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Trans. Ind. Ceram. Soc.,  65 (1) 1-16 (2006).

© 2006 The Indian Ceramic Society

Magnetoresistivity in Solids

Dipten Bhattacharya

Electroceramics Division

Central Glass and Ceramic Research Institute

Kolkata – 700 032 

The phenomenon of magnetoresistivity is known since the days of Michael Faraday when he observed nearly 1-2% change in electrical resistivity under a magnetic field in glassy materials. Over the years, while new materials with varying degrees of magnetoresistivity have been developed, the quest for unearthing the mechanism, side by side, led to the formulation of new theories for more complex materials with complicated electronic band structure courtsey local magnetic interaction and strong correlation. Following Kramer’s concept of indirect magnetic exchange interaction, the formulation of double exchange interaction theory in the 1950s, by Zener, Anderson, and de Gennes, created a perspective for analyzing the correlation between metallic charge conduction and ferromagnetism and hence a sizable magnetoresistivity – observed in a series of transition metal oxides with different crystallographic structures. During the last one and a half decade, a series of unusual and unexpected observations have been made in different compounds – (a) giant negative magnetoresistivity in magnetic multilayers, (b) even higher and therefore colossal magnetoresistivity in single phase doped LaMnO₃ based compounds, (c) melting of a certain charge state under a magnetic field, (d) magnetic field driven structural phase transition and a large change in resistivity thereby, to name just a few. This review discusses the traditional concepts starting from classical Hall effect to domain boundary interaction to Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism and places the more recent developments against the backdrop of old concepts. It also looks beyond double exchange plus Jahn-Teller effect into the modern theory of finer scale intrinsic phase separation and percolation conduction as the most probable scenario for describing the magnetoresistivity in various transition metal oxides. The limited application potential of magnetoresistivity seems to have now become unlimited with the jump in the magnitude of magnetoresistivity. This review presents a few glimpses of new possibilities and future scopes.

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Trans. Ind. Ceram. Soc.,  65 (1) 17-21 (2006).

© 2006 The Indian Ceramic Society

Effect of Calcia on the Densification and Mechanical Properties of Sol-Gel Alumina

K. Vishista and F. D. Gnanam

 Department of Physics

Anna University

Chennai – 600 025

 Boehmite sol was prepared by hot water hydrolysis of aluminium iso-propoxide using nitric acid as the catalyst. Calcium nitrate to yield 5 to 20 vol% of calcium oxide was added to the boehmite sol. The sol was precipitated in ammonia, dried at 120°C and calcined at 500°C for 3 h. The calcined powder was milled at 230 rpm for 6 h. The powder was compacted into cylindrical pellets using a uni-axial press at 180 MPa and sintered at temperatures ranging from 1400° to 1600°C for 6 h. Mechanical properties such as hardness, fracture toughness and diametrical tensile strength for compacts containing variable amounts of calcium oxide were studied. There was a slight decrease in the density and hardness with increase in calcia content. Increase in the mechanical properties such as fracture toughness, flexural strength and diametrical tensile strength was observed with increase in calcia content.

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 Trans. Ind. Ceram. Soc.,  65 (1) 23-28 (2006).

