Advanced Materials

Advanced Materials Definition In materials science are called composite materials that are formed by the joining of two materials to achieve the combination of properties can not be obtained in the original materials. These compounds can be selected to achieve unusual combinations of stiffness, strength, weight, high temperature performance, corrosion resistance, conductivity or hardness. When the materials are composites with the following characteristics: • are formed of two or more components physically distinct and mechanically separable. • Feature several chemically distinct phases, completely insoluble each other and separated by an interface. • Its mechanical properties are superior to the simple sum of the properties of its components (synergy). • not belong to composite materials, these multiphase materials, such as metal alloys, in which a heat treatment by the composition of the present phases are changed. These materials arise from the need to obtain materials that combine the properties of ceramics, plastics and metals. For example in the transportation industry are necessary light, stiff, impact-resistant materials that resist corrosion and good wear properties they rarely give juntas.A despite having obtained materials with exceptional properties, practical applications are reduced by factors that greatly increase their cost, and the difficulty of production or incompatibility between materiales.La vast majority of composite materials are artificially created but some, such as wood and bone, appear in nature. Structure Although there are a variety of composite materials, in all one can distinguish the following parts: • Reinforcing agent: a discrete phase character and geometry is essential in defining the mechanical properties of the material • Phase array or simply die. : a continuing character and is responsible for the physical and chemical properties. Transmits efforts to reinforcing agent. It also protects and gives cohesion to the material. BIOMATERIALS Biomaterials can be defined as common biological materials such as leather, wood, or any item that replaces the function of living tissues or organs. In other words, a biomaterial is a pharmacologically inert substance designed to be implanted or incorporated within the living system. Biomaterials are implanted in order to replace and / or restore living tissues and their functions, which means they are exposed to temporary or permanent body fluids so, but in reality may be located outside of the body, including in this category to most dental materials which have traditionally been treated separately. Because biomaterials restore functions of living tissues and organs in the body, it is essential to understand the relationships between the properties, functions and structures of biological materials, which are studied under three aspects: biological materials, implant materials and the interaction between them within the body. Devices such as artificial limbs, amplifiers external ear and facial prostheses are not considered implants. Biomaterials, natural or synthetic substances whose mission is to replace a part or a function of our body, physiologically safe and acceptable form, can be classified in different ways: according to their chemical composition, biometales, biopolymers, bioceramics, biocomposites and semiconductors; according to their origin, natural and synthetic. Another more practical way to classify are implantable devices which are implanted time in the human body to replace a function, and the non-implantable, including probes and catheters and tubes, among others. PROPERTIES REQUIRED IN BIOMATERIALS The required characteristics for the human body to make an artificial joint in the properties required of materials used in prostheses are very restrictive. Therefore, biocompatible materials are required, ie, materials that produce a minimum degree of rejection in the human body. Body fluids are highly corrosive, and metal alloys must be resistant to corrosion. Another aspect to consider is the mechanical properties, which are important in the selection of materials for prostheses, because the musculoskeletal system, along with the movement promotes considerable strength to the prosthesis. Because the surfaces of the joint are in contact, and have relative motion between them, the prosthesis is subject to wear. One consequence of the wear surfaces of the implants is the generation of particulate debris. The accumulation of these particles in the surrounding tissues of the joint can cause swelling and pain. In addition to dealing with the conditions mentioned above, another aspect to be considered in the selection of materials for surgical implants is that its components are lightweight, inexpensive, and their properties, stable over time. Ideally, an implanted prosthesis must operate satisfactorily over the lifetime of the patient, so that replacement is not necessary. However, in the current designs, the life of the prosthesis varies between 10 and 15 years in the case of total hip replacement, so there is great interest in the scientific community to develop prosthetic durability for increased longevity currently enjoyed by the population. METAL BIOMATERIALS In the 1920s, Reiner Erdle and Charles Orange, who combined their knowledge of dentistry and metallurgy respectively doctor, developed the Vitallium alloy, which was the first metallic biomaterial alloy with mechanical properties of biocompatibility and corrosion resistance, acceptable for applications in surgical prostheses. This cobalt (Co 65 percent, 30 percent Cr, and 5 percent of Mo), was the starting point for a number of multidisciplinary research in developing new orthopedic applications, such as nails, screws and fasteners fractured, and several types of joint replacement implants such as hip, knee, shoulder, elbow, among other bones. Later, in the 1930s the 316LQ surgical stainless steel, a steel with low carbon, 18 percent chromium, 8 percent nickel develops, and 2 percent molybdenum. Other alloys