Analysis of mechanisms for hardening constructional steels by structure parameters

Contribution of different hardening mechanisms into tensile strength of carbon and low alloy steels has been evaluated on the basis of analysis of research papers and own experimental studies. It has been found out that solid solution and grain boundary strengthening provide the most contribution to tensile strength of normalized steel, whereas in structural low alloy steel low alloy steel the role of dispersion strengthening is noticed (21,4 %) along with the above strengthening components. It has been shown that thermal and chemical treatment of St5 grade steel leads to around 27,6 % growth of dislocations strengthening in rolled steel in case of accelerated cooling of hot wrought austenite

Analysis of mechanisms for hardening constructional steels by structure parameters

Contribution of different hardening mechanisms into tensile strength of carbon and low alloy steels has been evaluated on the basis of analysis of research papers and own experimental studies. It has been found out that solid solution and grain boundary strengthening provide the most contribution to tensile strength of normalized steel, whereas in structural low alloy steel low alloy steel the role of dispersion strengthening is noticed (21,4 %) along with the above strengthening components. It has been shown that thermal and chemical treatment of St5 grade steel leads to around 27,6 % growth of dislocations strengthening in rolled steel in case of accelerated cooling of hot wrought austenite

Some results of long-term variability of avalanche activity of CIS mountains

The work present the analysis of the long variation of avalanche activity of former USSR (CIS) mountains by the data of regular observations. There were determined the periods of activigation and reduction of avalanche formation with different synchronization of separate groups of regions. The common territorial time curves of the avalanche activity were derive for 11 of 13 mountains areas of CIS being analyzed. For Tien Shan and Caucasus the generel tendencies of the long-term variation of avalanche formation was differentiated in more details. For some regions the relationship is established between the avalanche formation and climatic factors (air temperature, winter precipitation).The tendency to the avalanche activity decrease on the course of the last few years, revealed on the basis of the analysis is testified by the independent observational data

Interface Excitons in Krmnen Clusters : The Role of Electron Affinity in the Formation of Electronic Structure

The formation of the electronic structure of small Kr_m clusters (m<150) embedded inside Ne_N clusters (1200<N<7500) has been investigated with the help of fluorescence excitation spectroscopy using synchrotron radiation. Electronically excited states, assigned to excitons at the Ne/Kr interface, 1i and 1'i were observed. The absorption bands, which are related to the lowest spin-orbit split atomic Kr 3P1 and 1P1 states, initially appear and shift towards lower energy when the krypton cluster size m increases. The characteristic bulk 1t and 1't excitons appear in the spectra, when the cluster radius exceeds some critical value, R_cl>Delta_1i . Kr clusters comprising up to 70 atoms do not exhibit bulk absorption bands. We suggest that this is due to the penetration of the interface excitons into the Kr_m cluster volume, because of the negative electron affinity of surrounding Ne atoms. From the energy shift of the interface absorption bands with cluster size an unexpectedly large penetration depth of delta_1i =7.0+/-0.1 A is estimated, which can be explained by the interplay between the electron affinities of the guest and the host cluster

Plasma hardening of heavily loaded parts of soil-cutting machines

The influence of plasma hardening on hardening processes of heavy-duty and, therefore, wear parts of working elements of soil-cutting machines has been studied. It is shown that surface plasma hardening of ploughshare made of structural steel 65Mn in the hardened zone with thickness of 0,8 mm leads to formation of gradient-layered (mixed) structure consisting of finely dispersed mixture decay products of fine-grained austenite with variable microhardness in the range of 760 – 395 HV. It is confirmed that the creation of gradient-layered structure and features of its formation after the surface plasma treatment are explained by ultrahigh heating and cooling rates, unattainable with traditional methods of heat treatment

Nanometric TiO 2 as NBBs for functional organic-inorganic hybrids with efficient interfacial charge transfer

International audienceThe purpose of this work is to establish a fabrication method for new electronic materials: organic-inorganic p-MAPTMS / titanium-oxo-alkoxy hybrids. The size-selected 5.2-nm TiO 2 nanoparticles (Nano Building Blocks-NBB) are generated in a sol-gel reactor with turbulent fluids micromixing. The surface exchange between propoxy and MAPTMS groups under vacuum pumping results in a stable nanoparticulate precursor available for 2-photon laser polymerisation. The hybrids demonstrate quantum yield of photoinduced charges separation 6 % and can steadily trap photoinduced electrons at number density of 6% Ti atoms. The materials are suitable for 3D-microstructuring

Quantitative analysis of cell types during growth and morphogenesis in Hydra

Tissue maceration was used to determine the absolute number and the distribution of cell types in Hydra. It was shown that the total number of cells per animal as well as the distribution of cells vary depending on temperature, feeding conditions, and state of growth. During head and foot regeneration and during budding the first detectable change in the cell distribution is an increase in the number of nerve cells at the site of morphogenesis. These results and the finding that nerve cells are most concentrated in the head region, diminishing in density down the body column, are discussed in relation to tissue polarity

Femtosecond and Ultraviolet Laser Irradiation of Graphite-Like Hexagonal Boron Nitride

Effect of the femtosecond and nanosecond UV laser irradiation (below the ablation threshold) of graphite-like hexagonal boron nitride (hBN) has been studied. Experiments were carried out with the compacted powder under high vacuum at room temperature using excimer KrF laser (248 nm). In the nanosecond operation mode, the laser-induced fluorescence spectra are found strongly modified depending on the integrated doze, which is attributed to a progressive enrichment of the surface layer by elemental boron. A slow sample recovery after the laser irradiation has been observed. On the other hand, in the femtosecond mode the fluorescence spectra depend on the laser fluence, and the changes are reversible: low energy fluorescence spectra are restored immediately when the laser energy decreases. This effect can be explained by a material bleaching, which favors a bulk centers emission. The ablation threshold has been determined as 78 mJ/cm2 in the femtosecond laser operational mode