Porous Ceramic Surfaces Research Articles

Experimental study on the boiling behavior and film evolution of e-liquid on the surface of porous ceramic in e-cigarette

Electronic nicotine delivery systems (ENDS) have gained popularity worldwide. Research on the boiling behavior of e-liquid in ENDS helps to better understand heat transfer and e-aerosols generation mechanism. This paper designed an experimental system to investigate boiling behavior and liquid film evolution on the porous ceramic surface of ENDS. The effects of puffing duration, heating power and puffing pressure on the variations of temperature on ceramic surface and chamber pressure, boiling behavior of e-liquid were systematically explored. The boiling/vaporization of e-liquid mainly occurred on the e-liquid thin film formed on the ceramic bottom surface, which took ∼3 s to become relatively stable. Three boiling modes, i.e., incipient boiling, bubble boiling and non-bubble boiling have been identified based on the analysis of boiling images, which greatly relied on the heating power and puffing pressure. Increasing puffing pressure mainly caused greater liquid supply to the liquid film with larger thickness accompanied by bubbling mode, while higher heating power intensified liquid–vapor interface instability with higher oscillation frequency and consuming rate of e-liquid, more easily to induce non-bubbling boiling. The results provided insight into the boiling phenomenon and associated mechanisms, being of important significance in optimizing puffing parameters and avoiding failure of ENDS.

New Method toward a Robust Covalently Attached Cross-Linked Nanofiltration Membrane.

As nanofiltration applications increase in diversity, there is a need for new fabrication methods to prepare chemically and thermally stable membranes with high retention performance. In this work, thio-bromo “click” chemistry was adapted for the fabrication of a robust covalently attached and ultrathin nanofiltration membrane. The selective layer was formed on a pre-functionalized porous ceramic surface via a novel, liquid–vapor interfacial polymerization method. Compared to the most common conventional interfacial polymerization procedure, no harmful solvents and a minimal amount of reagents were used. The properties of the membrane selective layer and its free-standing equivalent were characterized by complementary physicochemical analysis. The stability of the thin selective layer was established in water, ethanol, non-polar solvents, and up to 150 °C. The potential as a nanofiltration membrane was confirmed through solvent permeability tests (water, ethanol, hexane, and toluene), PEG-in-water molecular weight cut-off measurements (≈700 g mol–1), and dye retention measurements.

MgO/carbon nanofibers composite coatings on porous ceramic surface for CO2 capture

Ceramic materials modified by hybrid MgO/carbon nanofibers systems are synthesized and characterized. Disordered carbon nanofibers were obtained via catalytic chemical vapor deposition of ethylene over nickel nanoparticles supported on the starting porous ceramic substrate. The carbon nanofibers were functionalized by acid treatment to increase the number of carbonyl and carboxyl groups on their surface. The hybrid samples were prepared by a deep coating method using Mg (OH)2 nanoparticles. After calcination, the obtained hybrid system attained a specific surface area of 242 m2·g−1 and a pore volume of 0.8 cm3·g−1. The hybrid material shows significantly enhanced sorption capacity towards carbon dioxide (4.9 mmol·g−1 CO2 uptake) under 367 K and 1 bar partial pressure of CO2.

Novel perspectives of laser ablation in liquids: the formation of a high-pressure orthorhombic FeS phase and absorption of FeS-derived colloids on a porous surface for solar-light photocatalytic wastewater cleaning.

A pulsed Nd : YAG laser ablation of FeS in water and ethanol produces FeS-derived colloidal nanoparticles that absorb onto immersed porous ceramic substrates and create solar-light photocatalytic surfaces. The stability, size distribution and zeta potential of the nanoparticles were assessed by dynamic light scattering. Raman, UV-Vis and XP spectroscopy and electron microscopy reveal that the sol nanoparticles have their outmost layer composed of ferrous and ferric sulphates and those produced in water are made of high-pressure orthorhombic FeS, cubic magnetite Fe3O4 and tetragonal maghemite γ-Fe2O3, while those formed in ethanol contain hexagonal FeS and cubic magnetite Fe3O4. Both colloids absorb solar light and their adsorption to porous ceramic surfaces creates functionalized ceramic surfaces that induce methylene blue degradation by daylight. The laser induced process thus offers an easy and efficient way for the functionalization of porous surfaces by photocatalytic nanoparticles that avoids aggregation in the liquid phase. The formation of an orthorhombic high-pressure FeS phase stable under ambient conditions is the first example of high-pressure structures produced by laser ablation in liquid without the assistance of an electric field.

