Vertically Oriented Films of Layered Rare Earth Hydroxides Grown Directly on Flat and Tubular Substrates

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.

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Structure-property relationships of PE/PP sandwiched films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126998 ◽

1987 ◽

Vol 45 ◽

pp. 454-455

Author(s):

J. Petermann ◽

G. Broza ◽

U. Rieck ◽

A. Jaballah ◽

A. Kawaguchi

Keyword(s):

Mechanical Tests ◽

Polymer Materials ◽

Ionic Crystals ◽

Structure Property ◽

Polymer Systems ◽

Structure Property Relationships ◽

Oriented Films ◽

Materials Used ◽

Polymer Laminates ◽

Heated Glass

Oriented overgrowth of polymer materials onto ionic crystals is well known and recently it was demonstrated that this epitaxial crystallisation can also occur in polymer/polymer systems, under certain conditions. The morphologies and the resulting physical properties of such systems will be presented, especially the influence of epitaxial interfaces on the adhesion of polymer laminates and the mechanical properties of epitaxially crystallized sandwiched layers.Materials used were polyethylene, PE, Lupolen 6021 DX (HDPE) and 1810 D (LDPE) from BASF AG; polypropylene, PP, (PPN) provided by Höchst AG and polybutene-1, PB-1, Vestolen BT from Chemische Werke Hüls. Thin oriented films were prepared according to the method of Petermann and Gohil, by winding up two different polymer films from two separately heated glass-plates simultaneously with the help of a motor driven cylinder. One double layer was used for TEM investigations, while about 1000 sandwiched layers were taken for mechanical tests.

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Study of segregation in La1.8Sr0.2CuO4 superconductor by STEM-EDS microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125294 ◽

1987 ◽

Vol 45 ◽

pp. 54-55

Author(s):

T. F. Kelly ◽

P. J. Lee ◽

E. E. Hellstrom ◽

D. C. Larbalestier

Keyword(s):

Rare Earth ◽

High Field ◽

Transport Current ◽

Total Thickness ◽

New Class ◽

Ceramic Superconductors ◽

Current Densities ◽

Group Ii ◽

Eds Microanalysis

Recently there has been much excitement over a new class of high Tc (>30 K) ceramic superconductors of the form A1-xBxCuO4-x, where A is a rare earth and B is from Group II. Unfortunately these materials have only been able to support small transport current densities 1-10 A/cm2. It is very desirable to increase these values by 2 to 3 orders of magnitude for useful high field applications. The reason for these small transport currents is as yet unknown. Evidence has, however, been presented for superconducting clusters on a 50-100 nm scale and on a 1-3 μm scale. We therefore planned a detailed TEM and STEM microanalysis study in order to see whether any evidence for the clusters could be seen.A La1.8Sr0.2Cu04 pellet was cut into 1 mm thick slices from which 3 mm discs were cut. The discs were subsequently mechanically ground to 100 μm total thickness and dimpled to 20 μm thickness at the center.

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Microstructural characterization of a cast RENi5-based alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151714 ◽

1993 ◽

Vol 51 ◽

pp. 1176-1177

Author(s):

G. M. Micha ◽

L. Zhang

Keyword(s):

Electron Microscopy ◽

Rare Earth ◽

Microstructural Characterization ◽

Binary Compound ◽

Nickel Metal ◽

Cast Material ◽

Nickel Metal Hydride ◽

Transmission Electron ◽

Cast Condition

RENi5 (RE: rare earth) based alloys have been extensively evaluated for use as an electrode material for nickel-metal hydride batteries. A variety of alloys have been developed from the prototype intermetallic compound LaNi5. The use of mischmetal as a source of rare earth combined with transition metal and Al substitutions for Ni has caused the evolution of the alloy from a binary compound to one containing eight or more elements. This study evaluated the microstructural features of a complex commercial RENi5 based alloy using scanning and transmission electron microscopy.The alloy was evaluated in the as-cast condition. Its chemistry in at. pct. determined by bulk techniques was 12.1 La, 3.2 Ce, 1.5 Pr, 4.9 Nd, 50.2 Ni, 10.4 Co, 5.3 Mn and 2.0 Al. The as-cast material was of low strength, very brittle and contained a multitude of internal cracks. TEM foils could only be prepared by first embedding pieces of the alloy in epoxy.

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