Excessive Porosity Research Articles

Ultrasonic technique for measuring porosity of plasma-sprayed alumina coatings

Porosity is an important factor in plasma-sprayed coatings, especially ceramic coatings. Excessive poros-ity can adversely affect the performance of the coated component in various ways. An ultrasonic nonde-structive measurement technique has been developed to measure porosity in plasma-sprayed alumina coatings. The technique is generic and can be extended to other ceramic coating systems. To test the tech-nique, freestanding alumina coatings with varying levels of porosity were fabricated via plasma spray. Samples with varying porosity, obtained through innovative fabrication techniques, were used to gener-ate a calibration curve. The ultrasonic velocity in the low-frequency range was found to be dependent on the density of freestanding coatings (measured via Archimedian techniques). This dependence is the basis of the development of a technique to measure the density of coatings.

Gas migration through water-saturated, fractured rock: results of a gas injection test

The generation of gases and possible development and migration of a gas phase at depth in groundwater-saturated, fractured rock has become an important aspect of assessing the performance and safety of radioactive waste disposal sites. To study gas-phase migration in this environment, helium gas was injected at constant pressure through an access borehole into an inclined fracture zone at a depth of about 40 m, in the granitic Lac du Bonnet Batholith, southeastern Manitoba, Canada. The gas flow rate, arrival time and pattern of distribution of gas at the surface were monitored by soil gas surveys. Gas flow rate increased from 5 to 20 l min −1 over the 11-day period of the test indicating removal of water from the flow paths. Breakthrough of injected gas at the surface was detected within 2 days. Two areas of high concentrations of gas discharge were observed within 40 m of the injection borehole, indicating gas transport through near-vertical fractures. A larger area of trace He concentrations was detected 200 m away indicating transport along the fracture zone. The field results were compared with predictions of a simple analytical model derived from Braester and Thunvik (1983). Good agreement was found when the influence of fracturing in the bedrock and a low-permeability overburden and `excess porosity' due to non-uniformity of fracture apertures were included in the model. The model was then used to estimate and map the relative hydraulic conductivities of individual gas flow paths in the fractured rock.

Complementary Analysis Using Polarized Light and Scanning Electron Microscopy in the Determination of Sulfate Attack on Concrete

Abstract A high water to cement ratio in concrete produces excessive porosity in the paste, thereby increasing the concrete’s susceptibility to sulfate attack and subsequent premature deterioration. Widely used as a building material, concrete experiences physical and chemical deterioration whose extent and nature may be determined by polarized light microscopy (PLM) and scanning electron microscopy (SEM). New software innovations allow exact image relocation in PLM and SEM, thereby producing complementary information which aids in analyst recognition and increases the effectiveness of each analytical technique. Although overlapping information may be derived using both PLM and SEM, each technique has inherent advantages and disadvantages which complement the other. The advantages of PLM include a color image, good low magnification resolution providing a bridge between macro/micro analysis, and the ability to distinguish polymorphs and materials of nearly identical composition (e.g., solid-solution series components). Disadvantages of PLM include limited high magnification potential, mineralogical identification based on the analyst’s knowledge of optics, and the need for photographic attachments.

Composition and ceramic properties of tertiary clays from southern Sardinia (Italy)

The Sardinian ceramic industry produces structural clay products (common and hollow bricks). The raw materials are obtained from Tertiary continental sediments (Cixerri, Ussana and Samassi Formations) found in the south-western part of the island. These clays have different mineralogical, chemical and grain size compositions and a different technological behaviour in the brick and tile production cycle. The Cixerri clays (Eo-Oligocene) are fine-grained and consist of illite, interstratilied I/S, quartz, kaolinite and high percentages of carbonates (19–24%). Overall, they are suitable for the production of high-quality common bricks, while they could also be part of mixes for roofing tiles and wall tiles. The Ussana clays (Oligo-Miocene) consist of illite-chlorite-kaolinite with high contents of quartz and variable percentages of carbonates (3–20%). In terms of grain size, they can be classified as silty clays and clayey silts. The behaviour in ceramic production is suitable for high-quality bricks, including roofing tiles. In addition, they could be the base for bodies to manufacture porous wall tiles. The Samassi clayey silts are rich in quartz and calcite, with a clay fraction consisting mostly of illite, smectite and chlorite. They are characterised by high dry shrinkage and excessive porosity of the fired samples, for which they are suitable only for mixes for common bricks.

