This paper discusses the of application of combustion synthesis of ceramic and ceramic-metal composites. Several model exothermic combustion synthesis reactions are being used to investigate the effect of reaction parameters, eg. stoichiometry, green density, combustion environment and mode, particle size, physical properties of reactants and products, on the stability and control of the synthesis reaction, product morphology and properties and performance.

Thermochemical and physical processes which occur in various aspects of solid-propellant combustion including steady-state burning, ignition, transient burning, cook-off and crack propagation are presented in this paper. For each case, the various thermochemical and physical properties involved are summarized. In addition, the current direction of solidpropellant research is highlighted. The intent of this paper is to stimulate the interest of materials scientists and engineers in the field of solid propellants so that they will contribute their unique expertise to the advancement of current research. It is also the hope of the authors that the paper will serve as a useful summary of important relationships and parameters for scientists and engineers currently involved in solid-propellant research.

In this study, the stress-deformation response of coal in the laboratory under threedimensional (3-D) loading conditions similar to those existing in an actual coal mine is investigated, and a constitutive model, including the effects of anisotropy, is developed. The coal samples were obtained from a mine in LeFlore County, Oklahoma, at a depth of approximately 25–30 ft below the ground surface. A High Capacity Cubical Device with servo-controlled independent loading along three axes of a cubical specimen and a computerized data acquisition and monitoring system were used to conduct the tests. A total of 21 tests under 4 different confining pressures and 5 different stress paths were conducted. The influence of the degree of anisotropy was investigated by comparing the transversely isotropic and isotropic idealizations for different stress paths (Triaxial Compression, Triaxial Extension and Simple Shear) at different confining pressures (1,600, 3,200 and 5,600 psi). The experimental results demonstrated that the coal exhibits inherent anisotropy and that it can be treated approximately as a transversely isotropic material. Also, the Young's moduli were found to be dependent on the confining pressure. The experimental data were used to evaluate the material constants associated with the elasto-plastic constitutive model developed in the study.

In the ordinary application of the time-lag method to the measurement of the diffusion coefficient of a gas passing through a plane sheet of an inert solid, the gas is pressurized on one side of the sheet and evacuated on the other. After decay of transients, the cumulative amount, Q(t), of gas diffused through the sheet in time, t, assumes the “time-lag” form, Q(t) = A(t - L). Measurements of the slope, A, and the intercept, L, can be used to determine the diffusion coefficient and the solubility of the gas in the solid. We have rederived this law for the case of a solid which is actively evolving this same gas at an arbitrary rate and have used it to predict the rate of outgasing of the solid upon standing. Practical applications of the theory include radioactive decay of minerals, rejection of plasticizers by plastics, and the decomposition of solid rocket propellants.

Combustion of a proper combination of an oxidizer and a fuel can produce the exothermicity required for the simultaneous synthesis of oxide ceramic powders. Oxidizers include metal nitrates, ammonium nitrate, and ammonium perchlorate, while urea, carbohydrazide, glycine and others have been used successfully as fuels. Combustion methods are particularly well-suited to producing multicomponent metal oxides, yielding compositionally homogeneous, fine particles with low impurity content. Organic fuels, particularly those containing nitrogen, also serve as a complexant in the precursor, which inhibits inhomogeneous precipitation from occurring prior to combustion. The exothermic redox decomposition of these oxidizer-fuel mixtures is initiated at low temperatures, usually <250°C. Properties of the products are influenced by the nature of the fuel and the oxidizer/fuel ratio. Many technologically important oxide ceramics have been produced by these methods.

We report on a program to develop and demonstrate a diagnostic technique using infrared fiber optics to probe the decomposition processes in burning gun propellant strands. The present experimental configuration involves measuring the absorption through a small gap between two embedded fibers. The gap can be filled with propellant, or left open to fill with gaseous decomposition products. Spectroscopic detection is presently achieved using pairs of bandpass filters. The absorption record can be correlated with readings from an embedded thermocouple and with a high resolution video recording of the bum. We also report on preliminary experiments in which an electrically heated filament is used to melt the infrared fiber as its transmission and physical appearance are monitored.

The goal of this program is to develop a fast-response probe of solid phase processes which can support the development of a predictive modeling capability for gun propellant combustion. We present examples of data for the atmospheric pressure burning now under investigation. A full assessment of the usefulness of this technique will require further observations and analysis.

The development of a novel technique for sensing trace vapors of -NO2 containing compounds is reported. This technique is based on the use of one laser operating at 226 nm to both photofragment the target molecule and detect the characteristic NO fragment, formed from a rapid predissociation of NO2, by resonance-enhanced multiphoton ionization (REMPI) via its A2Σ+ - X2Π (0,0) band origin. The analytical utility of this technique is demonstrated on a number of compounds, including dimethylnitramine, nitromethane, nitrobenzene, TNT, and RDX, employing molecular beam sampling with time-of-flight mass spectrometric analysis of the jet cooled analyte seeded in an atmosphere of buffer gas. For RDX and TNT, a detection limit of 8 and 24 ppb, respectively, is demonstrated using a laser energy of 100 microjoules/pulse.

A theoretical model is developed to describe multiphonon up-pumping of internal vibrations. The dominant mechanism for up-pumping is anharmonic coupling of excited phonon modes with low frequency molecular vibrations, termed doorway modes. Quantitative calculations were performed which show the extent and rate of multiphonon up-pumping caused by shock excitation. The time dependence of chemical reactivity behind the front is calculated using reaction rate laws for the decomposition of nitramine explosives. A mechanism for hot spot formation, based on defect induced local increases in anharmonic coupling, is discussed.