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Porosity
Kinds of Porosity Terms modified by Porosity Selected AbstractsGas breakthrough experiments on fine-grained sedimentary rocksGEOFLUIDS (ELECTRONIC), Issue 1 2002A. Hildenbrand Abstract The capillary sealing efficiency of fine-grained sedimentary rocks has been investigated by gas breakthrough experiments on fully water saturated claystones and siltstones (Boom Clay from Belgium, Opalinus Clay from Switzerland and Tertiary mudstone from offshore Norway) of different lithological compositions. Sand contents of the samples were consistently below 12%, major clay minerals were illite and smectite. Porosities determined by mercury injection lay between 10 and 30% while specific surface areas determined by nitrogen adsorption (BET method) ranged from 20 to 48 m2 g , 1. Total organic carbon contents were below 2%. Prior to the gas breakthrough experiments the absolute (single phase) permeability (kabs) of the samples was determined by steady state flow tests with water or NaCl brine. The kabs values ranged between 3 and 550 nDarcy (3 × 10,21 and 5.5 × 10,19 m2). The maximum effective permeability to the gas-phase (keff) measured after gas breakthrough on initially water-saturated samples extended from 0.01 nDarcy (1 × 10,23 m2) up to 1100 nDarcy (1.1 × 10,18 m2). The residual differential pressures after re-imbibition of the water phase, referred to as the ,minimum capillary displacement pressures' (Pd), ranged from 0.06 to 6.7 MPa. During the re-imbibition process the effective permeability to the gas phase decreases with decreasing differential pressure. The recorded permeability/pressure data were used to derive the pore size distribution (mostly between 8 and 60 nm) and the transport porosity of the conducting pore system (10 -5,10 -2%). Correlations could be established between (i) absolute permeability coefficients and the maximum effective permeability coefficients and (ii) effective or absolute permeability coefficients and capillary sealing efficiency. No correlation was found between the capillary displacement pressures determined from gas breakthrough experiments and those derived theoretically by mercury injection. [source] THE HYDROCARBON POTENTIAL OF LEBANON: NEW INSIGHTS FROM REGIONAL CORRELATIONS AND STUDIES OF JURASSIC DOLOMITIZATIONJOURNAL OF PETROLEUM GEOLOGY, Issue 3 2004F. H. Nader This paper presents an updated review of the petroleum prospects of Lebanon. We briefly describe the known hydrocarbon shows in Lebanon and compare them with adjacent countries, leading to the construction of a model for hydrocarbon migration which takes into account regional facies and reservoir correlations. The oldest exposed rocks in Lebanon are the Jurassic carbonates of the Kesrouane Formation (over 1,000m thick). This formation can be divided into a basal unit dominated by seepage-reflux stratabound dolostones (the Chouane Member,) and an overlying limestone-prone unit (the Nahr Ibrahim Member). A two-stage dolomitisation model for the Jurassic carbonates in Lebanon has recently been proposed by the authors. According to this model, second-stage Late Jurassic hydrothermal dolomitisation is believed to have occurred as a result of the circulation of mixed dolomitising fluids along faults. Hence, the resulting dolostones are fault-controlled and strata-discordant, and may occur at any level within the Kesrouane Formation, locally redolomitising the Chouane Member dolostones and replacing the Nahr Ibrahim Member limestones. In this paper, we discuss the implications of diagenesis (especially dolomitisation) on the petroleum prospects of the Kesrouane Formation in Lebanon. The hydrothermal fault-related dolostones possess porosities of up to 20%, which result from intercrystalline and mouldic porosity enhancement. Porosities in the stratabound reflux dolostones (Early Jurassic) and limestones are much lower. The fact that most of the Jurassic system in onshore Lebanon was affected by meteoric diagenesis during the Late Jurassic - Early Cretaceous and the Cenozoic may downgrade hydrocarbon prospectivity. However, offshore areas far from the meteoric realm may have been less (or not at all) affected by meteoric invasion. If effective seals are present there, these areas may host promising Jurassic reservoir units. We also review the prospectivity of unexposed Triassic potential reservoir units in onshore Lebanon (e. g. the "Qartaba" structure). By analogy with the Syrian portion of the Palmyride Basin, Triassic strata here may include both reservoir units and evaporite seals. [source] A REVIEW OF EOCENE NUMMULITE ACCUMULATIONS: STRUCTURE, FORMATION AND RESERVOIR POTENTIALJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2001A. Racey Eocene nummulite accumulations, also referred to as nummullte "banks", form Important hydrocarbon reservoirs in Tunisia and Libya and may constitute exploration targets in other parts of North Africa, the Mediterranean and the Middle East. Porosities commonly average 10,20% and permeabilities 10,50md. Foraminifera of the genus Nummulites may comprise up to 98% of the bioclasts in these carbonate reservoirs, although only one or two species may be present. The absence of associated fauna is generally taken to indicate an oligotrophic depositional environment. In this paper, the palaeoecology of the genus Nummulites is discussed together with depositional models for two nummulitic carbonate reservoirs , the Middle Eocene Seeb Limestone of Oman and the Early Eocene El Garia/Jdeir Formation of Tunisia and Libya. The El Garia and Seeb Limestone Formations were deposited in ramp settings, and comprise a series of amalgamated sheets or low-relief banks. In the Hasdrubal field offshore Tunisia, where the El Garia Formation constitutes the reservoir rock, most of the nummulites have been redeposited from