Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Zn”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Ground electronic state description of thiourea coordination in homoleptic Zn 2+ , Ni 2+ and Co 2+ complexes using sulfur K -edge X-ray absorption spectroscopy

Sulfur K-edge X-ray absorption spectroscopy (XAS) was employed to experimentally characterize the coordinative bond between the thiourea (TU) or thiocarbamide ligand and transition metal (TM) ions Zn 2+ , Co 2+ and Ni 2+ in distorted tetrahedral and octahedral homoleptic coordination environments. Comparisons of XAS spectra of the free TU ligand and [Zn(TU) 4 ] 2+ , [Co(TU) 4 ] 2+ and [Ni(TU) 6 ] 2+ complexes clearly identify spectral features unique to TM 2+ –S(TU) bonding. Quantitative analysis of pre-edge intensities describes the covalency of Ni 2+ —S(TU) and Co 2+ —S(TU) bonding to be at most 21% and 9% as expressed by the S 3p contributions per TM 3d electron hole. Using relevant Ni 2+ complexes with dithiocarbamate and thioether ligands, we evaluated the empirical S 1s → 3p transition dipole integrals developed for S-donor ligands and their dependence on heteroatom substitutions. With the aid of density functional theory-based ground electronic state calculations, we found evidence for the need of using a transition dipole that is dependent on the presence of conjugated heteroatom (N) substitution in these S-donor ligands.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Dual-Wavelength Time-Resolved Photoluminescence Study of CdSe x Te 1-x Surface Passivation via Mg y Zn 1-y O and Al 2 O 3

Voltage loss is currently one of the biggest challenges facing cadmium telluride (CdTe) based photovoltaics. Determining the location(s) of major voltage loss within the device stack (e.g., front/back interface, grain boundaries) is therefore of primary interest. Here, we present a custom-built time-resolved photoluminescence system with two excitation wavelengths - 670 (standard) and 405 nm - to probe the device stack at depths of approximately 130 and 35 nm, respectively; their comparison helps differentiate interface and bulk contributions to carrier lifetime. We apply this system to examine the passivation effect of two significant recent advances in CdTe: the incorporation of Se to form graded CdSe x Te 1-x and the replacement of CdS with Mg y Zn 1-y O. It is found that x = 0.2 Se is required to obtain lifetime improvements, primarily in the bulk. Additionally, evidence for trapping at the Mg y Zn 1-y O/CdSe x Te 1-x interface was observed. Furthermore, this indicates further work is required to sufficiently passivate the front interface.

CdSeTe↗
DOE OSTI2021

Growth of Cd 0.9 Zn 0.1 Te 1-y Se y Single Crystals for Room Temperature Gamma-Ray Detection

Quaternary Cd 0.9 Zn 0.1 Te 1-y Sey (CZTS) single crystals, a novel room-temperature nuclear radiation detector semiconductor material, have been grown using a modified vertical Bridgman method (VBM) and a travelling heater method (THM). The percentage concentration of selenium in the VBM-grown crystal was 3% and that in the THM-grown crystal was 2%. While the THM Frisch collar detector (4.4 × 4.4 × 10.7 mm 3 ) produced a highly resolved pulse height spectra (PHS) with a resolution of ~1.06% for 662-keV gamma rays without any correction, the VBM-grown detector (10 × 10 × 2 mm 3 ) offered a high energy resolution of ~2% after application of a digital biparametric correction. The high-resolution performance of these detectors has been attributed to the addition of Se in the Cd 0.9 Zn 0.1 Te (CZT) matrix. Ab-initio calculations based on density functional theory (DFT) also confirmed that the addition of Se in the CZT matrix helps to reduce the formation of TeCd and the TeZn anti-sites. The VBM-grown crystals were characterized using powder x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS). While XRD results revealed sharp diffraction peaks confirming the crystalline nature of the grown crystal, the EDS results confirmed the targeted stoichiometry of the elemental composition. The bulk resistivity of the grown crystal was calculated to be ~3 × 10 10 Ω-cm from current-voltage characteristics recorded at room temperature in a planar configuration, ensuring that the grown CZTS crystals have low dark current as required for detector-grade crystals.

