The document discusses the process of solid state sintering. It covers various sintering mechanisms like surface diffusion, lattice diffusion, and grain boundary diffusion. It describes the three stages of sintering - initial, intermediate and final. The initial stage involves rapid neck growth between particles through different mechanisms. The intermediate stage involves the development of continuous porosity along grain edges. During the final stage, isolated pores form at grain corners and gradually disappear. The document also presents kinetic equations to model neck growth and densification during the different sintering stages. It provides scaling laws relating sintering rates with particle size based on the dominant diffusion mechanism. Geometrical models are used to represent the microstructural changes during intermediate and final
The document summarizes key concepts in solid-state sintering including:
1) Sintering involves forming solid bonds between particles through heating without melting. Mass transport mechanisms like surface diffusion, grain boundary diffusion and plastic flow cause densification and coarsening.
2) Sintering progresses through initial, intermediate and final stages characterized by neck growth, pore rounding and grain growth respectively.
3) The dominant mass transport mechanisms depend on factors like temperature, particle size and material properties, and influence the rate of densification and grain growth.
The document discusses the process of sintering, which involves heating powdered materials below their melting point to bond particles together through atomic diffusion. Sintering reduces porosity and improves material properties. It explains the stages of sintering - initial neck growth, intermediate pore channel closure, and final pore shrinkage. Different sintering mechanisms are described, including surface, grain boundary, and lattice diffusion. Solid-state, liquid-phase, and reactive sintering types are also summarized. Key sintering parameters and the advantages and disadvantages of the process are presented.
Sintering is a process where ceramic powders are heated below their melting point to increase strength through bonding particles. It involves removing pores through densification and grain growth. There are different types including solid-state, liquid-phase, and reactive sintering. The driving force is reducing surface area and energy. Key factors that influence sintering are particle size, packing, and shape. The process occurs in stages from initial bonding to closing and eliminating pores, with final grain growth. Additional pressure in hot pressing and hot isostatic pressing enhances densification. Sintering allows shaping complex geometries of high-melting materials while maintaining purity and good properties, though it requires high temperatures and capital costs.
The document summarizes key concepts in solid-state sintering including:
1) Sintering involves forming solid bonds between particles through heating without melting. Mass transport mechanisms like surface diffusion, grain boundary diffusion and plastic flow cause densification and coarsening.
2) Sintering progresses through initial, intermediate and final stages characterized by neck growth, pore rounding and grain growth respectively.
3) The dominant mass transport mechanisms depend on factors like temperature, particle size and material properties. Data analysis of sintering kinetics helps determine the controlling mechanisms.
Sintering is a process that uses heat to consolidate powder materials into a solid form without melting them. There are three main stages of sintering: initial bonding and neck formation between particles, densification and pore shrinkage, and final grain growth. The driving forces for sintering include reducing surface curvature, applied pressure, and chemical reactions. Key parameters that affect sintering include powder properties, consolidation method, firing temperature and atmosphere. The main mechanisms are surface, lattice, and grain boundary diffusion which allow atoms to migrate and bonds to form between powder particles over time.
This document discusses creep deformation, which is the time-dependent plastic deformation of materials under constant stress, especially at elevated temperatures. It defines creep and identifies the primary mechanisms as bulk diffusion, grain boundary diffusion, and dislocation climb/creep. The document details experimental creep tests to determine creep rates and parameters, which provide prediction of life expectancy. It also discusses design considerations like reducing grain boundaries and employing high melting temperature materials to minimize creep deformation.
The document discusses the process of solid state sintering and densification of ceramic materials. It covers mechanisms of mass transfer such as evaporation-condensation and surface diffusion that allow for elimination of porosity. The driving force for densification is decreasing surface area and surface free energy by reducing curvature at the solid-solid interface. Grain growth is a concern during firing as excessive growth can harm mechanical properties.
Mumbai University
Mechanical engineering
SEM III
Material Technology
Module 1.4
Strain Hardening:
Definition importance of strain hardening, Dislocation theory of strain hardening, Effect of strain hardening on engineering behaviour of materials, Recrystallization Annealing: stages of recrystallization annealing and factors affecting it
The document summarizes key concepts in solid-state sintering including:
1) Sintering involves forming solid bonds between particles through heating without melting. Mass transport mechanisms like surface diffusion, grain boundary diffusion and plastic flow cause densification and coarsening.
2) Sintering progresses through initial, intermediate and final stages characterized by neck growth, pore rounding and grain growth respectively.
3) The dominant mass transport mechanisms depend on factors like temperature, particle size and material properties, and influence the rate of densification and grain growth.
The document discusses the process of sintering, which involves heating powdered materials below their melting point to bond particles together through atomic diffusion. Sintering reduces porosity and improves material properties. It explains the stages of sintering - initial neck growth, intermediate pore channel closure, and final pore shrinkage. Different sintering mechanisms are described, including surface, grain boundary, and lattice diffusion. Solid-state, liquid-phase, and reactive sintering types are also summarized. Key sintering parameters and the advantages and disadvantages of the process are presented.
Sintering is a process where ceramic powders are heated below their melting point to increase strength through bonding particles. It involves removing pores through densification and grain growth. There are different types including solid-state, liquid-phase, and reactive sintering. The driving force is reducing surface area and energy. Key factors that influence sintering are particle size, packing, and shape. The process occurs in stages from initial bonding to closing and eliminating pores, with final grain growth. Additional pressure in hot pressing and hot isostatic pressing enhances densification. Sintering allows shaping complex geometries of high-melting materials while maintaining purity and good properties, though it requires high temperatures and capital costs.
The document summarizes key concepts in solid-state sintering including:
1) Sintering involves forming solid bonds between particles through heating without melting. Mass transport mechanisms like surface diffusion, grain boundary diffusion and plastic flow cause densification and coarsening.
2) Sintering progresses through initial, intermediate and final stages characterized by neck growth, pore rounding and grain growth respectively.
3) The dominant mass transport mechanisms depend on factors like temperature, particle size and material properties. Data analysis of sintering kinetics helps determine the controlling mechanisms.
Sintering is a process that uses heat to consolidate powder materials into a solid form without melting them. There are three main stages of sintering: initial bonding and neck formation between particles, densification and pore shrinkage, and final grain growth. The driving forces for sintering include reducing surface curvature, applied pressure, and chemical reactions. Key parameters that affect sintering include powder properties, consolidation method, firing temperature and atmosphere. The main mechanisms are surface, lattice, and grain boundary diffusion which allow atoms to migrate and bonds to form between powder particles over time.
This document discusses creep deformation, which is the time-dependent plastic deformation of materials under constant stress, especially at elevated temperatures. It defines creep and identifies the primary mechanisms as bulk diffusion, grain boundary diffusion, and dislocation climb/creep. The document details experimental creep tests to determine creep rates and parameters, which provide prediction of life expectancy. It also discusses design considerations like reducing grain boundaries and employing high melting temperature materials to minimize creep deformation.
The document discusses the process of solid state sintering and densification of ceramic materials. It covers mechanisms of mass transfer such as evaporation-condensation and surface diffusion that allow for elimination of porosity. The driving force for densification is decreasing surface area and surface free energy by reducing curvature at the solid-solid interface. Grain growth is a concern during firing as excessive growth can harm mechanical properties.
