Cerami Engine Block

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TABLE OF CONTENTSAbstractContent Page1.0 Introduction........................................................................................................ 1

1.1 Aim......................................................................................................... 11.2 Objectives............................................................................................... 1

2.0 Properties of Ceramics....................................................................................... 22.1 Silicon Nitride……................................................................................ 32.2 Properties of Silicon Nitride................................................................... 4

3.0 Manufacturing of Ceramics................................................................................ 83.1 Preparation of Starting Powder............................................................... 8

3.1.1 Crushing…………………………………………………… 83.1.2 Grinding…………………………………………………… 9

3.2 Powder Processing…............................................................................. 93.3 Shape Forming........................................................................................ 10

3.3.1 Uniaxial Die Pressing……………………………………… 113.3.2 Isostatic Die Pressing……………………………………… 113.3.3 Injection Moulding…………………………………………..123.3.4 Extrusion………………………………………………… 13

3.4 Drying…………….................................................................................. 143.5 Sintering………………............................................................................ 153.6 After Firing Operations…………………………………………………..15

3.6.1 Diamond Grinding…………………………………………....153.6.2 Glazing………………………………………………………...153.6.3 Cleaning……………………………………………………….16

4.0 Design.................................................................................................................... 174.1 Engine Block……...................................................................................... .17

4.1.1 Materials Used and Manufacturing Processes………………...174.2 Silicon Nitride……….............................................................................. …18

4.2.1 Production…………………………………………………......185.0 Performance of Ceramic Engine Block…………………………………………….19

5.1 Metal Engine Block…………………………………………………………195.2 Ceramic Engine Block………………………………………………………19

6.0 Market Analysis…………………………………………………………………….226.1 Conventional Engine Block…………………………………………………226.2 Ceramic Engine Block………………………………………………………236.3 Cost Benefit Analysis……………………………………………………….23

6.3.1 Weight Reduction……………………………………………….236.3.2 Performance……………………………………………………..236.3.3 Life Span………………………………………………………...24

7.0 Conclusion……………………………………………………………………………24References

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List of Figures:

Figure 1 – Properties Enhancement since 1960Figure 2 – Silicon nitride evolving from high temperature to high tensile strengthFigure 3 – of the fracture toughness of new ceramic materials with conventional ceramics andother key structural materialsFigure 4 – Flow chart of Ceramics ManufacturingFigure 5 – Various types of crushing processesFigure 6 – Set up of Powder Processing UnitFigure 7 – Setup of Die PressingFigure 8 – Setup of Cold Isostatic ProcessingFigure 9 – Typical setup for Injection Moulding ProcessFigure 10 – Setup for ExtrusionFigure 11 - Changes in Vol. with waterFigure 12 - Representation of Drying ProcessFigure 13 – Sintering MillFigure 14 – Glazing in progressFigure 15 – Basic Engine BlockFigure 16 – Operating temp of metals and ceramicsFigure 17 – Fully Prepared Engine BlockFigure 18 – Cost Benefit Analysis

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1.0 Introduction:

Ceramics materials like many other materials evolved from a different discipline by today’sstandards. Materials engineering is grouped with Ceramics Engineering to this day. Universitieswith ceramics programs include a curriculum saturated with materials engineering classes. Themodern day ceramic engineer may find themselves in a variety of industries. Similar to otherdisciplines a ceramic engineer may find themselves in mining and mineral processing,pharmaceuticals, foods, and chemical operations.

Now a multi-billion dollar a year industry, ceramic engineering and research has establisheditself as an important field of science. Applications continue to expand as researchers developnew kinds of ceramics to serve different purposes. An incredible number of ceramics engineeringproducts have made their way into modern life. The largest producers of engineered ceramics--and largest employers of ceramic engineers--include AVX, CeramTec, CoorsTek, Corning,EDO, Kohler, Kyocera, Morgan Crucible, Murata, Saint- Gobain and 3M.

Ceramics are not new to the Automotive Industry also. In the early 1980s, Toyota researchedproduction of an adiabatic ceramic engine which can run at a temperature of over 6000 °F (3300°C). Ceramic engines do not require a cooling system and hence allow a major weight reductionand therefore greater fuel efficiency. Fuel efficiency of the engine is also higher at hightemperature, as shown by Carnot’s theorem. In a conventional metallic engine, much of theenergy released from the fuel must be dissipated as waste heat in order to prevent a meltdown ofthe metallic parts. Despite all of these desirable properties, such engines are not in productionbecause the manufacturing of ceramic parts in the requisite precision and durability is difficult.Imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipmentfailure. Such engines are possible in laboratory settings, but mass-production is not feasible withcurrent technology.

Work is being done in developing ceramic parts for gas turbine engines. Currently, even bladesmade of advanced metal alloys used in the engines’ hot section require cooling and carefullimiting of operating temperatures. Turbine engines made with ceramics could operate moreefficiently, giving aircraft greater range and payload for a set amount of fuel.

1.1 Aim:To study the effects brought about by making Engine Block out of Modern Ceramicsinstead of conventional Aluminum Alloys or Cast Iron.

