PUBLICATIONS High temperature reactions in mold flux slags: Kinetic versus composition control. Monica Dapiaggi, Gilberto Artioli, Carlo Righi, Riccardo Carli. Dipartimento di Scienze della Terra, Sezione Mineralogia, Universita degli Studi di Milano, Milan, Italy. Journal of Non-Crystalline Solids 353 (2007) 2852–2860 Abstract The reactions taking place at high temperature during a mold flux slag crystallization are studied in details by means of high temperature powder diffraction. Two heating ramps were performed in two different temperature ranges, showing the formation and decomposition of various phases during the whole crystallization process. A full isothermal kinetic analysis was carried out for the formation of cuspidine, whose results were compared with non-isothermal data provided by DTA analyses, showing a good agreement between the two techniques. P-V and T-V Equations of State of natural biotite: An in-situ high-pressure and high-temperature powder diffraction study, combined with Mössbauer spectroscopy. Pavese, Alessandro; Curetti, Nadia; Diella, Valeria; Levy, Davide; Dapiaggi, Monica; Russo, U. Dipartimento di Scienze della Terra, Sezione Mineralogia, Universita degli Studi di Milano, Milan, Italy. American Mineralogist, Volume 92, pages 1158.1164, 2007 Abstract The P-V and T-V equations of state of a natural biotite sample (Mg/Fe ratio . 1) have been studied using in-situ high-pressure (0.0001.11 GPa) synchrotron radiation powder diffraction at the European Synchrotron Radiation Facilities (ESRF) in Grenoble, France, and in-situ high-temperature (298.610 K) laboratory X-ray powder diffraction. A third-order Birch-Murnaghan model [V0 = 498.7(1) A3, measured value] provides the following elastic parameters: K0 = 49(1) GPa, K�f = 8.1(5). The volume thermal expansion is satisfactorily described by a constant value resulting in 37(2) 10.6 K.1. Mossbauer spectroscopy proves that REDOX reactions have occurred upon heating, presumably 2(OH. + Fe2+) �¨ 2O2. + 2Fe3+ + H2 �ª and/or 4Fe2+ + 2OH. + O2 �¨ 4Fe3+ + 3O2. + H2O. On the basis of the elastic and thermal parameters measured we have modeled the deformation contribution (Gdeform) to the Gibbs energy. The third-order Birch-Murnaghan model with V0 T xed at its experimental value and the model with reT ned V0 do not signiT cantly differ from one another in terms of Gdeform. A comparison based on Gdeform between biotite and phlogopite shows a better compliance to P of the former, though balanced in mineral reactions by a difference of molar volume, i.e., V0(biotite) > V0(phlogopite). Structural characterisation of high temperature K-exchanged sodalite. Dapiaggi, Monica; Artioli, Gilberto; Mazzocchia, Carlo; Merlini, Marco Dipartimento di Scienze della Terra, Sezione Mineralogia, Universita degli Studi di Milano, Milan, Italy. Z. Kristallogr. Suppl. 23 (2006) 437-442 Abstract The exchange reaction of Na-sodalite with KCl was studied by means of hightemperature X-ray powder diffraction, ex-situ and in-situ, up to 800 °C. The powder data were fully refined with the Rietveld method and showed that a substantial amount of K enters the structure in the same crystallographic position of Na, causing some Cl ions to be displaced from their position. The paper shows that sodalite is a potentially good matrix for trapping alkaline metal ions from the electrorefining process of nuclear waste and proposes a method to quickly estimate the amount of K in the structure. Characterization of omphacite jade from the Po valley, Piedmont, Italy. Adamo, Ilaria; Pavese, Alessandro; Prosperi, Loredana; Diella, Valeria; Ajo, David; Dapiaggi, Monica; Mora, Carlo; Manavella, Franco; Salusso, Franco; Giuliano, Valter. Dipartimento di Scienze della Terra, Sezione Mineralogia, Universita degli Studi di Milano, Milan, Italy. Journal of Gemmology (2006), 30(3/4), 215-226. Publisher: Gemmological Association and Gem Testing Laboratory of Great Britain, CODEN: JGOEAL ISSN: 1355-4565. Journal written in English. AN 2007:149291 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract A dark green jade was discovered recently in secondary alluvial deposits which are widespread in the Po valley, between Cuneo and Turin (Piedmont, Italy). Traditional gemol. tests were combined with advanced anal. techniques (x-ray powder diffraction, chem. compn. detn., absorption and photoluminescence spectroscopy) and thin section examns. to provide full characterization of this material and reveal that it is mainly composed of omphacite pyroxene. Negative thermal expansion in cuprite-type compounds: A combined synchrotron XRPD, EXAFS, and computational study of Cu2O and Ag2O. Artioli, Gilberto; Dapiaggi, Monica; Fornasini, Paolo; Sanson, Andrea; Rocca, Francesco; Merli, Marcello. Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Milan, Italy. Journal of Physics and Chemistry of Solids (2006), 67(9-10), 1918-1922. Publisher: Elsevier B.V., CODEN: JPCSAW ISSN: 0022-3697. Journal; General Review written in English. CAN 145:478654 AN 2006:930955 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract A review. Cuprite-type oxides (Cu2O and Ag2O) are framework structures composed by two interpenetrated networks of metal-sharing M4O tetrahedra (M = Cu, Ag). Both compds. exhibit a peculiar neg. thermal expansion (NTE) behavior over an extended temp. range (9-240 K for Cu2O, 30-470 K for Ag2O). High-accuracy synchrotron powder diffraction and EXAFS measurements were performed from 10 K up to the decompn. temp. to understand the nature of the NTE effects. The crit. comparison of the diffraction and absorption results concerning the temp. dependence of the interat. distances and of the at. vibrational parameters proves to be fundamental in defining the local dynamics of the atoms in the structure. Both techniques measure a strong transverse motion of the metal atoms perpendicularly to the O-M-O linear bonds. Furthermore, the anal. of the next-near-neighbors shell in the EXAFS data indicates a different temp. behavior of the M-M interaction between metal atoms related to the same framework and with respect to metal atoms located on distinct interpenetrated frameworks. The presence of M-M bonds is supported by first-principles calcn. of the charge d. distribution in Cu2O and Ag2O. Negative thermal expansion and local dynamics in Cu2O and Ag2O. Sanson, A.; Rocca, F.; Dalba, G.; Fornasini, P.; Grisenti, R.; Dapiaggi, M.; Artioli, G. Sezione CeFSA di Trento, IFN, Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche, Povo (Trento), Italy. Physical Review B: Condensed Matter and Materials Physics (2006), 73(21), 214305/1-214305/13. Publisher: American Physical Society, CODEN: PRBMDO ISSN: 1098-0121. Journal written in English. CAN 145:303131 AN 2006:670068 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract High-resoln. x-ray powder diffraction and extended x-ray-absorption fine-structure (EXAFS) measurements were performed on the isostructural framework crystals Cu2O and Ag2O as a function of temp. According to diffraction, both compds. exhibit a neg. thermal expansion (NTE) of the lattice parameter over extended temp. intervals (from 9 to 240 K for Cu2O, up to 470 K for Ag2O) and anisotropic thermal displacements of M atoms (M = Cu, Ag). EXAFS measures a pos. expansion of the nearest-neighbors M-O pair distance and a perpendicular to parallel anisotropy of relative motion, much stronger than the anisotropy of the abs. M motion. The M-O bond is much stiffer against stretching than against bending. According to EXAFS, out of the 12 M-M next-nearest-neighbor pairs, the 6 connected via a bridging O undergo neg. expansion, while the 6 lacking the bridging O undergo pos. expansion. These results show a rather complex local behavior, which, while confirming the connection of NTE to strong perpendicular vibrations, is inconsistent with rigid unit modes models and suggests a more flexible model based on rigid M-O rods. Incorporation of Trivalent Cations in Synthetic Garnets A3B5O12 (A = Y, Lu-La, B = Al, Fe, Ga). Maglia, Filippo; Buscaglia, Vincenzo; Gennari, Silvia; Ghigna, Paolo; Dapiaggi, Monica; Speghini, Adolfo; Bettinelli, Marco. IENI/CNR INSTM and Department Physical Chemistry, University of Pavia, Pavia, Italy. Journal of Physical Chemistry B (2006), 110(13), 6561-6568. Publisher: American Chemical Society, CODEN: JPCBFK ISSN: 1520-6106. Journal written in English. CAN 144:478133 AN 2006:230652 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract Static-lattice atomistic calcns. were used to study the soln. energy for the incorporation of 13 foreign cations at 3 different lattice positions of 12 synthetic garnets. Trends were obtained as a function of the ionic radius of the dopant cation, and the predictions about site preference were compared with both literature and exptl. data. The preferred substitution site is mainly detd. by the ionic size and was correctly predicted in all cases. Also, the energy difference between the preferred substitution site and the next favored site is relatively small in several cases, and hence the foreign ions can be inserted at two different positions by using the correct stoichiometry. A remarkably different behavior was encountered for Al garnets, due to the smaller size of the unit cell. In particular, some cations, such as Fe3+ and Ga3+, can be inserted at the dodecahedral position usually occupied by the rare-earth ion. Despite the limitations of the static-lattice