Mumbai University
Mechanical engineering
SEM III
Material Technology
Module 1.4
Strain Hardening:
Definition importance of strain hardening, Dislocation theory of strain hardening, Effect of strain hardening on engineering behaviour of materials, Recrystallization Annealing: stages of recrystallization annealing and factors affecting it
This document discusses various polymer processing techniques. It begins by outlining three general phases of plastics processes: heating, shaping/forming under constraint, and cooling. It then describes specific processes like thermoforming, compression and transfer molding, rotational molding, extrusion and extrusion-based processes, injection molding, and blow molding. For each process, it provides details on how it works, its advantages and disadvantages, and common applications.
Griffith proposed that brittle materials contain small cracks and flaws that concentrate stress enough to reach the theoretical strength at nominal stresses below theoretical values. For a crack to propagate, the decrease in elastic strain energy from crack growth must be equal to or greater than the increase in surface energy. Griffith established a criterion where the stress required for crack propagation is inversely proportional to the square root of the crack length. This theory provides an equation to calculate the maximum crack length possible without fracture given a material's surface energy, modulus of elasticity, and applied stress.
Recrystallization is the process in which deformed grains of the crystal structure are replaced by a new set of stress-free grains that nucleate and grow until all the original grains have been consumed. The process is accomplished by heating the material to temperatures above that of crystallization.
The document discusses rate controlled sintering in advanced ceramic processes. It explains that sintering transforms ceramic powder compacts into dense materials through heating by reducing pores and growing grains. The driving force is lowering free energy. Sintering occurs in three stages and is affected by various factors. Rate controlled sintering controls the heating rate or temperature to control the sintering process for improved material properties. It provides examples demonstrating the effects of heating rate on microstructure.
The document discusses sintering, which is a thermal process used to increase the strength of powder or compact materials below their melting point by bonding particles together. It describes the objectives and stages of sintering as well as different types, including solid-state, liquid-phase, conventional, and advanced processes like microwave, spark plasma, and high frequency induction heat sintering. Microwave sintering is highlighted as a superior advanced ceramic processing method compared to conventional techniques due to benefits like reduced energy consumption, heating rates, sintering temperatures, and improved material properties.
Refractories are materials that withstand high temperatures and exhibit properties such as resistance to heat, corrosion, and abrasion. The document discusses various refractory properties including physical properties like density, porosity, and cold crushing strength as well as thermal properties like refractoriness, thermal expansion, and thermal conductivity. It provides examples of common refractory materials used in cement production like magnesia bricks, high alumina bricks, and dolomite bricks. Key refractory testing methods are also summarized such as determining refractoriness under load and measuring thermal expansion under load (creep).
Creep is the time-dependent deformation of a material under constant stress at high temperatures. It occurs due to the movement of vacancies and dislocations within a material's microstructure. The critical temperature for creep to occur is 40% of the material's melting temperature. Different creep mechanisms dominate depending on the material, stress levels, and temperatures. Creep testing involves applying a constant load to a sample and measuring the strain over time until failure. The three stages of creep are primary, secondary, and tertiary creep. Creep can lead to failure of components in applications like turbines and nuclear reactors where high stresses and temperatures are present.
Plastic deformation and strengthning mechanismRahul Sen
Plastic deformation occurs through crystal distortion localized to slip planes and directions, most commonly through translational glide of dislocations. The presence of defects like dislocations explains why real crystals deform plastically at stresses much lower than theoretical predictions. Dislocations can glide, climb, and multiply, allowing plastic flow. Strengthening mechanisms like solution strengthening, precipitation strengthening, and work hardening increase the resistance of dislocation motion through interactions with solute atoms, particles, and other dislocations. In polycrystalline materials, grain boundaries further strengthen materials by impeding dislocation motion.
The document discusses the powder metallurgy process which consists of three main steps: 1) blending and mixing of metal powders and additives, 2) compaction of the blended powder using pressure-based or pressureless techniques, and 3) sintering the compacted powder below the melting point to bond the particles together without melting. Optional secondary operations such as heat treatment, machining or infiltration can further process the sintered parts.
1. The document discusses fatigue life estimation and fatigue crack initiation. It covers how fatigue occurs through repeated loading and unloading causing microscopic cracks.
2. Fatigue life is estimated using S-N curves which plot stress versus cycles to failure. The main steps in fatigue life estimation using S-N curves are also outlined.
3. Fatigue crack initiation involves two stages - micro cracks forming and growing (Stage I) and mechanically small cracks propagating (Stage II). The mechanism and factors influencing fatigue crack initiation are described.
This presentation is for mechanical engineering/ civil engineering students to help them understand the different type of destructive mechanical testing of materials. The tensile testing, hardness, impact test procedures are explained in detail.
Sintering is an important process for manufacturing ceramic products that involves consolidating powder materials into a dense mass without melting. It occurs through mass transport mechanisms like evaporation-condensation, vacancy diffusion, or viscous flow as particles bond together below melting temperatures. Liquid phase sintering uses a liquid that dissolves and reprecipitates solid particles to drive densification through capillary forces. Sintering progresses through initial, intermediate, and final stages characterized by changing pore shapes and densities.
There are several processes for shaping polymer matrix composites (PMCs), which can be categorized as open mold processes, closed mold processes, and continuous processes. Open mold processes involve manually laying up layers of fibers and resin in a mold. Closed mold processes use molds to shape the composite under heat and pressure. Continuous processes like filament winding and pultrusion produce long composite profiles. Common matrix materials are thermosetting polymers and common reinforcements are glass, carbon, and Kevlar fibers. PMC processes aim to efficiently orient and consolidate the fibers during curing.
The document discusses time-temperature-transformation (TTT) diagrams and the phase transformations they describe. TTT diagrams show the percentage of a phase transformation completed over temperature and time for a given alloy composition. They can indicate the microstructural phases like pearlite, bainite, and martensite that form during heating and cooling processes. The document explains how TTT diagrams are constructed from isothermal experiments and describes the various diffusion-controlled and diffusionless transformations that occur for a eutectoid steel depending on the cooling rate.
The document discusses various plastic manufacturing processes including compression molding, transfer molding, injection molding, extrusion molding, blow molding, calendaring, thermoforming, and polymer foaming. It provides details on each process such as how it works, advantages, disadvantages, and applications. Key plastic types are also discussed including thermoplastics, thermosets, and different polymer foams.
The document discusses various methods for casting and solidifying materials, including single crystal casting techniques. Single crystal casting of turbine blades involves directional solidification where a single crystal grows longitudinally through a ceramic mold for increased strength. For microelectronics, the Czochralski method pulls a seed crystal from molten material to form long single crystal ingots. Rapid solidification involves cooling molten material at over 106 K/s to form non-crystalline metallic glasses without grain growth. Roll casting is a common rapid solidification technique where molten material is spun against a chilled roll to rapidly solidify into amorphous ribbons or sheets.
The document discusses grain growth in ceramics. It covers:
1. Normal grain growth (NGG) follows a parabolic rate law where average grain size increases uniformly over time. Abnormal grain growth (AGG) results in a bimodal grain size distribution.
2. The Burke-Turnbull model describes NGG, where grain boundary mobility depends on the drag force and intrinsic mobility. However, many ceramics show a cubic rate law due to solute drag.
