Properties of the Interfacial Transition Zone in Model Concrete

The interfacial transition zone (ITZ) between aggregates and cement paste in cementitious materials is a crucial element in mechanical and transport systems. Computer simulation by the SPACE system is used to approach this problem in the present paper. For the particle-packing phenomenon in the fresh state of concrete, the SPACE system relies on a dynamic generation algorithm, reflecting the production conditions of concrete. Hence, structure of the model cement has been proven more realistic than can be achieved by random generator-based system.A natural phenomenon in the ITZ around aggregate particles is size segregation leading to different gradients in porosity, particle size and surface area. Size segregation implies the difference size fractions in the binder mixture to have peak values in their densities on different distances from the aggregate surface. Structural evolution of the ITZ is stereologically quantified with the help of composition and configuration parameters in the fresh and hardened states of concrete.The addition of mineral admixtures is a successful approach to improving the ITZ microstructure. Experiments demonstrated the blending efficiency to be higher for coarser grained Portland cement (PC), due to the positive effect exerted by gap grading, i.e. by having distinctly different size ranges of particles. This is confirmed by computer simulation of the ITZ microstructure in model concretes made with blended cements. In addition, it is very important in concrete production to achieve good workability conditions to ensure sufficient dispersion of the fine rice husk ash (RHA) particles and proper migration of them into the ITZ through the structure network of large cement particles.     

Effect of Some Aromatic Admixtures on the Raman Line Intensity of Solid Cyclohexane at 77 K

The dependence of the intensity of Raman line components of E_g symmetry of cyclohexane, frozen rapidly down to 77 K, on the concentration of admixtures of benzene or naphtalene was studied quantitatively. The admixture of benzene was found to facilitate to a larger extent the overcooling of phase I of solid cyclohexane than admixture of naphtalene.     

The Interfacial Transition Zone (ITZ) Between Cement Paste and Aggregate in Concrete

This paper describes the so called interfacial transition zone—ITZ—in concrete. This is the region of the cement paste around the aggregate particles, which is perturbed by the presence of the aggregate. Its origin lies in the packing of the cement grains against the much larger aggregate, which leads to a local increase in porosity and predominance of smaller cement particles in this region. The ITZ is region of gradual transition and is highly heterogeneous, nevertheless the average microstructural features may be measured by analysis of a large numbers of backscattered electron images of polished concrete samples. Such measurements show that the higher porosity present initially is significantly diminished by the migration of ions during hydration.     

In-Situ Intrinsic Interface Strength Measurement at Elevated Temperatures and its Relationship to Interfacial Structure

A previously developed laser spallation technique has been modified to measure the tensile strength of thin film interfaces in-situ at temperatures up to 1100°C. Tensile strengths of Nb/A-plane sapphire, FeCrAl/A-plane sapphire and FeCrAlY/A-plane sapphire were measured up to 950°C. The measured strengths at high temperatures were substantially lower compared with their corresponding strengths at ambient temperature. For example, at 850°C, the interface tensile strength for the Nb/sapphire (151 ± 17 MPa), FeCrAl/sapphire (62 ± 8 MPa) and FeCrAlY/sapphire (82 ± 11 MPa) interface systems were lower by factors of approximately, 3, 5, and 8, respectively, over their corresponding ambient values. These results underscore the importance of using such in-situ measured values under operating conditions as the failure criterion in any life prediction or reliability models of such coated systems where local interface temperature excursions are expected. The results on alloy film interfaces also demonstrate that the presence of Y increases the strength of FeCrAl/Al₂O₃ interfaces.     

Influence of the Interfacial Characteristics on the Tribological Behaviour of TiN-Base Films on Iron

The dry sliding behaviour of TiN-base films deposited onto a tool steel by two different physical vapour deposition techniques is discussed on the basis of the characteristics of both coatings and interfacial regions. It is shown that film adhesion is determining for the wear resistance. Other important factors are the film hardness and the intensity of the stress state at the film-substrate interface.     