approach, the results of the present simulations help in the understanding of the defect chem. of garnets, which is strongly responsible for the physicochem. properties (such as luminescence and ferrimagnetism) that make garnets interesting for technol. applications. Such results lead to the possibility of tuning the optical and luminescence properties of garnets by the formation of different types of solid solns. Use of IR-spectroscopy and diffraction to discriminate between natural, synthetic and treated turquoise, and its imitations. Pavese, Alessandro; Prosperi, Loredana; Dapiaggi, Monica. Universita degli Studi di Milano, Milan, Italy. Australian Gemmologist (2005), 22(8), 366-371. Publisher: Gemmological Association of Australia, CODEN: AGMLB2 ISSN: 0004-9174. Journal written in English. CAN 145:274995 AN 2005:1351589 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract This study aims at providing an overview, based on a statistically significant no. of samples, about the reliability of nondestructive IR spectroscopy, combined in some cases with diffraction, to det. the nature of turquoise specimens, be they natural, synthetic, treated, or its imitations. A total of 94 samples (32 natural, 12 synthetic, 16 treated, 34 imitations) were analyzed by IR spectroscopy in the non-destructive reflectance mode. Treated turquoise specimens were also studied in the IR transmission mode. Non-destructive X-ray diffraction was been used to remove ambiguities that IR spectroscopy was unable to resolve with respect to some imitations. High-Temperature Polymorphism in Metastable BiMnO3. Montanari, Erica; Calestani, Gianluca; Migliori, Andrea; Dapiaggi, Monica; Bolzoni, Fulvio; Cabassi, Riccardo; Gilioli, Edmondo. Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Universita di Parma, Parma, Italy. Chemistry of Materials (2005), 17(25), 6457-6467. Publisher: American Chemical Society, CODEN: CMATEX ISSN: 0897-4756. Journal written in English. CAN 144:92323 AN 2005:1205453 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract The multiferroic perovskite BiMnO3, synthesized under high-pressure conditions, decomps. if heated at room-pressure at 500-650 °C. Comparative studies by high-temp. X-ray diffraction, electron diffraction, thermal anal., and magnetic investigation revealed the existence of a complex pathway to decompn., depending on the heating rate, pressure, and atm. that involves different metastable phases. In particular the as-prepd. monoclinic phase (I) transforms to a second monoclinic form (II) at 210 °C and then to an orthorhombic phase (III) at 490 °C. These phase transitions, fast and reversible, occur on heating with a drop in vol. and are moved at higher temps. when pressure is decreased. The transition from II to III, typically obsd. in inert atm., can be detected also in air when the heating rate is kept sufficiently high. When III is heated in an oxygen-contg. atm. a slow irreversible transition to variants IV and then V takes place with kinetics depending on temp., heating rate, and oxygen partial pressure. Both IV and V are oxidized ferromagnetic phases contg. Mn4+ characterized by a modulated structure based on fundamental triclinic perovskite cells. Their magnetic behavior shows a strong analogy with thin films of BiMnO3, suggesting for the latter an oxidized nature and for the former a possible multiferroic behavior. P-V equation of state, thermal expansion, and P-T stability of synthetic zincochromite (ZnCr2O4 spinel). Levy, Davide; Diella, Valeria; Pavese, Alessandro; Dapiaggi, Monica; Sani, Alessandra. Dipartimento Scienze Mineralogiche e Petrologiche, Universita degli Studi di Torino, Turin, Italy. American Mineralogist (2005), 90(7), 1157-1162. Publisher: Mineralogical Society of America, CODEN: AMMIAY ISSN: 0003-004X. Journal written in English. CAN 143:350149 AN 2005:607990 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract The elastic properties and thermal behavior of synthetic zincochromite (ZnCr2O4) have been studied by combining room-temp. high-pressure (0.0001-21 GPa) synchrotron radiation powder diffraction data with high-temp. (298-1240 K) powder diffraction data. Elastic properties were obtained by fitting two Equations of State (EoS) to the P-V data. A third-order Birch-Murnaghan model, which provides results consistent with those from the Vinet EoS, yields: K0 = 183.1(±3.5) GPa, K' = 7.9(±0.6), K'' = -0.1278 GPa-1 (implied value), at V0 = 577.8221 .ANG.3 (fixed). Zincochromite does not exhibit order-disorder reactions at high temp. in the thermal range explored, in agreement with previous studies. The vol. thermal expansion was modeled with av = a0 + a1T + a2/T-2, where only the first coeff. was found to be significant [a0 = 23.0(4) 10-6 K-1]. Above 23 GPa diffraction patterns hint at the onset of a phase transition; the high pressure phase is obsd. at approx. 