1.2 Objective:

To study the benefits brought by use of Ceramics. To study the design considerations while making Engine Block out of Ceramics To study the impact of the product on the production.

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2.0 PROPERTIES OF CERAMICS:

The discipline of material science involves investigating the relationships that exists between thestructures and properties of materials. In contrast, materials engineering is on the basis of thesestructure-property correlations, designing or engineering the structure of a raw material toproduce a predetermined set of properties. This section deals with the important properties ofceramics as a whole and in detail about those ceramics which are being used in the AutomotiveIndustry (in specific about the adiabatic ceramic engine).While in service use, all materials are exposed to external stimuli that evoke some kind ofresponse in the material. That material trait in terms of the kind and magnitude of response to aspecific imposed stimulus is called the property of material.Virtually all important properties of solid materials maybe grouped into six different categories:mechanical, electrical, thermal, magnetic, optical and deteriorative. For each there is acharacteristic type of stimulus capable of provoking different responses. The behavior/propertyof material to the specific stimulus can be shown as mechanical when subjected to load/force,electrical when is put through electric field, thermal when applied upon by heat, magnetic whenthe response is due to magnetic field applied, optical when the stimulus is electromagnetic orlight radiation and finally deteriorative which explains its chemical reactivity.

Some of the important properties of ceramics which come under all the above stated categoriesare given below:

Excellent harness Excellent oxidation resistance Excellent chemical stability High temperature resistance Good wear resistance Good compressive strength Non-magnetic nature Moderate tensile strength Good refractory nature Low thermal conductivity Low electrical conductivity Poor thermal shock resistance Poor impact strength Low creep failure Prone to brittle fracture

Combination of all these properties can provide a material with:

High wear resistance with low density High wear resistance in corrosive environments Corrosion resistance at high temperatures Harder and stiffer solid than steel More heat and corrosion resistance than metals and polymers Less density than most metals and polymers

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Materials with such combinations of properties are very rarely found in the real life in the formof ores unless some complex blending techniques of materials are used to get differentcompositions which could offer desired properties. Materials to be used in automotive andaircraft industries are very carefully chosen to meet the worst conditions in operation due to thevast amounts of thermal and chemical aspects involved. Often, material compositions arechanged to meet the operation requirements with which some issues on traits can be resolved.The properties like high temperature strength, excellent hardness, high corrosion resistance,excellent chemical stability, good wear resistance, etc have made the technical ceramic materialsan alternative option when the question of which material to choose for an automobile engine isthought of. Once, when the thought to use ceramics for automobile engine is working its way on,a designer will think about consequences of using Silicon nitride as the optimum material.

2.1 Silicon nitride

Silicon nitride is a man made compound synthesized through several different chemical reactionmethods. It is a chemical compound of silicon and nitrogen and is a very hard and refractorymaterial. It is dark gray to black in color and can be polished to very smooth reflective surface,giving parts with a striking appearance. It is manufactured by very well developed methods toproduce a ceramic with unique set of outstanding properties. It was first produced in 1857 but itscommercial production had started only in the 1950’s when the search of fully dense, highstrength and high toughness materials to replace metals with ceramics in advanced turbine andreciprocating engines to give higher operating temperatures and efficiencies is going on.Although the ultimate goal of a complete ceramic engine has never been achieved, silicon nitridehas been used in a number of industrial applications, such as engine components, bearings andcutting tools.Silicon nitride has better capabilities than most metals and also possesses better properties thanother ceramic materials. It has been extensively used in automotive applications like in enginewear parts, such as valves and cam followers and is likely to be used in turbocharger rotors andceramic engines which could be feasible with the cost drooping down.

The ceramics in this family have a favorable combination of properties that include: High strength over a broad temperature range High hardness Moderate thermal conductivity Low coefficient of thermal expansion Moderately high elastic modulus Unusually high fracture toughness Superior thermal shock resistance Excellent wear resistance Mechanical fatigue and creep resistance Good oxidation resistance Ability to withstand high structural loads to high temperature

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Strength: Strength is a property that enables a material resist deformation under load. Theultimate strength is the maximum strain a material can withstand. Tensile strength is ameasurement of the resistance to being pulled apart when placed in a tension load. Fatiguestrength is the ability of material to resist various kinds of rapidly varying stresses and isexpressed by the magnitude of alternating stress for a specified number of cycles. Impactstrength is the ability of a metal to resist suddenly applied loads and is measured in foot-poundsof force.Hardness: Hardness is the property of a material to resist permanent indentation. Indentationoccurs on material surfaces when they rub against each other or when a material comes incontact with another with a shearing force.Toughness: Toughness is the property that enables a material to withstand shock and to bedeformed without rupturing. Toughness may be considered as a combination of strength andplasticity.Elasticity: Elasticity is the ability of a material to return to its original shape after the load isremoved. Theoretically, the elastic limit of a material is the limit to which a material can beloaded and still recover its original shape after the load is removed.Brittleness: Brittleness is the opposite of the property of plasticity. A brittle metal is one thatbreaks or shatters before it deforms. Generally, brittle metals are high in compressive strengthbut low in tensile strength.Thermal conductivity: It is defined as the property of a material that indicates its ability toconduct heat.Coefficient of thermal expansion: All materials change their size when subjected to atemperature change as long as the pressure is held constant. The coefficient of thermal expansiondescribes how the size of an object changes with a change in temperature.Thermal shock resistance: It is defined as the ability of the material to withstand shock loadsacting at high temperature.

