Inner Surface Of Pores Research Articles

Functionalization of the Surface of Porous Nickel–Titanium Alloy with Macrocyclic Compounds

For the first time, we performed functionalization of the surface of porous titanium nickelide alloys with bambusuril[6]-based macrocyclic compounds by different methods in order to provide the basis for saturation with therapeutic agents to impart antibacterial activity and accelerate its osteogenesis. It has been shown for the first time that the vacuum modification method is preferable for bambusuril deposition, since it provides a uniform deposition of organic matter on both the outer and inner surfaces of the pores. The effect of bambusuril deposition methods on the continuity, structure, and cytocompatibility of the porous titanium nickelide surface was evaluated. In vitro tests proved high biocompatibility and low toxicity of porous TiNi treated with BU[6] under vacuum. The SEM study of the structure of the surface layer of TiNi modified with BU[6] under the vacuum method showed that BU[6] agglomerates are uniformly deposited on the inner and outer surfaces of TiNi pores, which will provide an even saturation of BU[6] cavities with various pharmaceuticals, including antibiotics and inhibitors.

Synthesis of industrial solid wastes based geopolymer foams for building energy conservation: Effects of metallic aluminium and reclaimed materials

Thermal insulation materials with less energy consumption and low CO2 emissions have been paid great attention. This study was devoted to assessing the feasibility of utilizing industrial solid wastes for the preparation of sustainable geopolymer foams to make up for the weak link of using industrial solid waste in green low-carbon building energy-saving materials research. Efforts were made to investigate the effects of aluminium powder content and substitution ratio of reclaimed materials on slurry performance, physic-mechanical properties and formation of gel species by a series of characterization methods. Results revealed that the geopolymer foams characterized by compressive strength of 2.83 MPa, bulk density of 507 kg/m3 and thermal conductivity of 0.167 W/(m·K) were successfully produced by external incorporation of 0.17 % dosage of Al powder. 10 % substitution ratio of reclaimed materials presented no obvious negative effect on fluidity, initial setting time, bulk density, compressive strength, thermal conductivity, pore structure and microstructure of the specimens. The pore structure, morphology and polymeric gels of pore partition matrix co-determined the macroscopic properties of geopolymer foams. The existence of semi-crystalline zeolite precursors in reclaimed materials may induce the formation of zeolite-like grains on the inner surface of pores. The present work was in agreement with the strategic objective of resources recycling, solid waste utilization, lower carbon emission and building energy saving, which was conducive to the development of the circular and green economy.

Post-Operational Characterization of a Long-Term Operated Solid Oxide Fuel Cell Stack

