Depth-Resolved Porosity Investigation of EB-PVD Thermal Barrier Coatings Using High-Energy X-rays

Demands for designing prime reliant, energy-efficient, and high-performance thermal barrier coatings (TBCs) in gas turbines have led to a growing interest toward comprehensive microstructural characterization. Here we investigate the novel use of high-energy X-rays for small-angle X-ray scattering (SAXS), together with wide-angle scattering and radiography, for the depth-resolved characterization of TBCs grown by electron beam physical vapor deposition (EB-PVD). The coating microstructure is found to consist of columns perpendicular to the substrate, extending through the thickness, with a [001] growth texture and significant intercolumnar porosity. In addition, overshadowing effects during deposition together with gas entrapment give rise to nanoscale intracolumnar porosity consisting of featherlike and globular pores. Radiography showed an increase in the total porosity, from 15% near the substrate to 25% near the coating surface, which is ascribed to an increase in the intercolumnar spacing at the top of the coating. By contrast, the small-angle scattering studies, which are sensitive to fine features, showed the pore internal surface area to be greatest near the substrate.     

Preparation of a Translucent, Conductive, Porous Nanocomposite

A translucent, conductive, porous nanocomposite was designed and prepared by depositing SnO₂ on the inner surfaces of the pores of a porous glass plate and on its outer surface using a chemical vapor deposition method. The porous nanocomposite almost maintained its large surface area and pore volume because the pores remained open after they were deposited with SnO₂. Conductivity between the two outer surfaces of the nanocomposite plate was confirmed for the first time.     

Propagation of Love waves in an elastic layer with void pores

The paper presents a study of propagation of Love waves in a poroelastic layer resting over a poro-elastic half-space. Pores contain nothing of mechanical or energetic significance. The study reveals that such a medium transmits two types of love waves. The first front depends upon the modulus of rigidity of the elastic matrix of the medium and is the same as the love wave in an elastic layer over an elastic half-space. The second front depends upon the change in volume fraction of the pores. As the first front is well-known, the second front has been investigated numerically for different values of void parameters. It is observed that the second front is many times faster than the shear wave in the void medium due to change in volume fraction of the pores and is significant     

靖安油田延长组低孔低渗储层的扫描电镜研究

本文以靖安油田延长组储层为研究对象，通过扫描电镜、X射线能谱及光学显微镜、X射线衍射等，对碎屑岩储层的岩性、孔隙及成岩作用进行了分析。储层岩石类型主要为岩屑质长石砂岩和长石砂岩组成。储层孔隙类型以原生粒间孔隙和次生溶蚀孔隙为主。成岩作用有压实作用、胶结作用和溶蚀作用。压实作用和胶结作用是导致储层低孔低渗的主要原因。溶解作用所形成的次生孔隙改善了储层的性能。     

Inkbottle Pore-Method: Prediction of hygroscopic water content in hardened cement paste at variable climatic conditions

The aim of this work is the development of a practicable method for the reliable prediction of the equilibrium hygroscopic water content in hardened cement paste and cement mortars at changing climatic conditions. Sorption thermodynamics and multi-scale pore structure of hardened cement paste build the basis of the new computation procedure. Drying and chemical aging lead to a formation of inkbottle pores. Their influence on sorption behaviour will be considered in particular by including them into the pore model. Experimental data of adsorption, desorption and scanning-isotherms verify the new computation method, which has been called “IBP-Method” (inkbottle pores).     

从微孔洞起始的热冲击裂纹的数值研究——Ⅰ: 热应力分析

陶瓷材料在热冲击荷载作用下的典型破坏模式是裂纹的起始和扩展。当高温的材料或构件突然处于低温环境时,裂纹将由材料或构件的表面开始产生和发展。因此,材料表面及其表面附近的材料微结构对裂纹的起始有着非常重要的影响。实验表明:某些具有微孔洞结构的陶瓷材料比相应的密实材料的抗热冲击性能有所提高,但相关的机制目前还没有得到定量的解释。本文作者利用商业有限元软件ABAQUS,分析了受热冲击表面上的开口微孔洞、处于表面附近的闭口微孔洞周围的热应力场,以及微孔洞的大小、微孔洞与表面的距离对热应力场的影响,其目的是为进一步分析裂纹的起始和扩展做准备。数值结果表明:一般情况下,闭口微孔洞引起的应力集中比开口微孔洞引起的应力集中更为严重,特别当闭口微孔洞与表面之间的距离很小时,和没有微孔洞情况相比,闭口微孔洞引起的最大的应力集中系数超过6。     

Sintering of Platelike Iron(III) Oxide Powders

Packing and sintering of platelike hematite powders were studied with a special emphasis on pore behavior, and the results were compared with those for acicular powders. Platy particles gave a relatively high green density of 65% of the theoretical value, but did not achieve high fired densities. This is in strong contrast to acicular powders, in which high fired densities were reached from a relatively low green density under the same firing conditions. Features observed with platy particles have been interpreted as being due to the wedgelike pores which tend to close at the early stages of densification.     

Calcium Phosphate Bioceramics with Various Porosities and Dissolution Rates

Porous bioceramics, such as hydroxyapatite (HA), tricalcium phosphate (TCP), and biphasic HA/TCP, were fabricated using the polyurethane sponge technique. The porosity of the ceramics was controlled by a multiple coating of the porous body. When a porous body was produced by a single coating, the porosity was ∼90%, and the pores were completely interconnected. When the sintered body was coated five times after the porous network had been made, the porosity decreased to 65%. As the porosity decreased, the strength increased exponentially. The TCP exhibited the highest dissolution rate in a Ringer's solution, and the HA had the lowest rate. The biphasic HA/TCP showed an intermediate dissolution rate.     

Preparation and Properties of Hydroxyapatite Strengthened with a Glass Phase

A method is described for preparing hydroxyapatite strengthened with a glass phase. The properties of the composites obtained containing both biological and synthetic hydroxyapatite are studied. Characteristics of the test materials such as pycnometric density, volumetric porosity, biological solubility, and mechanical strength are determined.     

Effect of Pore–Grain-Boundary Interactions on Discontinuous Grain Growth

Pore behavior as influenced by migration of an abnormal grain boundary was studied. The pore behavior during the discontinuous growth of hot-pressed spinel (MgAl₂O₄) — whether the pore can move attached to the grain boundary — is particularly governed by the pore size and the matrix grain size. These phenomena can be understood from the interaction between the pore and the abnormal grain boundary.