A study of the effect of natural radiation damage in a zircon crystal using thermoluminescence, fission track etching and X-ray diffraction

The natural radiation damage in zircon caused by the decay of uranium and thorium, present as impurities, is studied, The radiation damage is first gauged by etching the fission tracks. It is found that thermoluminescence (TL) sensitivity (defined as light output per unit test-dose) decreases as the radiation damage increases, suggesting a destruction of TL centres. The spacing d of the (112)-plane is also measured. It is also found that the d-value increases with radiation damage, suggesting the displacement of atoms from their normal lattice sites. However, as the track density increases beyond 3 × 10⁶ tracks/cm², the d-value remains at 2.52 Å. By annealing the crystal, the displaced atoms are found to return to the original lattice sites, and this is followed by a reduction in d-value as well as the recovery of TL sensitivity. The fission track density also decreases and all the tracks disappear at the annealing temperature of 800°C.     

Neutron-irradiation effects on track etching and optical characteristics of CR-39 (DOP) nuclear track detector

The effects of thermal neutron-irradiation in the neutron fluence range of (1.77–7.08) 10¹¹ n/cm², on the etching and optical characteristics of diethylene glycol bis allyl carbonate (dioctyl phthalate doped), CR-39 (DOP) nuclear track detector have been studied using etching and UV–visible spectroscopic techniques. The bulk etch rates determined at different fluences were found to increase with an increase in neutron fluence up to 3.54 × 10¹¹ n/cm², and then decrease at higher neutron fluence. The optical absorption spectra in the wavelength range of 200–800 nm were also recorded for the unirradiated and neutron irradiated samples in the above fluence range. The optical energy gaps (E _g) were determined by the shift in optical absorption edges as observed by UV–visible spectra of the neutron irradiated sample, using Tauc’s expression. The UV–visible spectra results were further supported by determining the activation energies for bulk etching.     

Visualization of solute distributions in dendritic and spheroidized Al grains characterized by both color etching method and electron probe microanalysis

Spheroidization of Al grains was realized by compressing and partially remelting the as-received A356 aluminum alloy billets with a dendritic microstructure. A color etchant named Weck’s reagent was used to characterize the microstructures of both dendritic and spheroidal Al grains. After etching, color differences were observed inside Al grains. In the spheroidal grains, both the original dendritic structure and grain growth during water quenching were revealed by this reagent. By electron probe microanalyses, it was found that such color difference was strongly related to the microsegregation of Ti. Also, both microsegregations of Si and Ti were found in dendritic Al grains, as well as the grain growth of spheroidal Al grains during water quenching. Quantitative analyses indicated that after heating and partial remelting, the concentration of Ti was increased from dendritic grain to spheroidal grain. This phenomenon was discussed and considered to be related to Ostwald ripening and the increase of Ti solubility in Al as the temperature increased.     

Evaluation of etching correction factor for LR115 cellulose nitrate films from track parameters

LR115 cellulose nitrate films efficiency is strongly dependent on the conditions of etching. In this paper a new method to evaluate a correction factor for this effect is given. The film is scanned with an high-resolution scanner, the diameter of the tracks is measured, and the correction factor is calculated from the average diameter of the tracks. The sensitivity of the film is found to have a linear dependence on the average diameter, and the classical correction, based on the residual thickness, can be substituted by a method based on average track diameter.     

Optical limiting behavior correlated with the surface and etching time of irradiated nuclear track detector

The effects of different laser incident intensity on the optical characteristics of PM-355 nuclear track detector have been studied by using photoluminescence (PL) and UV–visible spectroscopic techniques. The polymers were irradiated with alpha particles with close contact to ²⁴¹Am (in contact with a mean energy 5.49 MeV) and then exposed to continues waveguide (cw) laser with different incident intensity. A noticeable decrease in the photoluminescence spectral intensity was observed with increasing laser incident intensity. From the UV–visible spectra, it is found that a shift in the absorption edge towards a longer wavelength with increasing laser incident intensity can be readily observed. The absorption peak with increasing incident intensity is seen to change into a broad one. The optical band gaps determined from the UV–visible spectra were found to decrease with the increase of cw laser doses. The calculations were made of the number of carbon atoms per conjugation length, N and number of carbon atoms per clusters, M embedded in the network of polymers. The effective of etching time on optical power limiting behavior of sample was also investigated. The optical power limiting behavior was found to vary with the etching time. It also shows a very good optical limiting behavior with a limiting threshold varying from 16.6 to 19.9 mW. These results indicate that the PM-355 nuclear track detector is a promising candidate for applications in the nonlinear optic field.     

