Papers by Keyword: Cordierite

Abstract: Catalytic combustion of VOCs was investigated over Mn–Zn mixed oxides supported on cordierite ceramic (Cord) and over the promoted Mn-Zn oxides with γ–Al₂O₃ coating. The properties and performance were characterized by using the XRD, SEM, BET, and TPD techniques. Mn-Zn oxides catalysts with different kinds of γ–Al₂O₃ sol coating were found to possess a high activity, and the Mn–Zn/γ–Al₂O₃/Cord (Mn/Zn=2) was identified as the most active that the temperature of complete combustion of toluene was 250°C. Effects of variation of preparation conditions, including molar ratio of Mn and Zn, loading, calcination temperature and different kinds of γ–Al₂O₃ dipping were investigated.

Abstract: The V₂O₅-WO₃/TiO₂ honeycomb catalysts with cordierite modified were prepared by solid-liquid mixing method. Its thermal stability, crystal structure, abrasion resistance and activity were studied by XRD, abrasion equipment and simulated flue gas analyzer,respectively. The results indicated that V₂O₅-WO₃/Cordierite-TiO₂ honeycomb catalyst possessed a better thermal stability, mechanical property and activity at the higher temperature comparing to commercial catalyst. There was no rutile phase present after the catalysts were calcined at 700°C, and the vanadia and tungsten trioxide phases could be apparently visible on TiO₂. Key word:V₂O₅-WO₃/ TiO₂; Cordierite; flue gas denitrification; NO_x; selective catalytic reduction (SCR)

Abstract: Cordierite (2MgO·2Al₂O₃·5SiO₂) has a low density of 2.2 g/cm³ due to its high magnesium content. Because of its low thermal expansion coefficient of 1~2 x10^-6 /^°C, many studies are being conducted on the synthesis of cordierite with the expensive petalite as a replacement for lithium alumina silicate-based heat-resistant materials. The cordierite can be synthesized over a wide range: SiO₂ at 50~70%, Al₂O₃ at 20~40%, and MgO at 10~30%. In this study, the range of chemical composition and temperature of cordierite synthesis is thoroughly investigated. In particular, we use natural materials (magnesite, kaolin and clay) to examine how thermal properties are affected by changes in crystal phase arising from the varying composition of MgO, SiO₂ and Al₂O_3. We focused on factors leading to an increase in the rate of cordierite synthesis at temperatures below 1280 ^°C. From observing the synthetic rate over 1250~1280 ^°C, the sintered body at 1280 ^°C had a high synthetic rate greater than 80%. Magnesite was ball milled at constant intervals, and mean particle size was controlled to improve the synthetic rate of cordierite. As a result, the cordierite synthetic rate increased by more than 15% with decreasing the mean particle size of magnesite.

Abstract: Cordierite (2MgO.2Al₂O₃.5SiO₂) is an advanced ceramic which is popular for its high melting temperature and high resistance to thermal, chemical and corrosion and also low dielectric constant. The use of various structure of cordierite especially porous structure became more popular where its properties can be tailored by controlling the open and closed porosity, cell size distribution and cell morphology. In this study, porous cordierite was synthesized using sol gel method with addition of corn starch (5wt%, 10 wt%, 15 wt% and 20 wt %) as pore forming agent. Characterizations have done using scanning electron microscope (SEM) show that the corn starch used is polyhedral shape with pore size between 6-7 μm. Whereas SEM analysis on sintered sample shows that the porosity obtained ranging from 13 to 46 % with interconnected pores.

Abstract: Cordierite (2MgO.2Al₂O₃.5SiO₂) is widely used in high temperature applications due to its high melting temperature and high resistance to thermal, chemical and corrosion shock. The use of various structure of cordierite especially porous structure became more popular where its properties can be tailored by controlling the open and closed porosity, cell size distribution and cell morphology. In this study, porous cordierite was synthesized using sol-gel method followed by replication of polymeric sponge method using three different types of polymeric sponge (Type A, B and C). Immersed sponge were then sintered at 1300°C to determine better sponge types to produce porous cordierite. Sponge was characterized using FTIR and porous sample produced were characterized using Scanning Electron Microscope (SEM) and density and porosity testing.

Abstract: The porous SiC-cordierite ceramics were prepared from SiC, calcined kaolin, talc, aluminum hydroxide, and graphite as pore-forming. The influence of pore-forming agent contents and sintering temperatures on the porosity and flexural strength of porous SiC-cordierite ceramics were investigated. The grain phases and the fracture surface micrograph were analyzed with XRD and SEM, respectively. The results show that the sample sintered at 1350°C for 3h with 15% graphite as the pore-forming agent exhibits the most excellent properties: flexural strength of 63.74MPa was achieved at a porosity of 31.80%.

