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- Advances in Glass Science and Technology
- Fundamentals of Inorganic Glasses
- Advances in Glass Science and Technology
- Introduction to Glass Science and Technology
Advances in Glass Science and Technology
Li erco f or m ns s Tra nge. Chapter 2! Time of Heat Treatment 2. Tm Metastable Zone of Undercooling Tc. Thermodynamics supports an increase in rates as the temperature decreases due to an increase in G. Kinetics lead to a rate decrease as the temperature decreases due to decrease in ion mobility diffusion coefficients decrease. Growth can occur at any temperature below the melting point Tm provided a nucleus is present from any source, i.
Nuclei do not have to be precipitated from the melt. Critical radius size is a result of competing terms. Gv formation of volume reduces the free energy of the system, while formation of surface increases the free energy. The net effect must be a decrease in free energy for formation of a stable nucleus. It follows that there must exist a zone of metastability for nuclei. The high viscosity at the melting point indicates a large kinetic barrier to crystal growth low diffusion coefficients.
Since the atoms cant rearrange from the liquid structure to form a crystalline network, a glass will form. Even if nuclei are present, growth is too slow to all significant crystal formation. In this case, the viscosity is low at the melting point, which would allow growth to occur if the melt were held in this temperature region and nuclei were present. However, the rapid increase in viscosity with decreasing temperature means a rapid increase in the kinetic barrier to nuclei formation with decreasing temperature and a very slow nucleation rate by the time the temperature decreases below the critical temperature for stable nuclei.
Homogeneous nucleation hence does not contribute to crystallization. If no heterogeneous nuclei are present, growth does not occur. Chapter 3! The oxide which forms the structural network of the glass and makes glass formation possible. Oxides which do not participate in network formation, but serve primarily in silicate melts to lower the temperature needed to produce a fluid melt. Oxides which are used primarily to adjust properties of the final glass to meet commercial requirements. They often partially counteract the fluxing contribution of the modifier oxides.
Oxides which alter the color of the glass. These oxides are often added in very small quantities and have little effect on the other properties of the glass. Elements which can form colloids Au, Ag, Cu! Agents added in small quantities to aid in removal of bubbles from the melt. These oxides also have little effect on the common properties of the glass. Calculate the batch weights of each component needed to yield 50 grams of glass for each of the following compositions.
Indicate the total batch weight, the molecular weight of the glass, and the weight of each component for each case. Express the following compositions in stoichiometry formulae. Write the general oxide formula for a series of glasses where! As 1-x Sx! Why is there an optimum size for the sand used in glass melting, i.
The batch-free time will be too long. This effectively slows the melting process and again leads to inhomogeneous melts and long batch-free times. Describe the process of dissolution of a grain of sand in a glass in which the batch contains NaCO3. Decomposition of the carbonate to form very fluid Na2O plusCO2gas. The release of gas causes foaming and stirring of the melt.
The stirring action can improve homogeneity. Reaction of sodium oxide at the surface of sand grains produces very fluid sodium silicate liquid. The melt gradually becomes more viscous as the silica content of the liquid increases. Melting rate slows. With time, diffusion results in a homogeneous melt.
Stirring by convection, bubbles rising, or mechanical means speeds the homogenizing process. Calculate the volume in liters of CO2 released during the preparation of 1 kilogram of a glass with the composition 25 Na2O - 75 SiO2.
Why does replacement of sodium carbonate by NaOH accelerate melting of a soda-lime- silicate batch? The sodium oxide reacts with the sand as discussed in question 2. Water acts as a strong flux, reducing the melting temperature of the sand and other refractory components of the batch.
Water vapor also forms bubbles, which rise to the surface. The rising bubbles stir the batch and aid in homogenization and fining. State WHY the following reduce alkali volatilization losses from melts. Rate of loss of alkali is a function of temperature, which decreases with decreasing temperature. This process is similar to evaporation of a liquid, e. Covering the melt increases the partial pressure of alkali vapor in the atmosphere above the melt.