Efficiency of Billoir's track fitting method for the OPAL central detector

Track fitting in the OPAL central detector can be improved at low energies with a recursive method due to Billoir [1], which accounts for multiple scattering.     

Effects of trace lead on the etching of aluminum foils for high voltage electrolytic capacitors

The effects of the addition of lead on the morphology, microstructure and capacitance of etched aluminum foils for high voltage electrolytic capacitors are investigated here. The results show that the etched tunnels had square cross sections about 1.3 m per side. The inner tunnel sidewalls had a rough corrugated texture with regular ripples with a periodic interval of about 0.12 m. The addition of lead to high purity aluminum foils can effectively increase the number of grains and etched holes, which enhances the etching of the surface. However, the cubic textured fraction will be reduced. The experiments showed that the maximum capacitance was obtained when the incremental addition of lead reached 0.3 ppm.     

移动荷载作用下轨道基础刚度突变对轨道振动的影响

通过建立移动荷载作用下具有基础弹性刚度突变连续梁的振动微分方程，得到了梁的变形解析表达式。利用该解析解和叠加原理，以车辆通过铁路轨道为例，研究了轨道基础弹性突变对轨道振动的影响。分析了单轮对和一台TGV高速动车通过五种轨道刚度比时的轨道动力响应。计算表明，基础弹性突变对梁的振动有较大影响，其影响随着移动荷载速度的增加而增加。     

包络变形对阶比分析结果的影响及消除方法

转速变化的滚动轴承故障诊断通常先采用计算阶比跟踪技术消除变转速的影响,再进行阶比分析获得故障特征。然而,等角度重采样会引起冲击包络变形进而导致阶比分析结果产生偏差,在转速变化范围较大时这个偏差必须要受到重视。本文的主要工作是介绍了等角度重采样方法,仿真了包络变形对阶比分析结果的影响,给出了峰值点间隔变化量详细的理论推导,提出了通过修正角度变换值来消除包络变形影响的方法,并进行了实验验证。研究结果显示,包络在宽窄方向的变形对阶比分析结果没有影响;相邻包络峰值点间隔的变化对阶比分析结果产生影响;在角度序列逐点减去峰值点间隔变化量可消除包络变形对阶比分析结果的影响。     

Effects of radical-distribution control on etching-profile uniformity in dielectric etching

Uniformity control of etching profile and etching rate across a wafer during damascene etching was investigated using a UHF-ECR etching apparatus with a dual-zone gas-injection system. Uniform etching rate was obtained under various conditions by controlling magnetic field distribution. It was found that etching profile could be controlled without affecting etching-rate uniformity by changing the ratio of inner- to outer-nitrogen-gas flow rate above the wafer. The effect of feed-gas control on radical distribution was evaluated by simulation and measurement of the radical distribution, which showed that controlling the gas-mixing ratio changed the distribution of the nitrogen-to-CF_x ratio. With SiOC via hole etching, nanometer-level bottom-CD uniformity at high etching-rate uniformity was obtained.     

Effects of disoriented grains on the elastic constants of directionally solidified superalloys

Two models, namely, coaxial and non-coaxial, are proposed to estimate the elastic constants of directionally solidified superalloys, which behave like transversely isotropic materials and require five independent elastic constants. Coaxial model considers each grain as an individual and obtains the averaged values. Because of the longitudinal grain structure, three independent constants are carried over from original cubic single crystal and the other two are obtainable through the averaging process. For each disoriented direction in the non-coaxial model, a lumped grain, which behaves like a transverse isotropy is proposed. By assuming the disoriented angle follows Weibull distribution, non-coaxial model obtains the expectations of compliances from probability consideration. Disoriented effect could be simulated through the parameters of Weibull distribution. Experimental off-axis Young's modulus data are compared with numerical predictions by both models. Excellent agreement is observed between coaxial model and 90° off-axis experimental data. However, the coaxial model over predicts the 45° off-axis Young's modulus, because anisotropic coupling effect is very strong in the real off-axis specimens. As non-coaxial model considers the disoriented effect, excellent agreement is observed between non-coaxial model and 45° off-axis experiment data. Disoriented grain consideration reduces the anisotropic coupling effect and predicts better to the real off-axis specimens.     