shallow into deeper waters whilst in the Bourri field (offshore Libya) they occur as an in situ "bank". Nummulite accumulations often show evidence that both physical reworking (scouring, winnowing and imbrication) and biological processes (reproduction strategies and bioturbation) have influenced their formation. A general model is outlined for discriminating between physically and ecologically produced biofabrics, and the implications for reservoir quality are discussed. [source] Calcium Phosphate Bioceramics with Various Porosities and Dissolution RatesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2002Soon-Ho Kwon 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. [source] The causes of porotic hyperostosis and cribra orbitalia: A reappraisal of the iron-deficiency-anemia hypothesisAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009Phillip L. Walker Abstract Porosities in the outer table of the cranial vault (porotic hyperostosis) and orbital roof (cribra orbitalia) are among the most frequent pathological lesions seen in ancient human skeletal collections. Since the 1950s, chronic iron-deficiency anemia has been widely accepted as the probable cause of both conditions. Based on this proposed etiology, bioarchaeologists use the prevalence of these conditions to infer living conditions conducive to dietary iron deficiency, iron malabsorption, and iron loss from both diarrheal disease and intestinal parasites in earlier human populations. This iron-deficiency-anemia hypothesis is inconsistent with recent hematological research that shows iron deficiency per se cannot sustain the massive red blood cell production that causes the marrow expansion responsible for these lesions. Several lines of evidence suggest that the accelerated loss and compensatory over-production of red blood cells seen in hemolytic and megaloblastic anemias is the most likely proximate cause of porotic hyperostosis. Although cranial vault and orbital roof porosities are sometimes conflated under the term porotic hyperostosis, paleopathological and clinical evidence suggests they often have different etiologies. Reconsidering the etiology of these skeletal conditions has important implications for current interpretations of malnutrition and infectious disease in earlier human populations. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] The Influence of Electrode Porosity on Diffusional Cyclic VoltammetryELECTROANALYSIS, Issue 22 2008Denis Menshykau Abstract A simple generic model to predict the influence of electrode porosity on the cyclic voltammetric response of an electrode is presented. The conditions under which deviation from the behavior of a perfectly flat, planar electrode can be expected are predicted. The scope for misinterpretation when conventional flat electrode theory is applied to porous electrodes is highlighted, especially in respect to the extraction of electrode kinetic parameters and the influence of ,electrocatalysis'. [source] Enhancing the Porosity of Mesoporous Carbon-Templated ZSM-5 by DesilicationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2008Martin S. Holm Abstract A tunable desilication protocol applied on a mesoporous ZSM-5 zeolite synthesized by carbon-templating is reported. The strategy enables a systematic manufacture of zeolite catalysts with moderate to very high mesoporosities. Coupling carbon-templating and desilication thus allow for more than a doubling of the original mesopore volume and mesopore surface area. The porosity effect arising from various treatment times and base amounts in the media has beenthoroughly mapped. Initially, small mesopores are created, and as desilication strength increases the average mesopore size enhances. Crystallinity of the treated samples is retained, and electron microscopy indicates solely intracrystalline mesoporosity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Silica-Based, Organically Modified Host Material for Waveguide Structuring by Two-Photon-Induced PhotopolymerizationADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Stefan Krivec Abstract The three-dimensional fabrication of optical waveguides has gained increasing interest in recent years to establish interconnections between electrical components on a very small scale where copper circuits encounter severe limitations. In this work the application of optically clear, organically modified porous silica monoliths and thin films as a host material for polymeric waveguides to be inscribed into the solid host structure by two-photon-induced photopolymerization is investigated. Porosity is generated using a lyotropic liquid crystalline surfactant/solvent system as a template for the solid silica material obtained by a sol,gel transition of a liquid precursor. In order to reduce the brittleness of the purely inorganic material, organic,inorganic co-precursor molecules that contain poly(ethylene glycol) chains are synthesized and added to the mixture, which successfully suppresses macroscopic cracking and leads to flexible thin films. The structure of the thus-obtained porous organic,inorganic hybrid material is investigated by atomic force microscopy. It is shown that the modified material is suitable for infiltration with photocurable monomers and functional polymeric waveguides can be inscribed by selective two-photon-induced photopolymerization. [source] SiOC Ceramic Monoliths with Hierarchical PorosityINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2010Cekdar Vakifahmetoglu SiOC glass monoliths possessing hierarchical porosity were produced by a one-pot processing method. Periodic mesoporous organosilica (PMO) particles were embedded into a foamed siloxane preceramic polymer. After pyrolysis at 1000°C in inert atmosphere, open celled, permeable SiOC ceramic monoliths with a high amount of pores, ranging in size from hundred