In the processing of multilayer ceramic multichip modules (MCM's), a ceramic substrate, such as alumina, along with a polymer, such as poly(methyl methacrylate) (PMMA), solvents, plasticizers, flocculants, is thermally degraded before sintering. The thermal degradation of PMMA from the green body of oxide ceramics leaves behind some amount of residual carbon in the ceramic. Carbon concentration above 100 ppm has a deleterious effect on the physical properties such as fkxural strength, density, breakdown voltage and dcnsification behavior of the ceramic. This paper discusses the kinetics of oxidation of carbon formed by the thermal degradation of poly(methyt methacrylate) in alumina. Pellets of 5 urn and I urn size alumina were made at 6000 psig in a single step change. Kinetic runs were made in the temperature range of 673 to 993 K with steam as the oxidant at a flow rate of 9.96E-03 g/cm2 sec. The organics (polymethyl methacrylate, methyl ethyl ketone, methanol) concentration was varied from 5 to 20 by weight%. The oxidation products were analyzed using a Varian 3700 gas chromatograph coupled with CDS 111 integrator, and by volumetric analysis. Carbon analysis was carried out at the IBM Fishkill center using a Leco analyzer. Kinetic rates and activation energies are evaluated. 相似文献
Photodegradation of humic substances causes drastic changes in the UV–vis absorption and fluorescence properties of humic acids. In this study it is intended to fulfill the lack of knowledge about the spectral changes of humic acids during photocatalytic oxidation processes and elucidate the effects observed on the molecular size distribution of humic acid focusing on their analysis by UV–vis and fluorescence spectroscopy.
As confirmed by the spectroscopic evaluation of the molecular size distribution data, photocatalytic degradation of humic acid leads to the formation of lower molecular size (small fractions) and higher UV absorbing compounds. For fractions less than 10 kDa, UV254 absorbing moieties in treated humic acid samples become higher than that of raw humic acid designating the generation of new species during photocatalysis. UV–vis spectroscopic changes were also evaluated by the parameters relating to the concomitant removal of the total organic carbon as well as by the ratios using absorption values at discrete wavelengths. Moreover, the fluorescence spectra of treated humic acid samples show decreasing intensity profiles with increasing photocatalytic irradiation time. 相似文献