which have become very important in aviation and aerospace applications, and in medical applications for surgical implants are titanium base, especially the Ti6Al4V alloy which has superior advantages in weight, mechanical properties and corrosion resistance regarding cobalt base alloys and stainless steel. However, it has low wear resistance, and high cost. This alloy has been modified by exchanging the Vanadium Niobium, which has left a noticeable improvement in the index of biocompatibility. Moreover, in order to increase wear resistance, it has implemented the use of hard coatings on femoral heads, applied by techniques of physical deposition in vapor phase (PVD), also using ceramic materials such as alumina (Al2O3) or zirconia (ZrO2). Polymeric biomaterials A variety of biocompatible polymers: natural polymers such as cellulose, glucosamine, etc., and synthetic polymers, such as polyethylene, ultra high molecular weight polyethylene (UHMWPE), PVC, nylon, silicone, etc.. The development of biopolymers applications include facial prosthetics, hearing aid parts, dental appliances, pacemakers, kidney, liver and lungs. Thin films and layers of PVC are used in storage bags and packaging surgical blood and other solutions; parties esophageal segments of arteries, biodegradable sutures, parts of joint implants in fingers, knee and hip acetabulum, among others. Ceramic biomaterials The bioceramics are complex chemical compounds containing metallic and nonmetallic elements. Due to their ionic or covalent bonds, are generally hard and brittle. Besides having a high melting point and low thermal and electrical conductivity, the ceramic wear resistant considered. Main bioceramics are alumina, zirconia, Hydroxyapatite, porcelain, bioactive glasses, and so on. Its main applications are in the skeletal system, with all kinds of coatings on implants and joint replacements, also used in dental applications, artificial valves, spine surgery and cranial repairs. SOME APPLICATIONS BIOMATERIALS The total hip The solution for this type of fracture, and diseases such as arthritis, among others, can be a total hip view in subsection b). This joint consists of an acetabular cup (UHMWPE, Co-Cr, Al2O3, ZrO2), which is fixed to the pelvis, and serves as a seat for a sphere whose rod (Co-Cr, 316LQ, Ti6Al4V) is embedded in the femur . The two artificial elements restore the articular patella type with which the patient can walk back system. Knee implant Knee replacement is one of the most significant advances in orthopedic surgery, and was first held in 1968. Heart Valves The heart is a vital part of the human anatomy, since it is a recirculation pump blood through the body. Heart valves allow to pump blood efficiently. These valves are prone to failure due to diseases, but can be replaced by artificial prosthetic valves. Mechanical valves are excellent in terms of durability, but are hampered by their tendency to clot blood. Biological valves are less durable and must be replaced periodically. Dental Implants The emergence of dental implants has influenced major changes in clinical dentistry in the second half of the twentieth century. Through specific surgical techniques, it is possible to replace missing teeth, other synthetic, with the same functions and long life. The prosthesis consists of three main parts, called corona, core or post, which will support the crown and the implant itself I replace the tooth root. Spine The first surgical procedure for thoracic herniated disc was reported by Middleton and Teacher in 1911.Desde the 1930s to the present, the metal is used in prosthetic surgery. In 1966 the first prosthetic surgery was done, replacing a cervical disc. NANOMATERIALS Nanomaterials are materials with smaller than one micron in at least one dimension morphological properties. Despite the fact that there is no consensus on the minimum or maximum size of a nanomaterial, some authors restrict their size from 1 to 100 nm, a logical definition would place the nanoscale from microscale (1 micron) and atomic / molecular scale ( about 0.2 nanometers). The new properties of nanomaterials is the subject of nanomechanics research. Their catalytic activities reveal novel properties in interaction with biomaterials. The materials reduced to the nanoscale can suddenly show very different properties to those exhibited in a macroscale, enabling unique applications. For example, opaque substances become transparent (copper), inert materials are transformed into catalysts (platinum) become stable combustible materials (aluminum), solids become liquid at room temperature (gold) become conductive insulators (silicone) . Materials such as gold, which is chemically inert at normal scales, can serve as catalysts at the nanoscale. Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale. Nanomaterials can be subdivided into nanoparticles, nanolayers and nanocomposites. The focus of nanomaterials is a bottom-up approach to structures and functional effects so that the building blocks of materials are designed and assembled in a controlled manner. A recent report by Small Times predicts strong growth of nanomaterials called. In the same different types existing today (such as nanoclays to reinforce plastic) or carbon nanotubes are discussed to add conductivity to various materials. Many of these advances are pursuing the small and medium companies in collaboration with leading American companies. There are three basic categories of nanomaterials from the commercial point of view and development: metal oxides, nanoclays and carbon nanotubes. Those who have more advanced from a commercial point of view are metal oxide nanoparticles. 