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Dec 2004

Volume 75, Issue 12, pp. 5079-5369

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back to top CONDENSED MATTER; MATERIALS

Highly efficient gaseous sample loading technique for diamond anvil cells

Jiyong Zhao, Guoyin Shen, Wolfgang Sturhahn, and E. Ercan Alp

Rev. Sci. Instrum. 75, 5149 (2004); http://dx.doi.org/10.1063/1.1813111 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2004

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A clean and highly efficient technique has been developed to load diamond anvil cells (DACs) using a small amount of gaseous samples. The loading process consists of two steps. First, gas is condensed on a designated cold surface in a pre-evacuated system; second, the solidified sample is loaded into a DAC at liquid-nitrogen temperature. A hundred milliliters of gas at ambient condition is typically required to produce a solidified sample. The use of solid sample material for DAC loading is beneficial to a clean loading process. We demonstrated this technique by loading isotopically enriched (99.925%‐83Kr) krypton into a DAC. 200 ml of this rare and expensive gas were solidified with 99.6% efficiency and almost completely recovered.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
06.60.Ei Sample preparation (including design of sample holders)
81.30.Fb Solidification
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
64.70.D- Solid-liquid transitions
64.70.F- Liquid-vapor transitions

Experimental technique for studying high-temperature phases in reactive molten metal based systems

A. Ermoline, M. Schoenitz, V. K. Hoffmann, and E. L. Dreizin

Rev. Sci. Instrum. 75, 5177 (2004); http://dx.doi.org/10.1063/1.1819011 (9 pages) | Cited 5 times

Online Publication Date: 10 November 2004

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Containerless, microgravity experiments for studying equilibria in molten metal–gas systems have been designed and conducted onboard of a NASA KC-135 aircraft flying parabolic trajectories. An experimental apparatus enabling one to acoustically levitate, laser heat, and splat quench 1–3 mm metal and ceramic samples has been developed and equipped with computer-based controller and optical diagnostics. Normal-gravity testing determined the levitator operation parameters providing stable and adjustable sample positioning. A methodology for optimizing the levitator performance using direct observation of levitated samples was developed and found to be more useful than traditional pressure mapping of the acoustic field. In microgravity experiments, spherical specimens prepared of pressed, premixed powders of ZrO2, ZrN, and Zr, were acoustically levitated inside an argon-filled chamber at one atmosphere and heated by a CO2 laser up to 2800 K. Using a uniaxial acoustic levitator in microgravity, the location of the laser-heated samples could be maintained for about 1 s, so that local sample melting was achieved. Oscillations of the levitating samples in horizontal direction became pronounced in microgravity. These oscillations increased during the sample heating and eventually resulted in moving the sample out of the stable position and away from the laser beam.
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07.20.Ka High-temperature instrumentation; pyrometers
64.70.D- Solid-liquid transitions
07.20.Hy Furnaces; heaters
43.25.Uv Acoustic levitation
81.70.Ha Testing in microgravity environments
06.60.Ei Sample preparation (including design of sample holders)
64.60.F- Equilibrium properties near critical points, critical exponents

A magnetoelasticity instrument for testing the mechanical properties of ferromagnetic materials

Qi Xin, Hou Zhi Ling, and Tian Jian Long

Rev. Sci. Instrum. 75, 5216 (2004); http://dx.doi.org/10.1063/1.1821646 (5 pages)

Online Publication Date: 11 November 2004

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Magnetoelasticity noise is the electromagnetic energy and sound energy released at the surface of ferromagnetic materials due to the movement of the magnetic domain walls inside the material when the material is magnetized by an alternating magnetic field. The electromagnetic energy and sound energy are released simultaneously and interact with each other. These energies carry many characteristics of the material, such as the electromagnetic character, the mechanical character, the material character, etc., and thus can be used to test these characteristics of the material. Based on this theory, an instrument for testing the stresses in ferromagnetic materials is developed in this article. The theory and the structure of the instrument are introduced. The experiment for testing the one-dimensional and two-dimensional stresses in ferromagnetic materials and the analysis of the fatigue damages are carried out. It is a portable instrument and can be used on the field. The outcomes of the test fit quite well with those obtained by the x-ray method.
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07.55.-w Magnetic instruments and components
07.10.Lw Balance systems, tensile machines, etc.
75.80.+q Magnetomechanical effects, magnetostriction
81.70.Bt Mechanical testing, impact tests, static and dynamic loads

High-resolution solid-state nuclear magnetic resonance experiments on highly radioactive ceramics

Ian Farnan, Herman Cho, William J. Weber, Randall D. Scheele, Nigel R. Johnson, and Anne E. Kozelisky

Rev. Sci. Instrum. 75, 5232 (2004); http://dx.doi.org/10.1063/1.1818512 (5 pages) | Cited 9 times

Online Publication Date: 11 November 2004

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A triple-containment magic-angle spinning rotor insert system has been developed and a sample handling procedure formulated for safely analyzing highly radioactive solids by high-resolution solid-state NMR. The protocol and containment system have been demonstrated for magic-angle spinning (MAS) experiments on ceramic samples containing 5–10 wt % 239Pu and 238Pu at rotation speeds of 3500 Hz. The technique has been used to demonstrate that MAS NMR experiments can be used to measure amorphous atomic number fractions produced by accelerated internal radiation damage. This will allow incorporated α-emitters with short half-lives to be used to model the long-term radiation tolerance of potential ceramic radioactive waste forms. This is an example of MAS NMR spectroscopy on samples containing fissionable isotopes.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
76.60.Es Relaxation effects

Flexible microprocessor-based evaporation controller

F.-J. Meyer zu Heringdorf and A. C. Belton

Rev. Sci. Instrum. 75, 5288 (2004); http://dx.doi.org/10.1063/1.1818911 (5 pages) | Cited 10 times

Online Publication Date: 17 November 2004

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Electron beam evaporation sources require two power supplies, one each for the filament current and the electron acceleration. To obtain a stable deposition rate, the emission current between filament and target must remain constant. During film deposition, slight geometry changes in the evaporator cause significant rate variations, making constant readjustment of the emission current necessary. While in commercial solutions, analog feedback regulators are often used to perform this task, these controllers cannot easily be adapted to home-built evaporation sources. The microcontrolled feedback controller presented here is more flexible and versatile than the commercial solutions. The controller can be easily modified to work with different external power supplies and allows the easy upgrade of most existing electron beam evaporation setups. A serial-port computer interface completely integrates the controller into the automated laboratory environment.
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07.05.Dz Control systems
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities
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