FREEZING POINT DEPRESSIONS IN SODIUM FLUORIDE. III. EFFECTS OF 3d TRANSITION METAL DIFLUORIDES AND CADMIUM FLUORIDE

Measurements have been made of the electrical conductance of crystals and melts of sodium fluoride and of cryolite. The contraction in volume when these melts crystallize has also been determined. A new transition at about 880° C has been detected in cryolite. The new results have been combined with previous information on the crystal structures at various temperatures, and on the densities and viscosities of the melts as aluminium fluoride is added progressively to sodium fluoride. Entropies of fusion, and freezing-point depressions when various ions are added to the melts have also been considered. Various findings suggest that the complex anion [AlF 6 ] 3¯ undergoes partial dissociation to [A1F 4 ] ¯ and [F] ¯ in the melt; probably this already occurs in the crystal below the meltingpoint. Dissociation of some fluoride ions from the symmetrical [A1F 6 ] 3¯ and randomization of their positions in the crystal lattice would explain the high conductance σ S of the solid just below the melting-point, and the small increase of conductance to σ L on melting; for cryolite σ L / σ S is less than 10 compared with about 7000 for NaF. The comparatively large expansion in volume (25%) on melting cryolite is probably due to extensive formation of positional flaws.

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FREEZING POINT DEPRESSIONS IN SODIUM FLUORIDE. IV. EFFECTS OF TRIVALENT FLUORIDES

The Journal of Physical Chemistry ◽

10.1021/j100806a061 ◽

1963 ◽

Vol 67 (12) ◽

pp. 2766-2769 ◽

Cited By ~ 7

Author(s):

Stanley Cantor ◽

Wilfred T. Ward

Keyword(s):

Sodium Fluoride ◽

Freezing Point

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HREM Study of electron-induced surface radiation damage in ReO3

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087495 ◽

1991 ◽

Vol 49 ◽

pp. 636-637

Author(s):

R. Ai ◽

H.-J. Fan ◽

L. D. Marks

Keyword(s):

Transition Metal ◽

Metal Ions ◽

Metal Oxides ◽

Electron Irradiation ◽

Transition Metal Oxides ◽

Carbon Film ◽

Transition Metal Ions ◽

Surface Radiation ◽

Valence Transition ◽

Electron Microscopes

It has been known for a long time that electron irradiation induces damage in maximal valence transition metal oxides such as TiO2, V2O5, and WO3, of which transition metal ions have an empty d-shell. This type of damage is excited by electronic transition and can be explained by the Knoteck-Feibelman mechanism (K-F mechanism). Although the K-F mechanism predicts that no damage should occur in transition metal oxides of which the transition metal ions have a partially filled d-shell, namely submaximal valence transition metal oxides, our recent study on ReO3 shows that submaximal valence transition metal oxides undergo damage during electron irradiation.ReO3 has a nearly cubic structure and contains a single unit in its cell: a = 3.73 Å, and α = 89°34'. TEM specimens were prepared by depositing dry powders onto a holey carbon film supported on a copper grid. Specimens were examined in Hitachi H-9000 and UHV H-9000 electron microscopes both operated at 300 keV accelerating voltage. The electron beam flux was maintained at about 10 A/cm2 during the observation.

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Problems with oxygen analysis in the system MgO-Al2O3-SiO2 with the electron microprobe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100132753 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1624-1625

Author(s):

Michel Fialin ◽

Guy Rémond

Keyword(s):

Transition Metal ◽

Metal Oxides ◽

Transition Metal Oxides ◽

Electrostatic Charge ◽

Carbon Layer ◽

Sample Holder ◽

Rock Matrix ◽

Electrical Discharges ◽

Thin Carbon ◽

Beam Instabilities

Oxygen-bearing minerals are generally strong insulators (e.g. silicates), or if not (e.g. transition metal oxides), they are included within a rock matrix which electrically isolates them from the sample holder contacts. In this respect, a thin carbon layer (150 Å in our laboratory) is evaporated on the sections in order to restore the conductivity. For silicates, overestimated oxygen concentrations are usually noted when transition metal oxides are used as standards. These trends corroborate the results of Bastin and Heijligers on MgO, Al2O3 and SiO2. According to our experiments, these errors are independent of the accelerating voltage used (fig.l).Owing to the low density of preexisting defects within the Al2O3 single-crystal, no significant charge buildup occurs under irradiation at low accelerating voltage (< 10keV). As a consequence, neither beam instabilities, due to electrical discharges within the excited volume, nor losses of energy for beam electrons before striking the sample, due to the presence of the electrostatic charge-induced potential, are noted : measurements from both coated and uncoated samples give comparable results which demonstrates that the carbon coating is not the cause of the observed errors.

