Low-pressure Method Research Articles

Nanopore-Structure Analysis and Permeability Predictions for a Tight Gas Siltstone Reservoir by Use of Low-Pressure Adsorption and Mercury-Intrusion Techniques

Summary The pore structure of unconventional gas reservoirs, despite having a significant impact on hydrocarbon storage and transport, has historically been difficult to characterize because of a wide pore-size distribution (PSD), with a significant pore volume (PV) in the nanopore range. A variety of methods is typically required to characterize the full pore spectrum, with each individual technique limited to a certain pore size range. In this work, we investigate the use of nondestructive, low-pressure adsorption methods, in particular low-pressure N2 adsorption analysis, to infer pore shape and to determine PSDs of a tight gas silt-stone reservoir in western Canada. Unlike previous studies, core-plug samples, not crushed samples, are used for isotherm analysis, allowing an undisturbed pore structure (i.e., uncrushed) to be analyzed. Furthermore, the core plugs used for isotherm analysis are subsamples (end pieces) of cores for which mercury-injection capillary pressure (MICP) and permeability measurements were previously performed, allowing a more direct comparison with these techniques. PSDs, determined from two isotherm interpretation methods [Barrett-Joyner-Halenda (BJH) theory and density functional theory (DFT)], are in reasonable agreement with MICP data for the portion of the PSD sampled by both. The pore geometry is interpreted as slot-shaped, as inferred from isotherm hysteresis loop shape, the agreement between adsorption- and MICP-derived dominant pore sizes, scanning-electron-microscope (SEM) imaging, and the character of measured permeability stress dependence. Although correlations between inorganic composition and total organic carbon (TOC) and between dominant pore-throat size and permeability are weak, the sample with the lowest illite clay and TOC content has the largest dominant pore-throat size and highest permeability, as estimated from MICP. The presence of stress relief-induced microfractures, however, appears to affect laboratory-derived (pressure-decay and pulse-decay) estimates of permeability for some samples, even after application of confining pressure. On the basis of the premise of slot-shaped pore geometry, fractured rock models (matchstick and cube) were used to predict absolute permeability, by use of dominant pore-throat size from MICP/adsorption analysis and porosity measured under confining pressure. The predictions are reasonable, although permeability is mostly overpredicted for samples that are unaffected by stress-release fractures. The conceptual model used to justify the application of these models is slot pores at grain boundaries or between organic matter and framework grains.

저압주조방식에 의한 AZ91D 마그네슘 휠 특성

본 연구에서는 마그네슘 합금 AZ91D를 소재로 18인치 휠을 개발하고 동일사양의 알루미늄 휠과 해외 시판중인 마그네슘 휠과 기계적인 성질을 비교하였다. 저압주조 방식에 의해 18인치 마그네슘 휠 시제품을 제작하여 동일 사양의 알루미늄 휠 대비 26% 의 경량화를 이룩하였고, 신판 마그네슘 휠 대비 동등 수준의 연신율, 인장강도, 경도를 달성하였다. 향 후 주조와 열처리 공정 개선을 통해 항복강도 향상이 필요한 것으로 판단된다. In this study, 18-inch wheels, magnesium alloy AZ91D was developed and we compared overseas go on sale magnesium wheels and same specifications of the aluminum wheels mechanical properties. Prototype 18-inch magnesium wheels by a low-pressure casting method to achieve the same specifications of aluminum wheels and reduced 26% of the weight, the new edition of magnesium wheels compared to the same level of elongation, tensile strength, hardness. Casting and heat treatment process to improve future need to improve the yield strength is expected.

Studies of upconversion emission of Yb3+, Er3+:Lu2O3 nanoceramics

The translucent Yb3+ and Er3+ doped Lu2O3 ceramics composed of nanocrystalline grains were sintered using a low temperature and high pressure method. The upconversion emission associated with the 2H11/2→4I15/2, 4S3/2→4I15/2 (green), 4F9/2→4I15/2 (red) and 4I9/2→4I15/2 (IR) transitions was observed upon intense infrared laser excitation. The dependence of the upconversion intensity on incident laser diode power in Yb3+, Er3+:Lu2O3 nanoceramics was investigated. In particular it was found that the green/red intensity ratio of upconversion transitions increased with the power of the incident laser light. This effect was due to heating of the nanoceramics with increasing excitation power and may be utilized for high temperature thermometry.