Fingerprints of Epoxy Bleed-out on Porous Ceramic Surface

Fingerprints of Epoxy Bleed-out on Porous Ceramic Surface

The preparation, microstructure and mechanical properties of a dense MgO-Al2O3-SiO2 based glass-ceramic coating on porous BN/Si2N2O ceramics.

A dense MgO–Al2O3–SiO2 based glass-ceramic coating was prepared by a doctor blade process on a porous BN/Si2N2O ceramic surface followed by heat treatment at 1050 °C under nitrogen flow. The phase composition, microstructure, mechanical properties and water absorption of the coating were studied. The coating consisted of α-cordierite phase with a small amount of glass phase. The dense coating without pores and cracks was favorable to seal and densify the porous ceramic surface due to part of the molten glass infiltrating the surface pores. The coating was defect-free and tightly bonded to the substrate because of a larger bonding area between the coating and the substrate. The elastic modulus and bending strength of the glass-ceramic coating were 37.9 GPa and 67.1 MPa, respectively. Moreover, the coated samples had a high Vickers hardness and low water absorption.

Influence of Voltage on the Biological Performance of Micro-Arc Oxide Films Based on TC4 Titanium Alloy

The porous ceramic biologic films were prepared on the surface of Ti6Al4V (TC4) with micro-arc oxidation technology (MAO). The phase composition, microstructure and valence state of micro-arc oxide films were studied. The biological properties of the ceramic film were comprehensive evaluated through animal experiments. Results show that with increasing of the micro-arc oxidation voltage, the better biocompatible hydroxyapatite appears on the surface of titanium alloy (TC4). The high voltage promotes the surface pore size enlarge. The porous ceramic surface makes bone tissue early grow up. Pathological sections of bone tissue 24 w animal experiments indicates that the implants can form good biological combination with bone, no rejection and the higher the micro-arc oxidation voltage, the more new bone cells.

Experimental study of second-mode instability growth and breakdown in a hypersonic boundary layer using high-speed schlieren visualization

Visualization experiments are performed to investigate the development of instability waves within the boundary layer on a slender cone under high Mach number conditions. The experimental facility is a reflected-shock wind tunnel, allowing both low (Mach-8 flight equivalent) and high-enthalpy conditions to be simulated. Second-mode instability waves are visualized using a high-speed schlieren set-up, with pulse bursting of the light source allowing the propagation speed of the wavepackets to be unambiguously resolved. This, in combination with wavelength information derived from the images, enables the calculation of the disturbance frequencies. At the lower-enthalpy conditions, we concentrate on the late laminar and transitional regions of the flow. General characteristics are revealed through time-resolved and ensemble-averaged spectra on both smooth and porous ceramic surfaces of the cone. Analysis of the development of individual wavepackets is then performed. It is found that the wavepacket structures evolve from a ‘rope-like’ appearance to become more interwoven as the disturbance nears breakdown. The wall-normal disturbance distributions of both the fundamental and first harmonic, which initially have local maxima at the wall and near $y/{\it\delta}=0.7$–0.75, exhibit an increase in signal energy close to the boundary-layer edge during this evolution. The structure angle of the disturbances also undergoes subtle changes as the wavepacket develops prior to breakdown. Experiments are also performed at high-enthalpy ($h_{0}\approx 12~\text{MJ}~\text{kg}^{-1}$) conditions in the laminar regime, and the visualization technique is shown to be capable of resolving wavepacket propagation speeds and frequencies at such conditions. The visualizations reveal a somewhat different wall-normal distribution to the low-enthalpy case, with the disturbance energy concentrated much more towards the wall. This is attributed to the highly cooled nature of the wall at high enthalpy.