© 2006 The Indian Ceramic Society

Microcellular Si/SiC Ceramics by Replication

of Indian Dicotyledonous Woods

O. P. Chakrabarti, D. Mallick, H. S. Maiti and R. Majumdar

 Central Glass and Ceramic Research Institute

Kolkata – 700 032

Three dicotyledonous woods of local origin (mango (Mangifera indica), jackfruit (Artocarpus integrifolia) and teak (Tectona grandis)) were transformed by pyrolysis into carbonaceous preforms and subsequently converted into microcellular Si/SiC ceramics by liquid Si-infiltration under vacuum. The pyrolyzed mango, jackfruit and teak were characterized in terms of pyrolysis  weight  loss,  shrinkages, bulk density  and microstructures. The end ceramics were found to be 91-98% dense with respect to theoretical densities (T.D.) with porosities in the range of 0.1-4.8%. SEM (in back scattered electron (BSE) mode) imaging confirmed the preservation of microcellular tissue anatomy of the precursor wood structure in the morphologies of the final ceramics. The microcellular Si/SiC ceramics from mango, jackfruit and teak exhibited excellent oxidation resistance during heating to 1350^oC in flowing air, showing a marginal weight gain at the highest temperature. Si/SiC-mango was also characterized in terms of flexural strength, Young’s modulus and hardness. These biostructural microcellular Si/SiC ceramics possess application potential in various structural ceramic sectors (e.g. mechanical pump seals, wear inserts, kiln support structures, heat exchangers etc).

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Trans. Ind. Ceram. Soc.,  65 (1) 29-33 (2006).

© 2006 The Indian Ceramic Society

Characterization of Porous Titania and Ceria Ceramics

by Small-Angle Neutron Scattering 

A. K. Patra, S. Ramanathan, D. Sen and S. Mazumder 

Solid State Physics Division

Bhabha Atomic Research Centre, Trombay

Mumbai – 400 085

Titania powder was prepared by a solution based hydroxide precipitation technique using the tetrachloride precursor and ammonia as the precipitating agent. Ceria powder was prepared by homogeneous precipitation method using cerium nitrate and hexamethylenetetramine. The particle size distribution of titania and ceria powders was measured by laser light scattering. The powder particles were found to follow a log-normal size distribution and the average size of the particles for both the powders was ~0.7 microns. Small-angle neutron scattering (SANS) was used to study the sintering behaviour and evolution of pore morphology in sintered compacts of titania and ceria by varying the sintering temperature / time. The SANS profiles were analyzed in the light of poly-disperse spherical pore model using log-normal size distribution. The pore sizes in both the ceramic compacts varied from 10 to 1000 nm and the mean value of the distribution shifted from a lower, 50 nm to a higher, 350 nm size. This trend could be attributed to both densification and grain growth occurring in the compacts with the progress of sintering.

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Trans. Ind. Ceram. Soc.,  65 (1) 35-40 (2006).

© 2006 The Indian Ceramic Society

Elastic Constants of Interpenetrating Phase

Alumina / Aluminium Composites

 Sujit K. Roy and Samir K. Ghosh 

Central Glass and Ceramic Research Institute

Kolkata – 700 032

Dense, pore-free interpenetrating phase Al₂O₃ / Al composites were synthesized by a condensed phase displacement reaction between silica and aluminium, and their elastic costants were determined by an ultrasonic technique. Comparisons are made between the experimental data and analytical theoretical models of Voigt-Reuss (V-R) and Hashin-Shtrikman (H-S). Young^,s modulus of these composites obey both the V-R and H-S bounds but is better predicted by the Hashin-Shtrikman model. The H-S bounds for the bulk and shear moduli are very narrow and the experimental values are close to the limit calculated on the basis of alumina as the matrix phase. The microstructural features of these composites, namely, a limited variation in the phase content and somewhat larger range of contiguity values seem not to have any significant influence on the elastic behaviour of the composites. Poisson^,s ratio is essentially constant in these composites. Within a small range of phase composition used in this study, it can still be deduced from the results that the contiguity of the Al₂O₃ phase influences the elastic properties to an extent.

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Trans. Ind. Ceram. Soc.,  65 (1) 41-48 (2006).

© 2006 The Indian Ceramic Society

Effect of Polyvinyl Pyrrolidone on Strength

and Some Other Properties of Cement

 V. K. Singh and R. K. Singh 

Dept of Ceramic Engineering

Banaras Hindu University, IT

Varanasi – 221 005

The effect of polyvinyl pyrrolidone (PVP) addition in the ordinary cement and mortar mixes on the properties such as setting time, heat of hydration, compressive and tensile strength has been studied by adding 0.5 to 5.0% additive by weight of cement. Hardness has been determined using the Vickers indentation method and the fracture toughness of cementitious bond and flexural strengths have been determined using three point bending system. Corrosion resistance of resulting products has been tested against each of 0.1 N and 1.0 N of HCl and H₂SO₄ and seawater. FTIR and X-ray diffraction techniques have been employed to determine the phase compositions of the material. The polymeric phase is interspersed in cement and causes decrease in water absorption; also its interaction with hydrating cement phases results in the additional bond formation, leading to the increase in strength.

