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DESIGN, ASSEMBLY AND CHARACTERIZATION OF COMPOSITE ...

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content in Ni powder is unchanged in this process, which is unlikely, the total carbon<br />

content after thermal degradation will be 0.364% by weight or less.<br />

The different thermal degradation kinetics of three polymers may be ascribed to<br />

the differences in their molecular structures and covalent bonds: PEI is highly branched<br />

containing C-C and C-N bonds; PAA has a carbon chain backbone with -COOH<br />

functional group, and HPMC is a cellulose derivative, i.e., modified polymerized glucose<br />

rings, containing C-O and C-C bonds. The C=O and C-O bonds requires lower thermal<br />

energy to break than C-C and C-N. 157 Also, these polymer additives are coated on nickel<br />

particle surface during actual binder removal, NiO may have a catalytic effect to the<br />

thermal degradation of these polymers. But these two aspects are not investigated further<br />

due to the negligible amount of residual carbon content. In the course of subsequent<br />

reducing atmosphere sintering process, thermal degradation of residual carbonaceous<br />

content will likely occur, and eventually lead to lower carbon content.<br />

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