Manganin Coil Research Articles

Solidification and loss of hydrostaticity in liquid media used for pressure measurements.

We carried out a study of the pressure dependence of the solidification temperature in nine pressure transmitting media that are liquid at ambient temperature, under pressures up to 2.3 GPa. These fluids are 1:1 isopentane/n-pentane, 4:6 light mineral oil/n-pentane, 1:1 isoamyl alcohol/n-pentane, 4:1 methanol/ethanol, 1:1 FC72/FC84 (Fluorinert), Daphne 7373, isopentane, and Dow Corning PMX silicone oils 200 and 60,000 cS. We relied on the high sensitivity of the electrical resistivity of Ba(Fe(1-x)Ru(x))2As2 single crystals to the freezing of the pressure media and cross-checked with corresponding anomalies observed in the resistance of the manganin coil that served as the ambient temperature resistive manometer. In addition to establishing the temperature-pressure line separating the liquid (hydrostatic) and frozen (non-hydrostatic) phases, these data permit rough estimates of the freezing pressure of these media at ambient temperature. This pressure establishes the extreme limit for the medium to be considered hydrostatic. For higher applied pressures, the medium has to be treated as non-hydrostatic.

High-pressure synthesis of polyphenylacetylene

Polyacetylene is an insoluble conjugated polymer that can be obtained by using conventional ZieglerNatta catalysts [1-3]. Substituted acetylenes, having bulky phenyl groups such as phenylacetylene, produce oligomers not exceeding the number-average molecular weight of 7500 and insoluble polymers by the use of the Ziegler-Natta catalyst [4, 5]. Masuda et al. found in 1974 that group 5 and 6 transition metal catalysts (W and Mo based catalysts) are effective for phenylacetylene polymerization [4, 6]. These polyacetylenes with substituents have attracted much attention as electrical and non-linear optical materials [7-9]. The application of pressure is well known to influence the structure, properties and reactions of substances [10-15]. Acetylene was polymerized at room temperature by a reaction-induced high pressure [11]. A previous paper reported the synthesis of a phenylacetylene oligomer under high pressure (0.11-0.92 GPa) and high temperature (100-200 °C) [16]. In the study reported here, the polymerization of phenylacetylene was carried out at room temperature under high pressure (1.5 GPa). Visible absorption spectroscopy and gel permeation chromatography (GPC) were utilized to characterize the structure of the product. Phenylacetylene (molecular weight 102.14, liquid) in the form H--C=--C--CoH 5 (Wako Pure Chemical Industries Ltd, Japan) was used for the reaction without further purification [purity >99% (gas chromatography)]. The reaction of phenylacetylene under high pressure was performed with a specially designed super high hydrostatic pressure reactor (Hikari High Pressure Machinery Co., Japan). The block diagram of the reactor is schematically illustrated in Fig. 1. Paraffin was used as a pressure transmitting medium. The pressure in the super high pressure vessel was increased ten times compared with that in the high pressure vessel through the hydraulic intensifier. Pressure was measured using a Bourdon gauge (Heise gauge) and a manganin coil gauge. The pressure was displayed on a digital manometer and was recorded on a recorder. The specimen (about 2 g) was packed into a polytetrafluoroethylene cell (inside diameter 8 mm, length 40 mm). After closing the cell, it was introduced into the super high pressure vessel. The specimen was compressed at 1.5 GPa by a motor driven oil pump and substantially reacted at room temperature (2225 °C) for constant times of 1-300 h. After reaction under high pressure, the product was decompressed and removed from the cell. Visible absorption spectra of the products in a quartz cell (specimen path length 10mm) were recorded on an Ultraviolet (UV)-visible recording spectrophotometer (Shimadzu UV-2100). The spectrum was measured in the 400-800 nm region. The molecular weight of the product was determined using a liquid chromatograph (Japan Analytical Industry Co., Ltd, LC-08) consisting of a UV absorption detector (wavelength 254nm) and a column. Chloroform was used as a mobile phase at

High Pressure Study of Transition in ZnTe by Manganin Coil Method

ZnTe which exhibits a few characteristic resistance changes under pressure has been studied in regard of volume change by a recently confirmed manganin coil method. Relatively large volume reductions are observed at 90 and 120 kbar correspond ing to the abrupt resistance changes. A small volume reduction found at 70 kbar may suggest an existence of an isostructural transition.