30 GPa and exhibits orthorhombic symmetry. The elastic and thermal properties of zincochromite were then used to model by thermodn. calcns. the P-T stability field of ZnCr2O4 with respect to its oxide constituents (Cr2O3 and rocksalt-like ZnO). Spinel is expected to decomp. into oxides at about 18 GPa and room temp., in absence of sluggish kinetics. EXAFS and XRD study of local dynamics in Cu2O and Ag2O. Sanson, A.; Dalba, G.; Fornasini, P.; Grisenti, R.; Rocca, F.; Artioli, G.; Dapiaggi, M.; Tiano, W. Istituto Nazionale per la Fisica della Materia and Dipartimento di Fisica dell'Universita di Trento, Trento, Italy. Physica Scripta, T (2005), T115(12th X-Ray Absorption Fine Structure International Conference (XAFS12), 2003), 271-273. Publisher: Royal Swedish Academy of Sciences, CODEN: PHSTER ISSN: 0281-1847. Journal; Computer Optical Disk written in English. CAN 143:276041 AN 2005:477045 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract Cu2O and Ag2O share the rather unusual cuprite structure, formed by 2 interpenetrating networks of corner-sharing M4O tetrahedra (M = Cu, Ag). Neg. thermal expansion of the cell parameter was obsd. from 5-200 K for Cu2O and £470 K for Ag2O by powder diffraction. In the case of Ag2O, it was shown by EXAFS that the lattice contraction is accompanied by an expansion of the Ag-O distance and that the deformation of the Ag4O tetrahedral is not negligible. We present a comparison between EXAFS and XRD results for both compds. The comparison between local and lattice thermal expansions, measured by EXAFS and XRD, resp., and the differences found between the 2 compds., allow to gain original insight on the mechanism of neg. thermal expansion in framework structures. Accurate measurement of the thermal expansion of MFI zeolite membranes by in situ HTXRPD. Lissinantti Gualtieri, M.; Gualtieri, A. F.; Hedlund, J.; Jareman, F.; Sterte, J.; Dapiaggi, M.. Department of Chemical and Metallurgical Engineering, Lulea University of Technology, Lulea, Swed. Studies in Surface Science and Catalysis (2004), 154A(Recent Advances in the Science and Technology of Zeolites and Related Materials), 703-709. Publisher: Elsevier B.V., CODEN: SSCTDM ISSN: 0167-2991. Journal written in English. CAN 144:281333 AN 2005:420836 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract Template removal by calcination of MFI type membranes is often accompanied by crack formation. The thermal behavior of MFI type membranes, synthesized with and without masking, was studied to understand the mechanism. Masking prevents growth of zeolite in the interior of the support during membrane synthesis. Rietveld refinements of powder diffraction data collected in situ at high temp. allowed to accurately det. the change in thermal expansion of the MFI film and the porous a-alumina support. During heating, a relatively large contraction of the cell vol. during template removal occurred in the zeolite powder and in the film of the membrane prepd. with masking. The much smaller decrease in the nonmasked sample indicates that this membrane is under stress during heating and as a consequence, cracks are formed. The stress imposed in the membrane prepd. without masking may be due to the opposite thermal behavior of the substrate in combination with strong bonds between the membrane and the support. Microscopic strain in synthetic pyrope-grossular solid solutions determined by synchrotron X-ray powder diffraction at 5 K: the relationship to enthalpy of mixing behavior. Dapiaggi, Monica; Geiger, Charles A.; Artioli, Gilberto. Dipartimento di Scienze della Terra "A. Desio", Universita degli Studi di Milano, Milan, Italy. American Mineralogist (2005), 90(2-3), 506-509. Publisher: Mineralogical Society of America, CODEN: AMMIAY ISSN: 0003-004X. Journal; Letter written in English. AN 2005:167140 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract A series of synthetic pyrope-grossular garnets (Mg3Al2Si3O12-Ca3Al2Si3O12) were investigated by powder X-ray synchrotron radiation at 5 K to det. their microscopic structural strain, which may be responsible for the obsd. excess enthalpy of mixing for this binary. This substitutional solid soln. provides an excellent system for investigating microscopic-macroscopic relationships and the phys. nature behind non-ideal thermodn. mixing behavior in silicates, because of the measurable nonidealities shown by its enthalpy and vol. of mixing. An anal. of the X-ray refection profiles, based on theor. considerations of X-ray line broadening, permits for the first time a direct exptl. detn. of