Technology & Engineering
Glass Microstructure
The glass microstructure refers to the arrangement and distribution of crystalline and non-crystalline components within a piece of glass. It includes features such as grain boundaries, phase composition, and defects, which influence the material's properties and behavior. Understanding the glass microstructure is crucial for designing and manufacturing glass products with specific mechanical, thermal, and optical characteristics.
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7 Key excerpts on "Glass Microstructure"
eBook - PDF- D Uhlmann(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
GLASS: SCIENCE AND TECHNOLOGY. VOL. 4B C H A P T E R 4 Electron-Microscope Studies of Glass Structure J. Zarzycki LABORATORY OF SCIENCE OF VITREOUS MATERIALS UNIVERSITY OF MONTPELLIER, FRANCE I. Introduction-Scope of Electron-Microscope Studies in Glasses 253 II. Imaging Modes 254 HI. Low-Resolution Studies 257 A. Direct Electron Microscopic Observations 257 B. Replica Techniques 259 IV. High-Resolution Studies 260 A. Diffraction Theory of Image Formation 260 B. Application to Amorphous Structures 265 C. Progress of HREM Studies in Glasses 267 V. Conclusions 270 References 270 I. Introduction: Scope of Electron-Microscope Studies in Glasses The structure of glasses can be studied at different levels of resolution. The diffusion of X-rays and neutrons (Chapter 5, Volume 4A) and different spectroscopic methods (Chapter 5, Volume 4A) confirm the existence of a short-range order, which, in a great majority of cases, is seen to be similar to that of parent crystalline phases. In the most favorable cases this local order is known up to 5 to 10A and constant efforts are made to extend this limit to higher values. On the other hand, in some glassy systems, phase separations may introduce textures the finest of which are in the range of 20 to 50A and which go up to several thousand angstroms. They can be followed by small-angle scattering of X-rays (SAXS) or of neutrons (SANS) (Chapter 5, Volume 4A). They are also currently studied by conventional electron microscopy, which is well adapted to this resolution range. Between these two limits is situated a region that may be defined as corresponding to a middle-range or intermediate order in which a very characteristic part of the structural organization of glasses is to be found. 253 Copyright © 1990 by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN 0-12-706707-8
- Pascal Richet(Author)
- 2021(Publication Date)
- Wiley-American Ceramic Society(Publisher)
2.3 Microstructure Analysis of Glasses and Glass Ceramics Christian Patzig and Thomas Höche Fraunhofer Institute for Microstructure of Materials and Systems IMWS, Halle (Saale), Germany 1 Introduction A homogeneous glass by definition lacks a microstructure at a scale larger than a few nanometers. As soon as actual inhomogeneities occur, in contrast, a detailed picture of their size, distribution, composition, and spatial arrangement becomes important to understand the properties of the material. In turn, the improved capabilities of microstructural studies in terms of spatial and elemental resolution are becoming increasingly important to optimize crystallization or phase separation and to achieve the desired microstructure and associated properties (Chapter 7.11). As a matter of fact, the beauty and challenge of glasses and glass ceramics is their diversity and complexity. The purpose of this chapter thus is to review the main microstructural methods commonly used to study inhomogeneous glass‐based materials. In preamble, however, it is important to note that studying extremely small volumes in great detail can result in “knowing everything about nothing.” In other words, it is critically important to make sure that the information gathered locally is actually representative for larger volumes. To achieve this goal, highly resolved information must be combined with additional integral measurements to get a broad picture. In addition, artifacts introduced upon either preparation or investigation of the sample must be avoided. And one should also be extremely careful with in situ microstructural experiments where, because of dramatic differences in the surface‐to‐volume ratio, annealing can easily lead to results not observed in the bulk
