Glass

History

Biology

The alive species largest producing of glass is not the man, but the family of the Diatomées. Indeed, these Algue S unicellular is protected by a hull from glass to the surprising and delicate forms. Although one is unaware of still the detail of the Synthèse starting from the Silicate S present in sea water, it is indeed glass. Component of the Plankton, the mass of this glass is considerable and quite higher than the human production.

This manufacture takes place under physical conditions related to the soft Chimie, i.e. it does not require of Température, nor of Pression high.

The main interest of glass for the diatom is not to make obstacle with the Photosynthèse while letting pass the light. It is synthesized very quickly at the time of the Méïose.

Applications

Glass is used primarily in Optique for its refringent properties (lenses, glasses of glasses).

It is also used in Chimie and in industry Agroalimentaire: it reacts very little with the majority of the compounds used in these fields, it is thus an ideal material for the containers (bottles, pots of yoghourt, Bécher S, Erlenmeyer S, fractionating column, test-tube S, test tubes…). One of only the Liquid S having the capacity to dissolve glass is the hydrofluoric Acid (HF).

Glass is the material in which the nuclear waste are confined of high activity (HAVL) by the process of vitrification. Indeed its disordered structure makes it possible to absorb part of radiations.

Glass is also a very important Construction material in the modern Architecture and industry Automobile. It is in particular present in the form of insulator, glass wool light, Imputrescible and non flammable.

The artistic uses of glass are innumerable since the origins. They accompanied by many technical innovations (molten glass, fusing, thermoforming, etc).

In many applications, glass is currently replaced by Polymère S (plastics).

Industry

For the manufacture of flat glass (window glass, for example), to see Industry of glass.

For the manufacture of the wire rolled glass (produced semi finished allowing to produce bulbs, bottles or glassmaking of laboratory), to see Glass wire rolled.

At the industrial level, glass often undergoes surface treatments (generally of the deposits) so that the final material is harder, anti-reflecting (application: lenses) or Hydrophobic (application: avoid-break) .

Heat treatments make it possible to improve resistance of the pièces : the side and back panes of the cars as certain parts of furnishing are soaked by a fast and controlled cooling, generally using air.

Avoid-break Automobile S are out of laminated glass (glass-plastic-glass layers, also called " glass feuilleté"). Thus, at the time of a shock, the windshield breaks, but remains in place. The passengers are less likely to be wounded by breakings.

Calculation of properties

The properties of glass can be calculated by the analysis Statistique of the databases of glass, for example SciGlass and Interglad. If the desired property of glass is not related on the Cristallisation (for example, the temperature of liquidus) or to the separation of phase, the linear regression can be applied by using functions Polynôme S communes until the third degree. Below figure is an equation of example of the second degree. The C - values are the component concentrations of glass like Na₂O or CAD expressed as a percentage or other fractions, the B - values are coefficients, and N is the total figure of the components of glass. The principal component of glass, the Silica (SiO₂), is excluded in the equation below because of with-top-parameterization, which had with the constraint that all the components summarize at 100%. Many terms in the equation below can be neglected by means of the analysis of correlation and significance. Other details and examples are available on the Glassproperties.com site.

Property of glass = $b_0 + \ sum_ {I = 1} ^n \ left (b_i C_i + \ sum_ {K = I} ^n b_ {ik} C_i C_k \ right)$

Often it is required to optimize several properties of glass simultaneously, including the production costs. This can be carried out using the Solveur-tool in Microsoft Excel as follows:

to list desired properties;
to enter of the models for the reliable calculation of the properties based on the composition of glass, including a formula to estimate the production costs;
to calculate the places of the differences (errors) between the desired and calculated properties;
to reduce the sum of square errors by using the option of Solveur in Microsoft Excel, with the components of glass like variables.

It is possible to weigh the differently wished properties. Basic information on the principle can be found in the article: NR. T. Huff, A.D. Call: " Computerized Prediction off Knell Compositions from Properties (automated Forecast of compositions of glass of the properties) " ; J. amndt Ceram. Plowshare, vol. 56,1973, p 55-57.

