Fabrication Of Compact Research Articles

Micromorphological analysis on the influence of the soil mineral composition on short-term aggregation in semi-arid Mediterranean soils .

Aggregation in soils is the result of the interaction of the soil organic components and soil minerals. The reactivity of the mineral phase is acknowledged to interfere with aggregates formation and stabilization, but its influence on aggregation in semi-arid Mediterranean soils remains mostly unknown. In this study, we used micromorphological analysis of aggregates formed in a 28-d incubation in two agricultural soils differing only in the composition of the mineral phase in the upper Ap horizon (a carbonate-depleted Palexeralf with 21.5% clay, and a contiguous carbonate-rich Typic Calcixerept with 20.9% clay before decarbonation which was reduced to 10.4% upon decarbonation). The two soils belong to the same agricultural field and have had similar management for decades. Soil samples were completely disaggregated into their fractions < 250 μm, and incubated with fresh organic matter to stimulate re-aggregation. Macroaggregates (> 2 mm) formed during the incubation were separated at days 3, 7, 14, 21 and 28 and used to prepare thin sections. Macroaggregates were more abundant at day 3, and then decreased in number in the two soils, which indicates a dependency between organic matter decomposition and stable macroaggregates formation. They contained a greater proportion of smaller aggregates in the decarbonated soil. Micromorphological analysis revealed significant differences in the fabric and physical characteristics of these macroaggregates, in which bonds among primary particles were observed to be led by clays in the Palexeralf while the coarse fraction appeared embedded in a micromass with crystallitic b-fabric corresponding to carbonates in the Calcixerept. This resulted in a more compact fabric and less porosity in macroaggregates in the Calcixerept. Image analysis of thin sections was used to quantify and characterize the pore system of macroaggregates. Porosity (pores > 20 μm) was more than double (36.9% for 15.6%) within macroaggregates in the decarbonated soil, with more elongated pores. Although in both soils most pores were 20 to 150-μm in equivalent diameter, some porosity > 150 μm was observed only in macroaggregates from the decarbonated soil. These observations allow hypothesizing that the mechanisms responsible for aggregates stabilization and/or formation are different in the two soils, and that they result in different physical characteristics of soil aggregates. The implications of such differences on air and water flow rates within aggregates, and thus on the soil microbial activity and organic matter decomposition, as well as on soil erodibility, need to be studied and accounted for when evaluating the effect of soil management and other practices on soil quality in semi-arid Mediterranean agrosystems.

Données nouvelles surRhapydioninaStache, 1913 etFanrhapydioninan. gen., un groupe de Rhapydioninidae (Alveolinacea, Foraminifera) foisonnant en région périadriatique au Campanien-Maastrichtien

ABSTRACT New data about Rhapydionina Stache, 1913 and Fanrhapydionina n. gen., a bunch of Rhapydioninidae (Aveolinacea, Foraminifera) expanded in periadriatic area by Campanian-Maastrichtian time. Rhapydionina gr. liburnica and its flabelliform variant Fanrhapydionina flabelliformis n. gen., n. sp. are the most outstanding components of a group, part of the Rhapydionininae subfamily, widely expanded in restricted environments of the carbonate platforms in north-occidental Mediterranean area by Campanian-Maastrichtian time. This group, like all Alveolinacea, comprises chambers divided into “primary chamberlets” by radial secondary partitions (“cloisonnettes”) perpendicular to the wall, hollowed out near the septum as to give way to a preseptal undivided volume (“preseptal passage”), crossed only by faint “preseptal buttresses”, and like all Rhapydioninidae a compact fabric in the axial part of chambers (“central endoskeleton”) irregularly crossed by some “secondary chamberlets”. The distinctive features of...

Fabrication and characterization of liquisolid compacts of Embelin for dissolution enhancement

In the present investigation, an attempt was made to improve the dissolution properties of water insoluble herbal active ingredient, Embelin (EBN) by utilizing liquisolid technique, which might offer improved bioavailability. The compacts were prepared using Capryol 90 as non-volatile solvent, Neusilin as carrier and Aerosil 200 as coating material. Mathematical model and 32 factorial design with liquid load factor (X1) and drug concentration (X2) as the independent variables, was utilized to prepare the liquisolid powder systems. The prepared systems were subjected for studying micromeritic properties and possible drug-excipient interactions by fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Dissolution studies revealed improvement in the drug release properties. Physicochemical characterization of liquisolid compacts by FTIR, DSC and PXRD techniques suggested reduction in drug crystallinity elaborating for the dissolution enhancement. The study reveals that liquisolid technique is a promising alternative for enhancing dissolution characteristics of EBN.

