5 research outputs found
Deposition of Thick SiO2 Coatings to Carbonyl Iron Microparticles for Thermal Stability and Microwave Performance
Thick dielectric SiO2 shells on the surface of iron particles enhance the thermal and electrodynamic parameters of the iron. A technique to deposit thick, 500-nm, SiO2 shell to the surface of carbonyl iron (CI) particles was developed. The method consists of repeated deposition of SiO2 particles with air drying between iterations. This method allows to obtain thick dielectric shells up to 475 nm on individual CI particles. The paper shows that a thick SiO2 protective layer reduces the permittivity of the ‘Fe-SiO2—paraffin’ composite in accordance with the Maxwell Garnett medium theory. The protective shell increases the thermal stability of iron, when heated in air, by shifting the transition temperature to the higher oxide. The particle size, the thickness of the SiO2 shells, and the elemental analysis of the samples were studied using a scanning electron microscope. A coaxial waveguide and the Nicholson–Ross technique were used to measure microwave permeability and permittivity of the samples. A vibrating-sample magnetometer (VSM) was used to measure the magnetostatic data. A synchronous thermal analysis was applied to measure the thermal stability of the coated iron particles. The developed samples can be applied for electromagnetic compatibility problems, as well as the active material for various types of sensors
Deposition of Thick SiO<sub>2</sub> Coatings to Carbonyl Iron Microparticles for Thermal Stability and Microwave Performance
Thick dielectric SiO2 shells on the surface of iron particles enhance the thermal and electrodynamic parameters of the iron. A technique to deposit thick, 500-nm, SiO2 shell to the surface of carbonyl iron (CI) particles was developed. The method consists of repeated deposition of SiO2 particles with air drying between iterations. This method allows to obtain thick dielectric shells up to 475 nm on individual CI particles. The paper shows that a thick SiO2 protective layer reduces the permittivity of the âFe-SiO2âparaffinâ composite in accordance with the Maxwell Garnett medium theory. The protective shell increases the thermal stability of iron, when heated in air, by shifting the transition temperature to the higher oxide. The particle size, the thickness of the SiO2 shells, and the elemental analysis of the samples were studied using a scanning electron microscope. A coaxial waveguide and the NicholsonâRoss technique were used to measure microwave permeability and permittivity of the samples. A vibrating-sample magnetometer (VSM) was used to measure the magnetostatic data. A synchronous thermal analysis was applied to measure the thermal stability of the coated iron particles. The developed samples can be applied for electromagnetic compatibility problems, as well as the active material for various types of sensors
Deposition of a SiO2 Shell of Variable Thickness and Chemical Composition to Carbonyl Iron: Synthesis and Microwave Measurements
Protective SiO2 coating deposited to iron microparticles is highly demanded both for the chemical and magnetic performance of the latter. Hydrolysis of tetraethoxysilane is the crucial method for SiO2 deposition from a solution. The capabilities of this technique have not been thoroughly studied yet. Here, two factors were tested to affect the chemical composition and the thickness of the SiO2 shell. It was found that an increase in the hydrolysis reaction time thickened the SiO2 shell from 100 to 200 nm. Moreover, a decrease in the acidity of the reaction mixture not only thickened the shell but also varied the chemical composition from SiO3.0 to SiO8.6. The thickness and composition of the dielectric layer were studied by scanning electron microscopy and energy-dispersive X-ray analysis. Microwave permeability and permittivity of the SiO2-coated iron particles mixed with a paraffin wax matrix were measured by the coaxial line technique. An increase in thickness of the silica layer decreased the real quasi-static permittivity. The changes observed were shown to agree with the Maxwell Garnett effective medium theory. The new method developed to fine-tune the chemical properties of the protective SiO2 shell may be helpful for new magnetic biosensor designs as it allows for biocompatibility adjustment
Associated production of prompt and mesons in collisions at
International audienceThe associated production of prompt and mesons in collisions at a centre-of-mass energy of is studied using LHCb data, corresponding to an integrated luminosity of . The measurement is performed for () mesons with a transverse momentum in the rapidity range . In this kinematic range, the cross-section of the associated production of prompt and mesons is measured to be , with a significance of , and that of prompt and mesons to be , with a significance of . The first uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the first observation of the associated production of and in proton-proton collisions. Differential cross-sections are measured as function of variables that are sensitive to kinematic correlations between the and mesons. The effective cross-sections of the associated production of prompt and mesons are obtained and found to be compatible with measurements using other particle productions
Search for the lepton-flavour violating decays and
A search for the lepton-flavour violating decays and is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of . No significant signals are observed and upper limits of \begin{align} {\cal B}( B^0 \to K^{*0} \mu^+ e^- ) &< \phantom{1}5.7\times 10^{-9}~(6.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^- e^+ ) &< \phantom{1}6.8\times 10^{-9}~(7.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^\pm e^\mp ) &< 10.1\times 10^{-9}~(11.7\times 10^{-9}),\newline {\cal B}( B_s^0 \to \phi \mu^\pm e^\mp ) &< 16.0\times 10^{-9}~(19.8\times 10^{-9}) \end{align} are set at confidence level. These results constitute the world's most stringent limits to date, with the limit on the decay the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.A search for the lepton-flavour violating decays B â KÎŒe and â ÏÎŒe is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of 9 fb. No significant signals are observed and upper limits ofare set at 90% (95%) confidence level. These results constitute the worldâs most stringent limits to date, with the limit on the decay â ÏÎŒe the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.[graphic not available: see fulltext]A search for the lepton-flavour violating decays and is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of . No significant signals are observed and upper limits of \begin{align} {\cal B}( B^0 \to K^{*0} \mu^+ e^- ) &< \phantom{1}5.7\times 10^{-9}~(6.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^- e^+ ) &< \phantom{1}6.8\times 10^{-9}~(7.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^\pm e^\mp ) &< 10.1\times 10^{-9}~(11.7\times 10^{-9}),\newline {\cal B}( B_s^0 \to \phi \mu^\pm e^\mp ) &< 16.0\times 10^{-9}~(19.8\times 10^{-9}) \end{align} are set at confidence level. These results constitute the world's most stringent limits to date, with the limit on the decay the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios