Unit-3 Notes PDF

# UNIT-III PHASE RULE ## State phase rule and Explain the terms involved in it. ### Phase rule If the equilibrium between any no. of phases is not influenced by gravity or electrical or magnetic forces but is influenced only by pressure, temperature, concentration, then F of the system is related t...

# UNIT-III PHASE RULE ## State phase rule and Explain the terms involved in it. ### Phase rule If the equilibrium between any no. of phases is not influenced by gravity or electrical or magnetic forces but is influenced only by pressure, temperature, concentration, then F of the system is related to 'C' and 'p' by the following **Phase rule equation**: $F = C - P + 2$ where * F= No. of degree of freedom * C= No. of components * P= No. of phases ### Phase(P) Any homogeneous, physically distinct, mechanically separable portion of a system which is separated from other parts of the system by definite boundaries. **EX**: 1. Gaseous phase - O2, H2, N2, CO2 (P=1) 2. Liquid phase - Benzene-water, Alcohol-water, (P=2) 3. Solid phase - Decomposition of CaCO3 (P=3) ### Components (C) "The smallest no. of independently variable constituents, by means of which the composition of each phase can be expressed in the form of a chemical equation." **EX**: 1) Ice(s) = Water (l) Water (V) (C = 1) 2) CaCO3 (CaO (s) + CO2 (g) (C = 2) ### Degree of freedom The minimum no. of independent variable factors such as T, P, S concentration, which must be fixed in order to definite the System completely. **EX**: water (l) water (V) (P=2) - F=0 => Non-variant System - F = 1 => Uni-variant System - F=2 => Bi-variant System. - F=C-P+2 = F=2-1+2=F=1 => Uni-variant System. ## Describe the phase diagram of water system. (one component system) ### Applications of phase rule-one Component (water) System. ### Phase rule: $F=C-P+2$ Where * F = No. of degree of freedom * C= No.of Components * P = No. of phases. Water is a one component system which is chemically a single compound involved in the System. Water exists in 3 possible phases namely solid, liquid and Vapour. The phase diagram of water System consists of * **Curves** - curve OA, OB, OC - Stable Curves * **Area** - curve AOB, BOC, AOC - metastable curves * **Triple point** - Point 'o' * **Solid Liquid** (OC) * **Liquid Vapour** (OA) * **Vapour** (DB) * **Solid** ## 1. Curve OA The curve OA is called Vapourisation curve of Ice. Water (l) => Water (V) * P=2 * C=1 $F=C-P+2 = 1-2+2= 3-2=1$ => Uni-Variant system Beyond the critical temperature (374°C), the equilibrium will disappear and water (V) will exist ## 2. Curve OB The curve OB is called sublimation curve of Ice Ice(s) => Water (V) * P=2, * C=1 $F=C-P+2 = 1-2+2= 3-2=1$ => uni-variant System The lower end of the curve OB extends upto the absolute zero (-273°C). Only Ice will exists. ## 3. Curve Oc The Curve OC is known as melting point curve of Ice. Ice(s) => water (l) * P=2 * C=1 $F = c-p+2 = 1-2 +2 = 3-2 = 1$ => Uni-variant System. ## 4. Curve OB' The curre OB' is known as Metastable Equilibrium - Super cooled water <=> Vapour When water is cooled Carefully below 0°C without the formation of Ice, then the water is known as Super cooled water. ## 5. point 'o' (Triple point) The three curves OA, OB and oc meet at a point 'o' which is called a Triple point Ice(s) = water(l) Water(g) * C=1, P=3 $F =C-P+2$ $F=1-3 +2$ $F=0$ => Non-Variant System. ## 6. Areas Certain regions which are formed between the curves are called Areas | Area | Phase Exists | Component | |---|---|---| | Aoc | Water (l) | H2O | | Boc | Ice(s) | H2O | | AOB | Water (v) | H2O | Thus, every area contains, C=1, P=1 $F=C-P+2]$ $=1-1+2$ $F = 2$ => Hence, each area is a bivariant System ## Draw & label the phase diagram of Pb-Ag system. Explain. ## Reduced on condensed phase rule A System in which only the Solid &liquid phases are considered and the gas phase is ignored is called a condensed system. Since the pressure is kept constant. $F' = C-P+)$ This is known as Reduced phase rule Where * F' = No. of degree