2.2 Properties of Silicon Nitride:

Silicon Nitride, Hot Pressed

Mechanical SI/Metric (Imperial) SI/Metric (Imperial)

Density gm/cc (lb/ft3) 3.29 (205.4)

Porosity % (%) 0 (0)

Color — black —

Flexural Strength MPa (lb/in2x103) 830 (120.4)

Elastic Modulus GPa (lb/in2x106) 310 (45)

Shear Modulus GPa (lb/in2x106) — —

Bulk Modulus GPa (lb/in2x106) — —

Poisson’s Ratio — 0.27 (0.27)

Compressive Strength MPa (lb/in2x103) — —

Hardness Kg/mm2 1580 —

Fracture Toughness KIC MPa•m1/2 6.1 —

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Maximum Use Temperature(no load) °C (°F) 1000 (1830)

Thermal

Thermal Conductivity W/m•°K (BTU•in/ft2•hr•°F) 30 (208)

Coefficient of Thermal Expansion 10–6/°C (10–6/°F) 3.3 (1.8)

Specific Heat J/Kg•°K (Btu/lb•°F) — —

Electrical

Dielectric Strength ac-kv/mm (volts/mil) — —

Dielectric Constant — — —

Dissipation Factor — — —

Loss Tangent — — —

Volume Resistivity ohm•cm — —

Table 1 – Properties of Silicon Nitride(http://www.accuratus.com/silinit.html)

Silicon Nitride, Pressureless Sintered

Mechanical SI/Metric (Imperial) SI/Metric (Imperial)

Density gm/cc (lb/ft3) 3.27 (204)

Porosity % (%) 0 (0)

Color — black —

Flexural Strength MPa (lb/in2x103) 689 (100)

Elastic Modulus GPa (lb/in2x106) 310 (45)

Shear Modulus GPa (lb/in2x106) — —

Bulk Modulus GPa (lb/in2x106) — —

Poisson’s Ratio — 0.24 (0.24)

Compressive Strength MPa (lb/in2x103) — —

Hardness Kg/mm2 1450 —

Fracture Toughness KIC MPa•m1/2 5.7 —

Maximum Use Temperature(no load) °C (°F) 1000 (1830)

Thermal

Thermal Conductivity W/m•°K (BTU•in/ft2•hr•°F) 29 (201)

Coefficient of Thermal Expansion 10–6/°C (10–6/°F) 3.3 (1.8)

Specific Heat J/Kg•°K (Btu/lb•°F) — —

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Electrical

Dielectric Strength ac-kv/mm (volts/mil) — —

Dielectric Constant — — —

Dissipation Factor — — —

Loss Tangent — — —

Volume Resistivity ohm•cm — —

Table 2 – Properties of Sintered Silicon Nitride(http://www.accuratus.com/silinit.html)

Given below are typical characteristics of ceramics:

Figure 1: Properties Enhancement since 1960(http://www.ms.ornl.gov/programs/energyeff/cfcc/iof/chap21-2sin.pdf)

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Figure 2: Silicon nitride evolving from high temperature to high tensile strength.(http://www.ms.ornl.gov/programs/energyeff/cfcc/iof/chap21-2sin.pdf)

Figure 3: Comparison of the fracture toughness of new ceramic materials with conventionalceramics and other key structural materials.

(http://www.ms.ornl.gov/programs/energyeff/cfcc/iof/chap21-2sin.pdf)

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3.0 MANUFACTURING OF CERAMICS:

The flow chart of Ceramic manufacturing is shown in figure 4.

Figure 4: Flow chart of Ceramics Manufacturing(http://fire.nist.gov/concpubs/talks/talkI/sld003.htm)

3.1 Preparation of Starting Powder:

The shaping process for traditional ceramics requires that starting material must be in theform of plastic paste. This paste is made of fine ceramic powders mixed with water and itsconsistency determines the ease of forming the material and the quality of final product. Theraw material usually occurs in nature a rocky lumps and reducing it to powder form is thepurpose of preparation in ceramic processing.

Techniques for reducing particle size in ceramics processing include mechanical energy invarious forms such as impact, compression and attrition. The term ‘Comminution’ is used forthese techniques which are most effective in brittle materials. Two general operationsincluded in this process are: crushing and grinding.

3.1.1 Crushing:

It refers to reduction from large lumps to smaller sizes for further reduction. Several stagesmay be required for this and the reduction ratio in each stage being in the range 3 to 6.Crushing of minerals is accomplished by compression against rigid surfaces. Below figureshows various types of equipment used for crushing;(a) jaw crushers in which a large jawtoggles back and forth to crush lumps against a rigid surface;(b) gyratory crushers which use agyratory cone to compress lumps against a rigid surface;(c) roll crushers in which ceramic

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lumps are squeezed between rotating rolls;(d) hammer mills which use rotating hammersimpacting the material to break up the lumps.

