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A low-temperature sintered porous SiC-based clay-Ni system with controlled electrical resistivity (2.54 × 1010 Ω cm to 2 Ω cm), and thermal conductivity (3.5 W/m. K to 12.6 W/m. K) was successfully designed. Clay (20 wt% kaolin) was used as a sintering additive in all the compositions. The electrical resistivity, and thermal conductivity was controlled by varying the Ni content (0–25 wt%) in the samples. The electrical resistivity was recorded as low as 2 Ω cm with 25 wt% Ni that was sintered at 1400 °C in argon. The interface reaction between Ni and SiC formed conductive nickel silicide (Ni2Si), while the transformation of kaolin to mullite strengthened the mechanical properties. Submicron-sized Ni (0.3 μm) was more effective than micron-sized Ni (3.5 μm) in reducing the electrical resistivity, and increasing the thermal conductivity along with flexural strength. A comparative study of sintering temperatures showed that 1400 °C resulted in the lowest electrical resistivity (2 Ω cm) and the highest thermal conductivity of 12.6 W/m. K with flexural strength of 54 MPa at 32% porosity in the SiC-kaolin-Ni system.

Electrically conductive porous SiC ceramics are attracting substantial attention due to their application in heatable filters, vacuum chuck, and semiconductor processing parts, etc. The main problem is their high processing cost. Ideal candidates from an engineering ceramic perspective will be mechanically durable and have the required electrical properties with sufficiently low fabrication costs. To decrease the sintering temperature, kaolin has been added, but it tended to render the material an insulator. Graphite was used to effectively decrease the electrical resistivity. Additionally, manganese oxide was used to decrease the quantity of kaolin (the component that leads to an insulator material after sintering) and decrease the electrical resistivity while maintaining the mechanical properties. In our study, we found that SiC with 35% kaolin, 20% graphite and 10% manganese oxide can produce samples with 6.5 × 10−1 Ω cm electrical resistivity and 43.5 MPa flexural strength at a low sintering temperature of 1200 °C.

Reticulated porous ceramics feature a three-dimensional network structure with high porosity and permeability simultaneously. However, generally, the compressive strength capabilities of reticulated porous ceramics are low, which severely limits applications of these materials. To increase the compressive strength of reticulated porous ceramics, it is necessary to coat the strut walls of the polyurethane foam completely with alumina slurry to form a thin ceramic coating layer after optimizing the processing conditions, specifically the alumina slurry composition and the coating condition. Although it remains challenging to improve the compressive strength of reticulated porous ceramics, thus far efforts to do so are underreported. Therefore, in this study, we attempt to optimize the composition (thickener, dispersant, and binder) of the alumina slurry. Among various types of reticulated porous ceramics, we focus on reticulated porous alumina here. Although there are numerous studies regarding porous alumina, which is already widely used, investigations of reticulated porous alumina are rare. In this study, we determined the optimized processing conditions to improve the compressive strength of reticulated porous alumina. These conditions, specifically the composition of the alumina slurry and the pore density of the polyurethane foam, are discussed.

To develop electrospun ceramic nanofibers as water/air filtration media, it is important to control the fiber diameter. This is because the fiber diameter of the electrospun ceramic nanofibers determines the mean/largest pore sizes, and this governs the permeability and filtration efficiency. Herein, the content (or concentration) of ceramic precursors and polymeric binders was adjusted in the electrospinning solution to control the fiber diameter of electrospun yttria-stabilized zirconia (YSZ)/silica nanofiber. This can influence the viscosity of the electrospinning solution and directly affect the fiber diameter of the electrospun YSZ/silica nanofibers through the electrospinning process. Increasing the content of ceramic precursors sequentially confirmed that the fiber diameter of electrospun YSZ/silica nanofibers increases gradually. Conversely, adjusting the content of the polymeric binder could shift the overall distribution of the fiber diameters. In other words, it is more effective to reduce the content of polymer binder than to reduce the content of ceramic precursors to manufacture smaller fiber diameters. The polymer binder content plays a significant role in promoting the mean/largest pore sizes and filtration efficiency. The aim of this research was to develop the electrospun nanofibrous microfiltration (MF) membranes or high-efficiency particulate air (HEPA) filters for water/air remediation. To confirm this hypothesis, the associated characterizations were conducted to evidence the superior filtration performances. For example, a rejection rate (%) of 99.5% (0.5 μm polymeric particles) and a filtration efficiency of 99.9% (0.06 μm NaCl particles) were obtained to prove water and air filtration capacity, respectively.