A two layer solid oxide cell stack based on anode-supported cells was operated galvanostatically at 0.5 A / cm² and 700°C for nearly 100,000 h in fuel cell mode. The overall degradation rate during the operation was approx. 0.5 %1000 h but the stack shows different degradation rates over different time periods. In contrast to our typical stack material choice this stack was mainly assembled with another type of metal: ITM from Plansee SE, Austria instead of Crofer22APU. Crofer 22 APU was merely used for a 200 µm thick foils inserted in the manifold areas at the gas in- and outlet of the cells. After controlled shut-down, the stack was post-test analyzed. After leakage test by pressure drop method, part of the stack was embedded as a whole and part was dissected plane-by-plane. All stack components, the cell, the metallic interconnects, frames and the glass-ceramic sealing were afterwards characterized by means of SEM, TEM and wet chemical analysis. Some analysis were made on whole stack parts including the top and bottom plates and some were performed on dissected individual parts.In summary, most of the components look optically quite good despite the 11 years operation. The measured gas-tightness at room temperature was below the threshold of 1 % gas loss on the fuel side but in an acceptable range regarding the air side. The microstructure of the glass-ceramic sealant showed a high crystallization state of the material with moderate porosity. The triple phase boundary to the furnace atmosphere had a thin layer of barium chromate indicating an early crystallization equilibrium achieved after short terms not being effected by the long-term exposition afterwards. An antiquated application method was used for the sealant resulting in an infiltration of the protective layer up to 100µm depth by the excess glass-ceramic squeezing out of the joining gap. Regarding the interfacial reactions to the YSZ electrolyte, zirconium containing silicate needles are formed as a thin layer. The reaction zone to the steel ITM is very similar to the phenomena observed for Crofer22APU: a chromium manganese spinel layer is dissolved by the glass during joining process resulting in an interfacial layer of 1-2 µm thickness.The interconnect steel ITM formed a thin protective chromia surface scale. The relatively high contents of chromium (ca. 25%) and molybdenum (ca. 3%) in the steel resulted in extensive s-phase formation in the large areas of the interconnect. Gas distributing steel foils of 200 µm thickness made from Crofer 22 APU showed only in some locations nodules of Fe-rich oxide. Substantial parts of these foils formed a protective surface oxide scale consisting of an outer Mn, Cr- spinel layer on top of an inner chromia scale. Interdiffusion phenomena were observed at the spot-welded joints between nickel contact wires and steel components. Ni diffusion from the wire into the ITM interconnect and Crofer 22 APU foils resulted in local transformation of ferritic into austenite structure. On the other hand diffusion of Cr from the interconnect into the Ni-wires resulted in minor Cr-oxide formation on the surfaces of the Ni wires.The cell itself and the air-side contacting reveal no obvious macroscopic changes like delamination, cracking etc. A closer look into the cell shows the formation of an interface zone between the LSCF cathode and the GDC barrier layer. This zone looks fragmented and being composed of various tiny crystals which in turn can be traced back to LSCF and GDC. But in many areas additionally Cr as foreign element could be detected. This Cr is also present in the first micrometers of the GDC barrier layer forming also tiny crystals on the inner surface of pores within the GDC. In the fuel electrode, composed of Ni and 8YSZ, also very small foreign phases containing Mn and Al were found. The amount is very low as the ITM contains only traces of Mn. But an enrichment in Ni in the fuel electrode could be detected. This is opposite to the effect in electrolysis mode were a Ni depletion takes place.To sum up the cell-related findings: i) an enrichment in Nickel in the fuel electrode has been observed in this stack for the first time; ii) a foreign phase composed of Mn-Al-(O) is present in the fuel electrode; iii) the LSCF cathode is, closed to the barrier layer, fragmented and chemically disintegrated; iv) the GDC barrier is also fragmented at the border towards the cathode and lastly v) an interaction between Cr and GDC has been observed also for the first time.

Interaction of elements in carbon-graphite—Al—Mg—Zn—Cu melt system under combined action of temperature and pressure

Redistribution of chemically active elements is established on its inner surface of pores and at the interface with the alloy when impregnating carbon-graphite framework with Al—Mg—Zn—Cu alloy at temperature of 800 °C under pressure of up to 3 MPa. In this case, change in the solubility of melt elements in aluminum is possible as result of the combined action of temperature and pressure in the impregnation process, created due to the difference in the coefficients of thermal and thermal expansion of the matrix alloy, and the material of the impregnation device during impregnation. Titanium compounds are found in the pores filled with metal that are not added to the matrix alloy, but are formed as result of the contact of the matrix alloy melt with the walls of the impregnation device.

Porous Materials in Heat Exchangers Used in Heating

This paper proposes using porous metals to boost heat exchanger efficiency. One coolant (Freon) flows through the porous metal, while the other coolant (water) flows through the narrow tubes laid inside the porous metal. The paper presents a mathematical model for a porous-metal heat exchanger, which can find metal temperature changes in any section of the heat exchanger to compare the heat transfer rate of metals of different porosity. Calculation by standard methods is not an option, as the inner surface of pores is unknown. The temperature of hot water inside the heat exchanger is to be found analytically. The obtained equations help determine the degree of cooling the first coolant (hot water). Porous heat exchangers can be used in heating systems.

