No abstract

No abstract

According to Doyle, the thermogravimetric curve of a decomposition reaction can be expressed by the equation log g(a)-log p(x) = B. The variable x depends on the temperature T,, at which the fraction of the initial compound decomposed is a. Both g(a) and p(x) depend on temperature; however, B is independent of temperature. The trial-and-error method allows, for a given thermogravimetric curve, the determination of the g(u) and p(x) functions fitting the equation and thus an estimation of the probable mechanism of the reaction and of other kinetic parameters (activation energy and frequency factor). To facilitate the analysis of experimental data, a table of log g ( a ) values for various decomposition mechanisms and a plot of -log p(x) vs T for various activation energies are presented. The use of the table and the diagram is described.

In der umfassenden Übersicht werden heterogene Gleichgewichte, ihre Untersuchung durch thermische Analysenmethoden, die Theorie der Kinetik und des Mechanismus nichLkatalytischer heterogener Prozesse, die Kinetik bei nichtisothermen Bedingungen sowie die für die thermische Analyse notwendige Apparatetechnik behandelt.

BORON suboxide, B60, is fabricated by reaction hot-pressing of appropriate amounts of boron and boric acid.' At room temperature the zero porosity Young's modulus is 68.5 X 10, psi and the zero porosity flexure strength is 51.9 x 103 psi, the latter value for a grain size of 1In the current study, the room temperature compressive strength of B 6 0 was investigated as a function of porosity.Billets of B 6 0 2 in. and 4 in. in diameter were fabricated by the authors2 and by Avco Corp. ,3 respectively. Specimens nominally % in. in diameter by -76 in. long were machined by diamond grinding techniques. After machining they were subjected to radiographic analysis to determine if macrocracks or discontinuities were present.Compressive strength was determined using a commercial testing machine; and a rate of loading of 0.05 in./min. Hardened steel platens were used with a 0.005 in. thick soft aluminum shim between the specimen and platen.Data for the effect of porosity on compressive strength are given The writers are with the