FINEMET-type thin films deposited by HiPIMS: Influence of growth and annealing conditions on the magnetic behaviour

Results concerning the influence of deposition conditions (effective power, P_eff, pulse length, τ, and working gas pressure, p) as well as of thermal treatments on the properties of Fe_73.5Cu₁Nb₃Si_15.5B₇ thin films, deposited by high power impulse magnetron sputtering (HiPIMS) technique, are presented. The P_eff, τ and p values were varied in the range of 30–90 W, 4–20 μs and 8–60 mTorr respectively. According to the XRD analysis, in as-deposited state, all the prepared samples are amorphous. For P_eff constant the coercive magnetic field, H_c, increases whit τ, while for τ constant H_c decreases when P_eff increases. The lowest H_c values have been obtained after the samples were annealed at temperatures between 450 °C and 480 °C, when the average size of the α-Fe(Si) grains and the crystalline volume fraction increase about 45% and 20% respectively.     

Upon the characterization of semi-synthetic hydrogels based on poly (NIPAM) inserted onto collagen sponge

The preparation of a semi-synthetic hydrogel based on poly(N-isopropyl acrylamide-co-diethylene glycol diacrylate) inserted onto a collagen porous membrane, it was previous presented. The synthesis of the hydrogels was performed through radical copolymerization of N-isopropyl acrylamide (NIPAM) with diethylene glycol diacrylate (DEGDA) also as crosslinking agent, using ammonium persulfate as initiator and N,N,N′,N′-tetramethylethylene diamine activator, and it was achieved in the presence of the collagen matrix. In this paper the thus prepared hydrogels are characterized by Differential Scanning Calorimetry, Scanning Electron Microscopy and for their swelling capacities. A kinetic model was studied to investigate the swelling mechanism of the semi-interpenetrated polymeric network. The swelling behavior was found dependent on the hydrogel composition and to the external stimuli such as temperature and pH of environment. This manner of acting recommends these materials as smart materials with potential applications in tissue engineering and pharmaceutical field as for example bioproducts carrier matrices.     

Accurate measurement of domain wall velocity in amorphous microwires, submicron wires, and nanowires

A new method for measuring the domain wall velocity in a single, ultrathin ferromagnetic amorphous wire with the diameter down to 100 nm is presented. The method has been developed in order to increase the sensitivity in studying the domain wall propagation in bistable magnetic wires in a wide range of field amplitudes, with much larger values of the applied field as compared to those employed when studying the wall propagation in typical amorphous microwires. The large fields required to propagate the domain walls in ultrathin wires are able to nucleate new domain walls in the samples and, therefore, they can affect the accuracy of the entire measurement. The proposed experimental setup prevents such situations by using a number of complex pick-up coils, which allow the detection of the direction of the wall propagation along with the precise measurement of the domain wall velocity. The newly developed method is especially important now, when large effort is devoted to the development of domain wall logic devices based on ultrathin magnetic wires and nanowires.     

Effect of emulsion polymerization and magnetic field on the adsorption of albumin on poly(methyl methacrylate)-based biomaterial surfaces

The adsorption of bovine serum albumin (BSA) onto the surfaces of poly(methyl methacrylate) (PMMA) and of methyl methacrylate copolymer with 2,3-epoxypropyl methacrylate, it was investigated. The polymeric matrices were obtained through radical emulsion polymerization with and without the presence of a continuous external magnetic field (MF) of 1,500 Gs intensity. Two types of surfactant agents were used for polymers’ synthesis: a classic one sodium lauryl sulphate (SLS) and β-cyclodextrin (CD). The protein adsorption was conducted in the presence as well as in the absence of MF, by varying the coupling conditions, respectively, the temperature, pH and albumin/polymer ratio. The study underlines the assistance of MF during the adsorption process, materialized into growth of the BSA adsorbed quantity. Thus, MF presence during adsorption determines the doubling of the BSA adsorbed quantity onto the surface of polymers prepared in the MF. The adsorption process was also related to the tensioactive used for the synthesis of polymeric matrices. The higher content of the adsorbed BSA corresponds to the polymers with CD instead of SLS. The fact was attributed to the catalytic activity of the MF, which determines the molecules distortions, the growth of distance interactions and the modifications of the angles between bonds, with benefit effect upon adsorption.     