Artisanal techniques

The Verrerie also constitutes an artisanal activity.

work of glass to the flame : the glassmakers work starting from tubes and of rods of Verre stretched which they softened using the flame of a blowtorch to transform it by the breath or various tools. In France, the work of glass blown with the flame for the realization of decorative, utility objects or of single parts is practiced more only by one ten craftsmen such as Dominique, Ludovic and Nicolas Guittet, Jean Pierre Baquère, Alain Villechange, Pascal Philibert (Better workman of France)
puffed up Verre

The glass-blowers make heat a ball of glass at the end of a cane (hollow metal tube), and blow in this cane to make inflate glass and carry out the interior vacuum. Then, they stretch, flatten, bore this ball to give him its final form. Once hardened, some dull it to carry out reasons.

Crystal

Glass with high content of Lead which gives him a more intense glare and is worked similarly with glass.

Molten glass

The mussel of the part to be realized manufactures itself in a material Réfractaire (containing kaolin e.g.) according to various techniques of which the lost wax, for example. After cooking, according to stages of heating intended to avoid the cracks, the mould is cooled and furnished with powders or with granulated with glasses coloured variously according to the required decoration. A new cooking with place and, after cooling, the mould is destroyed delicately by a chemical or mechanical means to release the part whose form and colors will have been controlled perfectly. This technique allotted to the Egyptians, was reinvented almost simultaneously by Henry Cros, François Décorchemont and Georges Desprets in the second part of the 19th century. Amalric Walter, Gabriel Argy-Rousseau is illustrated there. Today, a score of artists in the world, more or less alchemist S and jealous to know to them to make, are still devoted to it. One counts among them brothers Antoine and Etienne Leperlier (small wire of Décorchemont), Yan Zoritchak, Bernard Dejonghe, Olivier Juteau, Matei Negreanu, Jacques Lubtchansky, Keith Brokelhurst, Diana Hobson, the house Daum, Lila Farget, etc

Thermoforming

This technique consists in posing one cold (or several) glass leafs, possibly coloured, on a refractory of which she will marry the relief with cooking.

Calcining

Composition of glass, being able to be coloured (using metallic oxides), carried to fusion and soaked in a cool water bath in order to reduce it in pellets being used for the development of enamels or “balottes” (bars) coloured, basic materials of the glassmakers.

Cueiller

Action to take a mass of glass in the furnace using a cane or of a Pontil.

Pontil

Full metal tube, the Pontil allows a setting forms some with the “marble” or using various tools. It is also used for separation of the object of the cane in order to bore and work the collar, to bring back elements of decoration, handles, a foot.

Recycling of glass

The worn bottles of glass can be molten. The matter thus recovered makes it possible to manufacture new bottles. Glass can be recycled indefinitely without losing its qualities.

Glass can also be produced starting from cullet (crushed glass) of recovery. The manufacture of glass starting from cullet of recovery saves raw materials and energy.

Before being remelted, glass undergoes various treatments: crushing, washing, elimination of the adhesives, labels, capsules, separation of glass and metals and elimination of the rejects (porcelain, stones…).

In France, glass is recovered to be recycled. Germany chose another system of re-use: the Instruction. In this system the bottles are recovered whole, washed then re-used. Canada uses a similar system in Germany and standardized the format of the beer bottles to facilitate the re-use by various companies.

Physicochemistry

This part approaches glass and its characteristics from a physicochemical point of view. In this part, we will limit our study to glasses of Oxyde S. Cependant, it exists different great types of glasses, in particular, metal glasses (compounds only of lic elements Métal) and the glasses of spin (crystallized compounds characterized by an absence of a magnetic nature at long distance, from where them name).

Structure

Glass is a material Amorphe, i.e. not Cristal flax. So it presents an important structural disorder. Its microscopic structure is such as it does not exist any order at long distance in glass. Glass can even be seen like a " réseau" three-dimensional, similar to that of a crystal, but in which only the order at short distance is preserved.

Let us compare, for example, the structure of the Silice (SiO ₂) crystalline (in its form Cristobalite) and that of silica glass.

In both cases, each Atome of Silicium is dependant with four atoms of Oxygène, thus forming Tétraèdre S SiO ₄ ; each tetrahedron which can be regarded as a " brique" final building. But while cristobalite can be defined like a regular stacking of these bricks SiO ₄, the silica glass can be seen like an anarchistic stacking as of these same bricks SiO ₄.

