Porous Ceramic Materials Research Articles

Synthesis of Porous Ceramic Materials for Catalytically Active Membranes by Technological Combustion and Sintering

A porous, catalytically active membrane based on coarse-fraction silicon carbide was synthesized. Ultrafine additives with an eutectic composition of magnesium oxide and silicon carbide, which during sintering at temperatures from 1100 to 1450°C form a liquid phase in the form of clinoenstatite MgSiO3 that wets the coarse-size SiC particles and forms a strong porous framework of the membrane, were introduced into the initial SiC powder to synthesize the membranes. The pore size of the ceramic material was studied as a function of the pressing pressure, which made it possible to obtain a highly porous ceramic membrane with pore size optimized for dehydrogenation of ethylbenzene into styrene. Modification of the pore surfaces to 10% Re – W by means of active components using the alkoxy method is performed in order to give the synthesized membrane the catalytic properties required for realizing the dehydrogenation process.

Microstructural modeling of porous ceramic materials by homogenization method and prediction of sound transmission loss of particulate collection filter

Microstructural modeling of porous ceramic materials by homogenization method and prediction of sound transmission loss of particulate collection filter

PENGEMBANGAN BAHAN BAKU KERAMIK BERPORI UNTUK PENAMBAHAN TARIF PELAYANAN PADA BTIKK TAHUN 2019

The aims of this research were to: evaluate the recent ceramic raw material tariff, make the porous ceramic raw material alternative, select the porous ceramic raw material alternative, and propose the best porous ceramic raw material tariff with its financial variable as a new tariff. The research results shew that : the ceramic raw material service tariff according to Govermental Regulation Number 51 year 2018 is not enaough, because it followed by two tariff, that is : Rp 4.500,-each kg (white ceramic) and Rp 4.200,- each kg (stoneware ceramic), so the demand about glazur, castle mass, porous ceramic raw material, and others are nothing in the tariff. The development of porous ceramic raw material have been done by BTIKK which produce many compositon, that is : darkam-1 (75% Darmasaba clay : 25% husk), darkam-2 (70% Darmasaba clay : 30% husk), darkam-3 (65% Darmasaba clay : 35% husk), and darkam-4 (60% Darmasaba clay : 40% husk). The porous ceramic raw material with darkam-2 composition have been proposed as service addition to increase non tax revenue for BTIKK, because it closer to the requirements of raw material standard, it has been made water filter pot, it use Bali local raw material, and it result the economies cost of good manufactured. The financial variable of darkam-2 porous ceramic raw material followed by : cost of good manufactured Rp 3.858,73, cost price Rp 4.244,60, and operating profit margin Rp 308,70 each kg.

A compact standing-wave thermoacoustic refrigerator driven by a rotary drive mechanism

The design, the manufacture and the testing of a novel refrigeration system that is based on the thermoacoustic energy-conversion technology is reported. A 1-D linear acoustic model is specifically developed and carefully implemented in the present device. The system consists of two similar harmonically-oscillating pistons driven by a commercial 1-HP rotary drive mechanism operating at a frequency of 42 Hz -hereby, replacing typical expensive acoustic drivers-, and a thermoacoustic stack within which the energy conversion of sound into heat is taken place. Air at ambient conditions is used as the working gas while the amplitude of the driver's displacement reaches 19 mm. The 30-cm-long stack is a simple porous ceramic material having 100 square channels per square inch. Oscillating-gas pressure and temperature measurements show a maximum temperature span between the stack hot and cold ends of about 27° with an estimated Carnot COP around 11. A corresponding dynamic pressure of 7-kPa-amplitude is recorded (drive ratio of 7%) and found in a good agreement with theoretical prediction. The measured cooling effects at various phase shifts between the motions of the two opposite pistons show qualitative agreement with available theoretical values. However, the system behavior is noted to be clearly non-linear with significant energy loss mechanisms. This work helps understanding the operation principles of thermoacoustic refrigerators and represents a keystone towards developing commercial thermoacoustic refrigerators.

