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At least 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on SrAsO5 by Materials Project

SrAsO5 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Sr is bonded in a 6-coordinate geometry to eight O atoms. There are a spread of Sr–O bond distances ranging from 2.51–3.07 Å. As is bonded in a tetrahedral geometry to four O atoms. There are a spread of As–O bond distances ranging from 1.70–1.75 Å. There are five inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one Sr and one As atom. In the second O site, O is bonded in a distorted bent 150 degrees geometry to one Sr and one As atom. In the third O site, O is bonded in a distorted trigonal planar geometry to two equivalent Sr and one As atom. In the fourth O site, O is bonded in a distorted water-like geometry to two equivalent Sr atoms. In the fifth O site, O is bonded in a distorted trigonal planar geometry to two equivalent Sr and one As atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrMg6Ga by Materials Project

SrMg6Ga crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Sr is bonded in a 12-coordinate geometry to eight Mg and two equivalent Ga atoms. There are a spread of Sr–Mg bond distances ranging from 3.38–3.56 Å. Both Sr–Ga bond lengths are 3.28 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 1-coordinate geometry to one Sr, four Mg, and one Ga atom. There are two shorter (3.09 Å) and two longer (3.11 Å) Mg–Mg bond lengths. The Mg–Ga bond length is 2.93 Å. In the second Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Sr, six Mg, and two equivalent Ga atoms. There are a spread of Mg–Mg bond distances ranging from 3.03–3.37 Å. Both Mg–Ga bond lengths are 2.98 Å. In the third Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Sr and eight Mg atoms. Both Mg–Mg bond lengths are 3.24 Å. In the fourth Mg site, Mg is bonded in a 2-coordinate geometry to four Mg atoms. Ga is bonded in a 8-coordinate geometry to two equivalent Sr and six Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2AlGa3 by Materials Project

Sr2Ga3Al is hexagonal omega structure-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Sr is bonded to nine Ga and three equivalent Al atoms to form a mixture of edge and face-sharing SrAl3Ga9 cuboctahedra. All Sr–Ga bond lengths are 3.48 Å. All Sr–Al bond lengths are 3.48 Å. There are three inequivalent Ga sites. In the first Ga site, Ga is bonded in a 9-coordinate geometry to six equivalent Sr and three equivalent Ga atoms. All Ga–Ga bond lengths are 2.54 Å. In the second Ga site, Ga is bonded in a distorted trigonal planar geometry to six equivalent Sr and three equivalent Al atoms. All Ga–Al bond lengths are 2.54 Å. In the third Ga site, Ga is bonded in a 9-coordinate geometry to six equivalent Sr and three equivalent Ga atoms. Al is bonded in a distorted trigonal planar geometry to six equivalent Sr and three equivalent Ga atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr3Li by Materials Project

Li(Sr)3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional and consists of two lithium molecules and one Sr framework. In the Sr framework, Sr is bonded in a 12-coordinate geometry to eight equivalent Sr atoms. There are a spread of Sr–Sr bond distances ranging from 3.98–4.13 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba3SrSn12 by Materials Project