3. Solute drag occurs when impurities segregate to grain boundaries, reducing their mobility. Effective mobility decreases with increasing solute concentration and segregation. Dopant selection aims to maximize solute drag through low diffus
Review- Biomass Densification Technologies for Energy ApplicationBiorefineryEPC™
Review- Biomass Densification Technologies for Energy Application
Disclaimer-
YOU AGREE TO INDEMNIFY BiorefineryEPCTM , AND ITS AFFILIATES, OFFICERS, AGENTS, AND EMPLOYEES AGAINST ANY CLAIM OR DEMAND, INCLUDING REASONABLE ATTORNEYS' FEES, RELATED TO YOUR USE, RELIANCE, OR ADOPTION OF THE DATA FOR ANY PURPOSE WHATSOEVER. THE DATA ARE PROVIDED BY BiorefineryEPCTM "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY DISCLAIMED. IN NO EVENT SHALL BiorefineryEPCTM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER, INCLUDING BUT NOT LIMITED TO CLAIMS ASSOCIATED WITH THE LOSS OF DATA OR PROFITS, WHICH MAY RESULT FROM ANY ACTION IN CONTRACT, NEGLIGENCE OR OTHER TORTIOUS CLAIM THAT ARISES OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THE DATA.
This document discusses various polymer processing techniques. It begins by outlining three general phases of plastics processes: heating, shaping/forming under constraint, and cooling. It then describes specific processes like thermoforming, compression and transfer molding, rotational molding, extrusion and extrusion-based processes, injection molding, and blow molding. For each process, it provides details on how it works, its advantages and disadvantages, and common applications.
Griffith proposed that brittle materials contain small cracks and flaws that concentrate stress enough to reach the theoretical strength at nominal stresses below theoretical values. For a crack to propagate, the decrease in elastic strain energy from crack growth must be equal to or greater than the increase in surface energy. Griffith established a criterion where the stress required for crack propagation is inversely proportional to the square root of the crack length. This theory provides an equation to calculate the maximum crack length possible without fracture given a material's surface energy, modulus of elasticity, and applied stress.
Recrystallization is the process in which deformed grains of the crystal structure are replaced by a new set of stress-free grains that nucleate and grow until all the original grains have been consumed. The process is accomplished by heating the material to temperatures above that of crystallization.
The document discusses rate controlled sintering in advanced ceramic processes. It explains that sintering transforms ceramic powder compacts into dense materials through heating by reducing pores and growing grains. The driving force is lowering free energy. Sintering occurs in three stages and is affected by various factors. Rate controlled sintering controls the heating rate or temperature to control the sintering process for improved material properties. It provides examples demonstrating the effects of heating rate on microstructure.
The document discusses sintering, which is a thermal process used to increase the strength of powder or compact materials below their melting point by bonding particles together. It describes the objectives and stages of sintering as well as different types, including solid-state, liquid-phase, conventional, and advanced processes like microwave, spark plasma, and high frequency induction heat sintering. Microwave sintering is highlighted as a superior advanced ceramic processing method compared to conventional techniques due to benefits like reduced energy consumption, heating rates, sintering temperatures, and improved material properties.
Refractories are materials that withstand high temperatures and exhibit properties such as resistance to heat, corrosion, and abrasion. The document discusses various refractory properties including physical properties like density, porosity, and cold crushing strength as well as thermal properties like refractoriness, thermal expansion, and thermal conductivity. It provides examples of common refractory materials used in cement production like magnesia bricks, high alumina bricks, and dolomite bricks. Key refractory testing methods are also summarized such as determining refractoriness under load and measuring thermal expansion under load (creep).
Creep is the time-dependent deformation of a material under constant stress at high temperatures. It occurs due to the movement of vacancies and dislocations within a material's microstructure. The critical temperature for creep to occur is 40% of the material's melting temperature. Different creep mechanisms dominate depending on the material, stress levels, and temperatures. Creep testing involves applying a constant load to a sample and measuring the strain over time until failure. The three stages of creep are primary, secondary, and tertiary creep. Creep can lead to failure of components in applications like turbines and nuclear reactors where high stresses and temperatures are present.
Plastic deformation and strengthning mechanismRahul Sen
Plastic deformation occurs through crystal distortion localized to slip planes and directions, most commonly through translational glide of dislocations. The presence of defects like dislocations explains why real crystals deform plastically at stresses much lower than theoretical predictions. Dislocations can glide, climb, and multiply, allowing plastic flow. Strengthening mechanisms like solution strengthening, precipitation strengthening, and work hardening increase the resistance of dislocation motion through interactions with solute atoms, particles, and other dislocations. In polycrystalline materials, grain boundaries further strengthen materials by impeding dislocation motion.
The document discusses the powder metallurgy process which consists of three main steps: 1) blending and mixing of metal powders and additives, 2) compaction of the blended powder using pressure-based or pressureless techniques, and 3) sintering the compacted powder below the melting point to bond the particles together without melting. Optional secondary operations such as heat treatment, machining or infiltration can further process the sintered parts.
1. The document discusses fatigue life estimation and fatigue crack initiation. It covers how fatigue occurs through repeated loading and unloading causing microscopic cracks.
2. Fatigue life is estimated using S-N curves which plot stress versus cycles to failure. The main steps in fatigue life estimation using S-N curves are also outlined.
3. Fatigue crack initiation involves two stages - micro cracks forming and growing (Stage I) and mechanically small cracks propagating (Stage II). The mechanism and factors influencing fatigue crack initiation are described.
This presentation is for mechanical engineering/ civil engineering students to help them understand the different type of destructive mechanical testing of materials. The tensile testing, hardness, impact test procedures are explained in detail.
Sintering is an important process for manufacturing ceramic products that involves consolidating powder materials into a dense mass without melting. It occurs through mass transport mechanisms like evaporation-condensation, vacancy diffusion, or viscous flow as particles bond together below melting temperatures. Liquid phase sintering uses a liquid that dissolves and reprecipitates solid particles to drive densification through capillary forces. Sintering progresses through initial, intermediate, and final stages characterized by changing pore shapes and densities.
There are several processes for shaping polymer matrix composites (PMCs), which can be categorized as open mold processes, closed mold processes, and continuous processes. Open mold processes involve manually laying up layers of fibers and resin in a mold. Closed mold processes use molds to shape the composite under heat and pressure. Continuous processes like filament winding and pultrusion produce long composite profiles. Common matrix materials are thermosetting polymers and common reinforcements are glass, carbon, and Kevlar fibers. PMC processes aim to efficiently orient and consolidate the fibers during curing.
The document discusses time-temperature-transformation (TTT) diagrams and the phase transformations they describe. TTT diagrams show the percentage of a phase transformation completed over temperature and time for a given alloy composition. They can indicate the microstructural phases like pearlite, bainite, and martensite that form during heating and cooling processes. The document explains how TTT diagrams are constructed from isothermal experiments and describes the various diffusion-controlled and diffusionless transformations that occur for a eutectoid steel depending on the cooling rate.
The document discusses various plastic manufacturing processes including compression molding, transfer molding, injection molding, extrusion molding, blow molding, calendaring, thermoforming, and polymer foaming. It provides details on each process such as how it works, advantages, disadvantages, and applications. Key plastic types are also discussed including thermoplastics, thermosets, and different polymer foams.
The document discusses various methods for casting and solidifying materials, including single crystal casting techniques. Single crystal casting of turbine blades involves directional solidification where a single crystal grows longitudinally through a ceramic mold for increased strength. For microelectronics, the Czochralski method pulls a seed crystal from molten material to form long single crystal ingots. Rapid solidification involves cooling molten material at over 106 K/s to form non-crystalline metallic glasses without grain growth. Roll casting is a common rapid solidification technique where molten material is spun against a chilled roll to rapidly solidify into amorphous ribbons or sheets.