The Deep Madden Field, a Super-Deep Madison Gas Reservoir, Wind River Basin, Wyoming: ABSTRACT

Madison dolomites form the reservoir of a super deep, potential giant sour gas field developed on the Madden Anticline immediately in front of the Owl Creek Thrust along the northern rim of the Wind River Basin, central Wyoming. The Madison reservoir dolomites are presently buried to some 25,000 feet at Madden Field and exhibit porosity in excess of 15%. An equivalent dolomitized Madison sequence is exposed in outcrop only 5 miles to the north on the hanging wall of the Owl Creek thrust at Lysite Mountain. Preliminary comparative stratigraphic, geochemical and petrologic data, between outcrop and available cores and logs at Deep Madden suggests: (1) early, sea level-controlled, evaporite-related dolomitization of the reservoir and outcrop prior to significant burial; (2) both outcrop and deep reservoir dolomites underwent significant recrystallization during a common burial history until their connection was severed during Laramide faulting in the Eocene; (3) While the dolomite reservoir at Madden suffered additional diagenesis during an additional 7-10 thousand feet of burial, the pore systems between outcrop and deep reservoir are remarkably similar. The two existing deep Madison wells at Madden are on stream, with a third deep Madison well currently drilling. The sequence stratigraphic framework and the diageneticmore » history of the Madison strongly suggests that outcrops and surface cores of the Madison in the Owl Creek Mountains will be useful in further development and detailed reservoir modeling of the Madden Deep Field.« less

Mo-W Interdiffusion and the Influence on Potassium Bubbles in W Lamp Wire

ABSTRACTThe effects of Mo contamination on the microstructure of lamp-grade tungsten wire are investigated in this study. Mo is often used as the mandrel material in the coiling of lamp filaments, and when utilized during high temperature heat treatments significant amounts of Mo can diffuse into the W. In this study, W-Mo diffusion couples were prepared and heat treated at temperatures of 2500°C and above to intentionally contaminate the W with Mo. After dissolution of the Mo and additional high temperature heat treatments of the W, equiaxed grains were observed in the W and excessive porosity was also observed. Explanations for these microstructural changes are discussed. Microprobe data were also obtained to quantify interdiffusion between the W and Mo.

Determination of fiber-matrix interphase moduli from experimental moduli of composites with multi-layered fibers

In this paper we report a method for inverse determination of effective elastic moduli of fiber-matrix interphases from experimentally measured composite moduli. Multi-phase micromechanical models and simplified spring approximations are used for inversion. An analytical expression for the transverse shear modulus of a composite with multi-layered fibers is derived using a multi-phase generalized self-consistent (MGSC) model, which forms the theoretical basis for inversion. This method has been used to determine the moduli of fiber-matrix interphases in ceramic and intermetallic matrix composites with similar SiC fibers and carbon fiber coating using the composite moduli measured ultrasonically. We find that the calculated moduli of interphasial carbon in the intermetallic matrix composite, after considering differences in microstructure, are very close to those available in the literature. The interphasial moduli obtained for the ceramic matrix composite are smaller than those published. We have found that this difference can be well explained by considering imperfect contact between the interphasial carbon and the matrix due to excessive matrix porosity at the interfacial region. Special emphasis is placed on error propagation in the inversion process and interpretation of experimental results. The results show that the interphasial moduli in intermetallic matrix composites are more sensitive to measurement error than those in ceramic matrix composites due to higher interphase-to-matrix stiffness ratio in intermetallic matrix composites. For both types of composites the calculated interphasial moduli are most sensitive to error in measurements of composite and matrix moduli and less sensitive to error in fiber moduli.

