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74-423: Nepheline crystals are rare and belong to the hexagonal system, usually having the form of a short, six-sided prism terminated by the basal plane . The crystals appear to have more symmetry than they actually possess, but unsymmetrical etched figures produced artificially on the prism faces indicate that the crystals are hemimorphic and tetartohedral , the only element of symmetry being a polar hexad axis. Nepheline

148-401: A bank of 5–20 identical sections, each of which contains one complete set of mechanisms to make containers. The sections are in a row, and the gobs feed into each section via a moving chute, called the gob distributor . Sections make either one, two, three or four containers simultaneously (referred to as "single", "double", "triple" and "quad" gob). In the case of multiple gobs, the "shears" cut

222-424: A ccp arrangement of atoms is the face-centered cubic (fcc) unit cell. This is not immediately obvious as the closely packed layers are parallel to the {111} planes of the fcc unit cell. There are four different orientations of the close-packed layers. One important characteristic of a crystalline structure is its atomic packing factor (APF). This is calculated by assuming that all the atoms are identical spheres, with

296-403: A day 7 days a week. This means that there is little opportunity to either increase or decrease production rates by more than a few percent. New furnaces and forming machines cost tens of millions of dollars and require at least 18 months of planning. Given this fact, and the fact that there are usually more products than machine lines, products are sold from stock. The marketing/production challenge

370-438: A geographical business; the product is heavy and large in volume, and the major raw materials (sand, soda ash and limestone) are generally readily available. Therefore production facilities need to be located close to their markets. A typical glass furnace holds hundreds of tonnes of molten glass, and so it is simply not practical to shut it down every night, or in fact in any period short of a month. Factories therefore run 24 hours

444-599: A lattice system. Of the 32 point groups that exist in three dimensions, most are assigned to only one lattice system, in which case the crystal system and lattice system both have the same name. However, five point groups are assigned to two lattice systems, rhombohedral and hexagonal, because both lattice systems exhibit threefold rotational symmetry. These point groups are assigned to the trigonal crystal system. In total there are seven crystal systems: triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. The crystallographic point group or crystal class

518-413: A radius large enough that each sphere abuts on the next. The atomic packing factor is the proportion of space filled by these spheres which can be worked out by calculating the total volume of the spheres and dividing by the volume of the cell as follows: Another important characteristic of a crystalline structure is its coordination number (CN). This is the number of nearest neighbours of a central atom in

592-438: A variety of faults. Typical faults include small cracks in the glass called "checks" and foreign inclusions called "stones" which are pieces of the refractory brick lining of the melting furnace that break off and fall into the pool of molten glass, or more commonly oversized silica granules (sand) that have failed to melt and which subsequently are included in the final product. These are especially important to select out due to

666-400: A vector normal to the plane. Considering only ( hkℓ ) planes intersecting one or more lattice points (the lattice planes ), the distance d between adjacent lattice planes is related to the (shortest) reciprocal lattice vector orthogonal to the planes by the formula The crystallographic directions are geometric lines linking nodes ( atoms , ions or molecules ) of a crystal. Likewise,

740-505: Is "at infinity"). A plane containing a coordinate axis is translated so that it no longer contains that axis before its Miller indices are determined. The Miller indices for a plane are integers with no common factors. Negative indices are indicated with horizontal bars, as in (1 2 3). In an orthogonal coordinate system for a cubic cell, the Miller indices of a plane are the Cartesian components of

814-473: Is a massive form of translucent nepheline with a darker color and greasy luster. Because of its high alumina content, iron -free nepheline is valued for use in glass manufacturing in place of feldspar. Most of the nepheline used for this purpose comes from Ontario . Nepheline produced as a byproduct of apatite mining in the Kola Peninsula has found uses in ceramics, leather, rubber, textiles, wood, and

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888-430: Is a wide miscibility gap between nepheline and kalsilite, similar to the miscibility gap between microcline and albite . A composition falling in this gap will experience exsolution as it cools, where nepheline and kalsilite separate into separate microscopic layers (lamellae). Nephelinite is a rock-forming mineral found in silica-poor igneous rocks . These include nepheline syenite , foidite , and phonolite . It

962-425: Is applied either using a safe organic compound or inorganic stannic chloride . Tin based systems are not the only ones used, although the most popular. Titanium tetrachloride or organo titanates can also be used. In all cases the coating renders the surface of the glass more adhesive to the cold end coating. At the cold end a layer of typically, polyethylene wax , is applied via a water based emulsion . This makes

