Journal Of Solid State Chemistry Research Articles

The Evaluation of Formation and Bioactivity of New Sol-gel Bioactive Glass

In this paper, three ceramic compositions 50SiO2-50CaO (A), 45SiO2-45CaO-10P2O5 (B) and 40SiO2-40CaO-20P2O5 (C) (wt %) were synthesized by using the sol-gel technique. XRD analysis demonstrates that only sample C can form the glass material. Treated temperatures and heated times were also evaluated. Analysis data showed that the bioglass 40SiO2-40CaO-20P2O5 (wt %) can successfully elaborate when the ceramic powder heated at 750 oC for 3 hours. ‘‘In vitro’’ experiment was effectuated to investigate the bioactivity of bioglass 40SiO2-40CaO-20P2O5 by soaking powder samples in SBF solution. Obtained result confirmed the formation of hydroxyapatite (HA) phase on glass’s surface after 15 days of immersion, in which HA formation orients following (211) and (222) miller planes in crystalline structure of HA phase.
 Keywords
 Sol-gel; bioglass; hydroxyapatite; SBF; bioactivity
 References
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Effects of Cr Doping on Physical and Electrochemical Properties of Li2MnSiO4 Cathode Materials for Li-Ion Batteries

INTRODUCTION Lithium metal othosilicate (Li2 MSiO4, where M = Fe, Mn, Co or Ni) has currently attracted a good deal of interest as a high voltage positive electrode material due to its high theoretical charge and discharge capacities of 330 mAh g-1 and high voltage up to 5.1 V. Such high capacity arises from the ability to extract two lithium ions per one transition metal. However, this class of material has been reported to exhibit low conductivity and poor cycling performance due to structural instabilities with the transition from orthorhombic to monoclinic phase during charge and discharge.[1] Mn-site doping with transition metal ions (Ni2+, Cr2+, Ti4+, V5+) or the aliovalent ions (Al3+, Ga3+) can induce defects in the lattice and stabilize overall structure. Since the structural instability is generally caused by the collapse of MnO4 coordination structure to MnO6, works have been done to retain the MO4 structure.[2] A study by Cheng, et al. reported that substituting Cr on Mn site partly helps retain M-O coordination of MnO4.[3] In this study, our research focuses on stabilizing an othosilicate-based positive lithium-ion battery electrode material, specifically, lithium manganese silicate (Li2MnSiO4) via partial substitution of Mn with Cr up to 15 mol%. To understand the effect of Cr doping on structural evolution during the charge/discharge process, the in situ XRD is also conducted to understand the correlation between the electrode material’s structural and electrochemical behavior. EXPERIMENTAL Li2Mn1-x Cr x SiO4 (x = 0 - 0.15) were prepared by with an acetic acid-assisted sol–gel method. The dried materials were fired at 800°C for 6 hours in Ar atmosphere. Structural properties of the synthesized samples were studied by X-ray diffraction (Rigaku TTRAXII) using Cu-Kα (λ=1.5418 Å) radiation. Particle morphologies and size of the resulting compounds were observed using a field emission scanning electron microscope (FE-SEM, Hitachi SU8030). Electrochemical characterizations were performed by in Swagelok® cells. Active material, conductive carbon black and polyvinylidene fluoride (PVDF) were mixed in the ratio of 87:5:8 by weight. Galvanostatic charge-discharge cycling was done between 1.5-4.8 V at 0.05C using a MACCOR Series 4000 at room temperature. RESULTS AND DISCUSSIONS Figure 1 shows XRD patterns of the synthesized Li2Mn1-x Cr x SiO4 where Cr = 0 - 0.05. Main diffraction peaks could be indexed as an orthorhombic unit cell with a space group Pmnb. Appearance of the evidence of small amount of monoclinic phase, MnO and Li2SiO3. There is no obvious evidence of a phase containing Cr. With an increasing the Cr doping ratio, the unit cell volume slightly increases from 339.52 Å3 to 339.79 Å3 as expected due to larger ionic radii of Cr2+ than Mn2+ indicating the substitution of Cr into the structure of Li2MnSiO4. Electrochemical performance in relations to structural stability of Li2Mn1-x Cr x SiO4 will be discussed in the meeting. REFERENCES [1] R. Dominko, M. Bele, A. Kokalj, M. Gaberscek, J. Jamnik, Journal of Power Sources, 2007, 174, 457-461. [2] V.V. Politaev, A.A. Petrenko, V.B. Nalbandyan, B.S. Medvedev, E.S. Shvetsova, The Journal of Solid State Chemistry, 2007, 180, 1045–1050. [3] H.M. Cheng, S.X. Zhao, X. Wu, J.W. Zhao, L. Wei, Applied Surface Science, 2018, 433, 1067-1074. Fig. 1 Powder X-ray diffraction patterns of Li2Mn1-x Cr x SiO4 (x = 0, 0.025 and 0.05). Figure 1

