Showing papers in "Transactions of The Indian Ceramic Society in 1995"
TL;DR: High purity ceramic materials like alumina ceramics, which can be offered with novel formations and modifications using advanced processing techniques, offer a wide spectrum of enhanced properties such as high mechanical strength, wear resistance, corrosion resistance, capability to withstand high temperatures and thermal stresses, high electric insulation and improved dielectric properties.
Abstract: High purity ceramic materials like alumina ceramics, which can be offered with novel formations and modifications using advanced processing techniques, offer a wide spectrum of enhanced properties such as high mechanical strength, wear resistance, corrosion resistance, capability to withstand high temperatures and thermal stresses, high electric insulation and improved dielectric properties. High purity alumina ceramics with controlled composition and uniform minimal particle size can offer desired properties at low costs as needed for many engineering applications.High purity alumina (up to 99.99%, purity) is used in diverse engineering applications including electronics industry, wear resistant parts, corrosion resistant parts, chemical processing, translucent enclosures for highly corrosive sodium vapour (high pressure sodium vapour lamps), synthetic gems, oil and gas processing, refractories and a wide variety of industrial applications. The chemical applications to eliminate foaming and as catalyst i...
16 citations
TL;DR: Alumina ceramics have been recognized to be useful materials for fabricating substitutes for parts of human bone for nearly two decades, and at present, it is one of the widely used biomaterials for bone replacement as discussed by the authors.
Abstract: For nearly two decades, alumina ceramics have been recognized to be useful materials for fabricating substitutes for parts of human bone. Alumina ceramic was first applied as a clinical material in 1960's. Subsequently, it was extensively investigated and at present, it is one of the widely used biomaterials for bone replacement. Because of their relatively high strength and good wear resistance, they are good materials to be used in load bearing devices, particularly as the ball and socket components of hip prosthesis. They are also used to develop prosthesis for non-load bearing situations. Examples are maxillofacial restorations, ossicular chain replacements, keratoprosthesis and dental implants.Depending on the nature of the response ceramics elicit in the body, they are classified into three types, namely biodegradable, bioinert and bioactive. Each type has its advantages and disadvantages. In recent years, improvements have been made in alumina materials by various structural modifications and by fo...
6 citations
TL;DR: In this paper, the structure-property relations in boehmite sol-gel based synthesis of high temperature alumina ceramics are discussed and the importance of hydrolysis procedure and calcination conditions in the control of the end properties is highlighted.
Abstract: Alumina has been recognised as one of the most important high temperature ceramic materials; as its application has expanded the scope, a variety of preparative processes have also emerged. For example, sol-gel based synthesis techniques have been applied with a variety of modifications. The monohydroxy aluminium oxide (boehmite) is the precursor in most of the synthesis techniques. Keeping boehmite sol as the starting material, ceramic materials such as alumina, aluminium titanate and alumina-titania high surface area particulates have been prepared at low processing temperatures, and are reported here.Details regarding the in-depth problems with respect to the understanding of structure-property relations in boehmite are presented. Further, the details of synthesis of some high temperature alumina ceramics are discussed. The importance of hydrolysis procedure and calcination conditions in the control of the end properties is highlighted.
5 citations
TL;DR: Fused boric acid reacted with urea to form a solid mass having an indefinite composition, B2O3.xNH3 as mentioned in this paper, which was further heated in an atmosphere of ammonia to 900°C, when the excess urea was removed, leaving a refractory white residue.
Abstract: Fused boric acid reacted with urea to form a solid mass having an indefinite composition, B2O3.xNH3. It was further heated in an atmosphere of ammonia to 900°C, when the excess urea was removed, leaving a refractory white residue. The product was further heated in nitrogen atmosphere at temperatures ranging from 1100° to 1400°C for 1–4 hours. The powders obtained were boiled in water/HC1 and filtered. The washed samples were characterized by IR and X-ray studies and chemical analysis.At 900°C, two soluble phases were detected: one was isostructural with ammonium borate pentahydrate and the other with boric acid, wherein the OH groups were partially replaced by NH2. On further heating, reactions between NH2 and NH2OH led to the formation of B-NH-B and finally B-N bonds. With rising temperature, increasing amounts of the soluble phase were converted to boron oxynitride and a nitride of 90% purity was formed at 1400°C and of 95% purity at 1600°C in an inert atmosphere.
