Surface Of Porous Materials Research Articles

Treatment uniformity of atmospheric pressure plasma on flexible and porous material surface: A critical review

<sec>Flexible porous materials play an important role in frontier science and technology fields. Surface modification will further endow the materials with diverse and excellent surface properties, and expand the scope of their applications in functional and intelligent wearable devices. Atmospheric pressure plasma technology has many advantages in treating the flexible materials, such as low temperature, low energy consumption, high efficiency, friendly environment, low cost, no change in material itself characteristics, suitability for roll-to-roll preparation, etc. Also, it presents good adaptability in applied environment and target materials. All these advantages meet the requirements of large area and low-cost surface modification of flexible porous materials.</sec><sec>In this paper, we review several researches of atmospheric pressure plasma surface modification of flexible porous materials used in advanced materials, new energy, environmental protection and biomedicine. The problems and challenges of stability and permeability encountered in uniformly treating the flexible and porous materials by atmospheric pressure plasma are presented. Then, we introduce our research work on atmospheric pressure plasma stable discharge, roll-to-roll coating treatment of permeability and uniformity. Finally, we introduce the breakthrough in and ideas on the deposition kinetics of nanoparticle thin films and their microstructure control by atmospheric pressure plasma. </sec><sec>However, there are still many challenges to be overcome in the applications of the methods in current situation. Basic characteristics, discharge modes of atmospheric pressure plasma and the relationships of plasma discharge to structure and property of the various treated materials need to be further explored. It is confirmed that the permeability and uniformity of the atmospheric pressure plasma treatment in flexible porous materials are very important and their in-depth investigations will promote the application of this method—a high efficient, environmentally-friendly and continuous way of realizing functional and intelligent wearable devices in the future.</sec>

Selective adsorption of acidic gases from ternary mixture by acetate- and sulfonate-based ionic liquids at molecular level.

This paper attempts to elucidate the competitive adsorption mechanism of thin films of ionic liquids (ILs) on the surface of porous materials for acidic gases at a molecular level in order to design a proper material for the diminishment of gas emissions. Thin film 1-butyl-3-methylimidazalium ([BMIM]+) cation-based IL systems composed of four different anions such as [CH3CO2]- and [CF3CO2]- (acetate-based), and [CH3SO3]- and [CF3SO3]- (sulfonate-based) are created in contact with the gas phase containing ternary H2S/CO2/CH4:1/25/74 mixture. To define gas adsorption performance at gas-liquid interface and bulk liquid phase, classical molecular dynamics simulations are carried out. Adsorption of acidic gases is governed by the formation of an adsorbed gas layer on the surface of the ionic liquid based on thermodynamics aspects, and then the partial dissolution of gases in the bulk liquid phase is accompanied by the transport of gases. These behaviors are followed by several analysis methods in simulation approaches such as radial distribution function (RDF) of gases around specific atoms of ILs, lateral displacement of gas molecules, radial distance between gas and ILs, interaction energy between gases and ILs, and average number of hydrogen bonding between ions with and without adsorbed gases. Acetate-based ILs performed twice as good in CO2 adsorption capacity than sulfonate-based ILs. However, the one having -CF3 group in acetate-based ILs has short CO2 retention time and high CH4 adsorption capacity, diminishing the H2S+CO2/CH4 adsorption selectivity. High CO2 adsorption performance of acetate-based ILs is related to their strong anion-cation interaction and less hydrogen-bonding ability between cation tail and anion, which is the source for free space between anion and cation. Those with high adsorption capacities and long retention times are those that can ensure that CO2 molecules are coordinated in these free volumes between cation tails and anions. Therefore, here, the effect of different parameters on the CO2 and H2S adsorption over CH4 is revealed via atomistic design, and the importance of selection of suitable anions in IL for identifying potential nanocomposite adsorbent materials for acidic gas removal is highlighted.

Prediction of plastic yield surface for porous materials by a machine learning approach

The present paper focuses on the prediction of effective plastic yield surface of porous materials having a von Mises type solid matrix. Some typical explicit yield criteria obtained by different analytical homogenization methods are briefly reviewed and evaluated by using numerical results obtained from direct finite element simulations with different values of porosity. Each criterion has its own advantage and weakness. In order to get a better prediction, the Artificial Neuron Network (ANN) algorithm is adopted specially for the prediction of macroscopic yield stress of porous materials, seen as a regression problem with two input parameters and one output value. For the training purpose which is a key step in the ANN approach, new numerical results are presented in the present work with a wide range of porosity and of macroscopic stress triaxiality. Based on these data, the ANN approach is trained and it converges quickly. Then the ANN predictions are compared with numerical test data, a good agreement is found for all loading cases. Comparing with the existing yield criteria, the prediction given by the ANN approach is much more accuracy and easy to apply.