Because of its amorphous structure, glasses produce, in diffraction of X-rays (DRX), a halation of diffusion, contrary to the crystals which give narrow and intense peaks.

Main components

Because of its amorphous structure, glass is subjected to very few stoechiometric constraints . So glass can include in its center a very large variety of elements and present very complex compositions.

In oxide glass, these various elements are in a ic form Cation, in order to form Oxyde S with the Anion Oxygène O^2-.

The cations intervening in the composition of glasses can be classified in three categories according to the structural part which they play during vitrification (formation of glass): trainers of network, not-trainers of network (or modifiers of network) and intermediaries. The structural criteria of this classification take into account the number of coordination (many oxygen atoms on which are dependant the cation) and the strengths bonding.

Trainers of network

The trainers of network are elements which can alone form glass. The formative elements most current are the Silicium If (in its form SiO₂ oxidizes), the Bore B (in its form B₂O₃ oxidizes), the Phosphore P (in its form P₂O₅ oxidizes), the Germanium Ge (in its form GeO₂ oxidizes) and the Arsenic As (in its form As₂O₃ oxidizes).

In fact metal elements of rather high valence (generally 3 or 4, sometimes 5) form covalent connections mid- mid- ionic with the oxygen atoms. They give Polyèdre S of weak Coordinence (3 or 4), like SiO₄, BO₄ or BO₃. These polyhedrons are bound by their tops and form the vitreous network.

Modifiers of network

The modifiers of network (or not-trainers) cannot form glass alone. They are primarily the alkaline S, the alkaline-earth and to a lesser extent some metals transition and the Rare earths.

They are usually bulkier (more important ionic ray) than the trainers of network, slightly charged and give polyhedrons of great co-ordination number. Their connections with the oxygen atoms are more ionic than those established by the trainers.

They can have two quite distinct structural roles, either true modifiers of network, or compensation of load.

the true modifiers of network break the connections between the polyhedrons of the vitreous network causing a depolymerization of this last. They then transform bridging oxygens, which bind two formative elements of network, out of not-bridging oxygens, related to only one trainer of network. This is translated on the scale Macroscopique by a reduction in the Point melting and Viscosité.

the compensators of load as for them compensate for a negative charge on a formative polyhedron of network, for example BO₄^-, enabling him to be stable in this configuration.

Intermediaries

The intermediate elements have various behaviors: some of these elements are either formative, or modifying according to the composition of glass while others will have neither one nor the other as of these functions but an intermediate role.

The principal intermediate elements in oxide glasses are the Aluminum Al, the Fer Fe, the Titane Ti, the Nickel Ni and the Zinc Zn.

Coloured centers

metals and metal Oxyde S can be added during the manufacturing process of glass to influence its Couleur. The addition of a small quantity of Manganèse makes it possible to wear the nap off the green color produced by the Fer. concentration S more raised, it allows obtaining a color close to that of the Améthyste. Just as manganese, the Sélénium used in small quantity makes it possible to fade glass. A larger quantity produces a red color. Glass is dyed in blue by the addition of a weak concentration of Cobalt (0.025 to 0.1%). The oxide of tin and the oxides of Antimony and Arsenic make it possible to produce opaque white glass. This process was used for the first time at Venice to obtain an imitation of Porcelaine. The addition from 2 to oxide 3% of Cuivre produces a turquoise color. The metal addition of Copper pure led to red glass very dark, opaque, sometimes used like substitute with the Ruby gilded. According to the concentration used, the Nickel makes it possible to produce blue, purple glasses or even blacks. The addition of Titane leads to yellow-brown glass. The metal gold added to very weak concentrations (neighbors of 0.001%) makes it possible to obtain a coloured glass ruby, while weaker concentrations still lead to glass of less intense red, often presented like " currant ". Uranium (0.1 to 2%) can be added to give to glass a yellow or green color fluorescent. Glass with uranium is not enough radioactive to be dangerous. On the other hand, if it is crushed to form a powder, for example by polishing it with Sandpaper, the powder can be carcinogenic by inhalation. The compounds containing money (in particular the Silver nitrate) make it possible to obtain colors in a range going from the orange red to the yellow. The color obtained by the addition of these various additives depends significantly on the way in which glass was heated and cooled during the manufacturing process.