Figure 5: Various types of crushing processes(Adapted from Groover, Mikell.P., 2010)

3.1.2 Grinding:

It refers transforming the small particles formed after crushing into fine powder. It isaccomplished by abrasion and impact of the crushed mineral by the free motion of unconnectedhard media such as balls, pebbles or rods. Various examples of grinding are (a) ball mill ;(b)roller mill and (c) impact grinding.

Because the strength of new ceramics is more than traditional ceramics, so the starting powdersmust be more homogeneous in size and composition and particle size must be smaller becausestrength of resulting ceramic is inversely related to grain size. So, in this case powder preparationincludes mechanical and chemical methods.

[Adapted from Groover, Mikell.P., 2010]3.2 Powder Processing:

There are two chemical methods used for achieving greater homogeneity in the powders of newceramics which are Freeze Drying and Precipitation from solution. In freeze drying, salts of theappropriate starting chemistry are dissolved in water and the solution is sprayed to form smalldrops which are then rapidly frozen. The water is then removed from drops in a vacuum chamberand the resulting freeze fried salt is decomposed by heating to form the ceramic powders.However, freeze drying is not applicable to all ceramics because in some cases a suitable watersoluble salt cannot be identified as a starting material. In precipitation method, in which thedesired ceramic compound is dissolved from the starting mineral this permitting impurities to befiltered out. An intermediate compound is then precipitated from solution which is thenconverted into desired compound by heating.

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Further preparation of powders includes classification by size and mixing before shaping. Veryfine powders are required for new ceramics applications and so the grains must be separated bysize. There are various additives which are combined with starting powders usually in smallamounts which are; (a) plasticizers to improve plasticity and workability;(b) binders to bondceramic powders into a solid mass in final product;(c) deflocculants which help to preventclumping and premature bonding of powders;(d) wetting agents for better mixing;(e) lubricantsto reduce friction between ceramic grains during forming and to reduce sticking during mouldrelease. Picture of typical powder processing unit is in figure 6:

Figure 6: Set up of Powder Processing Unit

Examples of various additives used are listed below:

Organic Additives Inorganic Additives

PVA Mg-Al silicatesWaxes Soluble silicatesCellulose Colloidal silicaThermoplastic & thermosetting resins Colloidal aluminaLignins ClaysRubbers BentonitesProteins AluminatesBitumens PhosphatesChlorinated hydrocarbons BorophosphatesGelatins

3.3 Shape Forming:

Powder preparation stage is followed by shape forming stage. After grinding and powderpreparation processes, the plastic paste required for shaping consists of ceramic powders and

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water. Clay is usually the main ingredient in the paste because it has excellent formingproperties. Prior to shape forming ceramic powders are mixed with processing additives (binders,plasticizers, lubricants, deflocculants, water etc.). The following techniques are involved informing ceramic powders into a desired shape.

3.3.1 Uniaxial (Die) Pressing:

Die pressing is the powder compaction method involving uniaxial pressure applied to the powderplaced in a die between two rigid punches. Uniaxial (die) pressing is effectively used for massproduction of simple parts (alternative method is isostatical pressing). The scheme of the diepressing method is presented in the figure 7:

Figure 7: Setup of Die Pressing(http://www.substech.com/dokuwiki/doku.php?id=methods_of_shape_forming_ceramic_powders)

The pressing process consists of three stages i.e. Die Filling, Compactation & Green compact partejection removal.

3.3.2 Isostatic Die Pressing:

It is the powder compaction method involving applying pressure from multiple directionsthrough a liquid or gaseous medium surrounding the compacted part. Cold isostatic pressing(CIP) is conducted at room temperature.

A flexible (commonly polyurethane) mould immersed in a pressurized liquid medium(commonly water) is used in the cold isostatic pressing method (see the scheme above). Thereare two types of cold isostatic pressing: wet bag and dry bag.

In the wet bag method the mould is removed and refilled after each pressure cycle. This methodis suitable for compaction of large and complicated parts.

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Figure 8: Setup of Cold Isostatic Processing(http://www.substech.com/dokuwiki/doku.php?id=methods_of_shape_forming_ceramic_powders)

In the dry bag method the mould is an integral part of the vessel. The dry bag method is used forcompaction of simpler and smaller parts.

[Adapted from Substech Substances & Technologies.com]The cold isostatic pressing (CIP) method has the following advantages as compared to the diecold pressing method:

better uniformity of compaction; More complex forms (for example long thin-walled tubes) may be compacted.

3.3.3 Injection Moulding:

Injection moulding is the method of compaction of ceramic powder fed and injected into a mouldcavity by means of a screw rotating in cylinder. The method is similar to the plastic injectionmoulding.This process comprises the following stages:

Mixing the powder with 30% - 40% of a binder – low melt polymer. Injection of the warm powder with molten binder into the mould by means of the screw. Removal of the part from the mould after cooling down of the mixture. Debinding – removal of the binder. There are two debinding methods:

o solvent debinding – the binder is dissolved by a solvent or by water;o Thermal debinding – the binder is heated above the volatilization temperature.

Sintering the “green” compact.

It is widely used for manufacturing small parts having complex shapes. The cycle in this methodis about 10 sec, which much less, than the moulding time in the alternative methods – 10-20 min.