Ba3SrSn12 crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are three inequivalent Ba sites. In the first Ba site, Ba is bonded to twelve Sn atoms to form distorted BaSn12 cuboctahedra that share corners with two equivalent BaSn12 cuboctahedra, corners with four equivalent SrSn12 cuboctahedra, and faces with eight BaSn12 cuboctahedra. There are a spread of Ba–Sn bond distances ranging from 3.63–3.76 Å. In the second Ba site, Ba is bonded to twelve Sn atoms to form distorted BaSn12 cuboctahedra that share corners with six BaSn12 cuboctahedra, faces with four BaSn12 cuboctahedra, and faces with four equivalent SrSn12 cuboctahedra. There are a spread of Ba–Sn bond distances ranging from 3.62–3.74 Å. In the third Ba site, Ba is bonded to twelve Sn atoms to form distorted BaSn12 cuboctahedra that share corners with six BaSn12 cuboctahedra, faces with two equivalent SrSn12 cuboctahedra, and faces with six BaSn12 cuboctahedra. There are a spread of Ba–Sn bond distances ranging from 3.62–3.76 Å. Sr is bonded to twelve Sn atoms to form distorted SrSn12 cuboctahedra that share corners with two equivalent SrSn12 cuboctahedra, corners with four equivalent BaSn12 cuboctahedra, faces with two equivalent SrSn12 cuboctahedra, and faces with six BaSn12 cuboctahedra. There are a spread of Sr–Sn bond distances ranging from 3.59–3.73 Å. There are eight inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to two equivalent Ba, two equivalent Sr, and six Sn atoms. There are two shorter (3.21 Å) and four longer (3.24 Å) Sn–Sn bond lengths. In the second Sn site, Sn is bonded in a 4-coordinate geometry to four Ba and six Sn atoms. There are two shorter (3.20 Å) and four longer (3.24 Å) Sn–Sn bond lengths. In the third Sn site, Sn is bonded in a 4-coordinate geometry to two Ba, two equivalent Sr, and six Sn atoms. There are one shorter (3.21 Å) and four longer (3.25 Å) Sn–Sn bond lengths. In the fourth Sn site, Sn is bonded in a 10-coordinate geometry to four Ba and six Sn atoms. There are a spread of Sn–Sn bond distances ranging from 3.12–3.25 Å. In the fifth Sn site, Sn is bonded in a 4-coordinate geometry to two equivalent Ba, two equivalent Sr, and six Sn atoms. Both Sn–Sn bond lengths are 3.18 Å. In the sixth Sn site, Sn is bonded in a 4-coordinate geometry to four Ba and six Sn atoms. Both Sn–Sn bond lengths are 3.19 Å. In the seventh Sn site, Sn is bonded in a 10-coordinate geometry to three Ba, one Sr, and six Sn atoms. The Sn–Sn bond length is 3.12 Å. In the eighth Sn site, Sn is bonded in a 10-coordinate geometry to three Ba, one Sr, and six Sn atoms. The Sn–Sn bond length is 3.15 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrMg2 by Materials Project

Mg2Sr crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Sr is bonded in a 11-coordinate geometry to five equivalent Sr and eight Mg atoms. There are a spread of Sr–Sr bond distances ranging from 3.58–4.20 Å. There are a spread of Sr–Mg bond distances ranging from 3.58–3.78 Å. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to three equivalent Sr and six Mg atoms. There are a spread of Mg–Mg bond distances ranging from 3.19–3.33 Å. In the second Mg site, Mg is bonded in a 9-coordinate geometry to five equivalent Sr and four equivalent Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr4Ca(FeO3)5 by Materials Project

Sr4Ca(FeO3)5 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4/m space group. The structure is three-dimensional. Sr is bonded to twelve O atoms to form SrO12 cuboctahedra that share corners with three equivalent CaO12 cuboctahedra, corners with nine equivalent SrO12 cuboctahedra, a faceface with one CaO12 cuboctahedra, faces with five equivalent SrO12 cuboctahedra, and faces with eight FeO6 octahedra. There are nine shorter (2.76 Å) and three longer (2.78 Å) Sr–O bond lengths. Ca is bonded to twelve O atoms to form CaO12 cuboctahedra that share corners with twelve equivalent SrO12 cuboctahedra, faces with two equivalent CaO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight equivalent FeO6 octahedra. All Ca–O bond lengths are 2.75 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six FeO6 octahedra and faces with eight equivalent SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. There is two shorter (1.95 Å) and four longer (1.96 Å) Fe–O bond length. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six FeO6 octahedra, faces with two equivalent CaO12 cuboctahedra, and faces with six equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–1°. There is four shorter (1.95 Å) and two longer (1.96 Å) Fe–O bond length. There are five inequivalent O sites. In the first O site, O is bonded to four equivalent Sr and two equivalent Fe atoms to form distorted OSr4Fe2 octahedra that share corners with twenty-two OSr4Fe2 octahedra, edges with four equivalent OSr3CaFe2 octahedra, and faces with eight equivalent OSr4Fe2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. In the second O site, O is bonded to three equivalent Sr, one Ca, and two equivalent Fe atoms to form distorted OSr3CaFe2 octahedra that share corners with twenty-two OSr4Fe2 octahedra, edges with four OSr4Fe2 octahedra, and faces with eight OSr2Ca2Fe2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. In the third O site, O is bonded to four equivalent Sr and two Fe atoms to form distorted OSr4Fe2 octahedra that share corners with twenty-two OSr2Ca2Fe2 octahedra, edges with four OSr2Ca2Fe2 octahedra, and faces with eight OSr4Fe2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. In the fourth O site, O is bonded to two equivalent Sr, two equivalent Ca, and two equivalent Fe atoms to form distorted OSr2Ca2Fe2 octahedra that share corners with twenty-two OSr4Fe2 octahedra, edges with four OSr2Ca2Fe2 octahedra, and faces with eight OSr2Ca2Fe2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. In the fifth O site, O is bonded to four equivalent Sr and two equivalent Fe atoms to form distorted OSr4Fe2 octahedra that share corners with twenty-two OSr2Ca2Fe2 octahedra, edges with four OSr4Fe2 octahedra, and faces with eight OSr2Ca2Fe2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrCd(IO2)4 by Materials Project