of micrometers to a few nanometers, were obtained. The components possessed a specific surface area of 137 m2/g, indicating the retention of most of the mesopores after the pyrolytic conversion of the PMO precursor particles. These fillers converted to truncated rhombic dodecahedral SiOC mesoporous micron-sized grains, homogeneously distributed throughout the SiOC cellular matrix. The produced porous ceramics possessed compression strength of about 1.7 MPa, which is adequate for their use in several engineering applications. [source] Bioceramic Bone Graft Substitutes: Influence of Porosity and ChemistryINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2005Karin A. Hing Bioceramics have been considered for use as synthetic bone graft substitutes (BGSs) for over 30 years, throughout which there have been two primary areas of research: (i) optimization of the physical pore structure and (ii) formulation of an appropriate bioceramic chemistry. While it is well recognized that both the rate of integration and the final volume of regenerated bone are primarily dependent on the macroporosity, there still seems to be some dispute regarding the optimum "type" of porosity. The rate and quality of bone integration have, in turn, been related to a dependence on pore size, porosity volume fraction, and interconnection size and interconnection density, both as a function of structural permeability and mechano-transduction. Moreover, the role of strut microstructure and pore geometry have been considered with respect to their influence on entrapment and recruitment of growth factors (GFs) in addition to its influence on scaffold mechanics. Deconvoluting the relative affects of these parameters is complicated by the use of both resorbable and nonresorbable bioactive bioceramics, which are believed to mediate bioactivity in the osseous environment through two principal mechanisms: (i) directly through dissolution and release of ionic products in vivo, elevating local concentrations of soluble species that interact directly with local cells or influence cell behavior by their effect on local pH, (ii) indirectly through the influence that surface chemistry will have on protein adsorption, GF entrapment, and subsequent cell attachment and function. This article aims to review some of the recent developments in bioceramic BGSs, with a view to understanding how the various physiochemical parameters may be optimized to promote bone healing. [source] Porosity of human mandibular condylar boneJOURNAL OF ANATOMY, Issue 3 2007G. A. P. Renders Abstract Quantification of porosity and degree of mineralization of bone facilitates a better understanding of the possible effects of adaptive bone remodelling and the possible consequences for its mechanical properties. The present study set out first to give a three-dimensional description of the cortical canalicular network in the human mandibular condyle, in order to obtain more information about the principal directions of stresses and strains during loading. Our second aim was to determine whether the amount of remodelling was larger in the trabecular bone than in cortical bone of the condyle and to establish whether the variation in the amount of remodelling was related to the surface area of the cortical canals and trabeculae. We hypothesized that there were differences in porosity and orientation of cortical canals between various cortical regions. In addition, as greater cortical and trabecular porosities are likely to coincide with a greater surface area of cortical canals and trabeculae available for osteoblastic and osteoclastic activity, we hypothesized that this surface area would be inversely proportional to the degree of mineralization of cortical and trabecular bone, respectively. Micro-computed tomography was used to quantify porosity and mineralization in cortical and trabecular bone of ten human mandibular condyles. The cortical canals in the subchondral cortex of the condyle were orientated in the mediolateral direction, and in the anterior and posterior cortex in the superoinferior direction. Cortical porosity (average 3.5%) did not differ significantly between the cortical regions. It correlated significantly with the diameter and number of cortical canals, but not with cortical degree of mineralization. In trabecular bone (average porosity 79.3%) there was a significant negative correlation between surface area of the trabeculae and degree of mineralization; such a correlation was not found between the surface area of the cortical canals and the degree of mineralization of cortical bone. No relationship between trabecular and cortical porosity, nor between trabecular degree of mineralization and cortical degree of mineralization was found, suggesting that adaptive remodelling is independent and different between trabecular and cortical bone. We conclude (1) that the principal directions of stresses and strains are presumably directed mediolaterally in the subchondral cortex and superoinferiorly in the anterior and posterior cortex, (2) that the amount of remodelling is larger in the trabecular than in the cortical bone of the mandibular condyle; in trabecular bone variation in the amount of remodelling is related to the available surface area of the trabeculae. [source] Black bear femoral geometry and cortical porosity are not adversely affected by ageing despite annual periods of disuse (hibernation)JOURNAL OF ANATOMY, Issue 2 2007Meghan E. McGee Abstract Disuse (i.e. inactivity) causes bone loss, and a recovery period that is 2,3 times longer than the inactive period is usually required to recover lost bone. However, black bears experience annual disuse (hibernation) and remobilization periods that are approximately equal in length, yet bears maintain or increase cortical bone material properties and whole bone mechanical properties