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Trans. Ind. Ceram. Soc.,  65 (1) 49-55 (2006).

© 2006 The Indian Ceramic Society

New Generation Binders for Refractories

and Ceramic Industries 

S. D. Majumdar and A. K. Kaviraj 

H & R Johnson (India) Ltd

“Windsor” (7th Floor)

C. S. T. Road, Kalina, Santacruz (East)

Mumbai – 400 098

In recent years, process changes that have taken place in refractories as well as ceramic industries call for use of materials which can sustain stringent conditions and provide increased life during use at minimum cost. Introduction of higher grade of special binders with the existing grade of raw materials may be a possible solution. Work has been carried out successfully to develop a number of binders, namely, calcium dialuminate cement, barium aluminate cement, magnesia based cement and develop applications of these binders along with siliceous sol, aluminium hydrate, etc. In this paper, an attempt has been made to detail out the characteristics of these new binders, improved properties obtained from the finished products after their application and finally the effect of the same in the performance.

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Trans. Ind. Ceram. Soc.,  65 (2) 81-95 (2006).

© 2006 The Indian Ceramic Society

Refractories : A Comprehensive Report

 Subrata Banerjee

Answer  Technology Inc

1879 Jahns Drive, Wheaton

Illinois – 60187-8480 (USA)

Refractories are part and parcel of modern civilization. It is the most essential ingredient of all high temperature processes such as producing metals, glass etc. Significant developments have taken place in recent decades which have somewhat revolutionized the industry including the products and applications. In shaped refractories, preformed shapes ­– in machine shaped or cast forms ­– are used in significant amounts other than typical bricks. The unshaped refractories, commonly known as monolithic refractories, have taken a significant leap both in terms of materials, products and applications. In this paper, most of the various types of refractories will be dealt with respect to their compositions, manufacturing and applications.

A special separate section is dedicated towards the development and use of alumina-magnesia spinel high fired steel ladle well blocks and in situ cast steel ladle bottoms, since it has provided a significant improvement in the life of the ladle, particularly the well block and the bottom.

This paper will deal with the science and technology of refractories only and not the commercial aspects.

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 Trans. Ind. Ceram. Soc.,  65 (2) 97-99 (2006).

© 2006 The Indian Ceramic Society

A Study on the Solubility Limit of Nd₂O₃

in ThO₂-NdO_1.5 Solid Solution

G. Panneerselvam, M. P. Antony and P.R Vasudeva Rao 

Chemistry Group

Indira Gandhi Centre for Atomic Research

Kalpakkam – 603 102

Thorium dioxide dissolves considerable amounts of rare earth oxides forming FCC fluorite-type solid solution. In the present study a series of solid solutions containing NdO_1.5 in ThO₂ were prepared by co-precipitation method. These solid solutions were characterized for their composition by standard wet-chemical analysis. Their bulk and theoretical densities were determined by immersion and X-ray techniques respectively. The extent of solubility of NdO_1.5 in ThO₂ matrix was determined using powder X-ray diffraction at 1473 K. The measured solubility of NdO_1.5 was found to be in the range 45.7 to 46.2 mol%.

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Trans. Ind. Ceram. Soc.,  65 (2) 101-104 (2006).

© 2006 The Indian Ceramic Society

Electrical Discharge Machining of Sintered Ni₃Al

 A. K. Khanra and M. M. Godkhindi 

Dept of Metallurgical and Materials Engineering

Indian Institute of Technology

Kharagpur – 721 302

The electrical discharge machining (EDM) behaviour of sintered Ni₃Al was carried out with different process variables. The metal removal rates were found to increase with the applied current and pulse on-time. The surface roughness of Ni₃Al increased with pulse on-time. Cracks were formed on Ni₃Al surface during the EDM operation due to generation of high thermal stress. No phase changes were found on the machined surface due to the EDM operation. The debris analysis showed solidification of liquid materials into non-crystalline spheres.