1036-441: Is common, however the environmental impact of washing containers as against remelting them is uncertain. Factors to consider here are the chemicals and fresh water used in the washing, and the fact that a single-use container can be made much lighter, using less than half the glass (and therefore energy content) of a multiuse container. Also, a significant factor in the developed world's consideration of reuse are producer concerns over

1110-406: Is created by the forming machines. Operated by compressed air, they can produce noise levels of up to 106 dBA . How this noise is carried into the local neighborhood depends heavily on the layout of the factory. Another factor in noise production is truck movements. A typical factory will process 600 T of material a day. This means that some 600 T of raw material has to come onto the site and

1184-467: Is found in compact, granular aggregates, and can be white, yellow, gray, green, or reddish. Its hardness on the Mohs scale is 5.5 to 6, and its specific gravity 2.60–2.65. It is often translucent with a greasy luster . The low index of refraction and the feeble double refraction in nepheline are nearly the same as in quartz ; but since the sign of the double refraction is negative in nepheline, while it

1258-678: Is limited only by the quality of the furnace’s superstructure material and by the glass composition. Types of furnaces used in container glass making include "end-port" (end-fired), "side-port", and "oxy-fuel". Typically, furnace size is classified by metric tons per day (MTPD) production capability. Modern furnaces use electric heating methods that improve energy efficiency compared to traditional fossil fuel systems, contributing to reduced pollution and emissions. Electrodes made from molybdenum , graphite , or alloys are used in glass furnaces to conduct electricity and generate energy. There are currently two primary methods of making glass containers:

1332-523: Is manufactured into glass products. The batch enters the furnace, then passes to the forming process, internal treatment, and annealing. The following table lists common viscosity fixpoints, applicable to large-scale glass production and experimental glass melting in the laboratory : The batch is fed into the furnace at a slow, controlled rate by the batch processing system. The furnaces are natural gas - or fuel oil -fired, and operate at temperatures up to 1,575 °C (2,867 °F). The temperature

1406-771: Is often found along with leucite , sodalite, potassium feldspars, and sodium-rich plagioclase , amphiboles , or pyroxenes , but almost never in association with quartz . Notable outcrops of nepheline-bearing rocks are found on the Kola Peninsula ; in Norway and South Africa; and at Litchfield, Maine ; Magnet Cove, Arkansas ; and Beemerville, New Jersey , in the United States. Syenites found near Bancroft, Ontario contain large deposits of high-purity nepheline. Elaeolite (a name given by M. H. Klaproth 1809, from Greek words for oil [ἔλαιον] and stone [λίθος]; German : Fettstein )

1480-510: Is one step to initialize industries 2.0 in this branch. Furnaces, compressors, and forming machines generate large quantities of waste heat which are generally cooled by water. Hot glass which is not used in the forming machine is diverted and this diverted glass (called "cullet") is generally cooled by water, and sometimes even processed and crushed in a water bath arrangement. Often cooling requirements are shared over banks of cooling towers arranged to allow for backup during maintenance. After

1554-562: Is perceived as a "premium" quality packaging format. Glass containers are wholly recyclable and the glass industries in many countries have a policy, sometimes required by government regulations, of maintaining a high price on cullet to ensure high return rates. Return rates of 95% are not uncommon in the Nordic countries (Sweden, Norway, Denmark and Finland). Return rates of less than 50% are usual in other countries. Of course glass containers can also be reused , and in developing countries this

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1628-412: Is positive in quartz, the two minerals are readily distinguished under the microscope . An important determinative character of nepheline is the ease with which it is decomposed by hydrochloric acid , with separation of gelatinous silica (which may be readily stained by coloring matters) and cubes of salt . For this reason, a clear crystal of nepheline becomes cloudy when immersed in acid . The mineral

1702-456: Is prone to alteration to zeolites (especially natrolite ), sodalite , kaolin , or compact muscovite . The aluminosilicate backbone of nepheline has a fairly open structure of interlocked six-member rings. This resembles the structure of tridymite , with aluminum substituting for every other silicon atom. This structure produces one nearly hexagonal interstitial site and three irregular interstitial sites per unit cell. In ideal nepheline,

1776-418: Is referred to as a "tear". In the "press and blow" forming, if a plunger and mould are out of alignment, or heated to an incorrect temperature, the glass will stick to either item and become torn. In addition to rejecting faulty containers, inspection equipment gathers statistical information and relays it to the forming machine operators in the hot end. Computer systems collect fault information and trace it to