4 citations
TL;DR: In this paper, preliminary results on fabrication of Al2O3/Al composites by a metathesis reaction between silicon dioxide preforms and molten aluminium are reported, and the reaction ingredients employed were pure aluminium (commercial grade-IS) and optical grade silica glass.
Abstract: The co-continuous alumina/aluminium based composites show immense potential for high performance engineering applications where alumina offers superior stability to oxidation at elevated temperatures. In this paper preliminary results on fabrication of Al2O3/Al composites by a metathesis reaction between silicon dioxide preforms and molten aluminium are reported. The reaction ingredients employed were pure aluminium (commercial grade-IS) and optical grade silica glass. The transformation kinetics were studied in the temperature regimes of 900°-1300°C in 100°C steps and the various reaction times between 5.0 mins and 18.0 hrs. The composite growth took place through the formation of an intermediate phase and followed a linear rate behaviour. The width of the reaction interface decreased with the increase/decrease in temperature of the reaction. Typical growth rates of about 1.0 and 5.0 mm.h−1 were obtained at 1000° and 1200°C respectively. Bulk density of these composites was estimated to be 3.2 gm.cm−3. O...
4 citations
TL;DR: In this article, the authors used a micropipette and sandwiched between two 300 mesh TEM nickel grids placed on copper plate supports to obtain a sonogelation sample, which was then plunged into liquid freon at high speeds.
Abstract: Cryogenic scanning electron microscopy as a tool to image ‘wet’ sol to gel transformations, has been applied for the first time to obtain microstructural information during controlled hydrolysis. Aluminium sec-butoxide was chelated with a 1:1 mole ratio of ethyl acetoacetate. About 5.0 ml of isopropanol per gram of alkoxide was added to the chelated batch, and a powerful contact mode probe type ultrasonication performed to yield an intimately blended alumina sol. A controlled water addition at the rate of 0.4 ml per hour per gram of alkoxide was done on the sol. About 100 microlitre of samples in varying stages of sonogelation was extracted using a micropipette and sandwiched between two 300 mesh TEM nickel grids placed on copper plate supports. The sandwiched sample was plunged into liquid freon at high speeds to achieve a rapidly solidified state without crystallization. The sample was thermally fixed and placed in the microscope which was previously cooled to −170°C using liquid N2. Microscopic contras...
3 citations
TL;DR: In this paper, new data on geology, mineralogy and geochemistry for the different types of bauxite profiles from India were provided. And with this knowledge, a pragmatic classification was proposed for the Bauxite deposits.
Abstract: This paper comprises new data on geology, mineralogy and geochemistry for the different types of bauxite profiles from India. With the necessary software developed all the data in addition to the existing are construed and the geomodelling has been brought out. Fortified with this knowledge, a pragmatic classification is proposed for the bauxite deposits. The significance of the various aspects that have been undertaken in this work is fully discussed.
2 citations
TL;DR: In this article, a study regarding the morphological changes in upper layer of window glasses has been carried out with the help of optical microscopy, it is evident that the attack on window glasses is much more in the presence of sulphate and fluoride aggressive ions as compared to that of chloride ions.
Abstract: Window glasses in prolonged contact with water develop relatively thick layer crusts due to attack of corrosive environment. In the present study the corrosion behaviour of polished window glasses in plain water and in the presence of sulphate and fluoride as well as chloride aggressive ions in water have been examined at atmospheric temperature ranging from 25°to 30°C. A study regarding the morphological changes in upper layer of window glasses has been carried out with the help of optical microscopy. From these studies, it is evident that the attack on window glasses is much more in the presence of sulphate and fluoride aggressive ions as compared to that of chloride ions. Transmittance of corroded window glasses has also been recorded.
2 citations
TL;DR: In this article, a systematic investigation has been performed to find out the effect of different process parameters like pretreatment of ceramic, paint composition, metallization temperature, time and at...
Abstract: Ultra high vacuum (UHV) joining between alumina ceramics and metal is the key to the success of many devices used in modern technology. The conventional processes like high-temperature Sintered Metal Powder Process (SMPP) and active metal brazing are capital intensive and are not suitable for custom made items where the requirement of the product is small. In such cases, solution metallization is an easy and economic alternative. Over a decade we have perfected this method for the fabrication of high-tech UHV device like Linac. Though this process requires only 1050°C vis-a-vis 1500°C for SMPP, performance-wise ceramic to metal seals made by solution metallization are comparable to or in some respect better than those obtained by other established processes. The bond quality is dependent upon several process parameters. A systematic investigation has been performed to find out the effect of different process parameters like pretreatment of ceramic, paint composition, metallization temperature, time and at...