of freedom, * C= No-of components * P = No. of phases. ### Two component System (on the Lead-Silver System The Pb-Ag System has two components and Three phases: 1. Solid Silver 2. Solid Lead 3. melt The T-C Phase diagram consists of ⅰ) Touo curves - AOSBO - ⅱ) Eutectic point ('0') a) Above AOB b) Below AO, во c) Three areas ## 1) Curves ### ⅰ) Curve Ao The curve Ao is known as Freezing point curve of Ag. $Ag(s) = 961°C$ Curve AO - the melting point of Ag' is lowered by Successive addition of Pb * Solid Ag => melt => liquid * C=2 * P=2 $F'=C-P+1$ $= 2-2 +1 = 3-2$ $F = 1$ => Uni-variant System. ## ⅱ) Curve BO The curve Bo is known as Freezing point curve of lead. $Pb = 327°C$ Curve Bo-melting point of Pb is lowered by Successive addition of Ag. * Solid pb => liquid => melt * C=2 * P=2 $F'=C-P+1$ $= 2-2+1$ $F = 1$ => Uni-variant System. ## i) point'o' (Eutectic point) The curves Aos Bo meet at point 'o' at a temperature of 303°C, where the 3 phases namely, solid Ag, Solid Pb and liquid melt are in equilibrium. This point is known as Eutectic point. * Solid pb + solid Ag => liquid melt * C=2 * P=3 $F'=C-P+1$ $= 2-3 +1$ $=3-3$ $F' = 0$ => Non-Variant system ### C) Areas 1) Above AOB - Single phase system * C=2 * P=1 $F'=C-P+1$ $= 2-1+1$ $F' = 2$ => Bi-variant System. ii) Below AOS BO * Below AO) Solid Ag = melt * Below Bo =) solit po = melt * C=2 * P=2 $F=C-P+1 =) F' = 2-2 + 1 = F=1]$ => uni-variant System. ## Applicatication of pattinson's process for the desilverisation of Argentiferrous Lead The process of raising the relative proportion of Ag in the alloy is known as pattinson's process. * (point Preached) Cooling * (point Preached) Cooling * (point" pq! Ag proportion increases from 0.1 to 2.6% alung alo the Curve 'OB reached) Cooling 2.6 %. Ag+ 9+97.4 97.4 Y. Y. pь ## UNIT-III COMPOSITES ### Definition Composites (or) composite materials "A material system consisting a mixture of two (or) more micro-constituents, which are mutually insoluble, differing in form (or) Composition and forming distinct phase!"!" ### Need for composites * As composites never rust and have less fracture toughness than metals. * To reduce maintenace cost. * It is essential because according to the needs, using different of composities can be modified. * Lower weight reduces fuel consumption emission. * In telecommunication industries, need of power transmission along with data tremsmission is increasing, so composites are highly essential. * As Carbon fibre weights about 25% as much as Steel and 70 y, as much as Al and is much Stronger and stiffer than both materials, we need Composites. ### Advantages (or) Characteristics of composites * Higher specific strength and Lower specific gravity, * Lower electrical conductivity and thermal expansion, * Better creep, fatigue Strength, Corrosion, &oxidation resistance., * They maintain very good strength, even upto high temperatures. ### Constituents of Composites 1. **Matrix phase** (or) Matrix resin 2. **Dispersed phase** (or) Reinforcedment. ### ⅰ) matrix phase Matrix phase is the continuous body Constituent, which enclose the composite. Matrix phase may be metal, ceramics, polymers. composites using these matrix are know as MMC, CMC, PMC * i) metal matrix composites (MMC) * ii) ceramic matrix composites (cmc) * iii) polymer matrix composites (PMC) ### Liquid Resins polymers used as adhesives, potting compounds, Sealants etc., in a liquid form are called as Liquid resins. **EX: Epoxy adhesives, polysulphides.** ### Dispersed phase (or) Reinforcement Disphersed phase is the structural constituent, which determines the internal structure of composite. **Ex: 1. Fibres 2. Particulates 3. Flakes. 