Substructural characteristics of Cu (99.97%) were examined after the Twist channel angular pressing (TCAP) process carried
out at ambient temperature. Grain refinement efficiency and resulting thermal stability were evaluated after three passes
with respect to utilization of various strain paths. Results were obtained using light microscopy and X-ray diffraction methods;
Mechanical properties of extruded materials were also tested. Thermal stability was studied after application of three annealing
cycles. Based on the findings, Bc route is the most efficient strain path with respect to the grain refinement; higher speed of extrusion (10 mm/s) corresponds
with suppression of the static recrystallization. Measured strength, obtained after three passes (route A), achieved values around 440 MPa homogeneously along the cross section of the extruded material. Homogeneity of deformation
was also confirmed by micro-hardness tests. The grain size, determined after three passes, averaged out 1.2 μm. Application
of TCAP (three passes) brought markedly homogeneous deformation throughout the processed sample in comparison with classical
ECAP process. 相似文献
The theme of a second inflection point of the temperature dependence of the surface tension of water remains a subject of controversy. Using data above 273 K, it is difficult to get a proof of existence of the second inflection point, because of experimental uncertainties. Data for the surface tension of supercooled water and results of a molecular dynamics study were included into the exploration of existence of an inflection point. A new term was included into the IAPWS equation to describe the surface tension in the supercooled water region. The new equation describes the surface tension values of ordinary water between 228 K and 647 K and leads to the inflection point value at a temperature of about 1.5 °C. 相似文献
We have developed an effective approach to 1,2‐disubstituted diamondoids by palladium(II) acetate catalyzed functionalization of C H bond. Selective mono‐arylation of the adamantane framework was achieved using picolylamide as a directing group in yields up to 87 %. Kinetic studies in combination with deuterium labeling experiments, competitive experiments and mass spectrometry contribute to the mechanistic understanding of the arylation process of alkanes with number of C H bonds neighboring the directing group. Triflic anhydride promoted cyclization of the directing group generates imidazo[1,5‐a]pyridine derivatives. Acid‐mediated removal of the directing group provides access to 2‐aryl diamondoid carboxylic acids, which are common precursors for the synthesis of various bioactive compounds (drug candidates).