Highly sensitive coulometric titration of oxygen for the characterization of solid materials at elevated temperatures

A new setup for characterization of solid material oxygen exchange and conductivity in a broad oxygen partial pressure range and at elevated temperatures is presented. The development target of this setup is directed towards the detection of ultra-low amounts of exchanged oxygen. For this, electrochemical cells made of yttria-stabilized zirconia (YSZ) were optimized and applied in a flow-through arrangement. The design and process measures enable a lower limit of detection below 100&thinsp;pmol of exchanged oxygen. Furthermore, the system characteristics concerning oxygen dispersion, titration efficiency and electrode kinetics are described.</p

ВЛИЯНИЕ МЕТОДА ПОЛУЧЕНИЯ НА АДСОРБЦИОННЫЕ СВОЙСТВА НАНОСТРУКТУРИРОВАННОГО ПОРОШКА MgO

Magnesium oxide is widely used as an adsorbent, catalyst, identifier of chemical and toxic pollutants, in water and gas purification processes. Mesoporous magnesium oxide powder has been synthesized by the method of deposition, spray pyrolysis and glycine-citrate-nitrate method, their crystal structure, microstructure, granulometric composition and adsorption properties have been studied. Optimal conditions for the production of magnesium oxide by the glycine-citrate-nitrate method have been determined, which make it possible to obtain a powder with average primary particle sizes of 12 nm and the smallest sizes of secondary particles starting from 70 nm. The influence of the method of obtaining nanostructured magnesium oxide powder on the physicochemical properties is established. High values of the total pore volume of 1.038 cm3 /g exhibited the MgO powder obtained by the precipitation method.Оксид магния находит широкое применение в качестве адсорбента, катализатора, идентификатора загрязняющих химических и токсических веществ, в процессах водо- и газоочистки. В настоящей работе методом осаждения, распылительного пиролиза и глицин-цитрат-нитратным методом синтезированы мезопористые порошки оксида магния, изучена их кристаллическая структура, микроструктура, гранулометрический состав и адсорбционные свойства. Определены наиболее оптимальные условия получения оксида магния глицин-цитрат-нитратным методом, которые позволяют получить порошок со средними размерами первичных частиц 12 нм и наименьшими размерами вторичных частиц – от 70 нм. Установлено влияние способа получения на адсорбционные свойства наноструктурированного порошка оксида магния. Высокие значения общего объема пор 1,038 см3 /г продемонстрировал порошок MgO, полученный методом осаждения

СИНТЕЗ И АДСОРБЦИОННЫЕ СВОЙСТВА НАНОСТРУКТУРИРОВАННЫХ ПОРОШКОВ Mg(OH)2 И MgO

Magnesium oxide has found applications as adsorbent, catalyst and ideutifier of the contamination of chemicals and toxic substances in the processes of water and gases purification. In this work, mesoporous magnesium hydroxide and oxide were synthesized from water solutions by easy and cheap wet chemistry method. Crystal structure, particle size distribution and adsorption properties of the synthesized powders were studied. Obtained powders of Mg(OH)2 and MgO showed sufficiently high total pore volume – 0.737 and 1.038 cm3 /g, respectively, which opens an opportunity to use them as nanoreactors for the synthesis of isolated nanosized particles and multidirection catalysts. Оксид магния находит широкое применение в качестве адсорбента, катализатора, идентификатора загрязняющих химических и токсических веществ, в процессах водо- и газоочистки. В настоящей работе методом осаждения синтезированы мезопористые порошки гидроксида и оксида магния, изучена их кристаллическая структура, микроструктура, гранулометрический состав и адсорбционные свойства. Полученные порошки Mg(OH)2 и MgO продемонстрировали высокие значения общего объема пор – 0,737 и 1,038 см3 /г соответственно, что открывает широкие возможности их использования в качестве нанореакторов для синтеза наноразмерных изолированных частиц и создания на их основе полимаршрутных катализаторов.

Solid state synthesis, structure and transport properties of compositions in the CaRu1−xTixO3CaRu_{1-x}Ti_{x}O_{3} system

DoubleBperovskite-type CaRu1−xTixO3−ıseries withx=0,0.1,0.2...0.9, 1.0 were synthesized in air by solidstate reactions from simple ruthenium and titanium oxides and CaCO3. Crystal structures of CaRu1−xTixO3samples have been refined in space groupPnma(GdFeO3-type of structure) assuming statistical distri-bution of Ru and Ti species over the octahedral sites. Electrical conductivity and thermal expansion wereinvestigated att= 20–1000◦C andpO2= 1–21000 Pa. Apart from CaRuO3with a combined p-/n-type con-ductivity depending on temperature andpO2, all other compositions are n-type semiconductors. Theconductivity of CaRuO3decreases with increasing temperature (metal-type). The Ti-containing compo-sitions withx= 0.1–0.2 change their conductivity dependence from metal-type at relatively low oxygenpartial pressures (pO2) to semi-conducting-type at relatively high ones. The materials withx> 0.2 havethe semi-conducting-type dependence at all investigatedpO2. Disproportionation of Ru4+into Ru3+andRu5+cations is considered for explanation of the conductivity dependences on temperature andpO2.The investigated compositions show high catalytic activity for propene oxidation and no activity for NO2reduction