摘要:

A setup for micro‐Raman investigation at low temperature in a membrane diamond anvil cell is described. This setup allows investigations at variable temperature from room temperature down to 10 K. For a given temperature the system permits a continuous variation in pressure. Performance of the system is illustrated with investigations on benzene and deuterated ice which required pressure cycling (at low temperature) or temperature cycling (at high pressure).  

ISSN:0034-6748    

DOI:10.1063/1.1144435

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A static high‐pressure apparatus based on an internal force produced by constraining thermal expansion is devised. This apparatus does not require a large hydraulic press and is not accompanied by frictional force because it does not have a sliding part. As an example, in case of using lithium fluoride as a pressure source, the high pressures created in the apparatus are measured using pressure dependences of melting points of lead and aluminum. By the measurements, it is demonstrated that the apparatus creates pressures of 1.65 and 2.85 GPa at 440 and 842 °C, respectively. These measured values are in good agreement with the values calculated by using the finite‐element method.

ISSN:0034-6748    

DOI:10.1063/1.1144436

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A uniaxial dead weight creep apparatus has been designed to investigate the low stress, low strain‐rate rheologic behavior of refractory minerals. Displacement and displacement rate resolutions of 0.5 &mgr;m and 0.1 nm/s, respectively, on samples of 1.5‐mm cross section and 3.0‐mm length at temperatures up to 1900 K have been achieved. Oxygen fugacity is controlled to 0.1 log unit, load to 0.1 N, and temperature to 5 K. Maximum stresses applied were between 25 and 30 MPa. Use of this apparatus has allowed the investigation of the transient creep regime in olivine, an important mineral in the Earth’s mantle.

ISSN:0034-6748    

DOI:10.1063/1.1144437

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Imbedded thin‐film thermocouples can be used for the measurement of transient surface temperatures with high spatial resolution and sensitivity. To minimize environmental effects it is desirable to have close proximity between the reference junction and the sensor junction. In this article, we present and compare two calibration techniques for such thermocouples. The first technique is a steady‐state technique and uses a focused laser beam with a diameter of 3 &mgr;m as a point heat source. This technique consists of two steps. The first step is an absolute, but spatially averaged temperature measurement with a resistive temperature sensor. In the second step, the uncalibrated thermocouple junction is translated to resolve the spatial temperature profile generated by the laser spot. Both measurements are then combined to provide an absolute calibration which is independent of the thermal properties of the imbedding material and of the absorbed laser power. We used a simple sensor design which consists of a Ni resistive stripe, and the thermocouple junctions it forms with Ta/Au/Ta electrical leads. The second calibration technique is based on a dynamic measurement. To implement this technique we fabricated a small electrical heating element close to one of the junctions. With the dynamic calibration, the time‐resolved response of the thermocouple to a short heat pulse is recorded. A least‐squares fit of a simple model of heat diffusion to the measured response yields both the temperature calibration of the thermocouple and the heat diffusivity of the imbedding medium. The temperature calibration of the thermocouple obtained with the dynamic technique is in good agreement with the steady‐state calibration.

ISSN:0034-6748    

DOI:10.1063/1.1144438

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A mechanical apparatus designed for use in deep level transient spectroscopy (DLTS) experiments and capable of applying more than 5 GPa pressure to a semiconductor crystal sample at temperatures from 300–450 K is described. This compound lever system applies a temperature‐independent stress to the sample throughout the temperature range of interest. As an illustration of this device’s application, the initial result of a uniaxial stress DLTS experiment on EL2 inn‐GaAs is given. EL2 is found to split under the [100] uniaxial stress, denying the AsGaand AsGa–Asimodels.

ISSN:0034-6748    

DOI:10.1063/1.1144439

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A quartz resonator with a built‐in microheater used as a piezoelectric sorption sensor for mercury vapors in the air is presented. With the construction presented here a maximum sensitivity of 3×10−6g/m3can be reached. The built‐in microheater heats the crystal up to 150 °C and regenerates the sensor without dismounting it from the equipment. The sensor can be used in devices for environmental pollution control and in cases in which precise determination of low mercury vapor concentrations in air is necessary.

ISSN:0034-6748    

DOI:10.1063/1.1144440

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

This article presents a simple, lab scale, vacuum furnace design that features good temperature stability, rapid temperature response, and high‐vacuum and high‐temperature capabilities. The furnace was developed for applications such asinsituelectrical resistivity measurements, precise heat treatment of small samples, and complex heat treatments.

ISSN:0034-6748    

DOI:10.1063/1.1144441

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A new technique, based on the cavity resonance, of measuring the complex dielectric permittivity of liquid samples is described in detail. The errors in the measurement of the real and imaginary parts of the complex dielectric permittivity are ∼±1% and ±3%, respectively. The complex dielectric permittivity values measured using this method for some standard liquids are also presented. A comparison is made between the present values and the values obtained using standard techniques.

ISSN:0034-6748    

DOI:10.1063/1.1144442

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A machine is described which allows bicrystals of metals and ceramics to be made by pressure bonding at temperatures up to 1500 °C in ultrahigh vacuum (UHV). The mutual orientation of the two component crystals can be adjusted to within 0.1°. The surfaces to be bonded can be sputter cleaned with Ar ions while monitoring by Auger electron spectroscopy, and dopants can be applied by evaporation in a separate chamber. The machine allows the production of bicrystals with interfaces of precisely defined crystallography and chemistry. The specimen size is sufficient for fracture mechanical characterization of interface strength. The performance of the machine is illustrated with data for niobium‐sapphire bicrystals. The machine has been shown to produce bicrystal interfaces whose purity is not measurably impaired by atmospheric contaminants. Fracture resistant levels of Nb‐Al2O3interfaces bonded at 1700 °C in ordinary high vacuum are reached in the UHV machine already at 1000 °C. Going to temperatures around 1450 °C raises the fracture resistance to more than twice the level obtained in ordinary high vacuum at 1700 °C.

ISSN:0034-6748    

DOI:10.1063/1.1144443

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A new measuring system using an optical fiber and a position sensing photodetector was developed to measure a three‐dimensional distribution of a magnetic force. A steel ball attached to a cantilever made of an optical fiber generated force in a magnetic field. The displacement of the ball due to the force was detected by a position‐sensing photodetector with the capability of detecting two‐directional coordinates of the position. By scanning the sensing system in a magnetic field, we obtained distributions of two‐directional component of the magnetic force vector. The component represents the gradient of a squared magnetic field. The usefulness of the system for measuring the magnetic field distribution in a narrow clearance and for evaluating superconducting machine components such as magnetic bearings was verified experimentally.  

ISSN:0034-6748    

DOI:10.1063/1.1144444

出版商:AIP    

年代:1993

数据来源: AIP