Search results for "Melting"

High-pressure/high-temperature phase diagram of zinc

2018

The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300K up to the melting temperature. The pressure at which c/a reaches root 3 (approximate to 10GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple pol…

Microscopic evidence of a flat melting curve of tantalum

2010

International audience; New data on the high-pressure melting curve of Ta up to 48GPa are reported. Evidence of melting from changes in sample texture was found in five different experiments using scanning electron microscopy. The obtained melting temperatures are in excellent agreement with earlier measurements using x-ray diffraction or the laser-speckled method but are in contrast with several theoretical calculations. The results are also compared with shock-wave data. These findings are of geophysical relevance because they confirm the validity of earlier experimental techniques that resulted in low melting slopes of the transition metals measured in the diamond-anvil cell, including i…

Insights into the compositional evolution of crustal magmatic systems from coupled petrological-geodynamical models

2020

Funding was provided by the VAMOS Research Center, University of Mainz (Germany) and by the ERC Consolidator Grant MAGMA (project #771143). The evolution of crustal magmatic systems is incompletely understood, as most studies are limited either by their temporal or spatial resolution. Exposed plutonic rocks represent the final stage of a long-term evolution punctuated by several magmatic events with different chemistry and generated under different mechanical conditions. Although the final state can be easily described, the nature of each magmatic pulse is more difficult to retrieve. This study presents a new method to investigate the compositional evolution of plutonic systems while consid…

The influence of strain rate and presence of dispersed second phases on the deformation behaviour of polycrystalline D2O ice

2018

ABSTRACTThis contribution discusses results obtained from 3-D neutron diffraction and 2-D fabric analyser in situ deformation experiments on laboratory-prepared polycrystalline deuterated ice and ice containing a second phase. The two-phase samples used in the experiments are composed of an ice matrix with (1) air bubbles, (2) rigid, rhombohedral-shaped calcite and (3) rheologically soft, platy graphite. Samples were tested at 10°C below the melting point of deuterated ice at ambient pressures, and two strain rates of 1 × 10−5 s−1 (fast) and 2.5 × 10−6 s−1 (medium). Nature and distribution of the second phase controlled the rheological behaviour of the ice by pinning grain boundary migratio…

Soil decomposer animal community in heavy-metal contaminated coniferous forest with and without liming

2002

Abstract Responses of decomposer animals to heavy-metal contamination were studied near a Cu–Ni smelter in Finland. Samples were taken 0.5, 2 and 8 km from the smelter. In addition, plots fertilised with lime were sampled. Decomposer community in coniferous forest soil appeared to be quite resistant to heavy-metals. Only in the vicinity (0.5 km) of the smelter, were numbers of soil animals clearly decreased and their community structure strongly altered as compared to the control site (8 km). At the 2-km site, the community structure was only slightly changed. Most of the collembolan species were still found at the 0.5-km site. High metal sorption capacity of the humus, and heterogeneous di…

Cutting Temperatures Evaluation in Ceramic Tools: Experimental Tests, Numerical Analysis and SEM Observations

1994

The authors propose a multiple approach for the evaluation of cutting temperatures in ceramic tools. The first approach was the experimental evaluation of equitemperature lines, obtained in three-dimensional cutting by employing constant melting point powders scattered on planes parallel to rake face. In the second approach, a numerical finite element analysis was performed. At this step the determination of the percentage of total heat produced in the operation that flows into the tool was considered and, consequently, the temperature distribution within the whole volume of the insert. Finally, the examination of the crater zone with SEM microscopy confirmed the temperature levels as previ…

Numerical studies of the melting process in the induction furnace with cold crucible

2008

PurposeAims to present recent activities in numerical modeling of cold crucible melting process.Design/methodology/approach3D numerical analysis was used for electromagnetic problem and 3D large eddy simulation (LES) method was applied for fluid flow modeling.FindingsThe comparative modeling shows, that higher H/D ratio of the melt is more efficient when total power consumption is considered, but this advantage is held back by higher heat losses through the crucible walls. Also, calculations reveal that lower frequencies, which are energetically less effective, provide better mixing of the melt.Originality/value3D electromagnetic model, which allows to take into account non‐symmetrical dist…

1977

The thermal behavior of cycloalkanes (CH2)n with 12 ≤ n ≤ 84 prepared by metathesis reaction of cyclododecene, GPC separation of the oligomers, and hydrogenation has been investigated. The molar enthalpies of fusion being lower by a certain amount than those of the corresponding n-alkanes are a linear function of the chain length n. The entropy of fusion per CH2 increases with chain length in a not-linear mode (when plotted vs. 1/n). The melting points of the cycloalkanes are lower than those of the corresponding n-alkanes, the difference becoming smaller with increasing chain length.

Evaluation of entropies of fusion of polychlorinated naphthalenes by model congeners: A DSC study

2006

Abstract Thirteen congeners of polychlorinated naphthalenes (PCN) were synthesized and studied by differential scanning calorimetry (DSC). Melting points (Tm) were obtained for all thirteen, and enthalpies of fusion (ΔHf) were obtained for nine congeners. Melting points of other PCNs, except for five, were found in literature. In addition, experimental ΔHf values determined by DSC were found only for 1- and 2-mono-chloronaphthalenes in the literature. The missing or uncertain values of the eight melting points and 64 enthalpies of fusion were estimated by multiple linear regressions using a set of thirteen molecular descriptors as candidates for independent variables. The stepwise model of …

Nanoscale chemistry and atomic-scale microstructure of a bulk Ni3Sn material built using selective laser melting of elemental powder blends

2021

Abstract Cubic specimens of the intermetallic Ni3Sn compound were built using selective laser melting of elemental powder blends. A specimen built at a laser power of 200 W and a scanning speed of 0.5 m/s was determined to have a homogeneous distribution of Ni and Sn on a mesoscopic scale in spite of a 2 at.% Sn deficiency. Characterization of the microstructure using the HAADF-STEM technique reveals a dispersion of ultrafine Ni particles, nanoscale chemical inhomogeneity and the formation of antiphase nanodomains in the matrix of equiaxed Ni3Sn grains. While a mesoscopic homogeneity of the specimen demonstrates a prospect of additive manufacturing of a bulk intermetallic material using sel…