The document discusses grain growth in ceramics. It covers:
1. Normal grain growth (NGG) follows a parabolic rate law where average grain size increases uniformly over time. Abnormal grain growth (AGG) results in a bimodal grain size distribution.
2. The Burke-Turnbull model describes NGG, where grain boundary mobility depends on the drag force and intrinsic mobility. However, many ceramics show a cubic rate law due to solute drag.
3. Solute drag occurs when impurities segregate to grain boundaries, reducing their mobility. Effective mobility decreases with increasing solute concentration and segregation. Dopant selection aims to maximize solute drag through low diffus
Review- Biomass Densification Technologies for Energy ApplicationBiorefineryEPC™
Review- Biomass Densification Technologies for Energy Application
Disclaimer-
YOU AGREE TO INDEMNIFY BiorefineryEPCTM , AND ITS AFFILIATES, OFFICERS, AGENTS, AND EMPLOYEES AGAINST ANY CLAIM OR DEMAND, INCLUDING REASONABLE ATTORNEYS' FEES, RELATED TO YOUR USE, RELIANCE, OR ADOPTION OF THE DATA FOR ANY PURPOSE WHATSOEVER. THE DATA ARE PROVIDED BY BiorefineryEPCTM "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY DISCLAIMED. IN NO EVENT SHALL BiorefineryEPCTM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER, INCLUDING BUT NOT LIMITED TO CLAIMS ASSOCIATED WITH THE LOSS OF DATA OR PROFITS, WHICH MAY RESULT FROM ANY ACTION IN CONTRACT, NEGLIGENCE OR OTHER TORTIOUS CLAIM THAT ARISES OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THE DATA.
This document discusses generating a foam-like infill structure for 3D printing applications using a biomimetic approach. It reviews bone structure, engineering foams, 3D printing technology, 3D models, and the Protosphere sphere packing algorithm. The methodology generates a foam structure by using Protosphere to place non-overlapping spheres within a 3D model, converting it to an STL file for 3D printing. This structure mimics bone and is intended to produce stronger, lighter parts compared to traditional layer-based infill patterns.
SINTERFLEX - Carbon Control in PM SinteringAkin Malas
The presentation shows the Linde Gas SINTERFLEX technology for the PM Sintering industry and sharing background information on application in the industry for improving the quality of the PM parts in the sintering parts using the SINTERFLEX technology.
This document discusses barium zirconate, including its perovskite structure and applications as an electrolyte and electrode material in intermediate temperature solid oxide fuel cells. It is doped with Y2O3 to create oxygen vacancies. The document covers the advantages of high stability and reduced fabrication problems between 600-800°C, as well as the disadvantage of difficult sintering. It describes the sample preparation process and characterization techniques to analyze phase formation, density, microstructure. Results show single phase formation but low density without ZnO additive, which enables 92-94% density.
This document discusses bearings and their functions. It describes how bearings support rotating shafts and reduce friction to allow for smooth rotation. There are two main types of bearings - plain/slider bearings which have a large contact area and high friction, and rolling/ball bearings which have less contact area and lower rolling friction. Ball and roller bearings are further described as having races, balls/rollers, and a cage that separates the balls to reduce friction. Common ball and roller bearing types and their applications are also outlined.
The given document does not contain any readable text or meaningful information. It consists entirely of unreadable characters. Therefore, no accurate summary can be provided.
This document discusses grain boundary strengthening as a technique for strengthening materials. It describes how grain boundaries separate grains of different crystallographic orientations and act as barriers to dislocation motion. High angle grain boundaries have higher surface energy than low angle grain boundaries. Strengthening can occur through restricting dislocation motion at grain boundaries, making the material harder but sometimes reducing ductility. Grain boundary sliding is another deformation mechanism above half the melting temperature, where sliding along boundaries can occur.
The document discusses powder metallurgy and provides information about various aluminium powders and products produced including spherical and non-spherical aluminium powders, alloyed aluminium powders, aluminium granules, pigmentary aluminium powders, pyrotechnic aluminium powders, aluminium powders and pastes for aerated concrete. It also provides details on product specifications, quality control, certifications and contact information for powder metallurgy enterprises.
This document provides an overview of selective laser sintering (SLS) technology. It discusses the history and development of SLS, the SLS process, materials that can be used, applications, advantages and limitations. Recent developments discussed include using SLS to create electrical devices, 3D print in color, and develop drug delivery devices. Potential future applications highlighted are in the medical, aerospace, automotive and manufacturing industries, with a focus on increased speed, accuracy, size capacity and new materials like metals.
The document discusses powder metallurgy bearing materials. It begins with a brief history of self-lubricating bearings developed in the 1920s. Common materials used include bronze, iron, and aluminum alloys which are porous and can be impregnated with oil to provide self-lubrication. The document outlines the manufacturing process and secondary operations like impregnation, machining, and coating. Self-lubricating bearings have advantages of reliability, low maintenance needs, and can operate under a range of loads and speeds. Selection of the proper bearing material is important for predictable wear performance and lifetime in different applications.
This power point presentation gives the introduction about DMLS process (Direct Metal Laser sintering) and Direct Metal 20 (DM20) material. It also illustrates DMLS process and applications of DMLS.
Precipitation hardening, also known as age-hardening, involves quenching an alloy to increase its hardness over time through nucleation and growth of precipitates. It involves three main steps: solution treatment to dissolve precipitates, quenching, then aging at a lower temperature which allows precipitation to occur. During aging, carbon diffuses from ferrite forming cementite precipitates within the ferrite matrix, increasing the alloy's hardness. The rate of precipitation depends on temperature and free energy, with moderate temperatures and energies allowing the most rapid hardening. Over-aging can cause hardness to decrease if aging is done for too long.
The document summarizes key concepts from Chapter 7 of the textbook "Introduction to Materials Science" related to strengthening mechanisms in materials. It discusses how plastic deformation occurs through the motion of dislocations in materials and different ways to strengthen materials by impeding dislocation motion, such as reducing grain size, alloying, and increasing dislocation density through strain hardening. It also covers recovery, recrystallization and grain growth processes in materials after plastic deformation.
Powder metallurgy is a metal processing technique where parts are produced from metallic powders. There are several key steps: (1) metallic powders are produced through processes like atomization or chemical/electrolytic methods, (2) the powders are pressed into a die to form a green compact, and (3) the compact is sintered by heating below the melting point to bond the powder particles. Powder metallurgy allows for net-shape production with little material waste and precise control over composition and properties. Common powder metallurgy products include gears, bearings, cutting tools, and other parts.
The document discusses dislocations and strengthening mechanisms in metals, including how plastic deformation occurs through the motion of dislocations, and mechanisms like reducing grain size, solid solution strengthening, and strain hardening that impede dislocation motion and strengthen metals. Grain boundaries, solute atoms, and increased dislocation density from deformation respectively act as barriers to dislocation movement to strengthen materials.
This document discusses different types of magnetic separators used in mineral processing. It describes four main types: magnetic drum separators, ball Norton separators, roller type magnetic separators, and gravity feed magnetic separators. Magnetic drum separators use rotating drums with magnets to separate ferrous materials. Ball Norton separators handle large amounts of ferrous material. Roller type separators use magnetic rolls and conveyors to separate materials. Gravity feed separators use gravity and magnets in a vertical flow system to separate ferrous tramp metals. The document provides details on how each type of separator works and common applications in industries like mining, food processing, chemicals and more.