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Trans. Ind. Ceram. Soc.,  65 (2) 105-110 (2006).

© 2006 The Indian Ceramic Society

 Aluminium Oxide Coating by Microwave Processing

Sumana Das, Anup Kumar Mukhopadhyay, Someswar Datta and Debabrata Basu

Central Glass and Ceramic Research Institute

Kolkata – 700 032

Microwave processing is an energy-efficient advanced technique to prepare materials with finer microstructure and better mechanical properties. In the present paper, microwave energy was utilized for the development of oxide coatings on blocks of commercial aluminium of various geometrical shapes. Experimental results revealed that the geometrical term, i.e. the volume to surface ratio had a dominant influence on the microwave induced oxidation behaviour of the samples. In all the cases, coating thickness and its density progressively increased with increasing microwave exposure time. The coating phase was found out to be a-Al₂O₃ by XRD analysis. The coating microstructure and elemental analysis as examined by SEM and EDAX respectively have been discussed in detail. Adhesion of coatings was studied by using the scratch test.

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Trans. Ind. Ceram. Soc.,  65 (2) 111-114 (2006).

© 2006 The Indian Ceramic Society

 Introduction of Advance Lining System for

Tundish at Durgapur Steel Plant

 P. K. Roy Choudhury, D. Halder, R. K. Ahuja, S. Sarkar, K. Patwari,

B. D. Chattoraj, A. Majumdar and P. Dutta

 Refractories Division

Research and Development Centre for Iron and Steel (SAIL)

Ranchi – 834 002

Developments in the continuous casting of steel have put increased demands on the refractories used in the tundish. Tundish working lining systems are required to provide the steel maker with a clean steel practice over a reasonably longer sequence, proper insulation, wear resistance, flow control and easy deskulling. In order to achieve these objectives, the tundish lining material also advanced significantly. The present practice of using silica board as cold tundish working lining material in Durgapur Steel Plant has some limitations in the aforesaid requirements.

This paper deals with a “dry tundish working lining system” which allows the steel maker to produce cleaner steel. This material contains around 80% MgO and resinous bond. This bond is activated at relatively low temperature (250°-300°C) to generate sufficient strength. The thickness of the working lining varies between 40 and 60 mm depending on tundish size and sequence length. Dry tundish working lining can be used replacing SiO₂ or MgO boards in cold tundish practice. In addition, the other components of the tundish working lining, e.g. impact pads/turbo-inhibitors, metering nozzles, dams are also looked into to match the higher sequence length. The system has been proven as a cost effective refractory solution for long multiple sequence casts.

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Trans. Ind. Ceram. Soc.,  65 (2) 115-119 (2006).

© 2006 The Indian Ceramic Society

The Present Scenario of Non-Recovery

Coke Ovens in India and Development

of New Refractory Technology

 S. N. Laha

Natasha Ceramic and Consultancy Services

P-36, Motijheel Avenue, Dumdum

Kolkata – 700 074

The present status of coke making through the use of non-recovery coke ovens (NRCO) has been described. The main features and key characteristics of this type of oven have also been highlighted. The author’s own contribution in development of innovative refractory technology for improved performance of this type of coke oven has also been elucidated.

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Trans. Ind. Ceram. Soc.,  65 (3) 129-144 (2006).