Micromanufacturing in Fused Silica via Femtosecond Laser Irradiation Followed by Gas-Phase Chemical Etching

Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrogen fluoride (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure, as described in literature, consists of irradiating a silica slab followed by chemical etching using hydrogen fluoride. With aqueous HF the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of about 1.5 mm, while the use of low-pressure gaseous HF etchant can quickly produce 3 mm long channels with an aspect ratio (Length/Diameter) higher than 25. By utilizing this methodology the aspect ratio is not constant, but depends on the length of the channel. When the microchannel is short the aspect ratio increases quickly until it reaches a maximum length at around 1400 µm. Thereafter the aspect ratio starts to decrease slowly. In this paper we present a variation of the low-pressure gaseous HF etching method, which is based on the dynamic displacement of the etchant. This method results in a 13% increase in the aspect ratio (L/D = 29) at the expense of a low etching speed (4 µm/min).

Supercritical fluid extraction of Agaricus brasiliensis: Antioxidant and antimicrobial activities

The objective of this study was to obtain extracts from the mushroom Agaricus brasiliensis using supercritical fluid extraction (SFE) with pure CO2 and with CO2 plus 2.5%, 5.0% and 10.0% (w/w) of ethanol as co-solvent. In order to evaluate the high-pressure method in terms of process yield, extract composition and biological activity, low-pressure methods, such as maceration with ethanol (Mac), Soxhlet (Sox) with different organic solvents, and hydrodistillation (HD), were also applied to obtain extracts. The SFE conditions were temperatures of 313.15K, 323.15K and 333.15K and pressures from 10 to 30MPa. The SFE kinetics was investigated through the overall extraction curve (OEC). The extracts obtained by Sox with water and ethanol showed the best results for the global extraction yield. The best conditions in the studied range to obtain high yields using pure CO2 resulted to be 30.0MPa and 323.15K. The antioxidant potential of the extracts was evaluated by the DPPH method and by the Folin–Ciocalteau method. Maceration extract presented low yield, but good results of antioxidant activity by DPPH assays and total phenolic. The antimicrobial activity of the extracts was also studied. The main identified compounds in the extracts were linoleic and palmitic acids.

Investigation on heat transfer between two coaxial cylinders for measurement of thermal accommodation coefficient

The heat flux between two coaxial cylinders was measured in the range from the free molecular to the early transitional flow regimes for extraction of the thermal accommodation coefficient using an approximate relation on the pressure dependence of the heat flux. The experimental coaxial cylinders' geometry has been traditionally implemented for the measurement of the thermal accommodation coefficient using the low-pressure method; however, the actual experimental setup was characterized by large temperature difference and large cylinders' radius ratio. Compared to the original low-pressure method, much higher pressure range was applied. In order to verify assumptions in the accommodation coefficient extraction, the heat flux under measurement conditions was simulated numerically by the nonlinear S-model kinetic equation. Very good agreement was found between the measured and the simulated heat flux. The proposed procedure of the thermal accommodation coefficient extraction was discussed in detail and verified. The temperature dependence of the thermal accommodation coefficient was also found.

Design and Optimization of Bolster Casting Process

The low-pressure casting method has been used to the foundry process of bolster. According to the structural characteristics of the cast and the design process of low-pressure casting, the process programs had been accomplished. Through comparing the advantages and disadvantages of several group programs by computer simulation, after determining the initial process program, we optimized the casting process according observing the processes of cast filling and solidification by the computer simulation process of running castings. The risers and chills are very important. The contraction area of cast appears on the large flat, and the risers had been set on the large flat. This can not only play the role of feeding but also have the function of scavenging action.

Energy absorption mechanism of open-cell Zr-based bulk metallic glass foam

Open-cell Zr41.25Ti13.75Cu12.5Ni10Be22.5 bulk metallic glass foams were successfully fabricated by a low-pressure melt infiltration method using crude salts as a space-holder material. Detailed investigations were carried out on the energy absorption property and its underlying mechanism for the present foam. It is found that the foam exhibits high energy absorption capacity and absorbs energy efficiently. Further microscopic observations reveal that the bending of struts, formation and manipulation of multiple shear bands, and microcracking within the material contribute to this foam’s energy absorption capability.

