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In-Situ Synthesis of Mullite Fibers Reinforced Zircon-Zirconia Refractory Ceramic Composite from Clay Based MaterialsAramide, FO, Alaneme, KK, Olubambi, PA, Borode, JO 01 December 2015 (has links)
Abstract
Understanding the phase transformations/developments that result due to varying the production parameter of
engineering materials is vital to development of new materials. The effects of yttria and niobium oxide on the phase changes
and mechanical properties of mullite fiber reinforced zircon-zirconia ceramic composites produced by in-situ sintering of raw
materials was investigated. Varied amounts of powder zirconia, yttria and niobium oxide were mixed in a turbula mixer with
a fixed composition of clay (70% volume) of known mineralogical composition and mechanically milled in a planetary ball
mill. The blended powders/clay were compacted into standard sample dimensions, and finally fired at 1400°C and held at
varied time of one, two and three hours. The fired samples were characterized using ultra-high resolution field emission
scanning electron microscope (UHR-FEGSEM) equipped with energy dispersive spectroscopy (EDX), and X-ray
diffractometry (XRD). Various mechanical properties of the sintered samples were also investigated. It was observed that the
investigated mechanical properties (with the exception of shrinkages) improved with the amount of raw zirconia initially used
in the samples. It was also observed that addition of niobium oxide favours the formation polymignite phase, while the
presence of both yttria and niobium oxide in the raw materials resulted in the formation of fergusonite phase in the samples.
Both additives favour the phase transformation of zirconia from monoclinic to tetragonal and cubic phases even at
temperature as low as 1400°C. It was concluded that the improved mechanical properties of the samples was due to
strengthening by both mullite fibers reinforcement and phase transformation strengthening.
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Formation of mullite during sintering of kaolinite powderWu, Chia-Han 10 September 2009 (has links)
There are lots of reactions in formation of mullite during sintering of kaolinite powder at high temperature. Primary mullite (M(I), 2Al2O3¡PSiO2) is the result of a solid state reaction of kaolinite. And secondary mullite (M(II) or M(III), 3Al2O3¡P2SiO2) is formed by vitrification after nucleation and grain growth. It has been investigated that the growth mechanism of secondary mullite and the texture of ceramics are affected by the process of green tape. Expect that the growth direction of crystal has been analyzed, the texture of kaolinite green tape formed by tape casting after sintered can not be reproduced.
In order to realize the mechanism in formation of mullite we study different green tape process by vitrification and observe the microstructure of mullite after sintering.. The microstructure is analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
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The effect of the anion and cation of the catalyst on the catalytic mullitization of kaolinite /Prentice, William H. January 1951 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute. 1951. / Abstract. Includes bibliographical references (leaves 29-30). Also available via the Internet.
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Effect of radiation damage on the formation of mullite in kaoliniteHead, Clarence McMahan 12 1900 (has links)
No description available.
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Sintering, densification and creep of fine grained mulliteWakefield, R. January 1985 (has links)
No description available.
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The reduction of silica and mullite in hydrogen /Chen, Chung-I January 1979 (has links)
No description available.
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Study of diamond/mullite composites by sol/gel and hot press sintering methodsGovo, Simbarashe Piniel 15 April 2011 (has links)
MSc, School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment / A study has been conducted into the synthesis of 10wt% diamond/ mullite composites
through two methods: First through the hot press sintering of alumina and silica in
stoichiometric composition for 3:2 mullites (mullite formed in situ) at 1400, 1450 and
1500oC. Second through the sol/ gel process. The sol/ gel method only provided the basis
for future development with no further discussion of the results while the hot press
sintering method yielded composites with residual cristobalite and corundum phases.
Achieved densities of the composites were 93.7, 94.6 and 95.8% of the theoretical density
with respect to sintering temperatures of 1400, 1450 and 1500oC for compact samples by
the first method. Hardness – measured by Vickers indentation – of the composites
decreased with increase in temperature with 15.5 ± 0.33GPa achieved at the lowest
sintering temperature investigated. The decrease in hardness was attributed to the
structural degradation of diamond to non-diamond carbon forms with increase in
temperature as observed from Raman spectra of each of the composites. X-ray traces
showed an increase in the mullite content with increase in temperature. The fracture
toughness of compacts initially hot press sintered from alumina and silica in
stoichiometric composition for 3:2 mullite with no diamond added decreased with
increase in sintering temperature with 4.75 ± 0.10MPa·m1/2 achieved at the lowest
sintering temperature investigated. Further discussion to the structure and physical
properties is presented.
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Toughness-curve behavior of some alumina-mullite composites /Khan, Ajmal, January 1997 (has links)
Thesis (Ph. D.)--Lehigh University, 1998. / Includes vita. Includes bibliographical references (leaves 155-167).
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Simulation of Microwave Heating of Mullite RodsGoodson, Craig Carl 09 January 1998 (has links)
Microwave processing has been studied as an alternate heating technique over conventional heating for industrial applications. Some advantages include quicker and more uniform heating. Also, microwave energy offers the advantage of localized heating and smaller-sized equipment. Many ceramics, however, are difficult to heat using microwave energy by reason of the strong temperature dependence of the dielectric loss. The ability of a ceramic to absorb microwave energy, a measure of its dielectric loss, increases with temperature which makes the material more susceptible to thermal runaway. The purpose of this research is to develop a model that accurately reproduces experimental data and can be used to explore new applicator designs for continuous processing of such ceramics. A two-dimensional numerical model, created for this purpose, assumes that the ceramic is a circular cylinder that moves either longitudinally through a microwave cavity of given dimensions. By adjusting the electromagnetic field so that the absorbed power matches the measured power, the model successfully imitates experimental results and avoids thermal runaway while achieving high temperatures. / Master of Science
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A study of the sol-gel system for the preparation of mulliteOluwa, Omoyele A. 01 December 1996 (has links)
Sol-gel processing methods were used to prepare mullite ceramic powder form high purity aluminum tri-sec butoxide and tetraethylorthosilicate solutions under different processing conditions. the effects of the processing conditions on the sol to gel transition were examined by varying the water ratios, pH and temperature. Prehydrolysis of the silicon alkoxide was used since the aluminum alkoxide reacts faster than the silicon alkoxide. It was observed that the variation in temperature has the greatest effect on the time to gelation for the precursors. The rheological properties during the aging process indicated an increase in viscosity with age time, which is consistent with change in structure. Measurements of the viscoelastic properties during the sol to gel period showed a predominance of the loss (viscous) modulus over the storage (elastic)modulus in the initial stages of stages of aging. With increased aging of the sols and gels, large elastic components were observed which is consistent with structure build-up. The changes in structural evolution were followed by Fourier Transform Infra-red spectroscopy and correlated well to changes in the rheological properties of the sol. TG/DTA and X-ray analyses were used to correlate the starting chemistry and reaction condition to the microstructure of the final mullite powder. In all experimental cases fine grain mullite powder were obtained indicating no apparent differences of the synthesis conditions on the final mullite powder microstructure.
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