Porous Cordierite Research Articles

Using anisotropy rationally to fabricate porous cordierite ceramic with enhanced mechanical properties based on supportless stereolithography

Through tailoring the printing strategy, the oriented microstructure including the layered cordierite skeletons and oriented pores of porous cordierite ceramic became controllable and the mechanical orientation enhancement was achieved via supportless stereolithography (SLA) combining with reactive template grain growth (RTGG). The results showed that the oriented microstructure was related to the oriented talc particles caused by the shear stress of the scraper. When the loading direction was perpendicular to the XY plane, porous cordierite ceramic possessed higher flexural strength owing to the deflection of crack caused by the oriented pores, while the loading direction was parallel to the XY plane, it possessed higher compressive strength, derived from the interconnected layered cordierite skeletons preventing the Euler buckling. Based on the orientation dominance models, with decreasing the layer thickness, the apparent porosity was similar while the flexural and compressive strengths both increased. When the layer thickness was 25 μm, the flexural and compressive strengths of porous cordierite ceramics both reached the highest value, respectively.

Low-temperature cordierite ceramics with porous structure for thermal shock resistance products

This article shows the results of the study of low-temperature (1100−1150 °C) porous ceramics of cordierite composition. The technological manufacturing parameters, the features of the microstructural and phase composition of ceramics have been studied. A decrease in the sintering temperature is achieved by appending a part of components using eutectic glass of MgO–Al2O3–SiO2 pseudoternary system. The principle of reactive formation of the structure of the ceramic sample is implemented in the process of its low-temperature firing. The formation of α-cordierite occurs in the process of firing ceramics by means of intensive interaction between eutectic glass components and crystalline fillers, as well as in the result of glass crystallization. By means of the thin layers of the glassy phase, cordierite crystals form a hard base with a branched system of interconnected open pores (30.0−31.3 %). The cordierite-phase crystals, forming the structure of ceramics, have a particle size ranging from 0.2 to 0.3 μm to 1.0−2.0 μm. The specific surface area of the porous cordierite ceramics is in the range of 4.2–4.7 m2/g. The developed cordierite ceramics is characterized by its low coefficient of linear temperature expansion (1.7–2.6)·10−6 °С−1, which determines its high thermal shock resistance (1000−1150°С). The ceramics may be used as filtering elements in high-temperature filtering units, as well as catalyst carriers in the exhaust systems of combustion engines for discharging the sooty component.

Fabrication of textured cordierite ceramics with low thermal expansion coefficient and custom structure via vat photopolymerization

Owing to the orientation of grains, textured ceramics possess particular properties along a specific direction. In this study, combining reactive template grain growth (RTGG) and vat photopolymerization, the textured cordierite ceramics with low thermal expansion coefficient (CTE) and custom structure were prepared successfully. Initially, the generation mechanism of the oriented c axis of α-cordierite grains in the XY plane was revealed by analyzing the evolution of microstructure during the sintering process. Then, two printing models were used to investigate the anisotropic CTE of porous cordierite ceramics fabricated by vat photopolymerization, indicating the effect of oriented grains and microstructure on the CTE. Finally, based on the selected dominant model, the controllable oriented microstructure was achieved by altering the shear stress provided by the scraper. The results showed that the oriented α-cordierite grains and skeletons were originated from the oriented tabular talc particles. Owing to the c axis of α-cordierite grains oriented in the XY plane, the CTE of the test direction parallel to the XY plane is lower than that perpendicular to the XY plane. In addition, with decreasing the setting layer thickness to adjust shear force, the oriented degree of tabular talc particles and α-cordierite skeletons became controllable. When the layer thickness reached a minimum of 25 μm, the CTE of porous cordierite ceramic reached the lowest of 1.26 × 10−6 K−1.

Digital light processing fabrication of porous cordierite ceramics from polysilxoane-based slurries

Herein, a pohotosentive polysiloxane (PSO)/talc/Al2O3 slurry was prepared for the digital light processing printing. Liquid photosensitive PSO was exploited as a triple-functioned material, acting both as the resin matrix, a high reactive Si source and a pore generator. Through adjusting the raw material components, polysiloxane can be sintered with talc and Al2O3 fillers after being pyrolyzed to 1200 oC while pores with variable diameters can be generated. Ternary component slurry prepared based on the above strategy possesses the characteristics of low viscosity, high reaction activity and good homogeneity. Sintering schedule of the printed thin-walled precursor was investigated to guarantee the morphology of cordierite product was consistent with the printed model. This work aims to provide a new strategy for DLP printing of MgO-Al2O3-SiO2 ternary and other polymer derived ceramics.