Conception of Nanosized Membrane Reactors for Hydrogenation with Accumulated Hydrogen

Results are summarized from studies to develop the concept of next-generation nanosized membrane reactors (NMRs) in which hydrogenation reactions are run in pores of varying diameter using hydrogen preadsorbed in mono- and multilayer oriented carbon nanotubes with graphene walls (OCNTGs) formed on the inner surface of pores of ceramic membranes. A comparative analysis is performed of the morphology of such carbon nanostructures as graphenes, OCNTGs, and pyrocarbon nanocrystallites (PNCs), and morphology is studied via X-ray diffraction analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). It is shown that only OCNTGs are capable of accumulating and storing hydrogen. The mechanism of hydrogen adsorption and the laws governing adsorption in this nanostructure are discussed. Results from the noncatalytic hydrogenation of decene-1 and naphthalene in NMRs with hydrogen adsorbed in OCNTGs are analyzed, and the kinetics and activation energies for these reactions are determined. The effect of the substrate on which graphene nanostructures are synthesized is estimated through a comparative analysis of the mechanisms of hydrogen adsorption in OCNTGs and cylindrical and planar graphene nanostructures (CPGNSes) formed on zeolites. The concept of NRMs is formulated, the directions of developing the concept are discussed. These include devising ways to create of catalytically active metal-containing sites in the NMR structure and the effect of the steric factor of the nanoreactor configuration on the selective hydrogenation of different organic substrates.

Peculiarities of the Gas Breakdown in Narrow Discharge Gaps at High Pressures

Plasma treatment of porous polymer materials is a promising method for creating new materials that can be widely applied, in particular, in medicine and for development of new types of biocompatible and biodegradable polymer materials. In this work, plasma treatment of porous polymer materials is studied to reveal the breakdown conditions and to optimize this method of treatment. Experiments have been performed to determine the breakdown voltage in the discharge gap of a pulse barrier discharge at different air pressures and different gaps in the region of the minimum of the Paschen curve. An approximation of the Paschen curve with the variable γ is proposed, which provides good agreement with the experimental results. A technique of barrier discharge treatment of the inner surface of pores in a dielectric material based on optimizing the pressure inside the pores is proposed. The treatment of few-micron pores requires pressures substantially above atmospheric. The first results demonstrating the possibility of modifying the bulk of the polymer material by means of the barrier discharge treatment at the time when the gas pressure in the discharge chamber drops are obtained.

Dynamics of Acoustic Waves in a Porous Medium Partially Saturated with a Gas Hydrate

The propagation of acoustic waves in a porous medium partially filled with a gas hydrate was investigated with regard for the viscoelastic properties of the skeleton of this medium on the assumption that the gas hydrate is distributed homogeneously in the thin layer at the inner surface of pores of the medium. A system of equations defining the propagation of acoustic waves in a porous medium containing a gas hydrate is proposed. A dispersion relation has been derived for investigating the influence of different parameters of a porous medium on the propagation of acoustic waves in it.

Specific features of formation of bulk porous systems in the self-propagating high-temperature synthesis. Borides

The effect of ultrasound oscillations (USO) on the combustion velocity and temperature, phase composition and microstructure of compounds produced by the self-propagating high-temperature synthesis (SHS) in the Ti–B system is studied using the earlier developed experimental setup. It is shown that the effect of powerful ultrasound on SHS is connected with the thermal factor, viz. the enhancement of heat removal from the specimen surface due to forced convection, and the physical (non-thermal) factor that consists in the influence of USO on the melt spreading and crystallization of different phases in the SHS wave. It is demonstrated that for multiphase system Ti–B an increase of the boron content in the initial charge leads to grain refinement of the synthesized product and the imposition of USO on the SHS results in a change in the grain morphology: their shape becomes closer to equiaxial. In composition Ti+1.5B, under the action of USO cubic-shape product grains are observed on the inner surface of pores, and in composition Ti+2.0B the synthesized TiB2 grains become more vividly facetted.As a result of imposition of ultrasound on the synthesis process, grain refinement is observed for all the compositions along with the formation of a large number of borides and their redistribution in the volume. The use of ultrasound brings about changes in the quantitative phase composition of the synthesis products and the ratio between the orthorhombic and cubic modifications of phase TiB. The research has shown that the presence of pores in the initial charge plays an important role in the structure formation of the final product, and hence it appears impossible to obtain an equilibrium material by the SHS method. It is found that an optimal USO amplitude exists at which it is possible to obtain uniform fine-grained structure of the material. This permits controlling the structure formation at SHS.

