Powder magnetic

The different techniques of NDT were applied to evaluate the method allowing to give an optimal spectrum so that the interpretation can be done easily. In addition, and for the purpose of the defects quantification, we have done an optimization on the magnetic powders, colored and fluorescent, by applying magnetic powders of variable dimensions. This will enable us to estimate defects with a high precision. 

As a rule, in practice, the surface defects are revealed by the magnetic-powder and capillary methods. However, in the case of nonmagnetic materials the magnetic-powder methods are not applicable and the capillary ones do not detect the subsurface defects or defects filled with the lubricant after the grinding, wire-drawing and so on. 

Barium carbonate of finely controlled particle size reacts in the soHd state when heated with iron oxide to form barium ferrites. Magnetically aligned barium ferrite [11138-11-7] powder can be pressed and sintered into a hard-core permanent magnet which is used in many types of small motors. Alternatively, ground up magnetic powder can be compounded into plastic strips which are used in a variety of appHances as part of the closure mechanism. 

Micro-mesh sieves have been applied to the determination of solid propint ingredients (Refs 17 35) and similar materials where sieve analyses are required with great accuracy in the very fine range. They are also applicable to specific problems such as the analysis of magnetic powders, and of powders consisting of mixts of substances of different specific gravities or the preparation of clearly defined particulate fractions in a short time... 

Magnetic single-component developers in which magnetic powder is comprised in the toner itself, and... 

NiO + A1H3 + S —> 2Ni + Al + S02 + 3/lH2 with the purpose of synthesis of magnetic powders of nickel by plazmochemical method, (where EH - hydrogen atoms stream in plasmatron) [22],... 

Nickel dissolves readily in dilute nitric acid and in aqua regia. When brought into contact with fuming nitric acid it may be attacked vigorously, it may become passive, or it may yield a grey magnetic powder.3... 

When ammonium ferrocyanide, or its double compound with ammonium chloride, is heated, a black magnetic powder is obtained. This, upon ignition in air, is completely transformed into ferric oxide without any change in weight, and is believed 2 to be the dicarbide, FeC2. 

Dry Tests.—Iron salts, when moistened with hydrochloric acid and heated on a loop of platinum wire in a Bunsen flame, emit a shower of sparks. When heated on charcoal with sodium carbonate in the blowpipe flame, the compound is converted into a dark-coloured residue. If potassium cyanide is added to the sodium carbonate and iron compound, and the whole heated on charcoal in the inner flame of the blow-pipe, metallic iron is obtained as a grey, magnetic powder. 

Pavlov, V.G., Assessment of Contact Stresses and of Film Thickness During Magnetic Powder Lubrication of Gears, Russian Eng. J., 59, 3, (1979). 

For powder diffraction, all the expressions in the following paragraphs can be applied to magnetic powder diffraction by replacing the expression of the square of the structure factor by the square of the magnetic interaction vector. 

In the non-magnetic powders, pieees of 20 to 5 mm had a content below 1% but only represented 4.5% by weight of the batteries. 

Black, magnetic powder insoluble In acids and alkalies d Crystal structure NaCl t3q)e. 

Binder resins for the injection molding method are poly(amide)s and ethylene vinyl acetate copolymers, and more recently poly(ether ether ketone) (PEEK) and PPS, because of their superior properties. Crystalline resins such as PPS or PEEK require a high temperature for fusion molding of 350°C or higher, so that there is a disadvantage in that the magnetic powder of the rare earth is likely to be oxidized by the molding process. 

H. Kawato and T. Tomioka. Methods for preparing magnetic powder material and magnet, process for preparaton of resin composition and process for producing a powder molded product. US Patent 5 350558, assigned to Idemitsu Kosan Co., Ltd. (Tokyo, JP), September 27,1994. 

Calendering methods are normally used in the production of ordinary magnets used in daily life. Some ideas exist about the use of a thin sheet of a mixture of rubber or resin and the magnetic powder, such as for radially oriented magnets by rolling the sheets. However, scientific papers about the fundamental points of the techniques generally do not appear in ordinary technical magazines. 

---