2 citations
TL;DR: The effect of ambient atmosphere on the sintering of oxides was studied ever since the first experiments on aluminium oxide spheres were married out as mentioned in this paper, and several effects of atmosphere on sinterings have been found to be important, depending on the nature of interaction, whether physical or chemical, of the active species present in the atmosphere with the solid undergoing sinter.
Abstract: The effect of ambient atmosphere on the sintering of oxides was studied ever since the first experiments on sintering of aluminium oxide spheres were married out Several effects of atmosphere on sintering have been found to be important. These depend on the nature of interaction, whether physical or chemical, of the active species present in the atmosphere with the solid undergoing sintering. Atmosphere control of point defect concentration is touched upon. Atmospheric effects on technical ceramics are briefly reviewed. Sintering behaviour of alumina in gaseous atmospheres is analysed on the basis of such reactions. Microstructure development during atmosphere resintering is discussed.
1 citations
TL;DR: In this paper, the authors made hydration studies of non-portland blended cements made from bag house dust and a number of industrial and agricultural waste materials exhibiting pozzolanic properties.
Abstract: Hydration studies were made of non-portland blended cements made from bag house dust and a number of industrial and agricultural waste materials exhibiting pozzolanic properties. The results have shown that the blended cements made from rice husk ash fired at 700°C have the best cementing properties. When bag house dust is mixed with granulated blast furnace slag, it is observed that there is an optimum amount of bag house dust which exhibits the best cementing properties. It has further been observed that in super-sulphated cements, bag house dust is a better activator of granulated blast furnace slag than lime. The overall hydration studies have shown that the blended cements reported in this communication can work as masonry cements in rural areas for non-structural work
TL;DR: In this paper, three precursors of equivalent oxide composition 2MgO. SiO2, viz. a colloidal gel (partially crystalline) prepared from magnesium nitrate hexahydrate and colloidal silica sol, (ii) a Colloidal gel(partially, n-hydrate) from the same colloidal sol and (iii) a mechanical mixture of quartz and MgO were used for examining their relative reactivities in the formation of forsterite, Mg2SiO4.
Abstract: Three precursors of equivalent oxide composition 2MgO. SiO2, viz. (i) a colloidal gel (partially crystalline) prepared from magnesium nitrate hexahydrate and a colloidal silica sol, (ii) a colloidal gel (partially crystalline) prepared from magnesium chloride n-hydrate and the same colloidal silica sol and (iii) a mechanical mixture of quartz and MgO were used for examining their relative reactivities in the formation of forsterite, Mg2SiO4. The samples were heat treated at temperatures in the range 1000°-1400°C with soaking periods of less than 1 hr to 110 hours. X-ray analyses showed the nitrate-derived gel to be the most reactive, followed by the chloride-derived gel; the crystalline oxide mixture showed sluggish reaction.
TL;DR: In this article, the use of alumina ceramics in structural applications has increased in the recent past and is likely to go up further as progress is made in their processing and understanding their mechanical behaviour.
Abstract: Alumina ceramics constitute an important class of structural ceramics. Their use in the structural applications has increased in the recent past and is likely to go up further as progress is made in their processing and understanding their mechanical behaviour. Low reliability, as reflected in the Weibull modulus m, and low fracture toughness KIClimit the use of alumina ceramics in more demanding structural applications. The coarse grained aluminas display the phenomenon of crack bridging which leads to greater flaw tolerance and is actively being researched at present. Another thrust area is the development of alumina based composites.
TL;DR: In this article, various methods of preparation of reactive alumina powders (sinterable at 1823K) required for advanced ceramic applications have been reviewed and the factors influencing the formation of particles of controlled characteristics have been summarized.
