Gas Permeability Values Research Articles

HYDROPHOBISATION OF WATER-DISPERSION PAINT AND VARNISH MATERIAL WITH POLYSILOXANE EMULSION

The modern market of paint and varnish materials is represented by a wide range of construction products, including those designed to protect facades of buildings and structures from atmospheric impact. Among the variety of varnishes and paints for processing and rendering decorative and protective properties to building materials, as well as from the viewpoint of environmental friendliness, the most popular products are water-dispersion paints based on acrylic dispersions. However, along with the high values of colour fastness, UV resistance and gas permeability, acrylic-based paints are insufficiently elastic and lack resistance to water. In this regard, the paper considers a method for increasing the mechanical and hydrophobic properties of acrylic paint and varnish material by introducing a hydrophobic polyethylhydrosiloxane-based emulsion containing polyethylhydrosiloxane (PEHS) - 35.20, glutaric aldehyde - 0.19, polyvinyl alcohol (PVA) - 7.75, water - 56.86 wt%, as well as by increasing the surface development (relief), achieved by increasing the volumetric concentration of pigments (VCP). The optimal range of the amounts of a hydrophobic emulsion and a coalescent into the composition of water-dispersion paints based on acrylic dispersion has been determined. To assess the stability of the coating after drying an aqueous dispersion paint modified with the aqueous polyethylhydrosiloxane emulsion, the wetting angle and free energy of the surface were evaluated using two liquids of different polarities, namely distilled water and diiodomethane. The possibility of modifying the aqueous dispersion paint, characterised by VCP of 70-80 %, by the polyethylhydrosiloxane hydrophobic aqueous emulsion in the amount of 5-5.5 %, combined with ethylene glycol (4.5-5.5 %) has been established, which makes it possible to obtain a hydrophobic coating with a wetting angle of up to 100°. By comparing the wetting angle values of the coatings, it has been shown that in the absence of the hydrophobic additive, this parameter is lower by 12.5 % than the parameter of the modified sample.

Effects of stone powder on microstructure of manufactured-sand concrete and its gas permeability

With the development of infrastructure construction, natural sand resources have become increasingly scarce, and the use of manufactured sand has become inevitable. The unique stone powder in manufactured sand could significantly influent the concrete performance. To characterize the stone powder, a physical filling model was used to quantify the particle grading buildup. Isothermal calorimetry and thermogravimetric analysis determined the corresponding chemical activities. Subsequently, non-destructive testing flow methods were designed, referred to as nuclear magnetic resonance (NMR) and hydrostatic balance (HB), to test the pore structure, and a quasi-stationary flow method was used to test the gas permeability of the manufactured sand concrete. Finally, a random hierarchical bundle model using the NMR-HB method was proposed to predict the gas permeability of concrete based on the pore size distribution. The results showed that a moderate amount of stone powder could reduce the heat of hydration, increase the hydration products, improve the filling effect, and decrease gas permeability. A certain fineness of the stone powder could increase the heat of hydration, increase the hydration products, compact the pores from 4.5 to 50 nm, reduce the filling effect, and increase gas permeability. The maximum relative difference between the predicted and experimental gas permeability values of the random tube bundle model was reduced to 34.38 % using the NMR-HB method, whereas this value was 70.87 % using the mercury intrusion porosimetry (MIP) method.

Improving the technology of obtaining highquality castings from steel in sand-clay molds

This article examines the technology for producing high-quality steel and alloy castings in sand-clay molds. The optimization of the sandclay compound mold composition is explored, focusing on bentonite and kaolin clays as binders. The mold composition is refined based on the research conducted on these binding clays, resulting in the production of gas-free cast products. Additionally, the gas permeability of the sand-clay molds increased by 14-16%. The study also presents a test analysis of the gas permeability property, a crucial aspect of sand-clay mold quality. Furthermore, a mathematical model of the process was developed from the research findings to predict gas permeability values with varying amounts of binding clays, eliminating the need for further testing.