“Applications Of Powder Metallurgy In Reference with Cutting tools”Dushyant Kalchuri
Powder metallurgy is used for manufacturing products or articles from powdered metals by placing these powders in molds and are compacting the same using heavy compressive force. Typical examples of such article or products are grinding wheels, filament wire, magnets, welding rods, tungsten carbide cutting tools, self-lubricating bearings electrical contacts and turbines blades having high temperature strength. The manufacture of parts by powder metallurgy process involves the manufacture of powders, blending, compacting, profiteering, sintering and a number of secondary operations such as sizing, coining, machining, impregnation, infiltration, plating, and heat treatment.
The document analyzes the motion of workpieces in a centrifugal barrel finishing process. It describes:
1) The absolute acceleration of workpieces placed in a rotating tub by considering them as particles referenced to a moving coordinate system.
2) How the relationship between the speed of the turret and tub maintains proper relative motion between abrasives and workpieces.
3) How variables like abrasive size and type, forces, mixture volume, and time affect outcomes like material removal rate, surface finish, and hardness.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
We would send hard copy of Journal by speed post to the address of correspondence author after online publication of paper.
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Research Inventy : International Journal of Engineering and Scienceresearchinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
This document provides an overview of torsion in thin-walled beams. It discusses how torsion arises from loads like engine thrust and control surfaces. Methods are presented for calculating shear stresses and angle of twist in closed and open beam sections under torque loading. An example calculates shear stress distribution in a 3-cell wing section. Understanding shear flow direction is important for sign convention in open sections.
Kinetic pathways to the isotropic-nematic phase transformation: a mean field ...Amit Bhattacharjee
Here we illustrate the classic Ginzburg-Landau-de Gennes theory of isotropic nematic phase transition and show how fluctuations as well as deterministic kinetics can lead to phase equilibria.
The document discusses numerical simulations of ablation patterns on sublimating materials. It summarizes previous research on crosshatch patterns and experiments by Stock. The approach involves using CFD tools to implement a non-trivial boundary condition for low-temperature ablator camphor. Validation simulations of Baker's experiments on camphor cones show good agreement. Preliminary 3D simulations with turbulent models show localized groove patterns developing from peaks in wall temperature. Future work includes more detailed 3D cases and investigating the wall temperature dependence of groove formation.
The document describes a lifetime calculator tool developed at ALBA to calculate the beam lifetime based on machine parameters like beam current, coupling, RF voltage, and pressure. It summarizes the calculation methods for Touschek lifetime due to electron-electron scattering and gas lifetime due to collisions with residual gas. The tool integrates these calculations into ALBA's control system to continuously compare calculated and measured lifetimes as a diagnostic. It allows simulating the lifetime for different machine conditions to predict changes.
This document provides an overview of torsion in thin-walled beams. It discusses how torsional loads are generated in wing structures from factors like engine placement. Methods are presented for calculating shear stress and twist angle due to torsion in closed and open section beams, as well as multicellular wing sections. Examples are worked through to demonstrate calculating shear flow distribution, shear stress, and twist angle for beams with various cross-sectional geometries under applied torques.
Natural Convection Heat Transfer of Viscoelastic Fluids in a Horizontal AnnulusPMOHANSAHU
a detailed discussion of the results in terms of the streamline profiles, isotherm contours, distribution of local Nusselt number, variation of velocity components, etc., is also presented. Finally, from an application standpoint, a simple correlation for the average Nusselt number is presented, which can be used for the interpolation of the present results for the intermediate values of the governing parameters in a new application.
Design & Computational Fluid Dynamics Analyses of an Axisymmetric Nozzle at T...IRJET Journal
This document summarizes a numerical investigation of flow through an axisymmetric boat tail nozzle at transonic conditions using computational fluid dynamics (CFD). The study analyzed the effects of friction on adiabatic flow and determined a friction factor of 0.001452. CFD simulations using GAMBIT and FLUENT were conducted with a k-epsilon turbulence model to analyze pressure distributions, velocity vectors, and coefficient of pressure plots. Validation against experimental data showed reasonable agreement. The study concluded that CFD can predict nozzle aerodynamics, though turbulence models under predict pressures. Friction was found to impact real flows compared to isentropic assumptions. Future work could analyze shockwaves at Mach 0.8.
This document summarizes a numerical study of airflow over an Ahmed body using RANS turbulence models. It finds that the k-ε-v2 model more accurately predicts separation and reattachment compared to other models. The study simulates flow over an Ahmed body with a 35 degree rear angle using various turbulence models and investigates the effects of grid layout and differencing schemes on the results. Numerical results agree well with experimental data on the wake structure and turbulent kinetic energy distribution behind the body.
techDynamic characteristics and stability of cylindrical textured journal bea...ijmech
This document summarizes a study on the dynamic characteristics and stability of cylindrical textured journal bearings. The researchers numerically solved the Reynolds equation to analyze the effect of texture depth and density on the stiffness, damping coefficients, stability parameter, and whirl ratio of the bearing. They found that stability is enhanced with increasing texture depth, while there is an optimum texture density that results in maximum stability. Direct and cross stiffness/damping coefficients, stability margin, and whirl ratio were presented for different texture parameters.
This document discusses a numerical study of the effect of thermal radiation on free convection boundary layer flow over a vertical wavy cone. The governing equations for steady, laminar, two-dimensional flow are presented and non-dimensionalized. These equations are then solved using the Mathematica technique. Graphs of the dimensionless temperature, velocity, skin friction coefficient, and Nusselt number are generated for various values of the Prandtl number, radiation parameter, surface wave amplitude, and cone half-angle. The results are discussed to analyze the impact of thermal radiation on the flow and heat transfer characteristics.
This document describes an exit exam module for a fluid mechanics course. It is divided into two parts that cover key topics like fluid properties, statics, dynamics, and dimensional analysis. It also outlines the course goals, which are to understand fluids at rest and in motion, apply fluid principles to engineering problems, and analyze compressible and potential flows. The teaching methods include tutorials, textbook problems, and independently practicing examples and review questions to prepare for the exit exam.
This document contains multiple choice questions related to various topics in physics including electromagnetism, mechanics, heat and thermodynamics, modern physics, and other areas. The questions are from different dates and shifts and cover concepts such as EM waves, crystal structures, projectile motion, capacitors, magnetic fields, radioactivity, and more. Multiple choice options A, B, C, or D are provided for each question.
1. Laser pulses were used to generate shock waves in solids with peak pressures ranging from 5 to 120 kilobars. Peak pressures of around 35 kilobars were achieved at a fluence of 1000 J/cm2, while applying a transparent overlay increased the peak pressure to 120 kilobars.
2. Measurements found that plasma initiation occurred around 8 nanoseconds into a laser pulse when exposing a graphite coating. The resulting shock wave rose sharply at 37 nanoseconds, with only a small precursor pressure seen earlier.