1850-660: Is the Applied Ceramic Labelling process (ACL). This is screen-printing of the decoration onto the container with a vitreous enamel paint, which is then baked on. An example of this is the original Coca-Cola bottle. Glass containers are packaged in various ways. Popular in Europe are bulk pallets with between 1000 and 4000 containers each. This is carried out by automatic machines (palletisers) which arrange and stack containers separated by layer sheets. Other possibilities include boxes and even hand-sewn sacks. Once packed,

1924-403: Is the mathematical group comprising the symmetry operations that leave at least one point unmoved and that leave the appearance of the crystal structure unchanged. These symmetry operations include Rotation axes (proper and improper), reflection planes, and centers of symmetry are collectively called symmetry elements . There are 32 possible crystal classes. Each one can be classified into one of

1998-420: Is therefore to predict demand both in the short 4- to 12-week term and over the 24- to 48-month-long term. Factories are generally sized to service the requirements of a city; in developed countries there is usually a factory per 1–2 million people. A typical factory will produce 1–3 million containers a day. Despite its positioning as a mature market product, glass does enjoy a high level of consumer acceptance and

2072-456: The float glass process that produces sheet glass, and glassblowing that produces bottles and other containers. It has been done in a variety of ways during the history of glass . Broadly, modern glass container factories are three-part operations: the "batch house", the "hot end", and the "cold end". The batch house handles the raw materials; the hot end handles the manufacture proper—the forehearth, forming machines, and annealing ovens; and

2146-493: The gob cutting shear blades . This oil-laden water mixes with the water outflow stream, thus polluting it. Factories usually have some kind of water processing equipment that removes this emulsified oil to various degrees of effectiveness. Nitrogen oxides are a natural product of the burning of gas in air and are produced in large quantities by gas-fired furnaces. Some factories in cities with particular air pollution problems will mitigate this by using liquid oxygen , however

2220-591: The trigonal crystal system ), orthorhombic , monoclinic and triclinic . Bravais lattices , also referred to as space lattices , describe the geometric arrangement of the lattice points, and therefore the translational symmetry of the crystal. The three dimensions of space afford 14 distinct Bravais lattices describing the translational symmetry. All crystalline materials recognized today, not including quasicrystals , fit in one of these arrangements. The fourteen three-dimensional lattices, classified by lattice system, are shown above. The crystal structure consists of

2294-431: The "blow and blow" method for narrow-neck containers only, and the "press and blow" method used for jars and tapered narrow-neck containers. In both methods, a stream of molten glass at its plastic temperature (1,050–1,200 °C [1,920–2,190 °F]) is cut with a shearing blade to form a solid cylinder of glass, called a "gob". The gob is of predetermined weight just sufficient to make a bottle. Both processes start with

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2368-400: The "blowhead", blows the glass out, expanding into the mould, to make the final container shape. In the press and blow process, the parison is formed by a long metal plunger which rises up and presses the glass out, in order to fill the ring and blank moulds. The process then continues as before, with the parison being transferred to the final-shape mould, and the glass being blown out into

2442-498: The Miller indices ( ℓmn ) and [ ℓmn ] both simply denote normals/directions in Cartesian coordinates . For cubic crystals with lattice constant a , the spacing d between adjacent (ℓmn) lattice planes is (from above): Because of the symmetry of cubic crystals, it is possible to change the place and sign of the integers and have equivalent directions and planes: For face-centered cubic (fcc) and body-centered cubic (bcc) lattices,

2516-466: The air used in the forming process (that is, during the final blow of the container), or through a nozzle directing a stream of the gas into the mouth of the bottle after forming. The treatment renders the container more resistant to alkali extraction, which can cause increases in product pH, and in some cases container degradation. As glass cools, it shrinks and solidifies. Uneven cooling may make glass more susceptible to fracture due to internal stresses:

2590-414: The batch house measures, assembles, mixes, and delivers the glass raw material recipe (batch) via an array of chutes, conveyors, and scales to the furnace. The batch enters the furnace at the "dog house" or "batch charger". Different glass types, colours, desired quality, raw material purity/availability, and furnace design will affect the batch recipe. The hot end of a glassworks is where the molten glass

2664-417: The cell edges, measured from a reference point. It is thus only necessary to report the coordinates of a smallest asymmetric subset of particles, called the crystallographic asymmetric unit. The asymmetric unit may be chosen so that it occupies the smallest physical space, which means that not all particles need to be physically located inside the boundaries given by the lattice parameters. All other particles of

