Rutile decomposition by sulfuric acid, including the formation of two salts, Ti(SO4)2/TiOSO4, is thermodynamically modelled. It is shown that TiO2 can spontaneously dissolve in H2SO4 solutions. ...However, titania is considered as an inert (ballast) phase component of titanium-containing raw materials due to the decelerated separate nature of such chemical transformations. It is concluded that the hampered related kinetics of dissolution can be attributed to the lability of Ti(IV) cations/the specific engineered features of the hierarchical crystalline structure. It is suggested that the breaking of Ti–O–Ti bonds without additional mechanical strains in crystal lattice geometry becomes more advantageous when smaller negative anions/fluoride ions can be used. The analysis of sulfate-fluoride extraction leaching of titanium confirmed that a decrease in the Gibbs energy in the presence of F occurs. It is indicated by kinetic research studies that the addition of corrosive sodium reagent (NaF) reduces the activation by 45 kJ/mol, which results in intensification. A mechanism is proposed for the interactions involving the Ti–O–Ti cleavage on the surface/the H2SO4-induced Ti dioxide degradation on the sites of defects. Moreover, F acts as a homogeneous/heterogeneous bifunctional catalyst.
The crack propagation stability of chevron notched specimens during bending test was discussed on the basis of the dimensionless equilibrium Gibbs free energy diagram of elastic fracture system ...proposed by Sakai. The free energy diagram was also used for designing a new type of crack stabilizer which provides reliable and stable fracture of brittle ceramics in bending. A pair of elastic rectangular bend-bars were arranged on both sides and parallel to a bend-bar chevron notched SiC specimen as a crack stabilizer. Thus the stable fracture of the specimen was achieved by the simultaneous loading on both the specimen and the stabilizer arranged in this way.
The crack growth stability condition of brittle materials was considered using an equilibrium Gibbs free energy diagram, where the universal relationship of the dimensionless load and dimensionless ...displacement was utilized to calculate the Gibbs free energy of elastic fracture systems. The free energy diagram was then applied to a crack stabilizer which is specially designed for measuring the R-curve behavior of brittle ceramics showing unstable fracture. Some experimental R-curves of polycrystalline ceramics were measured by the use of the stabilizer. 26 ref.--AA
The crack growth stability condition of brittle materials was considered using an equilibrium Gibbs free energy diagram, where the universal relationship of the dimensionless load and dimensionless ...displacement was utilized to calculate the Gibbs free energy of elastic fracture systems. The free energy diagram was then applied to a crack stabilizer which is specially designed for measuring the R-curve behavior of brittle ceramics showing unstable fracture. Some experimental R-curves of polycrystalline ceramics were measured by the use of the stabilizer.
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