Bacterial flagellar motility on hydrated rough surfaces controlled by aqueous film thickness and connectedness.

Recent studies have shown that rates of bacterial dispersion in soils are controlled by hydration conditions that define size and connectivity of the retained aqueous phase. Despite the ecological implications of such constraints, microscale observations of this phenomenon remain scarce. Here, we quantified aqueous film characteristics and bacterial flagellated motility in response to systematic variations in microhydrological conditions on porous ceramic surfaces that mimic unsaturated soils. We directly measured aqueous film thickness and documented its microscale heterogeneity. Flagellar motility was controlled by surface hydration conditions, as cell velocity decreased and dispersion practically ceased at water potentials exceeding –2 kPa (resulting in thinner and disconnected liquid films). The fragmentation of aquatic habitats was delineated indirectly through bacterial dispersal distances within connected aqueous clusters. We documented bacterial dispersal radii ranging from 100 to 10 μm as the water potential varied from 0 to –7 kPa, respectively. The observed decrease of flagellated velocity and dispersal ranges at lower matric potentials were in good agreement with mechanistic model predictions. Hydration-restricted habitats thus play significant role in bacterial motility and dispersal, which has potentially important impact on soil microbial ecology and diversity.

Core-shell composite metal catalysts incased into natural ceramic nanotubes

The bimetallic halloysite nanotubes were prepared by the injection of halloysite- containing aerosols into the microwave plasma reactor. Nanotubes contain metal nanoparticles formed from the metal salt solution in the lumen of nanotubes and the iron oxide nanoparticles at the outer surface of nanotubes. Such halloysite composites may be sputtered onto the surface of the porous carrier forming the nanostructured catalyst, as was shown by the pure halloysite sputtering onto the model porous ceramic surface.

Static and dynamic hydrophobicity of alumina-based porous ceramics impregnated with fluorinated oil

Abstract

Adhesion of E. coli to silver- or copper-coated porous clay ceramic surfaces

Porous ceramic water filters (CWFs), produced by sintering a mixture of clay and a combustible material (such as woodchips), are often used in point-of-use water filtration systems that occlude microbes by size exclusion. They are also coated with colloidal silver, which serves as a microbial disinfectant. However, the adhesion of microbes to porous clay surfaces and colloidal silver coated clay surfaces has not been studied. This paper presents the results of atomic force microscopy (AFM) measurements of the adhesion force between Escherichia coli bacteria, colloidal silver, and porous clay-based ceramic surfaces. The adhesion of silver and copper nanoparticles is also studied in control experiments on these alternative disinfectant materials. The adhesive force between the wide range of possible bi-materials was measured using pull-off measurements during force microscopy. These were combined with measurements of AFM tip radii/substrate roughness that were incorporated into adhesion models to obtain the adhesion energies for the pair wise interaction. Of the three antimicrobial metals studied, the colloidal silver had the highest affinity for porous ceramic surface (125 ± 32 nN and ∼0.29 J/m2) while the silver nanoparticles had the highest affinity for E. coli bacteria (133 ± 21 nN and ∼0.39 J/m2). The implications of the results are then discussed for the design of ceramic water filter that can purify water by adsorption and size exclusion.

Performance of porous ceramic evaporators for building cooling application

An experimental investigation of porous ceramic evaporators for building cooling has been carried out. Prototypes, classified as low, medium and high porosity prototypes in direct evaporative cooling mode were placed in an experimental duct within an environmental chamber. Performance was measured under different conditions of dry bulb temperature (DBT), relative humidity (RH), supply water pressure, and layout within the duct. The high porosity ceramic evaporator consistently performed best, while increased water supply head also improved performance. Dry bulb temperature drops of 6–8 K have been achieved parallel with a 30% rise in relative humidity. Maximum cooling of 224 W/m 2 has been measured during test of the high porosity ceramic evaporator placed in a single row stack with water supplied at 1.0 m head. Empirical formulae relating mean cooling performance to [ e s− e], the ambient to saturated vapour pressure difference have been derived. The direct evaporation of water into supply air using porous ceramic surfaces has demonstrated significant potential for building cooling.