Structure and porosity of silicon oxycarbide/carbon black composites

This study describes the influence of carbon black (Cblack) on structural evolution and porosity of silicon oxycarbide (SiOC)-based ceramics obtained from pyrolysis of silicone-derived polymeric precursors. Initially, polymeric precursors were synthesized by hydrosilylation reaction between poly(methylhydrosiloxane) (PHMS) and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4Vi), with different Cblack contents (0, 1, 3, 5 and 10 wt%), followed by pyrolysis under argon at 1000 and 1500 °C, to give rise to the respective SiOC/Cblack ceramic composites. FTIR-ATR, TG, XRD, N2 gas physisorption at 77 K were used to characterize the carbonaceous phase, preceramic polymers and resulting ceramics. Cblack incorporation, together with the pyrolysis temperature, generated more porous ceramic materials and intensified the semiconducting SiC phase formation, maintaining the presence of conducting Cgraphitic structures embedded into SiOC matrices. Results concerning structural and textural features were associated to the different distributions of Cblack into polymeric precursors. Moreover, the availability of residual carbon to react with degradation products during pyrolysis and produce SiC and Cgraphitic crystalline phases was reported. Cblack immobilization into preceramic Si-containing polymers plays an important role to produce SiOC/Cblack ceramic composites with predominance of electroactive phases. The presence of Cblack also contributed to higher porosities on resulting composites, which are suitable features for electrochemical investigations in polymer-derived ceramic matrices.

Synthesis of nanoporous ceramic materials for filtration of liquids and gases by technological combustion method

Experimental and analytical studies on the synthesis of a Ti-Al-based ceramic material with a nanoscale porous structure were conducted. The results of previous studies conducted by the authors showed that it is reasonable to obtain porous ceramic materials designed for filtration of liquids and gases by thermal explosion (throughout the sample) rather than by layer-by-layer combustion. Self-propagating high-temperature synthesis (SHS) was used to obtain nanoporous ceramic membranes from a mixture of powders, wt.%: 40Ti + 60Al in one stage with the TiAl3 formation. It was found that the synthesized material consists of the main phase TiAl3 with a small amount of aluminum oxidized into Al 2 O 3 and unreacted. The microstructural analysis of the sample fracture showed that the resulting material has a developed surface and high open porosity. Empirically investigated open porosity is up to 48%, and the pore size ranges from 0.1 to 0.2 цт. The efficiency of the porous material obtained for the Ti-Al-based ceramic SHS filter reaches 99.999 %, gas flow resistance is 100 mmHg, filtration index is 0.062. Gas ultrafiltration capacity is up to 40 l/(cm 2 •h) at a pressure drop on the filter of 2 kPa, and water ultrafiltration capacity ranges from 2 to 10 l/(cm 2 •h) at a pressure drop on the filter of 0.1 MPa. Membranes made of ceramic materials with a gradient nanoporous structure by this method can be used as filter elements for small units providing fine water cleaning from bacteria, viruses, dissolved organic carbon, as well as for fine cleaning of air, process gases from dispersed micro-impurities and radioactive aerosols. The membrane SHS filters developed can also be used in units operating in aggressive environments and/or at high temperatures (up to 1000 °C).

Nanoporous high-temperature filters based on Ti–Al ceramic SHS materials

The research is devoted to the development of scientific bases for creating a technology for manufacturing heat-resistant membranes based on a highly porous ceramic material with nanoscale pores (nanoporous), which allows increasing the efficiency of high-temperature purification of liquids from submicron dispersed contaminants by tangential filtration. Membranes based on a mixture of Ti and Al powders (40% by 60% mass ratio) were synthesized in one stage using the SHS method in the thermal explosion mode and used as filter elements in the ultrafiltration unit. Using X-ray and SEM methods, it was found that the synthesized material consists of the main phases TiAl3 and Al2O3. Analysis of the microstructure showed that the resulting ceramic material has a multilevel highly developed web-like nanostructure that forms an open porosity of the membrane, providing the possibility of ultrafiltration.