Comparison between Slip Casting and Cold Isostatic Pressing for the Fabrication of Nanostructured Zirconia

Consolidation of ceramic parts may be achieved by several techniques, including the slip casting and cold isostatic pressing (CIP) methods. In the present work, the performances of the two methods are compared in the fabrication of nanostructured zirconia compacts for dental crown applications. First, a zirconia suspension suitable for slip casting was prepared. The rheological properties of the zirconia suspension were optimized by adding a dispersant agent and controlling the pH. Zirconia slurries were then slip-cast into a pellet. Second, another group of zirconia pellets were fabricated using uniaxial pressing and were then cold-isostatically pressed. Both slip-cast and CIP samples were sintered at 1300 °C with a soaking time of 2 hrs. The mechanical properties of both samples were compared. The samples prepared by slip casting were denser compared with those prepared via CIP. Slip casting technique produced samples with 98.8% of the theoretical density, which resulted in the high Vickers hardness (11.4 GPa) of the slip-cast samples. Morphological studies revealed that the microstructures of the slip cast-sample were more homogeneous and contain no porosity. The formation of such a structure is due to the enhancement of the particle packing efficiency by slip casting as well as to the removal of larger agglomerates by colloidal processing prior to casting. As a consolidation stage, slip casting appears to be more suitable than the CIP technique in preparing reliable nanostructural ceramic parts.

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A novel concept of bandpass filter (BPF) using distributed stub loaded highpass filter (HPF) and Defected Microstrip Structure (DMS) is proposed in this paper, which exhibits an ultra-wideband (UWB) property. The proposed design exhibits a bandpass response with WLAN rejection by combining the proposed DMS with the highpass filter design approach, also miniaturization is proposed to minimize the structure resulting in the pass band enhancement of the proposed filter with minimum insertion loss. The design consists of shorted stub microstrip transmission line on a substrate with relative dielectric constant 4.4 and thickness 1.59 mm. Its excellent bandpass property is verified by both simulated and measured results which show a result of 90.39% Fractional Bandwidth (FBW). The proposed UWB- BPF has an advantage of compact size, low cost and easy fabrication.

Processing and characterization of polymer precursor derived silicon oxycarbide ceramic foams and compacts

This work focused on the fabrication of silicon oxycarbide ceramic (SiOC) foams as well as dense compacts using poly(hydridomethylsiloxane) (PHMS) as a polymer precursor. The room-temperature cross-linking of PHMS was achieved by the addition of 1,4-diazabicyclo [2.2.2] octane (DABCO) with the release of hydrogen gas as a by-product. This resulted in self-blowing of the polymer precursor at room temperature and thereby offered the possibility of producing SiOC foams without the need of any external blowing agents. We also reported the fabrication of crack-free silicon oxycarbide compacts by cold compaction and pyrolysis route using polyvinyl alcohol (PVA) as a processing additive. Cylindrical-shaped pellets were pyrolysed at 1300 °C in argon atmosphere with a ceramic yield of approximately 85%. Increased resistance to phase separation and crystallization up to 1400 °C was attributed to the presence of large volume fraction of free carbon in the material which was confirmed by Raman spectroscopy.

Cost-Effective Integration of an a-Si:H Solar Cell and a ZnO TFT Ring Oscillator—Toward an Autonomously Powered Circuit

Cost-effective integration of a-Si:H solar cells and oxide-based thin-film transistor (TFT) circuits may lead to broader battery-free device applications. We demonstrate a n-i-p a-Si:H 15-series connected solar cell that supplies power to a ZnO-based ring oscillator. The ring oscillator can operate at 28 kHz at 6 V, corresponding to ≈100 mW/cm2 illumination. This letter describes the integration and compact fabrication of the a-Si:H solar cell and ZnO TFT ring oscillator. The fabrication process includes several mask steps to reduce the number of processing steps.

Critical issues in near net shape forming via green machining of ceramics: A case study of alumina dental crown

Green machining of ceramics through Computer Numerical Control (CNC) is efficient for near net shape fabrication due to minimum consumption of energy, less tool wear, and high material removal rate. However, there are numerous critical issues need to be addressed while manufacturing customized components through green state machining including fabrication of machinable green ceramics, designing of suitable mold for slurry casting, manufacture of suitable sample holders for mounting the fragile green samples during machining, and designing of machining tools for good surface finishing. This article introspects these critical issues and its possible solutions for efficient fabrication of dental crowns as a case study via green state machining. Highly loaded (55 vol%) alumina slurry was prepared for the fabrication of machinable dense alumina compacts by Protein Coagulation Casting (PCC) technique. Cylindrical alumina compacts were fabricated by casting alumina slurry into the polyvinyl chloride (PVC) mold. Metallic cylindrical sample holder was fabricated for mounting the green alumina samples for CNC machining. Diamond impregnated tool (∼3 mm diameter) was used for near net shaping of dental crown by grinding/milling. Dental crown (incisor) was successfully fabricated by optimizing different machining parameters.

