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- 저자 : Tytko Darius (검색결과 2 건)
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Oxidation behavior of AlN/CrN multilayered hard coatings
Tytko Darius,Choi Pyuck-Pa,Raabe Dierk 나노기술연구협의회 2017 Nano Convergence Vol.4 No.15
We report on the oxidation behavior of AlN/CrN multilayers at 900 °C, deposited by radio frequency magnetron sputtering. It is shown that oxidation in this system is controlled by diffusion of Cr towards the surface and formation of Cr2O3. Cr diffusion is found to mainly occur along grain boundaries. Thus, coherent cubic AlN/CrN multilayer regions with coarse columnar grain structures are found to be oxidation resistant, whereas regions decomposed into hexagonal AlN/cubic CrN are prone to oxidation.
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Lapauw, Thomas,Tytko, Darius,Vanmeensel, Kim,Huang, Shuigen,Choi, Pyuck-Pa,Raabe, Dierk,Caspi, El’ad N.,Ozeri, Offir,to Baben, Moritz,Schneider, Jochen M.,Lambrinou, Konstantina,Vleugels, Jozef American Chemical Society 2016 Inorganic Chemistry Vol.55 No.11
<P>The solubility of zirconium (Zr) in the Nb<SUB>4</SUB>AlC<SUB>3</SUB> host lattice was investigated by combining the experimental synthesis of (Nb<SUB><I>x</I></SUB>, Zr<SUB>1–<I>x</I></SUB>)<SUB>4</SUB>AlC<SUB>3</SUB> solid solutions with density functional theory calculations. High-purity solid solutions were prepared by reactive hot pressing of NbH<SUB>0.89</SUB>, ZrH<SUB>2</SUB>, Al, and C starting powder mixtures. The crystal structure of the produced solid solutions was determined using X-ray and neutron diffraction. The limited Zr solubility (maximum of 18.5% of the Nb content in the host lattice) in Nb<SUB>4</SUB>AlC<SUB>3</SUB> observed experimentally is consistent with the calculated minimum in the energy of mixing. The lattice parameters and microstructure were evaluated over the entire solubility range, while the chemical composition of (Nb<SUB>0.85</SUB>, Zr<SUB>0.15</SUB>)<SUB>4</SUB>AlC<SUB>3</SUB> was mapped using atom probe tomography. The hardness, Young’s modulus, and fracture toughness at room temperature as well as the high-temperature flexural strength and E-modulus of (Nb<SUB>0.85</SUB>, Zr<SUB>0.15</SUB>)<SUB>4</SUB>AlC<SUB>3</SUB> were investigated and compared to those of pure Nb<SUB>4</SUB>AlC<SUB>3</SUB>. Quite remarkably, an appreciable increase in fracture toughness was observed from 6.6 ± 0.1 MPa/m<SUP>1/2</SUP> for pure Nb<SUB>4</SUB>AlC<SUB>3</SUB> to 10.1 ± 0.3 MPa/m<SUP>1/2</SUP> for the (Nb<SUB>0.85</SUB>, Zr<SUB>0.15</SUB>)<SUB>4</SUB>AlC<SUB>3</SUB> solid solution.</P><P>The solubility of Zr in nanolaminated (Nb<SUB>1−<I>x</I></SUB>, Zr<SUB><I>x</I></SUB>)<SUB>4</SUB>AlC<SUB>3</SUB> is investigated. Experimentally, a maximum at <I>x</I> = 18.5% is found, which is consistent with a minimum in the calculated energy of mixing at low Zr contents. The mechanical behavior of this solid solution shows a significant improvement in fracture toughness and temperature stability compared to those of Nb<SUB>4</SUB>AlC<SUB>3</SUB>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2016/inocaj.2016.55.issue-11/acs.inorgchem.6b00484/production/images/medium/ic-2016-00484u_0007.gif'></P>
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