Fracture Considerations for the Thermal Shock Resistance of Porous Ceramic Materials

The influence factors of thermal shock resistance of porous ceramic materials are analysed from the point of stress criterion and energy criterion. Results show that material properties, relative density and initial crack have important effects to thermal shock fracture of porous ceramic materials. In energy criterion, the total elastic energy is given. The driving force for crack propagation is provided by the elastic energy stored at fracture. When the elastic energy stored in porous ceramic materials is larger than the fracture energy, the crack will propagate. The relationship between crack length and initial crack length is given. In addition, the reason why the thermal shock resistance of porous ceramic materials is larger than dense ceramics is explained.

Sintering Behavior of Highly Porous Ceramic Materials Based on the Al2O3–MgO System

We have studied the sintering of ceramic samples based on magnesium oxide, alumina, and magnesium aluminate spinel in order to assess the conceptual feasibility of producing ceramic foam materials in the Al2O3–MgO system and examined the effect of sintering aids on the sintering process. The range of firing temperatures has been found that ensures the preparation of materials with an open cellular pore structure: the optimal temperatures are from 1600 to 1700°C. The porosity of the synthesized materials is up to 85% and their compressive strength reaches 1.4 MPa.

Perspective Biomass Carrier for Anaerobic Processing Systems of Organic Waste AIC

To speed up the wastewater treatment under aerobic conditions and to optimize the processes of anaerobic wastewater treatment in digesters, immobilization technologies of microorganisms and enzymes on solid carriers are used. Ceramic carriers based on aluminosilicates and alumina are one of the promising inorganic biomass carriers. (Research purpose) To study the structure of porous ceramic biomass carriers for anaerobic processing of organic waste and evaluate the prospects for their use. (Materials and methods) The substrate for anaerobic digestion was a mixture of sediments of the primary and secondary sewage sumps of the Lyubertsy treatment facilities. K-65 cattle feed was used to ensure the constancy of the composition of organic substances in substrates as a cosubstrate. The authors used the method of low-temperature nitrogen adsorption of Bruner-Emmett-Teller to study the pore structure and specific surface of solid carriers on a specific surface analyzer Quntachrome Autosorb-1. (Results and discussion) The main characteristics (specific surface, volume of micro- and mesopores, predominant pore radius, water absorption and others) of chamotte foam lightweight and highly porous corundum ceramics were determined. It was revealed that ceramic materials with a developed surface and electrically conductive material provided an increase in biogas yield by 3.8-3.9 percent with an increase in methane content by an average of 5 percent. (Conclusions) The results of anaerobic digestion showed a positive effect of both a conductive carrier and highly porous ceramic materials on the process of anaerobic bioconversion of organic waste into biogas. It is advisable to expand experimental studies on the use of a conductive carrier with a developed surface based on highly porous ceramics.

A Comparison of Mechanical Properties of Different Hydroxyapatite (HAp) Based Nanocomposites: The Influence of Morphology and Preferential Orientation.

Three different types of hydroxyapatite (HAp) based porous ceramic materials were obtained through the modified gel casting method; one of them was made of commercial HAp particles and used as a reference in the mechanical characterization. Other type of ceramic was elaborated using HAp nanofibers, which were synthesized through the microwave assisted hydrothermal method and they possess a high crystallinity, purity and a preferential crystalline orientation in the [300], such were grown along the [001]. The third type of porous ceramic was elaborated using a combination of HAp nanofibers and particles. The HAp nanofibers and particles were previously analyzed by using X-ray diffraction to study their crystal structure, the topology and morphology of those HAp aggregates were observed with scanning electron microscopy (SEM); high-resolution transmission electron microscopy was useful to carry out a detailed crystallographic analysis. Afterwards, an organic phase made of gelatin was added to the porous ceramics in order to obtain nanocomposite materials. Two different concentrations of gelatin were used separately, and the combination of three types of porous ceramics and two concentrations of gelatin produced six different nanocomposite materials. All of these composite materials were observed through the SEM to see their topology and porosity and after that, they were probed under compression tests and their corresponding mechanical behavior was analyzed. All the composites showed mechanical properties similar to those observed in cellular materials. The Young modulus and ultimate strength were compared, finally, it was determined the contribution to the mechanical properties of the morphology, crystalline quality and preferential crystalline orientation in the HAp nanofibers. According to such properties, the composite material made of HAp nanofibers has bone tissue implant potential applications.