Supercritical fluid extraction from spent coffee grounds and coffee husks: Antioxidant activity and effect of operational variables on extract composition

The present study describes the chemical composition and the antioxidant activity of spent coffee grounds and coffee husks extracts, obtained by supercritical fluid extraction (SFE) with CO2 and with CO2 and co-solvent. In order to evaluate the high pressure method in terms of process yield, extract composition and antioxidant activity, low pressure methods, such as ultrasound (UE) and soxhlet (SOX) with different organic solvents, were also applied to obtain the extracts. The conditions for the SFE were: temperatures of 313.15K, 323.15K and 333.15K and pressures from 100bar to 300bar. The SFE kinetics and the mathematical modeling of the overall extraction curves (OEC) were also investigated. The extracts obtained by LPE (low pressure extraction) with ethanol showed the best results for the global extraction yield (X0) when compared to SFE results. The best extraction yield was 15±2% for spent coffee grounds with ethanol and 3.1±04% for coffee husks. The antioxidant potential was evaluated by DPPH method, ABTS method and Folin–Ciocalteau method. The best antioxidant activity was showed by coffee husk extracts obtained by LPE. The quantification and the identification of the extracts were accomplished using HPLC analysis. The main compounds identified were caffeine and chlorogenic acid for the supercritical extracts from coffee husks.

Materials with extreme properties: Their structuring and applications

This article is a brief review on syntheses of materials with extreme properties and their modification by plasma processes to obtain different morphological structures. First we illustrate general methodologies on preparation of polycrystalline diamond (PD), nanocrystalline diamond (ND), cubic boron nitride (cBN), diamond/cBN multilayer films by low pressure methods. Since cBN synthesis is more challenging, we place more attention to cBN including its growth, structuring and doping. The structural compatibility of cBN and diamond enables the fabrication of multilayer (superlattices); and we describe such an approach to produce composite materials with even more extreme properties. The superior hardness, extreme thermal conductivity and high chemical stability make diamond and cBN well suited for cutting tool and tribological applications. Although doping of these wide bandgap materials for p- and n-type conductivity is difficult, recent works indicate considerable advancement. The combination of high chemical stability and thermal conductivity with attractive electronic properties makes diamond and cBN suitable for construction of high power electronic devices operating in harsh environments. The development of these applications relies on the ability to design patterns and control the film conductivity. We illustrate that despite diamond and cBN are chemically stable and inert against many chemicals, film patterning and device fabrication is possible with the use of plasma processing. Further, we discuss the fundamental issues involved and demonstrate feasibility for the design of practical applications such as deep-ultraviolet (DUV) detectors and surface acoustic wave (SAW) devices. Finally we discuss the existence of other composite materials with extreme properties that have been only barely investigated, and that present promising alternatives for the future commercial applications.

An Evaluation on Processing of Metal Matrix Composites (Al<sub>2</sub>O<sub>3</sub>/AC8A) by Low-Pressure Infiltration

At present many researches are about low density and high strength material, Metal Matrix Composite (MMC) is one kind of high performance material which is very popular and can fit that condition very well. In this study, matrix material is Al alloy and Al2O3 short fiber is reinforcement, volume fractions of Al2O3 short fiber is 10, 15 and 20 %. Manufacture by a low-pressure infiltration method. And the performance is evaluated by microstructure observation, porosity ratio and relative density. It is found that the porosity ratio can be effectively adjusted by the infiltration temperatures and the loads of Al2O3 short-fibres, exhibiting a minimum of 2 for 10% loading at 700°C. Meanwhile, the relative density of composites reached to be a maximum of 98% for 15% loading at 700°C. The low porosity ratio and high density of composites are reasonably attributed to the proper processing techniques.

Solid State Structures of Anhydrous 1-Aminoethylidenediphosphonic Acid

AbstractThe 1-aminoethylidenediphosphonic acid (AEDPH 4 ) is anhydrous when it is synthesized according to the U.S. Patent 4239695. It crystallizes in water to form hydrous crystal AEDPH 3 ·H 3 O (1). With the help of a simple low-temperature, low-pressure hydrothermal method and template 2,2′-bidpyridyl (2,2′-bipy), single crystals with the same structure of the anhydrous AEDPH 4 (2) is obtained. Compound 2 were characterized by elemental analysis (EA), infrared spectrometry (IR), thermogravimetric analysis (TGA) and X-ray single crystal diffraction. In compounds 2, the AEDPH 4 molecules are linked into 3D supramolecules by various hydrogen bonds.Graphical AbstractThe 1-aminoethylidenediphosphonic acid (AEDPH 4 ) is anhydrous. It crystallizes in water to form hydrous crystal AEDPH 3 ·H 3 O (1). However, the single crystal of the anhydrous AEDPH 4 (2), must be obtained via a simple low-temperature, low-pressure hydrothermal method and with 2,2′-bipy as template.[IMAGE]