Justification of the boundary values of open porosity and gas permeability using data from flow studies for porous carbonate reservoirs

This paper proposes a method for determining the boundary values of open porosity (KPO_GR) and gas permeability (KPR_GR) of porous-type carbonate reservoir rocks using the example of Tournaisian deposits of one of the oil fields of the Republic of Tatarstan. When justifying the boundary values, two databases on core studies are used: 1) on standard core studies (used mainly to calculate hydrocarbon (HC) reserves); 2) on special core studies (used for technological development projects). In the proposed method, the residual oil saturation factor is not a constant, but is taken from flow studies or calculated from core dependencies. When determining the lower limits of porosity and permeability from both databases, approximately the same boundary values were obtained: KPO_GR = 0.11 fr. un., KPR_GR = 2·10–3 μm2 and KPR_GR = 1.7·10–3 μm2, but they differ from the values, accepted by petrophysicists when calculating the reserves of considered deposit – KPO_GR = 0.09 fr. un., KPR_GR = 1·10–3 μm2. Such a difference in determining the boundary porosity can significantly affect the calculation of hydrocarbon reserves, technological calculations and field development planning.

Effect of Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes on Structure-Property Relationships of Thermostable Hybrid Cyanate Ester Resin Based Nanocomposites.

Nanocomposites of cyanate ester resin (CER) filled with three different reactive amino-functionalized polyhedral oligomeric silsesquioxane (POSS) were synthesized and characterized. The addition of a small quantity (0.1 wt.%) of amino-POSS chemically grafted to the CER network led to the increasing thermal stability of the CER matrix by 12-15 °C, depending on the type of amino-POSS. A significant increase of the glass transition temperature, Tg (DSC data), and the temperature of α relaxation, Tα (DMTA data), by 45-55 °C of the CER matrix with loading of nanofillers was evidenced. CER/POSS films exhibited a higher storage modulus than that of neat CER in the temperature range investigated. It was evidenced that CER/aminopropylisobutyl (APIB)-POSS, CER/N-phenylaminopropyl (NPAP)-POSS, and CER/aminoethyl aminopropylisobutyl (AEAPIB)-POSS nanocomposites induced a more homogenous α relaxation phenomenon with higher Tα values and an enhanced nanocomposite elastic behavior. The value of the storage modulus, E', at 25 °C increased from 2.72 GPa for the pure CER matrix to 2.99-3.24 GPa for the nanocomposites with amino-functionalized POSS nanoparticles. Furthermore, CER/amino-POSS nanocomposites possessed a higher specific surface area, gas permeability (CO2, He), and diffusion coefficients (CO2) values than those for neat CER, due to an increasing free volume of the nanocomposites studied that is very important for their gas transport properties. Permeability grew by about 2 (He) and 3.5-4 times (CO2), respectively, and the diffusion coefficient of CO2 increased approximately twice for CER/amino-POSS nanocomposites in comparison with the neat CER network. The efficiency of amino-functionalized POSS in improving the thermal and transport properties of the CER/amino-POSS nanocomposites increased in a raw of reactive POSS containing one primary (APIB-POSS) < eight secondary (NPAP-POSS) < one secondary and one primary (AEAPIB-POSS) amino groups. APIB-POSS had the least strongly pronounced effect, since it could form covalent bonds with the CER network only by a reaction of one -NH2 group, while AEAPIB-POSS displayed the most highly marked effect, since it could easily be incorporated into the CER network via a reaction of -NH2 and -NH- groups with -O-C≡N groups from CER.

Effect of incorporation of multi-walled carbon nanotubes on the CO2/CH4 separation performance of sulfonated poly (ether ether ketone) / polyetherimide composite membranes using design of experiments and molecular dynamics simulation methods

