More Like this

1. Nickel‐containing magnetoceramics from water vapor‐assisted pyrolysis of polysiloxane and nickel 2,4‐pentanedionate

   https://doi.org/10.1111/jace.16738  

   Yang, Ni; Gao, Min; Li, Jiefang; Lu, Kathy (August 2019, Journal of the American Ceramic Society)

   Abstract In this study, novel ferromagnetic Ni‐containing silicon oxycarbide (SiOC–Ni) was successfully fabricated from a base polysiloxane (PSO) with the addition of nickel 2,4‐pentanedionate. The resultant SiOC–Ni nanocomposite consists of in situ formed Ni nanocrystallites with a small amount of NiO uniformly dispersed in the amorphous SiOC matrix, and the corresponding nanocrystallite size increases with the increase of the pyrolysis temperature. The formation of nickel silicides (Ni_xSi_y) is completely suppressed by the effect of water vapor during the pyrolysis. The fundamental phase evolution process and mechanisms are explained. In an argon atmosphere, the SiOC–Ni materials pyrolyzed at 900°C are stable up to 1000°C with less than 6 wt% weight loss; they exhibit desirable electrical conductivity up to ~900°C with the highest electrical conductivity at ~247 S/m. This series of SiOC–Ni materials also demonstrates exciting ferromagnetic behaviors. Their new semiconducting behavior with soft ferromagnetism presents promising application potentials for magnetic sensors, transformers, actuators, etc. 

   more » « less
2. Wide‐Bandgap Nickel Oxide with Tunable Acceptor Concentration for Multidimensional Power Devices

   https://doi.org/10.1002/aelm.202300662  

   Ma, Yunwei; Qin, Yuan; Porter, Matthew; Spencer, Joseph; Du, Zhonghao; Xiao, Ming; Wang, Boyan; Wang, Yifan; Jacobs, Alan_G; Wang, Han; et al (December 2023, Advanced Electronic Materials)

   Abstract Multidimensional power devices can achieve performance beyond conventional limits by deploying charge‐balanced p‐n junctions. A key obstacle to developing such devices in many wide‐bandgap (WBG) and ultra‐wide bandgap (UWBG) semiconductors is the difficulty of native p‐type doping. Here the WBG nickel oxide (NiO) as an alternative p‐type material is investigated. The acceptor concentration (N_A) in NiO is modulated by oxygen partial pressure during magnetron sputtering and characterized using a p‐n⁺heterojunction diode fabricated on gallium oxide (Ga₂O₃) substrate. Capacitance and breakdown measurements reveal a tunableN_Afrom < 10¹⁸ cm⁻³to 2×10¹⁸ cm⁻³with the practical breakdown field (E_B) of 3.8 to 6.3 MV cm⁻¹. ThisN_Arange allows for charge balance to n‐type region with reasonable process latitude, andE_Bis high enough to pair with many WBG and UWBG semiconductors. The extractedN_Ais then used to design a multidimensional Ga₂O₃diode with NiO field‐modulation structure. The diodes fabricated with two differentN_Aboth achieve 8000 V breakdown voltage and 4.7 MV cm⁻¹average electric field. This field is over three times higher than the best report in prior multi‐kilovolt lateral devices. These results show the promise of p‐type NiO for pushing the performance limits of power devices. 

   more » « less
3. Catalytic Ammonia Oxidation to Dinitrogen by a Nickel Complex

   https://doi.org/10.1002/anie.202213462  

   Stephens, David N.; Szilagyi, Robert K.; Roehling, Paige N.; Arulsamy, Navamoney; Mock, Michael T. (November 2022, Angewandte Chemie International Edition)

