Erich Reiffenstein

Strukturchemische und magnetochemische Untersuchungen an Komplexcarbiden

Der Metall-Metall-Austausch in Komplexcarbiden wird rontgenographisch und magnetochemisch untersucht. Das β-Mn-Carbid Mo3Al2C ist bis MoCr2Al2C homogen, die Mischphase weist auf antiferromagnetisches Verhalten hin. Im η-Carbid Nb3(Cr, Al)3C besetzen die Cr-Atome zuerst die 16 d) und erst dann die 32e) Lage. Geringe Cr/Al-Substitution fuhrt zu spontaner Magnetisierung (Temperatur des flussigen Stickstoffs) in den η-Phasen Nb3(Cr, Al)3C und Ta3(Cr, Al)3C. Chrom ist der Trager des Magnetismus, wahrend sich der Oktaederverband {Nb6C} oder {Ta6C} ahnlich wie in den einfachen Carbiden verhalt.

Thermodynamische Untersuchungen im System Gold—Cadmium, 2. Mitt.

Liquidus and solidus curves of the β-AuCd phase were determined byDTA measurements. β-AuCd has a congruent melting point of 629.5°C at 47 at% Cd with no signs of other minima or maxima in the liquidus curve between 43 and 51 at% Cd. Liquid and solid Au−Cd alloys were investigated by theemf method between 40 and 90 at% Cd and 653–973 K. A consistent set of integral thermodynamic data for liquid and for solid alloys of the entire Au−Cd system were calculated at 1000 and at 700K, resp., using values taken from the literature. Partial molar entropies of Cd of solid β-AuCd and of liquid alloys in the same concentration range were compared and discussed with respect to ordering phenomena in solid and liquid alloys.

Magnetische Messungen in den Systemen Co—Se, Ni—Se und Co—Ni—Se

The magnetic behavior of the binary systems Co−Se and Ni−Se was investigated within the temperature region from 100 to 300 K. Both phases Co1−xSe and CoSe2 behave like antiferromagnetics following theCurie-Weiss law with magnetic moments between 2.22 and 3.16 μB. For the corresponding phases Ni1−xSe and NiSe2 the results indicate a feeblePauli paramagnetism. For some alloys a slight positive temperature coefficient could be observed.

Einige Probleme im Zusammenhang mit der direkten Bestimmung der spezifischen Wärmen mittels Differential Scanning-Kalorimetrie

The relation between sample mass andDSC-amplitude was investigated under various experimental conditions for vitreous quartz, both as discs and powders. Contrary to other authors3 proportionality has been found up to the highest masses (75 mg) used.A statistical analysis of the data indicates that the accuracy of directCp-measurements byDSC can be increased by determining the blank value by extrapolation of the amplitudes for several masses to zero mass instead of using the usual procedure, which involves a run with the empty pans. The overall error ofCp due to instrument errors is estimated not to exceed 2%.