Blend membranes were prepared based on sulfonated poly (ether ether ketone) (SPEEK) and poly (etherimide) (PEI) using different amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 wt%). PEEK has been sulfonated directly to reach 70 % degree of sulfonation. The manufactured membranes were examined by X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). The effect of the composition of SPEEK / PEI on membrane selectivity was investigated under different feed pressures (2 to 8 bar) and temperatures (25 to 55 °C). The values of selectivity and gas permeability were varied between the value of the individual polymers, fluctuating systematically with SPEEK / PEI content variation in the blends. TGA and tensile tests result obtained for prepared membranes shown that the hybrid membrane had good thermal and mechanical properties. The addition of MWCNTs to the blend led to simultaneously improve the selectivity and permeability of the pair gases of CO2 and CH4. The permeability of CO2, as well as CH4/CO2 selectivity for the membrane with the same weight of SPEEK and PEI, and 1 wt% of MWCNTs (coded SP55M1) experienced an increase of about 22 % compared with the neat membrane. Molecular dynamics simulations (MDS) were performed by employing the COMPASS force field to estimate the diffusivity of CH4 and CO2 gases through selected membranes. At last, with compared to the obtained experimetal data, the optimized nanocomposite membrane, integrated with MWCNTs was efficient, which makes it promising platform to separate mixed gase flows of CO2 and CH4 and other related environmental processes.

ZIF-8 @polycarbonate nanocomposite membranes for improved permeability and selectivity for hydrogen gas.

Through this work, we are reporting high-performance ZIF-8 @polycarbonate nanocomposite membranes with satisfactory structural stability for improving the gas separation performance. ZIF-8 nanoparticles were synthesised using the wet chemical route with cubic morphology and controlled size using CTAB as a surfactant. The membranes were prepared using the solution casting method by adding ZIF-8 filler at various concentrations. The synthesised filler material and MMMs were characterised through X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), andRAMAN spectroscopy techniques. The gas separation measurements were taken using H2, CO2, and N2 gas in the purest form. The SEM results confirm the formation of spherulite-like morphology with the addition of ZIF-8 due to the crystallisation of the polymer, which increased the membrane's free volume and opened up additional pathways for the transportation of the gas molecules. The gas separation results confirmed that the 15 wt% ZIF-8/PC nanocomposite membrane showed the maximum H2 permeability of 180,970 barrer with an increment of 316.03%, while H2/CO2 and H2/N2 selectivity showed the increments of 89.43% and 103.64%, respectively. Therefore, this PC/ZIF-8 system seems to be a promising approach to developing new H2 selective membranes with high gas permeability and gas selectivity values.

Effects of MWCNTs on O2/N2 separation performance and morphology of sPEEK/PEI composite membranes: Experimental and molecular dynamics simulation studies

This study involved the development of blend membranes using sulfonated poly (ether ether ketone) (sPEEK) and poly (etherimide) (PEI) with varying amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 % by weight). The gas separation performance of these membranes was evaluated for the separation of O2 and N2 gases. In order to achieve a degree of sulfonation of 70 %, PEEK was sulfonated directly. The manufactured membranes were characterized using X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). Their operational evaluation was performed through permeability tests for pure gases of O2 and N2. The effect of sPEEK/PEI composition on membrane selectivity and gas permeability in the blend was studied. The selectivity and gas permeability values varied between those of individual polymers, fluctuating systematically with sPEEK/PEI content variation in the blends. The addition of MWCNTs to the blend improved the selectivity and permeability of O2 and N2 simultaneously. To further investigate the potential industrial application and stability of these membranes, experiments were conducted under different feed pressures (2 to 8 bar). The membrane containing 1 % of MWCNTs showed the best performance for O2 gas. Molecular dynamics simulations (MDS) were performed using the COMPASS force field to estimate the diffusivity of O2 and N2 gases through selected membrane systems. The simulated results agreed well with the available experimental data. With compared to the reported separating data, the prepared nanocomposite membrane was greatly efficient, which makes it promising platform to separate mixed gas flows and other related environmental processes.

Study of the hygroscopic properties of three Australian wood species used as solid wood and composite products