State-of-the-Art La0.6Sr0.4Co0.2Fe0.8O3-δ Cathode for SOFC: Microstructural and Electrochemical Properties

Solid Oxide Fuel Cells (SOFCs) have drawn much attention because they convert chemical energy into electrical energy efficiently in eco-friendly way. The performance of a SOFC depends on several combined factors in each cell compartments (i.e. anode, cathode and electrolyte). Especially the polarization resistance of the cathode becomes significant for intermediate temperature operations (500 – 700 °C). For this reason, the cathode reaction kinetics and influence of microstructure of state-of-the-art cathode materials have been extensively researched through comparative experimental studies and numerical simulations in the literature. Porous cathodes comprising mixed ionic-electronic conductors (MIEC) are commonly preferred in these energy conversion devices operating at intermediate temperature. They grabbed particular attention since the oxygen reduction reaction (ORR) is extended at the electrode/electrolyte interface, beyond the triple phase boundary (TPB) points. Earlier in our group, reaction kinetics of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) deposited by electrostatic spray deposition (ESD) technique was studied in two different microstructures, i.e; the coral and columnar-types [1-3]. Thanks to nanostructured microstructure features, one of the lowest polarization resistance (Rpol) values compared to literature was achieved. The present study concerns the influence of the thickness of columnar LSCF films on the area specific polarization resistance (ASR) of the cathode. Symmetrical cells of LSCF were deposited on dense Ce0.9Gd0.1O2-δ (CGO) electrolyte. The cathodes were consisted of double layer films of LSCF deposited sequentially by ESD technique as cathode functional layer (CFL) and by screen printing (SP) technique as current collecting layer (CCL) as shown in Figure 1. The thickness of CFL was varied between 0.5 and 18 μm by controlling the time of ESD deposition from 20᾿, 40᾿, 1h, 1h45᾿, 3h and 4h30’. Thickness of CCL was varied by SP from 20 to 50 μm. The resulting electrode thicknesses and microstructures were investigated by scanning electron microscope and microstructural parameters (porosity, specific surface area) were calculated by 3D reconstruction of the images obtained by FIB/SEM tomography. The electrode performance in terms of ASR as well as current constriction effects were monitored by electrochemical impedance spectroscopy (EIS). The results are discussed in terms of microstructure, adherence at the electrode/electrolyte interface, conductivity and optimized cathode performance. The hierarchical porous character of CFL is highlighted with macro porosity separating the columns and nano porosity within the columns [4]. The CCL provides a flatter surface than the CFL, thus improving the current collection by increasing the contact points between the surface and current collecting grid. We have shown that the electrochemically active layer in LSCF nanostructured columnar cathodes deposited by ESD concentrates on only a couple hundred nanometers away from the electrode/electrolyte interface [4]. One can conclude that the optimized films require at least 4-5 µm CFL thickness and 36 µm total thickness (CFL-CCL). In this geometry, the optimized ASR value of 0.065 Ω cm2 at 600 °C was achieved for double layer cathode characterized by a porosity amount of approximately 22 % and a specific surface area of 19 μm-1 with a columnar-type microstructure [4]. This ASR value is still amongst the highest specific surface area values achieved for SOFC cathodes. D. Marinha, C. Rossignol, E. Djurado, Influence of electrospraying parameters on the microstructure of La0.6Sr0.4Co.2Fe.8O3- d films for SOFCs, Journal of Solid State Chemistry 182 (2009) 1742–1748.D. Marinha, L. Dessemond, J.S. Cronin, J.R. Wilson, S.A. Barnett, E. Djurado, Microstructural 3D reconstruction and performance evaluation of LSCF cathodes obtained by electrostatic spray deposition, Chem. Mater. 23 (2011) 5340-5348.D. Marinha, J. Hayd, L. Dessemond, E. Ivers-Tiffée, E. Djurado, Performance of (La,Sr)(Co,Fe)O3−x double-layer cathode films for intermediate temperature solid oxide fuel cell, J. Power Sources. 196 (2011) 5084–5090.Celikbilek O., Jauffres D., Siebert, E., Dessemond L., Burriel M., Martin C.L., Djurado E., Rational Design of Hierarchically Nanostructured Electrodes for Solid Oxide Fuel Cells, J. Power Sources. 333 (2016) 72–82. Figure 1

