Melting points micro methods

Determination of Melting-points. The determination of the melting-point, as described on pp. 2-4, is of course in itself a micro-method. Even so, when working on a very small scale it is advantageous to use either ... 

The hardness of carbides can only be deterrnined by micro methods because of britdeness, the usual macro tests caimot be used. Neither can the extremely high melting points of the carbides be readily deterrnined by the usual methods. In the so-called Priani hole method, a small hoUow rod is placed between two electrodes and heated by direct current until a Hquid drop appears in the cavity. The temperature is determined pyrometricaHy. When high temperature tungsten tube furnaces are used, the melting point can readily be estimated by the Seger-type cone method. The sample may also be fused in a KroU arc furnace and the solidification temperature determined. 

Melting Point, Determination. Most methods for the detn of mp are microprocedures, and may be conveniently classified on the basis of the type of app used for the detn (1) the capillary tube method. (2) the heating bar method, and (3) the microscope heating stage (micro hot stage) method. 

Several micro methods have been developed for the determination of the melting point, using one or two crystals of the substance. In most of these methods the crystals are placed on a slide and covered with a cover glass. The slide is then placed on a metal plate which is heated electrically by resistance wires. The temperature is measured by a thermometer or thermocouple placed close to the sample. The change in the crystals is observed through a magnifying lense or a microscope. 

Molten salt synthesis based on the use of salts with low melting point has been reported to be one of the simplest techniques for preparing ceramic materials [57]. Well-faced LNM crystals were synthesized by molten salt technology using stoichiometric amount of LiOH, Ni(OH)2, and y-MnOOH (2 1 3) calcined at 700-1000 °C [57]. Micro-sized LNM crystals in plate and octahedral shapes were synthesized by molten-salt method in LiCl and LiCl-KCl fluxes the main surface facets on the plates were determined to be (112) crystal planes [58]. Recenfly, microscale LNM was synthesized using nanothom stmctured MnOa mixed with Li and Ni precursors [59]. 

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