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Title: Structure of Calcium Aluminate Decahydrate (CaAl2O4.10D2O) from Neutron and X-ray Powder Diffraction Data

Abstract

Calcium aluminate decahydrate is hexagonal with the space group P63/m and Z = 6. The compound has been named CaAl2O4{center_dot}10H2O (CAH10) for decades and is known as the product obtained by hydration of CaAl2O4 (CA) in the temperature region 273-288 K - one of the main components in high-alumina cements. The lattice constants depend on the water content. Several sample preparations were used in this investigation: one CAH10, three CAD10 and one CA(D/H)10, where the latter is a zero-matrix sample showing no coherent scattering contribution from the D/H atoms in a neutron diffraction powder pattern. The crystal structure including the positions of the H/D atoms was determined from analyses of four neutron diffraction powder patterns by means of the ab initio crystal structure determination program FOX and the FULLPROF crystal structure refinement program. Additionally, eight X-ray powder diffraction patterns (Cu K[alpha]1 and synchrotron X-rays) were used to establish phase purity. The analyses of these combined neutron and X-ray diffraction data clearly show that the previously published positions of the O atoms in the water molecules are in error. Thermogravimetric analysis of the CAD10 sample preparation used for the neutron diffraction studies gave the composition CaAl2(OD)8(D2O)2{center_dot}2.42D2O. Neutron and X-ray powder diffractionmore » data gave the structural formula CaAl2(OX)8(X2O)2{center_dot}[gamma]X2O (X = D, H and D/H), where the [gamma] values are sample dependent and lie between 2.3 and 3.3.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
959548
Report Number(s):
BNL-82534-2009-JA
TRN: US1005757
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Crystallographica Section B: Structural Science; Journal Volume: 63
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS; ALUMINATES; ATOMS; CALCIUM; CEMENTS; COHERENT SCATTERING; CRYSTAL STRUCTURE; DIFFRACTION; HYDRATION; NEUTRON DIFFRACTION; NEUTRONS; SAMPLE PREPARATION; SPACE GROUPS; SYNCHROTRONS; THERMAL GRAVIMETRIC ANALYSIS; WATER; X-RAY DIFFRACTION; national synchrotron light source