Abstract: The various methods of preparation of reactive alumina powders (sinterable at 1823K) required for advanced ceramic applications have been reviewed. The factors influencing the formation of particles of controlled characteristics have been summarized. The various methods of preparing alumina powders like modified Bayer Process, decomposition of alum and sulphate, freeze drying, plasma evaporation and gas phase reactions, controlled solution methods (like sol-gel, homogeneous precipitation and emulsion technique etc) have been briefly described. Finally, the results of the study carried out in our laboratory on preparation of reactive alumina powders of controlled morphologies by the homogeneous precipitation-crystallization technique are reported.
TL;DR: A brief presentation of the raw materials for alumina ceramics is made in this paper, where a survey of the world scene is made and the situation in India is briefly reviewed.
Abstract: A brief presentation is made of the raw materials for alumina ceramics. The important source is the alumina trihydrate resulting from the Bayer process. Purification of the Bayer aluminate liquor to minimise organics, iron oxide and silica, reduction of sodium oxide content, special conditions of precipitation and calcination and fine grinding of the calcined material lead to the production of various grades of alumina. Other processes involve acidification of the aluminate liquor followed by drying and calcination or treatment of aluminium amalgam with water to precipitate aluminium hydroxide. Typical properties and applications of alumina ceramics are discussed. A survey of the world scene is made and the situation in India is briefly reviewed. The importance of introducing collaborative efforts to accelerate activities in this field in India is stressed.
TL;DR: In this paper, the authors have examined the general characteristics, chemical, mineralogical and physical behaviour of talc from individual sources to identify and estimate the quality of the mineral as per BIS specification.
Abstract: The extensive deposits of talc occurring at Dagotha in Jaipur district, at Ghewaria and Chandpura in Bhilwara district and at Devpura in Udaipur district of Rajasthan have been characterised mineralogically as well as industrially for utilisation in the field of electroceramics. The study includes the examination of general characteristics, chemical, mineralogical and physical behaviour of talc from individual sources to identify and estimate the quality of the mineral as per BIS specification. The fired properties at four different temperatures starting from 1250° to 1400°C at an interval of 50°C with 2 hrs soaking at the peak temperatures were found out so as to get all possible information for utilising the mineral in the body-mix for high-frequency low-loss steatite insulator. Investigations have also been made by judicial incorporation of talc separately in a typical composition of electro-porcelain and then by evaluation of the product at five different temperatures of 1200°, 1250°, 1300°, 1325° and 1350°C with two hours soaking each for physical and electrical properties suitable for use in radio, radar and other electronic devices.
TL;DR: In this paper, the authors investigated microstructural uniformity and homogeneity of cold-pressed green samples of pure, undoped, as-received alumina, fired by hybrid heating (MHH) vis-a-vis conventional fast firing (CFF) and found that larger masses show a better parity in temperatures between the surface and the interior of the sample.
Abstract: Microwave (hybrid) heating (MHH) is a unique combination of microwave (MW)-material interaction and conventional radiant heating/conduction mechanisms that facilitates the attainment of very high heating rates in a 2.45 GHz multimode MW cavity. Microstructural uniformity and homogeneity of cold-pressed green samples of pure, undoped, as-received alumina, fired by MHH vis-a-vis conventional fast firing (CFF) has been investigated. The synergism of the twin heating mechanisms (with MHH) results in an improved parity in temperatures across the sample cross-sections vis-a-vis CFF and stand-alone MW (SMW) sintering; this enhanced parity in temperatures (with MHH) can be premised to be responsible for the better microstructural homogeneity and enhanced mechanical properties relative to CFF. Sintering of larger (20 gm vs 6 gm) samples with MHH shows evidence of a definitive mass dependence on the MHH phenomenon. Larger masses show a better parity in temperatures between the surface and the interior of the sample...
TL;DR: In this paper, the in situ processing of alumina-based CMCs by directed oxidation of aluminium is described, which essentially involves a rapid oxidation of a molten Al-alloy with the vapour pha...
Abstract: The Ceramic-Matrix-Composites (CMCs) have come into prominence for structural applications because of their superior mechanical properties both at room temperature and at elevated temperatures. In conventional processing route of pressureless sintering, the rigid reinforcement phase (particulate or whisker) severly retards the densification. The obvious solution of high temperature hot pressing or HIPing makes the process energy and cost intensive. Some recent developments on the reaction-forming of CMCs such as self propagating high temperature synthesis (SHS), co-continuous ceramic composites (C4 materials), directed metal oxidation (DIMOX) etc have, however, opened up new areas of applications for CMCs like wear resistant parts for a variety of process industry equipment, automobile and armour components.The present paper describes the in situ processing of alumina based CMCs by directed oxidation of aluminium. This process essentially involves a rapid oxidation of a molten Al-alloy with the vapour pha...