Abstract: Titanium silicalite-1(TS-1) membranes were prepared on cordierite support by hydrothermal treatment. The TS-1 membranes were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD) and FT-IR, The factor that the ratio of TPA+/Si on influencing TS-1 crystal was investigated and it was indicated that the ratio of TPA+/Si had a strong effect on its morphology. The TS-1 crystal presented ellipsoid when ratio of TPA+/Si was 0.15. However, the morphology of TS-1 crystal changed to coffin-shaped when the ratio of TPA+/Si increased to 0.4. Each lattice plane of TS-1 crystal grew on cordierite support with different speed which was controlled by concentration of structure-directing agent SDA (TPAOH) in precursor solution. The mechanism of TS-1 crystal growth on cordierite support maybe that the TPA+ in the solution attracts silicate species, titanium species to form inorganic-organic composite species, the aggregation the inorganic-organic composite species formed crystal nucleus, the morphologies changed due to the growth rate of different lattice planes.

Abstract: The cordierite was synthesized at relatively low temperature by pressureless sintering method, using calcined bauxite, talcum , quartz and feldspar as raw materials in this paper. The water absorption (Wa), porosity (Pa), bulk density (D_b) and bending strength of samples have been tested, and the synthetic process and mechanism have been investigated by XRD, SEM, and so on. The results showed that the cordierite could be synthesized at 1280°C and the range of synthetic temperature is 1160~1300°C, when the sample was sintered at 1280°C for 2h, its bulk density and bending strength were 2.20g/cm³ and 72.13MPa, respectively. XRD analysis showed that the main phase of sample was cordierite, the cordierite content was about 88wt%, and the minor phases were MgAl₂O₄ spinel and corundum. SEM results showed that the samples were dense and the pore sizes were 5 μm~100μm, the grains were growth and development well, the grains size were 0.5μm~6μm. High reaction activity corundum and mullite were provided by calcined bauxite, then coupled with the role of feldspar, thus reduced the synthetic temperature of cordierite.

Abstract: Mullite-aluminum titanate-cordierite multiphase ceramics were prepared by high alumina clinker, Aluminum Titanate and Cordierite. The sintering property and thermal shock resistance of composite materials were tested. The experimental results show that the sinter property and themal shock resistance of Mullite-aluminum titanate-cordierite multiphase ceramics are relatively preferably, which the materials composition are 30 wt.% high alumina clinker, 60 wt.% cordierite and 10 wt.% aluminum titanate. The component samples show porosity of 33.17%, volume density 1.9 % and normal temperature flexural strength 20.66 MPa. Thermal residual flexural strength of the samples is still as high as 10.29 Mpa by 5 times thermal residual tests, and there are only little flexural strength lower after three times earthquake test.

Abstract: Reagent grade chemicals were used to explore glass formation ability and allocate the glass forming area for the glass system SiO₂-P₂O₅-Al₂O₃-MgO-Na₂O. FT-IR, DTA, DSC and TMA techniques were employed to characterize the obtained glasses. The multicomponent, mixed network glasses, in which AlPO₄ tetrahedral units are being incorporated into the network structure through substitution for pairs of SiO₄ tetrahedra, exhibit high durability, low thermal expansivity (at Al₂O₃/P₂O₅ ˃1), relatively high softening temperatures (at low P₂O₅ contents) and an increased thermal stability (poor tendency for crystallization). When heated at high temperatures and / or for long periods of time, and depending on their AlPO₄ content, together with the Al₂O₃/P₂O₅ ratio, the glasses crystallize through a multistage process involving reconstruction and depolymerization of the glasses network structure. The crystallization behavior of many different glasses was investigated, phases identified and characterized, through XRD, and SEM coupled with EDX and X-ray mapping together with optical microscopy. The powder ceramization route had to be used to achieve the devitrification of the glasses with high thermal stability. Berlinite, corundum, spinel, indialite and cordierite among others were the crystallizing phases when different glasses were heated for various times. Microporous materials made of some of these technically favorable minerals, and characterized by an interesting morphologies were obtained, through acid leaching of some of the glass-ceramics produced. It is believed that the glass system under investigation is a fertile one, the crystallization of some glasses within it, represents another fabrication route for obtaining glass-ceramics with specific crystalline phases, as well as microporous materials made of such phase. In both cases, packages of the most suitable properties are obtainable.