crystallite size and the root-mean-square structural strain for a mineral solid soln. The measured microscopic strain shows pos. and asym. deviations from linearity across the join with the largest excess in pyrope-rich compns. There is a good correlation between the structural strain and the macroscopic enthalpy of mixing behavior for pyrope-grossular garnets as measured by calorimetry. The effect of oxidation and reduction on thermal expansion of magnetite from 298 to 1173 K at different vacuum conditions. Levy, Davide; Artioli, Gilberto; Dapiaggi, Monica. Dipartimento di Scienze Mineralogiche e Petrologiche, Universita degli Studi di Torino, Turin, Italy. Journal of Solid State Chemistry (2004), 177(4-5), 1713-1716. Publisher: Elsevier Science, CODEN: JSSCBI ISSN: 0022-4596. Journal written in English. CAN 141:29346 AN 2004:243187 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract Three thermal expansion curves of natural and synthetic magnetite (Fe3O4) have been measured under different vacuum conditions (10-4 and 10-6 mbar). The different behavior in thermal expansion depends on vacuum level, which controls the partial oxidn. of the sample. If the vacuum is poor, that is in mildly oxidizing conditions, the thermal expansion curve presents a discontinuity at 875 K and the samples oxidizes. In non-oxidizing conditions the discontinuity is not present and the thermal expansion coeff. is markedly smaller. The exptl. curves indicate that virtually all thermal expansion data on magnetite in the literature were measured on oxidized or partially oxidized samples. Equation of state, structural behaviour and phase diagram of synthetic MgFe2O4, as a function of pressure and temperature. Levy, D.; Diella, V.; Dapiaggi, M.; Sani, A.; Gemmi, M.; Pavese, A. Dipartimento Scienze Mineralogiche e, Petrologiche-Universita degli Studi di Torino, Turin, Italy. Physics and Chemistry of Minerals (2004), 31(2), 122-129. Publisher: Springer-Verlag, CODEN: PCMIDU ISSN: 0342-1791. Journal written in English. CAN 141:57155 AN 2004:211987 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract The behavior of synthetic Mg-ferrite (MgFe2O4) has been investigated at high pressure (in situ high-pressure synchrotron radiation powder diffraction at ESRF) and at high temp. (in situ high-temp. X-ray powder diffraction) conditions. The elastic properties detd. by the third-order Birch-Murnaghan equation of state result in K0 = 181.5(± 1.3) GPa, K' = 6.32(± 0.14) and K''= -0.0638 GPa-1. The symmetry-independent coordinate of oxygen does not show significant sensitivity to pressure, and the structure shrinking is mainly attributable to the shortening of the cell edge (homogeneous strain). The lattice parameter thermal expansion is described by aa0+aa1*(T-298) + aa2/(T-298)2, where aa0 = 9.1(1) 10-6 K-1, aa1 = 4.9(2) 10-9 K-2 and aa2 = 5.1(5) 10-2 K. The high-temp. cation-ordering reaction which MgFe-spinel undergoes has been interpreted by the O'Neill model, whose parameters are a = 22.2(± 1.8) kJ mol-1 and b = -17.6(± 1.2) kJ mol-1. The elastic and thermal properties measured have then been used to model the phase diagram of MgFe2O4, which shows that the high-pressure transition from spinel to orthorhombic CaMn2O4-like structure at T < 1700 K is preceded by a decompn. into MgO and Fe2O3. Thermal expansion and excess properties of akermanite-gehlenite synthetic solid solution series. Proverbio, Marco; Dapiaggi, Monica; Artioli, Gilberto. Universita degli Studi di Milano, Dipartimento di Scienze della Terra, Milan, Italy. Materials Science Forum (2004), 443-444(EPDIC 8), 401-404. Publisher: Trans Tech Publications Ltd., CODEN: MSFOEP ISSN: 0255-5476. Journal written in English. CAN 141:231466 AN 2004:163520 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract Thermal expansion of some members of the synthetic solid soln. akermanite-gehlenite was measured in the range 25-1200°C with the aim of clarifying the behavior of this solid soln. both with respect to compn. and temp. The results confirmed the non-ideal behavior at room temp. (neg. excess molar volume), and showed a different non-ideal response at high temp. In fact, excess molar volume is different during the heating and cooling stages: for Xak < 0.5 it becomes, from almost ideal, strongly pos. at high temp., while for Xak > 0.5 it is always neg. It can then be inferred that: (i) lattice dimensions are very sensitive to cation diffusion activated by temp., and (ii) intra-cryst. partition mechanisms, and their effects on the structural features, vary as a function of compn. in the solid soln. studied. Kinetics of the decomposition of crocidolite asbestos: a preliminary real-time X-ray powder diffraction