Once the partial pressure of alkali vapor reaches the equilibrium value for the melt composition and temperature, alkali will leave and re-enter the melt at equal rates. If the melt is not covered, the alkali vapor is continuously removed from the vicinity of the melt surface and evaporation of alkali continues.
Discuss the use of As2O5 as a fining agent. Describe how this oxide serves to both increase the rate of bubble rise and to increase dissolution of gases from bubbles. Indicate the conditions under which each process occurs. Arsenic is usually added to melts in the form of As2O3. A nitrate, e. KNO3 is usually also added to these batches. During the initial heating of the batch, the nitrate decomposes, oxidizing the arsenic to the pentavalent state.
Release of O2 and NOx during this process produces bubbles, which stir the melt and sweep smaller bubbles to the surface.
Continued heating to a higher temperature shifts the equilibrium described by the equation above toward trivalent arsenic, releasing more oxygen, This oxygen diffuses into nearby bubbles, increasing their diameter and thus increasing their rise rate. Lowering the temperature after homogenization of the melt shifts equilibrium back toward the pentavalent state, which results in absorption of oxygen from the melt to bond to the arsenic.
Nearby bubbles shrink until they are no longer stable, at which point they will disappear. The melt density is 2. Use Stokes Law. Discuss the rationale for bubbling helium through a glass melt as an aid in removing bubbles.
Bubbling helium will produce large bubbles which rise rapidly, sweeping smaller bubbles to the surface. Helium also diffuses rapidly in melts, so that it can enter existing bubbles and increase their diameter. After bubbles are removed, any remaining helium can diffuse rapidly to the surface and be removed without forming additional bubbles or leading to reboil.
List and describe the 4 major sources of bubbles in glass forming melts. These gases are trapped between particles as the melt is formed. Their volume is limited to the free spaces between batch particles. They contribute to foaming during the early stages of melt formation. Release of carbon dioxide, nitrous oxides, halides, water vapor, etc. These gases are reactive and can bond to the network in the form of carbonate, hydroxyl, etc.
They produce foaming during the early stages of melting, which may actually improve initial fining. At later times, however, the tend to become supersaturated, which results in the formation of new bubbles in a bubble-free melt. Supersaturation can occur by several methods.
The term indicates a change in conditions whereby a gas which was originally present in concentrations below its solubility limit now exceeds its solubility limit. Carbon dioxide, for example, is very soluble in alkali-rich liquids, but much less soluble in silica-rich liquids.
The sodium oxide and high sodium silicates produced during the initial stages of melting can thus contain a large concentration of carbon dioxide. As the sand dissolves into this liquid, the solubility of carbon dioxide decreases until the amount present exceeds the solubility limit and carbon dioxide precipitates into the melt and forms bubbles. Changes in the oxidation state of polyvalent cations can change the solubility of oxygen in the melt.
Changes in furnace atmosphere can change the solubility of sulphur in melts. The solubility of a few gases is very temperature dependent. This is especially true for sulphur compounds. If the solubility is high at a high temperature, the gas will be dispersed through the melt and not occur in bubbles.
If cooling the melt reduces the solubility, the gas will become supersaturated, precipitate from the melt, and bubbles will form. This frequently occurs during reheating of soda-lime-silicate glasses. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel.
Fundamentals of Inorganic Glasses
Fundamentals of Inorganic Glasses, Third Edition, is a comprehensive reference on the field of glass science and engineering that covers numerous, significant advances. This new edition includes the most recent advances in glass physics and chemistry, also discussing groundbreaking applications of glassy materials. It is suitable for upper level glass science courses and professional glass scientists and engineers at industrial and government labs. Fundamental concepts, chapter-ending problem sets, an emphasis on key ideas, and timely notes on suggested readings are all included. The book provides the breadth required of a comprehensive reference, offering coverage of the composition, structure and properties of inorganic glasses. Upper level undergraduate and professionals working in inorganic glasses and inorganic chemistry, as well as researchers working with glass in related fields of ceramic engineering, chemical engineering, mechanical engineering, physics, chemistry, and geosciences. Introduction 2.
