Ritwik Sarkar

Effect of addition of pond ash and fly ash on properties of ash-clay burnt bricks

Two industrial solid waste products generated by Indian coal-fired power plants, namely pond ash and fly ash, were used in combination with local clay to develop building bricks. The clay were mixed with the two different ashes in the range 10 to 90 wt.%, hydraulically pressed and fired at 1000°C. The fired products were characterized for various quality properties required for building bricks. The properties of the optimal compositions were compared with conventional red clay bricks including the developed microstructures and the comparative study generally showed that te ash-clay bricks were of superior quality to the conventional products.

Study on the Development of Machinable Hydroxyapatite - Yttrium Phosphate Composite for Biomedical Applications

Hydroxyapatite (HAp) and yttrium phosphate (YP) powders were synthesized through wet chemical route and calcination process. Calcined powders were used to prepare HAp-YP composites by solid mixing and sintering route, up to a YP content of 50 wt%. Sintered composites were characterized for phase analysis and densification study. The sintered composites were studied for machinability by drilling method using a conventional cemented carbide drill bit. Hydroxyapatite-yttrium phosphate composite pellets were studied for drilling by conventional drilling technique using carbide drill bits. In vitro cytotoxicity study of the sintered composites, using MTT assay by culturing in MG-63 cells, showed cell viability index >0.95.

Nano carbon containing low carbon magnesia carbon refractory: an overview

Steel manufacturing technology has changed drastically in last few decades to meet the demand of high purity and quality of steel from the steel users. The advancements in steel making process have also demanded high quality refractories to withstand severe operating conditions and to produce desired steel quality. Magnesia carbon refractories, being essential for making and processing of steel, have gone through many modifications since its inception and still are one of the major challenging areas for refractories development. Only a few years ago higher use of carbon was assumed to be beneficial for the refractories performances and life but the concept has been proven wrong and low carbon containing MgO-C refractories are becoming the point of attention. Reduction in carbon content in MgO-C refractories without much affecting their properties have been tried by many ways by many researchers, amongst them use of nano carbon is widely popular. This review discusses the prospects for using nano carbons in MgO-C refractory and various research works that are going on and also on the development of low carbon containing magnesia carbon refractories.

High Alumina Castables: Effect of Alumina Sols and Distribution Coefficients

Two different alumina sols were prepared using different precursor sources and the sols were solely used as binder in no cement high alumina castable. The sols were characterized for their solid content, pH, particle size, zeta potential, thermal behaviour through DSC-TG, phase formation on calcination, etc. The sols were used as sole binder in high alumina castables with different particle size distribution, as per Dinger and Funk model, to attain different flow consistency. The castables were processed conventionally and heat treated at three different temperatures. Different physical and mechanical properties were evaluated and compared. Sol prepared from nitrate precursor resulted in better properties when used as binder in castables as compared to that prepared from commercially available boehmite powder. No deformation in the castables was observed on firing at 1650oC, much above the application temperature of any cement/ sol bonded castables. Absence of any component other than alumina nullifies any eutectic or liquid phase formation in the system.

Lanthanum Phosphate Containing Machinable Alumina Ceramics for Bio-Medical Applications

Alumina-lanthanum phosphate composites were prepared using two commercial grade aluminas and synthetically prepared lanthanum phosphate. Composites were prepared by varying lanthanum phosphate content between 10 and 50 wt%. Mixed composites were pressed and sintered between 1400° and 1600°C. Sintered products were characterized for various properties including microstructure, machinability and bioactivity. Phase analysis confirmed separate existence of Al2O3 and LaPO4 phase’s different sintering temperatures. Sintering temperatures and lanthanum phosphate content were found to be important for the incorporation of machinability property in alumina. Bioactivity study indicated growth of apatite on immersing the samples in simulated body fluid for 7 days.

Synthesis and characterization of sintered beta-tricalcium phosphate: A comparative study on the effect of preparation route

Beta-tricalcium phosphate (β-TCP) was prepared by three different routes namely, wet chemical coprecipitation, sol-gel and solution combustion synthesis. The synthesized powders were calcined at different temperatures and characterized for phase evolution study, thermal analysis, Fourier transform infrared (FTIR) spectroscopy, microstructural study for comparative analysis. The optimal thermal treatment required to prepare pure β-TCP powders was determined and after calcination of the synthesize powders prepared by different routes, pure β-TCP was obtained. The sintering temperature required to prepare fully dense β-TCP completely free from α-form was identified. The powders were then used to make dense and compact bodies sintered at 1200 and 1250°C. The sintering behaviour of the dense bodies was analysed using dilatometry, densification and microstructural study. It was found that the pellet prepared from powder synthesized via co-precipitation route attained maximum density compared to the pellets prepared from powders synthesized via sol-gel and solution combustion route.

Study on variation of graphite content in N220 nanocarbon containing low carbon MgO–C refractory

The effect of variation in flaky graphite content from 1 to 5 wt-% was studied in 1 wt-% N220 nanocarbon containing MgO–C refractories. Low carbon MgO–C refractory compositions were prepared by conventional manufacturing techniques, and products were characterised for various refractory related physical, mechanical, corrosion, phase analysis and microstructural studies. All the low carbon compositions were also compared against 16 wt-% flaky graphite containing conventional MgO–C refractory, without any nanocarbon, prepared under similar manufacturing conditions. Graphite (3 wt-%) with 1 wt-% nanocarbon containing composition resulted in better density and strength values, and 5 wt-% graphite with 1 wt-% nanocarbon containing composition showed better hot strength and corrosion resistance.

Effect of LaPO4 Content on the Machinability, Microstructure and Biological Properties of Al2O3

Synthesized LaPO4 was mixed with calcined alumina at 10, 20, 30, 40 and 50 mass-%, and the mixed compositions were pressed and sintered at 1500, 1550 and 1600°C. Sintered products were analyzed for phase analysis, machinability (drilling by conventional tools) microstructure and biocompatibility studies. No reaction between the reactants was found and sintered compositions showed a composite character. Addition of LaPO4 was found to impart machinability in alumina ceramics. A good distribution of LaPO4 particles was observed in the microstructure. A positive response was observed for the sintered composites in bioactivity (immersion in SBF solution) and in vitro biocompatibility (cytotoxicity study) tests.

Reactive alumina–LaPO4 composite as machinable bioceramics

Sintered Al2O3–LaPO4 composites were prepared using commercially available reactive alumina and phase pure lanthanum phosphate (LP), prepared by the reaction synthesis technique. LP content was varied between 10 and 50 wt% and sintering was carried out between 1400 and 1600 ∘C. Sintered composites were characterized for phase analysis, densification, strength, machinability, microstructure and bioactivity (in SBF solution) and biocompatibility (MTT assay protocol) studies. Composite nature was confirmed by phase analysis and LP was found to reduce the densification and strength values but imparted machinability. Again positive bioactivity and biocompatibility character were observed for all the compositions.

Fibre Reinforced No Cement Self Flow High Alumina Castable: A Study

Effect of addition of steel fibre on self flow high alumina castable has been studied up to a fibre content of 4 wt%. Self flowing characteristics of this gel bonded castable were found to be unaffected in the presence of steel fibres. Density and strength properties were found to be improved significantly in presence of fibres. A maximum density of 2.93 g.cm−3 was obtained with up to 70% increase in crushing strength and about 4 times improvement in bending strength compared to those in a body containing no fibre. Uniform distribution of the fibres in cast samples is the reason for such betterment.