SrCd(O2I)4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Sr is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.93 Å. There are two inequivalent Cd sites. In the first Cd site, Cd is bonded in a 4-coordinate geometry to two equivalent O and two equivalent I atoms. Both Cd–O bond lengths are 2.28 Å. There are one shorter (2.74 Å) and one longer (2.80 Å) Cd–I bond lengths. In the second Cd site, Cd is bonded in a 4-coordinate geometry to two equivalent O and two equivalent I atoms. Both Cd–O bond lengths are 2.29 Å. There are one shorter (2.75 Å) and one longer (2.84 Å) Cd–I bond lengths. There are eight inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one I atom. The O–I bond length is 1.85 Å. In the second O site, O is bonded in an L-shaped geometry to one Sr and one I atom. The O–I bond length is 1.87 Å. In the third O site, O is bonded in a distorted water-like geometry to one Cd and two I atoms. There are one shorter (1.93 Å) and one longer (2.67 Å) O–I bond lengths. In the fourth O site, O is bonded in a distorted T-shaped geometry to one Sr and two I atoms. There are one shorter (1.90 Å) and one longer (2.53 Å) O–I bond lengths. In the fifth O site, O is bonded in a 3-coordinate geometry to one Cd and two I atoms. There are one shorter (1.95 Å) and one longer (2.51 Å) O–I bond lengths. In the sixth O site, O is bonded in a 2-coordinate geometry to one Sr and two I atoms. There are one shorter (1.87 Å) and one longer (2.66 Å) O–I bond lengths. In the seventh O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.38 Å. In the eighth O site, O is bonded in a single-bond geometry to one I atom. The O–I bond length is 1.81 Å. There are six inequivalent I sites. In the first I site, I is bonded in a distorted L-shaped geometry to four O atoms. In the second I site, I is bonded in a 3-coordinate geometry to three O atoms. In the third I site, I is bonded in a water-like geometry to two equivalent Cd atoms. In the fourth I site, I is bonded in a distorted rectangular see-saw-like geometry to four O atoms. In the fifth I site, I is bonded in a water-like geometry to two equivalent Cd atoms. In the sixth I site, I is bonded in a 4-coordinate geometry to four O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrMg6Fe by Materials Project

SrMg6Fe crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Sr is bonded to ten Mg and two equivalent Fe atoms to form a mixture of distorted face and corner-sharing SrMg10Fe2 cuboctahedra. There are a spread of Sr–Mg bond distances ranging from 3.22–3.68 Å. Both Sr–Fe bond lengths are 3.29 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 1-coordinate geometry to two equivalent Sr, four Mg, and one Fe atom. There are two shorter (3.01 Å) and two longer (3.18 Å) Mg–Mg bond lengths. The Mg–Fe bond length is 2.82 Å. In the second Mg site, Mg is bonded in a 2-coordinate geometry to six Mg and two equivalent Fe atoms. There are two shorter (3.20 Å) and four longer (3.25 Å) Mg–Mg bond lengths. Both Mg–Fe bond lengths are 3.24 Å. In the third Mg site, Mg is bonded in a 11-coordinate geometry to two equivalent Sr, seven Mg, and two equivalent Fe atoms. There are a spread of Mg–Mg bond distances ranging from 3.06–3.33 Å. Both Mg–Fe bond lengths are 3.02 Å. In the fourth Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Sr and eight Mg atoms. Fe is bonded in a 10-coordinate geometry to two equivalent Sr and eight Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2Nd(FeO3)3 by Materials Project