The use of engineered wood products and mass timber panels such as cross laminated timber (CLT), glued laminated timber (glulam) and laminated veneer lumber (LVL) is becoming more common, as these products have benefits in terms of environmental credentials and resource utilisation and have the potential to provide faster and more economical construction processes. However, timber exposed to moisture for prolonged periods can degrade biologically, leading to a loss of appearance and decreased mechanical properties. Southern pine, radiata pine and shining gum timber are important forest resources for the Australian timber industry. To date, no in-depth studies on the hygroscopic properties of these species have been carried out from a timber wetting point of view. Consequently, existing literature has a knowledge gap regarding the determination of moisture movement properties in these species that are applicable to numerical modelling when used as solid wood or in the production of engineered wood products (EWPs). The work presented herein will help develop a better understanding of moisture ingress and egress in solid timber and EWPs and provide data for future predictive tools (such as numerical modelling) for moisture management in timber buildings. Samples were prepared from solid timber as well as EWP’s to examine the relationships between glue lines and edge gaps in CLT and multiple glue lines in LVL on moisture movement. As expected, longitudinal permeability was higher than radial and tangential permeability for the species tested. Southern pine samples had higher gas and liquid permeability values than radiata pine and shining gum. CLT with end grain sections including an edge gap had higher gas and liquid permeability than similar sections with glue lines only. LVL sections with 1 glue line had slightly lower permeability values than in samples with 2 glue lines. Gas and liquid permeabilities were lower for LVL samples than a two-layered veneer section without a glue line illustrating the barrier posed by the glue line. The moisture loss parameter during the diffusion testing was higher for LVL ends and CLT ends with edge gaps than face and edge sample sections. The results will be used to develop numerical models for moisture behaviour in solid and composite timber panels when exposed to humidity and free water. It is recommended to conduct additional studies to examine the impact of the adhesive layer and its properties on impeding moisture migration or functioning as a moisture barrier.

Estimated versus field measured soil gas radon concentration and soil gas permeability

Prediction of areas with elevated natural radiation is fundamental for the prevention of human exposure. Soil gas radon activity concentration and soil gas permeability are predictive parameters for the radon potential, which has great importance in areas where future urban development is planned. In this study, the soil gas radon equilibrium concentration (C∞) and soil gas permeability (K) were estimated through the application of theoretical and empirical models found in the literature. These models apply soil properties as input parameters. Using already existing soil parameters to predict the radon potential of an area would be useful in avoiding direct field measurements. Therefore, in this study, we examined whether the estimated soil gas radon activity concentration and soil gas permeability values match the values measured in the field. The soil gas radon activity concentration estimated by two theoretical models is about 50% of the measured value in the studied area. This underestimation can be attributed to the assumption that the radon activity concentration measured in the field depends only on soil parameters and the models do not take into account the underlying bedrock. Additionally, these models neglect the radon transport by advection and consider only the radon availability and migration in homogeneous media. Furthermore, they do not count certain characteristics of the soil that can be relevant, e.g. organic matter and clay content in the soil. To investigate more in detail such soil characteristics, seven samples located roughly along the slope, were selected to determine the soil chemical composition by ICP-MS. Evaluating the physical and chemical properties of the soil, it was found that the sampling sites with pH < 8 (low calcium content) the preferential adsorption was a dominant process. This causes radium enrichment in organic matter and clay, which directly influence the soil gas radon activity concentration. At pH > 8, radium is no longer preferentially adsorbed on organic matter but continues to be adsorbed on clays albeit this process is weak because radium competes with calcium cations. Also, there are other factors that may affect radon emanation in soil such as radium concentration and distribution, porosity and water content. In contrast, empirical model of soil gas permeability overestimates the measured value in the study area by an order of magnitude. A new model was made by modifying the previously proposed one, which can be used as a guide for the estimation of the median value of soil gas permeability in granitic areas, but not as an accurate predictor due to the lack of correlation between the estimated and measured values.

Effect of Coarse Aggregate Content on Bubble Formation Behavior in Corundum Permeable Brick for Tundish

Herein, corundum porous permeable bricks with different coarse aggregate contents are prepared using particle packing method. Based on the similarity principle, a local water model of a tundish is designed to investigate the bubbling behavior in porous permeable bricks at various argon flow rates. Through dimensionless analysis, empirical formulas of bubbling region diameter and initial bubble size in porous permeable bricks are proposed. The results show that an increasing aggregate content can increase the apparent porosity and the proportion of large pores, reduce the surface fractal dimension of the porous permeable bricks, and obtain a higher gas permeability. With the increase of argon flow rate and the decrease of gas permeability, the internal pressure gradient in porous permeable bricks increases. The larger the argon flow rate and the gas permeability value, the more beneficial it is to activate more pores and form a larger bubbling region on the upper surface of porous permeable bricks. The Sauter mean diameter of bubbles and the initial velocity of gas plumes are inversely correlated with the content of coarse aggregate; that is, the porous permeable brick with a higher content of coarse aggregate is beneficial to generating much more small bubbles.

