Papers by Keyword: Cordierite

Abstract: This study focused on the production of bioactive pure cordierite ceramic and the evaluation of its bioactivity by immersing it in simulated bodily fluid (SBF) and coating it on CP-Ti utilizing the dip coating Procedure. Cordierite is created by chemical coprecipitation, which involves combining Cordierite gel with a water-based sol-gel composed of Alumina Al2O3, magnesium oxide MgO, and silicon oxide SiO2. They used a hydraulic press to form cordierite into a cylindrical shape with a pressure of 4 bar and a holding time of 30 minutes at this pressure. Firing presses reach temperatures of 1250 C^o and have a holding time of 2 hours. A Field Emission Scanning Electron Microscope (FESEM) was used to examine the microstructure, which revealed a homogenous distribution of the compounds with negligible porosities. The phase transitions that cur during the sintering Process is studied using X-ray diffraction (XRD). The structural investigation of specimens revealed the formation of the cordierite phase at 1250 C^o, as well as the development of cristobalite, spinel, protoestatite, and corundum with cordierite phase. The dip coating Procedure was utilized to cover commercial pure titanium (CP-Ti) samples with cordierite powder. CP and Tafel exploration tests show that coated CP-Ti has superior passivation than uncoated Substrate. By comparing the findings of uncoated and coated CP-Ti, this paper concludes that the cordierite system acts as a good passivation layer.

Abstract: Cordierite powders were synthesized via a melt-quench method. The samples were melted at 1550°C for 4 hours and immediately quenched in distilled water. The bioglass ceramic frit was milled and calcined to produce cordierite powders. After that, cordierite was treated with calcium acetate as a calcium salt in order to enhance the bioactivity of cordierite. The powders were immersed in calcium acetate solution for 24 hours and dried in the oven at 80°C for 24 hours. The mixtures were pressed into pellet form for bioactivity testing. Then, cordierite pellets were soaked in simulated body fluid (SBF) solution for 7 days. SEM micrographs show the formation of the hydroxyapatite layer on its surface after soaking in SBF solution. While EDX analysis shows the presence of calcium after the treatment. The presence of cordierite and hydroxyapatite phases were confirmed by XRD analysis.

Abstract: The bioactivity properties of pure cordierite (C), pure β-wollastonite (W), and cordierite/β-wollastonite (CW) biocomposite ceramics were studied. Cordierite was prepared via melting, while β-wollastonite was prepared via the wet milling method. A bioactivity test showed that hydroxyapatite (HA) was non-existent in the pure cordierite sample after seven days of being soaked in simulated body fluid (SBF). On the other hand, the cordierite/β-wollastonite bioceramics showed that HA formation has entirely covered the surface of these samples. The XRD patterns showed that the crystallinity of W and CW samples has decreased due to the amorphous calcium phosphate (ACP) formation after seven days of soaking. SEM tests revealed that more ACP microstructures were present in cordierite/β-wollastonite samples than those in pure β-wollastonite. The effect of cordierite and β-wollastonite in biocomposite ceramics is described in this paper.

Abstract: In this study, a composite of bioactive glass and cordierite (BG/cordierite) was proposed to increase the strength of bioactive glass (BG). Both BG and cordierite were separately synthesized with the method of glass melting and used to fabricate BG/cordierite with sintering temperature in the range from 600 to 1000 °C. The BG/cordierite were characterized using X-ray diffraction (XRD), density, bulk density, porosity and hardness test. The XRD pattern shows amorphous phase and crystalline phase such as combeite, wollastonite and larnite appeared after sintering. The highest hardness value show by BG/cordierite with sintering temperature 950 °C (BG/C950) with 251 Hv.