Phase transitions in barium and bismuth under high pressure

The controversial phase transitions in barium and bismuth were studied with a manganin coil sensor. The transition in barium proposed at 80 kbars by Bastide etal. was confirmed at 95 kbars. For bismuth, the transition reported first by Bridgman around 45 kbars was confirmed at 40 kbars, but that around 65 kbars could not be detected. To make up the P-T diagram of barium, the confirmed transition and the so-called high-Ba transition were traced at elevated temperatures by the resistance anomaly of barium, and the melting points above 90 kbars were determined with a manganin ribbon sensor. The mechanism of the manganin sensor is discussed with regard to the volume change associated with a transition.

Behavior of a manganin coil at elevated temperatures and pressures

We have determined the temperature dependence in the first-order pressure coefficient of a manganin coil to be dβ/dT= (4.2±0.8) ×10−7 (kbar °C)−1 in the equation R (T,P) =R (T,0)(1+βP+γP2), where R (T,P) is the coil resistance at temperature T and pressure P. The measurements were performed by simultaneously measuring the coil resistance and temperature at the transitions of mercury and bismuth, which were observed by differential thermal analysis.

New pressure calibration technique of manganin gauge by microthermal analysis of mercury

Methods of microdifferential thermal analysis (DTA), simple thermal analysis using one thermocouple, and the change of electrical resistance of mercury during melting under high pressure are used to calibrate the pressure coefficient of a manganin coil. It is shown that the methods of microthermal analysis under isobaric conditions yield satisfactory results and are easier to operate than the usual isothermal methods.

Method of checking automatic measuring instruments

1. Instruction No. 166-63 and No. 158-62 must be revised. The procedures discussed in the present article should be considered and the faults indicated above should be eliminated. 2. When checking an AMI in accord with the present instructions it is necessary, in our opinion: to be guided by the standards established in GOST 7164-71 and the technical documentation, or only by the technical documentation if the GOST 7164-71 does not apply (but not the standards given in Instruction No. 166-63 and No. 158-62); to take, when checking for the coincidence of the indicator with the mark being checked, its closest positions to the right and left of this mark. The error and variation must be determined according to the values of the input quantity that correspond to the beginning of the indicator motion away from the position of coincidence when the input quantity is increasing — in the direction of the increase, and when decreasing — in the direction of the decrease. In order to improve the checking efficiency, these values of the input quantity should be determined for each mark checked when approaching it first from one side and then immediately from the other; to check all output devices. If the error of these devices is referred to the AMI'S scale, they must then be checked with due regard for the error of the AMI itself (i.e., as measuring channels). In this case the standardized values of the error and the variation must be increased, respectively, by the permissible values of the error and the variation of the indications. 3. The error of a standard instrument [1, 2, 3] includes the error of all the standard facilities in the checking circuit (for example, when checking the error of the output transducer for the bridge voltage the total error comprises the errors of the resistance box, the connecting leads, and the voltmeter that is used to measure the output transducer's voltage). 4. When checking potentiometers without compensating wires the resistance value of the manganin coil should be chosen in accord with Instruction No. 166-63 for the older designs of potentiometers, but for the KS types where the compensating coil is located outside the instruments — in accord with the technical documentation for these instruments.

Pressure Calibration to 60 kbar Based on the Resistance Change of a Manganin Coil under Hydrostatic Pressure

The relative resistance change of a properly seasoned manganin coil was measured at the center of the region of indifference for the bismuth II-III, thallium II-III, and barium I-II phase transformations in a hydrostatic system. The equilibrium pressures for these transformations were obtained from the relative resistance change of manganin which was calibrated with pressure by means of the mercury L-I and bismuth I-II transition pressures. Equilibrium pressures corrected to 25°C of 26.861±0.042, 36.569±0.153, and 56.273±0.521 kbar were determined for the bismuth II-III, thallium II-III, and barium I-II phase transformations, respectively. Only the barium I-II point deviated from the presently accepted high pressure scale. On the basis of the manganin pressure gauge, either the presently accepted value of the barium I-II point is too high by about 2.5 kbar or the pressure coefficient of manganin resistance changes sharply between 37 and 59 kbar. A two-point quadratic calibration curve was satisfactory for pressures to 37 kbar.

Triaxial compression data on nuclear explosion shocked, mechanically shocked, and normal granodiorite from the Nevada Test Site