study. Gualtieri, A. F.; Levy, D.; Belluso, E.; Dapiaggi, M.. Dipartimento di Scienze della Terra, Universita di Modena, Modena, Italy. Materials Science Forum (2004), 443-444(EPDIC 8), 291-294. Publisher: Trans Tech Publications Ltd., CODEN: MSFOEP ISSN: 0255-5476. Journal written in English. CAN 140:426225 AN 2004:163467 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract This work is a preliminary kinetic study of the crocidolite decompn. followed in situ at high temp. using real time conventional powder diffraction and DTA in the temp. range 720-795°C. The data anal. using the Avrami models indicates that the rate-limiting step of the reaction is 1-dimensional ion diffusion (n=0.5) with an activation energy of 129 (10) kcal/mol. Thermal expansion in cuprite-type structures from 10 K to decomposition temperature: Cu2O and Ag2O. Tiano, Walter; Dapiaggi, Monica; Artioli, Gilberto. Dipartimento di Scienze della Terra, Universita degli studi di Milano, Milan, Italy. Journal of Applied Crystallography (2003), 36(6), 1461-1463. Publisher: Blackwell Publishing Ltd., CODEN: JACGAR ISSN: 0021-8898. Journal written in English. CAN 140:118103 AN 2003:913743 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract The thermal expansion of two isostructural oxides, Cu2O and Ag2O, has been measured from 10 K to their resp. decompn. temps. by means of high-resoln. x-ray powder diffraction. The thermal behaviors of the two oxides are different. Cuprite has a neg. thermal expansion up to about 200 K, and above this temp. it becomes pos. Ag2O, on the other hand, has a neg. thermal expansion up to its decompn. temp. A comparison with EXAFS data in the same temp. range shows that the obsd. difference between the thermal expansion regimes of the two compds. can be ascribed to the vibrational behavior of the Cu and Ag atoms and, in the ultimate anal., to the different rigidities of the metal-oxygen bonds. Phase transformations and reaction kinetics during the temperature-induced oxidation of natural olivine. Gualtieri, Alessandro F.; Gemmi, Mauro; Dapiaggi, Monica. Dipartimento di Scienze della Terra, Universita di Modena e Reggio Emilia, Modena, Italy. American Mineralogist (2003), 88(10), 1560-1574. Publisher: Mineralogical Society of America, CODEN: AMMIAY ISSN: 0003-004X. Journal written in English. CAN 139:294758 AN 2003:810878 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract This work describes the sequence of transformations and their reaction kinetics during the oxidn. of olivine in air at high temp. A natural olivine sample from the layered series of the Ivrea-Verbano igneous complex (Western Alps, Italy) was heated in the temp. range 25-1300 °C in air and investigated by in situ, real time powder X-ray diffraction (PXRD). The evolution of the peaks (measured integrated intensities) was followed in non-isothermal conditions using variable heating rates (b = 20, 22, 25, 27, and 30 °C/min). The total time of the expts. ranged from about 256 (b = 30 °C/min) to 277 (b = 20 °C/min) min including the time for the data collections. An addnl. isothermal run was performed at 800 °C. The anal. of the kinetic data was attempted with the use of different equations including the classical Avrami theory for solid-state reactions. The kinetic results were confirmed by independent exptl. data from electron microscopy (SEM, TEM). In the transformation sequence, hematite appears at about 600 °C producing amorphous segregations, of silica that later recombine with forsterite to form pyroxene. Hematite is stable up to 1130 °C where it is transformed into magnetite. The rate limiting step for the formation of hematite is a two-dimensional diffusion with const. or decelerating nucleation rate and apparent activation energy of 15 kcal/mol. The concn. of Fe3+ in Fe-rich regions favors the heterogeneous nucleation of hematite, which may take place on existing defects or at the grain boundaries with impurity phases such as serpentine. At 1130 °C, magnetite is formed at the expenses of hematite, with a contracting vol. interface-controlled reaction in two or three dimensions with an apparent activation energy of 30-31 kcal/mol. The hematite to magnetite transformation is direct, without a metastable amorphous intermediate. It is described by the "shrinking core model," with the formation of a magnetite outer layer at the surface of the hematite particles that proceeds toward the core of the reacting hematite by diffusion of the oxygen throughout the newly formed magnetite layer. Its rate is limited by the advancement of the reaction front. The rate-limiting step for the formation of pyroxene is two-dimensional diffusion with decelerating nucleation rate with an apparent activation energy of 29 kcal/mol. The