Growth of TGS single crystal by conventional and SR method and its analysis on the basis of mechanical, thermal, optical and etching studies

Unidirectional <001> bulk ferroelectric Tri glycine sulphate (TGS) single crystal of diameter 18 mm and length 150 mm was successfully grown by SR method. The grown TGS single crystal was characterized using etching, Vicker's microhardness, TG-DTA and UV-Vis analysis. The TGS crystals grown by SR method have higher hardness than conventional method grown crystals. Dislocation density (DD) is less in SR grown crystal compared to conventional method grown TGS crystals. The transmittance of SR grown TGS is 8% higher than that of the conventional grown crystal.     

T-stress and its implications for crack growth

Some of the “irregular” crack growth behaviour observed in different specimen geometries may not be unrelated. Discrepancies in fatigue crack growth rate have been observed in different specimen geometries of the same material; crack front “tunnelling” and out-of-plane crack growth have been found in mode I tension at elevated temperature. The results presented in this paper seem to indicate the relevance of a crack tip constraint parameter, the elastic T-stress, to the irregular crack growth behaviour that conventional LEFM fails to explain.     

Effects of trace silver on etching of aluminum electrolytic capacitor foil

The effects of the addition of silver content and stabilizing treatment on etching morphology, microstructure and static capacity were investigated for aluminum foils of an electrolytic capacitor. It was found that silver content in foils promoted Al–Fe–Mn and Al–Fe–Mn–Si precipitation as well as enhanced surface etching. The static capacity increased with increasing of silver content up to 0.2% and then decreased. Also, the stabilizing treatment enhanced re-crystallization so as to increase the static capacity of the cathode foil.     

纳米多孔硅的电化学制备及性能研究

纳米多孔硅是一种潜在的化学和生物传感材料,本文采用电化学腐蚀法制备纳米多孔硅.采用SEM技术分析多孔硅的表面形貌,研究了腐蚀条件对多孔硅的孔隙率、厚度、Ⅰ-Ⅴ特性的影响.结果表明,多孔硅的孔隙率随着腐蚀电流密度和腐蚀时间的增加而呈线性增大趋势;其厚度随着腐蚀电流密度的增加而近似呈线性增大趋势,随腐蚀时间的成倍增加而显著增大;其Ⅰ-Ⅴ特性表现出非整流的欧姆接触.     

Friedel-pair based indexing method for characterization of single grains with hard X-rays

A new evaluation procedure is presented to characterize the orientation and position of single grains within the bulk of a polycrystalline sample. Considering the symmetry properties of Friedel-pairs the contributions to reflection spot positions arising from grain orientation and position could be clearly separated. The proposed method avoids simultaneous fitting of all grain parameters with the goal of a higher accuracy. Depending on the number of reflections considered the accuracy of grain orientation may be less than 0.1°, and the position of the center of mass of the grains can be accurate within one-third of the pixel size.     

Effects of particle size and laser-induced heating on the Raman spectra of alpha quartz grains

Raman spectra of alpha-quartz (Qz) grains of various size (250 microm to < 11 microm) and arrangement (individual and aggregated) have been investigated with a combination of confocal Raman and micro-Raman systems. Frequency downshift and line broadening of the 464 cm(-1), v,(Si-O-Si) band are observed in the smallest size group (< 11 microm, both individual grains and aggregates) because of laser-induced heating and are used to estimate the temperature of the sampled region. The intensity ratio of the anti-Stokes to Stokes Raman lines is also used to estimate the vibrational temperature of the samples under different excitation power. The degree of laser-induced heating is more noticeable in the aggregates than in the individual grains with the use of medium-level laser excitation (< or = 150 mW). Heating diminishes with increasing grain size, and it can only be detected in grain aggregates between 11 and 20 microm in diameter using 150 mW excitation. Intensity studies of the v(s)(Si-O-Si) band using individual grains show no noticeable signs of grain size effects. However, grain size effects become an important factor in the study of aggregates in which spectral intensity diminishes with respect to decreasing grain size.