Effect of low UD carbon fibre content on mechanical properties of in situ polymerised cyclic butylene terephtalate

Carbon fibre reinforced cyclic butylene terephtalate were produced by a low pressure method, the impregnating temperature and the cooling speed were investigated using plate–plate rheometry and differential scanning calorimetry. The effects of low fibre volume fraction of carbon fibre reinforcement (∼20 vol.‐%) on the mechanical properties were examined by tensile and flexural tests and Charpy dynamic impact test. The results showed a significant increase in Young’s modulus and ultimate strength and were supported by scanning electron microscopy pictures of the broken surfaces to study fibre wet‐out.

Powder injection moulding of metallic and ceramic micro parts

Industrial use of micro components is determined by the availability of efficient manufacturing techniques. While micro injection moulding of plastic is common practice, metal and ceramic powder injection moulding (PIM) still is under development. High-pressure and low-pressure injection moulding methods complement each other ideally, covering the entire spectrum from prototype to large-scale production. With high-pressure PIM, micro gear wheels with diameters <300 μm can be fabricated using LIGA mould inserts. Densities between 97 and 99% of the theoretical values are achieved. Apart from oxide ceramics, metal materials like copper or powder metallurgical steels like 17-4PH or 316L are often applied. Multi-component injection moulding requires less mounting steps and, hence, offers decisive advantages for effective production of interesting material combinations like electrically conductive/insulating or hard/ductile. Studies relating to the fabrication of immobile as well as mobile shaft-wheel components were performed. Other activities focussed on in-mould labelling with foils containing ultra-fine particles to improve surface quality and detail accuracy. Low-pressure injection moulding allows for the manufacture of small series within 1–4 weeks at low cost. However, the process has features which are not compatible with high-pressure PIM. Although use of a low-viscous feedstock is associated with various benefits, low-pressure injection moulding has not met with acceptance in micro moulding.

Understanding growth of carbon nanowalls at atmospheric pressure using normal glow discharge plasma-enhanced chemical vapor deposition

Synthesis of carbon nanowalls (CNWs) at atmospheric pressure is realized by using a negative normal glow discharge, which differs from prior low-pressure plasma-enhanced chemical vapor deposition methods for CNW growth and holds great potential for mass-production of CNWs. The glow discharge is characterized for electrical and optical properties. The resulting CNW structures are analyzed using transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. The CNW growth process is examined for effects of discharge regime, discharge duration (growth time), hydroxyl radicals (water vapor), and local current density. Possible CNW growth mechanism and critical process parameters to the CNW growth and evolution are identified. OH radicals play an essential role in the initial nucleation process, but excess OH radicals accelerate the oxidation of CNWs. For a fixed growth time, there exists an optimum feed gas relative humidity and an optimum current density (∼40% and ∼9.17 A/m 2, respectively, in the current work) for the growth of large and less defective CNWs with a high degree of crystallinity. Results obtained in this study can be used to tailor final properties of the as-grown CNWs for various applications.

Multisyringe ion chromatography with chemiluminescence detection for the determination of oxalate in beer and urine samples

The first multisyringe-based low-pressure ion chromatographic method is presented. It is based on the use of short surfactant coated octadecyl-silica monolithic columns. As a first application, we have determined oxalate in beer and human urine via post-column chemiluminescence detection. Oxalate is separated from the sample matrix in the monolithic column by precise programmable fluid handling, and then detected by reaction with on-line generated tris(2,2′-bipyridyl)ruthenium(III). Column coating, un-coating, ion chromatography and chemiluminescence detection are quickly performed by using a simple low-pressure multi-burette. The factors influencing the separation of oxalate and its subsequent detection, including the column coating with surfactants and its stability have been studied. The chromatographic behavior of the oxalate in presence of potentially interfering species also was assessed. The method has limits of detection and quantification of 0.025 and 0.035 mg L−1, respectively, a relative standard deviation of 3.1% (for 10 consecutive measurements without column re-coating) and a throughput of 48 h−1. The results obtained with real samples were validated by using an enzymatic spectrophotometric test. The method is critically compared to recent methods for the determination of oxalate.