Oxidation bonding is a technique used to produce porous SiC ceramics at low temperatures. The oxidation behavior of SiC particles depends on various factors, including the oxidation environment, temperature, time, particle size, and impurities. The key properties required for a porous ceramic membrane are a controlled pore morphology, high strength, and high permeability. In this study, SiC powders with different particle sizes (0.55 and 7 μm) were used to fabricate porous ceramic membranes. First, the oxidation behavior of the SiC powders was evaluated. Then, the feasibility of using their mixture to create supports for microfiltration applications was analyzed. Through this study, not only were the ideal conditions for fabricating microfiltration supports quantified but also the conditions where specimens could be made with zero size change. Finally, a membrane fabricated from a powder mixture composed of 92% of the 7 μm powder and 8% of the 0.55 μm powder and sintered at 1450°C was proposed, which had a 37% porosity, 1.42 μm pore size, 49.6 MPa flexural strength, and L cm-2 min-1 bar-1 air permeability.

The development of flexible ceramic nanofibers has attracted much attention because they may be able to overcome the intrinsic brittleness of ceramics and thus be applied towards air/water filtration media. Yttria-stabilized zirconia/silica (YSZ/silica) nanofibers with excellent flexibility could be prepared through (1) sol-gel, (2) electrospinning, and (3) calcination processes. Our research focused on the effect of ceramic precursor concentrations [tetraethyl orthosilicate (TEOS) and zirconium (IV) propoxide (ZrP)] on improving the flexibility of YSZ/silica nanofibers. By adjusting the TEOS and ZrP concentrations, two major parameters (grain size and fiber diameter, respectively) can be controlled. It was consequently revealed that smaller grain size and larger fiber diameter could increase the flexibility of YSZ/silica nanofibers. In addition, flexible YSZ/silica nanofibers successfully performed as microfiltration (MF) membranes, while exhibiting high pure water permeability and a high rejection rate (%) for polymeric nanoparticles.

Porous alumina was fabricated using different particle size, sintering temperature, and particle size and content of poly (methyl-methacrylate) (PMMA) as pore former. The Forchheimer equation was used to investigate the relationship between porosity and average pore size, and obtain the permeability constants k1 and k2 (the viscous effect and the inertial effect, respectively). Compared to Darcy's law, the Forchheimer equation established a more realistic and reliable relationship between fluid pressure and fluid velocity. k1 and k2 were found to be more sensitive to the average pore size than to the porosity of alumina. Moreover, reliable relationships were confirmed between the average pore size and k1, k2, and their ratio (k1/k2).

Inorganic surface modification was carried out using a TiO2/SiO2 sol–gel process to enhance photocatalytic activity and to mitigate fouling of alumina microfiltration membranes. Pristine alumina membranes were subjected to TiO2/SiO2 coating with varied TiO2 mole percentages. Upon the formation of the TiO2/SiO2 layer, small changes in the surface morphology, pore size, and specific surface area were detected. Particularly, as the pore size decreased with the decrease in TiO2 content, the pure water permeability also gradually diminished. By examining the binary TiO2/SiO2 compositions, the optimized conditions demonstrating both higher flux performance and greater photocatalytic activity were determined. Thus, the inorganic surface modification by TiO2/SiO2 coating could contribute significantly to the realization of self-cleaning ceramic membranes while extending the membrane cleaning cycle and accelerating productivity.

The porous SiC-based membrane has proved its validity in microfiltration membrane fabrication, but application is limited due to its high fabrication cost. In this study, the oxidation-bonding technique was used to fabricate a SiC microfiltration membrane. The oxidation behaviour exhibited during different thermal treatments was related to pore morphology, and ultimately membrane permeance. Corrosion properties of the oxidation-bonded SiC specimens were also studied. We have found that a membrane made by coating an oxidation-bonded SiC layer over a clay-bonded SiC support and sintered at 1000 °C for 3 h could make a defect-free, corrosion resistant microfiltration membrane with pure water membrane permeance above 700 LMH per bar over the 1 h operation time. The membrane has a narrow pore size distribution, with an average pore size of 78 nm.

