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Bioabsorbable Metallic Glass
Bioresorbable (or bioabsorbable) metallic glass is a type of amorphous metal, which is based on the ''Mg-Zn-Ca ternary system''. Containing only elements which already exist inside the human body, namely Mg, Zn and Ca, these amorphous alloys are a special type of biodegradable metal. History The first reported metallic glass was an alloy (Au75Si25) produced at Caltech by W. Klement (Jr.), Willens and Duwez in 1960. This and other early glass-forming alloys had to be cooled extremely rapidly (in the order of one mega-kelvin per second, 106 K/s) to avoid crystallization. An important consequence of this was that metallic glasses could only be produced in a limited number of forms (typically ribbons, foils, or wires) in which one or more dimensions were small so that heat could be extracted quickly enough to achieve the necessary cooling rates. As a result, metallic glass specimens (with a few exceptions) were limited to thicknesses of less than one hundred micrometers. Mg- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amorphous Metal
An amorphous metal (also known as metallic glass, glassy metal, or shiny metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity and can show metallic luster. There are several ways in which amorphous metals can be produced, including extremely rapid cooling, physical vapor deposition, solid-state reaction, ion irradiation, and mechanical alloying. Previously, small batches of amorphous metals had been produced through a variety of quick-cooling methods, such as amorphous metal ribbons which had been produced by sputtering molten metal onto a spinning metal disk (melt spinning). The rapid cooling (in the order of mill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ductility
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stress before failure. Ductility is an important consideration in engineering and manufacturing. It defines a material's suitability for certain manufacturing operations (such as cold working) and its capacity to absorb mechanical overload.. Some metals that are generally described as ductile include gold and copper. However, not all metals experience ductile failure as some can be characterized with brittle failure like cast iron. Polymers generally can be viewed as ductile materials as they typically allow for plastic deformation. Malleability, a similar mechanical property, is characterized by a material's ability to deform plastically without failure under compressive stress. Historically, materials were considered malleable if they were am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioresorbable Stent
In medicine, a stent is any device which is inserted into a blood vessel or other internal duct to expand it to prevent or alleviate a blockage. Traditionally, such devices are fabricated from metal mesh and remain in the body permanently or until removed through further surgical intervention. A bioresorbable stent (also called bioresorbable scaffold, biodegradable stent or naturally-dissolving stent) serves the same purpose, but is manufactured from a material that may dissolve or be absorbed in the body. Background The use of metal drug-eluting stents presents some potential drawbacks. These include a predisposition to late stent thrombosis, prevention of late vessel adaptive or expansive remodeling, hindrance of surgical revascularization, and impairment of imaging with multislice CT. To overcome some of these potential drawbacks, several companies are pursuing the development of bioresorbable scaffolds or bioabsorbable stents. Like metal stents, placement of a bioresorbable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthopaedic
Orthopedic surgery or orthopedics ( alternatively spelt orthopaedics), is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal trauma, spine diseases, sports injuries, degenerative diseases, infections, tumors, and congenital disorders. Etymology Nicholas Andry coined the word in French as ', derived from the Ancient Greek words ὀρθός ''orthos'' ("correct", "straight") and παιδίον ''paidion'' ("child"), and published ''Orthopedie'' (translated as ''Orthopædia: Or the Art of Correcting and Preventing Deformities in Children'') in 1741. The word was assimilated into English as ''orthopædics''; the ligature ''æ'' was common in that era for ''ae'' in Greek- and Latin-based words. As the name implies, the discipline was initially developed with attention to children, but the correction of spinal and bone deformities in all stages of life eventually ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallic Glass
An amorphous metal (also known as metallic glass, glassy metal, or shiny metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity and can show metallic luster. There are several ways in which amorphous metals can be produced, including extremely rapid cooling, physical vapor deposition, solid-state reaction, ion irradiation, and mechanical alloying. Previously, small batches of amorphous metals had been produced through a variety of quick-cooling methods, such as amorphous metal ribbons which had been produced by sputtering molten metal onto a spinning metal disk (melt spinning). The rapid cooling (in the order of mill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hardness
In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, hardness can be measured in different ways, such as scratch hardness, indentation hardness, and rebound hardness. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter. Measuring hardness There are three main types of hardness measurements: ''scratch' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elastic Modulus
An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is defined as the slope of its stress–strain curve in the elastic deformation region: A stiffer material will have a higher elastic modulus. An elastic modulus has the form: :\delta \ \stackrel\ \frac where stress is the force causing the deformation divided by the area to which the force is applied and strain is the ratio of the change in some parameter caused by the deformation to the original value of the parameter. Since strain is a dimensionless quantity, the units of \delta will be the same as the units of stress. Specifying how stress and strain are to be measured, including directions, allows for many types of elastic moduli to be defined. The three primary ones are: # ''Young's modulus'' (E) describes tensile and compressive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corrosion Resistance
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion. In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen, hydrogen or hydroxide. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the original metal and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases. Many structural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bone Tissue
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have complex internal and external structures. They are lightweight yet strong and hard and serve multiple functions. Bone tissue (osseous tissue), which is also called bone in the uncountable sense of that word, is hard tissue, a type of specialized connective tissue. It has a honeycomb-like matrix internally, which helps to give the bone rigidity. Bone tissue is made up of different types of bone cells. Osteoblasts and osteocytes are involved in the formation and mineralization of bone; osteoclasts are involved in the resorption of bone tissue. Modified (flattened) osteoblasts become the lining cells that form a protective layer on the bone surface. The mineralized ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Millimetre
330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter. The millimetre (American and British English spelling differences#-re, -er, international spelling; International System of Units, SI unit symbol mm) or millimeter (American and British English spelling differences#-re, -er, American spelling) is a Units of measurement, unit of length in the International System of Units (SI), equal to one thousandth of a metre, which is the SI base unit of length. Therefore, there are one thousand millimetres in a metre. There are ten millimetres in a centimetre. One millimetre is equal to micrometres or nanometres. Since an inch is officially defined as exactly 25.4 millimetres, a millimetre is equal to exactly (≈ 0.03937) of an inch. Definition Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances by any chemical reaction. The number of protons in the nucleus is the defining property of an element, and is referred to as its atomic number (represented by the symbol ''Z'') – all atoms with the same atomic number are atoms of the same element. Almost all of the baryonic matter of the universe is composed of chemical elements (among rare exceptions are neutron stars). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds. Only a minority of elements, such as silver and gold, are found uncombined as relatively pure native element minerals. Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is primarily a mixture o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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