Surface energy reduction by dissociative hydrogen adsorption on inner surface of pore in aluminum

Surface energy reduction by dissociative hydrogen adsorption on inner surface of pore in aluminum

Probing Gas Adsorption in Metal–Organic Framework ZIF-8 by EPR of Embedded Nitroxides

Metal–organic frameworks (MOFs) are being increasingly considered as promising materials for gas separation and storage, yet specific interactions between gas molecules and the inner surface of pores are still not well understood. In this work, we propose a new approach for investigation of such interactions by Electron Paramagnetic Resonance (EPR). We use stable nitroxide radicals as multifunctional agents embedded into the pores of a MOF prior to the gas sorption. They act as EPR-active reporters, and simultaneously as competitor molecules during the gas adsorption process. We exemplify this approach using a ZIF-8 framework, nitroxide TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl), and CO2, N2, and O2 gases. The mobility of nitroxide monitored by continuous wave EPR behaves differently upon adsorption of each of these gases. In particular, a noticeable increase of mobility in the presence of CO2 reveals the weakening of guest–host interactions TEMPO–MOF induced by CO2, which was qualitatively supported by molecular dynamic calculations. The nitroxides can be embedded in MOFs postsynthetically, and their negligible amounts (≤1 per 1000 cells) are required due to a high sensitivity of EPR. Therefore, the proposed approach is sufficiently versatile and might find broad applications for various MOFs.

The importance of nano-porosity in the stalk-derived biochar to the sorption of 17β-estradiol and retention of it in the greenhouse soil.

Natural estrogens in greenhouse soils with long-term manure application are becoming a potential threat to adjacent aquatic environment. Porous stalk biochar as a cost-effective adsorbent of estrogen has a strong potential to reduce their transportation from soil to waters. But the dominant adsorption mechanism of estrogen to stalk biochars and retention of estrogen by greenhouse soils amended with biochar are less well known. Element, function groups, total surface area (SAtotal), nano-pores of stalk biochars, and chemical structure of 17β-estradiol (E2, length 1.20nm, width 0.56nm, thickness 0.48nm) are integrated in research on E2 sorption behavior in three stalk-derived biochars produced from wheat straw (WS), rice straw (RS), and corn straw (CS), and greenhouse soils amended with optimal biochar. The three biochars had comparable H/C and (O + N)/C, while their aromatic carbon contents and total surface areas (SAtotal) both varied as CS > WS > RS. However, WS had the highest sorption capacity (logK oc), sorption affinity (K f ), and strongest nonlinearity (n). Additionally, the variation of Langmuir maximum adsorption capacity (Q 0) was consistent with the trend for SA1.2-20 (WS > RS > CS) but contrary to the trend for SAtotal and SA<1.2 (CS > WS > RS). These results indicate that pore-filling dominates the sorption of E2 by biochars and exhibits "sieving effect" and length-directionality-specific via H-bonding between -OH groups on the both ends of E2 in the length direction and polar groups on the inner surface of pores. After the addition of wheat straw biochar, the extent of increase in the sorption affinity for E2 in the soil with low OC content was higher than those in the soil with high OC content. Therefore, the effectiveness for the wheat straw biochar mitigating the risk of E2 in greenhouse soil depended on the compositions of soil, especially organic matter.