Cu—Fe—Zr三元系统基的非铁合金

提出了微合金化铜基合金在真空条件下优选工艺和通过减少ＣｕＦｅ２Ｐ合金中Ｐ含量及用Ｚｒ，Ａｌ，Ｍｇ，Ｚｎ等对ＣｕＦｅ２Ｐ进行微合金化改善其性能，实验发现，对微合金化ＣｕＦｅＺｎ合金，高的铁锆比（Ｆｅ／Ｚｒ）与性能有良了的对应关系，而对微合金化ＣｕＦｅＺｒ合金，低的较宽范围的Ｆｅ／Ｚｒ与性能有良好的对应关系。     

Thermal behaviour of a series of poly[B-(methylamino)borazine] for the preparation of boron nitride fibers

The thermal behaviour of a series of poly[B-(methylamino)borazine] prepared at various temperatures ranging from 140 to 200 °C is studied in the present paper as potential BN fiber precursors. It was shown that the softening capability of poly[B-(methylamino)borazine] can be tailored by controlling the temperature at which polymers were prepared to achieve melt-spinning and produce high quality green fibers. Thus as-spun fibers could be next converted into boron nitride fibers using ammonia (25–1000 °C) and nitrogen (25–1800 °C) atmospheres. The quality of boron nitride fibers was shown to depend on the first part of the pyrolysis step (25 and 1000 °C; ammonia atmosphere) in which the great majority of the weight loss necessary for boron nitride production occurs. Ideal poly[B-(methylamino)borazine] as BN fiber precursors are those prepared between 170 and 180 °C. They display appropriate melt-spinnability and ceramic conversion capability.     

Possibilities of collagen adsorption on some polymeric matrices based on styrene copolymers

Seven matrices based on polystyrene and styrene copolymers, with acrylic and methacrylic acid, acryl‐ and methacrylamide, and acrylonitrile and maleic anhydride, are tested in respect of their capacity of collagen adsorption. The aim of the study is to correlate the collagen coupling capacity by the nature of the monomers and the ability of functional groups to obtain biomaterials. The prepared vinylic polymers are relatively hydrophobic. These hydrophobic properties, together with the large mesh interstices, hinder smooth‐cell seeding. In contrast, collagen offers the advantage of specific cell interactions and hydrophilicity. Therefore, synthetic polymers and collagen have been hybridized to combine their advantages. The biocompatibilization process consists of physical immobilization of the protein onto the synthesized matrice surfaces. The content of the adsorbed protein was correlated with the conditions of capture, solution pH, and sorption temperature, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3554–3561, 2006     

Magnetic composites obtainment based on styrene polymers

Three styrene‐based matrices for hybrid composites with ferrite have been obtained by emulsion polymerization in the presence of a tensioactive system: sodium n‐dodecylbenzene sulfate (C₁₂H₂₅C₆H₄SO₃Na) as anionic agent and poly(oxyethylene) nonylphenyl ether [C₉H₁₉C₆H₄(OCH₂CH₂)₃₀OH] as nonionic tensioactive agent. The system assures the steadiness of the emulsion during the reaction and the stability of the latices. The surfactants act as a protective colloid component and thickening agents determining an optimum viscosity and conditions for the further catching of the inorganic oxide with magnetic properties. The obtained polystyrene and styrene copolymers with acrylamide and methacrylamide were analyzed by elemental analysis, IR spectroscopy, DSC, and their viscosity data have been characterized. The size as well as the magnetic properties of composites were also appreciated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4133–4141, 2006     

Structural and thermal properties of boron nitride nanoparticles

In the present study, our main motivation was to investigate the structural and thermal stability of BN nanoparticles (B_1.0N_0.9-NPs) produced by spray-pyrolysis (SP) of borazine at 1400 °C by thermogravimetric experiments and X-ray diffraction. We observed that B_1.0N_0.9-NPs are relatively stable in air below 850 °C in which only oxidation of the NP surface proceeded. Above 850 °C, the powders started to strongly react with air due to bulk oxidation. Under nitrogen, they appeared to be less stable than plate-like BN synthesized from borazine at 1400 °C through conventional pyrolysis. This is related to the low degree of crystallization of B_1.0N_0.9-NPs that clearly affects their stability. Using a post-pyrolysis treatment at 1400 °C, B_1.0N_0.9-NPs remained stable up to 1600 °C similarly to plate-like BN. However, above 1600 °C, a relatively fast weight loss occurred for B_1.0N_0.9-NPs, whereas plate-like BN remained stable up to 1800 °C. This indicated that their lower size also affects their high temperature thermal behavior.