Ultrasonic study of Si-oil based magneto-rheological fluid

The present study is devoted to ultrasonic characterization of Si-oil based magneto-rheological (MR) fluid. Initially, the structural, morphological and magnetic properties of carbonyl iron powder have been carried out by its X-ray diffraction (XRD), scanning electron microscope (SEM), SEM-energy dispersive X-ray analyser (SEM-EDX) and vibrating sample magnetometer (VSM) measurements. The cubic structure with lattice parameter 2.841 Å of powdered material is confirmed by XRD study while spherical particle content is confirmed by SEM measurement. The VSM measurement of powder endorses the smooth magnetization and demagnetization with no remnance and coercivity. The rheological and ultrasonic properties are measured for pure Si-oil and four synthesized MR fluids having 10–40 wt% of carbonyl iron powder. The density and viscosity of synthesized MR fluid is found to enhance with weight percentage of carbonyl iron powder. In absence of magnetic field, the longitudinal ultrasonic velocity is found to decay with temperature and concentration. In presence of magnetic field, the longitudinal ultrasonic velocity is found to enhance while velocity measured at transverse magnetic field is found to decay for each MR fluid. The change in ultrasonic velocity with concentration at fixed temperature or magnetic field resembles the magnetization characteristics of disperse powder in MR fluid. The study opens a new dimension for its characterization through ultrasonic non-destructive technique.

Mechanoluminescence of a composite based on polymethylmethacrylate and fine-disperse powder of phosphor excited by short acoustic pulses and dynamic action of the stylus

A composite mechanoluminescent layer has been produced on the surface of polymethylmethacrylate by liquid-phase embedding of [Formula: see text] phosphor microparticles into the polymethylmethacrylate surface layer. The photoluminescence and mechanoluminescence of the obtained layer have been investigated. The mechanoluminescence was excited by the short acoustic pulses and by the dynamic pressure of the stylus sliding over the mechanoluminescent layer surface. A possible mechanism of mechanoluminescence excitation is under discussion. The produced composite layer is shown to exhibit high efficiency of “mechano-optical” transformation.

Fabrication and characterization of magnetic FePt nanoparticles prepared by extraction–pyrolysis method

In the present work, possibilities of the extraction–pyrolysis method (EPM) to produce FePt nanoparticles with the face-centered tetragonal (fct) phase were studied. A mixture of fine-disperse powder of carbonyl iron and n-trioctylammonium hexachloroplatinate [(С8Н17)3NH]2PtCl6 solution in toluene, preliminary produced by the solvent extraction method, is used as a precursor. Precursors with a different molar ratio of metals were used. The performed investigations show that as a result of pyrolysis in the air (Tpyr = 600°C, tanneal = 30 min), a FePt alloy with the fct phase is produced. Moreover, such phases as FePt3 and/or Fe3Pt with the cubic structure may be also present in the final products. The phase composition of the produced samples depends on the Fe:Pt molar ratio in the precursor. An increase of the fct phase part with the growth of the iron content from 40 to 60 mol% is observed. Also, with the Fe80%Pt20% molar ratio of the metals in the precursor, only the ordered fct phase along with a small amount of hematite and iron chloride exists in the produced sample. Magnetic measurements confirm the fct-FePt phase formation in all produced samples and evidence that the coercivity exceeds the value (3 kOe) at the 50 mol% Fe concentration in the precursor and significantly decreases with increasing the Fe concentration to 80 mol%.

Steel GX120Mn12 Modifying by Ultra Disperse Powders of Refractory Metal Oxides

The article provides a consideration of the technology of producing steel GX120Mn12 with high manganese content modified by the special modifier to improve constructional durability of details manufactured. The ultra disperse powder of refractory metal oxides was used to carry out the process of modifying. The samples were produced in the series of cast and tested mechanically. Structural research demonstrated improvement of steel microstructure and that of its mechanical characteristics. It also revealed that the size of austenite grain and nonmetallic inclusions on borders of grains were reduced, and sulphide inclusions were dissolved partially. It has positive impact on work characteristics of this steel.

Low temperature photoluminescence and deformation luminescence of microparticles SrAl2O4:(Eu2+, Dy3+) in a matrix of photopolymer

The paper deals with low-temperature photoluminescence and deformation luminescence (mechanoluminescence) of a composite material based on fine disperse powder of phosphor SrAl 2 O 4:( Eu 2+, Dy 3+) and photopolymerizing resin that is transparent in the visible region. New information about the energy levels of impurities and defects was obtained. It has been found that at low temperatures (T = 15 ÷ 200 K) the photoluminescence spectrum of SrAl 2 O 4:( Eu 2+, Dy 3+) presents two partially overlapping wide bands with the maxima at λ1 max = 446 nm and λ2 max = 517 nm. The strong interaction of energy states of the bands results in temperature quenching of the short-wave band of luminescence (λ1 max = 446 nm) and its complete attenuation at T ≥ 200 K. The results were used to describe the mechanism of persistent luminescence and mechanoluminescence of SrAl 2 O 4:( Eu 2+, Dy 3+).

BULK NANOSTRUCTURED MATERIALS OBTAINED BY SHOCK WAVES COMPACTION OF ULTRAFINE TITANIUM AND ALUMINUM

Theoretical and experimental Investigations of shock wave consolidation processes of Ti - Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatic of Ti and Al . The normal and tangential stresses in the cylindrical steel tube (containers of Ti - Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (≤ 50nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallics with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al . Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20) GPa. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallics phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.

Effect of ultra-disperse powder оf zirconate-titanate lead on morphological and functional status of kidney studied experimentally

Rat experiments revealed that daily inhalation of ultra-disperse powder (UDP) оf zirconate-titanate lead in a dose of 15 mg/m3 re-sult in increased contents of single element of UPD in kidneys and cause changes of morphological and functional status of the or-gan. According to accumulation degree in kidneys, the studied chemical elements are situated in the following sequence: Pb > Ti > Cr > Mn. The presented results are indicative of moderately expressed toxic effect of UDP of circonate-titanate lead on morphological and functional status of rat's kidney, been subjected to its inhalation influence.