Composition/structure/property relations of multi-ion-beam reactive sputtered lead lanthanum titanate thin films: Part III. Electrical properties

This paper, the third and final of a three part series, presents the electrical properties of postdeposition annealed, lead lanthanum titanate (PLT) thin films deposited by multi-ion-beam reactive sputtering (MIBERS). Also, a model is presented that explains the relations among composition, crystallographic structure, microstructure, and electrical properties of the PLT thin films. Thin films of PLT consisting of the perovskite phase exhibit 〈100〉 textured microstructures. Addition of a critical quantity of excess PbO results in the loss of this 〈100〉 texture, and continuity of the perovskite phase is disrupted while both excess PbO and porosity phases become continuous due to a percolation effect. Films with textured microstructures consisting of a continuous perovskite phase exhibit relatively high dc resistivities, high dielectric permittivities, and high remanent polarizations. At the transition between textured and nontextured microstructures, a discontinuous drop in the electrical properties occurs due to the ensuing continuity of the excess PbO and porosity. These composition-induced changes in the electrical properties were quantitatively modeled by applying a simple mixing rule model to the microstructure model developed in Part II of this series.

Real-Time Pore-Pressure Evaluation From MWD/LWD Measurements and Drilling-Derived Formation Strength

Summary Traditional pore-pressure interpretations in tertiary undercompacted shales have been based on empirical relationships between a particular measurement (such as resistivity) and pore pressure in pounds per gallon. It is well-known, however, that the measurements are responding to the "excess" porosity in the shale rather than to the pore pressure directly. A new technique is illustrated in which all available measurements are first characterized in terms of this excess porosity and lithology with measurement-response equations. This allows a mathematical minimization technique to solve simultaneously the various measurement-response equations for this porosity and lithology on a foot-by-foot basis. A conventional compaction porosity/effective-stress model is then used to determine the additional pore pressure caused by this excess porosity. The result is a single pore-pressure estimate that is independent of the number of measurements and that has an accuracy that improves with the total number of measurements used in the interpretation. The interpretation can be performed at the wellsite in real time by use of rate of penetration (ROP), measurement while drilling (MWD), and logging while drilling (LWD) measurements or after drilling by use of these measurements in conjunction with wireline measurements.

The Georges Bank Basin: a quantitative basin analysis study

AbstractUsing a one‐dimensional (1D) fluid flow/compaction model applied to wells of the Georges Bank Basin, east coast, USA, has enabled a simulation to be made of the history of the sedimentation, basement subsidence, tectonic activity, geoheat flux evolution, maturation of organic matter, hydrocarbon generation, and migration tendency.Based on the analysis of the basement tectonic activity, the basin's development is related to the formation and the evolution of the east edge of the North American plate. Through the simulation of geoheat flux variation, maturation of organic material and hydrocarbon generation at different positions in the basin at different time periods are analysed. Additionally, from the modelling of excess fluid pressure, porosity and permeability variations in the strata, the potential hydrocarbon migration tendency and stratigraphic traps in the basin are discussed.

Geologic Characterization of Caddo Limestone Reservoir, Curry Unit, Stephens County, North-Central Texas: ABSTRACT

Three classic carbonate models (carbonate bank, oolitic shoal, and tidal flat) are applied to interpret the depositional environments and diagenesis of the Caddo limestone (Middle Pennsylvanian). The study area is located in west-central Stephens County, approximately 4 mi southwest of Breckenridge, Texas. Phylloid algal mounds developed on a lower Caddo ramp, along the transition of the Concho platform and Fort Worth basin. Within the area defined as the Curry unit, phylloid algal mounds and intermound facies aggraded to sea level. This led to the development of an areally restricted carbonate bank. Some phylloid algal buildups underwent subaerial exposure, and fresh water leached unstable carbonate minerals, creating minor secondary porosity (<10%). An oolitic shoal (0-9.2 m thick) overlies and partially intergrades with the phylloid algal bank. Ooids were deposited along the margin of the preexisting bank, whereas fine-grained oolitic and peloidal packstone were deposited on the bank. The bank margin oolite exhibits oomoldic porosity in excess of 15%. The uppermost 6.1-24.4 m of the Caddo represents intertidal deposition. Sediment, primarily algal remains and carbonate mud, was deposited on a preexisting surface of ooids and peloids. Fenestral fabric. rhizoliths, brecciated zones, and small-scale channels are common features. A wide variety of poremore » types are present in the intertidal zone; intraskeletal, framework, biomoldic, and vuggy pores are most important. Throughout this zone, porosity exceeds 10% and permeability averages 12 md. The Curry unit has produced approximately 28 million bbl of oil (primary and secondary) from the upper Caddo. Depositional environments and diagenesis of the Caddo are complex. A greater understanding of these complexities may enable geoscientists to evaluate remaining future potential within the Caddo and in other similar carbonate accumulations.« less