2738-437: The cold end handles the product-inspection and packaging equipment. Batch processing is one of the initial steps of the glass-making process. The batch house simply houses the raw materials in large silos (fed by truck or railcar), and holds anywhere from 1–5 days of material. Some batch systems include material processing such as raw material screening/sieve, drying, or pre-heating (i.e. cullet ). Whether automated or manual,

2812-410: The concept of space groups . All possible symmetric arrangements of particles in three-dimensional space may be described by 230 space groups. The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage , electronic band structure , and optical transparency . Crystal structure is described in terms of the geometry of arrangement of particles in

2886-426: The crystal lattice leaves it unchanged. All crystals have translational symmetry in three directions, but some have other symmetry elements as well. For example, rotating the crystal 180° about a certain axis may result in an atomic configuration that is identical to the original configuration; the crystal has twofold rotational symmetry about this axis. In addition to rotational symmetry, a crystal may have symmetry in

2960-458: The crystallographic planes are geometric planes linking nodes. Some directions and planes have a higher density of nodes. These high density planes have an influence on the behavior of the crystal as follows: Some directions and planes are defined by symmetry of the crystal system. In monoclinic, trigonal, tetragonal, and hexagonal systems there is one unique axis (sometimes called the principal axis ) which has higher rotational symmetry than

3034-413: The details (such as cap sealing surface, screw threads, retaining rib for a tamper-proof cap, etc.) at the open end of the container. Then compressed air is blown through the glass, which results in a hollow and partly formed container. Compressed air is then blown again at the second stage to give final shape. Containers are made in two major stages. The first stage moulds all the details ("finish") around

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3108-402: The fact that they can impart a destructive element to the final glass product. For example, since these materials can withstand large amounts of thermal energy, they can cause the glass product to sustain thermal shock resulting in explosive destruction when heated. Other defects include bubbles in the glass called "blisters" and excessively thin walls. Another defect common in glass manufacturing

3182-424: The following series: This arrangement of atoms in a crystal structure is known as hexagonal close packing (hcp) . If, however, all three planes are staggered relative to each other and it is not until the fourth layer is positioned directly over plane A that the sequence is repeated, then the following sequence arises: This type of structural arrangement is known as cubic close packing (ccp) . The unit cell of

3256-437: The form of mirror planes, and also the so-called compound symmetries, which are a combination of translation and rotation or mirror symmetries. A full classification of a crystal is achieved when all inherent symmetries of the crystal are identified. Lattice systems are a grouping of crystal structures according to the point groups of their lattice. All crystals fall into one of seven lattice systems. They are related to, but not

3330-400: The forming process, some containers—particularly those intended for alcoholic spirits—undergo a treatment to improve the chemical resistance of the inside, called "internal treatment" or dealkalization . This is usually accomplished through the injection of a sulfur- or fluorine-containing gas mixture into bottles at high temperatures. The gas is typically delivered to the container either in

3404-507: The glass slippery, protecting it from scratching and stopping containers from sticking together when they are moved on a conveyor . The resultant invisible combined coating gives a virtually unscratchable surface to the glass. Due to reduction of in-service surface damage, the coatings often are described as strengtheners, however a more correct definition might be strength-retaining coatings. Glass containers are 100% inspected; automatic machines, or sometimes persons, inspect every container for

3478-417: The gob falling, by gravity, and guided, through troughs and chutes, into the blank moulds, two halves of which are clamped shut and then sealed by the "baffle" from above. In the "blow and blow" process, the glass is first blown through a valve in the baffle, forcing it down into the three-piece "ring mould" which is held in the "neckring arm" below the blanks, to form the "finish". The term "finish" describes

3552-401: The gobs simultaneously, and they fall into the blank moulds in parallel. Forming machines are largely powered by compressed air and a typical glass works will have several large compressors (totaling 30k–60k cfm) to provide the necessary compressed air. However in recent times servo drives have been implemented in the machines which achieve a better digital control of the forming process. It

3626-519: The hexagonal sites are occupied by potassium ions and the irregular sites by smaller sodium ions, yielding an atomic ratio of sodium to potassium of 3:1. This corresponds to an ideal weight percentage of K 2 O of 8.1% The range of compositions seen in natural nepheline is 3% to 12% K 2 O. Small amounts of calcium may be present as well. At elevated temperature, nepheline forms a complete solid solution series with kalsilite , KAlSiO 4 . At temperatures below about 1,000 °C (1,830 °F), there