Dynamic wetting behavior of droplets on the surface of porous materials with micro-airflow

<p indent=0mm>The dynamic wetting behavior characteristic of droplets is of significant importance in various industrial applications and high technologies, such as surface self-cleaning, surface drag reduction, anti-frosting, and droplet directional transportation. The modifications of coating surface energy and micro/nano structures on substrate surfaces are the conventional and indirect ways to manipulate the droplet dynamic wetting behavior. At present, many direct and external incentive ways, like substrate vibration, electrowetting and additional magnetic field, also have been proposed to control the droplet dynamic wetting behavior. In the present study, inspired from the phenomenon of droplet floating in the air without gravity, an innovative manipulation method had been proposed, which utilized the additional micro-airflow field as a momentum field to control the force distribution and wetting characteristic of droplets. The core idea of this innovative manipulation method was similar as the Leidenfrost phenomenon, which used the gas buoyancy to counter the droplet gravity effect. A porous substrate sintered by copper particles was used as the experimental sample, a micro-airflow field was located at the down side of porous substrate, and a droplet was wetted on the up side of porous substrate. The magnitude of upright momentum force could be changed by adjusting the pressure of micro-airflow field. Under different pressure of micro-airflow field, the dynamic wetting behaviors of droplets on porous substrate were visualized, and the change regulations of dynamic wetting parameters as a function of wetting time were analyzed. According to the results, three different dynamic wetting modes of droplets on the surface of porous materials with micro-airflow were identified, namely, intact infiltration mode, broken infiltration mode and non-infiltration mode. In the intact infiltration mode and broken infiltration mode, the droplets were finally in the state of complete infiltration, while in the non-infiltration mode, the droplets always maintained the suspension state similar as the super-hydrophobic wetting state. When the droplet was in the intact infiltration mode on the surface of the porous sample, the corresponding dynamic wetting process was simultaneously affected by gravity, surface tension, lifting force, adhesion force and capillary force. In this mode, the apparent contact angle and volume of droplet decreased exponentially at the initial stage during the dynamic wetting process. At the following stage, the decreasing amplitude of two dynamic wetting parameters became slower and presented a linear declining trend. The wetting area at the bottom of droplet rapidly increased to the maximum value at the initial stage, and then decreased slowly. However, when the ratio of droplet height to bottom diameter was less than 0.03, the decreasing amplitude of bottom wetting area increased rapidly, and the droplet would quickly approach to the state of complete infiltration. Besides, the maximum wetting area at the bottom of droplet increased with the increase of pressure difference driven by micro-airflow. The larger the pressure difference was, the smaller the changing range of apparent contact angle and volume of droplet in the same wetting time was, but the longer the whole dynamic wetting period was.

Ti-rich TiO2 Tubular Nanolettuces by Electrochemical Anodization for All-Solid-State High-Rate Supercapacitor Devices.

Supercapacitors store charge by ion adsorption or fast redox reactions on the surface of porous materials. One of the bottlenecks in this field is the development of biocompatible and high-rate supercapacitor devices by scalable fabrication processes. Herein, a Ti-rich anatase TiO2 material that addresses the above-mentioned challenges is reported. Tubular nanolettuces were fabricated by a cost-effective and fast anodization process of Ti foil. They attained a large potential window of 2.5 V in a neutral electrolyte owing to the high activation energy for water splitting of the (1 0 1) facet. Aqueous and all-solid-state devices showed diffusion time constants of 46 and 1700 ms, as well as high maximum energy (power) densities of 0.844 (0.858) and 0.338 μWh cm-2 (0.925 mW cm-2 ), respectively. The all-solid-state device showed ultrahigh stability of 96 % in capacitance retention after 20 000 galvanostatic charge/discharge cycles. These results open an avenue to fabricate biochemically inert supercapacitor devices.

