Porous Cordierite Research Articles

Highly porous cordierite ceramics from engineered basic activation of metakaolin/talc aqueous suspensions

The cellular structure, in alkali activated metakaolin-based suspensions, foamed by intensive mechanical stirring, is stabilised by the viscosity increase caused by gelation, in a condition of ‘inorganic gel casting’. The approach is so flexibile that it may be applied to mixtures embedding fillers, such as reactive γ-Al2O3 powders, playing a fundamental role upon ceramic conversion. The present study is dedicated to highly porous cordierite foams, obtained including talc as further component, and applying a heat treatment at 1200−1250 °C, in air. A key intermediate step is represented by the removal of Na+ ions from ‘green’ foams, by ion exchange in ammonium nitrate solution (24 h), before ceramization. Direct ceramization is also feasible, if the gelation is achieved by reaction with tetra-methyl-ammonium hydroxide, instead of NaOH. The new gels are effective in yielding phase-pure cordierite, otherwise feasible, with NaOH activation, by means of much longer ion exchange treatment (120 h).

Preparation and Modification of Mullite Whiskers/Cordierite Porous Ceramics for Cu2+ Adsorption and Removing.

In this paper, mullite whiskers were prepared by a molten salt reaction method based on a porous cordierite ceramic substrate (MC), and the modified mullite whiskers/cordierite ceramic sample (MCK) was obtained via the silane coupling reaction with γ-aminopropyl triethoxysilane (KH550). The structural morphology and phase compositions of the MC were characterized by X-ray diffraction and scanning electron microscopy. The surface functional groups of MCK were characterized using Fourier transform infrared spectroscopy, and the result showed that the amino group (−NH2) was successfully grafted onto the surface of cordierite ceramic. X-ray photoelectron spectroscopy analysis successfully showed inclusion of the amino and Cu2+ adsorption mechanism onto MCK. The adsorption properties of MCK were investigated using Cu2+ as the target pollutant by varying the experimental conditions such as pH, time, temperature, and initial Cu2+ concentration. The adsorption was found to be spontaneous, endothermic, and feasible, as indicated by the study of thermodynamic parameters. The adsorption kinetic analysis suggested that the pseudo-second-order kinetic model was best fitted for Cu2+ adsorption. The adsorption isotherm studies showed that the results of the Freundlich model are more suitable for experimental adsorption data than the Langmuir model. The adsorption–desorption cycle indicated that MCK had good reusability and stability. A novel porous ceramic-based adsorbent with high Cu2+ adsorption and removal efficiency was fabricated and has potential applications for the metal ion removing field.

Asymmetric porous cordierite ceramic membranes prepared by phase inversion tape casting and their desalination performance

Asymmetric porous cordierite ceramic membranes were fabricated by phase inversion tape casting method. It is shown that the membranes consist of a relatively dense skin layer on the top, a sponge layer at the bottom and a finger-like layer in the middle. The membranes have a hierarchical pore structure, where macrovoids (denoted as dozens-micron-sized (DMS) pores) are present in the finger-like layer and micron-sized (MS) pores are located in the skin layer, sponge layer and the wall of macrovoids. After surface silylation by post-grafting with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS), the sample with a starting powder/polyethersulfone (PESf) weight ratio of 9 (M − 4) becomes hydrophobic, with a water contact angle of 150°. At a NaCl concentration of 3.5 wt%, a feed rate of 18L/h and a feed temperature of 80 °C, the hydrophobic M − 4 membrane exhibits a water permeate flux of 22.33 kg/m2h, which is considerably larger than that of the membranes prepared by dry pressing method previously, and a salt rejection of 99.9%. The higher water permeate flux is attributed to the much lower transport resistance of water vapor in the membranes of the present work.

Preparation of porous cordierite ceramic with acid-leached coal gangue

The effect of impurities in coal gangue on the sintering and properties (porosity and compressive strength) of porous cordierite ceramics has been investigated by adjusting the amount of impurities by controlling the acid–gangue ratio during acid leaching. The sintering behavior and microstructure of the porous ceramics have been characterized via X-ray diffractometry and scanning electron microscopy. The effects of both the acid–gangue ratio and sintering temperature on the porosity and compressive strength have been also investigated. The results indicated that both porosity and compressive strength of the porous cordierite ceramics prepared using acid-leached coal gangue were evidently improved. The content of the impurities in coal gangue was adjusted via acid leaching by controlling the acid–gangue ratio. The appropriate content of impurities in coal gangue facilitated the sintering process and improved the porosity and compressive strength of the obtained porous cordierite ceramics.

