Radiation Physics and Chemistry (1977)最新文献

The low-dose radiolysis of N₂-O₂ mixtures has been investigated at 101 kPa and 299 K. Measurement of the yield for NO and NO₂ as a function of the N₂ mole fraction has been analyzed to give a G(N) value of 7.3 ± 1.5 for the yield of N(⁴S) and N(²D,²P) atoms for the radiolysis of N₂. Computer simulation of the neutral N₂O₂ chemistry under radiolytic conditions showed that N atoms are predominately formed in a metastable state. Predissociation of N₂ electronic states in the 12 to 16 eV range is responsible for the production of metastable atomic N(²D) and N(²P) atoms.

The isothermal luminescence (ITL) from glassy polyethylene adipate (PEA) γ-irradiated at 77 K was observed over a long period of time, together with effect of the electron scavengers on it. The decay behavior of ITL is similar to that of polyethylene terephthalate or polycrystalline PEA obtained previously, so that the decay obeys the decay function I(t) = I₀/(1 + αt)^m. The detailed discussion on the parameters included in the decay function is given. Differences in the parameters between different materials or different physical states are found not to be very large, except the parameter I₀. Addition of biphenyl into PEA enhances considerably the intensity of ITL and causes the luminescence center to exchange from the ester cation into the biphenyl cation. In the biphenyl doped PEA, the possibility of the triplet-triplet energy transfer from the excited ester group to the biphenyl and the positive charge transfer from the ester cation to the biphenyl are shown.

Spectra of electrons in ethylene glycol (EG)-hexamethylphosphoric triamide (HMPA) were studied at 77 K and higher temperatures as a function of matrix composition. The changes of such spectral characteristics as position of maximum, half-width of electron band and the yield of trapped electrons were interpreted in terms of a simple two-site model of electron trapping. Shallow trapped electrons are located among HMPA molecules while deeply trapped electrons are located inside EG clusters. The process of EG clustering starts stepwise at ∼50 mol% EG. The interpretation of spectral changes at higher temperatures is more complex because of the different thermal stability of electrons located in traps of various depths.

The gamma radiation grafting of N-vinyl-2-pyrrolidone (N-VP) to segmented polyetherurethane (SPEU) was studied.

The grafting was performed by the preswelling technique. In this work the experiments of the polymer films preswollen in N-VP-aqueous solution with different acidity and basicity showed that the radiation grafting only occured in the basic medium.

The influence of temperature, swelling degree in the basic monomer aqueous solutions and irradiation time at constant dose rate on the grafting yield were investigated.

The swelling behavior of the modified films in water was followed. The penetration of the N-VP into the SPEU was studied by using absorption kinetics and its surface structure was observed by scanning electron microscope. The thrombo- resistance test of the film also has been performed. All the results showed that this grafting procedure was successful.

The high speed and depth of cure possible with electron initiated monomer/oligomer coating systems provide many new opportunities for approaches to product finishing. Moreover, the use of transfer or cast coating using films or metallic surfaces offers the ability to precisely control the surface topology of liquid film surfaces during polymerization.

Transfer coating such as with textiles has been a commercial process for many years and the synergistic addition of EB technology permits the manufacture of unusual new products. One of these, the casting paper used in the manufacture of vinyl and urethane fabrics, is the first EB application to use a drum surface for pattern replication in the coating. In this case the coated paper is cured against, and then released from, an engraved drum surface.

Recent developments in the use of plastic films for transfer have been applied to the manufacture of transfer metallized and coated paper and paperboard products for packaging. Details of these and related processes will be presented as well as a discussion of the typical product areas (e.g. photographic papers, release papers, magnetic media) using this high speed transfer technology.

In the past two decades, a number of results in the field of R/D of the radiation processing have been attained in China. Many of them are of great value in application and have been put into pilot plant or trial production. From the viewpoint of system analysis, the radiation processing as a technological system follows its own law of development, now entering a stage of rapid development in the areas of R/D and application. As a favourable factor for the development of radiation, two significant policies have been formulated; first, the policy of development of science and technology should contribute to the development of national economy; secondly the policy of the development of atomic science and technology emphasis should be shifted to civil purposes. These two policies are bound to greatly promote the R/D of the radiation processing, especially its transfer and diffusion. Now, the linkage between the radiation processing and national economy is getting closer and closer. A lot of proposals for investment in this field have been put forward recently. Therefore, it is vital to make investigations into the strategy for the developing, economic effectiveness and the criteria in project selection of the radiation processing.

In this article, we study the present state and the Characteristics of the technology transfer of radiation processing in China from the viewpoint of system analysis and of effectiveness. We also analyse this issue in the light of the concept of life cycle of technology so as to establish, we hope, a realistic goal and an appropriate development strategy. Based on this, a model of project selection and suitable forms of diffusion and transfer are suggested.

The possibility of using a 12 MeV linear accelerator for control of minority carrier lifetime in silicon power rectifiers and thyristors to be used at high frequencies has been investigated. Electron irradiation of these devices has been used in place of metallic diffusion and ⁶⁰Co gamma irradiation. A comparison with the latter two techniques is made. The relation between absorbed dose and high and low injection lifetimes (τHL and τLL) has been studied for diodes and from the linear relationship $\text{1}\text{τ}\text{=}\text{1}\text{τ}{}_0\text{+ KD}$ found, values for the damage constant have been calculated. The dependence of the stability of the electrical characteristics of the silicon devices after electron irradiation on the annealing process at 150, 200, and 360°C has been analyzed. The conclusions drawn from this study are that charge lifetime control in semiconductors is feasible by high energy electrons because electron irradiation provides the more precise, uniform, and reproducible method of lifetime control. In addition this technique is much better than the conventional metal diffusion or gamma irradiation in raising the quality and end-product rate of these devices.

ITL spectra of γ-irradiated pure PMMA and PMMA matrices containing anthracene, pyrene, and naphthalene were studied at 77 K. Luminescence was found to be formed as a result of recombination of PMMA⁺ and aromatic cations with anionic species. The process occurs according to tunnelling mechanism.

Mechanisms leading to OH radical induced strand-break formation in polyuridylic acid are summarized and discussed on the basis of recent results obtained by light scattering, conductivity, pulse radiolysis and ESR methods.