Porous Inclusions Research Articles

Influence of non-conducting pore inclusions on phase change behavior of porous media with constant heat flux boundary

A one-dimensional analytical solution was presented for the temporal variation of phase interface in two-phase materials having randomly distributed stagnant low conducting pores with constant heat flux boundary. For validation, numerical simulations based on the finite difference method were conducted. It was demonstrated that the phase interface propagates faster with pore inclusion than that associated with constant wall temperature boundary. Such faster movement of the phase interface is attributed to the decreased effective density of the medium as a result of the included low conducting pores. The decreased effective density reduces the amount of latent heat of the medium whilst the amount of heat removed at the boundary remains constant. Therefore, at a given period of time, more latent heat is liberated. In addition, for a given porosity, the influence of pore shape upon phase change interface location is negligible since the effective conductivity, although varying considerably with pore shape, has a marginal effect on the behavior of phase change interface.

Special Section on Advances in Internally Cured Concrete

Special Section on Advances in Internally Cured Concrete

INFLUENCE OF DIFFERENT LOADS ON THE PROPERTIES OF LIGHTWEIGHT COMPOSITE

The paper describes the study on the operational properties of lightweight composite with density of 150–350 kg/m3. It was established that these properties depend on the ratio of porous cement matrix and inclusions of crushed expanded polystyrene packing tare waste per unit volume of the lightweight composite. Studies have demonstrated that when the density of lightweight composite varies in the above mentioned limits, the compressibility amounts to 2.4–0.8 mm, point load – 0.38–3.39 kN, dynamic stiffness – 35–135 MN/m3, and reduction in normalised impact sound pressure level – 26–17 dB. The dependences between the established properties and the density of lightweight composite are showed in the equations of regression. Possible versions for the use of lightweight composite in different constructions of floors and roofs are also provided.

Using Isothermal Calorimetry to Assess the Water Absorbed by Fine LWA during Mixing

AbstractFine lightweight aggregate (LWA) is being increasingly used for the manufacture of internally cured concrete. Internally cured concrete can be viewed as a concrete that contains fluid (water) in the pores of the LWA (or other porous inclusions) that can be released to the paste after setting. Most research performed on internally cured concrete assumes the LWA has been prewetted for some time before mixing (generally lab studies use 24-h soaking, whereas this value varies in practice). The research described in this paper investigated the potential for using aggregate that begins the mixing process from a different moisture state (i.e., not 24-h prewetting). Specifically, this paper considers oven-dry aggregate as a worst-case scenario to determine how much water would be absorbed by the LWA during the mixing and placement processes. To determine the amount of water absorbed by the LWA, isothermal calorimetry was used. Two different mixing scenarios were investigated, showing that 56–71% of the 24...

Experimental estimation of the transmission loss contributions of a sound package placed in a double wall structure

The objective of this paper is to propose a practical impedance tube method to optimize the sound transmission loss of double wall structure by concentrating on the sound package placed inside the structure. In a previous work, the authors derived an expression that breakdown the transmission loss of a double wall structure containing a sound absorbing blanket separated from the panels by air layers in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The sound transmission loss contributions of the blanket can thus be estimated from three acoustic measurements using impedance tube techniques: two reflection coefficients at the front face and the rear face of the blanket placed in specific positions characteristic of its position inside the double wall structure and its sound transmission coefficient. The method is first validated in the case of a double wall structure filled with a 2 in. foam material. Next, it is applied to investigate (i) the effect of frame compression of a 2 in. fibre glass in an aeronautic-type double wall structure and (ii) the effect of double porosity with or without porous inclusions in a building-type double wall structure.

On effective characteristics of wave propagation in a porous fluid-saturated medium containing entirely fluid inclusions

SUMMARY To investigate the behaviour of seismic wave propagation in natural rocks and soils, a model for the elastic properties of a heterogeneous porous medium containing uniform fluid inclusions is useful. The problem has already been addressed before, utilizing Biot’s theory of poroelasticity, and there have been some analytical and numerical results obtained for the different types of cavities. However, as it is shown in this paper, immediate passage within heterogeneous porous media from spherical porous heterogeneities to continuous fluid or solid inclusions cannot be performed on the basis of previously developed models. In this paper, we extend the results for wave scattering in porous media due to a random ensemble of spherical porous inclusions to allow for continuous fluid inclusions instead. To consider this case, we first obtain the single scattering series. Then we utilize multiple scattering theory to find the effective wavenumber due to an ensemble of inclusions. Our results make it possible to analyse wave attenuation and velocity dispersion at low frequencies due to the presence of entirely fluid inclusion heterogeneities within a porous material. Explicit analytical expressions for solution of single scattering problem for a fluid cavity, and effective propagation velocity and attenuation factor in a porous medium with random ensemble of these cavities constitute main results of this work.