In-situ synthesis and properties of porous cordierite ceramics with adjustable pore structure

Using high purity oxide (MgO, Al2O3 and SiO2) as raw materials, porous cordierite ceramics with a single phase and adjustable pore structure have been in-situ synthesized by foam gel-casting process. The effects of sintering temperature and foaming agent concentration on the phase composition, microstructure and properties were systematically investigated. The results indicated that pure cordierite could be obtained at sintering temperatures of 1430 °C and 1450 °C, while the sample sintered at 1450 °C showed better comprehensive performance. By adjusting the foaming agent concentration in the range of 2–32 g/L, the pore size of the materials could be controlled between 45.3 μm and 151.3 μm with the total porosity of 85.4–87.8%. When the sintering temperature was 1450 °C and the foaming agent concentration was 8 g/L, the prepared samples showed excellent properties and the near net size sintering was achieved. The sintering linear shrinkage was about 0.26%, the total porosity was 86.6 ± 0.2%, the bulk density was 0.35 ± 0.01 g/cm3, the compressive strength was 2.63 ± 0.33 MPa, the thermal conductivity was 0.217 ± 0.026 W/(m·K), the thermal expansion coefficient was 1.70 × 10−6/oC, and the permeability of deionized water was 3.62 × 10−11 m2.

Near net size sintering of porous cordierite ceramics with excellent properties

During the sintering process of porous ceramics, large volume shrinkage is often accompanied, which affects their preparation, porosity and properties vastly. Therefore, controlling and reducing the shrinkage in the preparing process is one of key points for high performance porous ceramics. Herein, the near net size sintering of high purity porous cordierite ceramics was achieved by means of the compensation for sintering shrinkage through the volume expansion derived from phase transition and synthesis reaction using Al2O3, SiO2 and MgO as starting materials. Through adjusting the solid content in the initial slurry of foam-gelcasting method from 20 to 30 vol%, the sintering linear shrinkage could be controlled in the range of −1.4–1.43%. Large porous cordierite ceramic parts with both relatively complex shape and high porosity (>85%) could be easily fabricated only using this method. The results also showed that when solid content was selected as 25 vol%, the linear shrinkage was low to −0.7% and the samples possessed both high porosity as 85.8% and high compressive strength as 2.6 MPa. The permeability coefficient was 2.07 × 10−11 m2 and the thermal expansion coefficient was 1.6 × 10−6/oC. This study might open an avenue for production and broaden the wide application of porous cordierite ceramics with high porosity.

Fabrication and characterization of porous cordierite ceramics prepared from fly ash and natural minerals

Low cost, single-phase porous cordierite ceramics are successfully synthesized by in-situ solid-state reactions from fly ash, quartz, and magnesite. The effects of sintering temperature and magnesite content on phase transformation, open porosity, bulk density, mechanical properties, and microstructure are carefully investigated. Factsage analyses are carried out to calculate the isopleth diagrams, and the results agree well with the experimental outcomes. Thermal gravimetric and differential scanning calorimeter analyses (TG-DSC) are performed to characterize the weight loss and transient behaviors of the raw materials. Linear thermal expansion properties are also studied. The α-cordierite phase is the only phase observed in S-3 (magnesite content 25%) sintered at 1300 °C for 2 h, and its linear thermal expansion coefficient (2.71 × 10 −6 K −1 ) is close to that of typical cordierite. Both the compressive strength (72.64 MPa) and flexural strength (23.92 MPa) of the as-synthesized samples are high with an open porosity of 33.16% and a bulk density of 1.61 g/cm 3 .

In Situ DRIFTS Investigation on CeOx Catalyst Supported by Fly-Ash-Made Porous Cordierite Ceramics for Low-Temperature NH3-SCR of NOX

A series of CeOx catalysts supported by commercial porous cordierite ceramics (CPCC) and synthesized porous cordierite ceramics (SPCC) from fly ash were prepared for selective catalytic reduction of NOx with ammonia (NH3-SCR). A greater than 90% NOx conversion rate was achieved by the SPCC supported catalyst at 250–300 °C when the concentration of loading precursor was 0.6 mol/L (denoted as 0.6Ce/SPCC), which is more advantageous than the CPCC supported ones. The EDS mapping results reveal the existence of evenly distributed impurities on the surface of SPCC, which hence might be able to provide more attachment sites for CeOx particles. Further measurements with temperature programmed reduction by hydrogen (H2-TPR) demonstrate more reducible species on the surface of 0.6Ce/SPCC, thus giving rise to better NH3-SCR performance at a low-temperature range. The X-ray photoelectron spectroscopy (XPS) analyses reveal that the Ce atom ratio is higher in 0.6Ce/SPCC, indicating that a higher concentration of catalytic active sites could be found on the surface of 0.6Ce/SPCC. The in situ diffused reflectance infrared fourier transform spectroscopy (DRIFTS) results indicate that the SCR reactions over 0.6Ce/SPCC follow both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. Hence, the SPCC might be a promising candidate to provide support for NH3-SCR catalysts, which also provide a valuable approach to recycling the fly ash.

