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1. Tailoring critical Al concentration to form external Al 2 O 3 scale on Ni–Al alloys by computational approach

   https://doi.org/10.1111/jace.18707  

   Ross, Austin ; Shang, Shun‐Li ; Fang, Huazhi ; Lindwall, Greta ; Liu, Xuan L. ; Zhao, Wei ; Gleeson, Brian ; Gao, Michael C. ; Liu, Zi‐Kui ( September 2022 , Journal of the American Ceramic Society)

   Nickel (Ni)‐based superalloys for high‐temperature applications are often designed to form a continuous and slow‐growing oxide scale by adding Al and Cr and other beneficial elements. In the present work, the critical Al concentration in Ni–Al alloys needed to establish an α‐Al₂O₃scale in contrast to internal oxide formation is predicted as a function of temperature by means of the CALPHAD approach coupled with models in the literature, which account for the thermodynamics and kinetics of oxidation. The present thermodynamic remodeling of the Ni–O system results in a better agreement with experimental data of oxygen solubility in Ni at high temperatures. The oxygen solubility is combined with kinetic parameters to determine oxygen permeability in Ni, and the critical Al concentration needed to establish an α‐Al₂O₃scale at a given exposure temperature. Good agreement is found with available experimental data for both oxygen permeability and critical Al concentration, indicating the capacity of the CALPHAD approach to tailor oxidation resistance for materials of interest using thermodynamic and kinetic knowledge.

    

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2. Band alignment of B 0.14 Al 0.86 N/Al 0.7 Ga 0.3 N heterojunction

   https://doi.org/10.1063/1.4999249  

   Sun, Haiding ; Park, Young Jae ; Li, Kuang-Hui ; Torres Castanedo, C. G. ; Alowayed, Abdulmohsen ; Detchprohm, Theeradetch ; Dupuis, Russell D. ; Li, Xiaohang ( September 2017 , Applied Physics Letters)
3. Realization of an Al≡Al Triple Bond in the Gas‐Phase Na 3 Al 2 − Cluster via Double Electronic Transmutation

   https://doi.org/10.1002/anie.201806917  

   Zhang, Xinxing ; Popov, Ivan A. ; Lundell, Katie A. ; Wang, Haopeng ; Mu, Chaonan ; Wang, Wei ; Schnöckel, Hansgeorg ; Boldyrev, Alexander I. ; Bowen, Kit H. ( September 2018 , Angewandte Chemie International Edition)

   The discovery of homodinuclear multiple bonds composed of Group 13 elements represents one of the most challenging frontiers in modern chemistry. A classical triple bond such as N≡N and HC≡CH contains one σ bond and two π bonds constructed from the p orbitals perpendicular to the σ bond. However, the traditional textbook triple bond between two Al atoms has remained elusive. Here we report an Al≡Al triple bond in the designer Na₃Al₂⁻cluster predicted in silico, which was subsequently generated by pulsed arc discharge followed by mass spectrometry and photoelectron spectroscopy characterizations. Being effectively Al²⁻due to the electron donation from Na, the Al atoms in Na₃Al₂⁻undergo a double electronic transmutation into Group 15 elements, thus the Al²⁻≡Al²⁻kernel mimics the P≡P and N≡N molecules. We anticipate this work will stimulate more endeavors in discovering materials using Al²⁻≡Al²⁻as a building block in the gas phase and in the solid state.

    

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4. Realization of an Al≡Al Triple Bond in the Gas‐Phase Na 3 Al 2 − Cluster via Double Electronic Transmutation

   https://doi.org/10.1002/ange.201806917  

   Zhang, Xinxing ; Popov, Ivan A. ; Lundell, Katie A. ; Wang, Haopeng ; Mu, Chaonan ; Wang, Wei ; Schnöckel, Hansgeorg ; Boldyrev, Alexander I. ; Bowen, Kit H. ( September 2018 , Angewandte Chemie)

   The discovery of homodinuclear multiple bonds composed of Group 13 elements represents one of the most challenging frontiers in modern chemistry. A classical triple bond such as N≡N and HC≡CH contains one σ bond and two π bonds constructed from the p orbitals perpendicular to the σ bond. However, the traditional textbook triple bond between two Al atoms has remained elusive. Here we report an Al≡Al triple bond in the designer Na₃Al₂⁻cluster predicted in silico, which was subsequently generated by pulsed arc discharge followed by mass spectrometry and photoelectron spectroscopy characterizations. Being effectively Al²⁻due to the electron donation from Na, the Al atoms in Na₃Al₂⁻undergo a double electronic transmutation into Group 15 elements, thus the Al²⁻≡Al²⁻kernel mimics the P≡P and N≡N molecules. We anticipate this work will stimulate more endeavors in discovering materials using Al²⁻≡Al²⁻as a building block in the gas phase and in the solid state.

    

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5. Band Alignment of Al 2 O 3 on α-(Al x Ga 1-x ) 2 O 3

   https://doi.org/10.1149/2162-8777/ac546f  

   Xia, Xinyi ; Al-Mamun, Nahid Sultan ; Fares, Chaker ; Haque, Aman ; Ren, Fan ; Hassa, Anna ; von Wenckstern, Holger ; Grundmann, Marius ; Pearton, S. J. ( February 2022 , ECS Journal of Solid State Science and Technology)

   X Ray Photoelectron Spectroscopy was used to measure valence band offsets for Al 2 O 3 deposited by Atomic Layer Deposition on α -(Al x Ga 1-x ) 2 O 3 alloys over a wide range of Al contents, x, from 0.26–0.74, corresponding to a bandgap range from 5.8–7 eV. These alloys were grown by Pulsed Laser Deposition. The band alignments were type I (nested) at x <0.5, with valence band offsets 0.13 eV for x = 0.26 and x = 0.46. At higher Al contents, the band alignment was a staggered alignment, with valence band offsets of − 0.07 eV for x = 0.58 and −0.17 for x = 0.74, ie. negative valence band offsets in both cases. The conduction band offsets are also small at these high Al contents, being only 0.07 eV at x = 0.74. The wide bandgap of the α -(Al x Ga 1-x ) 2 O 3 alloys makes it difficult to find dielectrics with nested band alignments over the entire composition range. 

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