crystal chemistry of julgoldite-Fe3+ from Bombay, India, studied using synchrotron X-ray powder diffraction and 57Fe Moessbauer spectroscopy. Artioli, G.; Geiger, C. A.; Dapiaggi, M.. Dipartimento di Scienze della Terra, Universita di Milano, Milan, Italy. American Mineralogist (2003), 88(7), 1084-1090. Publisher: Mineralogical Society of America, CODEN: AMMIAY ISSN: 0003-004X. Journal written in English. CAN 140:29570 AN 2003:540098 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract The crystal structure of julgoldite-Fe3+ from Bombay, India, was investigated by 57Fe Moessbauer spectroscopy and synchrotron X-ray powder diffraction. Only ferric iron was detected in the Moessbauer measurements and it occurs at two different octahedral sites in the at. ratio 20:80. Based on Rietveld refinements, the Fe3+ cations are located at the X- and Y-octahedral sites with at. percentages of about 25% and 75%, resp. The resulting chem. formula of the Bombay julgoldite sample is Ca8(Fe3+2.7Al1.1Mg0.2) (Fe3+8.0)Si12O42(OH)14. The oxidn. state of Fe is not the same as that arrived at through simple crystal-chem. considerations. Such anal. cannot give quant. results for the valence state of mixed-valence cations in pumpellyite-type minerals and their intracryst. partitioning behavior. Assignments of the Moessbauer absorption doublets and an anal. of Fe-intracryst. partitioning behavior are discussed with ref. to previous works on different pumpellyite-type minerals. The thermal behavior of cuprite: an XRD-EXAFS combined approach. Dapiaggi, M.; Tiano, W.; Artioli, G.; Sanson, A.; Fornasini, P. Dipartimento di Scienze della Terra 'Ardito Desio', Universita di Milano, Milan, Italy. Nuclear Instruments & Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms (2003), 200 231-236. Publisher: Elsevier Science B.V., CODEN: NIMBEU ISSN: 0168-583X. Journal written in English. CAN 138:392340 AN 2003:64692 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract Cuprite (Cu2O) is a low thermal expansion material with a neg. thermal expansion coeff. below room temp. Its peculiar thermal behavior encompasses the increase of the shear modulus with increasing temp., and the presence of rather intense symmetry-forbidden eeo reflections below room temp. The thermal expansion of cuprite was studied at low temp. (between 5 and 298 K) by high-resoln. (10-5 A) x-ray powder diffraction at European Synchrotron Radiation Facility (Grenoble, BM16) and extended x-ray absorption fine structure (EXAFS) (BM29). Neg. thermal expansion is confirmed up to 200 K, by EXAFS as well as by XRD measurements, and no sign of transition was found in XRD data. The comparison between EXAFS and XRD results provides a valuable insight into vibrational behavior of cuprite at low temp. A newly developed high-temperature chamber for in situ x-ray diffraction: setup and calibration procedures. Dapiaggi, Monica; Artioli, Gilberto; Petras, Laszlo. Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Milan, Italy. Rigaku Journal (2002), 19(1), 35-41. Publisher: Rigaku Corporation, CODEN: RIJOFV ISSN: 0913-543X. Journal written in English. CAN 137:223804 AN 2002:579683 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract A new chamber for high temp. powder diffraction (PAP1600) was developed based on the principles of the PMP1600 chamber. The implementation and the calibration procedures are described, together with some of the possible applications in materials science. Reliability and accuracy of environmental analytical data on moss samples: an inter-laboratory comparison. Dapiaggi, M.; Leva, F.; Rabuffetti, D.; Ayrault, S.; Gaudry, A.; Cenci, R. M. WS Unit, Joint Research Centre, Environment Institute, Ispra, Italy. Environmental Technology (2001), 22(10), 1183-1192. Publisher: Selper Ltd., Publications Division, CODEN: ENVTEV ISSN: 0959-3330. Journal written in English. CAN 136:251512 AN 2001:906353 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract An inter-comparison exercise was performed between 2 labs. on mineralized moss samples. Ten samples, 3 certified ref. materials (CRM 61, CRM 62, CRM 482) and 5 blanks were mineralized independently in the 2 labs. and then analyzed using different methods (at. absorption spectroscopy [AAS], inductively coupled plasma-mass spectrometry [ICP-MS], and instrumental neutron activation anal. [INAA]). Elements analyzed were Cd, Cr, Cu, Fe, Ni, and Pb. Accuracy tests showed that, for AAS, relative std. deviations for 5 repetitions of the same sample were from 0.2% for Cd to 2.9% for Cr; concns. detd. for ref. materials were within 1 std. deviation from certified values, with the exception of Cr and Cd for CRM 482. Statistical anal. was performed with a simple linear