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Electron energy loss near edge structures of intermetallic alloys and grain boundaries in NiAl

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165070 ◽

1996 ◽

Vol 54 ◽

pp. 522-523

Author(s):

G.A. Botton ◽

C.J. Humphreys

Keyword(s):

High Temperature ◽

Transition Metal ◽

Energy Loss ◽

Grain Boundaries ◽

Industrial Applications ◽

Edge Structure ◽

Structural Applications ◽

Yield Behaviour ◽

Late Transition ◽

Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

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HVEM Cryomicroscopy of Frozen Hydrated PTK1 Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100181257 ◽

1990 ◽

Vol 48 (1) ◽

pp. 500-501

Author(s):

E.T. O’Toole ◽

G.P. Wray ◽

J.R. Kremer ◽

J.R. Mcintosh

Keyword(s):

Liquid Nitrogen ◽

Phase Contrast ◽

Culture Medium ◽

Low Dose ◽

Ammonium Acetate ◽

Freezing Point ◽

Voltage Electron ◽

Cold Stage ◽

Humidity Chamber ◽

Coated Carbon

Ultrarapid freezing and cryomicroscopy of frozen hydrated material makes it possible to visualize samples that have never been exposed to chemical fixatives, dehydration, or stains. In principle, freezing and cryoimaging methods avoid artifacts associated with chemical fixation and processing and allow one to visualize the specimen in a condition that is close to its native state. Here we describe a way to use a high voltage electron microscope (HVEM) for the cryoimaging of frozen hydrated PTK1 cells.PTK1 cells were cultured on formvar-coated, carbon stabilized gold grids. After three days in culture, the grids were removed from the culture medium and blotted in a humidity chamber at 35° C. In some instances, the grids were rinsed briefly in 0.16 M ammonium acetate buffer (pH 7.2) prior to blotting. After blotting, the grids were transferred to a plunging apparatus and plunged into liquid ethane held directly above its freezing point. The plunging apparatus consists of a vertical slide rail that guides the fall of a mounted pair of forceps that clamp the specimen. The forceps are surrounded by a plexiglass humidity chamber mounted over a dewar of liquid nitrogen containing an ethane chamber. After freezing, the samples were transferred to liquid nitrogen and viewed in a JEOL JEM 1000 equipped with a top entry cold stage designed and built by Mr. George Wray (Univ. Colorado). The samples were routinely exposed to electron doses of 1 e/Å2/sec, and viewed at a temperature of −150° C. A GATAN video system was used to enhance contrast and to estimate the correct amount of underfocus needed to obtain phase contrast at various magnifications. Low dose micrographs were taken using two second exposures of Kodak 4463 film. The state of the solid water in the specimen was determined by diffraction using a 30/μm field limiting aperture and a camera length of 1 meter.

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A new lithium diffusion model in layered oxides based on asymmetric but reversible transition metal migration

Energy & Environmental Science ◽

10.1039/c9ee04123k ◽

2020 ◽

Vol 13 (4) ◽

pp. 1269-1278 ◽

Cited By ~ 5

Author(s):

Kyojin Ku ◽

Byunghoon Kim ◽

Sung-Kyun Jung ◽

Yue Gong ◽

Donggun Eum ◽

...

Keyword(s):

Transition Metal ◽

Diffusion Model ◽

Layered Oxides ◽

Layered Oxide ◽

Reversible Transition ◽

Lithium Diffusion ◽

Metal Migration

We propose a new lithium diffusion model involving coupled lithium and transition metal migration, peculiarly occurring in a lithium-rich layered oxide.

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Mechanochemical changes on cyclometalated Ir(iii) acyclic carbene complexes – design and tuning of luminescent mechanochromic transition metal complexes

Inorganic Chemistry Frontiers ◽

10.1039/c9qi01278h ◽

2020 ◽

Vol 7 (3) ◽

pp. 786-794 ◽

Cited By ~ 3

Author(s):

Jingqi Han ◽

Kin-Man Tang ◽

Shun-Cheung Cheng ◽

Chi-On Ng ◽

Yuen-Kiu Chun ◽

...

Keyword(s):

Transition Metal ◽

Metal Complexes ◽

Transition Metal Complexes ◽

Carbene Complexes ◽

New Class

A new class of luminescent cyclometalated Ir(iii) complexes with readily tunable mechanochromic properties derived from the mechanically induced trans-to-cis isomerization have been developed.

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