Interfacial water in mesopores and its implications to the surface features – A solid state NMR study

The temperature dependent morphologies of co-existing solid ice and interfacial water within two classic mesoporous materials, MCM-41 and SBA-15, are investigated below the Gibbs-Thomson transition temperature using Cryo-NMR, NMR spin-diffusion and NMR spectral analysis (second moment calculations). By using the combined NMR approach, the difference of the ice cores and interfacial water layers in MCM-41 and SBA-15 is unveiled. Based on the derived thickness of the interfacial water layers, the surface features in the two porous materials are discussed. The work demonstrates an approach to use the combined NMR techniques to study the porous material surface via probing the interfacial water layers, which can be used to study the physical/chemical properties of the material surface on the molecular level in general.

A study on the energy and the reflection angle of the sound reflected by a porous material.

Many noise control applications are based on the use of porous materials; therefore, it is important to have a tool to simulate acoustic behaviours. Plane-wave acoustic properties such as the sound absorption or reflection coefficient at normal incidence can be quickly obtained using standing wave tube or theoretical models and can be used to select the type of porous material and its dimensions. However, in real situations, no plane wave exists, and the sound field is more complex. Therefore, it is interesting to understand the real behaviour of porous materials. In this paper, a simple case of a point source above a uniform infinite layer of porous material has been analysed. Conversely, to the case of a plane wave excitation, on the porous material surface different incidence angles can be observed and the phase relation between the pressure and the particles velocity should be considered. The aim of this work is to define the far and the near field above a porous material where the results obtained considering a plane excitation may or may not be respectively extended. For this purpose, two parameters have been introduced: the energetic deviations index and the true reflection angle.

Characterization of the adsorption site energies and heterogeneous surfaces of porous materials

Heterogeneity of porous structures is an important material property involved during the design of adsorbents, catalysts and molecular recognition materials. This review discusses the mathematical methods that can characterize adsorption site energies and surface heterogeneity from the adsorption isotherms.

Metal-Glass-Ceramic Phases on the Surface of Porous TiNi-Based SHS-Material for Carriers of Cells

Using the methods of SEM, EDS, and optical microscopy, a large number of non-metallic inclusions are revealed on the pore surface of a TiNi-based SHS-alloy. According to the XRD and EDS data, the surface is chemically and structurally inhomogeneous and its composition is close to that of a Ti4Ni2(O,N,C) intermetallic oxycarbonitride. An optical microscopy examination demonstrates that the entire surface is coated with a semi-transparent film. The results of XRD analysis allow assuming that in the formation of the surface of the TiNi-based porous material surface a significant role is played by the glassy phase and wollastonite, which imparts special physical-chemical properties and high biocompatibility to the alloy. SEM examination of morphological features of evolution of the mesenchymal cells on the pore surface of the TiNi-based SHS-material within the period 1–28 days shows that on the 7–14-th day the main elements of loose fibrous connective tissue are formed. Dense connective tissue is formed by the 21-st–28-th day.

Electrophoretic Deposition of Metal Nanoclusters at the Surface of Porous Materials

Coating formation over the surface of a highly porous material on the basis of activated carbon fiber is considered. The coating is applied from a colloidal solution of metals, with the goal of producing electrodes and composite polymer structures. Experiments show that porous carbon materials may be metallized by means of metal nanoclusters (measuring 2–10 nm) on the basis of electrophoresis, without loss of the initial porosity.

The relative performance of microwave regenerated activated carbons on the removal of phenolic pollutants

The adsorption of reagent on the surface of porous material and the regeneration of porous material are significant processes that are widely used in chemical industries. The performance of a granular commercial activated carbon and two activated carbons synthesised from the factory waste tea and demineralised waste tea, were tested during a series of adsorption and regeneration cycles. Phenol and p-nitrophenol (PNP, 4-nitrophenol) were used as the reagents to represent water pollutants. The activated carbon samples were regenerated by the application of a short period of microwave energy (30 s). The influence of the microwave regeneration process on the surface area and pore volumes were investigated with laboratory characterisation techniques. Several cycles of adsorption and regeneration processes were conducted to determine the variation in the adsorption capacity and the characteristics of each porous material. The adsorption and regeneration processes were interpreted in terms of the amount of adsorbed reagent and surface characteristic of the porous material. The materials were found to be good adsorbents for phenol and PNP and the regeneration process worked effectively; broadly maintaining the adsorption capacity over multiple adsorption – regeneration cycles.