3. Precursor pressures seen with carbon-resin coatings but not with pure graphite coatings, supporting the idea that precursors are due to surface ablation pressures before plasma formation
LES Analysis on Confined Swirling Flow in a Gas Turbine Swirl BurnerROSHAN SAH
This presentation describes a Large Eddy Simulation (LES) investigation into flow fields in a model gas turbine combustor equipped with a swirl burner. A probability density function was used to describe the interaction physics of chemical reaction and turbulent flow as liquid fuel was directly injected into the combustion chamber and rapidly mixed with the swirling air. Simulation results showed that heat release during combustion accelerated the axial velocity motion and made the recirculation zone more compact
Natural Convection and Entropy Generation in Γ-Shaped Enclosure Using Lattice...A Behzadmehr
This work presents a numerical analysis of entropy generation in Γ-Shaped enclosure that was submitted to the natural convection process using a simple thermal lattice Boltzmann method (TLBM) with the Boussinesq approximation. A 2D thermal lattice Boltzmann method with 9 velocities, D2Q9, is used to solve the thermal flow problem. The simulations are performed at a constant Prandtl number (Pr = 0.71) and Rayleigh numbers ranging from 103 to 106 at the macroscopic scale (Kn = 10-4). In every case, an appropriate value of the characteristic velocity is chosen using a simple model based on the kinetic theory. By considering the obtained dimensionless velocity and temperature values, the distributions of entropy generation due to heat transfer and fluid friction are determined. It is found that for an enclosure with high value of Rayleigh number (i.e., Ra=105), the total entropy generation due to fluid friction and total Nu number increases with decreasing the aspect ratio.
X-ray diffraction is a technique used to characterize materials by analyzing the diffraction patterns of X-rays scattered from a sample. The document outlines the basic principles of X-ray diffraction, including Bragg's law, reciprocal lattices, and how diffraction patterns can provide information about crystal structure, phase, texture, and other structural properties. Examples are given of analyzing diffraction data from both powder and single crystal samples.
A high-Speed Communication System is based on the Design of a Bi-NoC Router, ...DharmaBanothu
The Network on Chip (NoC) has emerged as an effective
solution for intercommunication infrastructure within System on
Chip (SoC) designs, overcoming the limitations of traditional
methods that face significant bottlenecks. However, the complexity
of NoC design presents numerous challenges related to
performance metrics such as scalability, latency, power
consumption, and signal integrity. This project addresses the
issues within the router's memory unit and proposes an enhanced
memory structure. To achieve efficient data transfer, FIFO buffers
are implemented in distributed RAM and virtual channels for
FPGA-based NoC. The project introduces advanced FIFO-based
memory units within the NoC router, assessing their performance
in a Bi-directional NoC (Bi-NoC) configuration. The primary
objective is to reduce the router's workload while enhancing the
FIFO internal structure. To further improve data transfer speed,
a Bi-NoC with a self-configurable intercommunication channel is
suggested. Simulation and synthesis results demonstrate
guaranteed throughput, predictable latency, and equitable
network access, showing significant improvement over previous
designs
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELijaia
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
Blood finder application project report (1).pdfKamal Acharya
Blood Finder is an emergency time app where a user can search for the blood banks as
well as the registered blood donors around Mumbai. This application also provide an
opportunity for the user of this application to become a registered donor for this user have
to enroll for the donor request from the application itself. If the admin wish to make user
a registered donor, with some of the formalities with the organization it can be done.
Specialization of this application is that the user will not have to register on sign-in for
searching the blood banks and blood donors it can be just done by installing the
application to the mobile.
The purpose of making this application is to save the user’s time for searching blood of
needed blood group during the time of the emergency.
This is an android application developed in Java and XML with the connectivity of
SQLite database. This application will provide most of basic functionality required for an
emergency time application. All the details of Blood banks and Blood donors are stored
in the database i.e. SQLite.
This application allowed the user to get all the information regarding blood banks and
blood donors such as Name, Number, Address, Blood Group, rather than searching it on
the different websites and wasting the precious time. This application is effective and
user friendly.
Generative AI Use cases applications solutions and implementation.pdfmahaffeycheryld
Generative AI solutions encompass a range of capabilities from content creation to complex problem-solving across industries. Implementing generative AI involves identifying specific business needs, developing tailored AI models using techniques like GANs and VAEs, and integrating these models into existing workflows. Data quality and continuous model refinement are crucial for effective implementation. Businesses must also consider ethical implications and ensure transparency in AI decision-making. Generative AI's implementation aims to enhance efficiency, creativity, and innovation by leveraging autonomous generation and sophisticated learning algorithms to meet diverse business challenges.
https://www.leewayhertz.com/generative-ai-use-cases-and-applications/
This study Examines the Effectiveness of Talent Procurement through the Imple...DharmaBanothu
In the world with high technology and fast
forward mindset recruiters are walking/showing interest
towards E-Recruitment. Present most of the HRs of
many companies are choosing E-Recruitment as the best
choice for recruitment. E-Recruitment is being done
through many online platforms like Linkedin, Naukri,
Instagram , Facebook etc. Now with high technology E-
Recruitment has gone through next level by using
Artificial Intelligence too.
Key Words : Talent Management, Talent Acquisition , E-
Recruitment , Artificial Intelligence Introduction
Effectiveness of Talent Acquisition through E-
Recruitment in this topic we will discuss about 4important
and interlinked topics which are
Impartiality as per ISO /IEC 17025:2017 StandardMuhammadJazib15
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Open Channel Flow: fluid flow with a free surfaceIndrajeet sahu
Open Channel Flow: This topic focuses on fluid flow with a free surface, such as in rivers, canals, and drainage ditches. Key concepts include the classification of flow types (steady vs. unsteady, uniform vs. non-uniform), hydraulic radius, flow resistance, Manning's equation, critical flow conditions, and energy and momentum principles. It also covers flow measurement techniques, gradually varied flow analysis, and the design of open channels. Understanding these principles is vital for effective water resource management and engineering applications.
1. Solid State Sintering
Shantanu K Behera
Dept of Ceramic Engineering
NIT Rourkela
CR 320 CR 654
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 1 / 47
2. Chapter Outline
1 Sintering Mechanisms
2 Scaling Law
3 Stages of Sintering
4 Initial Stage
5 Intermediate Stage Sintering
6 Final Stage Sintering: Geometrical Model
7 Sintering with Externally Applied Pressure
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 2 / 47
3. Sintering Mechanisms
3 Particle Model
Figure : Fig 2.1, Sintering of Ceramics, Rahaman, pg. 46
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 3 / 47
4. Sintering Mechanisms
Sintering Mechanisms and Routes
Mechanisms Source Sink Densifying
Surface Diffusion Surface Neck No
Lattice Diffusion Surface Neck No
GB Diffusion GB Neck Yes
Lattice Diffusion GB Neck Yes
Vapor Transport Surface Neck No
Plastic Flow Dislocations Neck Yes
Note that mechanisms that extend the GB region (solid-solid interface) are
densifying mechanisms. That keep the solid-vapor interface are
non-densifying mechanisms.
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 4 / 47
5. Sintering Mechanisms
3 Particle Model
Calculate the free energy (surface related) difference between a set of
particles, and the same set of particles when sintered.
Note that the net reduction in energy would be equal to the total grain
boundary energy less the total surface (solid-vapor) energy.