with age. In this study, we investigated the architectural properties of bear femurs to determine whether cortical structure is preserved with age in bears. We showed that cross-sectional geometric properties increase with age, but porosity and resorption cavity density do not change with age in skeletally immature male and female bears. These findings suggest that structural properties substantially contribute to increasing whole bone strength with age in bears, particularly during skeletal maturation. Porosity was not different between skeletally immature and mature bears, and showed minimal regional variations between anatomical quadrants and radial positions that were similar in pattern and magnitude between skeletally immature and mature bears. We also found gender dimorphisms in bear cortical bone properties: females have smaller, less porous bones than males. Our results provide further support for the idea that black bears possess a biological mechanism to prevent disuse osteoporosis. [source] Development of a 95/5 poly(L -lactide- co -glycolide)/hydroxylapatite and ,-tricalcium phosphate scaffold as bone replacement material via selective laser sinteringJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008Rebecca Louise Simpson Abstract 95/5 Poly(L -lactide- co -glycolide) was investigated for the role of a porous scaffold, using the selective laser sintering (SLS) fabrication process, with powder sizes of 50,125 and 125,250 ,m. SLS parameters of laser power, laser scan speed, and part bed temperature were altered and the degree of sintering was assessed by scanning electron microscope. Composites of the 125,250 ,-tricalcium phosphate (CAMCERAM® II) were sintered, and SLS settings using 40 wt % CAMCERAM® II were optimized for further tests. Polymer thermal degradation during processing led to a reduction in number and weight averaged molecular weight of 9% and 12%, respectively. Compression tests using the optimized composite sintering parameters gave a Young's modulus, yield strength, and strain at 1% strain offset of 0.13 ± 0.03 GPa, 12.06 ± 2.53 MPa, and 11.39 ± 2.60%, respectively. Porosity was found to be 46.5 ± 1.39%. CT data was used to create an SLS model of a human fourth middle phalanx and a block with designed porosity was fabricated to illustrate the process capabilities. The results have shown that this composite and fabrication method has potential in the fabrication of porous scaffolds for bone tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Porous Ti-6Al-4V alloy fabricated by spark plasma sintering for biomimetic surface modificationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2004Masayuki Kon Abstract Porous compacts with both biological and biomechanical compatibilities and high strength were developed. Spherical powders of Ti-6Al-4V alloy, which were either as received or surface modified with the use of calcium ions by hydrothermal treatment (HTT), were fabricated by a spark plasma sintering process. The porous compacts of pure Ti were used as reference materials. Porosity was approximately 30%, and compressive strengths were 113 and 125 MPa for the as-received Ti alloy powders and those modified by the HTT process, respectively. The bending strength and elastic modulus of as-received Ti alloy powders were 128,178 MPa and 16,18 GPa, respectively. Each of the compacts was immersed in simulated body fluid (SBF). The amount of adsorption/precipitation of calcium phosphate through the compacts was measured by weight change and was observed by SEM. The compacts were covered with calcium phosphate after 2 weeks of immersion in SBF. The compacts of Ti alloy had plenty of precipitated apatite crystals, and modification by HTT accumulated more precipitation. Because calcium phosphate is a mineral component of bone, apatite, which is precipitated on the surface of the compacts, could adsorb proteins and/or drugs such as antibiotics. It is expected that a large amount of proteins and/or drugs could be impregnated when the porous compacts developed are used. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 88,93, 2004 [source] An In Vitro Study of the Ultrasonic Axial Transmission Technique at the Radius: 1-MHz Velocity Measurements Are Sensitive to Both Mineralization and Intracortical Porosity,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2004Emmanuel Bossy Abstract The ultrasonic axial transmission technique allows for investigating skeletal sites such as the cortical layer of long bones (radius, tibia, phalanges). Using synchrotron radiation ,CT, we investigated, in vitro, the relationships between 1-MHz axial transmission SOS measurements at the radius and site-matched measurements of C.Th, POR, MIN, and vBMD. Introduction: The ultrasonic axial transmission technique allows for investigating skeletal sites such as the cortical layer of long bones (radius, tibia, phalanges). Materials and Methods:Using synchrotron radiation ,CT, we investigated, in vitro, the relationships between 1-MHz axial transmission speed of sound (SOS) measurements at the radius and site-matched measurements of cortical thickness (C.Th), intracortical porosity (POR), tissue mineralization (MIN), and volumetric BMD (vBMD). SOS measurements were based on bidirectional axial transmission and were performed with a 1-MHz proprietary probe on 39 excised human radii. Results: The highest correlations between SOS values and bone parameters (R2SOS/POR = 0.28, p < 10,3; R2SOS/MIN = 0.38, p < 10,4; R2SOS/vBMD = 0.57, p < 10,3) were found for bone parameters assessed in a 1-mm-thick periosteal region of the cortex rather than throughout the whole cortex. The observed moderate correlation between SOS and C.Th values (R2SOS/C.Th = 0.20, p < 10,2) disappeared when controlled for other variables. The two best multilinear predictive models, including either BMD alone or the