Modeling the Tensile Strengths of Nickel-Based Superalloys at a Wide Range of Isothermal Exposures by Artificial Neural Networks

The nickel-based superalloys are unique high-temperature materials that are applied in gas-turbine engine manufacturing. The superalloys are compositions with complex doping. The master mechanical property of the alloys is the heat resistance, which is depicted by the values of the tensile strength after long isothermal exposures. However, for each superalloy, only certain temperature-time exposure parameters are known. The availability of information on the properties in the entire range of temperatures and holdings would significantly expand the possibilities of the superalloys applications. We have applied the artificial neural network to predict the missing tensile strength values for superalloys based on the chemical composition and the known tensile test conditions. The additional data preprocessing and the bootstrap have improved the model performance. A comparison of the modeled and the real experimental data has shown their convergence. The model verification has been carried out on the set of 10 common cast superalloys.

The Influence of Complex Doping on Kinetics of Decomposition and Thermal Stability of Mg-Based Mechanical Alloys

Mechanical alloys (MАs) were synthesized by the method of reactive mechanical alloying. At a hydrogen pressure of 0.1 MPa, with the use of thermal desorption spectroscopy, the thermal stability, the kinetics of hydrogen desorption from the hydride phase MgH2 of the obtained MAs were studied. It has been established that the complex doping by of Fe, Si, Ti, leads to a significant improvement in the of hydrogen desorption from the hydride phase MgH2 of MA synthesized by the RMA. Hydrogen capacity CH of MА after reactive grinding for 20 h. was found to be equal to 5.7 % wt. Due to this alloying, the decrease in the thermodynamic stability of MgH2 is not established. The tested materials showed a high potential as hydrogen storage alloys especially for stationary application.

Silver Doping Mechanism in Bioceramics—From Ag+: Doped HAp to Ag°/BCP Nanocomposite

The results presented in this paper, based on the powder X-ray diffraction technique followed by Rietveld analyses, are devoted to the mechanism of silver incorporation in biphasic calcium phosphates. Results were confirmed by SEM observation. Samples were synthesized via the sol-gel route, followed by heat treatments. Two incorporation sites were highlighted: Ca2+ replacement by Ag+ into the calcium phosphates (HAp: hydroxyapatite and β-TCP: tricalcium phosphate), and the other as metallic silver Ag° nanoparticles (formed by autogenous reduction). The samples obtained were thus nanocomposites, written Ag°/BCP, composed of closely-mixed Ag° particles of about 100 nm at 400 °C (which became micrometric upon heating) and calcium phosphates, themselves substituted by Ag+ cations. Between 400 °C and 700 °C the cationic silver part was mainly located in the HAp phase of the composition Ca10-xAgx(PO4)6(OH)2-x (written Ag+: HAp). From 600 °C silver cations migrated to β-TCP to form the definite compound Ca10Ag(PO4)7 (written Ag+: TCP). Due to the melting point of Ag°, the doping element completely left our sample at temperatures above 1000 °C. In order to correctly understand the biological behavior of such material, which is potentially interesting for biomaterial applications, its complex doping mechanism should be taken into consideration for subsequent cytotoxic and bacteriologic studies.

Ammonia-Responsive Luminescence of Ln3+-β-diketonate Complex Encapsulated within Zeolite Y

Assembling Ln3+(HPBAn) (Ln = Eu or Tb, HPBA = N-(2-pyridinyl)benzoylacetamide) in the cavities of zeolite Y (ZY) via the “ship-in-a-bottle” strategy leads to the formation of novel luminescent composite, Ln(HPBAn)@ZY, whose luminescence can be easily modulated by ammonia on the basis of the energy level variation of HPBA after deprotonation process. Additionally the bimetallic complex doping sample, Eu0.5Tb0.5(HPBAn)@ZY, show great potential as self-referencing luminescent sensor for detecting low ammonia concentration of 10−12–0.25 wt%.

Mechanical alloys Mg-Me (Me: Ti, Fe, Ni, Al) & Mg-Me1-Me2(Ме1:Al, Me2: Ti, Fe, Ni) with low resistance and improved kinetics of hydrogenation/dehydrogenation for hydrogen storage applications

Changes in MgH2 decomposition kinetics were investigated in dependence on complex doping of MgH2 by Al, Ti, Ni, and Fe. Reactive mechanochemical alloying method (RMA) was applied in the temperature descending regime. It was found that addition of Al+Ni+Ti, Al+Ti, Fe+Ti (see below) and Al+Fe elements combinations led to a lower thermal stability and, consequently, to a lowering of the temperature of hydrogen desorption onset. Whereas desorption began at temperature of 320 °C from the pure MgH2, the aditions of Al, Ni, Ti and Fe lowered the start of the desorption down to 250°C (at hydrogen pressure 0.1 MPa in the reactor). Very fast desorption kineticsprecize at 300 0C and PH 2= 0.1 MPa were observed for Mg+Me mixture in comparison with the pure Mg. Sorption capacity of investigated mechanically-alloyed composites varied from 5 to 6.5 wt. % H2. The tested materials showed a high potential as hydrogen storage alloys especially for stationary application.