Ed = As(
γgb
2
− γsv)
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 5 / 47
6. Sintering Mechanisms
Curvature
Figure : Curvature in solids, and their effect of vacancy concentration
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 6 / 47
7. Sintering Mechanisms
Vacancy under a Curved Surface
Chemical potential of atoms in a crystal can be written as
µa = µoa + pΩa + kBT ln Ca
Similarly, chemical potential of vacancies in a crystal can be written as
µv = µov + pΩv + kBT ln Cv
Chemical potential of vacancies under a curved surface can be written as
µv = µov + (p + γsvκ)Ω + kBT ln Cv
where κ = 1
R1
+ 1
R2
Accordingly, the equilibrium vacancy concentration
beneath a curved surface
Cv = Co,ve
−γsvκΩ
kBT
For γsvκΩ << kBT, this reduces to
Cv
Co,v
= 1 −
γsvκΩ
kBT
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 7 / 47
8. Sintering Mechanisms
Vapor Pressure over a Curved Surface
Figure : Curvature in solids, and their effect on vapor pressure
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 8 / 47
9. Sintering Mechanisms
Vapor Pressure over a Curved Surface
Vapor pressure over a curved surface can be defined as
Pvap = P0e
γsvκΩ
kBT
This simplifies to:
Pvap = P0 1 +
γsvκΩ
kBT
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 9 / 47
10. Sintering Mechanisms
Diffusional Flux Equations
The general expression for flux:
J =
−DiC
kBT
dµ
dx
Flux of atoms:
Ja =
−DaCa
ΩkBT
d(µa − µv)
dx
Flux of vacancies and atoms are opposite to each other:
Ja = −Jv
Flux of vacancies:
Jv =
−DvCv
ΩkBT
dµv
dx
=
−Dv
Ω
dCv
dx
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 10 / 47
11. Scaling Law
Herring’s Scaling Law
Length scale is an important parameter in sintering.
How does the change of scale (e.g. particle size) influence the rate of
sintering?
The law is based on simple models and assumptions.
Particle size remains the same.
Similar geometrical changes in different powder systems.
Similar composition.
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 11 / 47
12. Scaling Law
Herring’s Scaling Law
Define λ as the numerical factor
Say, λ = a2
a1
, where a is the radius of the particle
Similarly, λ = X2
X1
, where X is the neck dimension of the two particle system.
Time required to produce a certain change by diffusional flux can be written as
t =
V
JA
Comparing two systems, we can write
t2
t1
=
V2J1A1
V1J2A2
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 12 / 47
13. Scaling Law
Scaling Law for Lattice Diffusion
While comparing two spherical particles of sizes, a1 and a2, we can say that
the volume of matter transported is V1 ∝ a3
1, and V2 ∝ a3
2. And since λ = a2
a1
,
we can write V2 = λ3
Va.
Similarly A2 = λ2
A1
Again, flux (J) is ∝ the gradient in chemical potential (i.e. µ)
µ varies as 1
r , Therefore, J ∝ 1
r , Or J ∝ 1
r2
Therefore, J2 = J1
λ2
Summary: the parameters for lattice diffusion are:
V2 = λ3
V1; A2 = λ2
A1; J2 = J1
λ2
Comparing two systems, we can write
t2
t1
= λ3
=
a2
a1
3
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 13 / 47
14. Scaling Law
Scaling Law for Other Mechanisms
In a general form, we can write as:
t2
t1
= λn
=
a2
a1
3
where m is the exponent that depends on the mechanism of sintering. Some
of the exponents for different mechanisms are as follows.
Sintering Mechanisms Exponent
Surface Diffusion 4
Lattice Diffusion 3
GB Diffusion 4
Vapor Transport 2
Plastic Flow 1
Viscous Flow 1
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 14 / 47
15. Scaling Law
Relative Rates of Mechanisms
For a given microstructural change tha rate is inversely proportional to the
time required for the change. Therefore,
Rate2
Rate1
= λ−n
If grain boundary diffusion is the
dominant mechanism; then
Rategb = λ−4
If evaporation-condensation is the
dominant mechanism; then
Rateec = λ−2
Figure : Relative rates of sintering for GB
and EC as a function of length scale
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 15 / 47
16. Stages of Sintering
Generalized Sintering Curve
Figure : Schematic of a sintering curve of a powder compact during three sintering
stages.
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 16 / 47
17. Stages of Sintering
Sintering Stages
Sintering
Stage
Microstructural Fea-
tures
Relative
Density
Idealized Model
Initial Interparticle neck
growth
Up to
0.65
Spheres in contact
Intermediate Equilibrium pore
shape with continu-
ous porosity
0.65 -
0.9
Tetrakaidecahedron
with cylindrical
pores of the same
radius along edges
Final Equilibrium pore
shape with isolated
porosity
≥0.9 Tetrakaidecahedron
with spherical pores
at grain corners
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 17 / 47
18. Stages of Sintering
Sintering Stage Microstructures (Real)
Initial stage (a)
rapid interparticle growth (various
mechanisms), neck formation,
linear shrinkage of 3-5%.
Intermediate stage (b)
Continuous pores, porosity is
along grain edges, pore cross
section reduces, finally pores
pinch off. Up to 0.9 of TD.
Final stage (c)
Isolated pores at grain corners,
pores gradually shrink and
disappear. From 0.9 to TD.
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 18 / 47
19. Stages of Sintering
Schematic of Intermediate and Final Stage Models
Figure : Idealized models of grains during (a) intermediate, and (b) final stage of
sintering. After R L Coble
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 19 / 47
20. Initial Stage
Geometrical Model for Initial Stage
Figure : Geometrical models for the initial
sintering stage; (a) non-densifying, and (b)
densifying mechanism.
Non-
densifying
Parameter Densifying
r = X2
2a Radius of
Neck
r = X2
4a
r = π2
X3
a Area of
Neck
Surface
A = π2
X3
2a
r = πX4
2a Volume
into Neck
r = πX4
8a
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 20 / 47
21. Initial Stage
Kinetic Equations
Flux of atoms into the neck
Ja =
Dv
Ω
dCv
dx
Volume of matter transported to neck per unit time
dV
dt
= JaAgbΩ
Note that Agb = 2πXδgb Therefore,
dV
dt
= Dv2πXδgb
dCv
dx
Assuming that the vacancy concentration between surface and neck remains
constant dCv
dx = Cv
X Therefore,
Cv = Cv − Cvo =
CvoγsvΩ
kBT
1
r1
+
1
r2
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 21 / 47
22. Initial Stage
Kinetic Equations Contd..
If we take r1 = r and r2 = −X, and assuming X >> r, we have
dV
dt
=
2πDvCvoδgbγsvΩ
kBTr
Using dV
dt from geometrical model, and Dgb = DvCvo,
πX3
2a
dX
dt
=
2πDgbδgbγsvΩa2
kBT
4a
X2
On simplification
X5
dX =
16DgbδgbγsvΩa2
kBT
dt
Upon integrating
X6
=
96DgbδgbγsvΩa2
kBT
t
We can write in another form:
X
a
=
96DgbδgbγsvΩa2
kBTa4
1
6
t
1
6
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 22 / 47
23. Initial Stage
Kinetic Equations Contd..
X
a
=
96DgbδgbγsvΩ
kBTa4
1
6
t
1
6
This expression tells you that the ratio of neck radius to the sphere radius
increases as t
1
6 . For densifying mechanisms the shrinkage can be measured
as the change in length over original length.
l
l0
= −
r
a
= −
X2
4a2
Therefore
l
l0
=
3DgbδgbγsvΩ
kBTa4
1
3
t
1
3
The shrinkage is therefore predcited to increase as t
1
3
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 23 / 47
24. Initial Stage
Kinetic Equations for Viscous Flow
Rate of energy dissipation by viscous flow should equal to rate of energy
gained by reduction in surface area.
The final expression looks like
X
a
=
3γsv
2ηa
1
2
t
1
2
How would the expression for shrinkage by viscous flow look like?
l
l0
=
3γsv
8ηa
t
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 24 / 47
25. Initial Stage
Generalized Expressions
There can be general expressions for neck growth and densification as
follows:
X
a
m
=
H
an
t
l
l0
m
2
= −
H
2man
t
m, and n are numerical exponents that depend on sintering mechanisms.