Coordination polymers and metal-organic frameworks: materials by design.

The field of coordination polymers and metal–organic frameworks (MOFs) has evolved over a period of approximately 25 years to a stage where it is one of the most widely investigated areas of materials chemistry. The field has impacted many areas of science including commercial applications from

Amorphous Silicon Nitride Thin Film Anodes for Li-Ion Batteries

Silicon has proven to have a great potential as anode material for lithium ion batteries due to its high theoretical capacity, however; there are several obstacles that need to be overcome in order to make it a commercially viable option. Two of the main issues stem from the fact that silicon undergoes a large volume change during lithiation and delithiation (1). This makes forming a stable solid electrolyte interphase (SEI) difficult, resulting in a continuous loss mechanism of electrolyte and lithium as SEI is formed and broken each cycle. Uneven expansion and contraction causes the silicon to fracture, both exposing new surface on which more SEI might form, as well as electrically disconnecting material from the electrode, rendering it inactive. In this work we investigate the use of amorphous silicon nitride as an alternative to pure silicon anodes. Silicon nitride is believed to form lithiated silicon and lithium nitride or one of several lithium silicon nitride ternary phases during the initial lithiation (2, 3). The resulting material is therefore believed to combine the high lithium ion conductivity of lithium containing nitrides with the high capacity of silicon. In a sufficiently fine structure, we hypothesize the silicon would be able to expand and contract with little to no fracturing owing to dimensional stabilization, short diffusion distances, and fast lithium diffusion in the surrounding lithium nitride, resulting in a high cycling stability. We investigate this theory using a thin film electrode system. For this purpose, a-SiNx:H thin films are deposited on copper foil substrates using plasma enhanced chemical vapor deposition (PECVD) with silane (SiH4) and ammonia (NH3) as precursors. By changing the flow ratio of the precursor gases in the plasma, SiNxfilms with five different compositions were made (x = 0, 0.36, 0.63, 0.88 and 1.00). Films of different thicknesses were also made to be able to separate surface and bulk irreversible capacities, and to evaluate the kinetics of the material. Ellipsometry and transmission electron microscopy (TEM) were used to determine the thickness, composition, structure and quality of the pristine films. Electrochemical tests were conducted in 2032 coin cells, with a lithium metal counter electrode, using a commercial electrolyte with 5% FEC and 1% VC, and cycling is conducted between 50 mV and 1 V. The variation of the first cycle specific charge capacity as function of different stoichiometries is studied, as well as the stability of the resulting material. Figure 1 shows the charge capacity and Coulombic efficiency of three 40 nm thick SiN1.00 thin film electrodes which were primed at C/6 for 6 cycles and cycled at 1C for 750 cycles. These had an average charge capacity of 1126±40 mAh/g on the first 1C cycle, and experienced only a slight increase in capacity during the first 230 cycles, peaking at 1259±33 mAh/g before leveling out. After finishing 750 cycles the cells still retained an average capacity of 1245±19 mAh/g. Voltage-capacity curves for a selection of cycles can be seen in the figure 2, showing the large difference between the first conversion cycle and the subsequent cycles. By comparing the first cycle irreversible capacities of SiN1.00 films with different thicknesses (40 nm, 80 nm, 120 nm, 160 nm, and 200 nm), it has been determined that the conversion reaction of this nitride composition consumes approximately 565 mAh/g, while the initial formation of SEI consumes 0.021 mAh/cm2. These experiments also demonstrated that increasing the thickness of the films had no significant adverse effects on their performance, but rather improved the first cycle irreversible capacity and increased the long term (cycles 10-100) average Coulombic efficiency from 99.6% (40 nm) to >99.9% (80 nm, 120 nm, 160 nm and 200 nm). 1. Kasavajjula U, Wang C, Appleby AJ. Nano-and bulk-silicon-based insertion anodes for lithium-ion secondary cells. Journal of Power Sources. 2007;163(2):1003-39. 2. Ahn D, Kim C, Lee J-G, Park B. The effect of nitrogen on the cycling performance in thin-film Si1−xNx anode. Journal of Solid State Chemistry. 2008;181(9):2139-42. 3. Suzuki N, Cervera RB, Ohnishi T, Takada K. Silicon nitride thin film electrode for lithium-ion batteries. Journal of Power Sources. 2013. Figure 1