4.2 PROCESSING OF PARTICLE REINFORCED COMPOSITES (MCP) AND FIBRE (MCF) CONVENTIONAL METHODS FOR COMBINATION OF MATERIALS-oxidic oxidic oxidic AND OXIDES-NO • CERAMIC MATRIX COMPOSITES • POLYMER MATRIX COMPOSITES • METAL MATRIX COMPOSITE Composites reinforced with particles. Particles are composed of a hard material uniformly dispersed discrete fragile, are surrounded by a soft and ductile matrix Types: Compounds Compounds dispersion hardened with such particles itself. The dispersion-strengthened composite particle size is very small (diameter between 100 and 2,500 μ). At normal temperatures, these compounds are more resistant alloys, but its resistance decreases inversely with temperature. Its thermal creep resistance is greater than that of metals and alloys. Its main properties are: • The phase is usually a hard, stable oxide • The agent must have excellent physical properties • No agent should react chemically and phase • Must successfully joining materials.... Fiber-reinforced composite materials. One component is often a reinforcing agent as a strong fiber: fiberglass, quartz, Kevlar, Dyneema or carbon fiber that gives the material its tensile strength, while another component (called matrix) which is usually a resin such as epoxy or polyester fibers league wraps and transferring the burden of broken to intact and among which are not aligned with the lines of tension fibers. Also, unless the matrix chosen is especially flexible and prevents buckling of the compression fiber. Some compounds used an aggregate in place of, or in addition to the fibers. In terms of strength, the fibers (responsible for the mechanical properties) are used to resist tensile matrix (responsible for the physical and chemical properties) to resist deformation, and all materials used to resist compression, including any added . Bumping or cyclic stresses can cause the fibers to separate from the matrix, which is called delamination. Structural composites. They are made so simple materials like composites and their properties depend critically on the geometry and design. The most abundant are called laminar and sandwich panels. The webs are formed by panels joined together by any adhesive or other bonding. The most usual is that each blade is reinforced with fibers and has a more resistant to efforts preferred direction. In this way we obtain an isotropic material, joining several markedly anisotropic layers. This applies, for example, plywood, in which the directions of maximum resistance together form right angles. Sandwich panels consisting of two outer sheets of high strength and toughness, (typically reinforced plastics, aluminum or even titanium), separated by a less dense and less durable material (foaming polymers, synthetic rubbers, balsa wood or inorganic cements). These materials are frequently used in construction, in the aircraft industry and in the manufacture of multilayer capacitors. • Examples of composite fiber reinforced plastics: ◦ Classifieds by fiber type: ■ Wood (cellulose fibers in a matrix of lignin and hemicellulose) ■ Carbon fiber reinforced plastic or CFRP or ■ Glass Reinforced Plastic (GRP, GFRP or informally "fiberglass") ◦ Classified by the matrix:... ■ Thermoplastics Thermoplastics reinforced with long fiber glass fabrics ■ ■ • Compounds thermoformed or thermoset compounds or metal matrix MMCs: ◦ Cermet (ceramic and metal ). ◦ White Foundry. ■ Hard metal (carbide metal matrix) ◦ metal-Intermetal Laminate • Ceramic Matrix Composites. ◦ Concrete / Concrete ◦ Carbon-reinforced carbon (carbon fiber graphite matrix) ◦ bone (bone matrix reinforced with collagen fibers. ) ◦ Adobe (mud and straw) • Organic Compounds ceramic / matrix added Mother of pearl or nacre ◦ ◦ • Wood Asphalt concrete improved ◦ ◦ Plywood, oriented strand boards (OSB). ◦ ◦ WeatherBest Trex (recycled wood fiber in polyethylene matrix ) ◦ Pycrete (sawdust in ice matrix) NEW COMBINATION TECHNICAL 4.3 INFILTRATION LIQUID, oxidic, DIRECT PROCESS Lanxide. REACTION TECHNIQUES IN-SITE Vapor deposition CVD and CVI, HIGH TEMPERATURE REACTIONS REACTIONS AUTO SET SHS. By the method called "in situ synthesis" can be obtained where the material forming reinforcing particles in a close relationship with the polymer and by ensuring in most cases, a good dispersion of the filler in the polymer matrix without The use of an interfacial modifier needed. Synthesis Several methods for the production in situ of polymeric compounds. Among the best known can include: vapor deposition, precursor technique, polymerization method intercalation polymerization encapsulation, etc.. There is another method that can be considered within the category of reaction in situ, and is using sonic energy to give rise to different types of materials. This chemical process is outlined as a method of ultrasonic irradiation and is framed within the branch of chemistry known as sonochemistry. The CVD technique is the reaction of a mixture of gases within a vacuum chamber (reactor) to give rise to the formation of a material in thin film form. The products of the reaction are discharged to the outside through a system of high-speed pump (pump 'roots' supported by rotary). The chemical vapor deposition (chemical vapor deposition or CVD) is based on the reaction of a mixture of gases or chemical vapors, to yield a solid product, usually as a coating on a substrate, although it is possible to obtain the material in powder form. The difference with the techniques known physical, (Physical Vapour Deposition or PVD) is that in the latter case there is no chemical reaction, and the layers are directly obtained by condensing in vacuum vapor from a solid material which is heated until the merger or bombarded with enough energetic particles. CVD techniques are known for years but, since the 60s, have experienced a rapid development (1) thanks mainly to the momentum generated by the development of the microelectronics industry. The epitaxial silicon layers deposited by the decomposition of silane (SiH4) are perhaps the best example. Currently, due to its versatility, the different CVD techniques are now one of the most widely used way to obtain high solids coatings industrial location (2). Thus, CVD is possible to synthesize a large number of very diverse properties materials (metals, semiconductors, insulators, superconductors, ferroelectrics and ferromagnetic materials, polymers, etc.), Which find a wide variety of applications.