Higher borides and oxygen-enriched Mg-B-O inclusions as possible pinning centers in nanostructural magnesium diboride and the influence of additives on their formation

The study of high pressure (2 GPa) synthesized MgB2-based materials allows us to conclude that higher borides (with near MgB12 stoichiometry) and oxygen-enriched Mg-B-O inclusions can be pinning centers in nanostructural magnesium diboride matrix (with average grain sizes of 15-37 nm). It has been established that additions of Ti or SiC as well as manufacturing temperature can affect the size, amount and distribution of these inclusions in the material structure and thus, influence critical current density. The superconducting behavior of materials with near MgB12 stoichiometry of matrix is discussed.Comment: 4 pages, 1 figues, presented at VORTEX VI-2009, accepted for Physica

Дослідження впливу умов електросинтезу на склад сплаву Ni-P

The Ni–P alloys are widely used as catalysts, magnetic and wear resistant materials. Properties of the nickel-phosphorous alloys are defined by the composition. A highly regulated technique to obtain the alloys with specified composition is the electrosynthesis. It is a relevant task to establish dependences of the alloy composition on the process conditions. In the present work we examined the influence of electrolysis parameters on the Ni–P alloy composition, obtained from the methanesulfonate and sulfate electrolytes. It is shown that an increase in the concentration of sodium hypophosphite, acidity and temperature of the electrolyte increases phosphorus content in the alloy. It was established that when carrying out the electrosynthesis under galvanostatic mode, a change in the alloy composition is predetermined by the rate of phosphorus formation. Atomic phosphorus is formed as a result of the course of two reactions. There occurs the electroreduction and disproportionation of hypophosphite-anion involving hydrogen ions. An increase in the concentration of hydrogen ions in the near-electrode layer contributes to an increase in the rate of phosphorus formation and growing phosphorus content in the alloy. That is why the alloys with a higher content of phosphorus are formed at lower pH indices of the electrolyte and at higher temperature. It was established that weak buffer properties of the methanesulfonate electrolyte are responsible for the lowered phosphorus content in the synthesized alloy. High pH index in the near-electrode layer reduces the rate of phosphorus formation. Established regularities might prove very useful when designing new technologies of the Ni–P alloy electrosynthesis of specified composition from the methanesulfonate electrolyte.Установлены зависимости состава сплава Ni-P от условий электросинтеза. Показано, что образование фосфора происходит в результате электровосстановления и диспропорционирования гипофосфита натрия при участии ионов водорода. Увеличение скорости этих реакций приводит к увеличению содержания фосфора в сплаве. На основании этого установлено, что повышение температуры и кислотности электролита являются благоприятным факторами для увеличения содержания фосфора в сплаве Ni-P Встановлено залежності складу сплаву Ni-P від умов електросинтезу. Показано, що утворення фосфору відбувається в результаті електровідновлення і диспропорціонування натрій гіпофосфіту за участю іонів гідрогену. Збільшення швидкості цих реакцій призводить до збільшення вмісту фосфору в сплаві. На підставі цього встановлено, що підвищення температури і кислотності електроліту є сприятливими факторами для збільшення вмісту фосфору в сплаві Ni-

Examining the Effect of Electrosynthesis Conditions on the Ni-P Alloy Composition

The Ni–P alloys are widely used as catalysts, magnetic and wear resistant materials. Properties of the nickel-phosphorous alloys are defined by the composition. A highly regulated technique to obtain the alloys with specified composition is the electrosynthesis. It is a relevant task to establish dependences of the alloy composition on the process conditions. In the present work we examined the influence of electrolysis parameters on the Ni–P alloy composition, obtained from the methanesulfonate and sulfate electrolytes. It is shown that an increase in the concentration of sodium hypophosphite, acidity and temperature of the electrolyte increases phosphorus content in the alloy. It was established that when carrying out the electrosynthesis under galvanostatic mode, a change in the alloy composition is predetermined by the rate of phosphorus formation. Atomic phosphorus is formed as a result of the course of two reactions. There occurs the electroreduction and disproportionation of hypophosphite-anion involving hydrogen ions. An increase in the concentration of hydrogen ions in the near-electrode layer contributes to an increase in the rate of phosphorus formation and growing phosphorus content in the alloy. That is why the alloys with a higher content of phosphorus are formed at lower pH indices of the electrolyte and at higher temperature. It was established that weak buffer properties of the methanesulfonate electrolyte are responsible for the lowered phosphorus content in the synthesized alloy. High pH index in the near-electrode layer reduces the rate of phosphorus formation. Established regularities might prove very useful when designing new technologies of the Ni–P alloy electrosynthesis of specified composition from the methanesulfonate electrolyte

Improved magnetic trapped field in thin-wall YBCO single-domain samples by high-pressure oxygen annealing

International audienc

Oxygenation of the traditional and thin-walled MT-YBCO in flowing oxygen and under high evaluated oxygen pressure

International audienc

High Pressure Synthesized Magnesium Diboride- and Dodecaboride-Based Superconductors: Structure and Properties

International audienc

Spark Plasma Synthesis and Sintering of Superconducting MgB₂-Based Materials

International audienc