Porous SiC is a proven viable material for microfiltration membranes, but its application has been limited by high fabrication cost. In this study, the oxidation bonding technique was used for the first time to fabricate SiC microfiltration membrane. The study was divided into two parts: optimization of the slurry used to dip coat the SiC particles over a porous SiC ceramic support and controlling the oxidation behaviour of SiC with respect to temperature. The oxidation behaviour during different thermal treatments was related to pore morphology and ultimately the membrane permeance. By coating the clay-bonded SiC support with oxidation-bonded SiC and sintering the coating at 1100 °C for 1 h, we prepared a defect-free microfiltration membrane with pure-water membrane permeance of >210 L m−2 h−1 bar−1, an average pore size of 93 nm, and a narrow pore-size distribution.

Porous ceramic materials are in a current research focus because of their outstanding thermal stability, chemical stability and lightweight. Recent research has widened the range of applications to radar absorption to utilize the advantages of porous ceramic materials. There has been long-standing interest in the development of lightweight radar-absorbing materials for military applications such as camouflaging ground-based facilities against airborne radar detection. Therefore, in this study, a novel lightweight radar-absorbing material for X-band frequencies was developed using a self-setting particle-stabilized porous ceramic panel composited with carbon. The panel was prepared using a commercial calcium aluminate cement (as a self-setting matrix), zeolite 13X particles with propyl gallate (as a particle-stabilized pore former) and carbon (as a radar-absorbing material). The panel contained macropores approximately 200 to 400 μm in size formed by zeolite 13X particles that are irreversibly adsorbed at liquid-gas interfaces. The self-setting particle-stabilized porous ceramic panels were characterized by scanning electron microscopy, mercury porosimetry, physisorption analysis, capillary flow porosimetry and network analysis. When 0.2 wt.% carbon was added to a selfsetting particle-stabilized porous ceramic panel to fabricate a composite 7mm thick, the maximum reflection loss was −11.16 dB at 12.4GHz. The effects of the amount of added carbon and the thickness variation of a self-setting particle-stabilized porous ceramic panel on the radar-absorbing properties remain important issues for further research.

Porous ceramics have attracted research interest because of their high levels of thermal and chemical stability. Reticulated porous ceramics have been fabricated for several decades. However, insufficient data exists regarding the radar-absorption properties of reticulated porous ceramics. Therefore, the authors investigated the feasibility of using reticulated porous ceramics, prepared using alumina, as a platform for a radar-absorbing coating-material, such as carbon. The experimental data were used to determine whether carbon-coated reticulated porous alumina could be effectively prepared while maintaining an acceptable compressive strength by controlling the processing conditions. The structural properties and radar-absorption properties of the carbon-coated reticulated porous alumina material were examined using scanning electron microscopy (SEM), mercury porosimetry, and a network analyzer. The compressive strengths of the reticulated porous alumina specimens could be tailored by controlling the sintering temperature and the pore density of the polyurethane foams. The reflection loss of the reticulated porous alumina specimen with a thickness of 18.40 mm, coated with a carbon slurry with a carbon content of 10 wt%, was calculated as approaching −40 dB at 10.0 GHz.

Porous ceramic membranes are a current research focus because of their outstanding thermal and chemical stability. Recent research has utilised inexpensive natural materials such as diatomite to re...

Porous ceramic membranes have been widely studied recently owing to their outstanding thermal and chemical stability. In this paper, we investigate the preparation of an alumina coating over a diatomite-kaolin composite support layer in order to reliably tailor the porous coating structure and avoid defects, such as cracks. In particular, the effect of hydraulic pressure on the alumina coating was investigated using a flat-sheet membrane support. A flat-sheet diatomite-kaolin composite support filter was manufactured by an extrusion process. The characteristics of the membrane pores in an alumina coating on the diatomite-kaolin composite support layer were studied using scanning with electron microscopy, mercury porosimetry, and capillary flow porometer.

