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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.

Acylhydrazone-based fluorescent conjugated microporous polymers (CMPs) with inter-and intra-hydrogen bonding-controlled emissive properties were prepared. The synthesized CMPs (BH-CMP and ABH-CMP) were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, solid-state 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and photoluminescence spectroscopy. Interestingly, BH-CMP exhibited emission enhancement via adsorption of water molecules, whereas the emission of ABH-CMP, which possesses free amine groups, decreased upon the addition of water molecules. The differences in the emission trends of BH-CMP and ABH-CMP in the presence of water molecules originate from the formation of different hydrogen-bonding networks in each CMP. The acylhydrazone-based CMPs were applied to the detection of nitroaromatic compounds. As a result, ABH-CMP in DMF exhibited high selectivity for 1,3,5-trinitrotoluene (TNT) over other nitroaromatic compounds nitrobenzene, 1-chloro-4-nitrobenzene, 2,3-dichloronitrobenzene, and 2,4-dinitrotoluene.

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.

For decades, porous ceramics have received much scientific and industrial interests because they possess better thermal and chemical stabilities than their counterparts, including porous polymers and porous metals. Among the numerous kinds of porous ceramics, reticulated porous ceramics have recently been prepared for various application fields. However, as far as the authors’ knowledge, the radar-absorbing properties of reticulated porous ceramics remain largely unknown, until now. Therefore, the feasibility of reticulated porous ceramics prepared using barium titanate, which has an inherently high dielectric constant, as a potential platform that could be used without additional radar-absorbing material coating has been discussed. From the results obtained in this study, it was discussed whether reticulated porous barium titanate could be fabricated with an acceptable mechanical strength and radar-absorbing properties. Quantitatively, the measured reflection loss (RL) of the 2.08-mm-thick reticulated porous barium titanate, approached − 16 dB (97.49% absorption of the radar wave) at 9.2 GHz. Meanwhile, the calculated RL of the as-prepared 2.50-mm-thick reticulated porous barium titanate approached − 21 dB (99.21% absorption of the radar wave) at 9.2 GHz.

Porous ceramics have attracted researchers due to their high chemical and thermal stability. Among various types of porous ceramics, reticulated porous ceramics have both high porosity and good permeability. These properties of porous ceramics are difficult to replace with porous metals and polymers. ZTA is used in a variety of applications, and a wealth of experimental data has already been collected. However, research reports on reticulated porous zirconia-toughened alumina (ZTA) are insufficient. Therefore, we prepared reticulated porous ZTA via the replica template method. In this study, various processing conditions (average particle size, zirconia content, solid loading, dispersant, and thickener) were adjusted to improve the compressive strength of the reticulated porous ZTA. As a result, the optimized processing conditions for improving the compressive strength of reticulated porous ZTA could be determined.

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.

Recently, porous ceramics have received much attention because of their excellent chemical and thermal stabilities, despite their mechanical instability. Among the various types of porous ceramics, reticulated porous ceramics (RPCs) have been newly fabricated. However, there is still insufficient data on the characteristics of RPCs for radar-absorption applications. Therefore, in this study, the feasibility of using RPCs of alumina (reticulated porous alumina, RPA) is investigated. It is examined whether RPA can achieve appropriate mechanical strength, be coated by a radar-absorbing material (RAM), and have radar-absorbing properties. The compressive strength of the RPA specimens is significantly enhanced from 0.07 to 1.03 MPa by the combined effect of increasing the number of alumina coating, sintering temperature, and pore density. The measured reflection loss is less than − 3 dB over the X-band range (8.2–12.4 GHz) for an 8.46-mm-thick RPA specimen coated with 40 wt.% cobalt slurry, which corresponds to 49.9% absorption. However, the calculated reflection loss of an RPA specimen with a thickness of 38.27 mm and coated with 40 wt.% cobalt slurry approaches − 15 dB at 10.0 GHz, corresponding to a 96.8% absorption of the radar wave.

Recently, porous ceramics have received much attention from researchers because of their excellent thermal and chemical stabilities compared to their counterparts (such as porous polymers and metals), despite their inferior mechanical instability. Among the various types of porous ceramics, reticulated porous ceramics have significant industrial potential because of their synergistic high porosity and permeability. However, to the best of our knowledge, there is insufficient data on the processing conditions or preparing optimal reticulated porous alumina. Therefore, we prepared and characterized reticulated porous alumina specimens by controlling various processing conditions, namely average particle size, solid loading, binder, and dispersant. The data obtained were used to assess whether the compressive strength of the reticulated porous alumina could be enhanced and to discuss the potential of these materials for various applications.