Abstract: In order to synthesize cordierite ceramics with low thermal expansion coefficient and good properties, in our work, the cordierite ceramics were prepared by using talc, natural containing zirconium kyanite, common kyanite and industrial Al₂O₃ as raw materials, introducing the right amount of WO₃ (introducing tungsten acid) as catalyst. The effects of the introduced WO₃ on the phase composition, sintering characters, microstructure and thermal expansion coefficient of the cordierite ceramics were investigated. The results show that the introduction of WO₃ can eliminate the intermediate phase magnesia-alumina spinel and promote the formation of cordierite; the as-prepared cordierite ceramics synthesized by using natural containing zirconium kyanite as raw materials have high densification degree and low thermal expansion coefficient (1.53×10^-6/°C, Rt~1000 °C).

Abstract: In this paper, effects of incorporation of Narathiwat clay (NT), talc and silica on the mechanical properties of cordierite-mullite refractories were investigated. The starting raw materials were mixed in different ratios and fired at 1300 °C for 2 hours. XRD patterns of fired refectories indicated cordierite and mullite phases. The fired samples were studied the firing shrinkage, water absorption, bulk density, apparent porosity and bending strength of the cordierite-mullite refractories. The optimum condition was achieved for the composition of 20% Talc that had shrinkage: 11.78%, water absorption: 4.16%, bulk density: 2.28 g/cm³, apparent porosity: 9.2% and bending strength: 330.82 kg/cm². The results thus showed that Narathiwat clay, talc and silica was a potential materials for use kiln furniture cordierite-mullite refractories.

Abstract: 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.

Abstract: Highly porous cordierite ceramic by using of talcum, kaolinite and γ-alumina was obtained by method of slip casting of concentrated suspension. Additives of amorphous silica and non-stabilized zirconia in the amount of 5 wt% were used. Sintering temperature of dried samples was in range of 1250 – 1450°C. All the samples contain crystalline phases of cordierite, mullite and corundum but, depending on the additives, as a result of sintering in addition forms spinel, cristobalite or zircon (ZrSiO₄). Porosity of obtained materials changes in large scale from 42 to 59 per cent; it is influenced by both sintering temperature and composition. Compressive strength increases with the addition of zirconia. In comparison, compressive strength of samples without additives or with silica additive does not exceed 3.5 MPa. The increase of coefficient of thermal expansion depends both on the composition and sintering temperature. ZrO₂ additive increases the coefficient of thermal expansion considerably.

Abstract: Mechanical fatigue due to repeated thermal shock cycling is of great importance for most materials intended for refractory applications. This work explores thermal shock resistance and cyclic thermal shock effects of cordierite ceramic made from clay-containing mixtures. Different means of detection of change in modulus of elasticity have been employed including impulse excitation and dynamic-mechanic tests (DMA). Results have shown that the elastic modulus of cordierite ceramic gradually decreases over thermal shock cycles, the sharpest change being observed after the first cycle. Unlike synthetic cordierite ceramic material, clay-substituted cordierite composites show "self-healing" effect, which can be explained by the gradual filling of cracks with glassy phase that leads to the strengthening of the whole structure of material. This effect is directly dependent upon the composition of the sample and the material with lesser amount of glassy phase can be characterized with the largest inertia of this effect.

Abstract: This work aims to investigate the crystallization kinetics of β-spodumene/cordierite glass-ceramics. Thus, three glasses with compositions based predominantly on cordierite (C), β-spodumene (L) and in a molar ratio 1:1 of both phases (CL) were prepared. The kinetics parameters such as activation energy for crystallization (ranging from 160 to 358 kJ/mol) and Avrami exponent (ranging from 1.4 to 10.7) were determined by means of non-isothermal methods using differential scanning calorimetry (DSC). Additionally, the samples were crystalized according to DSC analyses and characterized by using x-ray diffraction (XRD). The main detected crystalline phases were β-spodumene to the glass L, cordierite to the glass C and β-quartz, mulite and spinel to the glass CL. Considering the thermal and electrical properties of these crystalline phases, these glass-ceramics have potential use for LTCC (Low Thermal Co-fired Ceramics) applications.