Extension of Double Porosity Model to Porous Materials Containing Specific Porous Inclusions

Extension of Double Porosity Model to Porous Materials Containing Specific Porous Inclusions

On the use of porous inclusions to improve the acoustical response of porous materials: Analytical model and experimental verification

Acoustical composite materials obtained through a set of porous inclusions are studied. A theoretical model based on the homogenization hypotheses introduced by Boutin et al. [1] is presented; the inclusions are supposed periodic and the frame rigid. The idea behind the inclusion of a second acoustical porous material into the original single porosity material, is to obtain the pressure diffusion effect already observed in the double porosity case. At the same time, the main disadvantages of double porosity are faced, especially the absorption behavior at very low frequency and the loss of performances in transmission. Experimental data are obtained in Kundt Tubes of different dimensions in terms of absorption curves and compared to analytical results for representative configurations, thus validating the theoretical model.

Supramolecular interactions and structural transformations in the metal-organic sorbent-acetone nanoreactor system

By the 1H NMR and Raman spectroscopy data it is shown that in the porous inclusion compound of Zn2(C8H4O4)2[(N2(CH2)6))]·n(CH3)2CO (n ≈ 0–4.7) acetone molecules exist in two structural forms: ketonic (CH3)2CO, for which the 1H NMR chemical shift value is δket = 0.8 ppm, and enolic CH3C(O)=CH2, for which δen(OH) = 11 ppm, δen(CH2) = 8.9 ppm, and δen(CH3) = 1.6 ppm are found, the average value over three proton sites being = 5.6 ppm. A sharp difference in chemical shift values for the keto and enol forms of acetone in the inclusion compounds can be assigned to the effect of structural chemical conditions in two types of adsorption centers.

Advanced metal powder based manufacturing of complex components by electron beam melting

Electron beam melting of Ti–6Al–4V powder (∼30 μm diameter) to create complex, three-dimensional components layer by layer using CAD is described along with the characterisation of these products (builds) by optical and electron microscopy, and mechanical testing. Build defects, including porous (unmelted or unsintered) zones, inclusions and gas bubbles trapped in the atomised powder particles and retained in the build, are illustrated. Reticulated mesh geometries and their applications are described along with examples having biomedical applications. Microstructures of solid components and mesh arrays are described. Powder chemistries and solid build chemistries are also examined and shown to be constant for up to 40 cycles of powder reuse, but there was a 10–15% reduction in Al content in the solid builds at optimised build conditions. Quality control and related issues are also described using duplicate products for destructive testing correlated with removable quality control tabs on the builds.

Sodium-metasomatism of Ca-Al-rich inclusions in the anomalous carbonaceous chondrite Ningqiang

A petrographic and mineralogical study of Ningqiang reveals that a significant proportion of the Ca-Al-rich inclusions (CAIs) consist entirely of fine-grained porous aggregates, and melilite in them has been extensively replaced by nepheline. Small fragments of nepheline-bearing inclusions and fine nepheline grains are widely scattered in the matrix. We found evidence suggesting that those fine-grained porous inclusions were formed by replacing primary Type A CAIs and spinel-pyroxene type CAIs. The results suggest that Ningqiang has experienced extensive Na-metasomatism on its parent body. In that process, part of CAIs became fine-grained porous, and during subsequent brecciation, they were disaggregated and segregated from the original portion in the parent body. We infer that these processes may be responsible for the low abundances of CAIs and bulk refractory lithophiles that are characteristic of Ningqiang.

Elastic behavior of composites containing Boolean random sets of inhomogeneities

The overall mechanical response as well as strain and stress field statistics of an heterogeneous material made of two randomly distributed, linear elastic phases, are investigated numerically. The Boolean model of spheres is used to generate microstructures consisting of either porous or rigid inclusions, at any volume fraction of the phases. Stress and strain field integral ranges, or equivalently the representative volume element, are computed and linked to features of the field statistics, and to the microstructure geometry.

The role of surface tension in elastic wave scattering in an inhomogeneous poroelastic medium

It is well known that many porous media such as rocks have heterogeneities at nearly all scales. We applied Biot's poroelastic theory to study the propagation of elastic waves in isotropic porous matrix with spherical inclusions. It is assumed that the heterogeneity dimension exceeds significantly the pore size. Modified boundary conditions on poroelastic interface are used to take into account the surface tension effects. The effective wavenumber is calculated using the Waterman and Truell multiple scattering theory, which relates the effective wave number to the amplitude of the wave field scattered by a single inclusion. The calculations were performed for a medium containing fluid-filled cavities or porous inclusions contrasting in saturating fluid elastic properties. The results obtained show that when we consider elastic wave propagation in poroelastic medium containing soft inclusions, it is necessary to take into account the capillary pressure. The influence of the surface tension depends on the diffraction parameter and it is a maximum in the low frequency range.