Hydrophobization of Porous Ceramic Materials Based on Quartz Fibers with Solutions of Tetrafluoroethylene Telomers

Hydrophobization of highly porous heat-shielding ceramic materials based on quartz fibers was studied. Radiation-synthesized tetrafluoroethylene telomers having different chain length and different chemically active terminal groups were used as hydrophobizing agents. Comparative analysis of the performance of the telomers in modification of TZMK-10 material was made. Treatment with solutions of tetrafluoroethylene telomers allows making hydrophilic materials highly hydrophobic with the contact angle of the order of 140˚. This significantly improves the operation characteristics of the modified materials and expands the possibilities of using them as heat-shielding and heat-insulating materials.

Characteristics of lightweight diatomite-based insulating firebricks

This study covers the physical, thermal, mechanical, and microstructural properties of porous ceramic materials produced from mixtures containing refractory clay and diatomite in different proportions. The raw materials were characterized by chemical (X-ray fluorescence), thermal (thermogravimetry), morphological (scanning electron microscopy), and phase (X-ray diffraction) analysis techniques. The prepared samples were sintered at different firing temperatures between 900 and 1100 °C in an electrical furnace. The bulk densities, apparent porosities, linear dimensional shrinkages, compression strengths, thermal conductivities, and microstructural properties of the sintered samples were investigated. The porosity of the sample with 90% diatomite content increased to 55.4%, density decreased to 1.02 g/cm3, and thermal conductivity coefficient decreased to 0.32 W/mK.

Temperature dependence of the fracture strength of porous ceramic materials

In spite of the extensive use of porous ceramic materials in high-temperature applications, there are very few experimental and no theoretical studies on analyzing their temperature-dependent fracture behavior. In this work, in order to fill this research gap, a novel theoretical model for the characterization of fracture strength of porous ceramic materials with respect to temperature is proposed. The model considers the effects of the Young's modulus, specific heat capacity, volume fraction of pores, sizes of pore and flaw (critical flaw size). Further, through simplification the model can be used for the characterization of the strength of the dense ceramic materials. The models are verified by the obtained excellent agreements between the predictions and measurements. The experimentally observed phenomena are analyzed and explained according to the predicted results. Our analysis indicates that the temperature dependence of the fracture strength of the porous ceramic materials in vacuum is controlled by the Young's modulus and volume fraction of pores. While on high temperature oxidation the critical flaw size with respect to temperature should be considered. Furthermore, the temperature dependence of the strength of the dense ceramics is governed by the Young's modulus.

New types of the hybrid functional materials based on cage metal complexes for (electro) catalytic hydrogen production

Abstract Successful using of cage metal complexes (clathrochelates) and the functional hybrid materials based on them as promising electro- and (pre)catalysts for hydrogen and syngas production is highlighted in this microreview. The designed polyaromatic-terminated iron, cobalt and ruthenium clathrochelates, adsorbed on carbon materials, were found to be the efficient electrocatalysts of the hydrogen evolution reaction (HER), including those in polymer electrolyte membrane (PEM) water electrolysers. The clathrochelate-electrocatalayzed performances of HER 2H+/H2 in these semi-industrial electrolysers are encouraging being similar to those for the best known to date molecular catalysts and for the promising non-platinum solid-state HER electrocatalysts as well. Electrocatalytic activity of the above clathrochelates was found to be affected by the number of the terminal polyaromatic group(s) per a clathrochelate molecule and the lowest Tafel slopes were obtained with hexaphenanthrene macrobicyclic complexes. The use of suitable carbon materials of a high surface area, as the substrates for their efficient immobilization, allowed to substantially increase an electrocatalytic activity of the corresponding clathrochelate-containing carbon paper-based cathodes. In the case of the reaction of dry reforming of methane (DRM) into syngas of a stoichiometry CO/H2 1:1, the designed metal(II) clathrochelates with terminal polar groups are only the precursors (precatalysts) of single atom catalysts, where each of their catalytically active single sites is included in a matrix of its former encapsulating ligand. Choice of their designed ligands allowed an efficient immobilization of the corresponding cage metal complexes on the surface of a given highly porous ceramic material as a substrate and caused increasing of a surface concentration of the catalytically active centers (and, therefore, that of the catalytic activity of hybrid materials modified with these clathrochelates). Thus designed cage metal complexes and hybrid materials based on them operate under the principals of “green chemistry” and can be considered as efficient alternatives to some classical inorganic and molecular (pre)catalysts of these industrial processes.

