Carbon fibers temperature effect

Temperature is one of the processing parameters which has a pronounced effect on the failure strength of carbon fibers. This effect is quite different for MP based and PAN based fibers. As the heat treatment temperature (HTT) is raised, the strength of a mesopitch based fiber, tested at room temperature, progressively increases [3] [38] [54-55]. Conversely, that of most PAN based fibers undergo a maximum at about 1300-1500 C (Figure 12). 

Figure 5.46 Apparent crystallite size against heat treatment temperatures for three levels of stress. Source Reprinted with permission from Ozbek S, Isaac DH, Carbon fiber processing Effects of hot stretching on mechanical properties. Mater Manuf Process, 9(2), 179-197, 1994. Copyright 1994, CRC Press, Boca Raton, Florida.

Carbon—carbon composites are used in high temperature service for aerospace and aircraft appHcations as weU as for corrosion-resistant industrial pipes and housings. AppHcations include rocket nozzles and cases, aircraft brakes, and sateUite stmctures. Carbonized phenoHc resin with graphite fiber functioned effectively as the ablative shield in orbital re-entry vehicles for many years (92). 

Table 2. Effect of Peak Carbonization Temperature on PAN Carbon Fiber Composition, wt %...

Dinwiddie, R.B., Nelson, G.E., and Weaver, C.E., The effect of sub-minute high temperature heat treatments on the thermal conductivity of carbon-bonded carbon fiber (CBCF) insulation. In Proc. Thermal Conductivity 23, ed. K.E. Wilkes, R.B. Dinwiddie and R.S. Graves, Technomic Pub. Co., Inc., Lancaster, PA, 1996, pp. 466 477. 

C. H. Liu, T. H. Ko, and Y. K. Liao. Effect of carbon black concentration in carbon fiber paper on the performance of low-temperature proton exchange membrane fuel cells. Journal of Power Sources 178 (2008) 80-85. 

In the case of intercalation reactions, the nanotexture of the host carbon materials has a strong effect. The intercalation of sulfuric acid into natural graphite can proceed at room temperature in concentrated sulfuric acid with a small amount of oxidant, such as nitric acid. The resulting intercalation compound is commonly used in industry for the preparation of exfoliated graphite [32], However, in order to intercalate sulfuric acid into carbon fibers, electrolysis is needed [145,146], Potassium as a vapor, on the other hand, can be easily intercalated in various carbon materials, even in low-temperature-treated carbon fibers [147],... 

The general effect of most fillers is to reduce the coefficient of thermal expansion of the cured epoxy resin in proportion to the degree of filler loading. Certain fillers, such as zirconium silicate and carbon fiber, have a negative coefficient of thermal expansion. These are very effective in lowering the expansion rate of the epoxy, especially at elevated temperatures. 

In order to study the effect of physical aging on the carbon-fiber reinforced epoxy, the freshly quenched materials were then sub-Tg annealed at 140 °C. After annealing for only 10 minutes at that temperature, the toughness of the composite was restored to a level comparable to that of the postcured material (see Fig. 7). It is likely that residual thermal stresses resulted from the quenching were annealed away during this 10 minutes thermal aging at 140 °C. 

On the other hands, it becomes obvious that SOx and NOx in flue gas can be removed at room temperature by using active carbon fibers (ACF) subjected to surface treatment such as heat treatment [1, 2], The flue gas treatment technology using ACF is a semidry oxidation type de-SOx method which is effective even around room temperature. In addition, this technology enables by-products such as sulfuric acid, sulfates, nitric acid, and various nitrates to be recovered, and is applicable in the field of flue gas treatment to which the conventional de-SOx method, such as the limestone gypsum method, could not be applied for economical reasons. 

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