Effect of electronic structure on phase equilibria in the AlB2-ScB2-YB2-ZrB2-HfB2-NbB2- TaB2 system

Compositions in the AlB2-ScB2-YB2-ZrB2-HfB2-NbB2-TaB2 system were selected to determine the effect of electronic structure on phase equilibria and solid solubility. The Group IVB diborides have the highest stability considering a melting point criterion (eg., ZrB2 with 10 valence electrons per unit cell, or 10 e-/uc) and three systems were investigated to characterize phase equilibria at or near this optimum valence electron sum. The materials were synthesized by hot-pressing diboride powder mixtures at 1750°C followed by heat-treatments at 1900 and 2000°C. The compositions in the system xScB2-(1-x)TaB2 (varying from 9 to 11 e-/uc, respectively), with a metal atom radius difference of 7.4%, exhibited complete solid solubility that could be attributed to the change of the net valence electron sum toward the optimum 10 e-/uc value. The xScB2-(1-x)ZrB2 system (varying from 9 to 10 e-/uc, respectively) was found to be quasi-binary, but exhibited insignificant solid solubility despite the metal atom radius of Sc being smaller than Zr by only 1.2%. The lack of solubility is attributed to an electronic structure based incompatibility. The system x(ZrB2)-(1-x)(0.5ScB2 - 0.5TaB2), with a valence electron sum of 10 e-/uc for all x, exhibited complete solid solubility. Very similar results were found for the YB2-ZrB2-TaB2 system, with the exception that significant solubility of ZrB2 in YB2 was observed. The unidirectional solubility is attributed to an electronic structure based stabilization of the YB2. The compatibilities observed for all compositions investigated indicate that ZrB2-ScB2-TaB2 and ZrB2-YB2-TaB2 are quasi-ternary systems. Additional 4, 5, and 6 component diboride systems with an average valence sum of 10 e-/fu were also investigated in the AlB2-ScB2-YB2-ZrB2-HfB2-NbB2-TaB2 system, and many formed solid solutions. The results confirm the significance of electronic structure for phase equilibria and solid solubilities for these diborides. The solid solutions also provide a basis for further investigations as high entropy boride system

Oxidation kinetics of sub-stoichiometric ZrCX via furnace testing to 2500˚C / 1 atm air

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Elementary games for preschool children in physical education

Igra je vrlo rado prihvaćena kod djece zato što putem nje dijete zadovoljava svoje potrebe za kretanjem i za društvenim životom. Promatranjem djece i njihove velike radosti dok se u igri koriste osnovnim pokretima izrađen je veliki broj elementarnih igara prilagođen satovima tjelesne i zdravstvene kulture. Koristeći razne metode rada, poput metode demonstracije ili imitacije, odgojitelj se približava djetetu i njegovom načinu razmišljanja. Na satu tjelesne i zdravstvene kulture odgojitelj bira koja će se elementarna igra koristiti, ovisno o cilju koji se misli postići igrom, kao i zadatka koji je potrebno realizirati tom prilikom. Cilj elementarnih igara je prvenstveno razvoj i održanje motoričkih i funkcionalnih sposobnosti. Prilikom izbora igara potrebno je paziti da su primijenjene dječjem uzrastu i antropološkim karakteristikama djece. Također djeci treba dopustiti da igru sama nadograde, da izmisle nešto novo, ali prije svega da uživaju u njoj.Games are very gladly accepted by children because through them a child satisfies his or her need for movement and social life. Looking at children and their great happiness while using elementary movements in games has led the creation of a large number of elementary games adequate for physical education lessons. Using different working methods of demonstration or imitation, the preschool teacher approaches the child and his or her way of thinking. During the physical education lessons, the preschool teacher chooses which elementary game to use depending on the aim to be achieved by it and the tasks to be realized on the occasion. The elementary games' aim is primarily to develop and maintain the motor and functional abilities. When choosing the games, it is important to pay attention for them to be adequate to the children's age and their anthropological characteristics. Children should also be given the opportunity to upgrade the games themselves, to make up something new, and, first of all, to enjoy in them

Elementary games for preschool children in physical education

Igra je vrlo rado prihvaćena kod djece zato što putem nje dijete zadovoljava svoje potrebe za kretanjem i za društvenim životom. Promatranjem djece i njihove velike radosti dok se u igri koriste osnovnim pokretima izrađen je veliki broj elementarnih igara prilagođen satovima tjelesne i zdravstvene kulture. Koristeći razne metode rada, poput metode demonstracije ili imitacije, odgojitelj se približava djetetu i njegovom načinu razmišljanja. Na satu tjelesne i zdravstvene kulture odgojitelj bira koja će se elementarna igra koristiti, ovisno o cilju koji se misli postići igrom, kao i zadatka koji je potrebno realizirati tom prilikom. Cilj elementarnih igara je prvenstveno razvoj i održanje motoričkih i funkcionalnih sposobnosti. Prilikom izbora igara potrebno je paziti da su primijenjene dječjem uzrastu i antropološkim karakteristikama djece. Također djeci treba dopustiti da igru sama nadograde, da izmisle nešto novo, ali prije svega da uživaju u njoj.Games are very gladly accepted by children because through them a child satisfies his or her need for movement and social life. Looking at children and their great happiness while using elementary movements in games has led the creation of a large number of elementary games adequate for physical education lessons. Using different working methods of demonstration or imitation, the preschool teacher approaches the child and his or her way of thinking. During the physical education lessons, the preschool teacher chooses which elementary game to use depending on the aim to be achieved by it and the tasks to be realized on the occasion. The elementary games' aim is primarily to develop and maintain the motor and functional abilities. When choosing the games, it is important to pay attention for them to be adequate to the children's age and their anthropological characteristics. Children should also be given the opportunity to upgrade the games themselves, to make up something new, and, first of all, to enjoy in them

Zirconia Transport by Liquid Convection during Oxidation of Zirconium Diboride–Silicon Carbide

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65610/1/j.1551-2916.2007.02142.x.pd