Membrane reactor application to hydrogen production

Selective removal of hydrogen in a membrane reactor enables the hydrogen production by steam reforming at lower reaction temperatures than conventional processes. We invented a composite membrane consisting of thin palladium layer deposited on the outer surface of porous ceramics by electroless-plating. The palladium layer could completely cover the surface, so that only hydrogen could permeate through the membrane with a 100% selectivity. By use of this kind of membrane, Tokyo Gas and Mitsubishi Heavy Industries have developed a membrane reformer applicable to the polymer electrolyte fuel cell system. Our current approach is the application of a CVD technique to deposit non-Pd metals, such as Pt, to overcome the limitations caused by Pd membranes, such as hydrogen embrittlement. The permeability and permeation selectivity of these metal-ceramic composite CVD membranes were investigated in a comparison with electroless-plating palladium membranes, as well as the performance in membrane reactors applied to steam reforming of methane. The permeation of hydrogen through the CVD membranes is not based on the solution-diffusion transport mechanism but on the surface diffusion mechanism. Although the CVD membranes gave higher conversion of methane than thermodynamic equilibrium, their performance became similar to electroless-plating membranes, only when the membranes showed high H 2/N 2 separation factors.

Methane Premixed Combustion Behavior of Porous Ceramic Surface Burner in a Furnace.

The surface combustion characteristics of a methane-air mixture on a porous ceramic plate in a cylindrical furnace were studied. The flammability region not only expanded but also the surface temperature of the ceramics rose due to the recirculation effect of thermal radiation from a furnace wall, compared with the case of the open atmosphere. The peak of the surface temperature shifted to a lower equivalence ratio or a higher heat load than that for the open. It is suggested, however, that the structure of the surface combustion in the furnace would be similar to that in the open atmosphere. The influence of input heat loads on the surface temperature was described by a function of the ratio of the net radiant heat loss on the surface to the load. The bottom surface temperature of the ceramics was reduced with increase in the heat load.

Observations of droplet impingement on a ceramic porous surface

The dynamic aspects of droplet impingement on a porous ceramic surface were studied experimentally. Single-shot flash photography was used to photographically record the deformation and spreading on the surface. The observations were made with ambient pressure (0.10 MPa), ambient temperature ( ca. 22° C), initial droplet diameter (1.5 mm), and the impact Weber number (43) fixed. The primary parameter was the surface temperature, which ranged from 22 to 200°C. The liquid was n-heptane. The spreading rate of a droplet on a porous surface at 22°C was measured to be lower than that on a stainless steel surface. No transition to film boiling was observed with the porous surface at a surface temperature of 200°C, unlike that seen with a stainless steel surface. The evolution of wetted area and spreading rate, both of a droplet on a porous surface as well as on a stainless steel surface, were found to be independent of surface temperature during the early period of impact. This result was attributed to negligible surface tension and viscous effects. The maximum value of the diameter of liquid which spreads on the surface was found to be lower on the ceramic surface than it was on the stainless steel surface at the same temperature.

Desalination by the use of dynamically formed PVA membranes

Considering the good rejection characteristic of the phenol contained in aqueous solution and the good chemical resistance (1,2,) proposed that using the dynamic formed method to get symmestric and asymmetric PVA ultrathin membrane on the porous ceramic surface, and the flux of the membrane has risen greatly. The flux keeps more than 5 M 3/D.M 2 and the rejection 90% under the applied pressure 4.0 Kg/cm 2 for 3000 ppm phenol aqueous solution. Besides, the membrane is stabilization for the most organic solvent, high concentration acid and base with high concentration and oxide and salt solution, and have some special selection characteristics. The experiment proved again that the dynamic formed membrane will develop the new field for the membrane research (3). The PVA dynamic formed membrane has a broad prospect both for research and application.