On the magnetic structure of magnetite/oleic acid/benzene ferrofluids by small-angle neutron scattering

Magnetic small-angle scattering of non-polarized and polarized neutrons from ferrofluds (magnetite covered by oleic acid in benzene) is analyzed. A complex correlation in the magnetic structure is observed. It takes place at the length of more than the particle size, and has a core-shell-like organization. Along with it no spatial interparticle correlation in the nuclear structure is detected.     

Some properties of slowly decaying oscillatory solutions of KP

In this paper a class of solutions of KP is discussed. Theory of these solutions, referred to here as breathers, is developed and it is shown that a subclass of these solutions can be used to construct more general solutions of KP similarly to how the functions e^i(λx+νy) are used to perform the same task in the theory of Fourier transform. Nonlinear superposition formula for general solutions of KP similar to the Fourier expansion formula is considered.     

Magnetic properties of metastable Gd-Cr alloys

We report on the magnetization, magnetocaloric effect, magnetic ordering temperatures, saturation magnetic moments and anisotropy of sputter-deposited Gd_xCr_1−x alloys with Gd atomic concentrations, x, ranging from 0.13 to 0.52. The complex magnetic nature of the Gd-Cr films was revealed from the M×H isotherms, which do not show saturation even at an applied field of 70 kOe and a temperature of 2 K and do not exhibit a linear behavior at higher temperatures. For some of the samples, the isotherms were used to determine the isothermal entropy variation as a function of temperature, for a change of 50 kOe in the applied magnetic field. The saturation magnetic moment varies with x and follows the dilution law, implying that the Cr atoms do not contribute to the total moment of the Gd-Cr alloys. Both static magnetization and dynamic susceptibility measurements reveal the existence of a magnetic glassy behavior in the alloys, which occurs below a freezing temperature. The existence of anisotropy at low temperatures for all samples was revealed by their M×H hysteresis loops from which the in-plane coercive fields, H_c, were determined. A monotonical increase in H_c with increasing Gd concentration was observed.     

Characterization of magnetic nano-fluids via Mössbauer spectroscopy

The laser pyrolysis became a useful tool, providing various ways, in production of nano materials. The iron Mössbauer spectroscopy is one very accurate method in evidencing the physical properties and related processes in the nano scale compounds. The effect of pressure, laser spot area and induced combustion, of gas mixture and laser power on the phase composition and inside particle distribution, grain size as well as the related phenomena were investigated by temperature dependent Mössbauer spectroscopy. A selection of most relevant properties is presented and discussed in details.     

Liquid forms of pharmaceutical co-crystals: exploring the boundaries of salt formation

We present evidence of hydrogen bond formation, not salt formation, as the driving force in the liquefaction of a solid pharmaceutical in the form of a neutral acid-base complex, as exemplified by the liquid formed from a mixture of the local anesthetic lidocaine with fatty acids; these complexes exist at the boundary between simple eutectics and partially ionised ionic liquids.     

Iron catalyzed Michael addition: Chloroferrate ionic liquids as efficient catalysts under microwave conditions

The iron containing ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate ([C4mim]Cl/FeCl3; = 0.5) proved to be an efficient catalyst for the solvent-free metal catalyzed Michael addition of β-keto esters and enones. Due to the ionic structure of the catalyst, a significant acceleration of the reaction rate was observed under microwave conditions. Furthermore, recycling of the ionic liquid catalyst could be performed after simply distilling off the products.     

An iron-containing ionic liquid as recyclable catalyst for aryl grignard cross-coupling of alkyl halides

[reaction: see text] The ionic liquid butylmethylimidazolium tetrachloroferrate (bmim-FeCl(4)) was found to be a very effective and completely air stable catalyst for the biphasic Grignard cross-coupling with primary and secondary alkyl halides bearing beta-hydrogens. After simply decanting the product in the ethereal layer, the ionic liquid catalyst was successfully recycled four times.     

On the possibility of using short chain length mono-carboxylic acids for stabilization of magnetic fluids

Short chain length mono-carboxylic acids (lauric and myristic acids) are used to coat magnetite nanoparticles in non-polar organic liquids, which results in highly stable magnetic fluids. The new fluids are compared with classical organic fluids stabilized by oleic acid (OA). Magnetic granulometry and small-angle neutron scattering (polarized mode) reveal a great difference in the particle size distribution function for the studied magnetic fluids, particularly a decrease in the characteristic particle radius of magnetite when lauric and myristic acids are used instead of OA.     

High accuracy photopyroelectric investigation of dynamic thermal parameters of Fe3O4 and CoFe2O4 magnetic nanofluids

The suitability of the photopyroelectric (PPE) calorimetry in measuring the thermal parameters of nanofluids was demonstrated. The main advantages of the method (concerning nanofluids) as compared to classical calorimetric techniques are: high sensitivity and small amount of sample required. The thermal diffusivity and effusivity of some nanofluids based on Fe₃O₄ and CoFe₂O₄ type of nanoparticles (mean diameter 6.5 nm) were investigated by using two PPE detection configurations (back and front). In both cases, the information is contained in the phase of the PPE signal. Due to the high accuracy of the results (within ±0.5%) thermal diffusivity was found to be particularly sensitive to changes in relevant parameters of the nanofluid as carrier liquid, type and concentration of nanoparticles.