- Charles H. Drummond, Charles H. Drummond, III(Authors)
- 2011(Publication Date)
- Wiley-American Ceramic Society(Publisher)
68th Conference on Glass Problems · 247 This page intentionally left blank STRUCTURE, MICROSTRUCTURE AND REFRACTORY PERFORMANCE Nigel Longshaw CERAM Staffordshire, UK ABSTRACT The importance of modelling as a tool in design and development of refractory materials are considered. Both bulk refractory structures as well as refractory microstructures are considered. Theory on micromechanics of composites is applied to calculate effective material properties of microstructures. It is shown that microstructure modelling can be considered as part of the simulation driven material development process. INTRODUCTION Refractory and heat-insulating materials have the objective to manage and control high temperature processes economically. Furthermore, refractory materials help protect the environment by ensuring that high temperature processes do not have a harmful impact on our environment. Refractory materials can be stressed in the following ways: • thermally by temperatures and thermal shock, • chemically by gasses, liquids , melts, slags and • mechanically by pressure, tensile force, friction and/or impact Refractories are most always subjected to a combination of the above-mentioned stress factors. Consequently, the selection of appropriate refractory materials must take various stress factors into consideration. This is also true when developing refractory materials. The role of microstructure modelling in the process of Simulation Driven Material Development will be presented in the following paper, the procedure of obtaining real microstructure images for modelling and the calculation of effective material properties of the microstructure and determine unknown material properties through back calculation of physical test results. The basic theory behind micromechanics and it application in computational modelling are presented. It is widely accepted that refractories can be a key contributor to business profitability in the glassmaking industry.
eBook - PDFModern Materials
Advances in Development and Applications
- Bruce W. Gonser(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
ENGINEERING GLASS Errol B. Shand Technical Consultant on Glass and Ceramics, Corning, New York Page I. Nature and Chemical Composition 248 A. Definition 248 B. The Vitreous State 249 C. Chemical Composition 251 D. Devitrification 253 II. Manufacture 255 A. Raw Materials and Melting 255 B. Forming 256 C. Secondary Processes 257 III. Properties 259 A. Viscosity 260 B. Specific Heat and Thermal Conductivity 262 C. Emissivity 262 D. Thermal Expansion 262 E. Mechanical Properties 265 F. Optical Properties 271 G. Electrical Properties 273 H. Chemical Properties 276 IV. Engineering of Glass 277 Structural Design of Brittle Materials 278 V. Glass in Buildings 289 A. Glass Products 289 B. Large Panes 290 VI. Vehicle Glazing 296 A. Land Vehicles 296 B. Aircraft 297 C. Spacecraft 298 D. Deep Submergence Craft 300 VII. Industrial Uses 303 A. Piping 304 B. Other Equipment 306 C. Heating Panels 306 D. Fluid Amplifiers 306 E. Glass Lubricants 307 VIII. Lamp and Electronic Industries 307 A. Lamps 307 B. Electron Tubes 310 C. Electronic Circuit Components 311 D. Microwire 312 247 248 ERROL B. SHAND E. Radomes 312 F. Vacuum Switches 313 IX. Glass for Science 313 A. Linear Particle Accelerators 313 B. Radiation Absorbers 314 C. Bubble Chamber Windows 314 X. Summary 315 References 316 I. Nature and Chemical Composition Glass has characteristics that, collectively, are not found in other engineering materials. 1 It is transparent, hard, and brittle at ordinary temperatures, but becomes increasingly more fluid with rising tempera-ture. It is corrosion-resistant and is a good electrical insulator. Because of these unusual characteristics the principal applications of glass are found in somewhat specialized fields, and the technical approach to engineering problems involved is not always the same as for other materials. A. DEFINITION Glass is a ceramic material; that is, it is made from inorganic materials at high temperatures.