Constraints on Magma Properties at Fragmentation During the 2011 Sub‐Plinian Eruptions of Kirishima Shinmoe‐dake Volcano, Japan

AbstractWe investigated essential factors controlling magma fragmentation during the 2011 sub‐Plinian eruptions of Kirishima Shinmoe‐dake volcano, Japan, based on observational data and the analysis of the conduit flow system. Key observational data of the Shinmoe‐dake eruptions are geophysically estimated magma discharge rate and petrologically measured crystallinity and porosity at the time of fragmentation. Using formulations of fragmentation criterion and conduit flow model, we derived analytical expressions describing the relationship among magmatic and geological parameters at the time of strain rate‐induced or stress fragmentation. The combination of the observational data and the analytical expressions revealed the relationship among weakly constrained parameters at the fragmentation, such as pressure, gas permeability in the magma, conduit radius, and maximum packing fraction of crystals, β*. From this relationship, we found that a smaller β*, less than approximately 0.5, is necessary for the fragmentation to occur for a wide range of the conduit radii under realistic pressure and gas permeability values. This reflects that in the case of the sub‐Plinian eruption with a moderate magma discharge rate, a drastic increase in magma viscosity induced by the smaller β* plays a crucial role in the occurrence of fragmentation. The strong dependence of the fragmentation process on β* indicates that the suspension rheology of crystal‐bearing magma is an essential factor controlling the magma ascent process during the moderate explosive eruption.

Influence of a Hydride-Forming Multi-Component Alloy on the Carbonization Behavior of Vulcanized Elastomer Composites

In this work, composites based on a hydride-forming fiber of a multi-principal-component (MPC) Ti20Zr20Nb20V20Hf20 alloy, carbosil, dicumylperoxide and nitrile butadiene rubber (NBR) matrix were obtained. The composites were prepared in a three-stage process including the mixing of elastomeric compounds via a rubber mixing mill and low-temperature vulcanization by heat pressing. Using dynamical mechanical analysis (DMA) and differential scanning calorimetry (DSC) the effect of the metallic filler on the process of carbonization of the composite elastomeric matrix was studied. The microstructure and gas separation properties of the resulting composites were also studied. The results showed that the filler content increase in the elastomeric matrix leads to a noticeable and gradual decrease in the activation energy of the carbonization process, reduces the temperature of this process, and accelerates the growth of the elastic modulus during carbonization. It was shown that the finely dispersed fiber of the MPC acts as an activation center for the process of thermal-oxidative degradation in the elastomeric matrix accompanying the onset of carbonization. The gas permeability values were found to be relatively low and no visible correlation with the MPC alloy content in the composite membrane was observed.

Zeolite-templated sub-nanometer carbon nanotube arrays and membranes for hydrogen storage and separation

Adsorbents and membranes consisting of carbon nanotube (CNT) pores with diameters of molecular dimensions are highly desirable for hydrogen storage and selective, high-flux membrane separation. However, fabrication of such materials with precise pore sizes and monodispersity as well as evaluation of the mechanisms associated to adsorption and molecular transport are challenging. Herein, we grew aluminophsphate zeolites (CoAPO-5, AFI crystal structure) consisting of one-dimensional, monodisperse parallel pores with diameter of ∼7 Å, and utilized them as templates to grow singe-walled CNTs (SWNTs) inside the pores. The resulting materials were examined as adsorbents and membranes for hydrogen storage and separation, respectively, using single-gas and real mixture feeds. Detailed mechanistic analysis and fundamental investigation of permeance and adsorption behavior of the resulting CNT-in-zeolite systems via combined adsorption, equilibrium, and kinetic studies were carried out. A superior gravimetric hydrogen uptake of 1.2 wt% at 35 °C and 1 bar was achieved in the case of the SWNTs grown in the cobalt-richer AFI host. Permeability measurements were performed on the respective Co(x)APO@SWNT membranes with the Co-richAPO@SWNT membrane exhibiting the highest permeance for all studied gases as a consequence of larger and more densely packed AFI crystals along with higher number of SWNT-filled pores, assets attributed to the higher Co catalyst content. Notably, the produced composite membranes exhibited gas permeability values that were two orders of magnitude higher than what predicted by the Knudsen mechanism.