TL;DR: In this article, the influence of powder characteristics on sintering and wear resistance properties of the fabricated grinding media during milling has been evaluated for wear resistant applications, in order to optimise the powder characteristics for wear-resistant applications.
Abstract: In line with ACC's stride towards new materials, the Research & Consultancy Directorate of the company has successfully developed and scaled up the process for manufacture of high and ultra high purity alumina powders at semi-commercial levels for high performance, structural and electronic applications.Among the various applications of high purity alumina powders, wear resistant parts and thermal barrier coatings are of prime importance for the domestic market. In order to optimise the powder characteristics for wear resistant applications, a study was undertaken to evaluate the influence of various parameters such as chemical purity, phase composition, particle size distribution, specific surface area (BET) of starting powders and their effect on sintering and wear properties. The paper highlights the influence of powder characteristics on sintering and wear resistance properties of the fabricated grinding media during milling.
TL;DR: In this article, two different types of mullite, namely, electrofused and sol-gel derived materials, were selected to have a comparative study of their properties, and the results showed that the solgel mullite showed better mechanical properties.
Abstract: In the present investigation, two different types of mullite, namely, electrofused and sol-gel derived materials, were selected to have a comparative study of their properties. The mullites were compacted at a pressure ranging from 300 to 350 MPa followed by sintering at 1650° and 1700°C for one hour. It was found that the sol-gel mullite showed better mechanical properties. Dielectric constant of the sample showed a direct relation with the sintered density. Higher A12O3 containing mullite showed higher thermal shock resistance.
TL;DR: In this article, the ceramic materials play a key role in the medical devices and implants used for diagnostic or therapeutic purposes, though not occupying the leading role like polymers, they play a complementary role.
Abstract: Biomaterials play a key role in the medical devices and implants used for diagnostic or therapeutic purposes. Among these, the ceramic materials, though not occupying the leading role like polymers...
TL;DR: A glass composition of Li2O-15, Al2O3-11, SiO2-74 wt% doped with 16 parts of TiO2 per 100 parts of glass was melted and heat treated at 550° and 850°C, considered to be nucleation and crystallizati...
Abstract: A glass composition of Li2O-15, Al2O3-11, SiO2-74 wt% doped with 16 parts of TiO2 per 100 parts of glass was melted and heat treated at 550° and 850°C, considered to be nucleation and crystallizati...
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TL;DR: A review on glasses for biomedical applications with particular emphasis on calcium-iron-phosphate type glasses is presented in this article, where a wide range of glass forming compositions exist in the system which can provide materials having the needed mechanical and biochemical properties.
Abstract: A review on glasses for biomedical applications with particular emphasis on calcium-iron-phosphate type glasses is presented. A wide range of glass forming compositions exist in the system which can provide materials having the needed mechanical and biochemical properties. The redox state of iron containing glasses is sensitive to melting atmosphere which in turn also affects their chemical and physical properties. Calcium phosphate glasses are diamagnetic, whereas calcium-iron-phosphate glasses are paramagnetic. A few spontaneously crystallized materials, exhibiting ferrimagnetic behaviour, are biocompatible. A few orthopaedic devices, designed and fabricated into composite forms using fibres produced from these compositions and polylactic acid (PLA) polymer, are being evaluated at present. Potential products and research issues have also been identified and discussed.
TL;DR: In order to identify the minerals and the association of valuable ore mineral with the gangue, characterisation studies of low grade Magnesite of Parshad area, Udaipur district, Rajasthan were undertaken Petrography, physicochemical characteristics, DTA, TGA, DTGA, vitrification study and X-ray analysis were carried out to characterise the magnesite.
Abstract: The amenability and selection of the process for beneficiation of ores are based on the mineralogy and texture of the mineral, type of impurities present in it and the mode of association of gangue and value minerals, their liberation characteristics etcIn order to identify the minerals and the association of valuable ore mineral with the gangue, characterisation studies of low grade magnesite of Parshad area, Udaipur district, Rajasthan were undertaken Petrography, physicochemical characteristics, DTA, TGA, DTGA, vitrification study and X-ray analysis were carried out to characterise the magnesiteThe characterisation studies reveal that the magnesite ore is mainly composed of magnesite with minor amounts of quartz and iron Other minerals, namely, calcite, sericite and clinozoisite are present in traces Based on the studies, the possible beneficiation route was identified
TL;DR: In this article, different techniques of preparation of alumina sols are briefly described, including preparation of monoliths, microspheres, etc by using precursor sols, and they are discussed in detail.
