摘要:

The Ar-ion-irradiation effects in the Al70Co15Ni15decagonal quasicrystal (DQC) have been studied by means of transmission electron microscopy (TEM). The phase transformation behaviour is dependent on the dose, dose rate and the thickness of the specimen. The as-annealed Al70Co15Ni15DQC consists of needle-like ordered domains. In the Ar+-ion affected depth the ordered DQC phase transformed into disordered DQC and a b.c.c. phase when the dose is equal to or less than 5 × 1013Ar+/cm2. Then the b.c.c. phase was ordered to CsCl-type structure when the dose was increased to 1014∼ 5 × 1015Ar+/cm2. However, the ordered CsCl structure transformed back to disordered b.c.c. phase with the further increase of the irradiation dose and dose rate. This disordering–ordering–disordering transformation sequence is explained by the Dienes–Potter ordering rate expressions.

ISSN:1042-0150    

DOI:10.1080/10420159708216858

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The fast neutron and gamma ray spectra measured behind different thickness of steel scrap concrete with density of 4 g/cm3have been studied. The mix proportions by weight of this type of concrete were 1 cement: 6.89 steel scrap: 2.9 sand and 0.5 Water. Comparison with a standard ordinary concrete of density 2.3 g/cm3have been carried out. The measurements were made using a collimated beam of both gamma rays and neutrons emitted from one of the horizontal channel of the Egyptian Research Reactor-1. A fast neutron and gamma ray spectrometer with a stilbene crystal was used to measure the spectra of fast neutrons and gamma rays. Pulse shape discrimination using the zero cross over technique was used to separate the photon pulses from the electron pulses. The equation due to Schmidt has been modified and applied for determining the neutron effective removal cross sections (∼R) for steel scrap, ordinary, hematite–serpentine, ilmenite–limonite and ilmenite concretes. This equation gives results which are in good agreement with the measured values. The derived empirical equation in a previous work to calculate the neutron integral flux behind different thicknesses of different types of concretes, gives good results for steel scrap concrete under investigation comparing with the corresponding experimental data. Total neutron macroscopic cross sections, linear attenuation coefficients for gamma rays and the half-value layers for both radiations at different energies have been obtained for steel scrap concrete and comparing with the corresponding values of ordinary concrete. The results show that steel scrap concrete is better than ordinary, hematite–serpentine, ilmenite–limonite and ilmenite concretes from the radiation shielding point of view.

ISSN:1042-0150    

DOI:10.1080/10420159708216859

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The electron spin resonance of γ-irradiated single crystals of methoxycarbonylcholine picrate hemihydrate, C7H16NO3+· C6H2N3O7−· ½ H2O has been observed and analyzed for different orientations of the crystal in the magnetic field. The crystals have been investigated between 70 and 350 K. The spectra were found to be temperature independent and the radiation damage centers are attributed to – ĊŌOCH3and –CH2CH2OĊ radicals. Thegand hyperfine coupling constants were found to be almost isotropic with an average,g= 2.0060,aH1= 4.4G for –CH2CH2OĊ,g= 2.0050,aH2= 3.5G for –CH2CH2OĊ andg= 2.0045,aH= 3.5 G for –ĊŌOCH3. These values indicatealong-range coupling between the unpaired electron and H protons.

ISSN:1042-0150    

DOI:10.1080/10420159708216860

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Measurements of the specific heat,Cp, of lithium potassium sulphate (LiKSO4) crystals doped with thallium, Tl, and rubidium, Rb, with different contents have been carried out. This was done to investigate the effect of a dopant on the ferroelastic phase, at transition temperatureT1≅ 700 K. The thermodynamic parameters, enthalpy change, ΔH, and entropy change, ΔS, at the transition point were obtained. The results showed that as the contents of thallium and rubidium increased (ΔCp)max, was found to decrease slowly to a minimum followed by sharp increase. The critical exponent was changed as the content of dopant increased and the model deviated from the 3d Ising model.

ISSN:1042-0150    

DOI:10.1080/10420159708216861

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Specimens of dry cortical bovine bone and bone equivalent ceramic of Ca/P ratio 1.95 were prepared and subjected to two fast neutron fluences of 1.15 × 106and 1.13 × 108n/cm2. Radiation damage was assessed by following their surface morphologies (SEM) and their selected area electron diffraction (SAED) patterns of both specimens using the scanning and diffraction electron microscope techniques.

ISSN:1042-0150    

DOI:10.1080/10420159708216862

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The shielding effect of an iron sphere assembly has been tested for a Pu-α-Be neutron source placed in the center of the shield assembly. Emergent neutron and gamma spectra were measured with a stilbene scintillation counter. Discrimination between neutrons and gammas was achieved by the pulse shape discrimination technique based on the zero crossing method. Calculations have been made using the one-dimensional transport code ANISN-Westinghouse version (ANISN-W) and the EUR LiB 15/5 cross section data set. The agreement between measurements and calculations indicates that the cross section set and the calculation model are suitable for studying the iron shielding experiments over the neutron energy range 1.35–10 MeV and the gamma energy range 0.3–6 MeV. Total macroscopic cross sections for fast neutrons, linear attenuation coefficients for gamma rays and half-value thicknesses for neutrons and gammas for the whole energy range and at different energies have been obtained.

ISSN:1042-0150    

DOI:10.1080/10420159708216863

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1042-0150    

DOI:10.1080/10420159708216847

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor