1,721,006 research outputs found
The quantitative estimation of silica in rice husk ash by titrimetric method: A case study for uncertainty calculation
No full textSilicon is an essential element found in cereals, fruits, vegetables pasta, rice, etc. Rice husk ash is one of the most silica rich raw materials after complete combustion among the family of agro wastes. For the preparation of pure activated silica rice husk are now widely used as raw material. Rice husk ashes are now used by various industries for different applications due to its important properties. The exact quantity of silica in the rice husk ash is therefore essential to know before further research. Keeping these facts an attempt has been made to determine the silica content by titrimetric method followed by
quantification of uncertainty budget in four different variety of rice husk ash. The major sources of uncertainty in the measurement have been identified as contributions from repeatability, standardization of sodium hydroxide, titration, weight of the sample taken, volume measurement by volumetric flask, burette, pipette, weighing balance etc. All major sources of uncertainty have been identified and combined following the EURACHEM guidelines
Influence of fly ash and steam on microstructure, and mechanical properties of oxide bonded porous SiC ceramics
Full text linkCeramic filters specially SiC filters are used in advanced coal combustion and gasification processes to remove fine dust particles from the fuel gas at high temperatures and high pressure for protection of turbine blades and other downstream components from corrosion and erosion and to meet the environmental regulations. Processing of corrosion resistant porous SiC ceramics at low temperature using a simple technique is still challenging. In this study oxide bonded porous SiC ceramics were synthesized by cost effective method. The corrosion behaviour of SiC ceramic filter materials in presence of steam, coal ash and both coal ash and steam was investigated at 1000 degrees C for 96-240 h. The apparent changes in mass, porosity and density with corrosion duration and environment were recorded. Finally SEM, XRD and mechanical tests of the corroded samples were carried out. The corrosion test results indicated water vapour is the perpetrator for strength degradation. (C) 2019 SECV. Published by Elsevier Espana, S.L.U
Influence of clay content on microstructure and flexural strength of in situ reaction bonded porous SiC ceramics
No full textThe aim of the present study is to reveal the effects of clay contents on in situ reaction bonding of SiC, phase development, microstructure, porosity and mechanical properties of porous SiC ceramics. Porous silicon carbide (SiC) ceramics are prepared in air at 1400 degrees C for 1 h using alumina as bond phase additive and variable amount of clay as sintering aids and compared their properties. The ceramics prepared with only alumina additive obtained with flexural strength of 28 MPa at porosity 38 vol% without any characteristic peak for mullite. The mullitization was almost completed at 1400 degrees C with addition of 3 wt% clay. It was found that the addition of clay strongly promoted the phase transformation towards mullite at lower temperature. A high flexural strength of 72 MPa was achieved at porosity level of 33 vol% in the sample prepared with 5 wt% clay due to the enhancement of necks at the contacting points. (C) 2019 Elsevier Ltd. All rights reserved
Dispersion of SiC powder suspension in mullite sol and influence on properties of sintered ceramics
No full textThe dispersion behavior of SiC powders in various concentration of mullite sol was studied by zeta potential, rheological, and sedimentation measurements. Effect of pH, sol concentration, solid loading on the rheological properties are discussed in detail. The lowest viscosity and sedimentation was obtained for 45 wt% SiC powders dispersed in 15 wt% mullite sol, at pH similar to 2. The adsorption isotherms belong to Langmuir type and optimum concentration of mullite for maximum dispersion was found to be similar to 0.036 g/m(2). The stabilization mechanism of SiC powder into mullite precursor sol was explained by Derjaguin-Landau-Vervey-Overbeek (DLVO) theory. Coating was confirmed by transmittance electron microscopy and energy-dispersive X-ray spectroscopy analysis. Further sintering of the mullite-coated SiC powder compact at 1300 degrees C produced porous SiC ceramic with porosity similar to 40 vol% and pore diameter similar to 3 mu m. The corrosion behavior of the ceramics was studied in strong acid medium at 90 degrees C and compared with the ceramics obtained from uncoated SiC powder
Influence of additive contents on the properties of SiC ceramic membranes and their performance in oil-water separation
No full textThe high processing cost is the key challenge for the economic industrial use of SiC membrane The aim of this research was to fabricate mullite bonded porous SiC ceramic membrane at low temperature from novel combinations of fly ash and alumina (FA) in weight ratio 44.5:55.5 as sintering additives. The influences of FA and pore former content on the porosity, morphology, crystalline phase composition, mechanical performance, permeability properties were investigated. The membrane prepared at 1300 degrees C using 20 wt% FA showed pure water permeability 3690 Lm(-2)h(-1)bar(-1) and exhibited high oil removal efficiency of similar to 98% from the synthetic oil-water emulsion having oil concentration of 1000 mg/L. The corrosion behaviour of silicon carbide membrane in the strong acid and alkali solution and its mechanism were investigated. The utilization of fly ash successfully reduced the raw material cost and sintering temperature and the use of alumina reduced the amount of oxidation of SiC as well as increased the amount of mullite bond phase which resulted excellent mechanical strength to the final ceramics
Stepwise complexometric determination of aluminium, titanium and iron concentrations in silica sand and allied materials
Full text linkAbstract Background This study aimed at measuring the quantities of Al, Ti and Fe in silica sand and allied materials employing a complexometric method in the same analyte and a stepwise indirect titration with EDTA. The method involves the complexation of Al, Ti and Fe with excess EDTA and the selective de-complexation of TiO-EDTA and Al-EDTA complexes with tartaric acid and NaF respectively. In addition to its simplicity, rapidity and accuracy, the proposed method does not require the use of a separation technique or any sophisticated instrumentation. Results Each of the test samples were analyzed five times using the proposed method. The method's accuracy was confirmed by analyzing the US National Institute of Standards and Technology's (NIST) Standard Reference Materials (SRM) 81a, 89 and IPT SRM 61 using the procedure proposed, in addition to analyzing Ti and Fe levels by spectrophotometry and that of Al by complexometry. Conclusion The study shows that there is good agreement between the proposed and existing methods. The standard deviations of the measurements were calculated by analyzing five replicates of each sample, and were found to be less than 1.5% in our method.</p
Processing and properties of cordierite-silica bonded porous SiC ceramics
No full textCordierite-silica bonded porous SiC ceramics were fabricated by infiltrating a porous powder compact of SiC with cordierite sol followed by sintering at 1300-1400 degrees C in air. The porosity, average pore diameter and flexural strength of the ceramics varied 30-36 vol%, similar to 4-22 pm and similar to 13-38 MPa respectively with variation of sintering temperature and SiC particle sizes. In the final ceramics SiC particles were bonded by the oxidation derived SiO2 and sol-gel derived cordierite. The corrosion behaviour of sintered SiC ceramics was studied in acidic and alkaline medium. The porous SiC ceramics were observed to exhibit better corrosion resistance in acid solution
Properties and performance of cordierite-bonded porous silicon carbide membrane prepared using waste fly ash and other oxide additives
No full textThe low-cost cordierite-bonded porous SiC ceramic membranes were successfully synthesized at 1300 & DEG;C for 1 h in the air by in-situ solid-state reactions of SiC with a mixture of fly ash, & alpha;-Al2O3 and MgO (FAM). The effects of sintering temperature and FAM content on porosity, mechanical strength, phase compositions, microstructure and permeability were carefully investigated. The ceramics prepared at 1300 & DEG;C with a 20 wt% FAM mixture showed a very high mechanical strength of 85.8 MPa at a porosity of 28 vol%. The addition of pore former effectively improved the porosity and permeability properties without significantly degradation of mechanical strength. The membrane exhibited 98.4% oil removal efficiency from synthetic oil-water emulsion (1000 mg l(-1)), which suggests that the membranes are suitable for oil-water separation and other microfiltration applications. The use of fly ash successfully reduced the sintering temperature for the fabrication of ceramic membranes and provided an efficient way of utilizing waste resources
Thermal Shock Resistance of Porous Silicon Carbide Ceramics Prepared Using Clay and Alumina as Additives
No full textPorous silicon carbide ceramics were prepared by an in situ reaction bonding process using clay and alumina as additives. The effects of alumina additive, pore former on phase composition, microstructure, flexural strength and thermal shock resistance of the ceramics were studied. Thermal shock resistance of porous SiC ceramics due to cooling was evaluated as a function of quenching temperatures and quenching cycles using water- and air-quenching technique. It was observed that residual strength of the quenched samples in water decreased with increase in the quenching temperature but was almost independent of quenching cycles. In water quenching, the surface of the sample cooled almost instantly but the inside remained hot which created an uneven thermal profile and generated microcracks in the sample; as a result sudden reduction of flexural strength was observed. The results showed that flexural strength and thermal shock resistance properties of the ceramics prepared with alumina are better than those of the ceramics prepared without alumina and the material was found suitable for hot gas filtration application
Permeability and dust filtration behaviour of porous SiC ceramic candle filter
No full textPorous SiC candle filter (similar to 660 mm L and 75 mm OD) were fabricated by ramming process using commercially available SiC powder (d(50) = 212 mu m), with and without alumina and small amount (3 wt %) of clay as the major binder phase additives, following heat treatment at 1400 degrees C in air. Depending on the composition, porosity of the candle filters varied from 36 to 39 vol% and C-ring strength varied from 15 to 23 MPa. The air permeability and dust filtration efficiency of the candle filter were evaluated using laboratory made test set up. At room temperature, Darcian (k(1)) and non-Darcian (k(2)) permeability parameters varied from 1.9 to 2.2 x 10(-12) m(2) and 5.4-9.72 x 10(-8) m, respectively. Airborne fly ash particle filtration tests showed good performance of SiC candle filter with filtration efficiency of >97%. (C) 2020 Elsevier Ltd. All rights reserved
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