Structural-textural nature and sorption properties of limestones from the mesozoic-neogene contact zone in the Bełchatów deposit

Abstract Limestones of the Jurassic age are one of the most important minerals accompanying the Bełchatówlignite deposits. They are part of the Bełchatów and Szczerców rock subsoil complex and form natural hillsides of exploitation fields, which are gradually being exposed due to the progressive exploitation of coal. So far in Bełchatów Lignite Mine nearly 2 million tonnes of limestones have been extracted, which were used in the form of highway aggregate. For the extraction (mineral recovery) approx. 2 million tonnes remained in the Bełchatów field and from 20 to nearly 70 million tonnes in the Szczerców field. The limestones occurring in the deposit Bełchatów are differential qualitatively. Those situated in direct contact with Neogene deposits are characterized by strong karstification (karst formation), and even occur in the form of detrital minerals. Furthermore, they are covered by processes of secondary mineralization. These processes caused significant diversity of phase and chemical composition, and thereby have contributed to reducing the CaCO3 content. Despite this, limestones from the Mesozoic-Neogene contact zone possess excellent sorption properties in respect of SO2 in conditions of fluidised furnaces. These properties are determined firstly by their structural-textural nature, and above all with the presence of calcite sparite crystals in microcrystalline groundmass, of micropores, tectonic discontinuities, fracturings and compaction slits. With their presence, both decarbonatization and sorption processes proceed effectively. The CO2 particles are quickly removed from the structures of calcite crystals, and SO2 is able to penetrate into the interior of the sorbent grains where are absorbed on the inner surface of pores arising as a result of the decarbonatization process. These characteristic structural and textural properties of the surveyed limestones have been shaped at the diagenesis and epigenesis stage. This contributed to all chemical and mechanical compaction and cementation processes, as well as the dissolution and recrystallization processes. Despite the low CaCO3 content limestones from the Mesozoic-Neogene contact zone can be successfully used in the form of sorbents to reduce SO2 emissions in conditions of fluidised furnaces.

Transformation of nanopores in gold under conditions of thermoactivation and the effects of acoustic and shock waves

Structural transformations of nanopores with cylindrical shapes in gold under conditions of thermoactivation and the influence of acoustic and shock waves are studied by means of molecular dynamics. It is shown that at temperatures above 600 K, dislocation loops are generated on the inner surfaces of pores, creating stacking fault tetrahedrons. Exposing a pore to acoustic waves lowers the initial temperature of its collapse. Exposing a cylindrical nanopore to shock waves in the direction perpendicular to its axis can lead to its division into two separate pores.

Depositing and alloying on the inner surface of Gasar Cu pores by plating and annealing treatment

Depositing and alloying on the inner surface of Gasar Cu pores were realized by plating Zn and subsequent annealing treatment. Influences of cathode current and plating time on alloy layer thickness at different positions along the pore axial direction were investigated. The obtained results showed that alloy layers with different thickness were formed on the overall inner surface of pores. Phase constitution of alloy layers was determined by energy dispersive X-ray analysis and the phase diagram of Cu–Zn. It was found that the generating sequence of alloy phases was γ→β′→α. Based on the thickness of each phase measured from field emission scanning electron microscopy images, the relationship between phase thickness and annealing time was obtained.

Peculiarities of Gas Transfer in Track Membranes with Asymmetric Pores

The asymmetry of the transport (permeation) of gases through track membranes with asymmetric pores has been experimentally investigated. Samples with different porosities and diameters of pores have been studied. The difference between the direct and reverse flows (asymmetry of transport) of helium, nitrogen, and carbon dioxide through membranes has been revealed. The flow from the narrow part of a pore (direct flow) is about 15% larger than the reverse flow. The interaction parameters characterizing the effect of the roughness of the inner surface of pores on the gas flow through a membrane have been determined. The surface flow effect has been demonstrated using the data obtained. Necessary conditions for the appearance of the asymmetric transport effect have been formulated.