regression and a Student t-test, accounting for the possible effect of the mineralization procedure and anal. method, to evaluate their reliability. Results showed >78% of regressions had a correlation coeff. higher than 0.750 and 83% of slopes were not different from one with a level of significance of 0.01. Afterward, measurement precision was evaluated using max. likelihood; normalized errors showed ICP-MS performed better on most elements (except Fe) and both the mineralization procedures gave satisfactory results. The 2 labs. produced reliable results. Fe-Doped Zirconium Oxide Produced by Self-Sustained High-Temperature Synthesis: Evidence for an Fe-Zr Direct Bond. Ghigna, Paolo; Spinolo, Giorgio; Anselmi-Tamburini, Umberto; Maglia, Filippo; Dapiaggi, Monica; Spina, Gabriele; Cianchi, Luciano. Dipartimento di Chimica Fisica, Universita di Pavia, Pavia, Italy. Journal of the American Chemical Society (1999), 121(2), 301-307. Publisher: American Chemical Society, CODEN: JACSAT ISSN: 0002-7863. Journal written in English. CAN 130:104178 AN 1999:3580 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract The local structure of iron in Fe-doped cubic ZrO2 produced by combustion synthesis was studied by Mossbauer spectroscopy and Fe-K edge extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES). Iron is in its II oxidn. state and occupies two different sites of the fluorite ZrO2 structure, both assocd. with some amt. of disorder. One of the sites was identified with the regular Zr position in 0,0,0, thus giving rise to substitutional Fe''Zr (i.e., Fe atoms occupying the regular Zr position, with a net 2-charge, with respect to the lattice) defects, while the other site was identified with the normally empty position at 1/2,1/2,1/2, thus giving rise to interstitial Fei.bul..bul. (i.e., Fe atoms occupying an interstitial position, with a net 2+ charge, with respect to the lattice) defects. For this last site, there is a short Fe-Zr distance (2.64 .ANG.). This result, coupled to the quite small value of the Debye-Waller factor for this distance, gives evidence of a direct Zr-Fe metal-to-metal bond. Computer simulation approach to reliability and accuracy in powder diffraction structure refinement. Dapiaggi, M.; Anselmi-Tamburini, U.; Spinolo, G. Dep. Phys. Chem., INCM and CSTE/CNR, Univ. Pavia, Pavia, Italy. Journal of Applied Crystallography (1998), 31(3), 379-387. Publisher: Munksgaard International Publishers Ltd., CODEN: JACGAR ISSN: 0021-8898. Journal written in English. CAN 129:237887 AN 1998:517071 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract The frequency distribution of different parameters of a powder pattern can be directly sampled by analyzing a population of simulated patterns produced by adding computer-generated noise to an exact calcd. pattern. The procedure gives statistical estimators (mean, dispersion, correlations) of the parameters, which can be compared to the corresponding single-pattern ests. to test the performance of a strategy for data acquisition and structure anal., to evaluate the bias introduced by wrong models and to clarify the amt. of information actually contained in an exptl. pattern. Examples are given for the simple structure of an almost completely inverted spinel (NiAl2O4). Microstructural characterization of some hydrothermal synthetic kaolinites: Preliminary data. Dapiaggi, M.; Fiore, S.; Huertas, F. J.; Setti, M. Dipartimento di Scienze della Terra, Universita di Pavia, Italy. Materials Science Forum (1994), 166-169(Pt. 2), 725-30. Publisher: Trans Tech, CODEN: MSFOEP ISSN: 0255-5476. Journal written in English. CAN 122:217708 AN 1995:392068 CAPLUS (Copyright (C) 2007 ACS on SciFinder (R)) Abstract Some methods of microstructural characterization were applied to a group of kaolinites synthesized by hydrothermal method with different conditions of synthesis. The variables taken into account were: chem. compn. (Si/Al ratio), crystn. temp., and crystn. time. The samples were studied by x-ray powder diffraction to obtain degree of crystallinity (Hinckley index), crystal size using Scherrer equation and a single-peak Fourier method on the (001) reflection, and cell parameters. The crystal size of the samples was also calcd. using the integrated intensities found using WPPF, a full-pattern-fitting program. The results showed a general increase in the crystal size of the samples with increasing crystn. time and temp. for the higher Si/Al ratio, while a Si/Al ratio <1 favored the formation of a higher quantity of kaolinite, but with a smaller crystal size. Therefore, using these methods, it could be possible to follow the kaolinite crystn., in order to find the best way to produce samples with given pre-requisites.