pair of dependent variables MIN and POR (all assessed in the periosteal cortex), were equally accurate in predicting SOS values (R2SOS/(POR,MIN) = 0.59, p < 10,5; R2SOS/vBMD = 0.57, p < 10,5). Conclusion: For the first time, the respective adjusted contributions of POR (,24 m/s%,1) and tissue mineralization (+3.5 m/s/mg/cm,3) to SOS values were assessed. These results suggest potential sensitivity of axial transmission SOS values to changes in cortical bone status under different pathological conditions or treatments affecting POR and/or tissue mineralization. [source] Fractal Dimension of Trabecular Bone Projection Texture Is Related to Three-Dimensional MicroarchitectureJOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2000L. Pothuaud Abstract The purpose of this work was to understand how fractal dimension of two-dimensional (2D) trabecular bone projection images could be related to three-dimensional (3D) trabecular bone properties such as porosity or connectivity. Two alteration processes were applied to trabecular bone images obtained by magnetic resonance imaging: a trabeculae dilation process and a trabeculae removal process. The trabeculae dilation process was applied from the 3D skeleton graph to the 3D initial structure with constant connectivity. The trabeculae removal process was applied from the initial structure to an altered structure having 99% of porosity, in which both porosity and connectivity were modified during this second process. Gray-level projection images of each of the altered structures were simply obtained by summation of voxels, and fractal dimension (Df) was calculated. Porosity (,) and connectivity per unit volume (Cv) were calculated from the 3D structure. Significant relationships were found between Df, ,, and Cv. Df values increased when porosity increased (dilation and removal processes) and when connectivity decreased (only removal process). These variations were in accordance with all previous clinical studies, suggesting that fractal evaluation of trabecular bone projection has real meaning in terms of porosity and connectivity of the 3D architecture. Furthermore, there was a statistically significant linear dependence between Df and Cv when , remained constant. Porosity is directly related to bone mineral density and fractal dimension can be easily evaluated in clinical routine. These two parameters could be associated to evaluate the connectivity of the structure. [source] Development of the powder reaction moulding processJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2009Lei Zhao Abstract BACKGROUND: The powder reaction moulding process uses a reactive monomer as carrier and binder for the moulding of metal or ceramic powders. De-binding is achieved using thermal depolymerisation which is followed by sintering to give the finished component. Binder can be recovered for re-use. RESULTS: Moulding compounds, with various powder volume fractions, have been prepared using stainless steel, silicon nitride and alumina with n-butyl cyanoacrylate as binder, and the stability of the compounds established. Rheological properties of the compounds have been measured using both pressure flow and drag flow methods. Compounds are strongly pseudoplastic. Comparison of experimental results with theoretical models, describing suspension flow behaviour shows that experimental maximum volume fractions are close to the theoretical volume fraction of 0.42 for silicon nitride, 0.68 for alumina and 0.7 for stainless steel. Differential scanning calorimetry and thermogravimetry have been used to simulate de-binding and show a rapid loss of binder through depolymerisation. Post-sintering porosity of the ceramic materials is high but this is thought to arise from the low pressure moulding techniques used. Porosity of the stainless steel mouldings is much lower. CONCLUSIONS: The results validate the powder reaction moulding idea and demonstrate applicability to three widely different powder materials. Copyright © 2008 Society of Chemical Industry [source] Porosity and surface characteristics of activated carbons produced from waste tyre rubberJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2002Guillermo San Miguel Abstract Waste tyre rubber has proven to be a suitable precursor for the production of high quality activated carbons. The performance of these carbons in commercial applications such as water treatment or gas purification is highly dependent on their surface characteristics. This paper presents an in-depth investigation on how production conditions may affect the yield and characteristics of activated carbons produced from tyre rubber. For this purpose, three tyre rubbers of different particle sizes were consecutively pyrolysed and then activated in a steam atmosphere at 925,°C using a laboratory-scale rotary furnace. Activation was conducted at different intervals over 80,640,min to achieve different degrees of carbon burn-off. The resulting carbons were analysed for their elemental composition, ash content and nitrogen gas adsorption characteristics. The BET and t -plot models were used to investigate various aspects of their porosity and surface area characteristics. SEM analyses were also conducted for visual examination of the carbon surface. Results show that pyrolytic chars, essentially mesoporous materials, developed a very narrow microporosity during the initial stages of the activation process (up to 15,25,wt% burn-off). Further activation resulted in the progressive enlargement of the average micropore width and a gradual development of the mesoporous structure. Total micropore volumes and BET surface areas increased continuously with the degree of activation to reach values up to 0.498,cm3g,1 and 1070,m2g,1 respectively, while external surface areas developed more rapidly at degrees of activation above 45,wt% burn-off. Results