Inner surface alloying on pores of lotus-type porous copper through electroless plating with supersonic vibration and annealing treatment

A new method was explored for inner surface alloying on pores of lotus-type porous copper. Zinc was deposited on the inner surface of pores by electroless plating with thorough supersonic vibration. Then, the Cu substrate together with Zn coatings was transformed into a brass layer by annealing treatment. From images filmed by a digital single lens reflex camera and a field emission scanning electron microscopy, it can be observed that the appearance and microstructure of lotus-type porous copper surface and pore walls were changed after the sequential treatments. The statistical thickness of the alloy layer at the distance of 0.5mm from pore openings increased with the electroless plating time increase, attaining a maximum of about 1.7μm when the time exceeded 1.5h. The alloy layer thickness at the sample height of 2.5mm along the pore axial direction was determined as about 1.5μm by the nano-indentation technique. Uniform coating and alloy layer can be achieved on the inner surface of 5mm-long pores. The influence of annealing temperatures on phase compositions was studied by X-ray diffraction.

Magnetic Study of Nanostructural Composite Material Based on Cobalt Compounds and Porous Silicon

In present work, an investigation of a magnetically ordered material, which is a composite structure obtained by embedding of cobalt-containing substance into pores of silicon matrix, was performed. The samples were characterized by steady-state magnetometry and electron microscopy. The methods of longitudinal nonlinear response to a weak ac magnetic field and registration of electron magnetic resonance were used for detail study of their properties. It was established that the material forms a structure of ferromagnetic particles at the inner surface of pores. It was agued that they are mainly nonmetallic magnetic particles like Co2B and/or Co3B. The possibility to apply the concept of blocking temperature to specify the magnetic behavior of the compound on temperature confirmed the single-domain state of these particles.

Growth of a Carbon Nanotube Forest on Silicon using Remote Plasma CVD

CVD enhanced by remote plasma is applied to produce carbon film material on silicon substrates. The layers of aligned multiwall carbon nanotubes (MWCNT) are obtained without a metal catalyst by deposition from a methane/hydrogen gas mixture activated by a direct current (DC) discharge. The individual MWCNTs in the films consist of 4–7 concentric carbon shells with a spacing of 0.34 nm. An absence of metallic impurities in the MWCNT film material is confirmed using energy dispersive X‐ray (EDX) and electron energy loss spectroscopy (EELS) analyses. A proposed model explains the formation of the cylindrical seeds of the MWCNTs via condensation of carbon atoms from the activated gaseous environment on the inner surfaces of pores, created in the substrate material as a result of silicon etching by ionized hydrogen, generated in the DC discharge plasma. Further growth of these seeds during the CVD process leads to the formation of MWCNT forests.

Measurement of gas storage processes in shale and of the molecular diffusion coefficient in kerogen

Total gas storage capacity in many shale gas reservoirs arises from three sources: compressed gas in the micro- and nano-scale pores, adsorbed gas on the inner surfaces of pores in kerogen—the main constituent of organic materials in shale—and dissolved gas molecules in kerogen. The storage capacity of and transport processes for each of these three sources of gas are different, and accordingly, appropriate models and production strategies should be developed on the basis of actual physics. Of great relevance to field development and management is knowing the contribution of each source to daily production and ultimate gas recovery. A valuable body of literature has addressed the first two sources, but the last source has not been studied in detail. We developed a technique to measure the gas capacity from each of the above-mentioned three sources simultaneously, in a small piece of a shale sample, through batch pressure decay experiments. Temporal pressure decay is recorded using a quartz high-resolution pressure transducer for several days. The pressure-decline curve shows distinctive slope changes representing different storage processes. Pressure decline at the earliest time represents gas migration into the micro- and nano-pores. This is followed by a change in the slope of the pressure decline in an intermediate time, representing gas adsorption onto the inner surface of kerogen pores. At the later time, the slope of the pressure decline changes again, representing gas diffusion into kerogen. In the samples we tested, we found that dissolved gas in kerogen can contribute about 22% of the total gas-in-place. Assuming that gas molecules diffuse into the walls of the pores in kerogen, we used a Fickian diffusion model and a parameter-estimation technique to estimate the gas molecular diffusion coefficient in kerogen. We measured the diffusion coefficient of methane in amorphous kerogen as being on the order of 10−20m2/s.