Warm/cold rolling processes for producing Fe-6.5wt% Si electrical steel with columnar grains

A new technical prototype for producing Fe-6.5wt% Si electrical steel sheets by directional solidification, heat treatment before rolling, warm rolling, and cold rolling was proposed in the present study. The formability of Fe-6.5wt% Si electrical steel before rolling and the reasonable process parameters of this technical prototype were obtained. Experimental results reveal that the formability of Fe-6.5wt% Si electrical steel is improved significantly under the combination of directional solidification and heat treatment before rolling. Fe-6.5wt% Si electrical steel sheets with the thickness of 0.15 mm, bright surface, few edge cracks, and high rolling yield can be successfully fabricated using this technology without any intermediate annealing during the whole rolling. The combination of directional solidification, heat treatment before rolling, warm rolling, and cold rolling can work as a new process for highly efficient and compact fabrication of Fe-6.5wt% Si electrical steel sheets.

Miniaturized and high-selectivity substrate integrated waveguide (SIW) bandpass filter loaded by complementary split-ring resonators (CSRRs)

This paper presents an effective technique to obtain miniaturized and high-selectivity substrate integrated waveguide (SIW) bandpass filters by loading complementary split-ring resonators (CSRRs) at the SIW cavities. The existence of the CSRR enables a considerable reduction of the resonance frequency of a conventional SIW cavity thanks to the coupling effect between CSRR and SIW cavity. Besides, a sharp roll-off is generated in a higher stopband due to the characteristics of CSRRs. To demonstrate the operation principal, the second- and third-order SIW bandpass filters are fabricated using standard printed circuit board technology, showing advantages of compact size, good selectivity, easy fabrication, and integration with other circuits. The measured -parameters agree well with the simulated ones.

Enhancement of poly(3-hexylthiophene)-based solar cell with thermal-evaporated [6,6]-phenyl-C60 butyric acid methyl ester layers

We provide a more compact fabrication process than the prior work using [6,6]-phenyl C61-butyric acid methyl ester (PCBM) buffer layer to enhance the performance of organic solar cells. The device with an extra PCBM layer exhibits an improved power conversion efficiency (PCE) of 20% as compared with the devices with conventional structures. Ultraviolet and x-ray photoemission spectroscopy indicate that thermal annealing treatments result in better mixture structures of PCBM layers with poly(3-hexylthiophene) at the blended surfaces. Therefore, the device with inserted PCBM provides more ideal hetero-structures and vertically graded PCBM distribution to optimize the charge extraction efficiency.

Fabric evolution at basement–cover interfaces in a fold-and-thrust belt and implications for décollement tectonics (Autochthon, Lower Allochthon, central Scandinavian Caledonides)

Microstructural and magnetic investigations (anisotropy of magnetic susceptibility, AMS) on sections across basement–cover interfaces (BCI) revealed a complex evolution in the crystalline basement rocks beneath and in the basal units of the Caledonian fold-and-thrust belt: (1) Pre-Caledonian mylonitic fabrics in basement granite relate to steep shear zones. (2) Palaeoweathering formed smectite and illite at the expense of feldspar and mica. Secondary Fe-bearing clay minerals and the intensity of the chemical weathering control the bulk susceptibility. Changing susceptibility and AMS relate to a (time) sequence from primary magnetite to secondary paramagnetic clay to pyrite and ferrimagnetic pyrrhotite. (3) Burial compaction with BCI-parallel fabrics. (4) Caledonian cleavage, overprinted by decollement zones with S–C–C′ fabrics. Decollement cataclasis overprinted pre-existing magnetic fabrics and produced horizontal magnetic lineations and subhorizontal foliations defined by the S–C–C′ fabrics. Clay mineral enrichment, together with subsequent, BCI-parallel compaction fabrics, decreased the shear strength in the basement rocks beneath the BCI. Detachments initiated at such low-strength zones and produced allochthonous units with their footwall within crystalline basement rocks, an observation of general importance for orogenic fold-and-thrust belts.