Porous ceramic membranes have attracted research interest because of their high thermal and chemical stabilities. Recently, silicon carbide membranes have been fabricated. However, insufficient data exist regarding the microfiltration applications of silicon carbide supports. We compared the measured membrane properties of alumina-coated silicon carbide and pyrophyllite supports. The experimental data were used to determine whether the average pore size of a silicon carbide support could be effectively reduced while maintaining acceptable water permeability by controlling the thickness of the alumina coating via a multiple dip-coating method. The membrane properties of the alumina-coated silicon carbide supports were examined using scanning electron microscopy, mercury porosimetry, and a dead-end microfiltration system.

SiC has excellent structural and mechanical properties and also has excellent properties related to membrane performance. High processing temperature increases the costs of SiC products and thus limits their use. In this study, we fabricated SiC-based ceramic support layers using a clay-bonding technique. Kaolin, a well-known clay, was used as a binder for silicon-carbide particles. Three different SiC powders were used on the basis of particle size for fabrication by the extrusion method, which converts powders into flat tubular form. The resultant supports are sintered at 1300–1500 °C in air and evaluated for their structural properties, pore characteristics and permeability. It is evident from the study that we can produce a support layer with small-sized SiC powder that has a high open porosity and high strength with a smaller pore size and lower permeability in comparison with layers produced with a large-sized starting SiC powder. Additionally, the produced support layer could be used as a stand-alone membrane for 1 µm particles.

Porous ceramic membranes are a current research focus because of their outstanding thermal and chemical stabilities. Recent research has utilized inexpensive natural materials such as pyrophyllite and diatomite to reduce the expense of these porous ceramic membranes. However, insufficient data exist for microfiltration applications using pyrophyllite-based membranes. We compared the measured membrane properties of alumina-coated alumina support layers and alumina-coated pyrophyllite-diatomite composite support layers. These experiments were used to determine whether we could effectively reduce the average pore size with acceptable water permeability by controlling the thickness of the alumina coating layer. The membrane properties of the alumina-coated alumina support layers and alumina-coated pyrophyllite-diatomite composite support layers were examined using scanning electron microscopy, mercury porosimetry, and a dead-end microfiltration system.

Recently, porous alumina-based ceramics have been extensively applied in the semi-conductor and display industries, because of their high mechanical strength, high chemical resistance, and high thermal resistance. However, the high electrical resistance of alumina-based ceramics has a negative effect in many applications due to the generation of static electricity. The low electrical resistance and high air permeability are key aspects in using porous alumina-based ceramics as vacuum chucks in the semi-conductor industry. In this study, we tailored the pore structure of porous alumina-based ceramics by adjusting the mixing ratio of the starting alumina, which has different particle sizes. And the electrical resistance was controlled by using chemical additives. The characteristics of the specimens were studied using scanning electron microscopy, mercury porosimetry, capillary flow porosimetry, a universal testing machine, X-ray diffraction, and a high-resistance meter.

Recently, porous ceramic membranes have become a subject of significant interest due to their outstanding thermal and chemical stability. To reduce the high manufacturing costs of these porous ceramic membranes, recent research has focused on the utilization of inexpensive natural materials. However, there have not been any well-established direct comparisons of the membrane properties between typical alumina-based membranes and novel natural material-based membranes. Therefore, we compared alumina-coated alumina support layers (with average pore sizes ranging from 0.10 µm ~0.18 µm), alumina-coated diatomite-kaolin composite support layers (with an average pore size of 0.12 µm), and alumina-coated pyrophyllite-diatomite composite support layers (with an average pore size of 0.11 µm) via the dip-coating method and subsequent heat treatment ranging from 1200 °C–1400 °C for 1 h. The pure water permeability of the alumina-coated diatomite-kaolin composite support layer and the alumina-coated pyrophyllite-diatomite composite support layer was found to be approximately 2.0×102 L m−2 h−1 bar−1, which is similar to that of an alumina-coated alumina support layer. Therefore, we suggest that the average pore size of an alumina-coated natural material-based support layer can be effectively controlled while exhibiting acceptable water permeability.

During the copyediting process, the author given and family names have been swapped. They should be read as follows.