42 ENGINEERING↗
DOE OSTI2022

The role of Co valence in charge transport in the entropy‐stabilized oxide (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O

Abstract Many of the studies on the entropy‐stabilized oxide (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O have been heavily application‐based. Previous works have studied effects of cation stoichiometry on the entropy‐driven reaction to form a single phase, but a fundamental exploration of the effects of anion stoichiometry and/or redox chemistry on electrical properties is lacking. Using near‐edge X‐ray absorption fine structure (NEXAFS) and electrical measurements, we show that oxidizing thin film samples of (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O affects primarily the valence of Co, leaving the other cations in this high‐entropy system unchanged. This oxidation increases electrical conduction in these thin films, which occurs via small polaron hopping mediated by the Co valence shift from 2+ to a mixed 2+/3+ state. In parallel, we show that bulk samples sintered in an oxygen‐rich atmosphere have a lower activation energy for electrical conduction than those equilibrated in a nitrogen (reducing) atmosphere. Combining feasible defect compensation scenarios with electrical impedance measurements and NEXAFS data, we propose a self‐consistent interpretation of Co redox‐mediated small polaron conduction as the dominant method of charge transfer in this system.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Phase evolution during conventional and reactive flash sintering of (Mg,Ni,Co,Cu,Zn)O via in situ X-ray diffraction

Reactive flash sintering (RFS) enables the simultaneous synthesis and sintering of ceramics and has been shown to affect the reaction pathway of different materials. Herein, in situ synchrotron X-ray diffraction (XRD) is used to investigate the (Mg,Ni,Co,Cu,Zn)O entropy-stabilized oxide formation during: (i) conventional heating and (ii) RFS under current rate-controlled mode. The same reaction pathway is verified in both instances: the starting rock-salt (RS), spinel (Co 3 O 4 ), tenorite (CuO), and wurtzite (ZnO) phases transform into a single RS phase with a (1 1 1) to (2 0 0) intensity ratio of 0.67, consistent with a random distribution of the cations into the structure. Pt lattice peak shift from the XRD patterns is used as standard to monitor the sample surface temperature, revealing a strong endothermic reaction during the RS single-phase formation (Pt peaks shift toward higher angles while increasing sample temperature/current density). Furthermore, in RFS, the single-phase RS structure is formed in just 60 s at a furnace temperature of 600°C and a current rate of 220 mA mm -2 /min. Therefore, RFS greatly accelerates the synthesis of (Mg,Ni,Co,Cu,Zn)O, however, it does not play a role in the reaction pathway for this material formation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Biocompatibility of a novel heat-treated and ceramic-coated magnesium alloy (Mg–1.2Zn–0.5Ca–0.5Mn) for resorbable skeletal fixation devices

Our recent exploration into the use of biodegradable metals and surface treatments resulting in sufficient strength for skeletal reconstruction applications has led to the need to test these devices’ cytotoxicity. More specifically, our group has developed a resorbable magnesium alloy, Mg–1.2Zn–0.5Ca–0.5Mn, that can be strengthened by heat treatment and coated with a ceramic layer offering time-certain resorption of a medical device. This in vitro study shows that these treatments do not result in cytotoxicity. Both heat-treated (HT) and HT + ceramic-coated (sol–gel) coupons demonstrated more than 70% viability. Thus, these processing steps are likely to be useful in producing biocompatible, resorbable implants that incorporate our Mg–1.2Zn–0.5Ca–0.5Mn alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Metal-ligand interactions in a redox active ligand system. Electrochemistry and spectroscopy of [M(dipyvd) 2 ] n+ (M=Zn, Ni, n =0, 1, 2)

Reaction of nickel and zinc triflates with the tridentate leucoverdazyl 1-isopropyl-3,5-di (2'-pyridyl)-6-oxo-2H-tetrazine (dipyvdH) and triethylamine resulted in the neutral coordination compounds M(dipyvd) 2 (M = Ni,Zn). In acetonitrile, both compounds undergo two one electron oxidation processes, Zn (dipyvd) 2 at -0.28 V and -0.12 V and Ni(dipyvd) 2 at -0.32 V and -0.15 V vs ferrocene/ferricenium. Oxidations are ligand based resulting in an intermediate mixed valence species and a cationic bis(verdazyl) compound respectively. Oxidation of the ligand changes a localized, antiaromatic, non-planar 8π electron anion to a planar, delocalized 7π electron radical. The change in ligand structure results in an increase in the octahedral ligand field splitting from 10,500 cm –1 to ~13,000 cm –1 , suggesting an increase in the pi acceptor character of the ligand. In the mixed valence species, spectroscopic data suggests minimal interaction between ligands mediated by the metal center; i.e., these are class I-II systems in the Robin-Day classification.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Texture and microstructure evolution in thermomechanically processed Mg-Ca and Mg-Zn-Ca alloys

Mg-Zn-Ca alloys have the potential for producing Mg alloy sheets with weaker basal textures and therefore improved formability. Thermomechanical processing (TMP) also plays a substantial role in determining the final sheet texture. The interplay of these variables, TMP and alloying, complicates comparisons of alloys across the literature. This work systematically explores the texture evolution and recrystallization behavior in Mg-Ca and Mg-Zn-Ca alloys during plane strain compression (PSC) using a Gleeble thermomechanical simulator. It is demonstrated that the basal texture intensity and texture characteristics change significantly during post-deformation annealing, particularly in the ternary alloys. It is also shown that careful selection of the TMP processing variables used during PSC is essential to producing weak textures. In particular, it is important to limit the recrystallization that occurs between compressive hits. This is achieved by adjusting solute content, strain rate, and the duration of the soak between passes.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(GaSe2)2 by Materials Project