3700-430: The logic of this given the cost in carbon of (1) not using regenerators and (2) having to liquefy and transport oxygen is highly questionable. Sulfur oxides are produced as a result of the glass melting process. Manipulating the batch formula can effect some limited mitigation of this; alternatively exhaust plume scrubbing can be used. The raw materials for glass-making are all dusty material and are delivered either as

3774-412: The manufacturing process: spray on a polyethylene coating for abrasion resistance and increased lubricity, inspect the containers for defects, label the containers, and package the containers for shipment. Glass containers typically receive two surface coatings, one at the hot end , just before annealing and one at the cold end just after annealing. At the hot end a very thin layer of tin(IV) oxide

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3848-446: The mould that produced the container. This is done by reading the mould number on the container, which is encoded (as a numeral, or a binary code of dots) on the container by the mould that made it. Operators carry out a range of checks manually on samples of containers, usually visual and dimensional checks. Sometimes container factories will offer services such as "labelling". Several labelling technologies are available. Unique to glass

3922-404: The mould. The container is then picked up from the mould by the "take-out" mechanism, and held over the "deadplate", where air cooling helps cool down the still-soft glass. Finally, the bottles are swept onto a conveyor by the "push out paddles" that have air pockets to keep the bottles standing after landing on the "deadplate"; they're now ready for annealing. The forming machines hold and move

3996-405: The new "stock units" are labelled, warehoused, and ultimately shipped. Glass container manufacture in the developed world is a mature market business. World demand for flat glass was approximately 52 million tonnes in 2009. The United States, Europe and China account for 75% of demand, with China's consumption having increased from 20% in the early 1990s to 50%. Glass container manufacture is also

4070-499: The oil industry. It can be used as a filler in paints, plastics, foam rubber, and sorbent. Nepheline of Kiya Shaltyr deposit (Kemerovo Region, Russia) is also used as a raw material for aluminium manufacturing. Basal plane In crystallography , crystal structure is a description of ordered arrangement of atoms , ions , or molecules in a crystalline material . Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat along

4144-416: The opening, but the body of the container is initially made much smaller than its final size. These partly manufactured containers are called "parisons", and quite quickly, they are blow-molded into final shape. The "rings" are sealed from below by a short plunger. After the "settleblow" finishes, the plunger retracts slightly, to allow the skin that's formed to soften. "Counterblow" air then comes up through

4218-423: The other two axes. The basal plane is the plane perpendicular to the principal axis in these crystal systems. For triclinic, orthorhombic, and cubic crystal systems the axis designation is arbitrary and there is no principal axis. For the special case of simple cubic crystals, the lattice vectors are orthogonal and of equal length (usually denoted a ); similarly for the reciprocal lattice. So, in this common case,

4292-410: The parts that form the container. The machine consists of 19 basic mechanisms in operation to form a bottle and generally powered by compressed air (high pressure – 3.2 bar and low pressure – 2.8 bar), the mechanisms are electronically timed to coordinate all movements of the mechanisms. The most widely used forming machine arrangement is the individual section machine (or IS machine). This machine has

4366-543: The past. This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass. Most float glass is soda–lime glass , but relatively minor quantities of special borosilicate and flat panel display glass are also produced using the float glass process. The float glass process is also known as the Pilkington process , named after the British glass manufacturer Pilkington , who pioneered

4440-415: The plunger, to create the parison. The baffle rises and the blanks open. The parison is inverted in an arc to the "mould side" by the "neckring arm", which holds the parison by the "finish". As the neckring arm reaches the end of its arc, two mould halves close around the parison. The neckring arm opens slightly to release its grip on the "finish", then reverts to the blank side. "Final blow", applied through

4514-411: The primitive lattice vectors are not orthogonal. However, in these cases the Miller indices are conventionally defined relative to the lattice vectors of the cubic supercell and hence are again simply the Cartesian directions . The spacing d between adjacent ( hkℓ ) lattice planes is given by: The defining property of a crystal is its inherent symmetry. Performing certain symmetry operations on

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4588-621: The principal directions of three-dimensional space in matter. The smallest group of particles in material that constitutes this repeating pattern is unit cell of the structure. The unit cell completely reflects symmetry and structure of the entire crystal, which is built up by repetitive translation of unit cell along its principal axes. The translation vectors define the nodes of Bravais lattice . The lengths of principal axes/edges, of unit cell and angles between them are lattice constants , also called lattice parameters or cell parameters . The symmetry properties of crystal are described by