Effect of starch pore formers with different particle sizes on cordierite porous ceramics

Particulate matter (PM) from vehicle exhaust can be effectively removed by cordierite particulate filters. The pore size and distribution of the cordierite particulate filter are very important to PM trapping efficiency. The main factors affecting the pore formation of porous cordierite ceramics are the grain size of the feedstock, the size of pore-forming agent particles, the sintering process, etc. Talc, kaolin, silicon oxide, alumina, and boehmite were used as the raw materials, and the effects of starch pore formers of different particle sizes on the CTE, XRD, microstructure, pore size distribution, and mechanical strength of honeycomb cordierite were investigated.

Sintering and characterization of in situ formed porous cordierite ceramics with nano boehmite additions

AbstractIn this study, we investigated the effect of sintering temperature and nano boehmite additions on the phase composition, densification, and mechanical properties of porous cordierite ceramics. Ceramic samples were sintered at temperatures ranging from 1200 to 1400°C. Carbon powder was used as a pore forming agent to improve the porosity of the ceramic structure. Nano boehmite and carbon additions significantly enhanced ceramic porosity and average pore size in sintered samples. The bulk density and apparent porosity of the sintered samples were found to be 0.96–1.53 g/cm3 and 42.3%–65.6%, respectively. Sintered samples had cold crushing strengths of 1.5–14.3 MPa. The microstructure obtained by scanning electron microscopy was used to measure average pore size in sintered samples and was found to be 41.93 µm for stoichiometric composition (SC), 67.72 µm for SC and nano boehmite, and 102.98 µm for SC, nano boehmite, and carbon. The microstructure of the sintered samples revealed that the crystallinity of the in situ formed phases increased with the increase in nano boehmite additions.

Co‐utilization of secondary aluminum dross and ferronickel slag for preparation of cordierite–mullite insulating ceramic

AbstractBecause of the low utilization rate, a large amount of metallurgical slag was piled up or buried each year, resulting in serious environmental pollution and resource waste. This study focused on the value‐add utilization of secondary aluminum dross (SAD) and ferronickel slag (FNS) by preparing porous cordierite–mullite ceramics (CMC) for thermal insulation. The detailed thermodynamic calculation of the preparing process was carried out by using the phase diagram and equilibrium component function module in FactSage 8.1 software, which provided precise theoretical guidance for the practical synthesis experiment. The phase component, microstructure, and mechanical and thermal insulation properties of the prepared CMC at an FNS addition from 5 to 30 wt% were investigated by an X‐ray diffractometer, scanning electron microscopy assembled with an energy‐dispersive spectrometer, and a laser thermal conductivity testing instrument, respectively. It was shown that the original mineral phase of the raw materials applied can be converted to cordierite, mullite, and spinel after sintering at 1350°C, which results in higher strength and lower thermal conductivity of the prepared ceramics. Moreover, the increase of FNS addition promoted the content of cordierite and the microstructure densification of CMC. With the increase of FNS addition, the apparent porosity of CMC decreased from 41.7% to 34.4%, and the average pore size varied from 46.7 to 29.0 μm. The CMC with the lowest thermal conductivity of 0.86 W/(m K) was achieved at 20 wt% of FNS addition, which also had a good compressive strength of 52.8 MPa. The results proved the feasibility of preparing high‐strength thermal insulation ceramics by recycling hazardous metallurgical slag of SAD and FNS, proposing a novel route for high value‐added utilization of industrial solid waste.

The enhanced thermal shock resistance and combustion efficiency of SiC reticulated porous ceramics via the construction of multi-layer coating

SiC reticulated porous ceramic (SRPC) as the key component determined the service life and combustion characteristics of porous burner. The novel multi-layer struts were constructed to synergistically improve the oxidation resistance and infrared radiation of SRPC, including microporous cordierite coating, dense mullite transition layer, SiC skeleton and filling layer. The continuous mullite transition layer significantly improved the resistance to water vapor oxidation of SRPC, also their strength and thermal shock resistance were enhanced because the elimination of strut defects in multi-layer struts. In addition, the microporous cordierite coating generated from the burnt out of pitch increased the burner surface temperature from 764.4 °C to 1061.7 °C, and obviously reduced the CO/NOx emission due to its improved infrared radiation property. Furthermore, the porous cordierite coating enhanced the heat radiation of SRPC, thus increasing the heating rate of the burner from 29.4 °C/min to 33.1 °C/min in the process of water heating.

