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THE INFERENCE UNDER THE REVIEW AND RESEARCH PROBLEM STATEMENT

Now examinations of magnetic medium with huge magnetocaloric effect (MKE), observed at a room temperature, are of great importance because of possibility of their use as working bodies (heat exchangers) of new effective solid-state magnetic cooler bodies.

Magnetic cooler bodies have transited a long trajectory to development: from early kettles of piston type with superconducting-coil electromagnets [1], to developed today rotornyh the cars using vysokoyoeffektivnye systems from constant magnets [2]. However, one aspect practically has not changed: the up-to-date cooler bodies work till now rather slowly, some cycles of magnetisation-demagnetization in a second though according to theoretical calculations, their optimum frequency of operation makes hundreds hertz [9]. Holodoproizvoditelnost the magnetic refrigerator depends on working frequency and from quantity and quality of a magnetic coolant. For today the basic efforts have been concentrated on improvement L^d and ΛSMматериалов [2, 3]. At the same time the quantity of the coolant used in the device, is restricted by the sizes of system from the constant magnets, being a magnetic field radiant. The magnification of working frequency at some orders at the expense of optimisation of the shape and the sizes of a working body (heat exchanger) is the perspective proposition as it can lead to immediate sharp pinch holodoproizvoditelnosti.

By operation on high frequencies necessary prompt transmission of heat from a coolant can be reached only thanks to a combination of process of effective heat exchange and an optimum construction of a heat exchanger. This deduction has been made for the first time in Brown's [1] operation which used plates of gadolinium in the thickness of 1 mm. Thus, to find application in technology of magnetic cooling, magnetocaloric materials should be adapted for manufacture on their bottom of heat exchangers - porous bodies with channels for a heat-transmitting fluid. The advanced geometry of a working body of a magnetic cooler body the structure from thin parallel plates or cores is considered thickness of 0,1-0,3 mm with backlashes of 0,1 mm between them [9]. Use of such configuration of heat exchangers will allow to reduce influence of fields of a natural demagnetization on quantity MKE in
Coolant [1O-13], and also will lead to magnification energoeffektivnosti a magnetic cooler body at the expense of reduction of necessary pressure of a heat-transmitting fluid in system.

Formation of heat exchangers from intermetallic compounds which are considered as the best for today magnetocaloric materials, is a challenge because of their mechanical performances. Besides obscure there is a question on influence of thermal and mechanical actions on a material at its adaptation to manufacture of heat exchangers. Therefore for the further development of magnetic refrigerating devices it is necessary to find simple and trusty expedients of manufacture of strips, plates or cores which would provide maintenance of values MKE of a coolant at observance of requirements to a heat exchanger construction.

In connection with the above-stated, the purpose of the given operation there was a studying of influence of the various thermal and mechanical actions used at making of effective heat exchangers for solid-state magnetic cooler bodies, on quantity of magnetocaloric effect in the most perspective materials.

For achievement of the given purpose following problems have been put:

- To synthesise polycrystalline samples of alloys of systems R2Fe17, RFe11Ti, RCo2, Mn5-xFexGe3, LaFe13-xSixH, to spend certification of their structure and a phase composition;

- The gained cast samples of linkings to adapt for manufacture on their bottom of heat exchangers with the given geometry, using various procedures: a prompt temper from a melt by dvuhvalkovoj proskating rinks and a method of vacuum moulding, cold to a proskating rink and kompaktirovanie powders in the polymeric binding;

- To explore influence of the dimensional factor and a structural state on quantity of physical properties (MKE, a heat capacity, a thermal conduction, transport properties) the gained materials.

The select of the given systems is caused by their unique properties: linkings R2Fe17и Mn5Ge3характеризуются by high values MKE near to a room temperature, besides an important requirement of use of a material as a working body in refrigerators is its cost. System R linkings (Fe, Ti) 12со structure ThMn12 are characterised by wide field of homogeneity, allowing to gain uniphase nanokristallicheskie samples a method of a prompt temper in
Wide interval of concentrations. Linkings RCo2 possess huge values MKE close zonnogo metamagnetic transition and are modelling objects for examinations MKE in linkings with phase transition of the first sort. Hydrides of linkings La (Fe, Si) 13являются the most perspective materials for use as working bodies of magnetic cooler bodies as possess huge values MKE close zonnogo metamagnetic phase transition of the first sort, and hydrogen introduction in a crystalline lattice of the given linkings allows to increment essentially temperatures of phase changes to 270¸350 To with maintenance of a sort of phase transition.

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A source: KARPENKOV Dmitry Jurevich. INFLUENCE of THERMAL And MECHANICAL ACTIONS ON QUANTITY of MAGNETOCALORIC EFFECT In LINKINGS 3d - And 4G-METALS. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver - 2013. 2013

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