Introduction to Glass Science and. Technology. Second Edition. James E. Shelby. New York State College of Ceramics at Alfred University. School of.
Advances in Glass Science and Technology
In this book, some recent advances in glass science and technology are collected. In the first part, the structure and crystallization of innovative glass compositions are analysed. In the second part, innovative applications are described from the use of glass in optical devices and lasers to fibres in composites, micropatterned components in sensors and microdevices, beads in building walls and
Presenting the fundamental topics in glass science and technology, this concise introduction includes glass formation, crystallization, and phase separation. Glass structure models, with emphasis on the oxygen balance method, are presented in detail.
Introduction to Glass Science and Technology
Scientific study attempts to explore and understand the working of the physical world. Science and technology research in nanotechnology promises breakthroughs in areas such as materials and man-ufacturing, nanoelectronics, medicine and healthcare, energy, biotechnology, information technology, and na-tional security. Does it matter?
The published report was ordered by the House of Lords to be printed 23 February The authors present complex issues in an accessible and engaging form. The importance of science and technology in our modern world cannot be overstated. The text outlines the contributions that this field has provided in health, industries, agriculture, transportation, and communication.
Request PDF | On Jan 1, , James E. Shelby published Introduction to Glass Science and Technology | Find, read and cite all the research you need on.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Homework: Ten sets of homework problems related to various chapters in the text and to the classroom lectures will be assigned, collected and graded. Each homework set is worth 20 points and must be turned in before class on the date indicated for full credit to be awarded.
ОБЪЕКТ: ДЭВИД БЕККЕР - ЛИКВИДИРОВАН Коммандер опустил голову. Его мечте не суждено сбыться. ГЛАВА 104 Сьюзан вышла из комнаты. ОБЪЕКТ: ДЭВИД БЕККЕР - ЛИКВИДИРОВАН Как во сне она направилась к главному выходу из шифровалки. Голос Грега Хейла эхом отдавался в ее сознании: Сьюзан, Стратмор меня убьет, коммандер влюблен в .
Но кровь… - Поверхностная царапина, мадам.
Коммандер был абсолютно убежден в том, что у Хейла не хватит духу на них напасть, но Сьюзан не была так уж уверена в. Хейл теряет самообладание, и у него всего два выхода: выбраться из шифровалки или сесть за решетку. Внутренний голос подсказывал ей, что лучше всего было бы дождаться звонка Дэвида и использовать его ключ, но она понимала, что он может его и не найти. Сьюзан задумалась о том, почему он задерживается так долго, но ей пришлось забыть о тревоге за него и двигаться вслед за шефом. Стратмор бесшумно спускался по ступенькам.
Водитель отказался его впустить. Машина была оплачена человеком в очках в тонкой металлической оправе, и он должен был его дождаться. Беккер оглянулся и, увидев, как Халохот бежит по залу аэропорта с пистолетом в руке, бросил взгляд на свою стоящую на тротуаре веспу. Я погиб. Халохот вырвался из вращающейся двери в тот момент, когда Беккер попытался завести мотоцикл.
Второй - с помощью ручного выключателя, расположенного в одном из ярусов под помещением шифровалки. Чатрукьян тяжело сглотнул. Он терпеть не мог эти ярусы. Он был там только один раз, когда проходил подготовку. Этот враждебный мир заполняли рабочие мостки, фреоновые трубки и пропасть глубиной 136 футов, на дне которой располагались генераторы питания ТРАНСТЕКСТА… Чатрукьяну страшно не хотелось погружаться в этот мир, да и вставать на пути Стратмора было далеко не безопасно, но долг есть долг.
- Мидж зло посмотрела на него и протянула руку. - Давай ключ.