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Figure 9: Typical setup for Injection Moulding Process(http://www.substech.com/dokuwiki/doku.php?id=methods_of_shape_forming_ceramic_powders)

This method permits to produce part with close tolerance, due to the consistent shrinkage. Thisshrinkage is taken into account in the mould design.

3.3.4 Extrusion:

Extrusion ram forces the ceramic paste through a die, resulting in a long product (rods, bars, longplates, pipes) of regular cross-section, which may be cut into pieces of required length. Extrusionis used for manufacturing furnace tubes, thermocouple components, and heat exchanger tubes.

Figure 10: Setup for Extrusion(http://www.substech.com/dokuwiki/doku.php?id=methods_of_shape_forming_ceramic_powders)

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3.4 Drying:

Water plays important role in shaping most of the ceramics during shaping processes. Thereafter,it serves no purpose and water must be removed from the body of the clay piece before firing.Shrinkage is the problem during this step in the processing sequence because water contributesvolume to the piece, and when it is removed, the he volume is reduced. The effect of same can beseen in the figure 8. As the water is initially added to the dry clay, it simply replaces the air in thepores between the ceramic grains and there is no volumetric change. Increasing water contentabove a certain level causes the grains to become separated and the volume to grow, resulting inwet clay that was plasticity and formability. As more water is added, the mixture eventuallybecomes a liquid suspension of clay particles in water.

Figure 11: Changes in Vol. with water Figure 12: Representation of Drying Process[Adapted from Groover.Mikell,P.] [Adapted from Groover.Mikell,P.]

The reverse of this process occurs in drying. As water is removed from the wet clay, the volumeof piece shrinks. The drying process occurs in two stages as shown in figure 9. In the first stage,the rate of drying is rapid and constant as water is evaporated from the surface of the clay intothe surrounding air and water from the interior migrates by capillary action towards the surfaceto replace it. It is during this stage, shrinkage occurs, with the associated risk of warping andcracking leading to variation in drying in different sections of piece. In second stage, themoisture content has been reduced to where the ceramic grains are in contact and little or nofurther shrinkage occurs.

[Adapted from Groover.Mikell,P.]3.5 Sintering ( Firing):

After shaping but before firing, the component is said to be Green means not fully processed ortreated. It lacks hardness and strength, it must be fired to fix the shape and achieve hardness andstrength in the finished ware. Firing is the heat treatment process which sinters the ceramicmaterial; it is performed in a furnace called Kiln. In sintering, bonds are developed in theceramic grains and are accompanied by densification and reduction in porosity. Thereforeshrinkage occurs in polycrystalline material in addition to the shrinkage that has already occurredin drying. Sintering in ceramics is basically the same mechanism as in powder metallurgy. In thefiring certain chemical reactions between the components in the mixture can also occur and aglassy phase also forms among the crystal that acts as binder. Both these facts depend upon thechemical composition of ceramic material and the firing temperatures used.

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Figure 13: Sintering Mill(http://www.ceramics.net/methods/stepthree.html)

In order for ceramic to be hard and dense, they must be "sintered", or fired to hightemperatures for prolonged periods of time in gas or electric kilns. Typical firingtemperatures for alumina, mullite, and zirconia reach 2850 °F - 3100 °F. Typical firing cyclescan range from 12 - 120 hours depending upon the kiln type and product. Ceramics shrinkapproximately 20% during the sintering process.

3.6 After Firing Operations:

There are certain techniques being carried for improving the properties of the ceramics afterthey are sintered. Few of them are diamond grinding, glazing and cleaning.

3.6.1 Diamond Grinding:

Post firing machining may be required to achieve tight tolerances, and surface finishes. Atthis stage ceramic can only be machined with diamonds, so tooling can be costly. Standardmachine shop equipment can be modified with diamond plated or impregnated wheels, drillsand assorted tools, as well as necessary recirculation and filtered coolant systems.

3.6.2 Glazing:

One of the reasons that parts are glazed is to make it easy to remove unwanted residue. Forinstance, spark plugs are glazed to reduce areas of potential arcing in high voltageenvironments. This process involves dipping, brushing or spraying a glass coating onto thesurface of the fired ceramic. The glazed ceramic must then be fired to 1500 °F - 2700 °F tosinter the glazed coating.

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Figure 14: Glazing in progress(http://www.ceramics.net/methods/stepfour.html)

3.6.3. Cleaning:

Most fired alumina ceramics can become dirty through handling, machining or inspecting.These oils, dirt’s and metal marks can be removed using a variety of techniques. Ultrasoniccleaning in mildly acidic or basic solutions at elevated temperatures is commonly done. STCalso offers special cleaning and packaging options which may be desirable for applicationssensitive to contamination.

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4.0 DESIGN

4.1 Engine Block:

The Engine Block is basically a machined casting. It holds engine component like pistons,cylinders and oil pump as well as the crankshaft and camshaft that convert rotating motion toreciprocating motion. It is placed at the bottom of the vehicle. And it is the most importantcomponent of an Engine where all major actions are performed.

