Nickel-titanium

D. Stoeckel and W. Yu, Superelastic Nickel-Titanium Wire, Technical Brochure, Raychem Corporation, Menlo Park, Calif. 

Porous parts and bearings are made by both the press and sinter techniques, whereas filters are made by loose powder sintering. The metals most commonly used for P/M porous products are bron2e, stainless steel (type 316), nickel-base alloys (Monel, Inconel, nickel), titanium, and aluminum. 

Mechanical properties depend on the alloying elements. Addition of carbon to the cobalt base metal is the most effective. The carbon forms various carbide phases with the cobalt and the other alloying elements (see Carbides). The presence of carbide particles is controlled in part by such alloying elements such as chromium, nickel, titanium, manganese, tungsten, and molybdenum that are added during melting. The distribution of the carbide particles is controlled by heat treatment of the solidified alloy. 

GoldJilloys, Wrought Type. Two types of wrought gold alloys were formerly recognized by the ADA specification no. 7 for the fabrication of orthodontic and prosthetic dental appHances, ie, type I, high-precious-metal alloys, and type II, low-precious-metal alloys (gold color). Alloys of this type are seldom used in the United States they have been replaced by stainless steels and nickel—titanium alloys. 

Aluminium-mercury Bismuth-plutonium Copper-zirconium Nickel-titanium... 

Trimethylantimony Nickel-titanium Ethyidi methyl phosphine ... 

When nitryl fluoride is passed at ambient temperature over molybdenum, potassium, sodium, thorium, uranium or zirconium, glowing or white incandescence occurs. Mild warming is needed to initiate similar reactions of aluminium, cadmium, cobalt, iron, nickel, titanium, tungsten, vanadium or zinc, and 200-300°C for lithium or manganese. 

Nickel-tin-aluminum catalyst, 24 794 Nickel titanate, 25 47 Nickel-titanium (NiTi) alloy (Nitinol), 22 341, 712... 

Commonly, blends of organic pigments with suitable inorganic pigments are used, such as nickel titanium yellow, chrome titanium yellow, bismuth-molybdenum-vanadium-oxide, or iron oxide. 

Metal alloys can be amorphous, too. LiquidmetaF alloy is an amorphous alloy of zirconium mixed with nickel, titanium, copper, and beryllium. It is used in the heads of some brands of golf clubs. Traditional metal club heads may have microscopic gaps where planes of metallic crystals meet. These tiny gaps are a potential source of weakness. The amorphous alloy is non-crystalline, so the metal structure does not have potential breakage sites. 

The most common SMAs are nickel-titanium alloys and copper alloys of various kinds. Nitinol, a specific alloy of nickel (Ni) and titanium (Ti), is probably the most widely used. (The word nitinol comes from the chemical symbols of its two metal components, along with an abbreviation for the Naval Ordnance Laboratory, where this alloy was discovered and studied in the early 1960s.) Although nickel and titanium alloys tend to be more expensive than copper materi-... 

Alloy with Memory. In seeking a way to reduce the brittleness of titanium, U.S. Navy researchers serendipitously discovered a nickel-titanium alloy having an amazing memory. Previously cooled clamps made of the alloy (nitinol) are flexible and can be placed easily in position. When warmed to a given temperature, the alloy hardware then exerts tremendous pressure. Use of conventional clamps for holding bundles of wires or cables in a ship or aircraft structure requires special tools. For this and other applications in industry and medicine, nitinol has been in demand. The alloy, however, is not easy to produce because only minor variations in composition can affect the snap back" temperature by several degrees of temperature. 

The use of shape-memory alloys as actuators depends on their use in the plastic martensitic phase that has been constrained within the structural device. Shape-memory alloys (SMAs) can be divided into three functional groups one-way SMAs, tw o-vvav SMAs, and magnetically controlled SMAs. The magnetically controlled SMAs show great potential as actuator materials for smart structures because they could provide rapid strokes with large amplitudes under precise control. The most extensively used conventional shape-memory alloys are the nickel-titanium- and copper-based alloys (see Shape-Memory Alloys). 

Ferrocene is only one of a large number of compounds of transition metals with the cyclopentadienyl anion. Other metals that form sandwich-type structures similar to ferrocene include nickel, titanium, cobalt, ruthenium, zirconium, and osmium. The stability of metallocenes varies greatly with the metal and its oxidation state ferrocene, ruthenocene, and osmocene are particularly stable because in each the metal achieves the electronic configuration of an inert gas. Almost the ultimate in resistance to oxidative attack is reached in (C5H5)2Co , cobalticinium ion, which can be recovered from boiling aqua regia (a mixture of concentrated nitric and hydrochloric acids named for its ability to dissolve platinum and gold). In cobalticinium ion, the metal has the 18 outer-shell electrons characteristic of krypton. 

As previously mentioned, the nickel—titanium alloys have been the most widely used shape memory alloys. This family of nickel—titanium alloys is known as Nitinol (Nickel Titanium Naval Ordnance Laboratory in honor of the place where this material behavior was first observed). Nitinol have been used for military, medical, safety, and robotics applications. Specific usages include hydraulic lines capable of F-14 fighter planes, medical tweezers, anchors for attaching tendons to bones, eyeglass frames, underwire brassieres, and antiscalding valves used in water faucets and shower heads (38,39). Nitinol can be used in robotics actuators and micromanipulators that simulate human muscle motion. The ability of Nitinol to exert a smooth, controlled force when activated is a mass advantage of this material family (5). 

Shape-memory alloys (e.g. Cu-Zn-Al, Fe-Ni-Al, Ti-Ni alloys) are already in use in biomedical applications such as cardiovascular stents, guidewires and orthodontic wires. The shape-memory effect of these materials is based on a martensitic phase transformation. Shape memory alloys, such as nickel-titanium, are used to provide increased protection against sources of (extreme) heat. A shape-memory alloy possesses different properties below and above the temperature at which it is activated. Below this temperature, the shape of the alloy is easily deformed due to its flexible structure. At the activation temperature, the alloy can be changed by applying a force, but the structure resists this deformation and returns back to its initial shape. The activation temperature is a function of the ratio of nickel to titanium in the alloy. In contrast with Ni-Ti, copper-zinc alloys are capable of a two-way activation, and therefore a reversible variation of the shape is possible, which is a necessary condition for protection purposes in textiles used to resist changeable weather conditions. 

This problem has been partially overcome by elimination of the phosphorus-oxygen bonds, as, for example, in the poly(phosphinoisocyanates), which have the structure shown in 6.47.42 It is also possible to form poly(metal phosphinates) with repeat unit -M(0PR20)2- by allowing a metal alkoxide to react with a phosphinic acid.43 Typical metal atoms are aluminum, cobalt, chromium, nickel, titanium, and zinc.43 Polymeric phosphine oxides can be prepared by the reactions... 

The discovery of the shape memory effect in TiNi by Buehler et al. at the Naval Ordinance Labs occurred during an investigation of the alloy for possible use as a corrosion-resistant knife for underwater activities. The investigators called the alloy nitinol for Nickel, Titanium, and Naval Ordinance Labs. 

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