摘要:

The results are presented of experiments on annealing in reactor and furnace the diamond pre-irradiated with reactor neutrons. It is established that annealing in a reactor proceeds more intensively than thermal annealing provided the γ-flux was lower in primary irradiation than in the secondary one. The γ-flux ratio varied due to the use of absorbing or amplifying screens and also by varying the reactor types or sample position. The experiment is described on electron annealing of a damaged diamond (electron energy 200 KeV). The volume of an elementary cell (expansion) with the constant measured radiographically was used in all experiments as the standard of defects present. The conclusion is that the contribution of γ-radiation always associated with the reactor neutron radiation to the formation of defect structure in materials is quite significant.

ISSN:1042-0150    

DOI:10.1080/10420159608211544

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The paper presents the results on neutron irradiation of the diamond in a nuclear reactor. It is shown that the neutron irradiation stimulates the diamond transition to the amorphous state. At a temperature below 750°K the time required for the diamond-graphite transition decreases with decreasing irradiation temperature. On the contrary, in irradiation at higher temperatures the time of diamond conversion into the amorphous state increases with decreasing temperature but always remains shorter than in the absence of irradiation.

ISSN:1042-0150    

DOI:10.1080/10420159608211545

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Ion beam induced epitaxial crystallization of the outer part of a buried amorphous silicon layer is studied following defect generation into the near-surface crystalline region by 2.5 keV Ar+ion bombardment. It is shown that mobile defects generated as far as 10 nm at least from the amorphous-crystalline interface effectively stimulate crystallization.

ISSN:1042-0150    

DOI:10.1080/10420159608211546

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Stopping powers for ions of O, Cl, Sc, Ti, Cr, Mn, Fe and Cu in the energy range 0.2–1.0 MeV/n have been measured in carbon foils using the elastic recoil ion technique and a twin detector system. Very heavy ions of Gold and Iodine of energy around 100 MeV have been employed to generate the various recoil ions using pure thin (≈ 1000Å) elemental/compound targets. The data have an overall average accuracy of 6%. The stopping power for Sc, Mn and Fe ions in the energy region 0.2–1.0 MeV/n as well as those for Ti and Cu ions in the energy region below 0.45 MeV/n are perhaps the first such measurements. The limitations of LSS theory even within the range of its applicability has been demonstrated. Varelas and Biersack estimates agree well in the region of their applicability lying above the ion velocity limit set for LSS theory. Northcliffe and Schilling predictions as well as the TRIM estimates provide the best fit with data. However, one does notice variations upto 25% for some ions at lower energies in the case of later estimates. Northcliffe and Schilling estimates lie within 10% of the experimental values for all the ions studied except for 0 and Cu ions at certain energies only.

ISSN:1042-0150    

DOI:10.1080/10420159608211547

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this paper we discuss the results of thermoluminescence (TL) studies carried out on freshly quenched crystals of KBr doped with ∼ 50 ppm of Eu2+ions which were X-irradiated at room temperature. The TL glow curve of this phosphor material consists of three glow peaks at 355, 376 and 398 K whose intensities increased as a function of X-irradiation time. The TL glow peaks were analyzed by the total curve-fitting method in order to obtain the characteristic parameters; activation energy, pre-exponential factor and kinetic order. The spectral character of the emission recorded during thermoluminescence was found to be the same for all glow peaks and consists of a broad band centered at ∼ 420 nm. This band is composed of two overlapping bands peaking at 419 and 460 nm. The former band is due to the well known fluorescence of Eu2+ions corresponding to the transition 4f65d(T2g) →8S7/2, while the latter may be associated with the recombination of F-centers with the radiation induced interstitial chlorine atoms which are thermally released from traps. It is proposed that the model of the TL process most consistent with our experimental results is one in which the Eu2+impurity acts as an electron trap during the irradiation process and that the radiation induced center (partner of an F center) and the Vkcenter (partner of an Eu+ion) are trapped together in the form of a Cl3−molecular ion at the Eu2+-cation vacancy dipoles and their smaller aggregate complexes such as dimers, trimers, etc. During the TL run, the H and Vkcenters escape from the trap and recombine with the complementary center giving rise to the observed TL emission spectra. The dosimetric characteristics of the KBr:Eu2+phosphor material are also reported.

ISSN:1042-0150    

DOI:10.1080/10420159608211548

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The zero-field splitting D and the g factor g‖, Δg (= g‖- g1) of the tetragonal Ni2+-VLicenter in LiCl:Ni2+crystal have been studied from the high-order perturbation formulas of these EPR parameters for d8ions in tetragonal symmetry. On the basis of this, the local structure of this tetragonal center is determined and the negative sign of the zero-field splitting D of the crystal is obtained.

ISSN:1042-0150    

DOI:10.1080/10420159608211549

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Thermoluminescence (Tl) properties of cement clinker (C) and its ferrite phase (F) doped with different activators such as CaF2, CaCl2, LiF, MgF2and Zn O were studied. The phosphors were prepared by sintering method at 1450°C for half an hour for cement clinker and at 1320°C for half an hour for its ferrite phase.

ISSN:1042-0150    

DOI:10.1080/10420159608211550

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor