Glow curve analysis applied to solid-state thermoluminescent dosimeters

We describe procedures for approximately solving first-and nth-order glow rate equations for linear and parabolic heating modes and analyze them in comparison with the conventional approach. The results demonstrate that parameters of glow peaks evaluated in the proposed model agree well with experimental and literature data for LiF-based phosphors.     

放电等离子烧结(SPS)技术

放电等离子烧结（SPS）技术是一种新型的材料制备技术。介绍了SPS技术的发展概况、原理、特点及在材料制备领域的应用。最后，对SPS主发展前景进行了展望。     

Glow curve analysis applied to the discrimination of X ray versus proton irradiation

A module for proton track structure simulation in liquid water was implemented in the biophysical model PARTRAC. Simulated tracks of energy deposition events from the radiation under investigation were superimposed on a higher-order DNA target model describing the whole genome inside a human cell. The parameters controlling DNA damage from direct and indirect effects were adapted to agree with yields and pathway contributions derived from gamma ray irradiation experiments. Single and double strand break (DSB) induction was simulated for irradiations by protons, photons and electrons over a wide range of initial energies. The relative biological effectiveness for DSB induction after proton irradiation was found to rise from 1.2 at 5 keV.micron-1 to about 2.5 at 70 keV.micron-1. About half of this growth resulted from an increased production of DSB clusters associated with small (< 10 kbp) fragments.     

Computerized glow curve deconvolution applied to ultralow dose LiF thermoluminescence dosimetry

A computerized glow curve deconvolution technique (CGCD) and its application to the ultralow dose thermoluminescence (TL) glow curve of LiF:Mg, Ti (TLD-100) are described. The benefits in precision and minimum measurable dose (MMD) applied to TLD-100 are considerable. The CGCD analysis interpolatively estimates the background signal under peaks 4 and 5 which greatly reduces the errors introduced by inaccurate background subtraction due to second readout as well as eliminating the need for second readout. In addition, the error introduced via inaccurate separation of peak 3 is reduced and post-irradiation annealing is rendered unnecessary. An additional important feature of the CGCD method is the ability to reject/correct outliers in the glow curve. Assuming an MMD criterion of ±20% (1 SD) precision yields an MMD of 1.9 μGy (0.19 mrad) and 27 μGy (2.7 mrad) for CGCD and routine analysis respectively, i.e., an improvement in MMD of a factor 14.2.     

Master curve analysis of the “Euro” fracture toughness dataset

Brittle fracture in the ductile to brittle transition regime is connected with specimen size effects and - more importantly - tremendous scatter of fracture toughness, which the technical community is currently becoming increasingly aware of. The size effects have the consequence that fracture toughness data obtained from small laboratory specimens do not directly describe the fracture behavior of real flawed structures. Intensive research has been conducted in the last decade in order to overcome these problems. Different approaches have been developed and proposed, one of the most promising being the master curve method, developed at VTT Manufacturing Technology.For validation purposes, a large nuclear grade pressure vessel forging 22NiMoCr37 (A508 Cl.2) has been extensively characterized with fracture toughness testing. The tests have been performed on standard geometry CT-specimens having thickness 12.5, 25, 50 and 100 mm. The a/W ratio is close to 0.6 for all specimens. One set of specimens had 20% side-grooves. The obtained data consists of a total of 757 results fulfilling the ESIS-P2 test method validity requirements with respect to pre-fatigue crack shape and the ASTM E-1921 pre-fatigue load. The master curve statistical analysis method is meticulously applied on the data, in order to verify the validity of the method. Based on the analysis it can be concluded that the validity of all the assumptions in the master curve method is confirmed for this material.     

利用控制烧结曲线及其拓展预测ZrO2陶瓷烧结过程

将钇稳定氧化锆(3Y-PSZ)冷等静压素坯在原位测量仪中进行恒速无压烧结, 升温速率分别为2、5、8℃/min, 通过原位测量仪保存图像, 并用软件Image-Pro Plus 6.0对图像进行处理, 得到收缩数据, 建立氧化锆的控制烧结曲线(MSC), 成功计算出其烧结活化能Q为685.7 kJ/mol。并对控制烧结曲线进行扩展(EMSCE), 模拟出恒定加热速率下整个烧结过程中温度与相对密度的关系, 而不仅仅是预测最终密度。该研究提供了一种预测材料烧结制度的可能性, 确保了所选烧结时间和烧结温度的高精确度和可重复性。     

Sintering of aluminium nitride: Particle size dependence of sintering kinetics

The effect of particle size (0.78 4.4 m) on the sintering kinetics of AIN powder was investigated in the temperature range from 1600 to 2000° C and the results were analysed on the basis of vacancy diffusion models. The mechanisms of sintering are discussed.Fractional shrinkage is proportional to the nth power of soaking time with n = 0.20 for 4.4 m and 1.5 m powders and 0.33 for 0.78 m powder. For the 0.78 m powder at 1900° C, however, n decreases gradually as grain growth proceeds. The experimental activation energy for sintering is between 92 kcal/mole for 4.4 m and 129 kcal/mole for 0.78 m powder. Unlike this activated energy, the rate of sintering and the diffusion constant calculated from it increase drastically with decrease of particle size; the derived diffusion constant for 1.5 m powder is 10¹ to 10² times larger than that of 4.4 m powder, and for 0.78 m powder the diffusion constant is estimated to be still higher.The particle-size dependence of parameter n and the diffusion constant seems to be caused by a variation in predominant diffusion mechanisms; namely, bulk diffusion in coarse powder and surface or grain-boundary diffusion in fine powder.     

Modeling of glass sintering applied for the fabrication of porous glass bodies

The sintering behavior of borosilicate and soda-lime mono-sized glass beads was investigated with the aim to fabricate transparent porous glass balls and cylinders. As the glasses tend to crystallize, temperatures where the sintering was in advantage compared to crystallization were used. Isothermal studies were undertaken for modeling the evolution of sintering necks as a function of radii of beads, temperature and time. The Frenkel model of viscous flow was applied to predict first and second stage of sintering. As the sintering of the glasses without crystallization was only possible at high temperatures the process is very fast and has to be controlled precisely. The results of this work were applied for the fabrication of porous bodies with specific characteristics: different geometries and sizes, transparency, high porosities to be achieved during first stage sintering of spherical glass beads. The porous parts with these characteristics are used for the investigation of hydrodynamic processes in the pore network of glass parts.     

Sintering forces in equilibrium and non-equilibrium states during sintering of two particles

The sintering force was originally defined for an equilibrium state, in which the sintering contraction is balanced by an external force. The concept of sintering force can be expanded to non-equilibrium process of sintering by using Beere's definition of sintering force. The sintering of two spherical particles was simulated by using the Surface Evolver program. The shrinkage rate was approximately proportional to the sintering force in a non-equilibrium process. The sintering force in a non-equilibrium process was smaller than the force necessary to stop the shrinkage at equilibrium.     

Sintering behavior and microstructure evolution in cp-titanium processed by spark plasma sintering

This paper investigates the effect of various sintering temperatures from 800 to 1500?°C on the microstructure evolution of cp-titanium processed by Spark Plasma Sintering (SPS). The material processing conditions under consideration may change the obtained atomic order and microstructure. The different relation of the mechanical and corrosion resistance properties observed in the analyzed results could at the same time be shaped in the expected range. The SPS procedure allows the obtainment of nearly theoretical densities of the compacts and excellent mechanical properties (UTS?=?892?MPa, CS?=?1442?MPa). The results confirm that the contact angle measurement could support the process control, particularly if a microstructure feature is considered.     

Sintering forces in equilibrium and non-equilibrium states during sintering of two particles

The sintering force was originally defined for an equilibrium state, in which the sintering contraction is balanced by an external force. The concept of sintering force can be expanded to non-equilibrium process of sintering by using Beere’s definition of sintering force. The sintering of two spherical particles was simulated by using the Surface Evolver program. The shrinkage rate was approximately proportional to the sintering force in a non-equilibrium process. The sintering force in a non-equilibrium process was smaller than the force necessary to stop the shrinkage at equilibrium.     

Fragility curve probabilistic model applied to durability and long term mechanical damage of masonry

In view of preserving the historical heritage, the deterioration processes of masonry materials and the long term damage of multiple leaf historic buildings is studied from an experimental and a numerical point of view. Durability tests and pseudo-creep tests have been carried out and interpreted through probabilistic models for the service life prediction. The precocious recognition of structural critical states will allow to design repair and strengthening interventions and to prevent total or partial failure of the constructions.     

Master curve of filler localization in rubber blends at an equilibrium state

In this study, the phase-specific localization of filler in NBR/NR blends was characterized by means of the selective extraction method and wetting concept. A strong dependence of silica localization on the filler loading was found. A model based on thermodynamic data was proposed for a quantitative prediction of filler localization in rubber blends. The filler localization can be described by a master curve demonstrating a characteristic behavior in dependence on the filler surface tension data of blend components and filler. The effect of filler loading on the silica localization is sufficiently explained by this model by taking into consideration the deactivation of the silanol groups on the silica surface by adsorbed curing additives. Using the master curve, the surface tension of filler affected by curing additives and silane addition can be estimated that may be useful for evaluation and comparison of the effect of different coupling agents. Surface tension values of different fillers were estimated by means of the master curve and they lie in the same order compared to those reported in literature. A potential transfer of filler within a rubber blend can be also quantitatively predicted.     