H contains geometrical and material parameters.
A range of values for m and n can be obtained.
Shantanu Behera (NIT Rourkela) SINTERING CR 320 CR 654 25 / 47
26. Initial Stage
Summary: Initial Sintering Stage
Mechanism m n H♥
Surface diffusion♦
7 4 56DsδsγsvΩ/kBT
Lattice diffusion from sur-
face♦
5 3 20DlγsvΩ/kBT
Vapor transport♦
3 2 3P0γsvΩ/(2πmkBT)1/2
kBT
GB diffusion 6 4 96DgbδgbγsvΩ/kBT
Lattice diffusion from GB 4 3 80πDlγsvΩ/kBT
Viscous flow 2 1 3γsv/2η
♦
- non-densifying mechanism
♥
- Diffusion coefficients and constants with usual meanings.
If you recall, the exponent n here is same as the Herring’s Scaling Law
exponent.
Also note that, for nondensifying mechanisms m is an odd number.
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27. Intermediate Stage Sintering
Intermediate Sintering Stage
If you recall, the intermediate stage is characterized by continuous pores,
porosity is along grain edges, pore cross section reduces, with finally pinching
off of pores.
Figure : Coble’s geometrical model for intermediate stage (a), and final stage (b).
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28. Intermediate Stage Sintering
Geometrical Model
Geometrically, sintering can be achieved as per the following two points:
Minimization of total interfacial
area (intfc tension eqlb.)
Filling of space without voids
In 2 dimensions, this can be
achieved by a hexagonal array
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29. Intermediate Stage Sintering
Geometrical Model Contd..
In 3D tension equilibrium
requirement: 6 planes (grain
boundaries) and 4 lines (grain
edges) meet.
So, the number of corners that are
needed for a grain to be in
equilibrium is 22.8.
Two possible structures:
pentagonaldodecahedron and
tetrakaidecahedron.
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33. Intermediate Stage Sintering
Geometrical Model for Sintering
Space-filling array of equal sized tetrakaidecahedron, each of it describing
one particle. Cylindrical channel pores at TKD edges. Volume of
tetrakaidecahedron
Vt = 8
√
2l3
p
where lp is the edge length of the TKD. Total porosity (with r as the radius of
the pore)
Vp =
1
3
36πr2
lp
Therefore, porosity of the unit cell:
Vt
Vp
= Pc =
3π
2
√
2
r2
l2
p
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34. Intermediate Stage Sintering
Sintering Equations
For Lattice Diffusion:
1
ρ
dρ
dt
=
10DlγsvΩ
ρG3kBT
Densification rate at a fixed density scales inversely with the cube of grain size
(Check Herring’s law).
For Grain Boundary Diffusion:
1
ρ
dρ
dt
=
4
3
DgbδgbγsvΩ
ρ(1 − ρ)1/2G4kBT
Densification rate at a fixed density scales inversely with the fourth power of
grain size.
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35. Final Stage Sintering: Geometrical Model
Final Sintering Stage
Cylindrical pore channels pinch off
Pores become isolated
Pores at 4 grain junctions
Average density can be defined as:
ρ = 1 −
r
b
3
Number of pores per unit volume
N =
3
4π
1 − ρ
ρr3
Figure : Pore radius and improvement of
density
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36. Final Stage Sintering: Geometrical Model
Final Stage Sintering Equations
Porosity at time t:
Ps =
6π
√
2
DlγsvΩ
l3kBT
(tf − t)
For diffusion of atoms occurring by lattice diffusion:
dρ
dt LD
=
288DlγsvΩ
G3kBT
For diffusion occurring by grain boundary diffusion:
dρ
dt GBD
=
735DgbδgbγsvΩ
G4kBT
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37. Final Stage Sintering: Geometrical Model
Phenomenological Sintering Equation
In this approach, empirical equations are developed to fit experimental data
(ρ ∼ t)
ρ = ρ0 + K ln
t
t0
where K is a temperature dependent parameter.
For Coble’s lattice diffusion model:
dρ
dt
=
ADlγsvΩ
G3kBT
where A is a constant that relates to the sintering stage.
If grain coarsening occurs by (say) cubic law:
G3
− G3
0 = Kt
where G, G0 are grain sizes at time t and 0, and if, G3
G3
0, then
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38. Final Stage Sintering: Geometrical Model
Phenomenological Sintering Equation
densification can be written as:
dρ
dt
=
K
t
; K =
ADlγsvΩ
KG3kBT
This equation is expected to be valid for both intermediate and final stage
sintering.
When grain growth is limited, shrinkage can be fitted to the following form:
l
l0
= Kt
1
β
where K is a temperature dependent parameter, and β is an integer.
See that the above equation has a form similar to the initial sintering stage
model.
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39. Sintering with Externally Applied Pressure
Hot Pressing
Simultaneous application of pressure and temperature.
Figure : Schematic of a Hot Press Unit
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40. Sintering with Externally Applied Pressure
Analytical Model for Hot Pressing
Coble’s model can be changed with an additional stress term.
Cv,neck =
Cv,∞γsvΩ
kBT
κ
where Pe is External Pressure= φPa; φ is the stress intensification factor, Pa is
the applied pressure. Therefore,
Cv,boundary = −
Cv,∞γsvPe
kBT
= −
Cv,∞γsvφPa
kBT
For the initial stage:
C = Cv,neck − Cv,boundary =
Cv,∞Ω4a
kBTx2
γsv +
Paa
π
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41. Sintering with Externally Applied Pressure
Creep
Creep: Deformation due to
diffusion of atoms from
interfaces subjected to a
compressive stress (higher
chemical potential) to those
subjected to a tensile stress.
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44. Sintering with Externally Applied Pressure
Dislocation Creep
Application of higher stress induces matter transport by dislocation motion.
˙ =
ADµb
kBT
Pa
µ
n
Or
˙ ∝ Pn
a
Intermediate Stage
1
ρ
dρ
dt
= A
Dµb
kBT
Paφ
µ
n
Final Stage
1
ρ
dρ
dt
= B
Dµb
kBT
Paφ
µ
n
A, B are numerical constants.
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45. Sintering with Externally Applied Pressure
Densification rate in Hot Pressing
Since in the hot press, one of the dimension stays fixed, densification rate is
proportional to the rate of change in the thickness of the compact.
1
1
l
dl
dt
=
1
d
d(d)
dt
=
1
ρ
dρ
dt
So, simply, linear strain represents the densification rate. Can be obtained by
the travel distance of the hot press ram (plunger).
The driving force for sintering in hot press is the two different forces added
together: DF due to curvature and DF due to applied pressure.
DF = Pe + γsvκ = Paφ + γsvκ
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46. Sintering with Externally Applied Pressure
Hot Pressing Mechanisms
1
ρ
dρ
dt
=
HDφn
GmkBT
Pn
a
where H is a numerical constant
D is the diffusion coefficient
φ is the stress intensification factor
G is the grain size
m is the grain Size exponent
n is the stress exponent.
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47. Sintering with Externally Applied Pressure
Hot Pressing Mechanisms
Mechanism m n Diffusion Coeffi-
cient
Lattice diffusion 2 1 Dl
GB diffusion 3 1 Dgb
Plastic deformation 0 ≥3 Dl
Viscous flow 0 1 -
Grain boundary sliding 1 1 or 2 Dl or Dgb
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