4. whiskers** ### Reinforcement * "It is a process of improving the characteristics of the plastic matrix buy adding reinforcing agents. The reinforcing agents may be organic, or Inorganic in nature. * They may be in the form of powder, Flakes; Fibres. * These materials are characterised by high strength, Excellent resistance to erosion, Corrosion. ### Fibres **Definition** Fibres are long and then filament of any macromolecular Substance such as polymer, metal or ceramic having high length to diameter ratio at least 100:1 ### Uses of Fibres used in variety of forms like continuous rovings, cloth, chopped strands etc., ### Characteristics of Fibre * High tensile Strength * High stiftness. * Lowers over all density of composites. ### Classification of fibres * **Natural Fibres** (derived from naturally available materials) * EX: * 1)cotton * 2) wool * 3) silk * 4) sisal * 5) Jutes * **Semi-Synthetic Fibres** (producet by modifying naturally occurs) * EX: * 1) Rayon * ii) cellulose * **Synthetic Fibres** (producet by the Loch processes) * EX: * 1) PAN * ii) polyester fibres * iii) erlass Fibres * iv) Aramid Fibres * **Aramid fibres.** (Aromatic Polyamides) * EX: * i) Nomex * ii) kevlar ### Dispersed phase (or) Reinforcement ⇒ Dispersed phase is the structural constituent, which determines the internal Structure of composites. **Ex: 1) Fibres 2) Particulates 3) Flakes 4) whiskers** * **Fibres** - long sthin filament of any macromolecular Substance - polymer, metal (or) ceramic materials. * **Particulates** - Small pieces of hard solid materials. - metallic (or) non-metallic materials. * **Flakes** - very thin solid like materials. - Ex: mica flake * **whiskers** - Thin Strong fibre like material made by growing a crystal. - EX: 1) Graphite, 2) sic, etc., ### Types of composites (or) Fibre Reinforced polymer Composites. ## FRP "A matrix of polymeric material that is reinforced by fibres (or other reinforcing material". FRP = Fibre Reinforced polymer. ### preparation of FRP * matrix phase + Dispersed phase => Composites * Temperature * Pressure * Matrix phase + Dispersed phase => FRP * Temp. * Pressure **Ex: polyesters, Epoxy, phenolic, silicone, polyamide** **Ex: Fibre, Flakes, Particulates** ### properties (or) characteristics of FRP * It possess superior properties like higher yield strength, fracture Strength and fatigue life. * It prevents slip and crack propagation-mechanical properties of FRP gets increased. * It possess high corrosion resistance * Heat resistance property. ### Resin Reason * polyester resin very good Strength & mechanical properties. * Epoxy resin Good mechanical properties * Silicone resins Excellent thermal & electrical properties. * Phenolic resins To withstand high temperatures. * Thermoplastics Repeatability and repairability. (polyamide, PET etc., ### Types of FRP composites | S.No | Name of FRP | properties | Application | |---|---|---|---| | 1 | Glass-FRP | * Lower densities * Dielectric constants - Lower * Higher tensile strengths & impact resistance. * Excellent corrosion resistance * Chemical resistance * Non-flammability. | * Automobile parts * Storage tanks * plastic pipes * Industries, Flaurings * Transportation | | 2 | Boron-FRP | * Excellent stiffness& Compressive Strength. * manufacturing of B-FRP is difficult. | * Horizontal & vertical tail in aeroplane * Stiffening Spares * Ribs | | 3 | Carbon-FRP | * Lighter density * Excellent resistance to corrosion * Retention of desired properties even at elevated temperatures. | * Structural components of aircraft and Helicopters * Recreational equipments * sports materials. * Antenna disc * Solar panal | | 4 | Aramid-FRP | * Metal-like ductile &respond non-catastrophically to Compressive stresses. | * Structural Component in aircraft * Helicopter parts. | | 5 | Alumina-FRP | * Good abrasion resistance * Creep resistance * Dimensional Stability. | * Components of Engine parts in automobile industry. * Components of turbine engine. | ### Advantages of polymer Composites (FRP) * very high strength to weight ratio than the metal. * The weight of FRP is 75 %. than the weight of Steed. - Improves performance - reduce energy need, Simplifiées handling * Using polymer composite devices both capacitance & leakage Current can be reduced. * Better corrosion resistance to a wide range of Chemicals - longer service life - less maintenance - repair down time. * It is ideal for outdoor installation - impervious to the effect of sunlight - Heat, cold Sother weather conditions. * It possesses Excellent durability & fire resisting properties. * GRP (Glass reinforced polymer) are strongest and most resistive to deforming forces. * CRP (Carbon fibre reinforced polymer) in place of Sheet Al i) 25% oreduction in weight. iⅱ) 95% reduction in components by combining parts & forming Simpler moulded parts. ### Metal matrix composites (MMC) ## Properties of MMC * It is extremely good thermal stability, good stiffness. * It is low specific weight. * It is high fracture toughness, ductility. * They can withstand at high temperature in corrosive environment than polymer composites. ### Uses of metal matrix composites * It is mainly used in engine parts. * They are used in engine blades, combustion chambers etc. * Al and Mg MMCs are used in automotive industry. * They improve fuel efficiency, because of the weight reduction. * It is used in biomedical industry. * It is used in equipment industry. ### Ceramic matrix composites (cmc) ### Properties of CMC * It is used at temperature above 1500°C * Good corrosion resistance * Stability at elevated temperature & high compressive Strength. * Ceramics provide necessary strength at high temperature with good oxidation resistance. * The matrixes used are glass, ceramics, carbides, nitrides, oxides & borides, the reinforcements are Al2O3, B, C, Sic and sioz. ### USES of CMC * Used in re-entry thermal shields in space Vehicles and tiles. * used in pump seal * used in round rings * used in brake linings. ### Hybrid composites ### Definition Hybrid composites are new class of materials composed of a Switable polymer matrix reinforced with two different fibres (or) Fillers. ### Types of Hybrid composites * Structurally Hybridized Composites * Materials hybridized in chemical bund * Functionally hybridized Composites ### properties of Hybrid composites * very good properties compared to their Single Fibre composites * They possess strong, tough and higher impact resistance * They are stressed in tension, failure does not occur Suddenly * They possess balanced Strength and stiffness. * Balanced thermal distortion Stability, reduced weight, improved fatigue resistance. * They exhibit superior mechanical & tribological properties than other composites. ### USES of Hybrid composites * used in light-weight transport structural components. (Land, water on oil) * used in light-weight orthopedic components & Sporting goods. * used to make furniture like chair, tables bath rubs. * used in railway coach interiors. * used as a plates and spoons. * It is mainly used in Automobile industry. ### Thermal Analysis (or) Cooling curves ### Definition Thermal Analysis is a method involving a study of the cooling curves of various compositions of a system during solidification. ### Example 1. cooling curve for a pure solid 2. Cooling curve for a mixture of solid. ### 1. P-T diagram If the phase diagram is plotted between temperature agamst pressure, the diagram is called P-T diagram. It is used for one component System. ### 2. T-C diagram If the phase diagram is drawn between temperature against composition, the diagram is called T-C diagram. It is used for two component system. ### Uses of phase diagram * It is possible to predict from the phase diagrams whether an eutectic alloy is formed on cooling a homogeneous liquid Containing mixture of two metals. * They are useful in understanding the properties of materials in the heterogeneous equilibrium System. * The study of low melting eutectic alloys, used in soldering ### Uses (or) merits of phase rule * It is applicable to both physical & Chemical equilibria. * It is a convenient method of classifying the equilibrium States in terms of P, C and F. ### Limitations of phase rule * Phase rule can be applied only for the systems in equilibrium. * All the phases of the system must be present under the same conditions of pressure & Temperature.