Evaluation of the thermal comfort of ceramic floor tiles

In places where people are bare feet, the thermal sensation of cold or hot depends on the environmental conditions and material properties including its microstructure and crustiness surface. The uncomforting can be characterized by heated floor surfaces in external environments which are exposed to sun radiation (swimming polls areas) or by cold floor surfaces in internal environments (bed rooms, path rooms). The property named thermal effusivity which defines the interface temperature when two semi-infinite solids are putted in perfect contact. The introduction of the crustiness surface on the ceramic tiles interferes in the contact temperature and also it can be a strategy to obtain ceramic tiles more comfortable. Materials with low conductivities and densities can be obtained by porous inclusion are due particularly to the processing conditions usually employed. However, the presence of pores generally involves low mechanical strength. This work has the objective to evaluate the thermal comfort of ceramics floor obtained by incorporation of refractory raw materials (residue of the polishing of the porcelanato) in industrial atomized ceramic powder, through the thermal and mechanical properties. The theoretical and experimental results show that the porosity and crustiness surface increases; there is sensitive improvement in the comfort by contact.

SPH as an Inverse Numerical Tool for the Prediction of Diffusive Properties in Porous Media

Heat and mass transfer and fluid flow in porous media are usually characterized by, or associated with, the effective thermal conductivity, the effective mass diffusivity and the permeability, respectively. All these macroscopic quantities are conceptually established on a phenomenological “equivalence” basis. They may contain the influence of porous micro-structures upon the corresponding diffusive process; however, the detailed nature inside the porous medium is lumped and neglected. Pore scale numerical modelling has the potential of providing adequate meso-/micro- scale insight into the transport process in porous medium, as well as obtaining macroscopic properties, which can encompass the complex pore-structure details. Modelling heat/mass transfer and fluid flow in complicated porous micro-structures presents a major challenge to numerical methods due to their multiscale and multiphysics nature. A relatively-novel numerical technique - the meshless Lagrangian-based Smoothed Particle Hydrodynamics (SPH) method is thought to be capable of making a significant contribution to this research field. This work deals primarily with the SPH modelling of heat conduction and fluid flow in 2-D isotropic porous media. The porous matrix is formed by randomly including a different component into a base component. Various pore-structures are realized by changing the inclusion shape/size, or the relative arrangement condition between inclusions. Pore-scale heat transfer and fluid flow streams are visualized, and both heat transfer and fluid flow always follow, as expected, the paths of least resistance through the porous structures. In what concerns the effective thermal conductivity, for the porous media with the base component of larger bulk thermal conductivity, the “flexible” EMT model, which can accommodate, to some extent, the influence from the porous micro-structures on the effective thermal conductivity by adjusting the so-called flexible factor ff, gives effective thermal conductivities agreeable to the SPH predictions across the whole composition range if ff is taken to be ~ 4.5; the effective thermal conductivity shows a weak dependence on the inclusion shape/size and the relative arrangement condition between inclusions; however, for porous media with dispersed inclusions, which component has larger bulk thermal conductivity presents a strong effect upon the effective thermal conductivity. The SPH fluid flow simulation results confirm the macroscopic Darcy’s law to be valid only in the creeping flow regime; the dimensionless permeability (normalized by the squared characteristic dimension of the inclusions) is found to have an exponential dependence on the porosity within the intermediate porosity range, and the derived dimensionless permeability /""porosity relation is found to have only a minor dependence on either the relative arrangement condition between inclusions or the inclusion shape/area.

Advanced Coatings on Furnace Wall Tubes

Nickel-based self-fluxing alloy coating extends the service life of furnace wall tubes at waste incineration plants due to its excellent corrosion resistance and heat resistance. Fusing of such coatings by induction heating offers improved efficiency and reliability of products. Compared with conventional plasma, flame, and high-velocity oxy-fuel spraying thermal-sprayed coatings, induction-fused coatings provide a far stronger metallurgical bond at the interface, while minimizing the inclusion of pores. In addition, the tubes are less costly than those with welded coatings, and the process reduces the distortion of the products, facilitating easier final assembly. A successful experimental application of 11 units in a waste incinerator revealed virtually no corrosion on the exposed surfaces, and showed an improved water heating efficiency over that of the original tubes. Such units are now being employed in four incinerators in Taiwan, and continuing tests are showing great promise.