矿物掺合料作为砂浆细集料的水化产物与光谱性能研究

粉煤灰、锂渣和钢渣作为工业废渣,等质量替代水泥时其利用率往往较低,为了大量地使用这些工业废渣。采用X射线单晶衍射仪、同步热分析仪、傅里叶红外光谱仪和电镜扫描分析方法,研究了锂渣、粉煤灰和钢渣替代细集料后砂浆的水化产物、光谱特性、微观形貌,并探讨了砂浆抗折/抗压强度随替代率(0%,30%,50%,70%和100%)增长的变化规律。研究结果表明：四种浆体的水化产物主要为CSH凝胶、Ca(OH)₂、少量的AFt和未水化的颗粒(Al₂O₃,SiO₂),其中水泥-锂渣浆体、水泥-粉煤灰浆体、水泥-钢渣浆体中的未水化颗粒还含有一定的Li₂O·Al₂O₃·SiO₂,Ca_1.56SiO_3.5·xH₂O和RO phas。四种浆体以3 467,3 438,2 923,2 348,1 638,1 429,1 111,1 000,768,696和462 cm-1为特征峰,但其峰强有所不同,其活性也不同,参与二次水化反应的程度也不同,因此,水泥-钢渣浆体中Ca(OH)₂的含量明显高于水泥-粉煤灰浆体和水泥-锂渣浆体的现象;但不管是矿物掺合料替代水泥还是细集料,都在浆体中发挥着火山灰活性和填充作用。含三种100%矿物掺合料砂浆的抗折强度和抗压强度均高于纯水泥砂浆,分别(锂渣、粉煤灰和钢渣)约高37.77%/51.88%,14.71%/11.70%,91.95%/34.88%,但其达到峰值的掺量不同。因此,采用矿物掺合料替代细集料是可行的,能大幅度提高工业废渣在混凝土行业中的使用,且能达到节能减排的效果。     

The Evolution of Interfacial Strength as a Way to Characterize a Low-Temperature Limit of the Surface Glass Transition of an Amorphous Polymer

The evolution of autoadhesive strength, σ, with healing temperature, T _h, at the symmetric amorphous polystyrene (PS)?PS interfaces of the samples with vitrified bulk has been used to characterize a low-temperature limit of the surface glass transition temperature T _g ^surface(low). The existence of a linear relationship between the square root of σ and T _h has been found for both polydisperse and monodisperse polymers. By the extrapolation of straight lines σ ^1/2 ? T _h to σ ^1/2 = 0, the values of T _g ^surface(low) have been determined and compared with those of a high-temperature limit of T _g ^surface, T _g ^surface(high), measured earlier. The differences between T _g ^surface(low) and T _g ^surface(high) have been found to be insignificant, 10–20°C. Using an average value of the shift of T _g ^surface(low) with healing time, t _h, the quasi-equilibrium value of the surface glass transition temperature of amorphous PS T _∞ ^surface has been estimated to be 10–15°C.     

An Analysis of the Transition Zone Between the Various Scaling Regimes in the Small-World Model

We analyse the so-called small-world network model (originally devised by Strogatz and Watts), treating it, among other things, as a case study of non-linear coupled difference or differential equations. We derive a system of evolution equations containing more of the previously neglected (possibly relevant) non-linear terms. As an exact solution of this entangled system of equations is out of question we develop a (as we think, promising) method of enclosing the “exact” solutions for the expected quantities by upper and lower bounds, which represent solutions of a slightly simpler system of differential equation. Furthermore we discuss the relation between difference and differential equations and scrutinize the limits of the spreading idea for random graphs. We then show that there exists in fact a “broad” (with respect to scaling exponents) crossover zone, smoothly interpolating between linear and logarithmic scaling of the diameter or average distance. We are able to corroborate earlier findings in certain regions of phase or parameter space (as e.g. the finite size scaling ansatz) but find also deviations for other choices of the parameters. Our analysis is supplemented by a variety of numerical calculations, which, among other things, quantify the effect of various approximations being made. With the help of our analytical results we manage to calculate another important network characteristic, the (fractal) dimension, and provide numerical values for the case of the small-world network.     