Bioactive extracts of orange ( Citrus sinensis L. Osbeck) pomace obtained by SFE and low pressure techniques: Mathematical modeling and extract composition

The objective of this study was to obtain orange ( Citrus sinensis L. Osbeck) pomace extract using supercritical fluid extraction (SFE) with CO 2 and with CO 2 and co-solvent. In order to evaluate the high pressure method in terms of process yield, extract composition and biological activity, low pressure methods were also applied to obtain orange extracts, such as ultrasound (UE) and soxhlet (SOX), with different organic solvents, and hydrodistillation (HD). The SFE conditions were temperatures of 313.15 K and 323.15 K and pressures from 100 to 300 bar. The SFE kinetics and mathematical modeling of the overall extraction curves (OEC) were also investigated. The antioxidant potential of the extracts was evaluated by the DPPH method, by the Folin–Ciocalteau method and by the β-carotene/linoleic acid bleaching method. The antimicrobial activity of the extracts was also studied. The main compounds identified were l-limonene, palmitic and oleic acids, n-butyl benzenesulfonamide and β-sitosterol.

Fabrication of Carbon Nano-Fiber / Aluminum Composites by Low-Pressure Infiltration Method

In this study, the fabrication of carbon containing aluminum composites was attempted by using low-pressure infiltration method. At first, porous preform containing vapor grown nano-fiber (VGCF) and pure aluminum powder was fabricated by spark plasma sintering (SPS) method. Porosity in preform was controlled by changing the applied pressure during plasma sintering. Consequently, the porous preform with 40-50vol％ in porosity was obtained, which has enough compression strength for low-pressure infiltration (&lt;1MPa). Then, the molten pure aluminum infiltrated to porous preform with 0.4MPa in applied pressure at 1023K, and consequently we can obtain the composite with 62-86% in density. The electrical and thermal conductivity of composites was affected by the porosity, strongly.

Identification of carbon sensitization for the visible-light photocatalytic titanium oxide

The authors successfully synthesized titanium oxide (TiO2) nanopowder with visible-light photocatalytic ability by low-pressure flat-flame metal organic chemical vapor condensation method. In order to confirm that carbon doping is a viable mechanism for the visible-light absorption of the powder prepared by this method, they modify the process by total exclusion of nitrogen usage to eliminate the nitrogen doping possibility. Since nitrogen is avoided in the process, the visible-light absorption cannot be due to nitrogen doping. They also found that the nanopowder formed has a single phase of anatase. Thus the nanopowder does not have anatase/rutile interface, and the authors can eliminate the possibility of visible-light absorption by the anatase/rutile interface. The visible-light absorption should thus be resort to the carbon doping. X-ray photoelectron spectroscopy studies show the presence of several carbon related bonds except Ti–C bond. This suggests that the carbon does not incorporate into the TiO2 crystal and should locate on the surface of the nanopowder. Thus the carbon species act as a visible-light sensitizer for the TiO2 as a photocatalyst. Among all carbon bonds the C–C bond is believed to be responsible for the light absorption, since all other carbon related bonds are not chromophores. The visible-light TiO2 photocatalysis induced by carbon doping is confirmed and explained.

Effect of variable crucible dropping rate on solid‐liquid interface in CdZnTe crystal growth

AbstractThe Cd0.9Zn0.1Te crystal growth with low pressure and vertical Bridgman method (LPVB) was numerically simulated and analysed by the simulation software of Comsol Multiphysics. In the process of crystal growth, the influence of variable crucible dropping rate on solid‐liquid interface was studied in this paper. The variability of crucible dropping rate was achieved by a specifical furnace temperature distribution function, while the selection and analysis of crucible dropping rate was obtained by the combination of orthogonal experimental design method and regression analysis method. In this paper, the value of relative crystal growth rate was defined, and the influence of variable crucible dropping rate on solid‐liquid interface was discussed by comparing these values. The simulation results showed that if the crucible dropping rate was 3.5 mm/h (ν1) in the first stage and 0.6 mm/h (ν2) in the second stage, and the distance (d) between the bottom of crucible and the position of melting point in tempreture field was 0.02 m at the time of dropping rate change, the solid‐liquid interface was appreciably convex after 211 hours' growth, and the relative crystal growth rate was 0.45%, which made the solid‐liquid interface smooth and kept the crystal grow up spontaneously.