Optimization of Process Parameters during Solid State Synthesis of LiMn2O4 as Cathode Material for Lithium-Ion Batteries

One focus of the present research of Lithium-Ion Batteries is the development of higher energy and higher power density materials. Spinels like LiMn2O4 exhibit a potential of 4.1 V v.s. Li/Li+ that can be further increased by substitution of Mn by transition metals like Ni. Those substituted spinels like LiMn1.5Ni0.5O4 are highly interesting cathode-materials for the high-energy range up to 5 V. The synthesis of spinels via a solid state route enables the production of high amounts up to 100 g with inexpensive starting materials and a combined step for milling and homogeni­zation of the raw materials. However, the solid state synthesis is a challenging approach regarding an adequate homogenization and a potential eva­po­ra­tion of Li during calcination[1]. The present work aims the characterization of calcined cathode-materials to control the processing parameters in order to prepare single-phase spinel materials. Therefore, different compositions of LixMn2O4 have been synthesized from Li2CO3 and MnO2 as starting materials, applying different milling parameters and calcination conditions. The calcined powders were then characterized by powder diffraction (XRD) and electron-paramagnetic-resonance spectroscopy (EPR). It is known that Li2MnO3 might be formed during the calcination process as an undesirable lithium-rich secondary phase[2]. Thus, particular attention has been paid on this phase. The formation of Li2MnO3 may occur by non-homogeneous mixing or remaining coarse particles of Li2CO3 in the powder mixture. The EPR is a highly sensitive method to obtain even small amounts of Li2MnO3 besides LiMn2O4in the calcined product and is therefore highly interesting for this application. [1] Y. Lee, The Effects of Lithium and Oxygen Contents Inducing Capacity Loss of the LiMn2O4 Obtained at High Synthetic Temperature, Journal of Electroceramics, 9, 209 – 214, 2002. [2] V. Massarotti et al., Stoichiometry of Li2MnO3 and LiMn2O4 Coexisting Phases: XRD and EPR Characterization, Journal of Solid State Chemistry, 128, 80 – 86, 1997.

Porous Li2MTi3O8 (M = Zn, Co) Flake Particles with Enhanced Lithium-Storage Properties

