lids are prepared by compacting nanopartieles, Synthesized by the Coprecipitation method, under different pressures. The varitions of structure and interface states of the NiFe2O4 nanosolids with compacting pressures are studied by x-ray diffraction and electronic spin resonance (ESR). It is found that the crystal structure of the nanosolids has not changed under pressure up. to 6.0 GPa. but the linewidth and δ-factor values of their ESR spectra increased significantly with increasing pressure up to 45Gpa and then decreased slightly with further increase of pressure These variations are discussed in terms of the changes of interparticle magnetic dipole interaction and superexchange interaction in NiFe2O4 nanosolids under different pressures. The experimental resules. suggest that 45 Gpa is the optimum forming pressure. under which the NiFe2O4 narioparticles can be compacted into a dense solid with their structure and nanoproperues still preseyed.

Crystallization processes of an amorphous (Fe0.99. Mo0.01)78 Si9B13 alloy induced by mechanical milling and annealing at pressures from O to 7.0 Gpa were studicd. It is found that the milling time needed for the crystallization of the amorphous alloy and its crystallization products are related to the milling intensity. The crystallization products are an α-Fe(Mo, Si) disordered solid solution at a lower milling intensty. while at a higher milling intensity they aare α-Fe(Mo, Si), Fe-Si-B. and Fe2B phases. BY comparing the mechanical crystallization of the amorphous alloy with its high pressure crystallization. it is suggested that crystallization of the amorphous alloy driven by ball milling results from the simultaneous action of local pressure (4-6 Gpa) and local tempterature (600-700K), which are produced by the collision of steel balls. The local pressure decreases the thermodynamic potential barrier of nuclecleation and inereases the diffusion activation energy in the processof mechanical crystallization, Leding to that crystallization of amoirphous alloy is depressed when the crystallization needs a long-rane atomic diffusion and is promoted when the crystallization needs atomie diffusionless or short-range diffusion. The local temperature plays the same role in the mechanical crystallization as the annealing temperature in the thermal crystallization.

By using series expressions of space-dependent electrical field in a periodic composite. Which are obtained by a simple Fourer approach. The frequency dependeoce of the effective third-order nonlinear susceptibility xe of the metal-insulator composites with simple cubic arrays of coated spheres has beea exactly calculated. The results show that the frequency-dependent nonlidear response of the composites has two sharp peaks when the metal phase forms a shell structure. The strengths of the peaks are very sensitive to the relaxation time of the metal. The dependences of both the shapes and strengths of the peaks on the rakii of the cores of the coated spheres are also studied.

With the single crystals of diamond without boron as starting materials and then by adding boron atoms to their surface aggregate crystals of diamond have been synthesized under high pressure. By the analytical methods of mokifie particle-tracking autoradiography and use of an ion microprobe, the microstructure of the boron-atom distribution in thaggregate crystal of diamond has been directly observed to test and verify the distrbution model of boron atoms. The reasor why the oxidation resistance and the chemical inertia for the aggrgate crystals of diamond containing boron are excellent ar explained.

By using the decoupling aproximation and a series expression of the effective dielectric function ε., the frequency-dependent cubic nonlinear susceptibility X., of metal-insulator composites with periodic structure was strdied. The results show that if the nonlinear metal phase is in the form of coating on the linear insulator core particles. the nonlinear frequency response o the composite has one sharp peak near the surface plasmon response frequcncy of the metal. and. an enhancement of x. of several orders of magnitude can be produced. The result s also show that the nonlinear response of the composite is sensitive to the relaxation time of the metal and the dielectric constant of the linear insulator.