Fig 15 - Basic Engine Block

4.1.1 Materials Used and Manufacturing Processes:(http://howautowork.com/part_1/ch_1/Cylinder_block_8.html)

At present, there are two major materials used in the manufacturing of Engine Blocks.

Grey Caste Iron- The use of cast iron blocks has been wide spread due to its low cost aswell as formability. It has a pearlitic structure. Ferrite in the microstructure of the borewall should be avoided because too much soft ferrite tends to cause scratching, thusincreasing blow-by. Cast iron blocks are produced by sand casting. In this case, a steeldie is rarely used .The lifetime of the steel die is not adequate for repeated heat cyclescaused by the melting of iron. Sand casting uses a mould that consists of sand. Thepreparation of sand and its bonding are a critical and very often rate – controlling step.Permanent patterns are used to make sand moulds.

Aluminum and its Alloys- The aluminum block can be both lighter and almost as strongas the cast iron block. In a recent comparison, an aluminum block can attain 40%reduction in weight compared to its cast iron equivalent. The aluminum alloys used forblocks have a thermal conductivity of 150 W/(m · K). Cast iron has a thermalconductivity as low as 50 W/(m·K). The thermal conductivity of aluminum is thereforethree times that of cast iron. Since the Density is 1/3 that of cast iron, aluminum alloy can

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give a high cooling performance at a lower weight. However, it is soft and the wearresistance is generally low. To deal with this problem aluminum alloy blocks withenclosed iron liners are used.

4.2 Silicon Nitride

Right from the 1980’s, research has been going on about using other materials for EngineProduction. And one of the candidates has been ceramics, for its workability within a hightemperature change, its reduced heat loss properties and higher efficiency.With this regard, Silicon Nitride has received most attention in the field of ceramics with regardto application in I.C.Engines. This is primarily because of its high creep resistance and thermalshock resistance. Silicon nitride (Si3N4) was developed in the 1960s and '70s in a search forfully dense, high strength and high toughness materials. A prime driver for its development wasto replace metals with ceramics in advanced turbine and reciprocating engines to give higheroperating temperatures and efficiencies [2].

4.2.1 Production

Pure silicon nitride is difficult to produce as a fully dense material. This covalently bondedmaterial does not readily sinter and cannot be heated over 1850 degrees C as it dissociates intosilicon and nitrogen. Dense silicon nitride can only be made using methods that give bondingthrough indirect methods, such as small chemical additions to aid densification. These chemicalsare known as sintering aids, which commonly induce a degree of liquid phase sintering.Some of the commonly used techniques of production are:

(http://www.azom.com/details.asp?ArticleID=53)

By Carbothermal Reduction in nitrogen atmosphere at 1400–1450 °C

3 SiO2(s) + 6 C(s) + 2 N2(g) → Si3N4(s) + 6 CO(g)It is the earliest used method for silicon nitride production. It is also considered as themost-cost-effective industrial route to high-purity silicon nitride powder.

By diimide synthesis.SiCl4(l) + 6 NH3(g) → Si(NH)2(s)+ 4NH4Cl(s) at 0 °C

3 Si(NH)2(s) → Si3N4(s) + N2(g) + 3 H2(g) at 1000 °C

It results in the production of amorphous silicon nitride, which needs further annealingunder nitrogen at 1400–1500 °C to convert it to crystalline powder. This process is thesecond best process with regard to commercial production.(Journal of the American Ceramic Society)

Obtained by direct reaction between Silicon and Nitrogen at temperatures between 1300and 1400 °C [3]

3 Si(s) + 2 N2(g) →Si3N4(s)

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5.0 PERFORMANCE OF A CERAMIC ENGINE BLOCK

5.1 Metal Engines Block:Over a century engines are manufactured using metals. The selection of metals of an engine is anunfortunate one because metals are low temperature materials when compared to ceramicmaterials and they are good thermal conductor’s combustion efficiency and thermal efficiencydepends on these two properties.Recognizing this problem research is being done to develop a new material for engines. Becauseof the above mentioned properties of the metals the engine efficiency is reduced.The maximum operating temp of the metal engines is less when compared to ceramics it isaround 600o c. So the metal engine is required to operate in low temperature conditions. Thistemp is low for the fuel to burn completely thus the incomplete combustion of the fuel causeslow combustion efficiency and the incomplete burnt fuels will mix with exhaust gases and causespollution.There is a loss of 20% energy generated for overcoming the friction and wearing of the parts aremore likely in metal engines. So we have to overcome this problem because this problem willdecrease the efficiency and life of the engine parts.

(http://www.fueleconomy.gov/feg/atv.shtml)The metals are good thermal conductors this property makes the heat generated in thecombustion chamber is easily conducted from the engine. Thus liquid cooling system is requiredfor metal engines to avoid over heating of the engine (over 30% of the heat generated is carriedout by the coolant) and this will lead to in complete combustion of the fuel.This heat loss in metal engines will lead to low thermal efficiency and low combustion efficiencyof the engine thus metallic engines have three major problems low thermal efficiency and lowcombustion efficiency, heat loss and wearing of the metal parts in relative motion reducing lifeof the parts.