Compared with the Li4Ti5O12 anodes, the spinel structure Li2MTi3O8 (M = Zn, Co, Mg, Cu) has recently attracted increasing attention for LIBs (lithium batteries) because of its high specific lithium storage capacity (>200 mA h g-1) and cycling stability.[1, 2] In this paper, we reported a novel synthetic method of porous Li2MTi3O8 (M = Zn, Co) flake particles (f-Li2MTi3O8) by a one-step solution-combustion. In relation to the conventional synthesis methods, this route is easy to control with less laborious procedures and no need for certain precursor. Moreover, the combustion synthesis in liquid phase ensures excellent homogeneity of the product with a high surface area.As shown in Figure 1, both of the Li2MTi3O8 samples prepared via the combustion method have flake structure and its secondary particles compose of nanometer-size primary particles with embedded nano and micro pores. These pores are in-site obtained due to concomitant formation of Li2MTi3O8with vigorous evolution of large volume of gases during the combustion reaction.To evaluate the cycleability of the f-Li2MTi3O8 (M = Zn, Co) flake particles electrodes, a charging and discharging current density of 100 mA g-1 was used. Both of the samples exhibited excellent cycle stability (Figure 2). For the f-Li2ZnTi3O8 electrode, a capacity of 192 mA h g-1 could be retained after 200 cycles with a capacity retention of 81%. In the case of the f-Li2CoTi3O8 electrode, it delivered 201 mA h g-1with a high capacity retention of 89% after 200 cycles.To gain more electrochemistry properties information on the materials, the rate performance tests were carried out. Figure 3 shows the rate capabilities of the synthesized f-Li2ZnTi3O8 and f-Li2CoTi3O8 electrodes at different current rates and their rate capacities at 200th cycle was summarized in Table 1. As observed from these data, both of the two samples show the considerable cycle stability even at high current rates. And the f-Li2CoTi3O8 electrodes showed considerably higher reversible capacities and more excellent capacity retention than the f-Li2ZnTi3O8 electrodes irrespective of the rate used. Interestingly, more than 100 mA h g-1 can be retained after 200 cycles even at the current rate of 2000 mA g-1. The excellent rate performance may be attributed to the special morphology and structure.These results indicate that the as-prepared anodes with spinel flake particles have a large reversible capacity and high rate performance, which can be attributed to the 3D porous flamework structures and their intrinsic characteristics. This special 3D porous flamework structure could provide a diffusion space for lithium-ion storage and extraction from the material. In addition, the porous flamework composed of several tens of nanometers greatly decreased the diffusion distance for lithium ions and electrons in the solid state. Thus, we believe that such a facile solution-combustion method could be applied in a wide range of fields and the f-Li2MTi3O8(M = Zn, Co) could be promising anode materials for high-rate lithium batteries. Acknowledgment: High Technology Research and Development Program of China (2012AA110204), the Fujian Natural Science Foundation (2012J05028) and Electric Vehicle Project (I) of Xiamen (3502J20121002). Qian Xiao expresses her special thanks for National Found for Fostering Talents of Basic Science (J1210014). The authors also wish to express their thanks to Dr. Bo Liu for valuable suggestions.Figure 1. SEM images of (a) f-Li2ZnTi3O8 and (b) f-Li2CoTi3O8.Figure 2. Cycle performance for (a) f-Li2ZnTi3O8 and (b) f-Li2CoTi3O8 electodes for 200 cycles at low capacity rate of 100 mA g-1.Figure 3. Capacity versus cycle number plots for (a) f-Li2ZnTi3O8 and (b) f-Li2CoTi3O8electrodes for 200 cycles at different discharge current rates.Table 1 The capacities for Li2ZnTi3O8 and Li2CoTi3O8 electrodes after 200 cycles at different discharge current rates. Rate(mA g-1)40080016002000f-Li2ZnTi3O8(mA h g-1)1641007473f-Li2CoTi3O8 (mA h g-1)175161141101 References [1]. N.Reeves, D.Pasero,A.R.West,Journal of Solid State Chemistry. 2007, 180, 1894.[2]. L.Wang, L.J. Wu, Z.H. Li, G.T. Lei, Q.Z. Xiao, P. Zhang, ElectrochimicaActa. 2011,56, 5343.

Phase transitions and electrical properties of Bi 2O 3 up to 2.5 GPa

The effect of pressure between 0.5 and 2.5 GPa on the phase transitions and electrical conductivity of Bi 2O 3 has been studied by the use of electrical impedance spectroscopy. By analyzing the Arrhenius plots gained from the electrical conductivity measurements in the temperature range of the α – δ phase transition, the pressure dependence of the critical temperature ( T c ) and activation energy were determined. The measurements demonstrated that the pressure effect between 0.5 and 2.5 GPa has a significant effect on the α – δ phase transition temperature in Bi 2O 3, and the increase of T c for the α – δ phase transformation is more than 60 ∘C compared to previous research with DTA [E.M. Levin, R.S. Roth, Polymorphism of Bismuth Sesquioxide. I. Pure Bi 2O 3, Journal of Research of the National Bureau of Standards–A. Physics and Chemistry 68A (2) (1964) 189–195]. The activation energies of electric conductivity in α – δ phases seem not to be affected by raising the pressure. During cooling, the δ – α transformation occurred approximately at the temperature corresponding to T c monitored during the heating cycle. Neither a δ – β , a δ – γ phase transformation nor a hysteresis effect has been found under pressure, which is in contrast with normal pressure studies that used DTA, electrical conductivity measurements and XRD [E.M. Levin, R.S. Roth, Polymorphism of Bismuth Sesquioxide. I. Pure Bi 2O 3, Journal of Research of the National Bureau of Standards–A. Physics and Chemistry 68A (2) (1964) 189–195; H.A. Harwig, A.G. Gerards, Electrical Properties of the α -, β -, γ - and δ -Phases of Bismuth Sesquioxide, Journal of Solid State Chemistry 26 (1978) 265–274].

