V. V. GORBACHEV et al. : Light-Induced Thermal Gratings in Nat,ural Diamond 901 phys. stat. sol. (b) 160, 901 (1988) Subject classification: 66.70 and 78.35; S6 Central Gemological Laboratory, Moscow (a) and Imtitute of Physics, Academy of Sciences of the Beloruasian SBR, Minsk1) (b) Light-Induced Thermal Gratings in Natural Diamond BY V. V. GOBBACHEV (a), V. M. DURMOV (b), R. B. ZEZW (a), E. 1'. Ivagw (b), A. S. RUBANOV (b), and Pa. A. TATYANINA (a) For the first time thermal dynamic gratings in Ia-type diamond are recorded. Thermal diffusivity of eight samples is measured by diffraction of a ow laser beam from light-induced spatially periodic temperature distributions. The connection between absorption of the 8.6; pm, wavelength and the thermal resistance of the crystals is demonstrated. No strict correlation is.observed due t o the influence of defects on the heat transfer in diamond which do not appear in the JR spectrum.

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obtaining not only the volume content of the filler but also of the binder and the pores by separating the porosity into open and closed and retaining the completeness of the specimen. Analysis of the curves in Fig. 4 shows that the porosity is reduced in layers with elevated binder content. The arrangement of the interlayers over the material thickness is seen from the curves, the tendency to increase the volume content of binder with the approach to the specimen outer surface is noticeable because of its extrusion during winding due to the contract pressure of the layers. Closed pores predominate as in the first experiment. Therefore, the proposed tomographic method of determining the composition of composites permits computation of the volume content of the original components, the porosity, the volume content of the open and closed pores in each elementary layer of material, and clarification of the regularities of its structure. coefficients of attenuation of the fiber, binder, air of the i-th layer of the dry specimen; i-th water-saturated layer of the specimen; j-th cell of the i-th layer of the specimen under investigation, impregnator; n, quantity of cells in the i-th layer, mfi, ml, m2, weight of the dry and impregnated specimens in air and in water; Ccl, closed porosity; Sf, rms deviation of the linear attenuation coefficients; and ~, volume closed pore content. LITERATURE CITED i. P. G. Cheremskoi, Methods of Investigating the Porosity of Solids [in Russian], Moscow