© 2006 The Indian Ceramic Society

Microwave Sintering of Ceramics, Composites and

Metallic Materials, and Melting of Glasses

 Dinesh Agrawal 

Microwave Processing and Engineering Center 

107 Materials Research Laboratory

The Pennsylvania State University 

University Park, PA 16802, USA

Though microwaves have been in use for many applications for over 60 years, their application in ceramic processing involving synthesis, sintering, melting, joining, surface modifications, etc, has developed only in the last twenty years. Microwave materials processing is recognized for many advantages, namely, substantial reduction in cycle time resulting in large energy savings, selective and volumetric heating, providing fine microstructures, improved mechanical properties, and eco-friendliness. In the last two decades, various researchers have worked with a variety of traditional and advanced ceramics such as alumina, zirconia, hydroxyapatites, transparent ceramics, electroceramics, ceramic superconductors, glass-ceramics, non-oxide ceramics including Si₃N₄, AlN, SiC and WC/Co, etc. In all of these materials, substantial improvements in their properties over conventional products, as well as enhancements in the diffusion and reaction kinetics, were reported. Recently, microwave melting of glasses has also been achieved with many advantages over conventional melting.

It was generally believed that metals reflect microwaves, and hence cannot be processed in a microwave field like ceramics. However, recently it has been discovered that if the metals are in powder form, they will also absorb microwaves and will get heated very effectively. Almost all metals, including refractory metals (W, Re, Mo, etc), alloys, steels, have now been sintered successfully in 5-15 min. The selective heating feature of microwaves has led to effective brazing and joining of metal parts. Even bulk metals can be heated and melted in a microwave field and the melt can be cast into useful products.

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Trans. Ind. Ceram. Soc.,  65 (3) 145-156 (2006).

© 2006 The Indian Ceramic Society

High Temperature Deformation Behaviour of a

High Purity Al₂O₃ Reinforced with Isolated Second Phases of Spinel (MgAl₂O₄), YAG (Y₃Al₅O₁₂) and Zirconia (t-ZrO₂)

 L. N. Satapathy

 Ceramic Technological Institute

Bharat Heavy Electricals Limited

Bangalore – 560 012

High temperature compression experiments were carried out on high purity alumina based composites containing second phases of spinel (MgAl₂O₄), YAG (yttrium aluminium garnet, Y₃Al₅O₁₂) and zirconia (t-ZrO₂) at a temperature range of 1623-1723 K, stress range of 10-200 MPa and a grain size range of ~1-10 µm. It was observed that 5 vol% of these second phases had no significant influence on the creep rate of alumina. The stress exponent of ~1.0 and the inverse grain size exponent of ~3.0 suggested no change in the creep mechanism of pure alumina with 5% second phase addition. Deformation enhanced grain growth, which was prominent in pure alumina, was not observed in the composites. The creep behaviour of the composites was discussed based on ionic radii and ionic charge, room temperature mechanical properties and grain size of individual phases. A new model was developed which took into account the creep rate of the second phase while calculating the creep rate of the composite.

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Trans. Ind. Ceram. Soc.,  65 (3) 157-164 (2006).

© 2006 The Indian Ceramic Society

 Rheological Behaviour and Thermo-Mechanical

Evaluation of Vitreous Sanitaryware Compositions

Containing Fired Sanitary Scrap

 P. Agrawal and K. N. Maiti

 Central Glass and Ceramic Research Institute

Naroda Centre, Naroda Industrial Estate

Ahmedabad – 382 330

Fired sanitary scrap after fine grinding has been incorporated in a standard vitreous sanitaryware body and the influence of its addition on the rheological and thermo-mechanical properties, vitrification behaviour and microstructure has been investigated. The incorporation of 5-10 wt% scrap resulted in about 8% increase in flexural strength, reduction in vitrification temperature by ~30°C and broadening of vitrification range of body by 40° to 90°C. This has also resulted in significant improvement of rheological properties of the casting slip at a reduced electrolyte demand without altering the unfired strength of body mixes.

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Trans. Ind. Ceram. Soc.,  65 (3) 165-167 (2006).

