Porous ceramic monoliths based on diatomite Šaponjić, Aleksandra; Stanković, Miroslav; Majstorović, Jelena ...
Ceramics international,
09/2015, Letnik:
41, Številka:
8
Journal Article
Recenzirano
Porous silica ceramics were obtained at low forming pressure and low sintering temperature by using diatomaceous earth as a silica source and boric acid as an inexpensive additive. The starting raw ...material, diatomite from surface coal mine Kolubara, Serbia, was purified from organic and inorganic impurities by using heat and chemical treatment. Boric acid was used as binding and sintering aid up to 2wt%. Powder was compacted by using different pressures of 40, 60 and 80MPa. The pressed samples were sintered at 850, 1000, 1150, and 1300°C for 4h in air. A relatively high porosity in the range of 60–70% is obtained for the samples pressed at 40, 60 and 80MPa and sintered at 1000°C. Median pore size diameters are in the range of macroporous up to 2μm in the samples sintered at 1150 and 1300°C. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scaning electron microscopy (SEM) and mercury porosimetry measurements were employed to characterize the phases, functional groups, microstructure and pore size distribution of the obtained samples. In addition, measurements of densities and open porosities by immersion technique, according to Archimedes principle, were used. The relations between mechanical properties (Young modulus, Poisson ratio, and compressive strength) versus content of boric acid in the investigated samples were studied and disscussed.
The purpose of this study was to investigate behavior and degradation level of refractory concrete sintered at different temperatures during the thermal stability testing. Alumina based low cement ...castable was synthesized, cured, and then sintered at 1100, 1300, and 1600°C with dwell time of 3h. Prepared samples were subjected to the water quench test. Behavior of the refractory concrete and determination of surface and internal degradation level during the testing were monitored by ultrasonic measurements and image analysis. Overall material degradation was determined by measuring the strength degradation of samples using the standard laboratory procedure. The samples sintered at 1300°C showed the best behavior under thermal shock, since they withstood 110 cycles of water quench without breaking. It was evident that during the thermal shock, surface and interior of the samples sintered at 1600°C behave differently compared with those sintered at 1100 and 1300°C.
The analized material was high alumina low cement castable sintered at three
different temperatures. Influence of initial material anisotropy on the
thermal shock resistance as well as changes of ...anisotropy level during the
thermal shock were studied. Water quench test was used as an experimental
method for the thermal stability testing. Surface anisotropy was analysed by
image analysis and structural anisotropy using ultrasonic measurements. The
results pointed out that the highest homogeinity and the lowest surface and
structural anisotropy was for the samples sintered at 1600?C. Surface
anistoropy had prevailing infuence on behavior of material during the thermal
shock, but the structural anisotropy should not be neglected.
Macroporous silica ceramic was obtained using clay and diatomite. Boric acid
as a low-cost additive in the amount of 1 wt% was used. These porous
materials were obtained at low forming pressure ...(40-80 MPa) and lower
sintering temperature (850-1300 ?C) for 4h in air. The influence of boric
acid, forming pressure, and sintering temperature on the microstructure,
porosity parameters, and mechanical properties of obtained porous monoliths
were investigated. As-received and the modified samples were characterized
by X-ray diffraction, FTIR, SEM, and mercury porosimetry measurements. As
for modified clay and diatomite, they were pressed at 60 MPa and then
sintered at 1150 ?C, obtaining porosities of about 10 % and 60 %,
respectively. Both of the analyzed samples had the pore diameter in the
range of macroporous materials. The pore diameters of clay samples are
ranging from 0.1-10 ?m, whereas the pore diameter of diatomite samples was
slightly lower with values ranging from 0.05-5 ?m. Modified diatomite
samples have a lower Young modulus in comparison to modified clay samples.
Porous silica ceramics were obtained at low forming pressure (40–80MPa) and low sintering temperature (850–1300°C) for 4h in air. Boric acid was used as a low-cost additive, in the amount of 2wt%. ...Relatively high porosities of nearly 40% and 65% are obtained for the samples of clay and diatomite pressed at 40MPa, and sintered at 1000°C, respectively. The samples sintered at 1150°C and 1300°C have the average pore size diameters in the range of macroporous for clay 0.2–10μm and for diatomite 0.2–5μm. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mercury porosimetry measurements were employed to characterize of the obtained samples. Measurements of densities and open porosities by immersion technique were used, according to the Archimedes principle. The relations between mechanical characteristics of the samples formed by using different pressures and sintered at different temperature, were discussed.
Basalt as a filler in a polymer-based composite material fulfils the demand
of being natural, environment-friendly material for the production of
various composite materials. The material could be ...used as protective layer
and the abrasion should be tested in order to evaluate the properties of the
material. The cavitation test enables the evaluation of the possible service
in conditions that simulate the extensive erosion. The presence of basalt in
the matrix improves the resistance to cavitation. The possibility to further
improve the material could be obtained using the reinforcement of the matrix
itself by incorporation of submicron ceramic particles into the composite.
The obtained hybrid composite material with the addition of reinforcement in
the matrix further improves the cavitation resistance.
Al2O3-YAG composite was obtained by sintering of porous Al2O3 preforms
infiltrated with water solution of aluminium nitrate nonahydrate,
Al(NO3)3?9H2O and yttrium nitrate hexahydrate, Y(NO3)3?6H2O. ...Al2O3 preforms
with porosity varying from 26 to 50% were obtained after sintering at
temperature ranging from 1100 to 1500?C. Sintering of the infiltrated Al2O3
preforms led to formation of YAG particles due to reaction between Y2O3 and
Al2O3 at high temperature. It was found that variation of porosity of alumina
preforms and sintering temperature is an effective way to fabricate Al2O3-YAG
composite with an unusual combination of properties. Open porosity was in the
range 15-35%, specific surface was 0.6-6.1 m2/g, pore size was 150-900 nm
whereas compressive strength was from 50 to 250 MPa. The effect of sintering
temperature on YAG formation and phase composition were investigated using
X-ray diffractometry whereas microstructure of the composite was analysed by
scanning electron microscopy.
In this study, the behavior of glass-ceramics synthesized from a glass frit
of FFW (Final Flotation Waste) originated from the RTB Bor Company was
investigated. Thermal shock resistance was monitored ...in order to assess the
possibility of application of such waste material. Thermal shock of the
samples was conducted using water quench test. Image analysis and ultrasonic
measurements were used as nondestructive methods for quantification of
thermal shock damage at the surface and in the bulk of the specimens. Phase
composition of samples was determined by X-ray powder diffraction (XRPD). The
degradation level of samples was about 43 % after 20 cycles of water quench
tests. The results pointed out that glass-ceramic material exhibited good
thermal shock resistance.
Intention of this work was to obtain porous silicon dioxide ceramics by using boric acid as an inexpensive additive at low forming pressure and low sintering temperature. Starting raw material, ...smectite clay from surface coal mine Kolubara, Serbia, was purified from organic and inorganic impurities by using heat and chemical treatment. Boric acid was used as binding and sintering aid in amount of 0.5, 1 and 2wt%. Powder was compacted by using different pressures: 40, 60 and 80MPa. Pressed samples were sintered at 850, 1000, 1150, and 1300°C for 4h in air. A relatively high porosity of nearly 40% is obtained for the samples pressed at 40, 60 and 80MPa and sintered at 1000°C. Median pore size diameters are in the range of macroporous up to 0.2μm and 10μm in the samples sintered at 1150 and 1300°C, respectively. X-ray diffraction (XRD), scaning electron microscopy (SEM), and porosimetry measurements were employed to characterize the phases and microstructure of the obtained ceramics. The relations between mechanical characteristics of samples (Young modulus and Poisson ratio) and content of boric acid were studied.
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