Destructive tests of porous materials using Digital Image Correlation Method

Designs of transportation equipment needs not only strength but also weight reduction. Therefore, porous materials are paid attention because they may contribute weight reduction of transportation equipment, machine part and make them high added value. Inside structures of porous materials are vacancy. Porous materials have high performance than conventional product. For example seismic resistance, thermal insulation, shock absorption and so on. But, porous materials have a problem that it is difficult to measure strain by strain gauge because the surfaces of porous materials are particular. So, porous materials need to be measured by contactless method. On the other hand, digital image correlation method is paid attention as deformation analysis method of structure. It can measure strain without touching test pieces. So, the content of this study is to measure material properties of porous materials using digital image correlation method. We could check measuring accuracy of digital image correlation method and measure Young’s modulus of porous materials.

Application of Porous Materials to Carbohydrate Chemistry and Glycoscience.

There is a growing interest in using a range of porous materials to meet research needs in carbohydrate chemistry and glycoscience in general. Among the applications of porous materials reviewed in this chapter, enrichment of glycans from biological samples prior to separation and analysis by mass spectrometry is a major emphasis. Porous materials offer high surface area, adjustable pore sizes, and tunable surface chemistry for interacting with glycans, by boronate affinity, hydrophilic interactions, molecular imprinting, and polar interactions. Among the materials covered in this review are mesoporous silica and related materials, porous graphitic carbon, mesoporous carbon, porous polymers, and nanoporous gold. In some applications, glycans are enzymatically or chemically released from glycoproteins or glycopeptides, and the porous materials have the advantage of size selectivity admitting only the glycans into the pores and excluding proteins. Immobilization of lectins onto porous materials of suitable pore size allows for the use of lectin-carbohydrate interactions in capture or separation of glycoproteins. Porous material surfaces modified with carbohydrates can be used for the selective capture of lectins. Controlled release of therapeutics from porous materials mediated by glycans has been reported, and so has therapeutic targeting using carbohydrate-modified porous particles. Additional applications of porous materials in glycoscience include their use in the supported synthesis of oligosaccharides and in the development of biosensors for glycans.

Errors when assuming locally reacting boundary condition in the estimation of the surface acoustic impedance

Numerical simulations usually require boundary conditions in terms of surface acoustic impedance. The surface acoustic impedance depends on the porous material acoustic properties (e.g., characteristic impedance and wave number) and its thickness as well as the type of wave front impinging on its surface. The locally reactive behaviour hypothesis is often assumed to simplify the choice of proper boundary conditions assigning a constant acoustic impedance value on the porous material surface at a given frequency and for each angle of sound incidence. This hypothesis is also used in measurement procedures or for the estimation of the edge effects.In this paper, it is shown that, in general, a porous material behaves partly as a locally reactive and partly as a non-locally reactive material depending on the ratio between the sound velocities in the free air and in the porous material. By using numerical FEM simulations it is shown that, given a porous material, the acoustic impedance may change or not along the material surface depending on the type of wave front that impinges on its surface.The error when assuming the locally reactive behaviour for porous materials backed by a hard surface and planar incident wave front to compute surface acoustic impedance values has been investigated comparing results yielded by theoretical models available in the literature and the one proposed for non-locally reactive behaviour materials. The last one is validated by means of FEM simulations and experimental results.

Synthesis of vertically aligned composite microcone membrane filter for water/oil separation

A simple and efficient strategy is introduced for fabricating a layer of superhydrophobic and superoleophilic membrane on the surface of porous materials by self-assembly, and it is of great interest for the new type separation of oil and water. It is realized in this study by synthesizing an array of vertically aligned composite microcones on the surface of nickel foam by microwave plasma assisted chemical vapor deposition. The hierarchical structure, high aspect ratio, and dual-scale pine tree-like nature of the microcones formed on the nickel foam, which has microscale pores, in combination with the low surface energy of carbon, amplify both the hydrophobicity and the oleophilicity of the membrane. In addition, the membrane exhibits pH-responsivity, and the controllable water permeation can be realized by simply altering the water pH. Given its extremely high hydrophobicity and oleophilicity as well as outstanding mechanical durability, the composite frame can be used as a filter to separate oil/water mixtures and as an intelligent sponge to purify oil-contaminated water with excellent separation efficiency and absorption capacity. It should also be ideal for real world use in various environmental and chemical separation processes.

