Surface chemical properties thermal treatment effect

The establishment of relationships between the surface chemistry and the surface free energy of silicas is important for practical applications of these materials. Inverse gas chromatography, either at infinite dilution or finite concentration, appears to be an effective method for the detection of changes of surface properties induced by chemical or thermal treatments. Silicas of various origins (amorphous or crystalline) with surface chemistries modified by chemical (esterification) or heat treatment were compared. The consequences of these modifications on surface energetic heterogeneities were assessed. 

Effect of Thermal Treatment of Carbon on Its Chemical Surface Properties as Determined by an Electrochemical Method3... 

Y. Xiao, L. Shao, T.-S. Chung, D. A. Schiraldi, Effects of thermal treatments and dendrimers chemical structures on the properties of highly surface cross-linked polyimide films, Ind Eng. Chem. Res., 44, 3059-3067 (2005). 

A custom-built dip-coating machine was used for PFPE coating onto SAM-modified and unmodified Si surfaces. A concentration of 0.2 wt% of PFPE was used. The sample was dipped in the PFPE solution and held for 1 min and withdrawn at a constant speed of 2.1 mm s". Tribological tests were carried out almost immediately after PFPE coating to eliminate any effect of aging at room temperature. The PFPE coated samples were heated at 150°C for 2 h in vacuum and were used for studying the effect of thermal treatment on the physical, chemical, and tribological properties. 

All natural fibers are hydrophihc and their moisture content ranges from 3 to 13%. This leads to a very poor interface between natural fiber and the hydrophobic matrix and very poor moisture resistance. Several fiber surface treatments are used to improve the interface viz-thermal treatment, chemical treatment, and use of coupling agents (Bledzki and Gassan, 1999). Fillers are added to composites for technical and chemical reasons (Milewski and Katz, 1980). Calcium carbonate has maximum usage as filler in plastics and FRP due to its low cost, non-toxicity and lack of odor. Present work gives effectiveness of jute fabric treatment and addition of filler on properties of jute reinforced polyester composites (JFRP). 

In this paper, XPS and Raman spectroscopy have been used to study the chemical state and location of Ni and V contaminants. The effects of thermal and hydrothermal treatments on catalyst surface properties, and the role of sepiolite in promoting metals tolerance has been observed and reported. 

It is not within the scope of this chapter to provide a comprehensive discussion of silica gel chemistry. An excellent treatise is available (77). The parameters that most significantly affect bonding chemistries and solute retention properties are surface area, pore volume, pore diameter, trace metal impurities, and thermal pretreatments. Both Sander and Wise (90) and Sands et al. (91) have studied the effect of pore diameter and surface treatment of the silica on bonding reactions. Boudreau and Cooper (92) have studied the effects of thermal pretreatments at 180, 400, and 840°C on the subsequent chemical modification of silica gel, and showed that thermal pretreatment at temperatures >200°C can produce more homogeneous distribution of active silanols which are available for subsequent derivatization. 

With a particular focus on polymers, two important properties of a low-pressure plasma treatment should be emphasized (i) A low-pressure plasma provides high activation energies of several electron volts without elevated temperatures of ions and neutrals (cold plasma). For that reason, there is no thermal load to sensitive polymer materials, while most chemical bonds can be broken and surface radical sites can be formed, (ii) When a polymer is exposed to a low-pressure plasma, the surface modification effect is limited to the uppermost few nanometers (i.e., the range of impinging ions and vacuum ultraviolet photons). Hence, favorable bulk properties of the material remain unchanged. 

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