Citation Formats

Christensen,A., Lebech, B., Sheptyakov, D., and Hanson, J. Structure of Calcium Aluminate Decahydrate (CaAl2O4.10D2O) from Neutron and X-ray Powder Diffraction Data. United States: N. p., 2007. Web. doi:10.1107/S0108768107035136.
Christensen,A., Lebech, B., Sheptyakov, D., & Hanson, J. Structure of Calcium Aluminate Decahydrate (CaAl2O4.10D2O) from Neutron and X-ray Powder Diffraction Data. United States. doi:10.1107/S0108768107035136.
Christensen,A., Lebech, B., Sheptyakov, D., and Hanson, J. Mon . "Structure of Calcium Aluminate Decahydrate (CaAl2O4.10D2O) from Neutron and X-ray Powder Diffraction Data". United States. doi:10.1107/S0108768107035136.
@article{osti_959548,
title = {Structure of Calcium Aluminate Decahydrate (CaAl2O4.10D2O) from Neutron and X-ray Powder Diffraction Data},
author = {Christensen,A. and Lebech, B. and Sheptyakov, D. and Hanson, J.},
abstractNote = {Calcium aluminate decahydrate is hexagonal with the space group P63/m and Z = 6. The compound has been named CaAl2O4{center_dot}10H2O (CAH10) for decades and is known as the product obtained by hydration of CaAl2O4 (CA) in the temperature region 273-288 K - one of the main components in high-alumina cements. The lattice constants depend on the water content. Several sample preparations were used in this investigation: one CAH10, three CAD10 and one CA(D/H)10, where the latter is a zero-matrix sample showing no coherent scattering contribution from the D/H atoms in a neutron diffraction powder pattern. The crystal structure including the positions of the H/D atoms was determined from analyses of four neutron diffraction powder patterns by means of the ab initio crystal structure determination program FOX and the FULLPROF crystal structure refinement program. Additionally, eight X-ray powder diffraction patterns (Cu K[alpha]1 and synchrotron X-rays) were used to establish phase purity. The analyses of these combined neutron and X-ray diffraction data clearly show that the previously published positions of the O atoms in the water molecules are in error. Thermogravimetric analysis of the CAD10 sample preparation used for the neutron diffraction studies gave the composition CaAl2(OD)8(D2O)2{center_dot}2.42D2O. Neutron and X-ray powder diffraction data gave the structural formula CaAl2(OX)8(X2O)2{center_dot}[gamma]X2O (X = D, H and D/H), where the [gamma] values are sample dependent and lie between 2.3 and 3.3.},
doi = {10.1107/S0108768107035136},
journal = {Acta Crystallographica Section B: Structural Science},
number = ,
volume = 63,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The stability of monocalcium aluminate decahydrate, with the nominal composition CaAl(2)O(4).10H(2)O (CAH(10)), has a decisive role for the strength development and durability of cementitious materials based on high alumina cements. This has prompted an investigation of the thermal transformation of crystalline monocalcium aluminate decahydrate in air to an amorphous phase by in-situ synchrotron X-ray powder diffraction in the temperature range from 25 to 500 degrees C, by DTA/TGA, and (2)H, (27)Al MAS NMR spectroscopy. The decomposition includes the loss of hydrogen-bonded water molecules in the temperature range up to 175 degrees C, coupled with a reduction of the unit cellmore » volume from 1928 A(3) at 25 degrees C, to 1674 A(3) at 185 degrees C. Furthermore, X-ray diffraction shows that CaAl(2)O(4).10H(2)O starts to transform to an amorphous phase at approximately 65 degrees C. This phase is fully developed at approximately 175 degrees C and it converts to crystalline CaAl(2)O(4) when heated to 1300 degrees C. The thermal decomposition in the temperature range from approximately 65 to approximately 175 degrees C involves both formation of an amorphous phase including AlO(4) tetrahedra and structural changes in the remaining crystalline phase.« less
  • In the present paper the authors report crystal structure of insulating compound Nd{sub 1.9}Ba{sub 1.1}Cu{sub 3}O{sub 7.28}--the Nd-rich terminating point of Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub z} solid solutions. This phase has an orthorhombic lattice with a = 3.8565(1){angstrom}, b = 7.7724(3){angstrom}, c = 22.9862(8){angstrom}. The space group Ammm was determined on the basis of IR and Raman spectroscopic data and electron diffraction analysis. The crystal structure was solved and refined from the powder XRD and time-of-flight neutron diffraction data. Neodymium atoms on the barium site compared to conventional NdBa{sub 2}Cu{sub 3}O{sub 7} crystal are ordered and form a face-centered supercell,more » while additional oxygen atoms occupy vacant chain sites in the vicinity of barium atoms.« less
  • No abstract prepared.
  • Lithium manganese oxides have been extensively studied at the cathode materials for advanced rechargeable lithium batteries because they offer high cell voltage, good rechargeability, and a wide operating temperature range with a much lower cost compared to LiNiO{sub 2} and LiCoO{sub 2}. Well-crystallized Li{sub 4}Mn{sub 5}O{sub 12} powder was prepared by heating a eutectic mixture of lithium acetate LiOAc and manganese nitrite Mn(NO{sub 3}){sub 2} in an O{sub 2} atmosphere. The structure of Li{sub 4}Mn{sub 5}O{sub 12} crystallites was found to be cubic spinel using Rietveld refinement of both neutron and X-ray powder diffraction profiles. We confirmed that lithium ionsmore » occupy both the tetrahedral sites 8a and part of the octahedral sites 16d, but not the 16c sites in the space group Fd{bar 3}m, while all the manganese ions occupy the 16d sites. The lattice parameter was found to be sensitive to synthesis temperature as a result of the variation in manganese valence. The presence of Mn{sup 3+} leads to the formation of a stoichiometric spinel Li[Li{sub x}Mn{sub 2-x}]O{sub 4} in which x decreases from 1/3 (Li{sub 4}Mn{sub 5}O{sub 12}) to 0 (LiMn{sub 2}O{sub 4}), with concomitant formation of Li{sub 2}MnO{sub 3} depending on the synthesis conditions.« less