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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on CaGaN by Materials Project

CaGaN crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one CaGaN sheet oriented in the (0, 0, 1) direction. Ca is bonded to five equivalent N atoms to form a mixture of corner and edge-sharing CaN5 square pyramids. There are one shorter (2.41 Å) and four longer (2.55 Å) Ca–N bond lengths. Ga is bonded in a single-bond geometry to one N atom. The Ga–N bond length is 1.86 Å. N is bonded to five equivalent Ca and one Ga atom to form a mixture of corner and edge-sharing NCa5Ga octahedra. The corner-sharing octahedral tilt angles are 8°.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Multiconfigurational Electronic Structure of Nickel Cross-Coupling Catalysts Revealed by X-ray Absorption Spectroscopy

Ni II 2,2'-bipyridine complexes are commonly invoked intermediates in metallaphotoredox cross-coupling reactions. Despite their ubiquity, design principles targeting improved catalytic performance remain underdetermined. A series of Ni( R bpy)( R 'Ar)Cl (R = MeOOC, t-Bu, R' = CH 3 , CF 3 ) complexes were proposed to have multiconfigurational electronic structures on the basis of multiconfigurational/multireference calculations, with significant mixing of Ni → bpy metal-to-ligand charge transfer (MLCT) configurations into the ground-state wave function. Here, Ni K-edge and L 2,3 -edge X-ray absorption spectroscopies provide experimental support for the highly covalent and multiconfigurational electronic structures of these complexes. The pre-edge intensity in the K-edge spectrum reflects highly covalent Ni–aryl bonding. The L 3 -edge spectral shape is dependent on ligand functionalization, and a feature reflecting the MLCT character is assigned using prior ab initio and new semiempirical calculations. The results suggest the push/pull effects of the aryl/bpy ligands moderate the changes in electron density on Ni during the multiredox cross-coupling reaction cycle.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Ultrafast population and structural dynamics of a Ni-bipyridine photoredox catalyst reveal a significant deactivation pathway

The ultrafast excited state pathways and dynamics of NiII-bipyridine complexes influence the yield of photochemical processes involved in their catalytic cross-coupling reactions. Here we present ultrafast Ni K x-ray emission spectroscopy (XES) and x-ray solution scattering (XSS) of a NiII-bipyridine aryl halide complex, [Ni(t-Bubpy)(o-tol)Br], to quantify the excited state population dynamics and structural changes of the pre-catalyst. Due to the local spin-sensitivity of XES, the population dynamics of metal-to-ligand charge transfer (MLCT) and metal-centered (MC) excited states is established. A rapid ground state recovery pathway is newly identified, representing a significant deactivation pathway during photocatalysis. Furthermore, the pseudotetrahedral structure of the long-lived MC excited state is unambiguously identified and refined by XSS. The results advance our understanding of the ultrafast relaxation mechanisms that impact the photocatalytic mechanism and yield for NiII-bipyridine aryl halide cross-coupling catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Light-Promoted C(sp 3 )–C(sp 3 ) Reductive Elimination from Dialkyl NiII Complexes

Ni-catalyzed cross-coupling is a powerful strategy to forge C(sp 3 )–C(sp 3 ) bonds. Typically, to do so requires overcoming a challenging C–C bond-forming reductive elimination, often enabled by the intermediacy of highly oxidized Ni species or outer-sphere processes. While direct C(sp 3 )–C(sp 3 ) reductive elimination from the Ni II base oxidation state is normally thermally inaccessible, light-activation provides an avenue to affect such transformations. Here, we investigate the mechanism of light-induced C(sp 3 )–C(sp 3 ) bond formation from dialkyl bipyridine Ni II complexes through a variety of organometallic, spectroscopic, and computational studies. Wavelength-dependent quantum yields, ligand electronics–reactivity relationships, excited-state lifetimes, computed barriers, and product distributions from crossover studies support a photolysis/radical rebound mechanism. Furthermore, this reactivity paradigm complements existing strategies in the literature to promote reductive elimination from Ni II , such as the use of destabilizing, sterically hindered ligands and reduction of electron density at Ni through the binding of electron-deficient olefins. Hence, we envision that light-induced reductive elimination may enable the development of challenging C(sp 3 )–C(sp 3 ) couplings.

Alkyls↗
NASA NTRS1981

Compressed television transmission: A market survey

NASA's compressed television transmission technology is described, and its potential market is considered; a market that encompasses teleconferencing, remote medical diagnosis, patient monitoring, transit station surveillance, as well as traffic management and control. In addition, current and potential television transmission systems and their costs and potential manufacturers are considered.

Lizak, R. M.↗
NASA NTRS1990

Research on conceptual/innovative design for the life cycle

The goal of this research is developing and integrating qualitative and quantitative methods for life cycle design. The definition of the problem includes formal computer-based methods limited to final detailing stages of design; CAD data bases do not capture design intent or design history; and life cycle issues were ignored during early stages of design. Viewgraphs outline research in conceptual design; the SYMON (SYmbolic MONotonicity analyzer) algorithm; multistart vector quantization optimization algorithm; intelligent manufacturing: IDES - Influence Diagram Architecture; and 1st PRINCE (FIRST PRINciple Computational Evaluator).

Cagan, Jonathan↗
NASA NTRS1990

AI/OR computational model for integrating qualitative and quantitative design methods

A theoretical framework for integrating qualitative and numerical computational methods for optimally-directed design is described. The theory is presented as a computational model and features of implementations are summarized where appropriate. To demonstrate the versatility of the methodology we focus on four seemingly disparate aspects of the design process and their interaction: (1) conceptual design, (2) qualitative optimal design, (3) design innovation, and (4) numerical global optimization.

Agogino, Alice M.↗
NASA NTRS1990

Inducing optimally directed non-routine designs

Non-routine designs are characterized by the creation of new variables and thus an expansion of the design space. These differ from routine designs in that the latter are restricted to a fixed set of variables and thus a pre-defined design space. In previous papers, the 1stPRINCE non-routine design methodology that expands the design space in such a way that optimal trends dictate the direction and form of this expansion is described. How inductive techniques can determine these optimal trends are examined. The induction techniques in 1stPRINCE utilize constraint information from monotonicity analysis to determine how to mutate the design space. The process observes the constraint information of mutated designs and induces trends from those constraints. Application of 1stPRINCE to a beam under flexural load leads to an optimally directed tapered beam. An interesting application of 1stPRINCE to determine the optimally directed shape of a spinning square block such that resistance to spinning is minimized leads to the discovery of a circular wheel.

Cagan, Jonathan↗