Vitreous transition

From a Thermodynamic point of view, glass is obtained starting from a phase Liquide superfused solidified at the point of vitreous Transition, Tg.

For a given composition, one is interested in the variation of a thermodynamic size like the Volume occupied by this phase (by maintaining the constant Pression) or one of the energy thermodynamic functions molar, like the Enthalpie H, for example (one could also have chosen the energy interns U).

We interest in the cooling of a liquid. A priori, for Temperature S lower than the Melting point T_f (T_f depends on the pressure), the most stable state thermodynamically corresponds at the smooth state Cristal (the lowest possible enthalpy). In T_f, one observes a variation of H then as well as a break of slope of H (this slope is much weaker for a solid than for a liquid).

But if, during the cooling of the liquid, the Viscosité is too important or the very fast cooling, the Cristallisation does not have time to occur and a liquid superfused is then obtained. No discontinuity of H is then observed in T_f and its slope remains unchanged. By continuing cooling, the viscosity of the liquid increases exponentially and the superfused liquid becomes almost solid. When it reaches 10¹³ Poise S, rigidity prevents the movements Microscopique S buildings and one observes a break of slope of the enthalpy (the slope becomes the same one as for that of the crystallized compound). The temperature to which this change occurs calls temperature of vitreous transition, T_g . For a temperature lower than T_g, the material is a solid with the structural disorder of a Liquide: it is glass. The disorder, and thus the Entropy, are higher in glass than in a Cristal.

The continuous passage of the liquid state in a vitreous state is done in a beach of temperature delimited by the melting point (T_f) and the temperature of transition vitreous (T_g) and called zone from vitreous transition . In lower part of Tg, the time of Relieving necessary to reach the balance of configuration (crystallized state) is then higher than the time of experiment. Thus, glass is a material Métastable, inevitably evolving to the crystalline state but being able to persist in a vitreous state over very long periods of time. It is the case for example of the Obsidienne, glass Volcan ic naturalness, which one can find specimens old several million years.

In spite of its strong viscosity, glass preserves certain properties of the liquids of which in particular disordered character, but contrary to the usual liquids its relaxation time is considerable and glass cannot " couler" on human time scales. Thus according to Daniel Bonn, of the statistical Physics laboratory of the ENS, if the stained glasses of the Cathedral S, or the ices of the Galerie of the Ices to the Château of Versailles are thicker at the base than at their top, it is because of the manufactoring process used. If the description of glass as an extraordinarily viscous liquid is not completely unfounded, it thus remains very debatable.

Chemical resistance and Deterioration of glass

Industrial glass has good compatibilities with the majority of the chemical compounds, on the other hand the hydrofluoric Acid (HF) degrades glass easily.

Glasses are not insensitive with the action of the Eau or the Air. Of course, that does not prevent the existence of glasses having several million years and nonfaded because the sensitivity of glasses to deterioration depends on their chemical composition.

Other materials

By extrapolation the name of glass is employed for other materials Amorphe S. Certains metal alloys can be solidified with an amorphous structure thanks to a very fast cooling, one calls then them metal glasses. One can for example project the Métal in fusion on a drum of revolving copper at high speed. These alloys are used for example for the transformer hearts of . Indeed them hysteresis loop is very weak, which reduces the losses by hysteresis considerably.

One can obtain metal alloy deposits (Al-Cu-Fe) amorphous by vacuum deposit (DEVELOPING COUNTRY).

Some Acier S can be solidified in amorphous form. Because of their isotropy, they have not-magnetic properties interesting in particular for the construction of furtive submarines. They also have a great hardness and a very good behavior with corrosion.

Symbolic system

Glass is one of first materials developped at the point, dreamed by the man. It is the Symbole of brittleness, smoothness and transparency (for example, the slipper of glass of Cendrillon in the cartoon of Walt Disney; and in the tale of Perrault. It is widespread that in the original tale the slipper would be of squirrel fur, but Perrault had written the original history with a slipper of glass, which was transformed into squirrel fur, before becoming again glass for the cartoon.

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