3D printing of cordierite materials from raw reactive mixtures

Porous cordierite materials are 3D printed by robocasting from two kaolin containing raw materials mixtures. Water suspensions of both mixtures at variable solid concentrations (40–67 wt%) are characterized by rheological measurements, showing good printability for concentrations >60 wt% without the need of any printing additive. The mixtures react during sintering (at 1250 °C) giving indialite as the main phase in the structures, which differ in minor phases. Three types of lattices are printed for both compositions with a logpile inner structure. Properties of interest like the coefficient of thermal expansion (CTE), the thermal conductivity (KT) and the compression strength (σ) of the printed cordierites are determined and compared with published data. Results evidence that printing of clay containing reactive mixtures is a straightforward and cost-effective way to achieve porous complex shaped cordierite with CTE∼ 2–3 x10−6 K-1, KT ∼ 0.4–0.6 W m−1 K−1 and maximum σ of 24 MPa.

Uniting printability and self-supportability of cordierite precursor pastes for fabricating cordierite ceramics with custom structures via supportless stereolithography

Cordierite precursor pastes including talc, alumina and silica particles were successfully prepared to fabricate porous cordierite ceramics by supportless stereolithography (SLA). To combining the printability and self-supportability properties of the pastes, the effects of the type and content of the dispersant on the rheological behavior were systematically investigated. Additionally, the effects of solid loading and plasticizer type on the rheological behavior of the cordierite precursor pastes were studied. It was found that 1 wt% Span80 was optimal for modifying the rheological behavior of the cordierite precursor pastes. Furthermore, the results indicated that the printability deteriorated, and the hysteresis area and yield stress of the cordierite precursor pastes increased rapidly when the solid loading exceeded 33 vol%. With the addition of 18 vol% plasticizers to replace UV-curing resins, dibutyl phthalate (DBP) was more effective in improving the printability of cordierite precursor pastes and ensuring self-supportability, compared with the polyethylene glycol 400 (PEG400). Finally, using the optimized cordierite precursor pastes, the porous cordierite ceramics with custom structures were successfully prepared.

Phase evolution and properties of porous cordierite ceramics prepared by cordierite precursor pastes based on supportless stereolithography

Porous cordierite ceramics with high flexural strength, low thermal expansion coefficient and custom structure were in-situ prepared using talc, alumina and silica particles by supportless stereolithgraphy (SSL) firstly in this study. To restrain the formation of defects, dibutyl phthalate (DBP) as low temperature pore-forming agent and a heating rate as low as 0.2 ℃/min were allowed to control the pyrolysis in the multistage debinding process based on thermal gravimetric analysis (TG). The effect of sintering temperature on phase evolution, microstructure and properties was investigated in details. The results showed that the generation of α-cordierite started at 1250 ℃ through the reaction between spinel and cristobalite, which generated volume expansion to offset sintering shrinkage. A porous cordierite ceramic with single phase was obtained at 1400 ℃. In addition, the coefficient of thermal expansion was as low as 1.65 × 10−6 /℃ and the flexural strength was 26.16 MPa with the apparent porosity of 48.62 %. The effects of configuration on the apparent porosity, shrinkage, mechanical and thermal properties were investigated by analyzing the phase composition and microstructure. Finally, the porous cordierite ceramic with custom structure was prepared successfully.

ZrO2 and MxOy (M= La, Ce, and Nb) synergistically reinforced porous cordierite ceramics synthesized via a facile solid-state reaction

In an attempt to enhance the sintering and mechanical performance of porous cordierite ceramics (Mg2Al4Si5O18) as support materials for vehicle exhaust catalysts, ZrO2 and MxOy (M = La, Ce, and Nb) were simultaneously introduced into cordierite sintered at 1350 °C for 4 h. Then, the reinforced function of ZrO2 and MxOy on the properties of porous cordierite ceramics was systematically evaluated, especially for the sample co-doped with ZrO2 and La2O3. The results displayed a distinct enhancement in mechanical and thermal performance, and the cold compressive strength increased from 72.74 to 158.59 MPa as well as thermal conductivity ranged from 1.66 to 2.01 W m−1 K−1, respectively. It is found that ZrO2 facilitated activation sintering introduced via lattice distortion in cordierite and La2O3 accelerated the formation of cordierite and ZrSiO4 microcrystalline through the low-temperature liquid phase. The synergic effect between ZrO2 and La2O3, therefore, had a significant role in the reinforced mechanical and thermal performance of porous cordierite ceramics. This work not only offers a feasible strengthening strategy, but also expands the possibilities for building high-performance structural and functional ceramics.