多孔泡沫陶瓷催化材料降解臭氧实验研究

多孔泡沫陶瓷催化材料降解臭氧实验研究

Prospects for the creation of smart homes using energy-saving wall ceramic materials

The article discusses the prospects of energy saving in a ‘smart home’, taking into account the characteristics of consumer behavior. It is shown that the technical characteristics of the building in conditions of insufficient consumer awareness (passive approach to energy conservation) are preferable to the characteristics associated with intelligent solutions (active approach). It was revealed that special attention is paid to assessing the possibility of reducing the energy loss of a building by wall enclosures. In this regard, the effectiveness of the use of popular wall structural and heat-insulating materials, which reduce energy and material consumption in their production, is analyzed. The rationality of the production of porous ceramic products by the method of introducing into the mixture of mineral pore-forming additives with plastic molding is proved. A composition of porous ceramic material has been developed using local raw materials to create wall structural and heat-insulating products that meet the requirements of energy conservation.

Optical Properties of Porous Alumina Ceramics with Micron Open Cells

Porous ceramic material is widely used in a great deal of fields. In this work, porous alumina ceramics with micron open cells are modeled by applying the inverse opal structure. The considered porous alumina ceramics are periodic with different size parameters. The diameters of spherical pores are 200, 400, 600, and 800 nm, while the ratios of height to diameter range from 0.1 to 0.9. The absorptivity, transmissivity, and reflectivity for the wavelength range from 0.2 to 2 μm are calculated using the finite difference time domain (FDTD) method. Then the effects of size parameters and incident angle on the optical properties are discussed. The results show that the absorptivity is usually very small. For the transmissivity, a wide dip in the transmission spectrum appears when the diameter and height exceed the critical values, and a red shift of the transmission spectrum's wide dip with increasing height is observed. When the incident wavelength is longer than the critical wavelength, the spectral transmissivities of porous ceramics with a certain diameter reach a stable domain. Moreover, the red shift of the wide dip, the critical incident wavelength, and the critical ratio of height to diameter are visibly affected by the size parameters and the incident angle.

Nanosized iron-substituted hydroxyapatites

Introduction of iron ions into hydroxyapatites imparts some useful properties to ceramic materials. We created a porous ceramic material from nanosized iron-substituted HA and studied its physico-chemical and biological properties. It is shown that all the iron ions introduced in the course of synthesis enter into the composition of HA and are characterized by the oxidation state +3. The size of crystals after thermal treatment at 9000 C does not exceed 100 nm, the crystals’ shape is close to a sphere. Porous materials from nanosized iron-substituted hydroxyapatites support adhesion and growth of anchorage-dependent cells of mammals.

Transient behavior and thermal efficiency of volumetric heat receivers

Volumetric heat absorbers made of porous materials allow for a greater contact area between the porous matrix and the working fluid. In such devices, heat is collected in a volume rather than a surface. This work deals with transient behavior of Volumetric Heat Receivers using the thermal non equilibrium approach. Balances for energy amounts for the porous ceramic materials and air are solved numerically using the backward Euler discretization method and application of the SIMPLE method. After obtaining the algebraic equation system, relaxation by the SIP method is applied. We investigate here the effects of permeability, thermal conductivity ratio, inlet velocity and porosity on the temperature reached after thermal equilibrium. Higher inlet velocities attain quicker stabilization times and decreases equilibrium temperature, Teq. In addition, increasing porosity lower Teq and shorten time for temperature stabilization. Less permeable solid matrices, i.e. porous structures with lower Da, result in slightly higher Teq due to better enhancement of energy exchange between phases. Increasing kskf/ increases stabilization time as well as equilibrium temperatures. Thermal efficiency increases for lower inlet velocities and higher thermal conductivity ratios, whereas η is reduced for more permeable structures and higher porosities.