presented in this work also illustrate that carbons produced from powdered rubber developed a narrower and more extensive porosity, both in the micropore and mesopore range, than those produced from rubber of a larger particle size. © 2001 Society of Chemical Industry [source] A FUZZY LOGIC APPROACH TO ESTIMATING HYDRAULIC FLOW UNITS FROM WELL LOG DATA: A CASE STUDY FROM THE AHWAZ OILFIELD, SOUTH IRANJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2009A. Kadkhodaie-Ilkhchi Porosity-permeability relationships in the framework of hydraulic flow units can be used to characterize heterogeneous reservoir rocks. Porosity is a volumetric parameter whereas permeability is a measure of a rock's flow properties and depends on pore distribution and connectivity. Thus zonation of a reservoir using flow zone indicators and the identification of flow units can be used to evaluate reservoir quality based on porosity-permeability relationships. In the present study, we attempt to make a quantitative correlation between flow units and well log responses using fuzzy logic in the mixed carbonate-clastic Asmari Formation at the Ahwaz oilfield, South Iran. A hybrid neuro-fuzzy approach was used to verify the results of fuzzy modelling. For this purpose, well log and core data from three wells at Ahwaz were used to make an intelligent formulation between core-derived flow units and well log responses. Data from a separate well was used for evaluation and validation of the results. The results of this study demonstrate that there is a good agreement between core-derived and fuzzy-logic derived flow units. Fuzzy logic was successful in modelling flow units from well logs at well locations for which no core data was available. [source] THE RESERVOIR POTENTIAL OF MIOCENE CARBONATE ROCKS IN THE ASKALE AND HINIS-MUS-VAN SUB-BASINS, EAST ANATOLIA, TURKEYJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2003A. G. Büyükutku Lower-middle Miocene limestones in East Anatolia (eastern Turkey) assigned to the Adilcevaz Formation were studied using core and cuttings data from eight wells in the Tertiary Askale and Hinis-Mus-Van sub-basins. Their depositional environment, diagenetic characteristics and reservoir quality are reviewed. The Adilcevaz Formation carbonates are up to 225m thick. Abundant bioclasts are dominated by corals, encrusting red algae, bryozoans, and benthonic and planktonic foraminifera. Reef-core, fore-reef and back-reef facies were recognized. The preservation of primary porosity is generally poor as a result of late calcite cementation. Porosity is mainly present as moulds, vugs and interparticle types, which are best developed in the fore-reef and reef-core facies. However these pores are poorly connected and permeability is generally less than 0.1 mD. In contrast to coeval limestones of similiar facies in Iran, Iraq and other parts of the Middle East, the Adilcevaz Formation has little reservoir potential. [source] DEPOSITIONAL ENVIRONMENT AND DIAGENESIS OF THE EOCENE JDEIR FORMATION, GABES-TRIPOLI BASIN, WESTERN OFFSHORE, LIBYAJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2000J. M. Anketell The late Ypresian (early Eocene) Jdeir Formation was deposited in the Mesozoic-Cenozoic Gabes-Tripoli Basin, offshore Libya. The basin developed on the northern passive margin of the African Plate and was relatively unstable being affected by syn-sedimentary tectonic movements. Deposition was coeval with a relative rise of sea-level and the subsequent highstand. A lower, thinly-developed nummulitic bank facies with restricted distribution records the transgressive event and is succeeded by more micritic sediments that record the time of maximum flooding. The succeeding sea-level highstand is represented by a thick, and widely developed, progradational-aggradational nummulitic sequence that displays lateral changes across WE-ESE trending facies belts. Three major lithofacies are recognized in the Jdeir Formation: Nummulites packstone-grainstone, Alveolina-Orbitoliteswackestone-packtone, andFragmental-Discocyclina-Assilina wackestone-packstone, depositedin bank, back-bank, and fore-bank environments, respectively. The formation passes to the NNE into the pelagic lithofacies of the Hallab Formation; landward, to the south, it passes into shoreline evaporitic facies of the Taljah Formation. The lithofacies were structurally controlled by contemporaneous and/or syndepositional tectonic movements, with nummulitic facies tending to develop on uplifted areas. Petrographic and petrophysical studies indicate that porosity in the Jdeir Formation is controlled by depositional environment, tectonic setting and diagenesis. The combined effects of salt tectonics, a major unconformity at the top of the formation and meteoric diagenesis have produced excellent-quality reservoir facies at the Bouri oilfield and in other areas. Porosity is highest in the nummulitic bank facies and lowest in the Alveolina-Orbitolites micrite facies. Good to excellent reservoir quality occurs in the upper part of the nummulitic packstone-grainstone facies, especially where these sediments overlie structurally high areas. High rates of dissolution found at the crests of domes and anticlines suggest that early diagenetic processes and features are, in part, structurally controlled. Future exploration success will depend on investigation of similar structures within the Gabes-Tripoli Basin. Both porosity initiation and preservation are related to early depositional and diagenetic processes. The wide time-gap between hydrocarbon generation and reservoir formation points to the role of the seal in porosity preservation and rules out the assumption that early emplacement of oil had preserved the porosity. [source] DOLOMITIZATION OF THE EARLY EOCENE JIRANI DOLOMITE FORMATION, GABES-TRIPOLI BASIN, WESTERN