Microstructural influence of the thermal behavior of arc deposited TiAlN coatings with high aluminum content

The influence of the microstructure on the thermal behavior of cathodic arc deposited TiAlN coatings was studied as a function of isothermal annealing. Two compositionally similar but structurally different coatings were compared, a Ti0\ub734Al0\ub766N0.96 coating with a fine-grain structure consisting of a mixture of cubic (c) and hexagonal (h) phases, and a Ti0\ub740Al0\ub760N0.94 coating with a coarse-grain structure of cubic phase. By in situ wide-angle synchrotron x-ray scattering, spinodal decomposition was confirmed in both coatings. The increased amount of internal interfaces lowered the decomposition temperature by 50 \ub0C for the dual-phase coating. During the subsequent isothermal anneal at 1000 \ub0C, a transformation from c-AlN to h-AlN took place in both coatings. After 50 min of isothermal annealing, atom probe tomography detected small amounts of Al (∼2 at.%) in the c-TiN rich domains and small amounts of Ti (∼1 at.%) in the h-AlN rich domains of the coarse-grained single-phase Ti0\ub740Al0\ub760N0.94 coating. Similarly, at the same conditions, the fine-grained dual-phase Ti0\ub734Al0\ub766N0.96 coating exhibits a higher Al content (∼5 at.%) in the c-TiN rich domains and higher Ti content (∼15 at.%) in the h-AlN rich domains. The study shows that the thermal stability of TiAlN is affected by the microstructure and that it can be used to tune the reaction pathway of decomposition favorably

Hot carrier relaxation in CdTe via phonon-plasmon modes.

Carrier and lattice dynamics of laser excited CdTe was studied by time-resolved reflectivity for excitation fluences spanning about three orders of magnitude from 0.064 to 6.14 mJ/cm2. At fluences below 1 mJ/cm2 the transient reflectivity is dominated by the dynamics of hybrid phonon-plasmon modes. At fluences above 1 mJ/cm2 the time-dependent reflectivity curves show a complex interplay between band-gap renormalization, band filling, carrier dynamics and recombination. A framework that accounts for such complex dynamics is presented and used to model the time-dependent reflectivity data. This model suggests that the excess energy of the laser-excited hot carriers is reduced much more efficiently by emitting hybrid phonon-plasmon modes rather than bare longitudinal optical phonons

Effects of decomposition route and microstructure on h-AlN formation rate in TiCrAlN alloys

The phase evolution of cubic (c), solid solution TixCr-0.37Al1-0.37-x N alloys with x = 0.03 and 0.16, and the kinetics of the hexagonal (h)-AlN formation are studied via in situ wide angle x-ray scattering experiments during high temperature (1000-1150 degrees C) annealing. Spinodal decomposition was observed in Ti0.16Cr0.36Al0.48N while Ti0.03Cr0.38Al0.59N decomposes through nucleation and growth of h-AlN, c-TiN and c-CrAlN. h-AlN is formed from c-CrAlN domains in both cases and the formation rate of h-AlN depends on the stability of the c-CrAlN domains. In Ti0.16Cr0.36Al0.48N, the c-CrAlN domains are stabilized by crystallographic coherency with the surrounding c-TiCrN in a microstructure originating from spinodal decomposition. This results in lower formation rates of h-AlN for this composition. These differences are reflected in higher activation energy for h-AlN formation in Ti0.16Cr0.36Al0.48N compared to Ti0.03Cr0.38Al0.59N. It also points out different stabilities of the intermediate phase c-CrAlN during phase decomposition of TiCrAlN alloys. Additional contributions to the low activation energy for formation of h-AlN in Ti0.03Cr0.38Al0.59N stems from precipitation at grain boundaries. (C) 2016 Elsevier B.V. All rights reserved.Funding Agencies|EUs Erasmus-Mundus graduate school in Material Science and Engineering (DocMASE); Swedish Research Council VR [621- 2012-4401]; Rontgen-Angstrom Cluster grant [VR 2011-6505]; Swedish Foundation for Strategic Research, SSF [RMA08-0069]; Swedish government strategic research area grant AFM - SFO MatLiU [2009-00971]; VINNOVA (M - Era.net project) [2013-02355]</p

Effects of decomposition route and microstructure on h-AlN formation rate in TiCrAlN alloys

The phase evolution of cubic (c), solid solution Ti$_x$Cr$_{~0.37}$Al$_{1-0.37-x}$N alloys with x ¼ 0.03 and 0.16, and thekinetics of the hexagonal (h)-AlN formation are studied via in situ wide angle x-ray scattering experimentsduring high temperature (1000e1150 C) annealing. Spinodal decomposition was observed inTi$_{0.16}$Cr$_{0.36}$Al$_{0.48}$N while Ti$_{0.03}$Cr$_{0.38}$Al$_{0.59}$N decomposes through nucleation and growth of h-AlN, c-TiNand c-CrAlN. h-AlN is formed from c-CrAlN domains in both cases and the formation rate of h-AlN dependson the stability of the c-CrAlN domains. In Ti$_{0.16}$Cr$_{0.36}$Al$_{0.48}$N, the c-CrAlN domains are stabilized bycrystallographic coherency with the surrounding c-TiCrN in a microstructure originating from spinodaldecomposition. This results in lower formation rates of h-AlN for this composition. These differences arereflected in higher activation energy for h-AlN formation in Ti$_{0.16}$Cr$_{0.36}$Al$_{0.48}$N compared toTi$_{0.03}$Cr$_{0.38}$Al$_{0.59}$N. It also points out different stabilities of the intermediate phase c-CrAlN during phasedecomposition of TiCrAlN alloys. Additional contributions to the low activation energy for formation ofh-AlN in Ti$_{0.03}$Cr$_{0.38}$Al$_{0.59}$N stems from precipitation at grain boundaries

Microstructural influence of the thermal behavior of arc deposited TiAlN coatings with high aluminum content

studied as a function of isothermal annealing. Two compositionally similar but structurally differentcoatings were compared, a Ti$_{0.34}$Al$_{0.66}$N$_{0.96}$ coating with a fine-grain structure consisting of a mixture ofcubic (c) and hexagonal (h) phases, and a Ti$_{0.40}$Al$_{0.60}$N$_{0.94}$ coating with a coarse-grain structure of cubicphase. By in situ wide-angle synchrotron x-ray scattering, spinodal decomposition was confirmed in bothcoatings. The increased amount of internal interfaces lowered the decomposition temperature by 50 Cfor the dual-phase coating. During the subsequent isothermal anneal at 1000 C, a transformation from c-AlN to h-AlN took place in both coatings. After 50 min of isothermal annealing, atom probe tomographydetected small amounts of Al (~2 at.%) in the c-TiN rich domains and small amounts of Ti (~1 at.%) in theh-AlN rich domains of the coarse-grained single-phase Ti$_{0.40}$Al$_{0.60}$N$_{0.94}$ coating. Similarly, at the sameconditions, the fine-grained dual-phase Ti$_{0.34}$Al$_{0.66}$N$_{0.96}$ coating exhibits a higher Al content (~5 at.%) inthe c-TiN rich domains and higher Ti content (~15 at.%) in the h-AlN rich domains. The study shows thatthe thermal stability of TiAlN is affected by the microstructure and that it can be used to tune the reactionpathway of decomposition favorably