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Sep 2002

Volume 73, Issue 9, pp. 3149-3394

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back to top CONDENSED MATTER; MATERIALS

Novel approach to produce polymerized hydrocarbon coatings using dielectric barrier controlled atmospheric pressure glow discharge plasma

K. K. Mishra, R. K. Khardekar, Rashmi Singh, and H. C. Pant

Rev. Sci. Instrum. 73, 3251 (2002); http://dx.doi.org/10.1063/1.1499538 (7 pages) | Cited 15 times

Online Publication Date: 22 August 2002

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Conventionally, low-pressure (<1 Torr) electrical discharges are used for material processing and thin-film deposition. These schemes suffer mainly due to the high cost of equipment and the complexity of operations. The atmospheric pressure glow discharge plasma is developed using a threaded styled electrode in different configurations, and these reactors are used to produce plasma polymerized coatings, required on plane substrates as self-supporting films to obtain membranes for blocking holes in cavities, and on microballoon targets, which are used as fuel containers for inertial confinement fusion, to avoid DT gas permeation. Helium gas is used as the supporting gas for formation and stabilization of atmospheric pressure glow discharge plasma reactors. Ethylene and acetylene gases are used as monomers to produce plasma polymerized hydrocarbon films. These films are characterized using scanning electron microscopy. Plasma polymerized coatings of thickness 100 nm–10 μm with a smooth surface finish (rms<100 nm) are deposited successfully. The surface finish is further improved using a postdischarge configuration. Preliminary results are very encouraging but further progress is to be made in this area. We are also planning to extend this technique for C:H coating of microballoons, which are used as fuel containers in inertial confinement fusion. © 2002 American Institute of Physics.
Show PACS
52.77.Dq Plasma-based ion implantation and deposition
52.80.Hc Glow; corona
81.15.Jj Ion and electron beam-assisted deposition; ion plating
82.35.-x Polymers: properties; reactions; polymerization
68.55.-a Thin film structure and morphology
61.41.+e Polymers, elastomers, and plastics

Fiber-coupled antennas for ultrafast coherent terahertz spectroscopy in low temperatures and high magnetic fields

S. A. Crooker

Rev. Sci. Instrum. 73, 3258 (2002); http://dx.doi.org/10.1063/1.1498904 (7 pages) | Cited 20 times

Online Publication Date: 22 August 2002

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For the purposes of measuring the high-frequency complex conductivity of correlated-electron materials at low temperatures and high magnetic fields, a method is introduced for performing coherent time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed magnets. Miniature fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 1.5 K and up to 17 T, for eventual use in higher-field magnets. Maintaining the submicron alignment between fiber and antenna during thermal cycling, obtaining ultrafast (<200 fs) optical gating pulses at the end of long optical fibers, and designing highly efficient devices that work well with low-power optical gating pulses constitute the major technical challenges of this project. Data on a YBCO superconducting thin film and a high mobility two-dimensional electron gas are shown. © 2002 American Institute of Physics.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
42.81.Wg Other fiber-optical devices
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

A simple system to measure magnetostriction in soft magnetic materials

J. H. Claassen, Matthew A. Willard, and Vincent G. Harris

Rev. Sci. Instrum. 73, 3265 (2002); http://dx.doi.org/10.1063/1.1497498 (3 pages) | Cited 3 times

Online Publication Date: 22 August 2002

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A direct measurement of strain in magnetostrictive materials yields a meaningful result only if the sample remains saturated and the magnetization is rotated between directions parallel and perpendicular to the measurement direction. A simple way to accomplish this is to use small permanent magnets mounted on a rotating shaft. Within the constraints of the limited available space for a sample, we found it most convenient to use a strain gage to detect small changes in length. With commonly available laboratory equipment we were able to achieve a sensitivity ∼0.03 ppm. There is a loading effect that reduces the apparent magnetostriction if the sample is of comparable size to the strain gage. We showed that for a typical nanocrystalline ribbon sample this correction could be experimentally estimated and was of order 20%.
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07.55.-w Magnetic instruments and components
75.80.+q Magnetomechanical effects, magnetostriction
07.10.Pz Instruments for strain, force, and torque
75.50.Ww Permanent magnets

Heater cell for materials synthesis and crystal growth in the large volume high pressure apparatus at 10 GPa

Yasushi Kanke, Minoru Akaishi, Shinobu Yamaoka, and Takashi Taniguchi

Rev. Sci. Instrum. 73, 3268 (2002); http://dx.doi.org/10.1063/1.1499760 (3 pages) | Cited 8 times