© 2006 The Indian Ceramic Society

Deflocculating Effect of Sodium Polymethacrylates

on Aqueous Clay Suspensions

 S. Sakthivelu, P. Manohar, V. Ramamurthi and M. Balasubramaniam

 Dept of Ceramic Technology

Alagappa College of Technology, Anna University

Chennai – 600 025 

The ability of sodium polymethacrylates salts with various molecular weights (1200 to 30000) to deflocculate concentrated aqueous suspensions (56 wt%) of two Indian ball clays was investigated. The ball clays were one from Bikaner, Rajasthan and the other from Bhimandole, Andhra Pradesh, which are widely used in Indian sanitaryware and tile industry. The clays were characterized for their chemical analysis, cation exchange capacity (methylene blue index test) and for particle size distribution. The clay slips were prepared with distilled water and water containing calcium ions (0 to 60 ppm) using sodium polymethacrylates as deflocculant. All the slurries showed non-Newtonian behaviour. Polymethacrylates with low molecular weights (1200 to 2500) were found to be the most efficient deflocculants for these clay suspensions. The salts acted by an essentially electrosteric stabilization mechanism in combination with a high sequestering ability towards flocculating cations (calcium ion binding power values of 760 to 790 mg_CaCO3.g^–1). For their efficient deflocculating capabilities towards concentrated clay suspensions, sodium polymethacrylates may be considered for practical industrial application, in particular, for the preparation of liquid deflocculants.

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Trans. Ind. Ceram. Soc.,  65 (3) 169-172 (2006).

© 2006 The Indian Ceramic Society

Determination of Trace Impurities in Silica Sand

by Inductively Coupled Plasma

Atomic Emission Spectrometry

 S. S. Mukhopadhyay and Dipali Kundu

 Analytical Chemistry Section

Central Glass and Ceramic Research Institute

Kolkata – 700 032

Determination of trace impurities in silica sand is simplified by the introduction of automated inductively coupled plasma atomic emission spectrometer (ICP AES). Due to high sensitivity and wide linear concentration range most of the elements are possible to be determined directly using ICP AES in one sample solution. The instrument has been optimized using silica sand matrix considering radio frequency (RF) power, nebulizer pressure, auxiliary flow rate and pump speed. A multielement programme for trace impurity analysis of silica sand has been developed. The accuracy of overall analysis was first estimated by the analysis of three certified reference materials, and good agreement between measured and reference values has been found for all the elements. As the second way of determining accuracy, results obtained from independent analytical techniques ICP AES and AAS have been compared by analyzing real samples.

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Trans. Ind. Ceram. Soc.,  65 (4) 179-196 (2006).

© 2006 The Indian Ceramic Society

Review on Monolithic Ceramic Catalysts in Different Applications: Support Materials, Incorporation Techniques and Physical Properties

 Sudipta Chattopadhyay

 Catacel Corporation

Ohio-44231, USA

A broad spectrum of the fundamental principles of ceramic monoliths as supports in different applications based on catalytic reactions is presented in this review. Importance of selecting right ceramic structure, carrier materials etc has been discussed in detail focusing on several major studies performed since ’50s till date. The large array of preparation technology using various incorporation techniques of active phase on the support meeting suitable characteristics of a good monolithic catalyst has also been illustrated at length. The choice of a suitable ceramic catalyst for a particular application strongly depends on emphasizing the physical properties of the catalyst, i.e. active surface area, adhesion properties, pore volume and particle size. The significance of these properties have also been reviewed in this article. Ceramic monoliths are especially well-known due to their cost-effectiveness, low pressure drop and requisite high mechanical strength for the long run harsh conditions encountered in environmental applications. Several emerging applications especially in gas phase catalytic reactions are discussed briefly, emphasizing on the implication of ceramic catalysts in hydrogen production and fuel cell technology, the main debate in alternative energy nowadays.

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Trans. Ind. Ceram. Soc.,  65 (4) 197-201 (2006).

© 2006 The Indian Ceramic Society 

Influence of Kaolinitic Clay on the Physico-Mechanical Properties of Common Clay-Fly Ash Mix

for Building Bricks

Syamal Ghosh, T. K. Mukhopadhyay, S. Chakrabarti and S. K. Das

 Central Glass and Ceramic Research Institute

Kolkata – 700 032

Kaolinitic clays of different varieties were progressively added to a 70 : 30 mix of common clay and fly ash. The improvement in physico-mechanical properties upon heating in the temperature range of 1050° to 1200°C was studied by evaluating their linear shrinkage, water absorption, flexural strength and phase content. Incorporation of clay I produced better ceramic properties than that of clay II. It was observed that incorporation of kaolinitic clay up to 10% of the total batch improved the physico-mechanical properties and beyond this limit the properties, particularly fired strength, remained unchanged or marginally decreased. Microstructural features were also studied using SEM technique.

