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What is Stainless Steel? What is Sterling Silver? What is Surgical Steel? What is Nickel Free? What is Pearl? What is Rhodium? What is Cubic Zirconia? What is Fresh Water Pearl? What is Leather? Soure from Wikipedia, the free encyclopedia. What is Stainless Steel?
In metallurgy, stainless steel is defined as an iron-carbon alloy with a minimum of 11.5 wt% chromium content.[1] Stainless steel does not stain, corrode or rust as easily as ordinary steel (it "stains less"), but it is not stain-proof. It is also called corrosion resistant steel when the alloy type and grade are not detailed, particularly in the aviation industry. There are different grades and surface finishes of stainless steel to suit the environment to which the material will be subjected in its lifetime. Common uses of stainless steel are cutlery and watch straps.
High oxidation-resistance in air at ambient temperature are normally achieved with additions of a minimum of 13% (by weight) chromium, and up to 26% is used for harsh environments.[2] The chromium forms a passivation layer of chromium(III) oxide (Cr2O3) when exposed to oxygen. The layer is too thin to be visible, which means that the metal remains lustrous. It is, however, impervious to water and air, protecting the metal beneath.
Also, this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, such as aluminium and titanium. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off causing the parts to weld together. When disassembled, the welded material may be torn and pitted, an effect that is known as galling. This destructive galling can be best avoided by the use of dissimilar materials, e.g. bronze to stainless steel, or even different types of stainless steels (martensitic against austenitic, etc.), when metal-to-metal wear is a concern. In addition, Nitronic alloys (trademark of Armco, Inc.) reduce the tendency to gall through selective alloying with manganese and nitrogen.
What is Sterling Silver?
The sterling silver standard has a minimum millesimal fineness of 925. Sterling is an alloy of silver containing 92.5 % pure silver and 7.5 per cent other metals, usually copper.
Fine silver (99.9% pure) is generally too soft for producing large functional objects, therefore the silver is usually alloyed with copper to give it strength, while at the same time preserving the ductility and beauty of the precious metal. Other metals can replace the copper, usually with the intent to improve various properties of the basic sterling alloy such as reducing casting porosity, eliminating firescale, and increasing resistance to tarnish. These replacement metals include germanium, zinc and platinum, as well as a variety of other additives, including silicon and boron. A number of alloys have appeared in recent years, formulated to lessen firescale or to inhibit tarnish, and this has sparked heavy competition among the various manufacturers, who are rushing to make claims of having the best formulation. However, no one alloy has emerged to replace copper as the industry standard, and alloy development is a very active area.
What is Surgical Steel?
Surgical stainless steel is an alloy of iron, carbon, chromium (12–20%), molybdenum (0.2–3%), and nickel (8–12%).
The chromium gives the metal its scratch-resistance and corrosion resistance. The nickel provides a smooth and polished finish. The molybdenum gives greater hardness, and helps maintaining a cutting edge.
Although there are myriad variations in the recipes, there are two main varieties of stainless steel; martensitic and austenitic, see the stainless steel article.
The word 'surgical' refers to the fact that these types of steel are well-suited for making surgical instruments: they are easy to clean and sterilize, strong and corrosion-resistant. The nickel/chrome/molybdenum alloys are also used for orthopaedic implants as aids in bone repair, as a structural part of artificial heart valves, and other implants. Immune system reaction to nickel is a potential complication. In some cases today titanium is used instead in procedures that require a metal implant which will be permanent. Titanium is a reactive metal, the surface of which quickly oxidizes on exposure to air, creating a microstructured stable oxide surface. This provides a surface into which bone can grow and adhere in orthopaedic implants but which is incorrodible after implant. Thus steel may be used for temporary implants and the more expensive titanium for permanent ones.[citation needed]
Most surgical equipment is made out of martensitic steel—it is much harder than austenitic steel, and easier to keep sharp. Depending on the type of equipment, the alloy recipe is varied slightly to get more sharpness, or strength. Implants and equipment that are put under pressure (bone fixation screws, prostheses, body piercing jewelry), are made out of austenitic steel, often 316L and 316LVM, because it is less brittle.
What is Nickel?
Nickel is a silvery white metal that takes on a high polish. It belongs to the transition metals, and is hard and ductile. It occurs most usually in combination with sulfur and iron in pentlandite, with sulfur in millerite, with arsenic in the mineral nickeline, and with arsenic and sulfur in nickel glance.
Similar to the massive forms of chromium, aluminium and titanium, nickel is a very reactive element, but is slow to react in air at normal temperatures and pressures. Due to its permanence in air and its inertness to oxidation, it is used in coins, for plating iron, brass, etc., for chemical apparatus, and in certain alloys, such as German silver.