ZnGa2Se4 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. Zn2+ is bonded to four equivalent Se2- atoms to form ZnSe4 tetrahedra that share corners with eight GaSe4 tetrahedra. All Zn–Se bond lengths are 2.50 Å. There are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four equivalent Se2- atoms to form GaSe4 tetrahedra that share corners with four equivalent ZnSe4 tetrahedra and corners with four equivalent GaSe4 tetrahedra. All Ga–Se bond lengths are 2.46 Å. In the second Ga3+ site, Ga3+ is bonded to four equivalent Se2- atoms to form GaSe4 tetrahedra that share corners with four equivalent ZnSe4 tetrahedra and corners with four equivalent GaSe4 tetrahedra. All Ga–Se bond lengths are 2.46 Å. Se2- is bonded in a trigonal non-coplanar geometry to one Zn2+ and two Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(GaTe2)2 by Materials Project

ZnGa2Te4 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. Zn2+ is bonded to four equivalent Te2- atoms to form ZnTe4 tetrahedra that share corners with eight GaTe4 tetrahedra. All Zn–Te bond lengths are 2.69 Å. There are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four equivalent Te2- atoms to form GaTe4 tetrahedra that share corners with four equivalent ZnTe4 tetrahedra and corners with four equivalent GaTe4 tetrahedra. All Ga–Te bond lengths are 2.67 Å. In the second Ga3+ site, Ga3+ is bonded to four equivalent Te2- atoms to form GaTe4 tetrahedra that share corners with four equivalent ZnTe4 tetrahedra and corners with four equivalent GaTe4 tetrahedra. All Ga–Te bond lengths are 2.68 Å. Te2- is bonded in a trigonal non-coplanar geometry to one Zn2+ and two Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(FeO2)2 by Materials Project

ZnFe2O4 is Spinel structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Fe3+ is bonded to six equivalent O2- atoms to form FeO6 octahedra that share corners with six equivalent ZnO4 tetrahedra and edges with six equivalent FeO6 octahedra. All Fe–O bond lengths are 2.05 Å. Zn2+ is bonded to four equivalent O2- atoms to form ZnO4 tetrahedra that share corners with twelve equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 58°. All Zn–O bond lengths are 2.00 Å. O2- is bonded to three equivalent Fe3+ and one Zn2+ atom to form a mixture of distorted edge and corner-sharing OZnFe3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(InTe2)2 by Materials Project

ZnIn2Te4 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. Zn2+ is bonded to four equivalent Te2- atoms to form ZnTe4 tetrahedra that share corners with eight InTe4 tetrahedra. All Zn–Te bond lengths are 2.70 Å. There are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to four equivalent Te2- atoms to form InTe4 tetrahedra that share corners with four equivalent ZnTe4 tetrahedra and corners with four equivalent InTe4 tetrahedra. All In–Te bond lengths are 2.85 Å. In the second In3+ site, In3+ is bonded to four equivalent Te2- atoms to form InTe4 tetrahedra that share corners with four equivalent ZnTe4 tetrahedra and corners with four equivalent InTe4 tetrahedra. All In–Te bond lengths are 2.86 Å. Te2- is bonded in a trigonal non-coplanar geometry to one Zn2+ and two In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(InS2)2 by Materials Project

ZnIn2S4 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of two ZnIn2S4 sheets oriented in the (0, 0, 1) direction. Zn2+ is bonded to four S2- atoms to form distorted ZnS4 trigonal pyramids that share corners with three equivalent InS6 octahedra and corners with six equivalent ZnS4 trigonal pyramids. The corner-sharing octahedral tilt angles are 62°. There are three shorter (2.27 Å) and one longer (3.16 Å) Zn–S bond lengths. There are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to four S2- atoms to form InS4 tetrahedra that share corners with three equivalent InS6 octahedra and corners with six equivalent InS4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. There are one shorter (2.41 Å) and three longer (2.54 Å) In–S bond lengths. In the second In3+ site, In3+ is bonded to six S2- atoms to form InS6 octahedra that share corners with three equivalent InS4 tetrahedra, corners with three equivalent ZnS4 trigonal pyramids, and edges with six equivalent InS6 octahedra. There are three shorter (2.57 Å) and three longer (2.78 Å) In–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a trigonal planar geometry to three equivalent Zn2+ atoms. In the second S2- site, S2- is bonded in a rectangular see-saw-like geometry to four In3+ atoms. In the third S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent In3+ atoms. In the fourth S2- site, S2- is bonded to one Zn2+ and three equivalent In3+ atoms to form distorted corner-sharing SZnIn3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(InS2)2 by Materials Project