Sr2Nd(FeO3)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Sr is bonded to twelve O atoms to form distorted SrO12 cuboctahedra that share corners with nine equivalent SrO12 cuboctahedra, faces with three equivalent SrO12 cuboctahedra, and faces with eight FeO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.56–3.02 Å. Nd is bonded in a 12-coordinate geometry to twelve O atoms. There are a spread of Nd–O bond distances ranging from 2.47–3.11 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six FeO6 octahedra and faces with five equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 8–19°. There are a spread of Fe–O bond distances ranging from 1.95–1.99 Å. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six equivalent FeO6 octahedra and faces with six equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 8–15°. There are a spread of Fe–O bond distances ranging from 1.95–1.98 Å. There are five inequivalent O sites. In the first O site, O is bonded in a 6-coordinate geometry to three equivalent Sr, one Nd, and two Fe atoms. In the second O site, O is bonded in a 6-coordinate geometry to three equivalent Sr, one Nd, and two Fe atoms. In the third O site, O is bonded in a 5-coordinate geometry to two equivalent Sr, two equivalent Nd, and two equivalent Fe atoms. In the fourth O site, O is bonded in a 6-coordinate geometry to two equivalent Sr, two equivalent Nd, and two equivalent Fe atoms. In the fifth O site, O is bonded in a 6-coordinate geometry to three equivalent Sr, one Nd, and two Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KSrMg6 by Materials Project

KSrMg6 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. K is bonded to two equivalent Sr and ten Mg atoms to form distorted KSr2Mg10 cuboctahedra that share corners with four equivalent SrK2Mg10 cuboctahedra, corners with six equivalent KSr2Mg10 cuboctahedra, edges with two equivalent SrK2Mg10 cuboctahedra, faces with two equivalent KSr2Mg10 cuboctahedra, and faces with two equivalent SrK2Mg10 cuboctahedra. Both K–Sr bond lengths are 3.81 Å. There are a spread of K–Mg bond distances ranging from 3.45–3.54 Å. Sr is bonded to two equivalent K and ten Mg atoms to form distorted SrK2Mg10 cuboctahedra that share corners with four equivalent KSr2Mg10 cuboctahedra, corners with six equivalent SrK2Mg10 cuboctahedra, edges with two equivalent KSr2Mg10 cuboctahedra, faces with two equivalent KSr2Mg10 cuboctahedra, and faces with two equivalent SrK2Mg10 cuboctahedra. There are a spread of Sr–Mg bond distances ranging from 3.45–3.55 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to two equivalent K, two equivalent Sr, and six Mg atoms. There are a spread of Mg–Mg bond distances ranging from 3.32–3.46 Å. In the second Mg site, Mg is bonded in a 8-coordinate geometry to two equivalent K, two equivalent Sr, and four Mg atoms. There are one shorter (3.20 Å) and one longer (3.24 Å) Mg–Mg bond lengths. In the third Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent K and six Mg atoms. In the fourth Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Sr and six Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrMg2 by Materials Project

Mg2Sr crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Sr is bonded to three equivalent Sr and nine Mg atoms to form distorted SrSr3Mg9 cuboctahedra that share corners with nine equivalent SrSr3Mg9 cuboctahedra, corners with nine equivalent MgSr6Mg6 cuboctahedra, edges with six equivalent SrSr3Mg9 cuboctahedra, faces with three equivalent MgSr6Mg6 cuboctahedra, and faces with five equivalent SrSr3Mg9 cuboctahedra. All Sr–Sr bond lengths are 3.66 Å. There are six shorter (3.61 Å) and three longer (3.66 Å) Sr–Mg bond lengths. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 8-coordinate geometry to four equivalent Sr and four Mg atoms. There are two shorter (3.16 Å) and two longer (3.35 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded to six equivalent Sr and six equivalent Mg atoms to form MgSr6Mg6 cuboctahedra that share corners with eighteen equivalent SrSr3Mg9 cuboctahedra, edges with six equivalent MgSr6Mg6 cuboctahedra, faces with two equivalent MgSr6Mg6 cuboctahedra, and faces with six equivalent SrSr3Mg9 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrAl2(Si2O7)3 by Materials Project