4662-467: The risk and consequential product liability of using a component (the reused container) of unknown and unqualified safety. How glass containers compare to other packaging types ( plastic , cardboard , aluminium ) is hard to say; conclusive lifecycle studies are yet to be produced. Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin , although lead and various low melting point alloys were used in

4736-482: The same as the seven crystal systems . aP mP mS oP oS oI oF tP tI hR hP cP cI cF The most symmetric, the cubic or isometric system, has the symmetry of a cube , that is, it exhibits four threefold rotational axes oriented at 109.5° (the tetrahedral angle ) with respect to each other. These threefold axes lie along the body diagonals of the cube. The other six lattice systems, are hexagonal , tetragonal , rhombohedral (often confused with

4810-520: The same group of atoms, the basis , positioned around each and every lattice point. This group of atoms therefore repeats indefinitely in three dimensions according to the arrangement of one of the Bravais lattices. The characteristic rotation and mirror symmetries of the unit cell is described by its crystallographic point group . A crystal system is a set of point groups in which the point groups themselves and their corresponding space groups are assigned to

4884-411: The same off the site again as finished product. Water is used to cool the furnace, compressor and unused molten glass. Water use in factories varies widely; it can be as little as one tonne water used per melted tonne of glass. Of the one tonne, roughly half is evaporated to provide cooling, the rest forms a wastewater stream. Most factories use water containing an emulsified oil to cool and lubricate

4958-401: The seven crystal systems. In addition to the operations of the point group, the space group of the crystal structure contains translational symmetry operations. These include: There are 230 distinct space groups. By considering the arrangement of atoms relative to each other, their coordination numbers, interatomic distances, types of bonding, etc., it is possible to form a general view of

5032-626: The structure. The APFs and CNs of the most common crystal structures are shown below: The 74% packing efficiency of the FCC and HCP is the maximum density possible in unit cells constructed of spheres of only one size. Interstitial sites refer to the empty spaces in between the atoms in the crystal lattice. These spaces can be filled by oppositely charged ions to form multi-element structures. They can also be filled by impurity atoms or self-interstitials to form interstitial defects . Glass manufacturing Glass production involves two main methods –

5106-447: The structures and alternative ways of visualizing them. The principles involved can be understood by considering the most efficient way of packing together equal-sized spheres and stacking close-packed atomic planes in three dimensions. For example, if plane A lies beneath plane B, there are two possible ways of placing an additional atom on top of layer B. If an additional layer were placed directly over plane A, this would give rise to

5180-409: The surface cools first, then as the interior cools and contracts it creates tension. Even cooling is achieved by annealing . An annealing oven (known in the industry as a lehr ) heats the container to about 580 °C (1,076 °F), then cools it, depending on the glass thickness, over a 20 – 60 minute period. The role of the cold end of glass container production is to complete the final tasks in

5254-401: The syntax ( hkℓ ) denotes a plane that intercepts the three points a 1 / h , a 2 / k , and a 3 / ℓ , or some multiple thereof. That is, the Miller indices are proportional to the inverses of the intercepts of the plane with the unit cell (in the basis of the lattice vectors). If one or more of the indices is zero, it means that the planes do not intersect that axis (i.e., the intercept

5328-506: The technique (invented by Sir Alastair Pilkington ) in the 1950s. As with all highly concentrated industries, glassworks suffer from moderately high local environmental impacts. Compounding this is that because they are mature market businesses, they often have been located on the same site for a long time and this has resulted in residential encroachment. The main impacts on residential housing and cities are noise, fresh water use, water pollution, NOx and SOx air pollution, and dust. Noise

5402-420: The unit cell are generated by the symmetry operations that characterize the symmetry of the unit cell. The collection of symmetry operations of the unit cell is expressed formally as the space group of the crystal structure. Vectors and planes in a crystal lattice are described by the three-value Miller index notation. This syntax uses the indices h , k , and ℓ as directional parameters. By definition,

5476-445: The unit cells. The unit cell is defined as the smallest repeating unit having the full symmetry of the crystal structure. The geometry of the unit cell is defined as a parallelepiped , providing six lattice parameters taken as the lengths of the cell edges ( a , b , c ) and the angles between them (α, β, γ). The positions of particles inside the unit cell are described by the fractional coordinates ( x i , y i , z i ) along

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