   Abstract We report a nickel complex for catalytic oxidation of ammonia to dinitrogen under ambient conditions. Using the aryloxyl radical 2,4,6‐tri‐tert‐butylphenoxyl (^tBu₃ArO⋅) as a H atom acceptor to cleave the N−H bond of a coordinated NH₃ligand up to 56 equiv of N₂per Ni center can be generated. Employing theN‐oxyl radical 2,2,6,6‐(tetramethylpiperidin‐1‐yl)oxyl (TEMPO⋅) as the H‐atom acceptor, up to 15 equiv of N₂per Ni center are formed. A bridging Ni‐hydrazine product identified by isotopic nitrogen (¹⁵N) studies and supported by computational models indicates the N−N bond forming step occurs by bimetallic homocoupling of two paramagnetic [Ni]−NH₂fragments. Ni‐mediated hydrazine disproportionation to N₂and NH₃completes the catalytic cycle. 

   more » « less
4. All‐Electric Nonassociative Learning in Nickel Oxide

   https://doi.org/10.1002/aisy.202200069  

   Mondal, Sandip; Zhang, Zhen; Islam, A_N_M_Nafiul; Andrawis, Robert; Gamage, Sampath; Aghamiri, Neda_Alsadat; Wang, Qi; Zhou, Hua; Rodolakis, Fanny; Tran, Richard; et al (September 2022, Advanced Intelligent Systems)

   Habituation and sensitization represent nonassociative learning mechanisms in both non‐neural and neural organisms. They are essential for a range of functions from survival to adaptation in dynamic environments. Design of hardware for neuroinspired computing strives to emulate such features driven by electric bias and can also be incorporated into neural network algorithms. Herein, cellular‐like learning in oxygen‐deficient NiO_xdevices is demonstrated. Both habituation learning and sensitization response can be achieved in a single device by simply controlling the magnitude of the electric field. Spontaneous memory relaxations and dynamic redistribution of oxygen vacancies under electric bias enable such learning behavior of NiO_xunder sequential training. These characteristics in simple device arrays are implemented to learn alphabets as well as demonstrate simulated algorithmic use cases in digit recognition. Transition metal oxides with carefully prepared defect concentrations can be highly sensitive to electronic structure perturbations under moderate electrical stimulus and serve as building blocks for next‐generation neuroinspired computing hardware. 

   more » « less
5. SN 2023zaw: An Ultrastripped, Nickel-poor Supernova from a Low-mass Progenitor

   https://doi.org/10.3847/2041-8213/ad527a  

   Das, Kaustav K; Fremling, Christoffer; Kasliwal, Mansi M; Schulze, Steve; Sollerman, Jesper; Karambelkar, Viraj; Rose, Sam; Anand, Shreya; Andreoni, Igor; Aubert, Marie; et al (June 2024, The Astrophysical Journal Letters)

   Abstract We present SN 2023zaw—a subluminous (M_r= −16.7 mag) and rapidly evolving supernova (t_1/2,r= 4.9 days), with the lowest nickel mass (≈0.002M_⊙) measured among all stripped-envelope supernovae discovered to date. The photospheric spectra are dominated by broad Heiand Ca near-infrared emission lines with velocities of ∼10,000−12,000 km s⁻¹. The late-time spectra show prominent narrow Heiemission lines at ∼1000 km s⁻¹, indicative of interaction with He-rich circumstellar material. SN 2023zaw is located in the spiral arm of a star-forming galaxy. We perform radiation-hydrodynamical and analytical modeling of the lightcurve by fitting with a combination of shock-cooling emission and nickel decay. The progenitor has a best-fit envelope mass of ≈0.2M_☉and an envelope radius of ≈50R_⊙. The extremely low nickel mass and low ejecta mass (≈0.5M_⊙) suggest an ultrastripped SN, which originates from a mass-losing low-mass He-star (zero-age main-sequence mass < 10M_⊙) in a close binary system. This is a channel to form double neutron star systems, whose merger is detectable with LIGO. SN 2023zaw underscores the existence of a previously undiscovered population of extremely low nickel mass (<0.005M_☉) stripped-envelope supernovae, which can be explored with deep and high-cadence transient surveys. 

   more » « less