Online Publication Date: 22 August 2002

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To realize materials synthesis and crystal growth in a large volume of high pressure apparatus in the region of 10 GPa, a heater cell was developed for a belt-type high pressure apparatus with a bore diameter of 32 mm. The cell consists of a cylindrical electrode made of TiC powders located between a pair of graphite heaters with a disk shape. High temperature of 1500 °C at nominal pressure of 9.7 GPa (9.35 GPa corrected) was successfully generated for 1 h using the cell. Synthesis and growth of stishovite was performed at high pressure and high temperature conditions based on their calibrations. Experimental results suggest that the materials synthesis and crystal growth above 10 GPa can be realized in a large volume of belt-type apparatus using the heater cell. © 2002 American Institute of Physics.
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81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Ka High-temperature instrumentation; pyrometers

Development of a dilatometer based on diffractometry

S. Ledesma, S. N. Goyanes, and C. Duplaá

Rev. Sci. Instrum. 73, 3271 (2002); http://dx.doi.org/10.1063/1.1497504 (4 pages) | Cited 3 times

Online Publication Date: 22 August 2002

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In this article we present a new method to determine the thermal expansion coefficient of polymeric materials. The method is based on the measurement of the diffraction patterns produced by a slit. This slit is produced using two edges, one that remains fixed and the other one attached to the sample, so that the slit modifies its width as the sample temperature is changed. For each temperature the sample length expansion is obtained by using the Fraunhofer diffraction theory. Depending on which parameters of the experimental setup are chosen, this technique can be used to measure expansions of tens of microns or hundreds of microns with a resolution of tenths of microns or a few microns, respectively. As an example, we have determined the coefficient of thermal expansion and the glass transition temperature Tg of a commercial sample of polymethylmethacrylate (PMMA). The obtained results were compared with those reported previously in a sample of the same commercial material using a mechanical dilatometer. Moreover, our results agree with those reported in the literature for different samples of PMMA both for the low temperature T<Tg and high temperature T>Tg regions. © 2002 American Institute of Physics.
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07.10.-h Mechanical instruments and equipment
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

High-temperature contactless viscosity measurements by the gas–film levitation technique: Application to oxide and metallic glasses

Paul-Henri Haumesser, Jacky Bancillon, Michel Daniel, Michel Perez, and Jean-Paul Garandet 

Rev. Sci. Instrum. 73, 3275 (2002); http://dx.doi.org/10.1063/1.1499756 (11 pages) | Cited 5 times

Online Publication Date: 22 August 2002

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In the field of thermophysical characterization of materials at high temperature, a crucial issue is to limit the effect of chemical or physical phenomena occurring at the interface between the sample and the container. Therefore, contactless techniques are well adapted to high-temperature measurements. The gas–film levitation method has recently proved to be applicable to viscosity measurements. Our purpose in this article is to derive viscosity values by the observation of the dynamical response of a perturbed levitating drop. We present here recent improvements in this technique, with particular attention paid to measurement accuracy issues and temperature calibration problems. Viscosity measurements performed on oxide and metallic glasses reveal that a gas–film levitation based viscometer is able to provide measurements with good accuracy (±10%) in a wide viscosity range, from very viscous (up to several kPa s, aperiodic relaxation of the drop) to fluid liquids (a few mPa s, damped oscillation of the drop). © 2002 American Institute of Physics.
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83.85.Jn Viscosity measurements
47.80.-v Instrumentation and measurement methods in fluid dynamics
47.55.D- Drops and bubbles

Zero applied stress rheometer

L. Bellon, L. Buisson, S. Ciliberto, and F. Vittoz

Rev. Sci. Instrum. 73, 3286 (2002); http://dx.doi.org/10.1063/1.1499210 (5 pages) | Cited 6 times

Online Publication Date: 22 August 2002

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In order to test the fluctuation-dissipation relation on rheological properties of soft materials, we built an experiment to measure thermally excited strain in a sample and compare it to the classical response to an external stress. The rheometer is based on a cylindrical Couette geometry. We use differential interferometry to achieve better than 10−10 rad/math sensitivity in angular position above 0.5 Hz. The forcing method, based on electrostatic interaction in a capacitor, generates torques comparable to that of thermal noise. Experiments on a calibrated silicon oil show good agreement between response and fluctuation measurements. © 2002 American Institute of Physics.
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46.80.+j Measurement methods and techniques in continuum mechanics of solids
83.85.Cg Rheological measurements—rheometry
07.10.Pz Instruments for strain, force, and torque
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