摘要:

An ion thinning apparatus for the preparation of transmission electron microscopy (TEM) specimens was constructed using new‐type cold cathode ion guns. The gun was specially designed for this purpose and has a movable central cathode rod. The rod is used to stabilize the discharge inside the gun when the pressure is high and to stimulate it when the pressure is low. The gun has no consumable parts within it and operates stably for more than 300 h. The thinning apparatus operates well at a vacuum of 3×10−5to 1×10−4Torr and gives argon‐ion beams of 5 kV, 0.8 mA, with a maximum density of 0.25 mA/cm2. A few examples of the preparations and the observations are also described for the specimens of some rock‐forming minerals and human teeth.

ISSN:0034-6748    

DOI:10.1063/1.1137790

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Sample dimensions can be measured optically at high pressures to a precision of about 65 nm. Using an image‐shearing device and a gasketed diamond‐anvil cell, linear strains can be determined to about one part in 103for typical sample dimensions (∼100 &mgr;m). This technique complements x‐ray diffraction measurements in that optical length determinations are rapid, and can be applied to samples that are amorphous or of low atomic number. Compressibility at high temperatures and creep deformation under nonhydrostatic stresses can also be measured optically. We illustrate this method by successfully measuring the hydrostatic compression of gold to 7 GPa, using some of the smallest samples for which length changes have been determined at high pressures (∼40 &mgr;m).

ISSN:0034-6748    

DOI:10.1063/1.1137791

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The calculation of the pressure generated by a controlled‐clearance piston gauge depends upon the jacket pressure corresponding to zero clearance between the piston and cylinderPz. The dependence ofPzon the viscosity of the pressure transmitting fluid, the temperature, and the rate of piston rotation have been measured. The four fluids used in this study have viscosities ranging from 0.7 to more than 10 000 cP. The value ofPzis nearly independent of viscosity below 60 cP. Above 60 cP,Pzdepends strongly upon viscosity. Variations ofPzwith temperature and rate of rotation are more severe at higher viscosities. The results suggest that the best choice of fluid is the one having the lowest viscosity at the operating pressure. Such a fluid can be selected on the basis of having the most nearly linear plot ofPzas a function of pressure of the candidate fluids. These results are also a clear indication that, for the most accurate pressure measurements, a controlled‐clearance piston gauge must be characterized using the same operational and environmental conditions with the same fluid as are used in normal operation.

ISSN:0034-6748    

DOI:10.1063/1.1137792

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A vertically oscillating spherical buoy, magnetically suspended, is used in a new measurement of viscosity. Thus far it has been applied only to transparent, dilute aqueous biomolecular solutions of 0.5‐ml volume. With a different position transducer and sufficient attention to the hydrodynamics, it is possible that these limitations could be transcended. In the method, the phase lag of the motion relative to a sinusoidal magnetic driving force is measured with a phase‐lock amplifier. This has been effective with amplitudes of motion from 100 A˚ to 1.8×10−3cm. At the lowest amplitude noise reduces the precision, but different position sensors could improve that. Motion with larger amplitude risks invoking more complicated boundary layer effects, but has not been necessary thus far for precision at the level of two or three parts in 103relative viscosity. This level of precision has been confirmed with aqueous sucrose and propanol solutions, and the output versus viscosity is linear at least to this level. Practical difficulties in the design of an instrument with such small volume has been our present limitation, both in precision and in the lack of ease of data taking. In this paper we present a simplified theory of operation, the design of the instrument, results of calibration runs, noise behavior and estimated limitations, and a discussion of improvements which might increase the precision about a factor of 10.

ISSN:0034-6748    

DOI:10.1063/1.1137793

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A fast method of calibrating a three‐component hot‐wire probe in a computer‐controlled digital anemometer system is presented.

ISSN:0034-6748    

DOI:10.1063/1.1137794

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In many complex flow fields, such as those encountered in combustion chambers, swirl atomizers, gas separators, and turbomachines, the mean‐flow direction is not well known. However, quite often the experimental determination of the three‐dimensional, steady‐state characteristics of these flows is required. One of the most suitable instruments for measuring mean‐flow values in such situations is the directional pressure probe. Presented in this paper are the results of a program to construct, calibrate, and employ a special type of directional pressure probe which is called: five‐tube pressure probe or 5TPP. Topics such as calibration techniques, various sources of errors, and correction procedures are discussed in detail. Preliminary tests, which included measurements in the initial region of a turbulent jet in a coflowing stream, have shown fair agreement between the measurements of velocity with a 5TPP and with a standard hot‐wire probe.

ISSN:0034-6748    

DOI:10.1063/1.1137801

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A vibrating tube flow densimeter for measuring the density of fluids as functions of temperature and pressure is described. The apparatus allows relative density measurements to be carried out on 6 cm3of solution in about 20 min with a precision of 30 ppm at temperatures to 700 K and pressures to 40 MPa. The accuracy of the densimeter has been verified by measurements on NaCl solutions. Good agreement with literature values was obtained.

ISSN:0034-6748    

DOI:10.1063/1.1137775

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A method using two delay line oscillators is described for measuring the flow velocity of a liquid. Each of the delay line oscillators is composed of two interdigital transducers on one surface of a piezoelectric plate, and an amplifier. The transducer operates as a sound beam radiator or a detector at a liquid–solid interface. The liquid velocity is estimated from the oscillation frequencies of two delay line oscillators. Experimental results confirming the operation principle of the method are satisfactory for water velocity measurement.

ISSN:0034-6748    

DOI:10.1063/1.1137802

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

One approach to chemical measurement in aqueous solution involves the use of two thermistors, with a catalyst such as an enzyme attached to one while the other serves as a reference. Fundamental to this approach is measurement of a small temperature difference &Dgr;Tbetween the two thermistors. The present study uses a flow‐through cell for investigation of &Dgr;Tmeasurement problems. There are important &Dgr;Teffects associated with thermistor separation, flow‐rate variability, absolute flow rate, dissolved gas content, and thermistor excitation power. By using steady flow and passive but continuous partial degassing, a rms &Dgr;Tresolution of 2–3 &mgr;°C can be achieved.

ISSN:0034-6748    

DOI:10.1063/1.1137803

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A fused‐quartz cell with graphite electrodes, suitable for measurement of corrosive liquids at high temperatures is described. Experimental procedures that reduce errors and facilitate the measurement, which are made possible by computer‐controlled automation of the measurement, are also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1137764

出版商:AIP    

年代:1984

数据来源: AIP