Physico-Chemical nanomaterials science

Thermodynamics on heat-transfer phenomena in multinanophase substances exemplified by over-stoichiometric arsenicals
Andrzej Kozdras1*, Oleh Shpotyuk2,3, Yaroslav Shpotyuk4,5 
1 Opole University of Technology
75, Ozimska str., 45370, Opole, Poland
E-mail: a.kozdras@po.opole.pl
2 Jan Dlugosz University in Czestochowa
13/15, al. Armii Krajowej, 42201, Czestochowa, Poland
3 O.G. Vlokh Institute of Physical Optics
23, Dragomanov str., 79005, Lviv, Ukraine
4 Institute of Physics, University of Rzeszow
1, Pigonia str., Rzeszow, 35-959, Poland
5 Ivan Franko National University of Lviv
107, Tarnavskogo str., 79017, Lviv, Ukraine

Thermochemical heat transfer phenomena reconstructed from heat-flow DSC measurements performed in two special regimes involving dynamic cycling and progressive step-cycling are probed in multinanophase substances, exemplified by melt-quenching and nanomilling derived As60S40, As62S38 and As64S36 arsenicals. Thermal-alteration heat transfer responses in these alloys composed of normal- and plastic-crystalline phases supplemented by dual-nature amorphous phase are found to be essentially complicated due to inter-nanocrystalline phase transformations of realgar-type As4S4 and dimorphite-type As4S3 phases. The primary calorimetric events in the studied nanomilling-modified arsenicals involve: 
(i) reduction in onset temperature ascribed to the first-order normal-to-plastic-crystalline transition (from orthorhombic α-As4S3 to rhombohedral -As4S3); 
(ii) depression effect in “pre-melting” temperature ascribed to plastic-crystalline dimorphite-type -As4S3 phase generated in its own environment; 
(iii) decreasing trend in characteristic temperatures related to decomposition of dimorphite As4S3 phase supplemented by melting of realgar-type -As4S4 phase; 
(iv) increasing trend in crystallization temperature of plastic -As4S3 phase; 
(v) high-temperature shift in overall relaxation of liquid arsenicals into stabilized heterogeneous state detected under reheating in progressive DSC step-cycling.
It is established that, in contrast to single-phase substances, nanostructured multi-nanophase systems (multinanophase substances) demonstrate unexpected increasing trend in some characteristic calorimetric heat-transfer phenomena.