ZnIn2S4 is Spinel structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Zn2+ is bonded to four equivalent S2- atoms to form ZnS4 tetrahedra that share corners with twelve equivalent InS6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Zn–S bond lengths are 2.41 Å. In3+ is bonded to six equivalent S2- atoms to form InS6 octahedra that share corners with six equivalent ZnS4 tetrahedra and edges with six equivalent InS6 octahedra. All In–S bond lengths are 2.64 Å. S2- is bonded in a distorted rectangular see-saw-like geometry to one Zn2+ and three equivalent In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(InS2)2 by Materials Project

ZnIn2S4 crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one ZnIn2S4 sheet oriented in the (0, 0, 1) direction. Zn2+ is bonded to four S2- atoms to form ZnS4 tetrahedra that share corners with three equivalent InS6 octahedra and corners with six equivalent ZnS4 tetrahedra. The corner-sharing octahedral tilt angles are 61°. There are three shorter (2.32 Å) and one longer (2.67 Å) Zn–S bond lengths. There are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to six S2- atoms to form InS6 octahedra that share corners with three equivalent ZnS4 tetrahedra, corners with three equivalent InS4 tetrahedra, and edges with six equivalent InS6 octahedra. There are three shorter (2.59 Å) and three longer (2.75 Å) In–S bond lengths. In the second In3+ site, In3+ is bonded to four S2- atoms to form InS4 tetrahedra that share corners with three equivalent InS6 octahedra and corners with six equivalent InS4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. There are one shorter (2.46 Å) and three longer (2.51 Å) In–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a trigonal non-coplanar geometry to three equivalent Zn2+ atoms. In the second S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four In3+ atoms. In the third S2- site, S2- is bonded to one Zn2+ and three equivalent In3+ atoms to form distorted corner-sharing SZnIn3 tetrahedra. In the fourth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three equivalent In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(InSe2)2 by Materials Project

ZnIn2Se4 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. Zn2+ is bonded to four equivalent Se2- atoms to form ZnSe4 tetrahedra that share corners with eight InSe4 tetrahedra. All Zn–Se bond lengths are 2.51 Å. There are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to four equivalent Se2- atoms to form InSe4 tetrahedra that share corners with four equivalent ZnSe4 tetrahedra and corners with four equivalent InSe4 tetrahedra. All In–Se bond lengths are 2.64 Å. In the second In3+ site, In3+ is bonded to four equivalent Se2- atoms to form InSe4 tetrahedra that share corners with four equivalent ZnSe4 tetrahedra and corners with four equivalent InSe4 tetrahedra. All In–Se bond lengths are 2.64 Å. Se2- is bonded in a trigonal non-coplanar geometry to one Zn2+ and two In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(Bi3O5)4 by Materials Project

ZnBi12O20 crystallizes in the cubic I23 space group. The structure is three-dimensional. Zn2+ is bonded to four equivalent O2- atoms to form ZnO4 tetrahedra that share corners with twelve equivalent BiO5 square pyramids. All Zn–O bond lengths are 2.03 Å. Bi+3.17+ is bonded to five O2- atoms to form distorted BiO5 square pyramids that share corners with eight equivalent BiO5 square pyramids, a cornercorner with one ZnO4 tetrahedra, and an edgeedge with one BiO5 square pyramid. There are a spread of Bi–O bond distances ranging from 2.11–2.56 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to one Zn2+ and three equivalent Bi+3.17+ atoms to form corner-sharing OZnBi3 tetrahedra. In the second O2- site, O2- is bonded in a trigonal planar geometry to three equivalent Bi+3.17+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent Bi+3.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(SbO3)2 by Materials Project

ZnSb2O6 is Hydrophilite-derived structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with eight equivalent SbO6 octahedra and edges with two equivalent SbO6 octahedra. The corner-sharing octahedra tilt angles range from 51–52°. There are two shorter (2.09 Å) and four longer (2.11 Å) Zn–O bond lengths. Sb5+ is bonded to six O2- atoms to form SbO6 octahedra that share corners with four equivalent ZnO6 octahedra, corners with four equivalent SbO6 octahedra, an edgeedge with one ZnO6 octahedra, and an edgeedge with one SbO6 octahedra. The corner-sharing octahedra tilt angles range from 47–52°. There are two shorter (2.01 Å) and four longer (2.03 Å) Sb–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to one Zn2+ and two equivalent Sb5+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Zn2+ and two equivalent Sb5+ atoms.

36 MATERIALS SCIENCE↗