摘要:

Polyvinylidene fluoride (PVDF) films were bombarded with 50–350 keV ion beams with fluences of about 1 × 1015ions/cm2. Structural modifications induced by the ion beam irradiation were studied ‘in situ’ by monitoring the desorbed gases from the irradiated polymer by quadrupole mass spectrometry and ‘ex situ’ by X-ray diffractometry analysis. The chemical yields of the emitted H2and HF molecules are of the order of 1 desorbed molecule per 100 eV incident energy. The chemical yields of these molecules were investigated as a function of the irradiation conditions and ion fluences. The experimental results are discussed from the standpoint of the chemical evolution induced by ion energy deposition in the bio-polymer.

ISSN:1042-0150    

DOI:10.1080/10420159508226268

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The collisional damage profiles of high dose 0.7 MeV N+and 1.4 MeV N+2ions in Si crystals, as determined by RBS/channeling, have been compared with each other. The damage produced by molecular ions extends over a broader regime than the one stemming from single-atomic ions. The difference in width of the damage distributions amounts to as much as 30%. This is much more than the 6% difference reported earlier forrangesof single-atomic and molecular nitrogen ions in matter. [1] It supports recent findings of enhanced damage of carbon cluster ions in polymeric matter [2] and on 3D-damage distributions of N+2ions in Si. [3].

ISSN:1042-0150    

DOI:10.1080/10420159508226269

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new approach to modelling the multilayer growth of metal layers by ion beam induced dissociation of organo-metal precursor gases and adsorbate is developed. This involves generation and solution of a hierarchy of mutation equations to describe adsorption and desorption, metal deposition and sputtering. It is shown that such an approach cannot account for contaminant incorporation into the growing film and so the model is improved to allow for this process. Steady state solutions for metal: contaminant ratios are obtained. It is further shown that, even with simple model assumptions, prediction of time dependent growth parameters is difficult.

ISSN:1042-0150    

DOI:10.1080/10420159508226270

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polyvinylidene fluoride (PVDF) is strongly modified by ion irradiation. PVDF films were bombarded with helium beams, 50-350 keV in energy and ion doses ranging between 1012and 1015ion/cm2. Irradiations were performed in vacuum at different temperatures from-150 up to +100°C. Ion irradiation of the fluropolymer produces H2and HF gas desorption, which yields are proportional to the temperature, as detected ‘in situ’ by a quadrupole mass spectrometer. The results can be qualitatively explained by assuming that free radicals of hydrogen and fluorine, produced along the ion track, can diffuse throughout the sample, react, and the resulting melecules desorbed from the polymer surface. Residual irradiated polymer remains drastically modified and rich in carbon content.

ISSN:1042-0150    

DOI:10.1080/10420159508226271

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Tl-based superconducting ceramics of different phases (Tl-2212, Tl-1223, Tl-2223) have been irradiated by heavy ions (6 GeV Pb and U). It is shown by high resolution electron microscopy that Pb irradiations induce columnar defects of about the same diameter (95 ± 5) Å in Tl-2223 and Tl-1223 whereas a larger dispersion of the diameter around the value of 95 Å is observed for Tl-2212. The U irradiation leads to diameters slightly more scattered than in the Pb irradiation. These samples have been studied by SQUID magnetometry before and after irradiation. Drastic increases of the critical current induced by the irradiation have been observed and the ‘hierarchy’ existing between phases about the location of their irreversibility lines remains the same after irradiation at the same fluence.

ISSN:1042-0150    

DOI:10.1080/10420159508226272

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Na2SO4is an interesting material in that it has an ‘open’ structure which can incorporate large number of cations. Solid solutions of Na2SO4with various compounds are thus possible. In this paper we report a compound Na1.58Ba0.105Vc0.105SO4:Eu which exhibited intense fhermoluminescence and interesting Eu luminescence. TL glow curves and photoluminescence in this phosphor are described.

ISSN:1042-0150    

DOI:10.1080/10420159508226273

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Electronic and vibrational absorption spectra of OH- and Cu+ double doped NaF are studied and compared with the same respective single impurity doped host material. New ultraviolet and infrared absorption bands are found, which are supposed to be from a coupling effect of Cu+—OH- defects. The infrared vibrational absorption of the OH- fundamental stretching mode, for uncoupled and coupled defects, were measured using a color center laser, with X cavity configuration and 0.2 cm-1 resolution. The observation of second harmonic absorption are analyzed and the ratio of overtone to fundamental reveals the existence of an electric anharmonicity in addition to the usual mechanical one observed in the Morse's potential model. Further measurements of thermally stimulated depolarization current indicate a permanent orientational freeze-in of the Cu+—OH- defect.

ISSN:1042-0150    

DOI:10.1080/10420159508226274

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The substitutions of Fe3+(I) and Fe3+(II) for both Li+ and Nb5+ions in LiNbO3crystal have been studied using the superposition model. From the studies, it is found that a displacement of the impurity ion along the c-axis is required to reach a good fit between the calculated and observed zero-field splittings b02By analyzing the displacement direction from the impurity displacement scheme suggested in this paper, we can conclude that Fe3+(I) replaces Li+ion and Fe3+(II) replaces Nb5+ion.

ISSN:1042-0150    

DOI:10.1080/10420159508226275

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The measurement of the electrical resistivity, the Seebeck effect and the UV/VIS absorption were carried out in the solid solutions under study. It was observed that: 1) with the increase of temperature the activation energy changes rapidly for all samples, 2) at about 700 K a phase transition from insulating to semiconducting state takes place, 3) the shift of the absorption edge to higher wavelengths is explained by the d-d electron transitions between the chromium ions with the valence state 3+ and 2+.

ISSN:1042-0150    

DOI:10.1080/10420159508226276

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Measurements of the electrical resistivity, the Seebeck effect and the UV/VIS absorption were carried out for samples of AVO4(A = Fe, Cr, Al) compounds. It was observed that: 1) chromium and aluminum vanadates are insulators at room temperature and they have p and n-type electrical conductivity at higher temperatures, respectively, 2) the shift of the absorption edge to lower wavelengths in iron and aluminum vanadates and to higher ones in chromium vanadate in comparison with their constituents is connected with the type of the crystal structure, 3) the charge transport occurs via anion-deficient centers in iron and aluminum vanadates and via cation-deficient centers in chromium vanadate.

ISSN:1042-0150    

DOI:10.1080/10420159508226277

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor