|
|
Heterogeneous bipolar membrane and the influence of composition on its properties
Kvasničková, Lucie ; Válek, Robert (referee) ; Neděla, David (advisor)
This work is focused on the preparation of heterogeneous bipolar membranes and studies the influence of different composition on mechanical and physical properties. The main feature of this approach is optimalization of composition following gained data. Theoretical part contains new piece of knowledge in the field of heterogeneous bipolar membranes. Experimental part engages preparation of bipolar ion-exchange membranes on one face cation-selective and on the other one anion-selective. In this case are used variant types of polyethylene.
|
|
|
Heterogeneous bipolar membrane and the influence of composition on its properties
Kvasničková, Lucie ; Válek, Robert (referee) ; Neděla, David (advisor)
This work is focused on the preparation of heterogeneous bipolar membranes and studies the influence of different composition on mechanical and physical properties. The main feature of this approach is optimalization of composition following gained data. Theoretical part contains new piece of knowledge in the field of heterogeneous bipolar membranes. Experimental part engages preparation of bipolar ion-exchange membranes on one face cation-selective and on the other one anion-selective. In this case are used variant types of polyethylene.
|
|
| |
|
|
Metallography of gamma TiAl intermetallic casts
Dlouhý, Antonín ; Válek, Robert ; Svoboda, Milan ; Zemčík, L.
A quantitative metallographic study was performed which focussed on the cast versions of advanced intermetallic alloys based on gamma TiAl phase. Specimens cut out of cast rods and turbine blades exhibited two pronounced microstructural characteristics: (i) a preferential orientation of lamellae in columnar grains below the cast surface and (ii) increasing fraction of equiaxed grains towards the central part of the casts. The relation between the particular microstrucrure and creep strength has been documented.
|
|
| |
|
|
Microstructure and Anisotropy of Creep in Ti-46Al-2W-0.5Si Castings
Dlouhý, Antonín ; Kuchařová, Květa ; Svoboda, Milan ; Válek, Robert ; Březina, Josef
The present study investigates microstructure and creep behaviour of the cast alloy Ti-46A1-2W-0.5Si (at-%) at temperatures 700, 750 and 800°C and applied stresses between 250-420 MPa. Solidification of the alloy during precision casting is associated with two processes: (i) the growth of the [0001].alpha. oriented columnar grains from the mould wall into the cast interior and (ii) the enrichment of the central part of the cast with aluminium. The first process results in a fully lamellar microstructure where lamellae are preferentially oriented parallel to the cast surface. The second process contributes to the development of the duplex microstructure in the central part of the cast. It is shown that distinct microstructural types in different regions of the cast result in different creep strengths. Specimens taken from inside of the cast and oriented parallel to the cast bar axis exhibited the lowest creep strength while similarly oriented specimens cut from the fully lamellar region near the cast surface were the strongest. The third type of the creep specimens cut out of the central region of the cast and oriented perpendicular to the cast bar axis showed the intermediate creep strength. The observed variations of the creep strength are associated with the preferential orientation of the lamellas and with the fraction of equiaxed .gamma.-grains in the duplex regions of the cast.
|
guest ::
RSS feed.