Commercially available magnetic materials

The main properties for permanent magnet application of several commercially available magnetic materials are compared in table 17. It can be seen that the materials based on Nd-Fe-B are quite outstanding. It has to be kept in mind, however, that the properties listed pertain to room temperature and that the... 

Table. 3-M Magnetic properties of Fei4Nd2B-based magnetic materials at room temperatnre. Typical valnes of commercially available magnets...

M-type ferrites are mainly used as permanent magnet material. They have largely replaced the alnicos as preferred permanent magnet material, as a result of the lower material and processing costs. These ferrites were first introduced under the trade name Ferroxdure, the isotropic form in 1952 (22) and the anisotropic (crystal oriented) form in 1954 (23), and are widely available commercially under various trade names such as Oxid and Koerox. They cover about 55% of the world market of permanent magnet materials, corresponding to 1100 million U.S. doUars (1991), as weU as 55% of the U.S. market, at 300 million. 

Soft magnetic materials are characterized by high permeabiUty and low coercivity. There are sis principal groups of commercially important soft magnetic materials iron and low carbon steels, iron—siUcon alloys, iron—aluminum and iron—aluminum—silicon alloys, nickel—iron alloys, iron-cobalt alloys, and ferrites. In addition, iron-boron-based amorphous soft magnetic alloys are commercially available. Some have properties similar to the best grades of the permalloys whereas others exhibit core losses substantially below those of the oriented siUcon steels. Table 1 summarizes the properties of some of these materials. 

Balkus et al. investigated the commercially available Y zeolites with an unspecified particle size, after Gd(III) exchange (82,83). A detailed study was made not only on the magnetic properties, but also on the preparation and the characterization of these materials. Several factors infiu-encing the exchange, including the pH, time, and concentration, were optimized. Procedures to control the Gd(III) loading of the zeolites were developed. 

Terrafix is a transportable ex situ technology that uses screening, magnetic separation, and chemical/cementitious material for removal and fixation of metal wastes in soils or sludges. Terrafix is a commercially available technology that has been used to treat over four million tons of wastes and soils on a full-scale level. 

Magnetic sector ion microprobes are becoming increasingly important in isotopic analysis of extratenestrial materials as spot size decreases and the precision and accuracy of the measurements improve. The first of the commercially available ion microprobes used in cosmochemistry were the Cameca ims 3f-7f series machines, which initially became available in the mid-1980s. These multipurpose instruments are able to measure isotopic compositions of most elements of interest in cosmochemistry and can also be used to measure trace element abundances. Their main drawback is that the relatively small mass spectrometer can only be operated at mass-resolving powers below about 9000, and at this mass resolving power, the transmission of the mass spectrometer is very low. 

The reaction is run in a 250-mL flat-bottomed three-necked flask containing a magnetic stirrer and equipped with a gas inlet tube and a reflux condenser connected to a mercury check-valve to ventilate evolved gases. Octane is dried over sodium and freshly distilled before use. Triosmium-dodecacarbonyl and cyclopentadienylnickelcarbonyl dimer are commercially available (Strem). Alternatively, Os3(CO)12 may be synthesized from commercially available materials by a tested procedure.1... 

Following this approach, Kopelman and coworkers have prepared a pH sensor72 using as magnetic material barium ferrite nanocrystals (BaM) and as dye the dextran-linked carboxy SNARF-1, a commercially available fluorescein derivative with a convenient pKa of 7.5 and dual excitation and emission, which allows for ratiometric pH sensing. The two components were incorporated in silica nanospheres of 300 nm... 

If the sonolysis is done in the presence of a support or porous host, then colloidal metal particles are formed. These powders have a surface area over a hundred times greater than powders commercially available and are amorphous. Such materials are generally considered for catalytic reactions and not for magnetic applications. 

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