Intermetallic compounds have proved to be interesting alternatives to heterogeneous catalysts prepared from pure noble metals or their alloys. As to study their intrinsic properties, to determine the ...crystalline structures of specific surfaces and finally to understand elementary processes of heterogeneous catalysis, single crystals of these intermetallics are needed. Inspired by the recent discovery of Ga–Ni catalysts for carbon dioxide reduction to methanol, we have grown for the first time cm3-size single crystals of trigonal Ga3Ni2. We report in detail on the synthesis and Czochralski growth from high-temperature solution using Ga as native solvent. Inclusion formation of Ga-rich fluid proved to be the most severe problem that was minimized by using an extremely low pulling rate down to 25µm/h.
•Growth of cm3-size Ga3Ni2 single crystals for catalytic studies is described in detail.•The Czochralski method from Ga-rich solution is a well-suited technique for the growth at subperitectic temperatures.•Mother liquid inclusion formation is the dominant problem, but can be reduced by extremely low pulling rates.
En el presente trabajo se reporta la actividad inhibitoria del crecimiento bacteriano por nanopartículas de cobre cementado y de cobre comercial. Se utilizaron las cepas de Staphylococcus aureus ATCC ...6538 (Gram positiva) y Escherichia coli ATCC 35218 (Gram negativa) para determinar el efecto inhibitorio mediante la concentración mínima inhibitoria de las nanopartículas diluidas en caldo de cultivo nutritivo y distribuidas en placas de ELISA. Las muestras de cobre cementado (obtenidas por procesos hidrometalúrgicos) y de cobre comercial fueron nanoestructuradas empleando un equipo de molienda mecánica. Los resultados indican que las nanopartículas de cobre comercial (a 2.5 horas de molienda) muestran acción inhibitoria del crecimiento de la cepa S. aureus y no así en la cepa E. coli. Asimismo, se determinó que la concentración mínima inhibitoria de la muestra de cobre comercial fue de 20 μg/mL frente a S. aureus. El cobre cementado (en su forma sólida y nanoestructurada) no mostró efecto inhibitorio del crecimiento en ninguna de las dos cepas estudiadas.
•An effective kind of forced convection by rotation of an inclined ampoule is used.•Inclusion-free growth of FeSb2 and CoSb3 single crystals is achieved.•Numerical modelling confirms effective mixing ...mechanism in the solution.
Sb-based compounds such as CoSb3 and FeSb2 are interesting materials for thermoelectric applications. Their single crystal growth can be achieved from high-temperature solutions that are strongly enriched in Sb. In Bridgman growth using closed ampoules, effective mixing of the solution is an important prerequisite in order to minimize the high risk of liquid inclusion formation. We have successfully grown inclusion-free single crystal of CoSb3 and FeSb2 by rotating the ampoule in a Bridgman-type crystal growth set-up being inclined by 75° with respect to the vector of gravity. Numerical modelling as well as experimental growth studies have demonstrated the strong influence of forced convection that is achieved by this modified directional solidification technique called Inclined Rotary Bridgman method.
The effect of mechanical milling in i-Al
64
Cu
23
Fe
13
quasicrystalline and ω-Al
70
Cu
20
Fe
10
crystalline phases is systematically investigated in the present work. The Al–Cu–Fe samples were ...obtained by arc furnace technique and then nanostructured by means of mechanical milling. The results indicate that the solid samples present a weak ferromagnetic behavior at 300 K, showing a saturation magnetization of 0.124 emu g
−1
for the icosahedral phase (i-phase) and 0.449 emu g
−1
for the tetragonal phase (ω-phase). These small values could be an indication that only a few percentage of Fe atoms carry magnetic moment. The magnetic response in the nanostructured ω-phase increases up to 3.5 times higher than its corresponding solid counterpart. Whereas for the i-phase this increment is about 16 times higher. Moreover, the speed of the variation of the studied physical parameters after reducing the average grain size has been obtained from the exponent (
α
) of a power law fit of the experimental data. The values of
α
, corresponding to the magnetic response, are slightly different in each phase, which should be related to the different chemical composition and/or the type of long range order. Additionally, we also search for a critical grain size. However, this critical value has not been observed in the studied samples.
The effect of mechanical milling in i-Al64Cu23Fe13 quasicrystalline and omega -Al70Cu20Fe10 crystalline phases is systematically investigated in the present work. The Al-Cu-Fe samples were obtained ...by arc furnace technique and then nanostructured by means of mechanical milling. The results indicate that the solid samples present a weak ferromagnetic behavior at 300 K, showing a saturation magnetization of 0.124 emu g-1 for the icosahedral phase (i-phase) and 0.449 emu g-1 for the tetragonal phase ( omega -phase). These small values could be an indication that only a few percentage of Fe atoms carry magnetic moment. The magnetic response in the nanostructured omega -phase increases up to 3.5 times higher than its corresponding solid counterpart. Whereas for the i-phase this increment is about 16 times higher. Moreover, the speed of the variation of the studied physical parameters after reducing the average grain size has been obtained from the exponent ( alpha ) of a power law fit of the experimental data. The values of alpha , corresponding to the magnetic response, are slightly different in each phase, which should be related to the different chemical composition and/or the type of long range order. Additionally, we also search for a critical grain size. However, this critical value has not been observed in the studied samples.
CoSb3, a skutterudite compound, is key in studying thermoelectric materials. Under compression, it undergoes a 'self-insertion' isostructural transition, redistributing large Sb atoms among ...crystallographic sites. We investigated CoSb3's structural stability up to 70 GPa using single crystal X-ray diffraction and high-resolution X-ray scattering, including Bragg Coherent Diffraction Imaging. We examined the material in three pressure transmitting media (PTMs), exploring how PTMs and nonhydrostatic stresses affect CoSb3. Notably, the 'self-insertion' transition may reduce or even make compressibility negative. Additionally, we report a previously unknown phase transformation from cubic Im-3 to trigonal R-3 above 40 GPa and discuss the phases' distinctive behaviors.
The effect of mechanical milling in i-Al
64
Cu
23
Fe
13
quasicrystalline and ω-Al
70
Cu
20
Fe
10
crystalline phases is systematically investigated in the present work. The Al-Cu-Fe samples were ...obtained by arc furnace technique and then nanostructured by means of mechanical milling. The results indicate that the solid samples present a weak ferromagnetic behavior at 300 K, showing a saturation magnetization of 0.124 emu g
−1
for the icosahedral phase (i-phase) and 0.449 emu g
−1
for the tetragonal phase (ω-phase). These small values could be an indication that only a few percentage of Fe atoms carry magnetic moment. The magnetic response in the nanostructured ω-phase increases up to 3.5 times higher than its corresponding solid counterpart. Whereas for the i-phase this increment is about 16 times higher. Moreover, the speed of the variation of the studied physical parameters after reducing the average grain size has been obtained from the exponent (
α
) of a power law fit of the experimental data. The values of
α
, corresponding to the magnetic response, are slightly different in each phase, which should be related to the different chemical composition and/or the type of long range order. Additionally, we also search for a critical grain size. However, this critical value has not been observed in the studied samples.
The effect of mechanical milling in i-Al
64
Cu
23
Fe
13
quasicrystalline and ω-Al
70
Cu
20
Fe
10
crystalline phases is systematically investigated in the present work.
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