SrAl2Si6O19O2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional and consists of two hydrogen peroxide molecules and one SrAl2Si6O19 framework. In the SrAl2Si6O19 framework, Sr is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of Sr–O bond distances ranging from 2.52–3.19 Å. Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with four SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.80 Å. There are three inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.65 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two equivalent AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. There are twelve inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one Sr, one Al, and one Si atom. In the second O site, O is bonded in a single-bond geometry to one Sr atom. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a linear geometry to two equivalent Si atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Sr and two equivalent Si atoms. In the seventh O site, O is bonded in a 3-coordinate geometry to one Sr, one Al, and one Si atom. In the eighth O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.23 Å. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the tenth O site, O is bonded in a bent 150 degrees geometry to one Sr and one O atom. In the eleventh O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the twelfth O site, O is bonded in a bent 150 degrees geometry to two Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The Role of Lewis Acid Sites in γ-Al 2 O 3 Oligomerization

Olefin oligomerization by γ-Al 2 O 3 has recently been reported, and it was suggested that Lewis acid sites are catalytic. The goal of this study is to determine the number of active sites per gram of alumina to confirm that Lewis acid sites are indeed catalytic. Addition of an inorganic Sr oxide base resulted in a linear decrease in the propylene oligomerization conversion at loadings up to 0.3 wt %; while, there is a >95 % loss in conversion above 1 wt % Sr. Additionally, there was a linear decrease in the intensity of the Lewis acid peaks of absorbed pyridine in the IR spectra with an increase in Sr loading, which correlates with the loss in propylene conversion, suggesting that Lewis acid sites are catalytic. Characterization of the Sr structure by XAS and STEM indicates that single Sr 2+ ions are bound to the γ-Al 2 O 3 surface and poison one catalytic site per Sr ion. The maximum loading needed to poison all catalytic sites, assuming uniform surface coverage, was ~0.4 wt % Sr, giving an acid site density of ~0.2 sites per nm2 of γ-Al 2 O 3 , or approximately 3 % of the alumina surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Microwave‐Assisted Synthesis of SrTiO 3 Nanocuboids without TiCl 4

Strontium titanate (STO) nanocuboids are a novel support for Pt nanoparticle catalysts (Pt/STO). The first of many steps in commercializing Pt/STO will be developing a scalable, environmentally sustainable, and cost‐effective STO nanocuboid synthesis. Herein, Sr–Ti–OH mixtures are synthesized from various Sr 2+ and Ti 4+ reagents and treated by convection‐ and microwave‐assisted heating to obtain STO nanoparticles. These experiments clarify how phase composition of the prehydrothermal Sr–Ti–OH mixture and choice of heating method affect final nanoparticle morphology. In Sr–Ti–OH mixtures synthesized with TiCl 4 , STO is the most stable phase and precipitates prior to heating, while titania sol–gels are the most stable phase when other Ti 4+ sources are used. STO nanocrystals always form when Sr–Ti–OH mixtures are treated by convection heating, though nanocuboids are only observed if STO precipitates from the Sr–Ti–OH mixture. Microwave‐assisted hydrothermal treatment more rapidly heats the precursor solution, and thus, STO nanocuboids can form from a variety of Sr–Ti–OH mixtures regardless of mixture composition. Two microwave syntheses of STO nanocuboids are reported: one which uses TiCl 4 as a Ti 4+ source, and another that uses titanium(IV) bis(ammonium lactato) dihydroxide ([NH 4 CH 3 CH(O)CO 2 ] 2 Ti(OH) 2 ), a water‐stable Ti 4+ complex.

Peczak, Ian L.↗
DOE OSTI2023

Strontium Effects on the Formation of Iron-Intermetallic Phases in Secondary Al–9Si–0.6Fe Alloys

The presence and morphology of Fe-containing intermetallic phases affect the mechanical properties of aluminum alloys, especially in secondary Al–Si-based cast alloys. Although strontium (Sr) addition of 50 to 500 ppm is known to refine the needle-type eutectic silicon structure, the influence of Sr on the formation of Fe-intermetallic phases remains unclear. The present work investigates the combined additions of Sr and Mn to Al–9Si–0.6Fe–0.35Mg (All compositions are in wt pct except otherwise stated.) alloys on the formation of Fe-intermetallic phases at different solidification rates from ~ 1.5 to ~ 60 °C/s. Long and branched-type AlFeSi phase with size ranging from 50 to 120 µm are more common when solidified at the rate of 1.5 °C/s regardless of Sr and Mn additions. However, at the fast solidification rate of 60 °C/s, a 60 ppm Sr addition significantly reduced the average length of needle-shaped AlFeSi phase to less than 3 to 5 µm. Thermodynamic simulations have been performed using CALculation of PHAse Diagrams (CALPHAD) models to predict the formation of various phases and their possible interactions during solidification. The results indicated that the combination of a high solidification rate and about 60 ppm of Sr is beneficial to refining the δ-Al 3 FeSi 2 phase in Al–Si–Mg alloys containing 0.6 pctFe. As a result, this unexpected finding of Fe-intermetallic refinement by low Sr addition (~60 ppm) provides an important guide in designing secondary alloys for sustainable casting applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Merging flux-variance with surface renewal methods in the roughness sublayer and the atmospheric surface layer

In this article, Two micrometeorological methods utilizing high-frequency sampled air temperature were tested against eddy covariance (EC) sensible heat flux (𝐻) measurements at three sites representing agricultural, agro-forestry, and forestry systems. The two methods cover conventional and newly proposed forms of the flux-variance (FV) and surface renewal (SR) schemes of differing complexities. The sites represent measurements in surface, roughness, and roughness to surface transitional layers. Regression analyzes against EC show that the most reliable FV and SR forms estimate 𝐻 with slopes within ±10% from unity and coefficient of determination 𝑅2 > 0.9 across all the three sites. The best performance of both FV and SR was found at the agricultural site with measurements well within the surface layer, while the worst was found for the tall forest with measurements within the roughness sublayer where its thickness needed to be additionally estimated. The main variable driving 𝐻 in FV is the temperature variance, whereas in SR, it is the geometry of ramp-like structures. Since these structures are also responsible for most of the temperature variance, a novel FV-SR approach emerging from combining the methods is proposed and evaluated against EC measurements and conventional FV and SR schemes. The proposed FV-SR approach requiring only a single fast response thermocouple is potentially independent of calibration and ameliorates some of the theoretical objections that arise when combining ramp statistics with similarity arguments. The combination of methods also provides new insights into the contribution of coherent structures to the temperature variance and its dependence on atmospheric stratification. Other potential utility of the new method is to include it in multi-tool assessments of surface energy fluxes, since a convergence or divergence of the results has a high diagnostic value.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Strain-driven surface reconstruction and cation segregation in layered Li(Ni 1– x – y Mn x Co y )O 2 (NMC) cathode materials

The composition, structure and phase transformations occurring on cathode surfaces greatly affect the performance of Li-ion batteries. Li-Ion diffusion and surface–electrolyte interaction are two major phenomena that impact the capacity and cell impedance. The effects of surface reconstruction (SR) of cathode materials on the performance of Li-ion batteries are of current interest. However, the origin and evolution of the SR are still not well understood. In this work, density functional theory (DFT) calculations are used to investigate the processes taking place during surface segregation and reconstruction. Facet dependent segregation was found in Li(Ni 1– x – y Mn x Co y )O 2 (NMC) cathodes. Specifically, Co tends to segregate to the (104) surface of the primary particles within the transition metal layer, while Ni ions tend to segregate to the (012) surface in the Li layer, forming a SR. Experimental evidence shows the SR to be epitaxial with the bulk of the as-synthesized material, and the new SR phase is pinned to the NMC unit cell leading to a strained SR. Here, we demonstrate that strain can stabilize a spinel structure of the SR layers. Understanding the effects of surface strain opens a new avenue for the design of cathode materials with enhanced surface properties.

25 ENERGY STORAGE↗