Direct ink writing of porous cordierite honeycomb ceramic

Abstract Herein, we fabricated honeycomb ceramics with different porosities and pore shapes via the layer-by-layer deposition of cordierite (2MgO·2Al2O3·5SiO2) particle ink, obtaining proper rheological properties using a direct-writing technology. No collapses as well as minimal cracking and bending were observed in the internal structure of the samples after calcination. We measured and compared the internal porosity and specific surface area of honeycomb ceramics with the same pore shape but different pore dimensions, as well as the same pore dimension but different pore shapes. The samples were both loaded with an γ-Al2O3 washcoat and Pd-based catalyst using the same method for the catalytic combustion of toluene. The different porosity and pore shape influenced the catalytic efficiency. This study may provide some useful guidelines for fabrication of honeycomb ceramics by direct writing technology, which could be used to remove volatile organic pollutants(VOCs).

Porous cordierite ceramics prepared by foam-gelcasting technique: Phase evolution and properties

Porous cordierite ceramics with a single phase, high porosity and high strength were in-situ prepared using periclase, alumina and silica powders as raw materials by foam-gelcasting technique firstly. The reaction mechanism of preparing process was investigated via TG-DTA, X-ray diffraction, scanning electron microscope and electron energy disperse spectroscopy. The results confirmed that Mg(OH)2 was formed during the preparation of green body and cordierite was formed at 1325 °C through the intermediate phases of cristobalite and MgAl2O4 spinel. Samples with different performance have been fabricated by changing experimental parameters. Through altering holding time, sintering temperature and solid content in a certain scale, high porosity (83.9–89.2%), low bulk density (0.28–0.42 g/cm3) and high compressive strength (0.9–4.7 MPa) were obtained. The SEM images showed that the pore structure of the as-prepared material was multiscale, the cordierite grains were irregular and the grain size was below 5 μm. The method used in this paper shows great promise for preparing porous cordierite ceramics with single phase, high porosity and high strength.

Preparation of high solid loading and low viscosity ceramic slurries for photopolymerization-based 3D printing

In this study, high solid loading and low viscosity cordierite slurries are successfully developed for the first time for photopolymerization-based additive manufacturing. The processability of the slurries is mainly determined by their rheological properties and photocuring parameters. The slurry preparation involves the orthogonal optimization of compositions in order to achieve suitable viscosity, stability and homogeneity. The photocuring parameters of the as-prepared slurries, including penetration depth Dp and critical exposure Ec, are also determined experimentally. Results show that viscosity increases with reduction in particle size. A higher solid-volume fraction also results in an exponential growth in viscosity. As for the dispersant amount, a concentration of 5 wt% leads to the lowest viscosity. Particle size also play an important role in the solid loading capacity of the slurries, as results suggest that smaller particles improve performance. In terms of the photocuring behaviors, the addition of 2 wt% photoinitiator generates an optimal curing process. 40 vol% solid loading leads to the thickest curing depth for all slurries with different types of particle sizes. Finally, a cordierite part with a complex hollow structure and a fine resolution is successfully fabricated. The present study offers a material basis for the polymerization-based 3D printing of porous cordierite structures.

Porous Cordierite Ceramic with Pore Formers of a Different Nature

Results are provided for development of porous ceramic materials based on cordierite. The pore forming agents used are wood waste and carbamide in crystalline form. Analysis of the pore structure shows that all specimens have a complex pore space structure with a considerable number of elongated connected pores. The best porosity parameters are achieved using an organic crystalline pore former. It is shown that nano-dispersed aluminum metal has a strengthening effect during porous ceramic sintering. An organic clay suspension improves cordierite powder sintering capacity and leads to formation of additional nano- and micro-pores.

Porous cordierite ceramics with the poreformers of different kinds

The investigating results are given on the cordierite ceramic porous materials development. The wood waste and the crystalline carbamide were used as the pore-formers. The pore structure analysis showed that all samples had complex pore space composed of numerous elongated connected pores. The best pore formation factors were achieved when using the organic crystalline pore-former. It was demonstrated that nanodispersive metal alumina acted as the strengthening agent in course of the porous ceramics sintering. The organic clay suspension improves the cordierite powder's agglomeration capacity and gives rise to additional nano- and micro-pores.