Compression tests were performed at room temperature on solid circular cylinders of medium-grained granodiorite from the Hardhat Event conducted at the Nevada Test Site. Confining pressures ranged from 1 to 7000 bars. A piston-cylinder apparatus equipped with an internal axial load cell and manganin coil was used. The confining fluid was a low-viscosity oil. Pre-detonation specimens were cut 0°, 45°, and 90° to the drill core axis and were taken from 195-, 225-, and 255-meter depths. Post-detonation rock was sampled at 23 and 27.5 meters from ground zero, which was located at a depth of 290 meters and experienced a calculated peak shock pressure of approximately 20 kb. Specimens mechanically shocked in the laboratory (35 to 40 kb) were from the 195-meter depth pre-detonation sample. No orientational effects were observed. The failure of granodiorite under compressional stresses was found to be adequately described by a modified Coulomb maximum shear stress theory. Under uniaxial compression, the mode of failure was brittle shear. Under triaxial compression, a quiet slip failure was observed at low confining pressures and brittle shear at high confining pressures. A possible explanation for the occurrence of slip failure may be the presence of a fluid pore pressure within the specimen. Strain measurements were made on several specimens. At atmospheric pressure, the stress histories of the rock were clearly apparent. Under confining pressure, shock effects rapidly disappeared, and, at 4.5 kb, the behavior was essentially that of normal granodiorite. Young's modulus at atmospheric confining pressure for unshocked rock was found to be 0.64 ± 0.26 × 106 bars, which in the upper limit agrees with the reported dynamic value. The average value for rock shocked by nuclear blast is 0.18 × 106 bars and that for mechanically shocked rock is of the order 0.01 × 106 bars.

Electrical Resistance of Manganin Coil to 7 kbar and 200°C

The electrical resistance of a manganin coil was measured at various temperatures and pressures in the ranges of 20 to 200°C and 0 to 7 kbar. Three useful results were obtained from this study. (1) At elevated temperatures, the resistance of the manganin coil is reproducible with rising and falling pressures. (2) At elevated temperatures, the resistance-pressure curves remain linear. (3) The pressure coefficient changes only slightly with temperature. The present study indicates that the manganin coil may be used as a pressure indicator at elevated temperatures, provided that a convenient correction due to the shift of the resistance at different temperatures is made.

High Pressure Manganin Gauge with Multiple Integral Calibrants

A high pressure Manganin gauge with multiple integral calibrants has been developed. It allows accurate and continuous pressure measurement in the 100-kbar range at both room and elevated temperatures. The gauge is designed for use in piston-cylinder, multianvil, and other relatively large volume pressure apparatus. One modification of the gauge consists of a Manganin coil wound on a threaded insulating sleeve which encloses a core of primary calibrants. Bismuth, thallium, and barium have been used for calibrants because they provide four widely separated fixed points in the 100-kbar range. The principle of the gauge's operation is based on (a) the nearly linear dependence of the resistance of Manganin on pressure, (b) the volume discontinuities accompanying pressure-induced first-order phase transitions in the calibrants, and (c) the appreciable strength and rigidity at high pressure of commonly used solid pressure-transmitting media. The over-all response of the gauge consists of nearly linear segments of increasing resistance vs pressure between well-established fixed points. The extension of the range of the gauge to higher pressures and its use for semiquantitative estimates of unknown volume changes accompanying polymorphic transitions are described.

Measurement of high pressures by electrolyte conductance

A simple electrolyte conductance cell is described which can be used as a secondary reference pressure gauge. With a dilute acetic acid solution in the cell, and referring to a manganin coil gauge as the pressure standard, in the pressure range 1000-3000 atmospheres the standard deviation in pressure measurements ranged from 0.35% at 1000 atmospheres to 0.25% at 3000 atmospheres. The electrolyte cell is free from hysteresis and strain effects and is a small and easily transportable unit.

The Ice Calorimeter. With Remarks on the Constancy of the Density of Ice

The primary object of the work was the re-determination, by an electrical method, of the constant of Bunsen's ice-calorimeter. The heat was supplied by a manganin coil wound on a mica rack which fitted the interior tube of the calorimeter, and the results are based on determinations of E.M.F. and resistance. The current was adjusted so that the difference of potential at the ends of the heating coil was exactly equal to the E.M.F. of a number of standard cadmium cells n series. The conditions were varied as much as possible. Thus the rate of energy supply in the fastest experiments was more than seven times that in the slowest. Errors due to progressive freezing or thawing of the ice mantle were greatly diminished by suspending the calorimeter within a transparent vacuum vessel of cylindrical form, the stem and capillary of the calorimeter projecting through a rubber stopper, and the vacuum vessel being completely embedded in powdered ice. The mean value of the calorimeter constant was found to be 15.486 milligrammes of mercury per mean calorie. The Constancy of the Density of Ice. - Various observers have advanced evidence tending to show that the density of ice at 0°C. is not a definite constant. A consideration of their work leads to the conclusion that the small variations of density found for different samples might be simply due to the presence of occluded water or an amorphous modification cementing the ice crystals together. The value (80.30) of the latent heat of fusion of ice, calculated from the ice calorimeter, supports this view, as it is higher by about 0.7 per cent. than the value obtained by direct determinations with ice in bulk.