Synthesis of new copolyimides containing pyridine and morpholine groups for gas separation through molecular design and simulation

AbstractThrough one‐step copolymerization of 4‐(4‐[1‐morpholinyl]phenyl)‐2,6‐bis(4‐aminophenyl)pyridine (MPAP), 9,9‐bis(4‐aminophenyl)fluorene (BAFL), and (4,4′‐hexafluoroisopropylidene)diphthalic anhydride (6FDA), a series of polyimides containing morpholine group, pyridine ring, fluorene “cardo” pendant and hexafluoroisopropyl group are obtained. The synthesized polyimides have good thermal stability, high transparency, outstanding hydrophobicity and excellent solubility in not only high‐boiling solvents but also low boiling‐point solvents. Furthermore, polyimide films have large molecular chain spacing, which is consistent with the free volume calculated by molecular simulation. Consequently, polyimide membranes display better gas permeability values of CO2 (up to 24.47 Barrer) and He (up to 45.04 Barrer), and good ideal gas selectivity values of CO2/N2 (up to 15.33 Barrer) and He/N2 (up to 23.89 Barrer), which also shows potential application of polyimide matrix materials in gas separation.

Investigation of transport properties of 6FDA-durene polymeric membrane for landfill gas application using molecular simulation approach

Gas separation of carbon dioxide (CO2) and methane (CH4) from landfill gas (LFG) is very crucial to be undertaken to treat significant greenhouse gases (GHG) emitted to the atmosphere. Among the well-developed conventional technologies, membrane has drawn a huge attraction from many researchers to leverage on its application, which favors an efficient and environmentally safe process. In membrane technology, inorganic membrane type requires a complex and pricey fabrication process which is contradictory from the polymeric membrane features. The impressive gas permeability and acceptable value of selectivity possessed by polymeric membranes has contributed to its main attractiveness over the other types of membranes available. Besides, the frequent approach used which is through experimental methods requires complicated procedures and possess high difficulty to obtain a defect-free membrane sample. In this work, 6FDA-durene has been investigated by employing a molecular simulation approach to further examine its fractional free volume within the membrane matrix and transport properties. The structure creation of complete framework and the analysis of project deliverables has been adopted through a molecular dynamic simulation in Materials Studio software. FFV value obtained based on the simulated framework is 0.1743 which establishes about 3.15% deviation to the published experimental works. Upon the increment of operating temperature, most of the gasses would be in their activation condition and possess higher gas diffusivities and permeabilities. However, with increasing operating pressure simulation, the membrane framework was compressed and reached its asymptotic limit at 7 atm which acts as a maximum point when the membrane system becomes saturated. In both cases, the selectivity of CO2/CH4 gas pairs are validated with low percentage deviation (less than 10%) towards the reported experimental works hence affirms the reliability of results and methodology conducted.

Epoxidized natural rubber/acid functionalized carbon nanotubes composites for enhanced thermo‐mechanical and oxygen barrier performance

AbstractHerein, acid functionalized carbon nanotubes (FCNTs) reinforced epoxidized natural rubber (ENR 25) composites with 25% epoxidation are studied with particular reference to the effect of FCNTs on microstructural development along with their effect on thermo‐mechanical and gas barrier properties. Excellent improvement in tensile strength, that is, 128% and 118%, was observed with the addition 1 and 2 wt% of FCNTs, respectively, without compromising the elongation at break. A 76% improvement in oxygen impermeability was found for 2 wt% of FCNTs. Chemical interactions among FCNTs and ENR 25 altered the composite morphology and led to good dispersion, both of which contribute to the excellent thermo‐mechanical and gas barrier properties of the composites. The distribution of the filler inside ENR 25 has been characterized with scanning electron microscopy, which unveiled segregated FCNTs. The obtained experimental gas permeability values were correlated with the well‐known Bharadwaj model. The fabricated functional composites could find applications in automobiles, packaging, and other demanding engineering sectors.