Numerous reports have elucidated that TiO2 nanoparticles (TiO2-NPs) exhibit respectable photocatalytic degradation capacities due to their high specific surface areas. However, the current recovery process leads to a loss of TiO2-NPs; therefore, there is a need to immobilize TiO2-NPs on the substrate used. Herein, TiO2-coated yttria-stabilized zirconia/silica nanofiber (TiO2-coated YSZ/silica NF) was prepared by coating TiO2 on the surface of YSZ/silica NF using a sol–gel process. The TiO2 coating layer on the nanofiber surface improved the separation ability of the membrane as well as the photocatalytic degradation ability. The pore size of the TiO2-coated YSZ/silica NF membrane was less than that of the pristine YSZ/silica NF membrane, and it rejected over 99.6% of the 0.5 μm polymeric particles. In addition, the TiO2-coated YSZ/silica NF membrane showed excellent adsorption/degradation of humic acid (HA, 88.2%), methylene blue (MB, 92.4%), and tetracycline (TC, 99.5%). Six recycling tests were performed to evaluate the reusability of the TiO2-coated YSZ/silica NF membrane. The adsorption/degradation efficiency for HA, MB, and TC decreased by 3.7%, 2.8%, and 2.2%, respectively. We thus verified the high separation ability, excellent photocatalytic degradation ability, and excellent reusability of the TiO2-coated YSZ/silica NF membranes.

Numerous reports have elucidated that TiO2 nanoparticles (TiO2-NPs) exhibit respectable photocatalytic degradation capacities due to their high specific surface areas. However, the current recovery process leads to a loss of TiO2-NPs; therefore, there is a need to immobilize TiO2-NPs on the substrate used. Herein, TiO2-coated yttria-stabilized zirconia/silica nanofiber (TiO2-coated YSZ/silica NF) was prepared by coating TiO2 on the surface of YSZ/silica NF using a sol–gel process. The TiO2 coating layer on the nanofiber surface improved the separation ability of the membrane as well as the photocatalytic degradation ability. The pore size of the TiO2-coated YSZ/silica NF membrane was less than that of the pristine YSZ/silica NF membrane, and it rejected over 99.6% of the 0.5 μm polymeric particles. In addition, the TiO2-coated YSZ/silica NF membrane showed excellent adsorption/degradation of humic acid (HA, 88.2%), methylene blue (MB, 92.4%), and tetracycline (TC, 99.5%). Six recycling tests were performed to evaluate the reusability of the TiO2-coated YSZ/silica NF membrane. The adsorption/degradation efficiency for HA, MB, and TC decreased by 3.7%, 2.8%, and 2.2%, respectively. We thus verified the high separation ability, excellent photocatalytic degradation ability, and excellent reusability of the TiO2-coated YSZ/silica NF membranes.

A simple polymer microsphere was dramatically transformed into a novel protein delivery carrier by the incorporation of hydroxyapatite (HA) into the polymeric phase. In this study, nano-sized HA was uniformly mixed in a gelatin/chitosan solution to ultimately form composite microspheres with a well-defined spherical shape. The physicochemical properties of these microspheres were extensively characterized in terms of morphological analysis, crystalline structure, swelling properties, etc. The average sizes of the microspheres increased slightly due to a gradual increase in viscosity of the HA-containing gelatin/chitosan solution. The typical characteristics of HA used in this work were confirmed to result in the successful fabrication of composite microspheres with graded HA content (0 to 55 %). The HA-containing microspheres showed outstanding features with respect to in vitro calcification, high protein loading/controlled release, and cytocompatibility. First, the addition of HA made composite microspheres greatly facilitated in vitro calcium ion deposition while initiating nucleation in stimulated body fluid (SBF). Second, the HA-involved composite microspheres acted as a highly efficient delivery system when compared to bare polymer microspheres. These features were mostly a result of the relatively good swelling properties and protein adsorption capability of HA. Third, the HA-containing composite microspheres showed significantly improved initial cell adhesion/proliferation. The increase in HA content and surface roughness provided a favorable matrix for the attached cells, which grew extensively in elongated, spindle-like shapes. In summary, this study investigated a high protein loading/controlled release system consisting of nano-sized HA as a key component, which contributed superior features of in vitro calcification and cytocompatibility.

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.