Etched glass ionomer liners: surface properties and interfacial profile with composite resins

The purpose of this study was to assess the surface alterations induced by acid etching on two glass ionomer lining cements (Ketac Bond, G-C lining cement) and to evaluate their interface with a composite resin (Herculite XR) following various surface treatments. The changes in the surface composition and topography of the etched liners were studied by electron microprobe and ESCA analyses. The interfacial treatments performed on the ionomer surfaces were: (i) application of a bonding resin; (ii) 20-s acid etching and application of a bonding resin; (iii) application of a dental adhesive based on a chlorophosphate ester of BisGMA (Scotch-bond LC), without acid etching. The interfacial sealing efficiency of these treatments was studied by the silver nitrate microleakage technique combined with optical and electron microscopy. According to the results the etched surfaces of both the liners present excessive porosity with glass and matrix dissolution. Significant changes in the surface chemistry of the liners were detected indicating severe degradation. The microleakage study revealed interfacial gaps and fractures in the etched samples. The best results were obtained from the non-etched ionomer liners which were subjected to the adhesive treatment. The efficiency of acid etching as a necessary step in the 'layered' technique is seriously questioned.

Diagenesis and Preservation of Porosity in Norphlet Formation (Upper Jurassic), Southern Alabama

Sandstones of the Norphlet Formation (Upper Jurassic) in the vicinity of Lower Mobile Bay, Alabama, have porosities greater than 20% and permeabilities up to about 1 darcy at depths of more than 20,000 ft (6,096 m). Typically, pre-Tertiary sandstones buried to such depths have approximately 6% (±2%) porosity; thus, deep Norphlet sandstones contain up to 14% excess porosity. This porosity is largely intergranular and appears to be preserved primary porosity. When the diagenetic scenario for the Norphlet is reconstructed in a time-temperature framework, it is apparent that porosity preservation is not the result of any single diagenetic event, but is due to a continuous series of diagenetic conditions that overlapped in time. The most important of these circumstances were the following. (1) The lack of pervasive early calcite or anhydrite cements found in the large eolian dunes (10-300 ft or 3-91 m high) that comprise the best Norphlet reservoirs. This lack of cement may have set the stage for subsequent events by keeping open pathways through which fluids were later able to efficiently contact the sandstone. (2) Early grain-coating clay/iron oxide rims reacted to form chlorite in the 176°-248°F (80°-120°C) thermal wind w. The grain-rimming chlorite may have inhibited subsequent quartz cementation. Up to 10.5% porosity may be due to the porosity preserving effect of chlorite. (3) Migration of hydrocarbons and development of geopressures, beginning at temperatures as low as 230°F (110°C), retarded further cementation. Up to 4.5% porosity may be due to the combined effects of hydrocarbons and geopressures. (4) A series of CO2-generating reactions occurred, including decarboxylation of organic acids, thermal cracking of liquid hydrocarbons, and thermochemical sulfate reduction. As a result of these reactions, late carbonate cements were not abundant. Thermochemical sulfate reduction (275°-356°+F or 135°-180°+C) has been of particular importance in the deep Norphlet. Reaction of hydrocarbons with anhydrite has resulted in the local removal of nodular anhydrite and has also affected gas quality (i.e., H2S content). The preserved porosity in Norphlet sandstones is the result of a combination of circumstances. The fact that these conditions overlapped in time-temperature space may be as important as any single factor.