Upscaling Forchheimer law

We investigate the high velocity flow in heterogeneous porous media. The model is obtained by upscaling the flow at the heterogeneity scale where the Forchheimer law is assumed to be valid. We use the method of multiple scale expansions, which gives rigorously the macroscopic behaviour without any prerequisite on the form of the macroscopic equations. We show that Forchheimer law does not generally survive upscaling. The macroscopic flow law is strongly non-linear and anisotropic. A 2-point Pade approximation of the flow law in the form of a Forchheimer law is given. However, this approximation is generally poor. These results are illustrated in two particular cases: a layered composite porous media and a composite constituted by a square array of circular porous inclusions embedded in a porous matrix. We show that non-linearities are sources of anisotropy.

Effect of CO2 Gasification on the Transformations of Coke Minerals at High Temperatures

Mineral phases of three metallurgical cokes were characterized after reactions with CO2 at 1373 and 1773 K in a horizontal furnace for 2 h using X-ray diffraction (XRD) and scanning electron microscope/energy dispersive spectroscopy (SEM/EDS). After reaction at 1373 K, all cokes displayed an increased degree of mineral decomposition, dissemination within the carbon matrix, and inclusions in pores such that the intensity of transformation varied with coke types. As for the original cokes, XRD analysis of the reacted cokes indicated the presence of quartz, mullite, and high melting point aluminosilicate as the major refractory phases while pyrrhotite, triolite, iron oxides, and metallic iron phases were the main reactive phases. Framboidal sulfide appeared to diminish after CO2 reactions. Iron-spinel was the common reaction product while olivine was observed in only one coke. All minerals occurred in a wide variety of sizes and distributions such that fine minerals occurred mainly within or close to pores and were comprised of iron sulfide and Al2O3. At 1773 K, aggregates of Al-silicates decomposed further to form mullite and cristobalite while low melting point Al-silicates transformed to running slag in coke. Iron was observed to occur in many forms including metallic iron, silicates, and oxides but less frequently as sulfides and appeared to occur within or in close proximity to pores. At 1773 K, pore inclusions were the prominent features of the reacted cokes, particularly a high proportion of Al2O3 (corundum). Calcium was observed as silicates as well as thermally stable phosphate and sulfides. This study demonstrated that characteristics of coke minerals after reactions at standard coke strength after reaction (CSR) test temperatures of 1373 and 1773 K were significantly different in terms of phase distribution which would influence coke strength and reactivity accordingly. This study implies that coke properties measured at relatively lower temperatures in the conventional tests may not provide a true assessment of coke performance in an operating blast furnace.

The effect of nonhydrostaticity on elastoplastic compaction and decompaction

The paper is devoted to the modeling of processes of inelastic nonhydrostatic compaction and decompaction of low porosity geomaterials such that each pore can be considered as an isolated cavity in a solid matrix. A real material containing a large number of noninteracting pores is replaced at a microscopic level by an equivalent homogeneous medium containing a single pore inclusion. Attention is paid to the case where cylindrical pores oriented perpendicularly to an applied nonhydrostatic load are present in the material. Along with the elastoplastic response of the medium, viscous effects are considered. The effect of shear stresses on compaction and decompaction of porous geomaterials is studied. The dependence of effective material parameters on the properties of components is examined.

Structural Transformation in PECVD Ultralow-k Material during Porogen Removal by UV Assisted Thermal Curing

ABSTRACTNext-generation microelectronic interconnects require the use of dielectrics with continuously lower permittivity (k) to overcome limitations induced by crosstalk parasitic signal delay. Using PECVD, Ultralow-k film (ULK, k ≤ 2.5) can be developed by creating pore inclusions within an organosilicate matrix through porogen approach. Both ULK deposition and subsequent curing process has to be adjusted in order to achieve optimized mechanical and electrical properties and maintain stability during integration. For this concern, the attention was recently focused on ultraviolet (UV) radiation to sustain the thermal curing. In the present work, a fundamental understanding of structural transformations occurring during porogen extraction from as-deposited ULK materials when exposed to thermal-assisted UV radiation is proposed. This thermal-assisted UV cure technique is very efficient in porogen removal since in a few minutes the desired porosity is reached. During the first stage of curing, the film shrinks strongly whereas the porosity is created. After porogen removal step, the porous film continues shrinking under UV radiation leading to an increase of SiOSi bonds concentration (film densification). The normalized FTIR SiOSi peak increase during UV curing (related in literature to an improvement of mechanical properties) is mainly due to the film densification, in addition to the SiOSi bridging bond creation. In this case, correlation is found between shrinkage and elastic modulus.