functionalized tunicate whiskers were prepared by sulfuric acid hydrolysis of cellulose pulp derived from tunicates (StyelacldVa). These high aspect ratio nanoparticles formed colloidal suspensions in water (Figure 14.4). A stable suspension of tunicin whiskers was obtained in an organic solvent (Af,Af-dimethylformamide) without surfactant addition or chemical surface modification. Both the high value of the dielectric constant of DMF and the medium wettability of tunicin whiskers were supposed to control the stability of the suspension (Figure 14.5). 

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