Nickel is magnetic, and is very frequently accompanied by cobalt, both being found in meteoric iron. It is chiefly valuable for the alloys it forms, especially many superalloys, and particularly stainless steel. Nickel is also a naturally magnetostrictive material, meaning that in the presence of a magnetic field, the material undergoes a small change in length.[4] In the case of Nickel, this change in length is negative (contraction of the material), which is known as negative magnetostriction.
The most common oxidation state of nickel is +2, though 0, +1, +3 and +4 Ni complexes are observed. It is also thought that a +6 oxidation state may exist, however, results are inconclusive.
The unit cell of nickel is a face centered cube with a lattice parameter of 0.356 nm giving a radius of the atom of 0.126 nm.
Nickel-62 is the most stable nuclide of all the existing elements; it is more stable even than Iron-56
What is Pearl?
A pearl is a hard, rounded object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of mollusks, a pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of pearls occur, see baroque pearl.
The finest quality pearls have been highly valued as gemstones and objects of beauty for many centuries, and the word pearl has become a metaphor for something rare, fine, and admirable.
Almost any shelled mollusk can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within the mollusk's mantle folds, but virtually none of these "pearls" are considered to be gemstones.
True iridescent pearls, the most desirable pearls, are produced by two groups of molluscan bivalves or clams. One family lives in the sea: the pearl oysters. The other, very different group of bivalves live in freshwater, and these are the river mussels, for example, see the freshwater pearl mussel.
Saltwater pearls can grow in several species of marine pearl oysters in the family Pteriidae. Freshwater pearls grow within certain (but by no means all) species of freshwater mussels in the order Unionida, the families Unionidae and Margaritiferidae. All of these bivalves are able to make true pearls because they have a thick inner shell layer composed of "mother of pearl" or nacre. The mantle of the living bivalve can create a pearl in the same way that it creates the pearly inner layer of the shell.
Fine gem quality saltwater and freshwater pearls can and do sometimes occur completely naturally, but this is a rare occurrence. Many hundreds of pearl oysters or pearl mussels have to be gathered and opened (killed) in order to find even one pearl, and for many centuries that was the only way pearls were obtained. This was the main reason why pearls fetched such extraordinary prices in the past. In modern times however, almost all the pearls for sale were formed with a good deal of expert intervention from human pearl farmers.
A true pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell. A "natural pearl" is one that formed without any human intervention at all, in the wild, and these are very rare. A "cultured pearl" on the other hand, is one that has been formed on a pearl farm. The great majority of pearls on the market are cultured pearls.
Imitation or fake pearls are also widely sold in inexpensive jewelry, but the quality of the iridescence is usually very poor, and generally speaking, fake pearls are usually quite easy to distinguish from the real thing.
Pearls have been harvested, or more recently cultivated, primarily for use in jewelry, but in the past they were also stitched onto lavish clothing, as worn, for example, by royalty. Pearls have also been crushed and used in cosmetics, medicines, or in paint formulations.
Pearl is considered to be the birthstone for June.
What is Rhodium?
Rhodium is a hard silvery white and durable metal that has a high reflectance. Rhodium metal does not normally form an oxide, even when heated. Oxygen is absorbed from the atmosphere at the melting point of rhodium, but on solidification the oxygen is released.[3] Rhodium has both a higher melting point and lower density than platinum. It is not attacked by acids: it is completely insoluble in nitric acid and dissolves slightly in aqua regia. A complete dissolution of rhodium in powder form is only obtained in sulfuric acid.
What is Cubic Zirconia?
Cubic zirconia (or CZ), the cubic crystalline form of zirconium dioxide (ZrO2), is a mineral that is widely synthesized for use as a diamond simulant. The synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirconium silicate (ZrSiO4). Cubic zirconia is extremely rare in nature.
Because of its low cost, durability, and close visual likeness to diamond, synthetic cubic zirconia has remained the most gemologically and economically important diamond simulant since 1976. Its main competition as a synthetic gemstone is the more recently cultivated material, synthetic moissanite.
What is Fresh Water Pearl?
Freshwater pearls are a kind of pearl that comes from freshwater mussels. They are produced in Japan and the United States on a limited scale, but are now almost exclusive to China The U.S. Federal Trade Commission requires that freshwater pearls are referred to as "freshwater cultured pearls" in commerce.
What is Leather?
Leather is a material created through the tanning of hides and skins of animals, primarily cattlehide. The tanning process converts the putrescible skin into a durable, long-lasting and versatile natural material for various uses.
Leather is an important material with many uses. Together with wood, leather formed the basis of much ancient technology. The leather industry and the fur industry are distinct industries that are differentiated by the importance of their raw materials. In the leather industry the raw materials are by-products of the meat industry, with the meat having higher value than the skin. The fur industry uses raw materials that are higher in value than the meat and hence the meat is classified as a by-product. Taxidermy also makes use of the skin of animals, but generally the head and part of the back are used. Hides and skins are also used in the manufacture of glue and gelatin.
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