Interfacial properties of a driven diffusive system

A study is made of the low-temperature interfacial properties of a driven system with a single conserved density whose bulk properties were first analyzed, using computer simulations, by Katz, Lebowitz, and Spohn in 1983. The system corresponds to a nearest neighbor interacting lattice gas of charged particles (henceconserved order parameter), which are acted upon by a uniform, constant external electric fieldE. Starting from a bulk kinetic equation, an integral equation for the interface is derived. Nonlocal coupling between different parts of the interface arises from local particle conservation. The interface at any angle is shown to be stable against small deformations ofall wavelengths that are large compared to the interfacial width. However, the relaxation rate(k) for the interface exhibits a strongorientational dependence, which can be understood in terms of the modification of nonlocality byE. The wandering of the interface is considered. Also, the possible stabilizing effect of periodic boundary conditions on the orientation toward the direction ofE is discussed.     

Transition to Chaos in the Floating Half Zone Convection

The transition process from steady convection to chaos is experimentally studied in thermocapillary convections of floating half zone. The onset of temperature oscillations in the liquid bridge of floating half zone and further transitions of the temporal convective behaviour are detected by measuring the temperature in the liquid bridge. The fast Fourier transform reveals the frequency and amplitude characteristics of the flow transition. The experimental results indicate the existence of a sequence of period-doubling bifurcations that culminate in chaos. The measured Feigenbaum numbers are δ2 =4.69 and δ4 = 4.6, which are comparable with the theoretical asymptotic value δ=4.669.     

Influence of Grafting Density of Diblock Copolymers on Interfacial Assembly Behavior and Interfacial Shear Strength of Glass Fiber/Polystyrene Composites

To investigate the influence of the grafting density and the molecular structure of block copolymers on the interfacial assembly behavior and interfacial shear strength, macromolecular coupling agents, hydroxyl-terminated poly(n-butyl acrylate-b-styrene) (HO-P(BA-b-S)) were synthesized by atom transfer radical polymerization, and then chemically anchored on the glass fiber surfaces to form a well-defined monolayer. The phase separation and 'hemispherical' domain morphologies of diblock copolymer brushes at the polystyrene/glass fiber interface were observed. The interfacial assembly morphology differs with changes in the grafting density of diblock copolymers. When the grafting density is greatest, the highest height difference of the hemispherical domain and the largest surface roughness are achieved, as well as the best interface shear strength. It was also found that the copolymer brush with a PBA block of the polymerization degree (Xn) about 77 is the optimal option for the interfacial adhesion of PS/GF composites. Thus, the grafting density and molecular structure of diblock copolymers determines the interfacial assembly behavior of copolymer brushes, and therefore the interfacial shear strength.     

The Phase Transition in Statistical Models Defined on Farey Fractions

We consider several statistical models defined on the Farey fractions. Two of these models may be regarded as spin chains, with long-range interactions, while another arises in the study of multifractals associated with chaotic maps exhibiting intermittency. We prove that these models all have the same free energy. Their thermodynamic behavior is determined by the spectrum of the transfer operator (Ruelle–Perron–Frobenius operator), which is defined using the maps (presentation functions) generating the Farey tree. The spectrum of this operator was completely determined by Prellberg. It follows that these models have a second-order phase transition with a specific heat divergence of the form C [ ln² ]^–1. The spin chain models are also rigorously known to have a discontinuity in the magnetization at the phase transition.     