A three-dimensional porous metal foam with selective-wettability for oil–water separation

The development of selective-wettability surfaces of porous materials is important for oil spill cleanup. A new type of oil–water separation material has been prepared through a three-dimensional (3-D) extension of a biologically inspired two-dimensional (2-D) material. In this, a simple solution-immersion method is used to construct a super-oleophilic and super-hydrophobic surface on the metallic skeleton of a copper foam, onto which a nanosheet structure is formed that differs greatly from previous nanoscale needle-based materials. This 3-D copper foam is demonstrated to be capable of supporting a maximum height of accumulated water of 5.5 cm prior to oil wetting and 1.5 cm after oil wetting. Furthermore, the foam is capable of efficient oil–water separation, despite losing its super-hydrophobicity during the process. This has given important new insight into the mechanism of separation, in that super-oleophilicity is clearly important to achieving good separation. The selective-wettability of this porous metal foam is expected to extend the range of metal-based oil–water separation materials from 2D metal meshes to more complex 3-D metal structures.

Determination of the constants of cap model for compaction of three metal powders

Cap model is a well-known model for defining the yield surface of porous materials. In this work, the constants of the model are determined by a combined experimental/numerical/optimization technique for aluminum 7075, iron and copper powder. The compaction of powder is conducted using Instron testing machine. The numerical simulation of powder compaction is performed using the Ls-Dyna hydrocode. Optimization is carried out using genetic algorithm. The objective function is defined as the difference between the experimental and numerical load–displacement curves of the compaction. The constants of the model correspond to the case when this difference is optimized. A second order Maclaurin polynomial is assumed for the objective function. The results indicate that the cap model can reasonably predict the powder compaction of iron and aluminum. The model however, proves not to be accurate for copper powder. The results also show dependency of the model’s constants on strain rate.

Formation of Ultra-Thin Pore Seal Layer on Porous Low-k Films

ABSTRACTIn order to integrate porous dielectric materials into the next generation of Cu/low-k interconnect, the porous material has to be sealed against metal barrier precursor. We have reported pore sealants which forms ultra-thin (&lt; 3 nm-thick) layer on top of the surface of porous low-k film while the pore sealant does not diffuse into pores. In this study, it was investigated how pore seal layer is formed on the surface of porous material and how pore mouths are sealed by pore seal layer. It was found that 1) thickness of the pore seal layer is well-controlled in the range &lt; 5 nm, by varying spin rate and concentration of solid, 2) minimal thicknesses of the pore seal layer needed to achieve an efficient sealing for porous low-k films whose pore radius is 1.5 nm was 2.6 nm. 3) Larger pores, whose pore radius is 4.2 nm, were sealed completely with an expansion of our technology.

Effective flow surface of porous materials with two populations of voids under internal pressure: I. A GTN model

This study is devoted to the effective plastic flow surface of a bi-porous material saturated by a fluid. The material under consideration exhibits two populations of voids. The smaller voids are spherical voids whereas the larger ones are spheroidal and randomly oriented inside the material. These two populations of voids are subjected to internal pressures due to the presence of gases. Approximate models for the effective plastic flow surface of such a bi-porous saturated material have previously been proposed in Vincent et al. (2009), where a three-scale homogenization procedure has been performed: first, smearing out all the small spherical bubbles using a Gurson-like matrix, and second, smearing out the intergranular ellipsoidal bubbles. Our objective here is to derive a simple analytical expression of the effective flow surface, starting from one of these previous models, obtained by generalizing the approach of Gologanu et al. (1994) to compressible materials. The main contributions of the present paper are: (1) an expression for the average dilatation-rate in the matrix, (2) an approximation of the effective flow surface in the form of a Gurson–Tvergaard–Needleman criterion. The accuracy of this new model is assessed in a companion paper by comparison with full field numerical simulations.

Effective flow surface of porous materials with two populations of voids under internal pressure: II. Full-field simulations

This study is devoted to the effective plastic flow surface of a bi-porous material saturated by a fluid. Highly irradiated uranium dioxide is a typical example of such a material. In part I of this study, a GTN-type approximation of the effective plastic flow surface has been derived. In this second part, the predictions of this new model are compared with full-field numerical simulations performed with a numerical method based on Fast Fourier Transforms. This method is successfully applied to voided materials with a Gurson matrix where the voids are subjected to internal pressure. Different microstructures containing a large number of spherical or ellipsoidal voids are investigated. The deviation from isotropy of their mechanical response is measured by a new criterion.