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Trans. Ind. Ceram. Soc.,  65 (4) 203-209 (2006).

© 2006 The Indian Ceramic Society

Comparison between Capillary Suction Time (CST) and Flow Point Measurements for Determination of Highest Achievable Solids Loading in Ceramic Slurries

 Bimal P. Singh, Ruben Menchavez, Tamura Aya, Masayoshi Fuji and Minoru Takahashi

 Colloids and Materials Chemistry Division

Regional Research Laboratory

Bhubaneswar – 751 013

This paper presents the comparison of two different techniques, namely, capillary suction time (CST) and flow point measurements for determination of maximum achievable solids loading in slurries. Good agreement was observed between the two techniques for Al₂O₃ and Y₂O₃. The shift in isoelectric points (iep) of the powders in presence of a dispersant was determined through zeta potential measurements on dilute suspensions. Specific free energy of interaction between oxides and dispersants was also calculated by using a model based on the electrical double layer theory of surfactant adsorption through shift in isoelectric points. The specific free energy of interaction was found to be higher for Al₂O₃ (–DG°_SP = 7.5016) compared to Y₂O₃ (–DG°_SP= 6.856), suggesting greater electrical double layer repulsion and hence, better dispersion and solids loading. It has been concluded that the measurement of CST and flow point are two simple but useful techniques for rapid evaluation of a required amount of dispersant for making any flowable suspension with maximum solids loading.

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Trans. Ind. Ceram. Soc.,  65 (4) 211-214 (2006).

© 2006 The Indian Ceramic Society

Effect of Grinding on De-Hydroxylation

Behaviour of Diaspore

 S. Sakthivelu, P. Manohar, V. Ramamurthi and M. Balasubramaniam

 Dept of Applied Science and Humanities

Madras Institute of Technology, Anna University

Chennai – 600 025

The natural diaspore from Jhansi, India was ground in a pot mill in different conditions (dry and wet). The wet grinding was carried out in different media (acidic, basic and neutral) and with deflocculated aqueous diaspore suspension (60 wt%). The sodium polymethacrylate salt (mol. wt. 1200 g.mol^–1) was used as the dispersant. The range of particle size of diaspore at which a limit of the grindability exists was also investigated. The effect of grinding on the thermal behaviour of dehydration and a-transformation was examined by means of differential thermal analysis (DTA), thermogravimetry (TG) techniques.

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 Trans. Ind. Ceram. Soc.,  65 (4) 215-221 (2006).

© 2006 The Indian Ceramic Society

DMAIC Approach in Rural Technology —

An Application to Making of Water Filters

V. C. S. Prasad and Vivek Ganvir

 Tata Research Development and Design Center

54B , Hadapsar Industrial Estate

Pune – 411 004

Development of appropriate specifications for low cost technologies is not often done in a rigorous manner. This paper presents the use of systematic DMAIC methodology (Define, Measure, Analyze, Improve and Control) for arriving at practical specifications for the bacterial (E.coli) trapping level in a low cost water filter meant for rural needs in India. This filter is based upon a materials-based invention, viz. the use of the waste material, rice husk ash as a filtration medium to achieve near 99% trapping efficiency of E.coli bacteria. In actual practice, however, the filtered water shows substantial variation in bacterial levels when filters are produced in significant numbers. This variation is reduced to safe limits through systematic application of the DMAIC methodology. When the filters made by the villagers from the resulting process were introduced in a small village in India, significant reduction in the number of cases of water-borne diseases was reported. Since the materials on which this work was done are rice husk ash (largely silica), commonly occurring pebbles and ordinary Portland cement, all of which come under the broad category of ceramic materials, the methodology can be applied to the reduction of variation in ceramic processes and products wherever applicable.