Continuum Micro-mechanics of Estimating Interfacial Shear Strength in Short Fiber Composites

A new continuum approach to micro-mechanics of short fiber composites yielded two separate methods of estimating the apparent interfacial shear strength and fiber orientation efficiency. The methods exploit the compilation of the effects of fiber length distribution and interfacial shear strength on strengthening efficiency into a function of strain. The In-Built Method derives a unique combination of apparent interfacial shear strength and fiber orientation efficiency being able to reproduce the experimental stress–strain curve of a short fiber reinforced composite with a very low residual standard deviation. The Boundary Method accomplishes rapid interfacial shear strength screening in materials selection by constructing and utilizing the proposed selection chart.     

Multicomponent Stress–Strength Model Based on Generalized Progressive Hybrid Censoring Scheme: A Statistical Analysis

The statistical inference of the reliability and parameters of the stress–strength model has received great attention in the field of reliability analysis. When following the generalized progressive hybrid censoring (GPHC) scheme, it is important to discuss the point estimate and interval estimate of the reliability of the multicomponent stress–strength (MSS) model, in which the stress and the strength variables are derived from different distributions by assuming that stress follows the Chen distribution and that strength follows the Gompertz distribution. In the present study, the Newton–Raphson method was adopted to derive the maximum likelihood estimation (MLE) of the model parameters, and the corresponding asymptotic distribution was adopted to construct the asymptotic confidence interval (ACI). Subsequently, the exact confidence interval (ECI) of the parameters was calculated. A hybrid Markov chain Monte Carlo (MCMC) method was adopted to determine the approximate Bayesian estimation (BE) of the unknown parameters and the high posterior density credible interval (HPDCI). A simulation study with the actual dataset was conducted for the BEs with squared error loss function (SELF) and the MLEs of the model parameters and reliability, comparing the bias and mean squares errors (MSE). In addition, the three interval estimates were compared in terms of the average interval length (AIL) and coverage probability (CP).     

用光散射研究部分相容聚合物共混物的相间过渡层(英文)

在光散射的理论中 ,密度均方起伏η2在两相完全不相容的体系中 (界面间也不存在相互粘附 )η2 =Φ1Φ2 (α1-α2 )。对于界面间有相互作用或形成一定的相容区时 ,η2将变小 ,则有η2 =(α2 -α1) 2 (φ1φ2 -φ3/6)。α1、α2 为两组元分别的极化率 ,φ1、φ2 为两组元的体积分数。本文根据部分相容的聚合物共混体系中的分散相尺寸γ和积分不变量θ,可计算出φ3,并提出相间弥散层的概念 ,进而计算出弥散层的厚度 d,从而发展了光散射理论。激光小角散射计算的弥散层厚度 d与 X光小角散射计算的界面层厚度σb是相对应的。在计算中应用相关距离 ac代替分散性尺寸γ是可行的 (也可用均方旋转半径 R2g代替 )。文中给出了 PA6/PP合金的弥散层厚度 d和界面层厚度σb的计算结果 ,同时给出了 HIPS/Pc BR合金在熔体动态过程中两相间弥散层厚度的变化     

The Effect of Blood Contamination on the Chemical Characterization of Hydrated Mineral Trioxide Aggregates and Their Dentin-Interface: A Comparative Study

The presence of blood contamination could affect the chemical characterization of mineral trioxide aggregates as endodontic repair material during surgical approach. The aim of this study was to assess and compare the chemical characterization of two white mineral trioxide aggregates (ProRoot and Angelus) mixed with blood versus water. ProRoot and Angelus were mixed with either distilled water, fresh human blood, or diluted blood and analyzed using Fourier transform infrared spectroscopy. The same materials were packed inside holes in dentin blocks for scanning electron microscopy with energy-dispersive X-ray. Gray Portland cement was used as a control. The infrared spectra of unhydrate powders showed an increase in alite in ProRoot and Angelus, belite in Portland cement, and calcium hydroxide in Angelus. Upon hydration, changes in these bands were detected. Energy-dispersive X-ray displayed significantly higher calcium, aluminum, and phosphorous in hydrated Angelus and silicon in hydrated ProRoot (p < 0.05). No phosphorous was detected in ProRoot. Traces of iron were detected in blood groups. A granular pattern was observed at the hydrated material of all tested groups. Definitive gaps were detected at certain areas within hydrated material and its dentin-interface, particularly in blood-contaminated groups. It was supported with the appearance of new bands assigned to Amide I and II of blood protein. It was concluded that the presence of blood during the hydration process of mineral trioxide aggregates produced small gaps of protein impurities within the hydrated material, affecting its chemical behavior and dentin/material-interface integrity.     