OFFSHORE, LIBYAJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2000I. Y. Mriheel Dolomitization in the early Eocene Jirani Formation in the Gabes-Tripoli Basin (offshore western Libya) occurred in two stages. Stage I dolomites are composed of two types, one associated with anhydrite (Type I) the other anhydrite free (Type II,). The stratigraphic and sedimentological settings together with petrographic and geochemical criteria suggest that dolomitization was effected by refluxed evaporative seawater. Stable isotope and trace element analyses suggest dolomitization of both Types from a fluid of near-surface seawater composition under oxidising conditions modified by evaporation. Non-luminescence and lack ofzonation of all the dolomite indicate that the dolomitizing fluids maintained a relatively constant composition. The geologic setting during the early Eocene, interpreted as hypersaline lagoon, supports an evaporative reflux origin for the anhydritic dolomite Type I. Type II developed under less saline conditions in the transition zone between lagoon and open marine shelf. Stage II dolomitization is recorded by negative isotope values in both Types I and II indicating their dissolution and recrystallization (neomorphism) by dilute solutions. A period of exposure of the overlying Jdeir Formation following a relative sea-level fall allowed ingress of meteoric waters into both the Jdeir and the underlying Jirani Formations. Flushing by meteoric waters also resulted in development of excellent secondaly porosity and caused major dissolution of anhydrite to form the anhydritic-free dolomite facies typical of Type II. Following, and possibly during, both Stages I and II, low temperature dolomites (Type IIIa) precipitated in pore spaces from residual jluids at shallow burial depths, partially occluding porosity. In the late stage of basin evolution, medium clystalline, pore-filling saddle dolomite precipitated, causing some filling of mouldic and vuggy porosity (Type IIIb). Very light oxygen isotopic signatures confirm that it developed from high temperature fluids during deep burial diagenesis. Calculation of temperatures and timings of the dolomitization and cement phases show that the main dolomitization phases and Type IIIa cements occurred in the early Eocene, and that the saddle dolomite precipitated in the Miocene; these results are consistent with age relationships established from stratigraphic, petrographic and geochemical signatures. The most common porosity includes intercrystal, vuggy and mouldic types. Porosity is both pre-dolomitization and syn-dolomitization in origin, but the latter is the most dominant. Hence, reservoir quality is largely controlled by fluid dynamics. [source] The Effect of Coating Patterns with Spinel-Based Investment on the Castability and Porosity of Titanium Cast into Three Phosphate-Bonded InvestmentsJOURNAL OF PROSTHODONTICS, Issue 7 2010Anelise R. F. Pieralini DDS Abstract Purpose: This study evaluated the effect of pattern coating with spinel-based investment Rematitan Ultra (RU) on the castability and internal porosity of commercially pure (CP) titanium invested into phosphate-bonded investments. The apparent porosity of the investment was also measured. Materials and Methods: Square patterns (15 × 15 × 0.3 mm3) were either coated with RU, or not and invested into the phosphate-bonded investments: Rematitan Plus (RP), Rema Exakt (RE), Castorit Super C (CA), and RU (control group). The castings were made in an Ar-arc vacuum-pressure machine. The castability area (mm2) was measured by an image-analysis system (n = 10). For internal porosity, the casting (12 × 12 × 2 mm3) was studied by the X-ray method, and the projected porous area percentage was measured by an image-analysis system (n = 10). The apparent porosity of the investment (n = 10) was measured in accordance with the ASTM C373-88 standard. Results: Analysis of variance (One-way ANOVA) of castability was significant, and the Tukey test indicated that RU had the highest mean but the investing technique with coating increased the castability for all phosphate-bonded investments. The analysis of the internal porosity of the cast by the nonparametric test demonstrated that the RP, RE, and CA with coating and RP without coating did not differ from the control group (RU), while the CA and RE casts without coating were more porous. The one-way ANOVA of apparent porosity of the investment was significant, and the Tukey test showed that the means of RU (36.10%) and CA (37.22%) were higher than those of RP (25.91%) and RE (26.02%). Conclusion: Pattern coating with spinel-based material prior to phosphate-bonded investments can influence the castability and the internal porosity of CP Ti. [source] Dye-Sensitized Solar Cells Based on TiO2 Coatings with Dual Size-Scale PorosityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2009Lai Qi Dye-sensitized solar cells (DSSC) with efficiencies greater than 4% were produced with templated "inverse opal" titania coatings. A novel one-step method produces uniform and crack-free coatings made using commercially available titania nanoparticles with high reproducibility and uniformity. In this research, a volatile solvent electrolyte was tested; however, it shows proof-of-concept that larger pore volumes can be created for increased penetration of more viscous electrolytes that can be utilized in high-efficiency cells. This dual size-scale porosity film is a promising structure for DSSC applications, especially for those solid-state or quasi-solid-state cells that require polymer electrolytes. [source] Particle Rearrangement and Pore Space Coarsening During Solid-State SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2009Hans Eckart Exner Coarsening of porosity during sintering has been observed in powder compacts of metallic, ceramic, and amorphous materials. Monitoring