摘要:

To overcome the shortcomings of the conventional falling needle viscometer, many improvements have been made, e.g., adopting new design of needle structure, collector, and launcher. Furthermore, Hall magnetic sensors and single-board computer are used in the system, which makes the measurement automatic and intelligent. It is proved in the experiment that the instrument is accurate enough and has excellent performance. The technique can also be applied in falling ball viscometers. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147997

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple design for a four-point probe suitable for precision surface conductivity measurements is described. Our design makes use of small, commercially available spring contact probes which are mounted in a custom built MACOR ceramic probe head. The design is suitable for use in ultrahigh vacuum applications, and the custom-built parts can be fabricated in any machine shop. Very reproducible values were obtained using this probe for surface conductivity measurements on aMoS2(0001)model catalyst, a sputter deposited indium-tin oxide thin film and a doped silicon wafer. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147968

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The finite element method was employed to calculate the correction factors for the measurement of sheet resistivity of a square sample with a square four-point probe. This method is simpler than methods of image and conformal transformation, and can be used for calculating the correction factors for four-point resistivity measurement of an arbitrarily shaped sample with an arbitrary four-probe array. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147998

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This paper describes the development of an automated sample translatory type apparatus capable of measuring the magnetocaloric effect of potential magnetic refrigerants over the temperature range 10 to 325 K in applied fields of up to 9 T. A QuantumDesign®Physical Property Measurement System has been used as the host platform. The emphasis of the design is on rapid and accurate automated measurements with field slew rates of 9 T per second. Measurement repeatabilities of±30 mKhave been achieved. Results are presented for the rare earth metals gadolinium, dysprosium and holmium, and a gadolinium-yttrium alloy. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147999

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electron spin resonance (ESR) of phosphorus-doped silicon was detected using a low temperature magnetic resonance force microscope (MRFM). Force-detected ESR spectra were obtained using an amplitude or frequency modulated microwave field to cyclically saturate the spin magnetization. For a sample containing4×1018phosphorus atoms/cm3, a single strong ESR line was observed. For a sample containing8×1016phosphorus atoms/cm3, a pair of lines split by the 42 G31Phyperfine interaction was observed. This result demonstrates the possibility of using MRFM techniques for spectroscopic purposes. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147967

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A deuterium nuclear magnetic resonance probe in which samples can be studied at pressures up to 3 kbar is described. Characteristics of this device include simple design involving a beryllium copper pressure vessel, a modular coil assembly, and containment of the sample in a sealed polyethylene tube. The probe has been designed for operation at a deuterium frequency of 23 MHz in a 100 mm bore superconducting magnet at temperatures ranging from −20 to 100 °C. The probe has been used in isobaric and isothermal studies of phospholipid bilayer headgroup orientation, phase behavior, and molecular dynamics. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148000

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have constructed a3Heimmersion cell for dielectric measurements of insulating amorphous solids in a nuclear demagnetization cryostat at temperatures between 500 &mgr;K and 150 mK. The samples are directly immersed in3Hewith two heat exchangers per electrode which are thermally isolated from each other and have a very low capacitance to ground. The cell incorporates a195Ptpulsed NMR thermometer with a novel superconducting magnet and a3Heviscometer for calibration. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148055

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A high pressure optical cell capable of producing pressures up to 13.2 GPa using gem-cut single crystal cubic zirconia (CZ) anvils was developed. Maximum pressures obtainable were found to depend upon the particular pressure transmitting medium and gasket material employed. The cubic zirconia anvil high pressure cell (CZAC) provides advantages over the diamond anvil cell in optical and infrared spectroscopy while still maintaining a substantial pressure capability. To demonstrate these advantages, microRaman, optical fluorescence, and infrared absorption measurements were made on diamond, ruby, and 1,3,5-trinitrohexahydro-1,3,5-triazine samples, respectively, using the CZAC cell under high pressure conditions.

ISSN:0034-6748    

DOI:10.1063/1.1147955

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the use of recently developed spin-polarized electron sources with very high polarization for electron spectroscopy. In particular we present data of spin-resolved inverse photoemission from Fe(100) films excited by polarized electrons produced by a strained GaAsP negative electron affinity photocathode. This highly polarized source (beam polarizationP=65&percent;) allows a direct and almost complete decoupling of the majority and minority empty states in Fe(100), much better than the standard GaAs sources (P=20&percent;–30&percent;). The preparation and characterization of the strained photocathode is also discussed. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147954

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An ultrahigh speed imaging system has been developed and built to image rapid solidification of materials. The system collects data from a 10 by 10 array of parallel tapped photodiodes. Up to 8192, frames of data are digitized with 8-bit flash converters at frame rates ranging from 500 to 1 000 000 frames per second. The system has been used to image solidification of a gamma titanium aluminum (&ggr;-TiAl) alloy, with compositionTi-60a/oAl, over a range of undercoolings. The data collected includes the first images of solidification from multiple solidification fronts, images of solidification of a disordered phase followed by the alloy ordering, and quantitative measurement of solidification velocity as a function of undercooling in a &ggr;-TiAl alloy. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147956

出版商:AIP    

年代:1997

数据来源: AIP