5.2 Ceramic Engine Block:Ceramic materials are high temperature materials when compared to metal the maximumoperating temp of the ceramic materials are around 1600o c and ceramics are not good thermalconductors. This enables engine to work at high temperatures thus the combustion of the fuelwill be more complete. As ceramic materials are not good conductors of heat thus the coolingsystem is not required for this kind of engines this in turn reduces the weight and powerconsumption of the engine.High temp working property of the ceramic engine will enable the fuel to burn more completelyso this will increase the combustion efficiency of the engine. As the ceramic materials are notgood conductors of heat the thermal efficiency of the material will increase. If fuel is burntcompletely the fuel combustion will increase. And also enable using of the various other fuels asthe engine can work at high temperatures.In ceramic engine wearing of the parts is less when compared to the metal engines and thefriction is less so there is no loss of energy in overcoming friction.No heavy coolant is required for the engine as the material is not a good conductor of heat. If theengine is modified and the exhaust gases and sent in to the chamber with the fuel then a thinlayer of graphite is formed this layer of graphite acts as a coolant and lubricant for the engine.This enables us to remove cooling system and thus weight of the engine is reduced.

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Figure 16 - Operating temp of metals and ceramics(Ceramic Materials: Processes, Properties, and Applications, Philippe Boch)

Thus using ceramic materials for manufacturing engines will have advantages like improvedcombustion efficiency and thermal efficiency, no heat loss and less wearing of the engine parts.

Loses we can cover in Ceramic Engine Block: Friction Inefficient combustion Heat loss from combustion chamber.

Pollution:Pollution is caused by in complete combustion of the fuel because of the heat loss in metalengines.In ceramic engines modification of the engine is done such that the hot exhaust gases are used topreheating of the fuel so that the fuel will reach its fire point quickly and this enables the fuel toburn completely. By this the combustion efficiency of the engine will increase and decrease inpollution.

Environmentally Friendly Engine:Because of the high operating temp property the ceramic engine is capable of using various otherfuels like cellulosic bio-ethanol and straight vegetable oils. In rural communities and villagesceramic engine is a portable power source using SVO for water pumping in irrigation and manyother purposes and could power electric generators used for lightning and cooking this enablesthe reduce of usage of wood indeed will reduce cutting of trees.

(http://ceramicrotaryengines.com/)

Some Useful Studies:In 1980, in development program at ford motors led by Dr McLean testing of Zirconium-basedceramic components been done in reciprocating internal combustion engine. Testing is done on

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80 mm bore by 80 mm stroke, high speed direct injection diesel engine at full load over completespeed range. Result shown was fuel consumption of un cooled engine is reduced by 5% to 9%.In diesels, it is reported that coating cylinder head with 1mm and 2mm coating on the piston capwill reduce the heat loss into the coolant by 9%.

(W.Bunk and H.Hausner 1986 Proceedings of the Second International Symposium)Dr Alan Bentz of the Energy Institute at Pennsylvania State University stated that when athermal barrier ceramic coating is applied mass reduction and composition change in emissionand peculate mass reduction is observed. he said that the coating enhances the oxidation ofcondensable hydrocarbons that agglomerate with the diesel soot

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6.0 MARKET ANALYSIS

6.1 Conventional Engine Block:

The engine blocks in current market are made of materials like grey cast iron and aluminumalloys. The block is machined by casting the material to required shape. The cost of the materialsused in manufacturing engine block is found to be £1 - £2 per/kg commercially available (CESEDU Pack). The cost of the engine block which is manufactured by a MED Engineering inLEICESTER, UNITED KINGDOM is found to be £280. [MED Engineering, 2005]

Fig 17 - Fully Prepared Engine Block(http://www.med-engineering.co.uk/product_details.php?p_id=283&vlang_id=327)

Bored and honed to size, refaced to customers request, supplied and fitted with new camshaftbearings, drilled and tapped for 11 stud head fixing, machined for centre main strap and suppliedwith extra long H/T bolts, supplied with new oil way and core plugs, acid dipped and pressurewashed, painted and in other words fully prepared ready for assembly. [MED Engineering, 2005]

The conventional engines are expected to give an overall efficiency of 20 – 40 % and the heatrejection is as high as 70 – 90 %. [Jaichandar and Tamilporai, 2003].

The lifespan of conventional engine block is expected around 200,000 to 300,000 miles. Thismight vary according to conditions under which it is used. The grey cast iron blocks have higherlifespan as they are thicker and heavier than the aluminum alloy made. Due to the above reasonthe cast iron were able to resist heat and various wears caused due to movable parts for longerperiod when compared with aluminum alloys. The weight to power ratio is high when aluminumalloys are used, the reason why most of the passenger cars manufacturers nowadays usealuminum alloys for manufacturing engine blocks.

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6.2 Ceramic Engine Block:The ceramic material chosen for manufacturing engine block is silicon nitride. Silicon nitride ischosen because of its high thermal conductivity, forming the material is easier when comparedwith other ceramics and this material resists fracture well than other ceramic materials.

