Effect of feeding Ca–Mg–RE–Zr composite cored wire during refining of liquid steel on weldability of ultrahigh strength wear resistant steels

The weldability and mechanical properties of an ultrahigh strength wear resistant steel were substantially improved by the addition of a small amount of Ca–Mg–RE–Zr composite (1·5 kg t^?1) to the molten steel during the refining stage. Based on optical and electron microscopy examinations, the observed improvements were attributed to the enhanced pining effect of inclusions on the original austenite grain boundaries within the coarse grained heat affected zone, as well as the inclusion induced acicular ferrite formation within the fine grained heat affected zone.     

Photovoltaic Ge/Si quantum dot detectors operating in the mid-wave atmospheric window (3-5 micrometers)

ABSTRACT: Ge/Si quantum dots fabricated by molecular-beam epitaxy at 500C are overgrown with Si at different temperatures Tcap, and effect of boron delta-doping of Si barriers on the mid-infrared photoresponse was investigated. The photocurrent maximum shifts from 2.3 to 3.9 micrometer with increasing Tcap from 300 to 750C. Within the sample set, we examined devices with different positions of the delta-doping layer with respect to the dot plane, different distances between the delta-doping layer and the dot plane d, and different doping densities pB. All detectors show pronounced photovoltaic behavior implying the presence of an internal inversion asymmetry due to the placing dopants in the barriers. The best performance was achieved for the device with Tcap=600C, pB=12x10^{11} cm^{-2}, and d=5 nm in a photovoltaic regime. At a sample temperature of 90K and no applied bias, a responsivity of 0.83 mA/W and detectivity of 8x10^{10} cmHz^{1/2}/W at lambda=3.4 micrometer were measured under normal incidence infrared radiation.     

On η5 -π-Complexes of C70 and Some of its Cyclopentadienyl Derivatives with Li Atoms: MNDO Simulation

Abstract

The molecular and electronic structure of hypothetical η⁵ -complexes of C₇₀ and its cyclopentadienyl derivatives such as C₇₀R₅, C₇₀R₁₀ and C₆₀X₁₀ (R = H, Cl, Br; X = B, N, Al, P) with Li are discussed. It was proposed that atoms R were attached to the α-positions of one (two) polar pentagon(s) of prolated shape fullerene (D_5n)-C₇₀, and atoms X substituted atoms C in same sites. It was established that the complexes under consideration were more stable systems in comparison with unsubstituted C₇₀. The MNDO method was used. The results obtained are generalizing theoretical studies of electron stucture of similar complexes of fullerene C₆₀ and its derivatives such as C₆₀R₅ and C₅₅X₅.     

Supercritical fluid extraction of minor components of vegetable oils: β-Sitosterol

The extracts of valuable vegetable oils containing a number of minor components (sterols, tocopherols, carotenoids, etc.) have added value as pharmaceuticals and food additives. Beta-sitosterol (BS) as minor component of vegetable oil was extracted from ground seeds of sea buckthorn with supercritical CO₂ at pressures 15-60 MPa and temperatures 40-80 °C. The changes in the BS content in extract in the course of the extraction were evaluated using HPLC and described in terms of phase equilibrium. It was shown that the separation factors used in counter-current fractionation of oils apply also to the initial period of oil extraction from ground seeds. The equilibrium compositions of a model BS + trilinolein + CO₂ mixture were calculated using SRK and PSRK equations of state. The BS to triacylglycerol separation factor, ranging from 1.0 to 3.1, was correlated with CO₂ density.     

Influence of High Pressure and Temperature on the Structure and Properties of the WC–6Co Hard Alloy

The results are presented of the barothermal treatment studies of a WC–6Co hard alloy at high pressure (7 GPa). It is shown that such a treatment of hard alloy leads to the deterioration of the basic physico-mechanical characteristics, specifically the strength at the contact, and the coercive force, which is stipulated by the increase of the defects amount in the structure of the carbide phase of the hard alloy.     

Visible and NIR Upconverting Er3+–Yb3+ Luminescent Nanorattles and Other Hybrid PMO‐Inorganic Structures for In Vivo Nanothermometry

Lanthanide‐doped luminescent nanoparticles are an appealing system for nanothermometry with biomedical applications due to their sensitivity, reliability, and minimal invasive thermal sensing properties. Here, four unique hybrid organic–inorganic materials prepared by combining β‐NaGdF₄ and PMOs (periodic mesoporous organosilica) or mSiO₂ (mesoporous silica) are proposed. PMO/mSiO₂ materials are excellent candidates for biological/biomedical applications as they show high biocompatibility with the human body. On the other hand, the β‐NaGdF₄ matrix is an excellent host for doping lanthanide ions, even at very low concentrations with yet very efficient luminescence properties. A new type of Er³⁺–Yb³⁺ upconversion luminescence nanothermometers operating both in the visible and near infrared regime is proposed. Both spectral ranges permit promising thermometry performance even in aqueous environment. It is additionally confirmed that these hybrid materials are non‐toxic to cells, which makes them very promising candidates for real biomedical thermometry applications. In several of these materials, the presence of additional voids leaves space for future theranostic or combined thermometry and drug delivery applications in the hybrid nanostructures.     

Effect of the Polymerization Degree,Moisture Content,and Temperature on Kinetics of Hydrolysis of Corn Starch by Alpha-Amylase

Effect of the polymerization degree, moisture content, and temperature on kinetics of hydrolysis of corn starch by α-Amylase was studied. The degree of hydrolysis of the corn starch by α-amylase at low moisture content was shown to be strongly dependent on the initial starch polymerization degree and the thermodynamic activity of water in the system.     

Effect of the rate of cooling tungsten heavy alloys of the W–Ni–Fe type from the sintering temperature on the formation of their physico-mechanical properties

The effect of the conditions of cooling after the liquid-phase sintering of tungsten heavy metals have been studied. It has been found that to attain a high ductility of the tungsten heavy metal, the rate of cooling from the sintering temperature should afford removal of the major part of hydrogen, which was dissolved in the alloy volume in the temperature range of the liquid phase existence.     

Effect of the thermal treatment of the initial tungsten-containing raw material on the structure and properties of WC–Co type hard alloys with particularly fine-grained structures

A method has been proposed to produce the WC–Co type tungsten hard alloys having particularly fine-grained structures by homogenizing annealing of the initial components, which allows us to obtain a particularly disperse tungsten-containing component. By this means it has been possible to avoid a long grinding of hard-alloy mixtures and produce alloys with high physico-mechanical characteristics.