The surface activity of ultrafine particles

Within the last 20 years, advances in characterization methods, particularly in the field of high–resolution electron microscopy, have made it possible to probe the surface and internal structure of sub–100 nm particles, or nanoparticles. Such studies have indicated conclusively that surface–energy considerations in metal nanoparticles cause these particles to adopt structures which only approximate to close packing but are terminated by close–packed faces. In oxides, where stoichiometry must be maintained, the adoption of low–index crystallographic faces almost invariably necessitates the introduction of cation or anion vacancies, and both have been observed. In such cases, the structure at the edges of the particles differs greatly from that of bulk phases, and it seems highly probable that the physical and chemical properties of these particles are also different. In certain cases it appears that new structural types, found only in nanoparticulate form, may exist. The significance of these findings, particularly as regards their relevance to particulate pollutants in the atmosphere, may be of great interest.

Ab initio perturbed ion description of the equation of state and a high pressure phase transition of Al 2O 3

The electronic structure, equilibrium geometry, and equation of state of Al 2O 3 in the α — Al 2O 3 and Rh 2O 3(II) phases have been determined by means of the ab initio perturbed ion method augmented by a recently developed non-empirical Debye-like model for describing the vibrational thermal effects. A systematic multidimensional optimization of the structural parameters has been completed for the two phases from zero to 2200 K, and pressures up to 70 GPa for the α — Al 2O 3 phase, and 20 GPa for the high pressure phase. Our structural results are in good agreement with the experimental information available. Although the α — Al 2O 3 phase is more stable in the static ( p = T = 0) description, a pressure-induced phase transition is detected at room temperature near 4 GPa. The critical pressure p c increases very slightly with temperature, being about 5.5 GPa at 1000 K. This value is consistent with the phase transition found in Rh 2O 3 by Shannon and Prewitt [ Journal of Solid State Chemistry 2, (1970) 134] at p c 6.5 GPa. Furthermore, the α — Al 2O 3 phase shows a slight pressure-induced anisotropy, since the c a ratio decreases from 2.638, at zero pressure, to 2.474 at 70 GPa. Also, according to our calculations, the crystal maintains its symmetry and reduces moderately its compressibility in the high temperature regime. The present methodology gives detailed structural information on phase transitions of the type described in this work, as well as a meaningful description of the high pressure phase, a task rather difficult to undertake in the laboratory.

Molecular dynamics of tetrakis(trimethylsilyl)silane in the solid state: an incoherent quasi-elastic neutron scattering investigation