Effect of glutinous rice flour and dried egg white in fabrication of porous cordierite by gel casting method

Abstract In this study, cordierite was produced using MgO, SiO2 and Al2O3 as raw materials through glass route method. The raw materials were mixed for 6 h and the mixture was melted at 1550 °C and then water quenched. The glass produced was milled for 5 h to obtain fine powder, which was used to prepare porous cordierite through gel casting method. The effect of addition of different natural binders, glutinous rice flour (GRF) and dried egg white (DEW), on porous cordierite was investigated. GRF and DEW were added to the slurry during mixing. The synthesized cordierite powder was analyzed by X-ray diffraction. Porous cordierite was characterized through Archimedes method, morphological analysis, and compression test. The porosity level varied from 60.6% to 78.7% depending on the amount of natural binder added. Compression test results showed that the compressive strength of porous cordierite increased with increasing amount of natural binder added.

Numerical modeling of thermally induced microcracking in porous ceramics: An approach using cohesive elements

A numerical framework is developed to study the hysteresis of elastic properties of porous ceramics as a function of temperature. The developed numerical model is capable of employing experimentally measured crystallographic orientation distribution and coefficient of thermal expansion values. For realistic modeling of the microstructure, Voronoi polygons are used to generate polycrystalline grains. Some grains are considered as voids, to simulate the material porosity. To model intercrystalline cracking, cohesive elements are inserted along grain boundaries. Crack healing (recovery of the initial properties) upon closure is taken into account with special cohesive elements implemented in the commercial code ABAQUS. The numerical model can be used to estimate fracture properties governing the cohesive behavior through inverse analysis procedure. The model is applied to a porous cordierite ceramic. The obtained fracture properties are further used to successfully simulate general non-linear macroscopic stress-strain curves of cordierite, thereby validating the model.

Effect of Solid Loading on Fabrication of Porous Cordierite

Effect of Solid Loading on Fabrication of Porous Cordierite

Influence of Technological Parameters on Thermal Properties of Cordierite Ceramics

Porous cordierite ceramic samples have been prepared by using 33% of two carbonate-containing illite clays as substitutes for the necessary synthetic ingredients. The changes of thermal (CTE) and mechanical properties (compressive strength, modulus of elasticity), as well as phase content, apparent porosity and bulk density have been investigated in regards to gradual changes in maximum sintering temperature. It can be affirmed that these properties strongly depend on the thermal parameters of sintering as well as slightly upon differences in chemical composition of composition substitutes.

Effect of Particle Size of Cordierite Powder on Pore Structure of Porous Cordierite

Porous cordierite is among the special porous ceramic due to its extensive properties. In this research, porous cordierite was fabricated through gelcasting method. A mixture of raw materials (SiO2, Al2O3 and MgO) was melted at 1550 °C followed by quenching in water to produce a glass. Then the formed glass powder were milled for 1, 3, 5, 7 and 9 hours to obtain various particle sizes of cordierite powder. Cordierite powder produced was then used to prepare 3-D porous cordierite ceramic using gelcasting method. The cordierite pellets were characterized. Surface morphology was analysed via Scanning Electron Microscope (SEM) to observe the pore structure of porous cordierite formed from powder with various particle sizes.

Interaction between Ca, Zn, and porous cordierite substrate at elevated temperatures

The interactions of both Ca and Zn with cordierite substrates were studied to better understand how Ca and Zn individually contribute to physio chemical changes in the cordierite diesel particulate filters (DPF) during high temperature engine exhaust conditions. The Ca and Zn doped cordierite samples were heated to temperatures of 300, 500, 900, and 1100 °C. Thermal treatment consisted of 1, 3, and 10 h exposure, separately, to simulate the duration of heat experienced by DPFs during use. Among the temperature profiles studied, SEM, XRD and EPMA mapping results indicate that the zinc–cordierite interaction is more severe in contributions to cordierite degradation than the calcium–cordierite interaction. The corrosion pathway generally followed the cordierite honeycomb porous structures. Appraised by the EPMA mapping, the element concentration across a given cordierite cross-section tends to increase for Zn doped samples, where calcium did not. XRD analysis indicate both the Ca and Zn can chemically interact with cordierite and alter the crystalline phases present at temperatures above 300 °C.

Preparation of porous cordierite ceramic by gel-casting method

ABSTRACTPorous cordierite ceramics were synthesised by gel-casting method, using talcum powder, kaolin and alumina as raw materials. Organic monomers and cross-linker were used as additives. The phase composition and microstructure were investigated by X-ray diffraction and scanning electron microscope. The open porosity, compressive strength and thermal expansion coefficient were tested by the Archimedes method, universal testing machine and thermal expansion instrument, respectively. The results indicate that sintering temperature and holding time have a great influence on the cordierite properties. We obtain the good performance of porous cordierite ceramic sintering at 1350°C for 3 h. The cordierite phase content in the sample is higher and the crystallinity is better. At this point, the porosity is 58.53%, the compressive strength is 22.44 MPa and thermal expansion coefficient reaches 1.69 × 10−6 °C−1.