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Physical properties of the intermetallic catalyst compound ZnPd

Abstract

Kataliza se uporablja v znanosti in tehnologiji za spreminjanje poteka kemijskih reakcij preko znižanja aktivacijske energije, ki je potrebna za reakcijo. Najpreprostejši katalizator dobimo, če vzamemo kovinski element brez podlage. Slabost take izbire je zelo omejeno število elementov, ki so katalitsko aktivni za dano kemijsko reakcijo. Alternativni materiali za heterogeno katalizo so strukturno urejene intermetalne spojine. Gre za spojine iz dveh ali več kovinskih elementov, ki se nahajajo levo ali v okolici Zintlove črte v periodnem sistemu elementov. Njihova struktura je popolnoma ali delno urejena in se razlikuje od strukture elementov, ki tvorijo spojino. Stabilnost intermetalnih spojin med kemijsko reakcijo je povezana z njihovo elektronsko in geometrijsko strukturo. Prednost uporabe intermetalnih spojin za katalizo je možnost izbire elektronske in geometrijske strukture. Intermetalne spojine lahko razpadejo pred ali med katalizo, tako da iz njih nastane katalizator z veliko aktivno površino. Intermetalne spojine lahko nastanejo tudi med kemijsko reakcijo pri reakciji med aktivno kovino in podlago ali med različnimi materiali s podlago. V izogib tem težavam je bil nedavno sprejet pristop, da se kot stabilne katalizatorje brez podlage uporablja intermetalne spojine z urejeno kristalno strukturo. V Magistrskem delu smo opravili karakterizacijo vzorca ZnPd s pomočjo mikroskopije SEM, ki je bila izvedena na Kemijskem institutu v Ljubljani. Ostale meritve so bile izvedene na Institutu »Jožef Stefan« v Ljubljani. Z napravo PPMS (angl. Physical Property Measurement System) proizvajalca Quantum Design smo izmerili fizikalne lastnosti ZnPd. Pri določanju magnetnega stanja vzorca pa smo uporabili magnetometer MPMS (angl. Magnetic Property Measurement System) XL-5 proizvajalca Quantum Design. V Magistrskem delu smo prav tako dopolnili nedavne študije fizikalnih lastnostih intermetalnih katalizatorjev GaPd in InPd.Catalysis is used in science and technology to change the path of chemical reactions by modifying their activation energies. The simplest catalyst is an unsupported metal element. The downside of such choice is a very limited number of elements that are catalytically active for a specific chemical reaction. Alternative materials for heterogeneous catalysis are structurally ordered intermetallic alloys. Intermetallic alloys are composed of two or more metallic elements. The completely or partially ordered structure of intermetallic alloys is different form the structure of individual elements that form the alloy. Stability of intermetallic alloys during chemical reactions depends on their electronic and geometrical structure. The great advantage of intermetallic alloys is the possibility to choose their electronic and geometric structure before use. Intermetallic alloys can decompose before or during catalysis. They form catalysts with large active surfaces. Intermetallic alloys can also form during the chemical reaction between active metal and supporting material or between different supporting materials. To avoid difficulties, an approach to use intermetallic alloys with ordered crystal structure as stable unsupported catalysts has recently been accepted. In this Master\u27s thesis, we characterized a ZnPd sample using SEM microscope at the Chemistry Institute in Ljubljana. Physical properties of the sample were measured at the Jožef Stefan Institute in Ljubljana. With the Physical Property Measurement System (PPMS) we measured specific heat and electrical resistivity. To determine the magnetic state of the sample we used the Magnetic Property Measurement System (MPMS XL-5). We have also supplemented recent studies of physical properties of intermetallic catalysts GaPd and InPd

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