Phase relations of the Ce2Co17–Sm2Co17 pseudo-binary system

The phase relations in the Ce2Co17-Sm2Co17 system over the whole concentration range have been studied by means of Xray powder diffraction, differential thermal analysis and scanning electron microscopy equipped with energy dispersive Xray spectroscopy. The X-ray powder diffraction results reveal that all the alloys (Ce1-xSmx)2Co17 are similar to the end member of the investigated system, Sm2Co17. It is implied that continuous solid solutions are formed in this system. The lattice parameters and unit cell volumes of (Ce1-xSmx)2Co17 solid solutions increase linearly with x increasing from 0 to 1.0. The occurrence of the polymorphic transformation reaction α-(Ce, Sm)2Co17 = β-(Ce, Sm)2Co17 is confirmed in the Ce2Co17-Sm2Co17 system, but its transition temperature cannot be determined. The differential thermal analysis measurements show that both the decomposition temperature and the Curie temperature of the (Ce1-xSmx)2Co17 alloys increase gradually with increasing Sm content. Based on the X-ray powder diffraction results and differential thermal analysis data, the tentative vertical section of Ce2Co17-Sm2Co17 pseudobinary system has been constructed.

Определение термодинамических параметров в областях фазовых переходов в Cu-=SUB=-1.95-=/SUB=-Ni-=SUB=-0.05-=/SUB=-S

X-ray diffraction and differential thermal analysis data obtained in the Cu_1.95Ni_0.05S phase-transition region are analyzed. It is established that the low-temperature rhombic α phase in Cu_1.95Ni_0.05S transforms to the hexagonal β phase at temperatures of 370–390 K and to the cubic γ phase at temperatures of 740–765 K according to the scheme $$\alpha \to \mathop {\alpha + \beta }\limits_{370 - 390K} \to \mathop {\alpha + \gamma }\limits_{740 - 765K} \to \gamma $$ α → α + β 370 − 390 K → α + γ 740 − 765 K → γ . It is determined (using the temperature dependence of differential thermal analysis) that the transition α → β is accompanied by heat absorption while the transition β → γ is accompanied by heat release. It is found that both transitions are allowed and belong to the reconstructive type. Both transitions are found to occur in a fluctuation volume of ~10^–20 cm^3 at temperature rates of 0.11 and 0.08 K^–1. It is demonstrated that the transition α → γ is accompanied by alternation of the structures passing through the intermediate β phase, which is incommensurate with respect to the α and γ phases.

Heat-Induced Degradation Processes in Forest Soils

Degradation by heating was studied in samples from the top 5 cm of six woolandHumic Cambisols under Ulex and Pinus pinaster stands in N.W. Spain. After heating to various temperatures, the samples were exposed for 30 minutes to simulated rain with an energy of 24.16 joul m-2 mm-1. Three kinds of degradation were observed: 1) loss of organic matter and water by volatilization ; 2) dry breakdown ; and 3) wet breakdown. The observed degradation processes correlated well with the differential thermal analysis data. Below 170°C, volatilization losses appeared, but there was no dry breakdown and resistance to wet breakdown increased slightly; between 170°C and 380–460°C, all three kinds of degradation increased greatly; and above 460°C, no further volatilization, non dry breakdown ocurred, and wet breakdown tended to decrease.

Phase Relations and Bulk Crystal Growth in the System CuInTe2-MnIn2Te4

ABSTRACTRecently manganese substituted I-III-VI2 compounds have been investigated. Their magnetic properties are similar to the paramagnetic transistion metal ion substituted II-VI materials, but their crystal structure is non-cubic resulting in anisotropies in their physico-chemical properties that do not exist in the zincblende structure diluted magnetic semiconductors (DMS) materials. In this paper, we report the phase relations on the pseudobinary cut CuInTe2-MnIn2Te4 based on x-ray diffraction and differential thermal analysis data. The range of chalcopyrite structure alloys of composition Cu1−xMnx□xIn2Te4 is limited to x<0.52 due to an eutectic at x=0.74, T= 734°C. A second eutectic exists at x = 0.97, T = 737.5°C. A heretofore unknown congruently melting compound exists in between the two eutectics at x= 0.85, Tm = 760°C. Also, the thus far unknown melting point of the compound MnIn2Te4 was determined (740°C ). Based on the analyses of the first to freeze parts of directionally solidified melts in this range of liquidus compositions by inductively coupled plasma emission spectroscopy the solidus is constructed.

The 14 Å phase developed in heated dickites

Dickites with well-ordered crystal structures and with relatively high dehydroxylation temperatures develop a 14 Å phase when heated to temperatures in the range 550–800°C. The actual spacing is close to 13·7–13·8 Å. Dickites with less well-ordered structures and with lower dehydration temperatures give less development of this phase or none at all. Other kaolinite group minerals do not produce a similar phase. Thermal weight-change and differential thermal analysis data show that the 14 Å phase develops to a maximum as hydroxyl ions are eliminated from the dickite structure and infrared spectroscopic data are consistent with this result. AIKα fluorescence wavelength measurements indicate that the Al ions are in four-fold coordination in the 14 Å phase. Absence of other diffraction data makes structure analysis impossible. The description ‘chlorite-like’ for the 14 Å phase is of questionable validity.