Influence of gas permeability of abrasive tools on their structural and mechanical parameters

Quality assurance and processing capacity are essential performance parameters of abrasive tools. It is of prime importance for grinding wheels operating at a speed of 35–60 m/s. In this case, the opportunities to increase the high-rate grinding efficiency without burns are associated with using high-porosity and low-hardness wheels. Artificial pore-forming agents are used to manufacture tools. Introduction of pore-forming agents decreases grinding forces and increases the maximum grinding depth without burns. The porosity of filled compound materials can be attributed to the conception of gas permeability. The gas permeability parameter describes the openness degree of such structures and the velocity of the air volumes passing through porous materials. The porosity and gas-permeability degrees of the material of high-porous ceramic-bond abrasive tools with various parameters, depending on the abrasive material type, porogen grain size and content, and the composite structure number have been studied. It appeared that the porosity degree of high-porous abrasive tools, made both of fused alumina and silicon carbide increases as the structure number, grain size, and content of burning porogens increases. Besides, the increase degree of fused alumina is a little higher than that of silicon carbide. The gas permeability degree depends on the factors mentioned above in nearly the same way. Compared to porosity, the effect of gas permeability increases due to an altered structure, grain size, and content of porogens is much higher, up to 6 times. In this case, the gas permeability value is primarily characteristic of the pore size; in other words, the speed and volume of the air or lubrication and cooling fluid penetrating the material structure increase correspondingly at nearly the same increase of the pore size by several times and at the same volume porosity degree. The gas permeability degree can be used for quantitative and qualitative description of the material structure of high-porous abrasive tools, as well as their structural and mechanical parameters. The operating parameters of tools can depend on the gas permeability level of their materials. Thus, the results of abrasive processing can be foreseen.

Freeze cast support for hydrogen separation membrane

BaCe0.65Zr0.20Y0.15O3-δ - Gd0.2Ce0.8O2-δ (BCZY-GDC) membranes have received increasing attention for their full H2 selectivity, high thermal and chemical stability, and intrinsic lower cost respect the Pd–based technology. The microstructure of the substrate plays a fundamental role to increase the gas diffusivity through the porous support. In this work, BCZY-GDC ceramics for hydrogen separation application were produced for the first time using ice-templating technique to obtain membrane supports with well-organized aligned porosity and lower pore tortuosity. After slurry composition optimization, the effect of cooling rate on the microstructure was accurately investigated. Samples produced with cooling speed of 30 °C/h showed homogeneous microstructures and well-aligned porosity with the best compromise between gas permeability and mechanical properties. Particularly gas permeability values are one order of magnitude higher with respect to the ones registered for tape cast BCZY-GDC substrates with isotropic porosity conventionally used for protonic applications.

Polyazole polymers membranes for high pressure gas separation technology

Aromatic (fluorinated and non-fluorinated) polyoxadiazole and polytriazole polymers were synthesized through one step polycondensation method in the lab followed by gas permeation and purification performance of the membranes prepared by casting their polymer solution from chloroform or NMP solvents. The gas permeability and selectivity values were found mainly depending on the bulky fluorinated groups (hexafluoroisopropylidene, HFA) on the main polymer stem and a bulky aniline derivatives (4-bromoaniline & 4-aminophenol) groups as a side chain of the polymer stem. No plasticization effect was observed for the membranes under a high range of pure CO2 feed pressure (100–800 psi). The polymers synthesis process is simple and reproducible, easy solubility in most of the common organic solvents and easily scalable for commercial production. The polymer membrane materials developed in this research work, showed a considerable high permeability for CO2 and helium gases and a very low or negligible permeability for other gases such as methane (CH4), nitrogen (N2) and ethane (C2H6) at a very high operating feed pressure (up to 800 psi). Based on the preliminary results, these polymers membranes can be considered as promising materials for gas separation technology especially for helium recovery and CO2 gas removal with a high selectivity. This work represents the testing of dense membranes under different experimental conditions of feed pressure (up to 800 PSI) at room temperature to investigate their mechanical and chemical stability for potential industrial application.