[Ashley, Steven, 1992]

The cost of commercially available silicon nitride material is found to be £15 - £18 per/kg, [CESEDU Pack]. The cost of producing ceramic components is high and is expected to be aroundthrice the original cost of the conventional metal components. Ceramics when manufactured tothe required shape becomes very hard. This property makes them unfit for machining them oncethe desired shape is manufactured. To machine ceramics, tools made of polycrystalline diamondhas to be used which once again increases the cost of producing the component.

6.3 Cost Benefit Analysis

Fig 18 - Cost Benefit Analysis6.3.1 Weight ReductionOne of the main contributors of weight for conventional metal engines is liquid cooling systemwith radiator, coolant storage, pumps and pipes. Reducing this weight will increase efficiency ofthe engine. Since ceramics are materials operating at very high temperature the engine doesn’tneed a heavy cooling system as needed by the conventional engines. [Ashley, Steven, 1992]

6.3.2 PerformanceAbout a third of the heat generated by an internal combustion engine is lost to its surroundings.The engine block made of ceramic material will reduce heat loss. This helps in complete burningof the fuel rather than incomplete combustion. This reduces pollution in the vehicle as the fuel iscompletely burnt. This automatically increases the efficiency of the engine.

[Jaichandar and Tamilporai, 2003]

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6.3.3 Life spanThe ceramic materials are the ones having very less friction between them. Due to the abovereason the wear resistance is high and the ceramic do not wear that sooner as the metals do. Thelife expectancy of the component is expected to be high in comparison with metals.

[Ray Walker, 2008]The cooling, in other words lubrication for movable parts inside the engine block is provided bythe exhaust gases. The exhaust gases are sent back again in to the combustion chamber wherethey are heated due to surrounding temperatures, this in turn forms a graphite layer which is 0.1micrometers thick and which acts as a lubricating material for the reciprocating parts inside theengine. [Ashley, Steven, 1992]

7.0 Conclusion:

To conclude we can say that commercialization of ceramic engine blocks can bring revolutionaryimpact in the Global Automotive Industry. Such efficient systems will provide a strong answer toincreasing prices and fast depleting sources of petrol and diesel. Since, there are less frictionallosses in case of ceramics, so this will definitely enhance the overall life of the product. But thereare some practical problems still left like the higher costs of commercially available ceramics(Silicon Nitride) as well as production techniques which are very complex due to which theoverall time and process cost increases.

Cars of the future may have ceramics in internal engine structural parts; in wear-resistantapplications in fuel systems; and in additional components in valve trains, such as valves andvalve seats. Futuristic cars also may use ceramic fuel cells for near-emission-free operation.

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References:

Properties of Ceramics

http://www.azom.com/details.asp?ArticleID=53http://www.ms.ornl.gov/programs/energyeff/cfcc/iof/chap21-2sin.pdfhttp://www.accuratus.com/silinit.htmlhttp://americas.kyocera.com/KICC/industrial/types.html

Manufacturing of Ceramics:

Groover, Mikell.P., 2010. Fundamentals of Modern Manufacturing: Materials Processes &Systems.4th ed. New Jersey: John Wiley & Sons.

STC Superior Technical Ceramics Corp., 2001. ‘Manufacturing Methods’ [online].http://www.ceramics.net/methods/Date Accessed: 15 May 2010.

Substech Substances & Technologies.2009, ‘Method of Shape forming of Ceramics’ [online]http://www.substech.com/dokuwiki/doku.php?id=methods_of_shape_forming_ceramic_powdersDate Accessed: 14 May 2010.

Heinrich & Aldinger, 2001. Ceramic Materials and Components for Engines. Weinheim:Wiley-VCH

Design:

http://howautowork.com/part_1/ch_1/Cylinder_block_8.htmlhttp://www.azom.com/details.asp?ArticleID=53Journal of the American Ceramic Society Volume 83 Issue 2, Pages 245 – 265

Performance:

Ceramic Materials: Processes, Properties, and Applications. Autores: Editor: Philippe Boch (University Pierre & Marie Curie, Paris, FranceCeramic materials: science and engg By C. Barry Carter, M. Grant NortonCeramic materials and components for engines: proceedings of the third internationalsymposium, Las Vegas, Nevada, U.S.A., November 27-30, 1988, Volume 1988W.Bunk and H.Hausner 1986 Proceedings of the Second International Symposium; 14 to17 April, Lubeck-Travemunde, Germany "Ceramic Materials and Components for Engines".S.Jaichandar and P.Tamilporai 2003 SAE Technical Paper Series 2003-01-0405 "Low HeatRejection Engines - An Overviewhttp://www.fueleconomy.gov/feg/atv.shtmlhttp://ceramicrotaryengines.com/

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Market Analysis:

MED Engineering, 2005. Fully prepared cylinder block [online]. Available from:http://www.med-engineering.co.uk/product_details.php?p_id=283&vlang_id=327 [Accessed 30Apr 2010].

Jaichandar, S., Tamilporai, P. 2003. "Low Heat Rejection Engines - An Overview”, SAETechnical Paper Series 2003-01-0405.

Ashley, Steven, 1992. Lubricating ceramic engines with exhaust, Mechanical Engineering-CIME.

Ray Walker, 2008. Ceramic rotary engines [online]. Available from:http://ceramicrotaryengines.com/ [Accessed 28 Apr 2010].