Use of ion implantation techniques to characterize the oxidation of elemental nickel

Factors affecting the adherence of protective alumina scales have been profitably studied employing ion implantation techniques. Alumina is considered to grow largely (but not exclusively) by short-circuit diffusion of oxygen down grain boundaries. Hence studies were conducted involving the oxidation of nickel (pure and Ni-270) because outward cation nickel diffusion is known to be important in the growth of nickel oxide. In contrast with alumina scales, neither sulfur nor argon implants produced scale exfoliation. Moreover implanted carbon did not produce excessive porosity associated with the formation of CO. Yttrium implants had two effects. In pure nickel, implanted yttrium hindered oxidation-related diffusion. For both grades of nickel, the implanted yttrium was found after oxidation to be at the interface between two layers in the final oxide, functioning there as a marker indicating the initial surface of the metal. Nickel particles were present within mature scales on nickel of both grades characterized here. Mechanisms responsible for these effects and their implications are discussed.

The sintering characteristics and properties of hard metal with NiCr binders

The substitution of an NiCr binder for cobalt in conventional hard metals is known to enhance corrosion resistance in a variety of media. Chromium carbide is also noted for its grain growth inhibition properties in the production of abrasion resistant hard metals. However, in both cases, chromium has been associated with excessive porosity and reduced toughness in the sintered product. An attempt has been made to characterize the effect of chromium on the sintering process, using dilatometry and resistivity determinations. The system studied was based on WC-10wt.%Ni, with up to 50% substitution by chromium in the binder to give WC-5wt.%Ni-5wt.%Cr. Sintering activation energies were determined for each composition, the value increasing with increasing chromium content. While the straight nickel-bonded composition exhibited considerable shrinkage in the solid state (about 80% of total), increasing chromium levels delayed the onset of major shrinkage until the appearance of liquid phase. Isothermal treatments for extended times indicated that the liquid phase could appear at a temperature as low as 1210°C. It is proposed that dissolution of chromium in the nickel binder inhibits the tungsten carbide and nickel dissolution and that the formation of a low melting NiCrC eutectic results in most of the shrinkage in the high chromium compositions.

Pore Structure of Low Porosity DSP Cement Pastes

AbstractThe pore structure of low porosity cement pastes containing varying quantities of silica fume has been examined using mercury intrusion porosimetry (MIP) and nitrogen adsorption (NA) measurements. The water:solid ratio for all DSP pastes studied was 0.18. It was observed that, as for conventional pastes, removal of water by solvent replacement with methanol minimizes changes to the pore structure. Vacuum or oven drying severely reduces specific surface area and obscures important trends.It was found that capillary porosity in excess of 10 nm (100 Å) is essentially absent and that the pore volume measured can be considered an intrinsic part of the binding phase. The influence of silica fume and curing times on pore structure has been measured and the implications of the data will be discussed. Comparisons will be made with conventional cement pastes.

Improvements to needle-coke quality by pressure reductions from a tube reactor

Needle coke of excellent uniaxial orientation and thermal expansion of 0.6 × 10 −6/° C was produced at 460°C in a tube bomb from a low sulfur petroleum vacuum residue by reducing the carbonization pressure from 15 to 7 kg/cm 2G at the solidification stage. Both timing and rate of pressure reduction are critical to the uniaxial arrangement of mesophase molecules that governs the coke quality. Reduction of pressure before the formation of bulk mesophase or after the solidification did not induce an improvement. Excess gas evolution by the larger rate of pressure reduction creates excessive porosity, although the uniaxial arrangement may be improved. A too-small rate is not effective in modifying the lamellar arrangements at the solidification stage.