Experimental study on toughening of porous cordierite ceramic prepared by particle-stabilized emulsions

The majority of work has focused on the toughening of porous cordierite ceramics (PCC), which has a uniform and homogeneous porous structure prepared by the particle-stabilized emulsions after sintering at ∼1300 ℃ for 2 h. The particle sizes of raw materials were adjusted to 20 nm to ensure that all samples maintained the same porous structure, which prevented crack propagation from separating. PCC's bending strength increased by up to ∼214% at ∼4 wt% ZrO2 content, which absorb energy to improve fracture toughness. The addition of mullite fibers created new intermolecular forces between colloidal particles and filler parameters, which played a negative impact on the stability of the micelle shape, resulting in unsuccessful foaming and toughening. Rod-shaped cordierite crystals with a large aspect ratio were formed on the inner wall of PCC with 3 wt% AlF3 and created a short network in situ, which improved the bending strength of the tensile structure by strengthening crack deflection and crack bridging.

Structure-Controlled Porous Cordierite Ceramics with High Solid Content Prepared by Pickering Emulsion Technique Using Sucrose as a Porogen.

Porous cordierite ceramics (PCCs) with stable 3D microstructures were prepared by Pickering emulsion technique using sucrose as a porogen. The microstructural and mechanical properties could be adjusted by varying O/S ratios, sintering temperature, and sucrose content. The formation of the spherical structure was due to the broken oil bubbles. The appearance of cordierite and the concurrent consumption of sucrose were responsible for the observation of gradient pore structure. When the O/S ratio was 2, the pore-structure-controlled PCCs with cordierite as the main phase was obtained after sintering at 1300 °C. With the addition of 30 wt.% of sucrose, the obtained PCCs possessed high solid content of 45 vol.%, the porosity of 90.83%, the compressive strength of 6.09 MPa, and the optimized thermal conductivity of 0.4794 W/m.K. Compared with the predecessors’ research results, the as-prepared precursor of PCCs with sucrose content had the lowest initial Zeta potential without adjusting the pH to ensure the stable suspension. Our results showed that the addition of sucrose not only acts as a solvent to increase the solid content, but also acts as a pH modifier to maintain precursor stability, which enables the increase in compressive strength. In this work, via the scenario of “oil droplet” 3D accumulation, the stable and orderly spatial arrangement of the micro-emulsion system was successfully realized to obtain the structure-controlled PCCs by controlling the precursor conditions.

Preparation of porous cordierite/pseudo-wollastonite biocomposite and study bioactivity properties

The bioactivity properties of porous cordierite (C), pseudo-wollastonite (PW), and cordierite/pseudo-wollastonite (CPW) biocomposite ceramics were studied. Cordierite was prepared via melting, and pseudo-wollastonite was prepared via the wet milling method. Meanwhile, the cylindrical porous of cordierite (C), pseudo-wollastonite (PW), and cordierite/pseudo-wollastonite (CPW) biocomposite was fabricated using a gel-casting method, then sintering at 1250 °C for two hours. The X-ray analysis and SEM techniques were applied to find the phase and microstructure. The bioactivity properties of porous cordierite (C), pseudo-wollastonite (PW), and cordierite/pseudo-wollastonite (CPW) biocomposite were determined after soaking for seven days in the simulated body fluid (SBF) solution, which appearance layer of hydroxyapatite (HA) that exhibits a biological activity with the present of pseudo-wollastonite as compared with porous cordierite. The XRD patterns showed that the crystallinity of C and PW samples has decreased due to the HA formation after seven days of soaking. SEM tests revealed more HA microstructures in porous pseudo-wollastonite samples than in porous cordierite/pseudo-wollastonite. The effect of cordierite and pseudo-wollastonite in biocomposite ceramics is described in this paper.

Phase-engineering strategy of ZrO2 for enhancing the mechanical properties of porous cordierite ceramics

Porous cordierite ceramics, one of the major industrial materials used in heat transmission pipelines, have gained much attention due to their superior thermal properties. However, the unsatisfactory mechanical properties restrict their further application to some extent. In this work, the porous cordierite ceramics were prepared with fused magnesia, Al2O3, and SiO2 at different sintering temperatures from 1250 ℃ to 1400 ℃. To further reinforce the mechanical properties, ZrO2 characteristic of various phase types was regarded as sintering additives and then the enhancing mechanism was investigated. The phase evolution, microstructures, apparent porosity, bulk density, cold compressive strength, and thermal shock resistance of porous cordierite ceramics have been evaluated. The results indicated a great promotion on the mechanical (from 77.43 to 148.18 MPa) and thermal properties (from1.66 to 2.09 W m−1 K−1) by introducing the sintering additives. Furthermore, the strengthening mechanism of ZrO2 on porous cordierite ceramics was proposed, that is, the monoclinic phases facilitated the substitution reaction of Zr4+ and Mg2+ in cordierite, and the tetragonal phases were highly advantageous for the formation of ZrSiO4. Profiting from the delicate material phase composition modulation of ZrO2, the reinforced porous cordierite ceramics manifests outstanding mechanical properties and superior thermal stability.