- David Brandon, Wayne D. Kaplan, David Brandon(Authors)
- 2008(Publication Date)
- Wiley(Publisher)
It is always a good idea to compare microstructural observations of porous materials with data on pore size and volume fraction determined from physical models using measurements based on density, porisometry or gas adsorption. 1.2 Crystallography and Crystal Structure The arrangements of the atoms in engineering materials are determined by the chemical bonding forces. Some degree of order at the atomic level is always present in solids, even in what appears to be a featureless, structureless glass or polymer. In what follows we will briefly review the nature of the chemical forces and outline the ways in which these chemical forces are related to the engineering properties. We will then discuss some of the 24 Microstructural Characterization of Materials crystallographic tools needed to describe and understand the commonly observed atomic arrangements in ordered, crystalline solids. The body of knowledge that describes and characterizes the structure of crystals is termed crystallography. 1.2.1 Interatomic Bonding in Solids It is a convenient assumption that atoms in solids are packed together much as one would pack table tennis balls into a box. The atoms (or, if they carry an electrical charge, the ions) are assumed to be spherical, and to have a diameter which depends on their atomic number Figure 1.17 The volume fraction of a second phase can be determined from the areal fraction of the phase, seen on a random planar section, or from the fractional length of a random test line which intercepts the second phase particles in the section, or from the fraction of points in a test array which falls within the regions of the second phase. The Concept of Microstructure 25
eBook - ePub- Hani M. Tawancy, Anwar Ul-Hamid, Nureddin M. Abbas(Authors)
- 2004(Publication Date)
- CRC Press(Publisher)
8 Materials Characterization 8.1 Introduction Materials characterization is almost always involved in failure analysis investigations. It requires knowledge of the overall composition of the material, as well as its microstructural features. Chemical composition refers to the elemental constituents of the material and their concentrations. By definition, microstruc- ture refers to the internal structural features of a material which cannot be visually observed. They are to be distinguished from macrostructural features such as large cracks, porosity, and fracture characteristics which can be observed either visually or by using a low-power hand lens. Complete microstructural characterization of a given material requires determination of (i) morphology (size, shape, and distribution of all phases present), (ii) crystal structure of all phases present, and (iii) elemental composition of all phases present, including localized segregation and depletion. Since some techniques for chemical analysis are associated with certain methods used to reveal the microstruc- ture, techniques for microstructural characterization are described first. Various techniques for chemical analysis are described in Sec. 8.3. As described below, there are various techniques available for microstructural characterization. Selection of one technique or another depends upon the type of information required. 8.2 Techniques for Microstructural Characterization Microstructural features of a material are revealed by means of a high-power microscope. Its primary function is to form an image of an object, as schematically illustrated in Fig. 8.1. To observe the microstructure of a material, a representative specimen is illuminated by a suitable source of radiation. Radiation emitted by the specimen is then gathered by an objective lens and focused into an image
eBook - PDFLaser Processing of Engineering Materials
Principles, Procedure and Industrial Application
- John Ion(Author)
- 2005(Publication Date)
- Butterworth-Heinemann(Publisher)
Atomic packing and bonding influences material properties, and electronic configurations play a central role in determining the interaction between the photons of the laser beam and the material. The microstructure, on the order of micrometres (10 − 6 m), is governed by arrangements of atoms and molecules in discrete phases. Microstructural changes are induced through the thermal cycles generated during laser processing, which can be illustrated using various phase transformation diagrams. The macrostructure, on the order of millimetres (10 − 3 m), is used as the basis for design calculations to determine engineering performance. Fundamental mechanical and thermal properties are influenced by structure on all three levels. The chapter also introduces the most common industrial materials. Their composition, structure and properties are described, to reveal the philosophy that underlies their design. Strengthening mechanisms, introduced by alloying or thermomechanical treatments, are described – these are affected by the thermal cycles induced during laser processing. These materials make regular appearances in the chapters that follow. Those properties that control the thermal response of materials are displayed on charts, which indicate behaviour during laser processing and play an important role in the selection of materials for laser processing. 140 Laser Processing of Engineering Materials Atomic Structure The atomic structure of engineering materials describes the bonding between atoms, the packing of the atoms, and the distribution of electrons. Metals and Alloys Bonding The atomic structure of metals and alloys is determined by the metallic bond. Electrons are freely shared by atomic nuclei (positive ions). On average, each nucleus is surrounded by sufficient electrons to maintain a full outer shell. Electrostatic attraction between the positive nuclei and the negative electron ‘cloud’ constitutes the metallic bond.
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