Spark Plasma Sintering as a Useful Technique to the Nanostructuration of Piezo‐Ferroelectric Materials

This review gathers detail on the processing of piezo‐ferroelectric ceramic materials by spark plasma sintering for the first time. The results reported here clearly indicate that it is a powerful technique and opens the possibility of processing ceramics with controlled sub‐micron or even nanoscale grain sizes.     

利用主烧结曲线和Arrhenius曲线确定TiO_2陶瓷表观激活能

表观烧结激活能是研究陶瓷烧结机理的一个非常重要参量。采用纳米金红石相TiO2陶瓷坯体在空气中进行无压烧结,加热速率分别为1,2,5℃/min,用热膨胀仪记录试样收缩率,阿基米德法测量烧结体相对密度,分别用主烧结曲线法和Arrhenius法计算表观烧结激活能。结果表明:用主烧结曲线得到的激活能是一个定值,而用Arrhenius法得到的激活能是一个变化的值,激活能是相对密度的函数,随相对密度的增加而减小,且激活能和相对密度的变化趋势分成两段,当相对密度大于85%时,激活能随相对密度的增加而减小比小于85%时要快,这意味着在烧结过程中,控制烧结的扩散机制可能发生了变化。     

Multivariate curve resolution applied to infrared reflection measurements of soil contaminated with an organophosphorus analyte

Multivariate curve resolution (MCR) is a powerful technique for extracting chemical information from measured spectra of complex mixtures. A modified MCR technique that utilized both measured and second-derivative spectra to account for observed sample-to-sample variability attributable to changes in soil reflectivity was used to estimate the spectrum of dibutyl phosphate (DBP) adsorbed on two different soil types. This algorithm was applied directly to measurements of reflection spectra of soils coated with analyte without resorting to soil preparations such as grinding or dilution in potassium bromide. The results provided interpretable spectra that can be used to guide strategies for detection and classification of organic analytes adsorbed on soil. Comparisons to the neat DBP liquid spectrum showed that the recovered analyte spectra from both soils showed spectral features from methyl, methylene, hydroxyl, and P=O functional groups, but most conspicuous was the absence of the strong PO-(CH2)3CH3 stretch absorption at 1033 cm(-1). These results are consistent with those obtained previously using extended multiplicative scatter correction.     

小波变换在可调谐半导体激光器模跳变检测中的应用

利用小波变换的局部化性质分析出拍频信号的奇异点,从而找出半导体激光器电流调制时的模跳变位置,简化了半导体激光器参数测量.     

CoMnNiO超微细粉体的合成及烧结特性

以醋酸盐为原料，用喷雾热分解方法（ＥＤＳ）合成了粒径小于３０ｎｍ的ＣｏＭｎＮｉＯ纳米粉体。粉体压片后，在６００～１０００℃温区处理，ＸＲＤ谱观察了烧结体的不同温度下的晶粒尺寸和相变。烧结体断层的ＳＥＭ观察表明，纳米粉体的烧结体制不同于常规氧化物粉体，纳米粉体中颗粒的亚结构对烧结过程有显著影响。     

Sintering behavior and dielectric properties of Ce doped strontium barium niobate ceramics with silica sintering additive

Sr_0.5Ba_0.5Nb₂O₆ ceramics with and without CeO₂ dopant were prepared by a partial co-precipitation method and a liquid phase sintering process. The cooperative effects of Ce doping and silica sintering additive on the sintering behaviors and the dielectric properties of Sr_0.5Ba_0.5Nb₂O₆ ceramics was investigated. It was observed that the lattice parameters of a-axis and c-axis of Sr_0.5Ba_0.5Nb₂O₆ ceramics decrease with the increase of Ce dopant, namely contraction of crystal cell volume occurs. Amorphous silica used for sintering additive can effectively restrain abnormal grain growth and prevent the rise of sintering activation energies caused by Ce doping, but Ce doping has more effect on the average size of the grains and the dielectric properties than the silica sintering additive when the Ce dopant and the silica sintering additive are introduced. Both the Curie temperatures and the maximum of dielectric constant at Tc decrease as the Ce³⁺ concentration increases.     

齿轮啮合分离测试技术中的测量齿轮误差修正

本文介绍齿轮啮合分离测试技术的测量齿轮误差修正技术，它运用最小区域法计算测量齿轮的压力角和螺旋角误差对其进行修正，利用切比雪夫多项多拟合测量齿轮的形状误差进行修正，试验结果表明修正技术可大大降低了测量齿轮精度要求，能使工作的配对件作为测量齿轮。