Vol.7,

390

327

358

The mechanical properties of functional heat-resistant ceramics SiC are significantly influenced by the concentration and dimensions of pores. Small angle neutron scattering measurements for 3 SiC samples with different densities are performed on C1-2 SANS instrument of the University of Tokyo. Two groups of the neutron data are obtained using 8 and 16 m of secondary flight path, 1 and 0.7 nm of neutron wave lengths, respectively. After deduction of background measurement and transmission correction, both neutron data are linked up with each other. The patterns of neutron data of 3 samples with Q range from 0.028 ~ 0.5 nm^-1 are almost with axial symmetry, showing that the shape of pores is almost spherical. Using Mellin transform, size distributions of pores in 3 samples are obtained. The average size (~19 nm) of pores for hot-pressed SiC sample with higher density is smaller than the others (~21 nm). It seems to be the reason why the density of hot-pressed SiC sample is higher than not hot-pressed sample.

319

The solvent extraction of U(VI) and Th(IV) from nitric acid medium by N,N,N',N'-tetrabutylsuccinylamide(TBSA) in a diluent composed of 0.5 volume fraction trimethyl benzene(TMB) and 0.5 volume fraction kerosene(OK) has been studied. The distribution ratios of U(VI) and Th(IV) as a function of aqueous HNO₃ concentration, extractant concentration and temperature have been measured. From the data, the composition of extracted species, equilibrium constants and enthalpies of extraction reaction are also calculated.

365

263

The austenite to martensite transformation in fine Fe.₉₀Ni.₁₀ particles prepared by evaporation is studied by Mössbauer technique. Unlike bulk Fe.₉Ni.₁ which is entirely transformed to martensite, these particles show a remarkable austenite stability upon cooling upto liquid nitrogen temperature. This stability is associated with the oxide surface layer formed on the particles and also with their small size. A hyperfine field approach is employed to analyze the martensitic transformation in the particles. It is also shown that, in contrast with large particles, the temperature variation of the Mössbauer average hyperfine field of the fine particles can be satisfactorily explained in terms of the collective magnetic excitations model.

308

Using conversion electron Mössbauer spectroscopy (CEMS) and slow positron beam, the chemical state of ⁵⁷Fe ( 100keV, 3 ×10¹⁶ cm^-2) implanted into ZrO₂ containing 0.03 mole fraction Y₂O₃ (ZY₃) and its thermodynamic behavior during annealing process at 200 ~ 500℃ are studied. For as-implanted sample, Fe chemical states of Fe⁰, Fe²⁺ and Fe³⁺ are observed, and assigned to the superparamagnetic metallic iron cluster, iron dimer (and trimer) and complex of the Fe³⁺ associated with cation vacancy (V) and oxygen, respectively. After annealing at 400℃ the complexes of Fe³⁺-V are mostly dissolved, and the prior phase to α-Fe and α-Fe nano- crystalline cluster are present in the sample. Meanwhile the mixed conducting of oxygen-ions and electrons in the ZY₃ sample containing Fe appears, it may correlate with the different iron charge states and their relative amounts, in particular with the α-Fe nano-granule.

687

272

286

563

390

288

477

605

The biological effects of wheat seeds irradiated by 48MeV/u and 20 MeV/u ¹⁴N⁷⁺ beams are studied, respectively. The results show: both penetration and implantation of heavy ions can significantly inhibit growing power (height of plant stem) of wheat seeds. The greater dose is, the weaker growing power is, and the implantation influence on growing power is stronger than the penetration; a great variety of chromosomal aberrations were observed in root tip cells of irradiated seeds and the aberration frequencies were several hundred times higher than that of the corresponding control; it has been proved by 3H-TdR incorporation test that unscheduled DNA synthesis exists in irradiated wheat seed embryos. It is found by ESR spectroscopy that the variation of free radical concentration with total dose has different features for the penetrated and implanted seeds.

571

The mortality of lung cancer in Gejiu has reached the peak in the world. The indoor radon levels in Gejiu are measured by SSNTD. The results indicate that a higher indoor radon level widely exists in Gejiu area; the radon level in houses situated in geologic fault zone is 6 times as high as 2 km from fault zone; the radon level in soil in faults is 6~8 times as high as 1 km from faults; the radon level of the cancer patients' houses is 1.45 times as high as healths'. The relationship between indoor radon level and incidence of lung cancer is given for the first time.

275