Fabrication and Property Evaluation of Mo Compacts for Sputtering Target Application by Spark Plasma Sintering Process

Pure molybdenum compacts having a high density, purity and a fine-grained microstructure were fabricated by a spark plasma sintering process. Also, an optimized sintering condition was obtained by controlling process parameters such as temperature, pressure, and heating rate. Molybdenum compacts were prepared with diameters of ¯150 © 6.35mm, and the characteristics of the compacts were analyzed by induction couple plasma (ICP), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). In addition, molybdenum thin films that were fabricated on a glass substrate by using sputtering equipment were analyzed by XRD, transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS). A relative density of up to 99% and the grain size of below 8µm were reached at the sintering temperature of 1473.15K and the uniaxial pressure of 60MPa. Also, molybdenum compacts having a uniform relative density and grain size were fabricated through an optimully redesigned mold and process control method. The resistivity (³0.15 ®³m) of the optimized spark plasma sintering (SPS) molybdenum thin film showed properties that are similar to those of the film prepared with conventional sintering. [doi:10.2320/matertrans.M2012039]

Operational characteristics of a surface breakdown triggered vacuum switch with six gap rod electrode system

A triggered vacuum switch (TVS) is one of the important apparatuses in the field of pulsed power system. It has many advantages, such as wide working voltage range, high current capability, high transfer charge, flexible trigger system, high trigger reliability, rapid dielectric recovery, long life, compact fabric, low noise, etc. A small and compact sample of surface-breakdown TVS with six-gap rod electrode system was fabricated in this paper, and a test platform of TVS was set up. The test results show that, the TVS sample has working voltage of 0.05-28 kV, current peak of 225 kA and transfer charge of 45Cb. Due to the ceramic surface in the trigger gap, the time delay of TVS is controlled in less than 1.5 μs, and long trigger life is in prospect. Lastly, the working polarities are discussed, showing that the positive working mode is more reliable and advantageous.

Injection molding of surface modified powders with high solid loadings: A case for fabrication of translucent alumina ceramics

Solid loading is a critical key to the fabrication of ceramic compacts with high densities via ceramic injection molding. As reported in most previous work, solid loading of ultra-fine alumina feedstock system could be achieved only up to ∼58 vol% with stearic acid (SA) as the surface modification agent. In present work, different from the traditional work in which SA has been introduced just in the powder blending process, we have successfully prepared the feedstock with a much higher solid loading up to ∼64 vol% by a prior ball milling treatment of ceramic powders with a small amount of SA before the traditional blending process. It can be attributed to that SA can be coated homogeneously around the powder surfaces by a chemical reaction induced by ball milling treatment. Highly translucent Al 2O 3 ceramics have been fabricated, which suggests an alternative route for fabrication of translucent ceramics with high quality.

Fabric development in a weathering profile at a basement–cover interface, the sub-Cambrian peneplain, Israel: Implications for decollement tectonics

The present study examines a fossil saprock–saprolite–laterite-profile beneath the sub-Cambrian peneplain in the Pan-African Roded Granite, Israel, with regard to structure and magnetic fabrics (anisotropy of magnetic susceptibility, AMS), and image analysis of compaction. The deformed granite shows two pre-weathering foliations, S1m (magmatic) and S2g (gneissic). Pre-Early Cambrian weathering comprised weathering-brecciation in saprock and saprolite, and chemical weathering with clay-formation in saprolite and laterite. During subsequent Phanerozoic burial the laterite was vertically compacted to 73% of its original thickness. In the laterite, compaction produced an unconformity-parallel cleavage (S3d) with increasing intensity towards the unconformity. Bulk susceptibility (κbulk) and anisotropy (P′) decrease from the unweathered granite into the saprolite, as a result of progressive magnetite breakdown, martitization and weathering-brecciation. In the laterite, an enrichment of haematite and relic Fe–Mg–mica lead to increased κbulk. Here, magnetic fabrics trace the compaction fabrics. The subhorizontal, compactional clay–/mica-fabric S3d defines a structurally weak and impermeable layer. The mechanical weakness of a clay-enriched weathering horizon with an unconformity-parallel, planar shape-preferred orientation, combined with the potentially overpressured state due to the sealing character of such a zone provides a viable explanation for the abundant localization of decollement horizons at or beneath basement-cover interfaces.