Reservoir Geology Of The Neilburg McLaren Pool, Lloydminster Region Of Saskatchewan

Abstract The Neilburg McLaren reservoir zone consists of tabular Lower and Upper McLaren Sands separated by a thin coal. The two sandstone reservoirs have a combined thickness of less than 7 m. The main trapping mechanism for the Lower Sand is formed by erosional channels filled by shaly and cemented rocks. The reservoirs typically consist of very coarse silt (Lower McLaren) and very fine sandstone (Upper McLaren). Despite the fine grain size, some Neilburg wells produce heavy viscous oil at initial rates up to 11 m3/d (70 barrels/day). The Lower Sand, although it contains more clay-size material and is finer and less sorted than the Upper Sand, has a larger porosity (33%) and permeability in excess of one darcy. Field operators report that large amounts of loose sand are produced with the fluids from the Lower Sand. A major objective of this study was to understand why this sand is produced. Our preliminary conclusion is that sand production at Neilburg is related to complete leaching of cementing material from the Lower Sand during digenesis. It is speculated that secondary porosity was also produced so that porosity and permeability were enhanced and oil productivity from the fine-grained reservoirs is anomalously high. Introduction This paper concerns the Neilburg McLaren Pool where sizeable reserves of heavy oil occur in tabular sandstones having an aggregate thickness of less than 7 m. The pool has a proclivity toward production of loose sand, but in many other respects it is reasonably typical of the numerous pools that produce from thin sheet like sandstones in the Lloydminster heavy oil belt. Work leading to this report was done through a Sand Control Studies project conducted jointly by the University of Regina and the Saskatchewan Heavy Oil Laboratory (now SRC Petroleum Division). The work was carried out under the Canada / Saskatchewan Heavy Oil/Fossil Fuels Agreement. Major objective of the study was to develop an understanding of the basic mechanism of sand production in the Lloydminster heavy oil belt. Geological work done by Richardson led to a B.Sc. (Hon.) thesis(1) at the University of Regina. A progress report concerning mainly stratigraphy and trapping mechanism was published by Richardson and Vigrass(2) in 1984. Contract reports, with Pappas and Vigrass(3,4) as principal authors, have been submitted to the Saskatchewan Department of Energy and Mines. Research on digenesis of Lloydminster sands will be continued by Richardson as part of her M.Sc. studies at the University of Regina. The reservoir zone at Neilburg consists of a McLaren Lower Oil Sand, which is topped by an underclay and thin coal seam, and a thin McLaren Upper Oil Sand. The pool occurs on a structural high but the main petroleum trap for the Lower Sand is formed by erosional channels filled with shaly and cemented rocks. The Lower and Upper Sands differ in several important aspects. Characteristically the Lower McLaren is very coarse silt and the Upper McLaren is very fine sandstone. Despite the small grain size, the Neilburg wells are prolific producers of viscous oil; initial production rates are as large as 11 m3/d (70 barrels/day) of oil with viscosity of about 0.5 Pa.s (500 centipoise).

Plasma sprayed Fe76Nd16B8 permanent magnets

Thin coatings (0.16 mm) and thick coatings (0.50 mm) of Fe76Nd16B8 were deposited on stainless-steel substrates by low pressure plasma spraying. Microscopic examination of the coatings in a light microscope revealed excessive porosity, but good bonding to the substrate. Fracture cross sections examined in a scanning electron microscope showed the grains to be equiaxed and approximately 1 μm or less in diameter in the as-sprayed condition. The intrinsic coercivities of the as-sprayed coatings varied from 5.8 to 10.9 kOe. The effects of post-spray heat treatments on the intrinsic coercivity are also given.

Leuko-araiosis: an ancient term for a new problem.

Recent research with computerized tomography (CT) and magnetic resonance imaging (MR) of the brain has revealed a type of tissue change for which no fitting term exists. The change appears as areas of decreased density on CT and changed signals of the white matter in MR images. Because neither a definite pathological change nor a specific clinical deficit has been linked with the CT and MR changes, a designation is required that limits itself to describing the changes themselves. We propose "leuko-araiosis". The Greek root leuko-, signifying "white", has found wide usage in modern medical terminology: e.g. leucine, leukocyte, leukorrhoea. Also several precedents exist for its application to the white matter of the central nervous system: e.g. leukoencephalitis, leukomyelitis, leukotomy. Araios is an adjective meaning "rarefield", and the suffix -osis converts the adjective to a noun meaning "rarefaction, diminution of density", a word used in the Hippocratic Collection to describe a state of excessive porosity of the lung. A descriptive term precludes premature presuppositions and encourages the search for causes.