Near net shape fabrication of porous cordierite by combination of foam gel‐casting and freeze‐drying

AbstractNear net shape fabrication of porous cordierite was successfully achieved through a combination of foam gel‐casting, freeze‐drying, and in situ synthesis. Environment friendly gelation was used as gel system, and the gelatin concentration influenced the drying shrinkage vastly. Combined with the volume expansion coming from phase transition and solid reaction during in situ synthesis of cordierite, the total linear shrinkage could be controlled around zero (−1.87% to 0.45%) by adjusting the gelation concentration and solid content in the slurry, meanwhile the prepared porous cordierite ceramics showed both high porosity (85.9%–91.1%) and high compressive strength (0.58–3.37 MPa). The sample with 0.05 g/ml gelatin concentration and 20 vol% solid content possessed excellent performance: total porosity of 89.1%, compressive strength of 1.36 MPa, and specific strength of 4.9 MPa/(g/cm3), showing the potential usage of filter carrier.

Hierarchically cell-window structured porous cordierite prepared by particle-stabilized emulsions using potato starch as a modifier

Porous cordierite ceramics (PCCs) with hierarchical microstructures were prepared by particle-stabilized emulsions method using potato starch (PS) as a modifier. The formation of hierarchical structure was ascribed to the removal of oil bubbles and consumption of PS during the sintering process. The volume shrinkage of samples tended to be stable with a solid content of 40 vol. %. When the PS content was 25 wt. %, PCCs with a controlled hierarchical pore structure up to 91.4% porosity, compressive strength of 5.76 MPa, and pore size of 6.19 μm was obtained. The thermal conductivity of PCCs was optimized to 0.4325 W/m K, along with the pore size distribution showing a single peak trend at the same time. The chemical corrosion of PCCs in both strong acid and alkaline medium was inhibited by the stable cordierite phase. The method of preparing PCCs with controlled hierarchical structured was potentially applicable in catalyst carrier and filtration.

Experimental Study on Toughening of Porous Cordierite Ceramic Prepared by Particle-Stabilized Emulsions

Experimental Study on Toughening of Porous Cordierite Ceramic Prepared by Particle-Stabilized Emulsions

Negative thermal expansion in porous glass-ceramics based on Mg2Al2B2Si5O18 prepared from Saudi raw materials

A porous glass-ceramic enjoyed very low and negative thermal expansion was prepared. A glass of the base molar composition, 2 MgO·2 Al2O3·2 B2O3·5 SiO2 with the addition of 1.61 ma% TiO2, was melted from kaolin, magnesite, silica sand and boric acid. The composition is based on cordierite where 50 % Al2O3 were replaced by an equimolar concentration of B2O3. The glass was crashed and powdered, subsequently plastified, uniaxially pressed and finally sintered at temperatures in the range from 1100 to 1300 °C. X-ray diffraction of sintered samples gave evidence of a cordierite like crystalline phase. Scanning electron microscopy and electron dispersive microanalysis of samples prepared at 1300 °C showed crystals with hexagonal shape doped by TiO2, B2O3 and Fe2O3 embedded in a glassy matrix. With increasing crystallization temperature, the porosity of the glass-ceramics increased from 8.99 % (at 1200 °C for 3 min) to 56.42 % (at 1300 °C for 3 min). This led to a decrease of the specimen density from 1.9880 to 1.1278 g/cm3 whereas the skeletal density increased from 2.1303 g/cm3 to 2.5878 g/cm3. The microhardnesses were in the 5.60 and 6.00 GPa range. The coefficient of thermal expansion was between −3.26 and −2.27×10−6 K−1 from room temperature up to 300 oC and −0.45 and 1.89×10−6 K−1 from room temperature up to 500 °C. For the first time, to the best of our knowledge, a porous cordierite glass-ceramic with negative thermal expansion is reported. The partial replacement of Al2O3 by B2O3 enables to apply lower melting temperature which is advantageous for the production process.