Origin and palaeoenvironmental significance of lamination in stalagmites from Katerloch Cave, Austria

AbstractThe origin and environmental dependencies of lamination in stalagmites from Katerloch, common in speleothems from other cave sites, are examined in detail. Petrographic observations and chemical analyses (including isotopes) of stalagmites and modern calcite were combined with multi‐annual cave monitoring. All investigated stalagmites are composed of low‐Mg calcite and show white, porous laminae and typically thinner, translucent dense laminae. The binary lamination pattern results from changes in the calcite fabric: white, porous laminae are characterized by a high porosity and abundant fluid inclusions and also by enhanced vertical growth and thinning towards the flanks. Translucent, dense laminae exhibit a compact fabric and constant thickness of individual growth layers. U‐Th dating supports an annual origin of the lamination and the seasonally changing intensity of cave ventilation provides a robust explanation for the observed relationships between lamination, stable C isotopic compositions and trace elements (Mg, Sr and Ba). The seasonally variable air exchange, driven by temperature contrasts between the cave interior and outside atmosphere, modulates the rate and amount of CO2 degassing from the drip water and affects the hydrochemistry and consequently the fabric of the precipitating calcite. Although cave air composition and drip rate are both major variables in controlling CO2 degassing from the drip water, the seasonally changing ventilation in Katerloch exerts the primary control and the results suggest a secondary (amplifying/attenuating) influence of the drip rate. Drip rate, however, might be the controlling parameter for lamina development at cave sites experiencing only small seasonal cave air exchange. Importantly, the seasonally variable composition of drip water does not reflect the seasonal cycle of processes in the soil zone, but results from exchange with the cave atmosphere. The alternating porous and dense calcite fabric is the expression of a variable degree of lateral coalescence of smaller crystallites forming large columnar crystals. The white, porous laminae represent partial coalescence and form during the warm season: low calcite δ13C values are linked to low δ13C values of cave air and drip water during that time. This observation corresponds to times of reduced cave ventilation, high pCO2 of cave air, low drip water pH, lower calcite supersaturation and typically high drip rates. In contrast, the translucent, dense laminae represent more or less complete lateral coalescence (inclusion‐free) during the cold season (high calcite, drip water and cave air δ13C values), i.e. times of enhanced cave ventilation, low cave air pCO2, increased drip water pH, relatively high calcite supersaturation and typically low drip rates. In essence, the relative development of the two lamina types reflects changes in the seasonality of external air temperature and precipitation, with a strong control of the winter air temperature on the intensity of cave‐air exchange. Thick translucent, dense laminae are favoured by long, cold and wet winters and such conditions may be related closely to the North Atlantic Oscillation mode (weak westerlies) and enhanced Mediterranean cyclone activity during the cold season. Studies of speleothem lamination can thus help to better understand (and quantify) the role of seasonality changes, for example, during rapid climate events.

Fabrication of Porous Structured WC-Co Alloy Compacts by Indirect Laser Forming

Fabrication of Porous Structured WC-Co Alloy Compacts by Indirect Laser Forming

COMPARISON BETWEEN MECHANICAL PROPERTIES OF FABRICS WOVEN FROM COMPACT AND RING SPUN YARNS

Abstract Due to the elimination of spinning triangle in compact spun yarns, its mechanical and physical properties differ significantly from ring spun yarns. The difference between the two spun yarns is reflected in the properties of fabrics woven from both. This study is aimed to compare the mechanical properties of fabrics which are produced from yarns spun from 100% Egyptian cotton, Giza 86 on these systems. Statistical analysis revealed that there is no significant difference between both type of fabrics regarding tear strength and abrasion resistance. But in relation to tensile strength, air permeability and stiffness, compact fabrics were superior to ring fabrics.

Rapid, high-temperature formation of large-scale rheomorphic structures in the 2.06 Ma Huckleberry Ridge Tuff, Idaho, USA

In the Teton River Canyon, eastern Idaho, the ca. 2.06 Ma, 130-m-thick Huckleberry Ridge Tuff exhibits large-scale rheomorphic fold geometries defined by eutaxitic fabrics parallel to both the primary internal zonation and the basal contact with older strata. Paleomagnetic data from a large-amplitude (>150 m), northwest-trending, overturned fold near the failed Teton Dam indicate folding above maximum magnetization unblocking temperatures (>580 °C). The in situ characteristic remanent magnetization (ChRM) direction is indistinguishable from previous studies of undeformed Huckleberry Ridge Tuff, and a fold test is negative ( k minimized at 100% unfolding). Anisotropy of magnetic susceptibility data reveal magnetic foliation planes that dip northeast, roughly parallel to the axial surface of the fold. Because deformed and undeformed Huckleberry Ridge Tuff exposures preserve the same anomalous ChRM direction, large-scale rheomorphic structures in the tuff must have formed rapidly at high temperatures shortly after development of compaction fabrics. Post-welding, high-temperature deformation is consistent with field evidence indicating rapid, plastic secondary deformation of much of the tuff prior to devitrification.