Interfacial enhancement of flexible PVC-silica composites by silane coupling agents

Enhancement of a flexible poly(vinyl chloride) (PVC)-silica composite interface was studied by the application of γ-aminopropyltrimethoxysilane on silica. Composites containing silica and silanized silica up to 25.6 phr (per hundred resin) and prepared by sol-gel technology were subjected to water and water vapor attacks similar to that in their daily use. Silane application resulted in diminishing liquid water and water vapor sorption by about 24.0% and 11.9%, respectively. Equilibrium weight gain values of the composites having different amounts of silica correlated well with a peak at 3400 cm^-1 in the IR spectra which was attributed to the stretching vibration of the O-H group of water. Liquid water and water vapor diffusivities in composites determined by the evaluation of weight gain against time data were about 0.4 x 10^-13 and 0.4 x 10^-12 m² s^-1, respectively. Inhibition of dioctyl phthalate (DOP) migration from composites by silane application was also determined as 24% using UV measurements. The most impressive merit of silane enhancement was observed as the retention of ultimate tensile strength (UTS) under wet conditions. While the untreated silica composite reduced its UTS by about 21.2%, silanized silica composite reduced its UTS by only about 13.6%, on wetting.     

Interfacial adhesion of lignocellulosic materials in polymer composites: an overview

Cellulosic materials have long been used as cost-cutting fillers in the plastic industry. Among the various factors which determine the final performance of the composite materials depend, to a large extent, on the adhesion between the polymer matrix and the reinforcements, and, therefore, on the quality of the interface. In fact, the majority of cellulosic raw materials are lignocellulosics of different polarity to plastics, and due to this divergent behavior, the adhesion between cellulosic materials and polymer matrices is very poor. However, a sufficient degree of interaction or adhesion between the surface of the cellulosic materials and matrix resin is usually desired to achieve an optimum performance of the end-product. In many cases surface modification of the cellulosics or the matrix resins, using various additives, vinyl monomers, or coupling agents, are considered to be essential to achieve this goal. The present paper surveys research work published in this field with special emphasis on the cellulosic materials' surface chemistry, morphology, as well as interfacial properties of the composites in order to elucidate the role of surface treatments. In order to elucidate the mechanism of interaction on molecular level, it is necessary to employ various techniques, such as spectroscopy that can measure surface events. In fact, the complexity of the interphase region requires a variety of characterization methods for the thorough understanding of the physical and chemical nature of this region. Moreover, a proper combination of different techniques is necessary to provide a true picture of the interphase.     

入射光单色性与界面粗糙度对多层膜反射性能的不同影响

多层膜界面粗糙度、入射光单色性对软X射线多层膜实际反射率均有影响。利用数学卷积积分,理论上推导出一个在入射光不同单色性下精确计算多层膜反射率的公式。利用给出的理论计算公式,简要分析了入射光不同单色性、不同界面粗糙度对Mo/Si多层膜反射率的影响。理论分析发现这两种因素对Mo/Si多层膜反射率影响完全不同:入射光低的单色性不但极大降低Mo/Si多层膜峰值反射率,而且使反射曲线的半峰全宽增加;而界面粗糙度是降低Mo/Si多层膜反射曲线上各点对应值,基本不改变Mo/Si反射曲线的半峰全宽,不改变反射曲线的形状。说明这两个因素在软X射线的长波段对多层膜反射性能的影响不同。