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Jones Matthew J. , Guillaume François , Harris Kenneth D. M. and Dianoux Albert-josé 1996Molecular dynamics of tetrakis(trimethylsilyl)silane in the solid state: an incoherent quasi-elastic neutron scattering investigationProc. R. Soc. Lond. A.452701–714http://doi.org/10.1098/rspa.1996.0035SectionRestricted accessArticleMolecular dynamics of tetrakis(trimethylsilyl)silane in the solid state: an incoherent quasi-elastic neutron scattering investigation Matthew J. Jones Google Scholar Find this author on PubMed Search for more papers by this author , François Guillaume Google Scholar Find this author on PubMed Search for more papers by this author , Kenneth D. M. Harris Google Scholar Find this author on PubMed Search for more papers by this author and Albert-josé Dianoux Google Scholar Find this author on PubMed Search for more papers by this author Matthew J. Jones Google Scholar Find this author on PubMed Search for more papers by this author , François Guillaume Google Scholar Find this author on PubMed Search for more papers by this author , Kenneth D. M. Harris Google Scholar Find this author on PubMed Search for more papers by this author and Albert-josé Dianoux Google Scholar Find this author on PubMed Search for more papers by this author Published:01 January 1996https://doi.org/10.1098/rspa.1996.0035AbstractIncoherent quasi-elastic neutron scattering (IQNS) spectroscopy has been used to investigate the dynamic properties of solid tetrakis(trimethylsilyl)silane (Si[Si(CH3)3]4). This material is known to undergo a phase transition to a plastic crystal phase at ca. 240 K. The evolution of the elastic intensity as a function of temperature between 4.5 K and 300 K indicates three distinct dynamic regimes, with changes in dynamic behaviour at 120 K and 240 K. Detailed consideration of quasi-elastic broadening in the IQNS spectra (including consideration of the effects of multiple scattering) has established the following information on the dynamic processes occurring on the experimental timescale within each of these regimes. Below 120 K, there are only molecular vibrational motions with no quasi-elastic broadening in the IQNS spectra. Between 120 K and 240 K, the dynamic properties are interpreted as three-fold jumps of the CH3 group about the Si—CH3 bond. Above 240 K, two different dynamic models have been considered: (a) combined three-fold jumps of the CH3 group about the Si—CH3 bond and three-fold jumps of the Si(CH3)3 group about the Si—Si(CH3)3 bond; and (b) isotropic reorientational diffusion. Model (a) fails to fit the IQNS spectra, whereas model (b) provides an acceptable fit to the IQNS spectra in the temperature range investigated (245-300 K) for the high-temperature phase. The isotropic reorientational diffusion is considerably slower than the threefold jumps of the CH3 group about the Si—CH3 bond.FootnotesThis text was harvested from a scanned image of the original document using optical character recognition (OCR) software. As such, it may contain errors. Please contact the Royal Society if you find an error you would like to see corrected. Mathematical notations produced through Infty OCR. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by Zhou Y, Patterson R, Williams P, Kariuki B, Hughes C, Samanta R, Devarapalli R, Reddy C, Apperley D and Harris K (2019) Temperature-Dependent Structural Properties, Phase Transition Behavior, and Dynamic Properties of a Benzene Derivative in the Solid State, Crystal Growth & Design, 10.1021/acs.cgd.8b01775, 19:4, (2155-2162), Online publication date: 3-Apr-2019. Desmedt A, Kitchin S, Harris K, Guillaume F, Tykwinski R, Xu M and Gonzalez M (2008) Dynamic Properties of Solid Ammonium Cyanate, The Journal of Physical Chemistry C, 10.1021/jp8042889, 112:40, (15870-15879), Online publication date: 9-Oct-2008. Tutoveanu G, Kitchin S, Harris K and Müller J (2003) Molecular motion in solid ammonia trimethylalane, Journal of Solid State Chemistry, 10.1016/S0022-4596(03)00355-4, 176:1, (120-126), Online publication date: 1-Nov-2003. This Issue08 March 1996Volume 452Issue 1946 Article InformationDOI:https://doi.org/10.1098/rspa.1996.0035Published by:Royal SocietyPrint ISSN:1364-5021Online ISSN:1471-2946History: Manuscript received03/04/1995Manuscript accepted27/06/1995Published online01/01/1997Published in print01/01/1996 License:Scanned images copyright © 2017, Royal Society Citations and impact

Experimental studies of Earth's deep interior: accuracy and versatility of diamond-anvil cells

Phase equilibria, chemical reactions, equations of state and elasticity investigated at high P-T in candidate materials for the mantle and the core provide an experimental basis for modelling the structure, dynamics and evolution of the Earth's deep interior. During the past three decades, diamond-anvil cells have been developed for experimental simulation of the pressure conditions of the entire Earth in the laboratory. Simultaneous high temperatures have been generated with various heating techniques. Physical and chemical properties of materials have been determined in situ at high P-T with microsampling techniques. Further improvements in accuracy and versatility of these measurements are essential for resolving key geophysical problems. Some recent developments in our laboratory are summarized, and assessments of the present status and immediate future of the field are offered.