Porous ceramic membranes are of special interest owing to their outstanding thermal and chemical stability. However, porous ceramic membranes with permeability usually suffer from low mechanical strength. Therefore, there have been a number of studies of the optimisation of membrane mechanical strength and permeability. In this paper, to avoid a trade-off between mechanical strength and permeability, we attempt to enhance these parameters by incorporating diatomite as both a pore former and a bonding phase. Because the flexural strength and air permeability of alumina support layers cannot be enhanced simultaneously by just changing the sintering temperature, we investigate whether they can be controlled by changing the amount of added diatomite. We study the effectiveness of diatomite as both a pore former and a bonding phase through a comparison of alumina–diatomite and the alumina–pyrophyllite composite support layers.

Recently, porous ceramic membranes have become a subject of significant interest because of their outstanding thermal and chemical stability. To reduce the high manufacturing costs and the complex processing steps of porous ceramic membranes that consist of a support layer and a separation layer, recent research has focused on the standalone use of a support layer. Therefore, in this paper, we report the results of our efforts to determine whether we could prepare an alumina support layer as a porous ceramic membrane that could effectively filter particles (an average particle size of approximately 1 µm, the ISO 12103-1 A3 test dust) while exhibiting acceptable water permeability. We also discuss the results of an attempt to compare the alumina support layer with the other porous ceramic support layers which have different pore characteristics such as a pyrophyllite–diatomite composite support layer and a silicon carbide support layer. The pore characteristics of the specimens were studied using scanning electron micrography, mercury porosimetry, capillary flow porosimetry, and a dead-end microfiltration system with particle counters.

Porous alumina ceramics are involved in many industrial applications due to the exceptional properties of these products. This study addresses the preparation of porous alumina ceramics using hollow microspheres as a pore-forming agent and slip casting as a green-body-forming technique. A uniform distribution of pores is a basic requirement of a porous material. This study investigates three different slurry systems, i.e., as-prepared alumina slurry, alumina slurry electrostatically dispersed by hydrochloric acid (HCl), and slurry dispersed by the commercial dispersant ‘Darvan C-N’. At a low viscosity, the hollow microspheres in the slurry tend to float, which causes a non-uniform pore distribution. To avoid this phenomenon, the viscosity of the slurry was increased to the extent that the movement of hollow microspheres ceased in the slurry. As a result, a uniform pore distribution was achieved.

Recently, porous ceramic membranes have become a subject of special interest due to their outstanding thermal and chemical stability. To alleviate the manufacturing cost issues of these porous ceramic membranes, recent research has been focused on the utilization of low cost natural materials. Therefore, in this paper, we report the results of our efforts to determine whether we could utilize diatomite as a pore former and whether we could prepare a pyrophyllite–diatomite composite support layer that could effectively control the largest pore size and permeability. The pore characteristics of the specimens were studied by scanning electron micrography, mercury porosimetry, and capillary flow porosimetry.

Very elastic poly(L-lactide-co-epsilon-caprolactone) (PLCL) (50:50) copolymer blended with gelatin was electrospun into microfibers from a hexafluoroisopropanol solution. PLCL fiber sheet exhibited the unique soft and flexible behavior while gelatin fiber was hard and brittle. As the gelatin content of PLCL/gelatin fibers increased, Young's modulus was increased, but the elongation was decreased compared to those of PLCL. However, fibers containing 10-30 wt% gelatin demonstrated an enhanced tensile strength with still high elongation to be beneficial for tissue engineering scaffolds. The cytocompatibility of electrospun fiber sheets was evaluated by fibroblasts (NIH-3T3) cell culture. The initial cell adhesion on various fibers after 5h was somewhat similar, but in the order of PLCL>PLCL70/gelatin30 approximately PLCL50/gelatin50>PLCL90/gelatin10 approximately gelatin>PLCL30/gelatin70. However, the cell proliferation exhibited a completely different and strong dependence on the fiber composition: a very high proliferation rate on PLCL90/gelatin10, followed by PLCL>gelatin>PLCL70/gelatin30. Such an enhanced effect of gelatin, especially at 10 wt% content, on strength and cytocompatibility of PLCL/gelatin fibers would be very preferable for tissue engineering scaffolds.