and modelling of the growth of individual (closed) pores in the late sintering stages are well established. Porosity is interconnected up to very high densities. Coarsening of the continuous pore space takes place during the initial and intermediate sintering stages. This coarsening is caused by localized transport of atoms or molecules (diffusion or viscous flow) as well as by bulk particle movement (rearrangement). Its quantitative exploration poses problems both experimentally and theoretically. Ways to characterize the geometry of the interconnected pore space and of closed pores are discussed with emphasis on stereological parameters. Recent and classical approaches, experimental findings with 2D model arrangements (as the formation and opening up of particle contacts, pore coarsening, and particle rearrangement) and some advances of computer simulations are discussed together with open questions. [source] Tomography-Based Multiscale Analyses of the 3D Geometrical Morphology of Reticulated Porous CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Jörg Petrasch X-ray microtomography with a digital resolution of 30 ,m and synchrotron submicrometer tomography with a digital resolution of 350/700 nm are performed on catalyst-coated reticulate porous ceramic foa, 22[2] 121,45ms. Porosity, specific surface, pore-size distribution, two-point correlation function, and minimum size of a representative elementary volume are computed by image processing of the tomographic reconstructions on the mm-scale- and ,m-scale-sized pores. Numerically determined porosities are experimentally validated by weighing, helium pycnometry, and mercury intrusion porosimetry. [source] Effect of Porosity on the Electrical Properties of Polycrystalline Sodium Niobate: I, Electrical ConductivityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2003Silvania Lanfredi The electrical behavior of NaNbO3 ceramic samples with different relative densities was investigated by ac impedance spectroscopy in a range of 13 MHz to 10,3 Hz between 400° and 800°C in dry air. Measurements were performed during heating and cooling cycles. The Nyquist impedance diagrams of dense sodium niobate exhibit only one semicircle representing the grain contribution with depression angles as small as 1°, indicating a high homogeneity of the specific electrical properties. In the case of porous samples, the data reveal an additional low-frequency semicircle related to microstructure. For all studied samples, the Arrhenius conductivity plots show a change in the activation energy around 640°C, attributed to the tetragonal-cubic phase transition. The electrical conductivity of porous samples appears to be higher than that of dense ones. [source] Microstructure and Mechanical Properties of Silicon Nitride Ceramics with Controlled PorosityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002Jian-Feng Yang Porous silicon nitride ceramic with a porosity from 0,0.3 was fabricated by partial hot-pressing of a powder mixture of ,-Si3N4 and 5 wt% Yb2O3 as sintering additive. Irrespective of the porosity, the samples exhibited almost the same microstructural features including grain size, grain aspect ratio, and pore size. Porosity dependences of Young's modulus, flexural strength, and fracture toughness (KIC) were investigated. All these properties decreased with increasing porosity. However, because of the fibrous microstructure, the decreases of flexural strength and fracture toughness were moderate compared with the much greater decrease of Young's modulus. Thus, the strain tolerance (fracture strength/Young's modulus) increased with increasing porosity. The critical energy release rate also increased slightly with an increasing volume fraction of porosity to 0.166 and remained at the same level with that of the dense sample when the porosity was 0.233. They decreased as porosity increased further. [source] Porous Biodegradable Scaffold: Predetermined Porosity by Dissolution of Poly(ester-anhydride) Fibers from Polyester MatrixMACROMOLECULAR BIOSCIENCE, Issue 7 2009Jaana Rich Abstract A novel selective leaching method for the porogenization of the biodegradable scaffolds was developed. Continuous, predetermined pore structure was prepared by dissolving fast eroding poly(, -caprolactone)-based poly(ester-anhydride) fibers from the photo-crosslinked poly(, -caprolactone) matrix. The porogen fibers dissolved in the phosphate buffer (pH 7.4, 37,°C) within a week, resulting in the porosity that replicated exactly the single fiber dimensions and the overall arrangement of the fibers. The amount of the porosity, estimated with micro-CT, corresponded with the initial amount of the fibers. The potential to include bioactive agents in the porogen fibers was demonstrated with the bioactive glass. [source] Electrospun Composite Mats of Poly[(D,L -lactide) -co- glycolide] and Collagen with High Porosity as Potential Scaffolds for Skin Tissue EngineeringMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2009Ye Yang Abstract Electrospun composite mats of poly[(D,L -lactide) -co- glycolide] and collagen with high porosities of 85,90% and extended pore sizes of 90,130,µm were prepared to mimic the ECM morphologically and chemically. The existence of collagen molecules on the fiber surface was confirmed, enabling the cells to find enhanced binding sites for their integrin receptors. The mechanical data for the blended fibrous mats indicated that they were sufficiently durable for dermal tissue engineering. Fibroblasts derived from GFP transgenic C57BL/6 mice were used to directly observe cell proliferation, and the inoculation of collagen enhanced cell attachment, proliferation and extracellular matrix secretion, which were found to be dependent on the amount of collagen in the composite scaffold. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||