Abstract: Different techniques of preparation of alumina sols are briefly described. Preparative techniques of alumina monoliths, microspheres etc by using precursor sols are discussed.
TL;DR: In this article, the dopants Fe, Co and Ni are considered for substituting Cu in Y1Ba2Cu3O7-δ for different oxygen co-ordinations and the results of variation of orthorhombicity and Tc with substitution indicate that Fe and Co substitutes occupy the Cu-sites of analgous oxygen coordination.
Abstract: Y1Ba2Cu3O7-δ has a structural characteristic of two inequivalent Cu-site, Cu(I) and Cu(II), of different oxygen co-ordinations. The contrasting effect of substitution for Cu in these two sites is of considerable interest. The dopants Fe, Co and Ni are considered here for substituting Cu. Unit cell parameters obtained by X-ray diffraction analysis were used to estimate change in orthorhombicity with substitution content which shows 0 →T phase transformations at x < 0.1. The merging of the characteristic split peak of orthorhombic/tetragonal at 20 ≈33° confirms the phase transformations. The critical transition temperature (Tc) determined by the temperature dependent electrical resistivity measurements using the standard four probe technique exhibits depression with dopant content. The results of variation of orthorhombicity and Tc with substitution indicate that Fe and Co substitutes occupy the Cu-sites of analgous oxygen co-ordination, i. e. Cu(I) sites in the basal plane, while Ni occupies Cu (II) sites ...
TL;DR: A significant change in the d → d absorption features of incorporated divalent copper ion has been noted in case of a phosphate glass with addition of alumina as one of its major components as discussed by the authors.
Abstract: A significant change in the d → d absorption features of incorporated divalent copper ion has been noted in case of a phosphate glass with addition of alumina as one of its major components.
The observed spectral change of the ion in the glass has been correlated to the structural change of the glass network that results due to the cross-linking of the phosphate chains of the glass by the alumina.
TL;DR: In this paper, the processing steps for the injection molding of alumina shapes have been described, specifically mentioning the different criteria to be considered at each steps to achieve the desired products.
Abstract: The importance of injection moulding to form complex shapes like turbine rotors, stators, nozzles, seals etc is well-recognized. However, the fabrication process necessitates a control over the different processing parameters including the choice of organic additives like binders and plasticizers and their burn out schedule. The processing steps for the injection moulding of alumina shapes have been described, specifically mentioning the different criteria to be considered at each steps to achieve the desired products.
TL;DR: In this article, the surface area and porosity of the gels were determined with and without chelating agent and the particle size distribution of the sols were studied with respect to variations in the amount of the chelation agent.
Abstract: Aluminium isopropoxide precursor has been modified by addition of ethyl acetoacetate and subsequently hydrolysed with excess of water to give alumina gels. These gels were calcined at different temperatures to give different phases of alumina powders. The surface area and porosity of the gels were determined with and without chelating agent. The particle size distribution of the sols was studied with respect to variations in the amount of the chelating agent. It is found that the above variations do bring about a change in the morphology and the microstructure of these gel powders. In addition to the chelating agent, 2 wt% of fine γ- and a mixture of γ- and α-Al2O3 powders was added to the hydrolysed sols. These powders acted as seeds for the promotion of-α- Al2O3 formation. These systems were gelled, dried and heat treated to give α- Al2O3. The morphology and the microstructure of these seeded gels were studied and compared with those of the unseeded gels.
TL;DR: In this paper, the surface of SiC obtained from rice husk at 1500°-1800°C has been studied before and after sputtering and the presence of Si, C, O and F in the surface is indicated.
Abstract: Surface of SiC obtained from rice husk at 1500°-1800°C has been studied by AES before and after sputtering. Presence of Si, C, O and F in the surface is indicated. Binding energies of these elements with intensity, area and other observations are tabulated. Individual spectra of the elements are presented and difference between sputtered and unsputtered surface is brought out.