摘要:

Measurements made at the National Standards Laboratory and at Iowa State University of the linear expansion coefficient a for Si, Cu, Ag, Al and Ge below 35 K agree within limits of experimental uncertainty and should constitute reliable reference data. At temperatures from 35 K toca100 K, there are data for Cu measured at NBS and by Rubinet al.which disagree by ∼10 7times; 10−8K−1. From 130 to 230 K these and Russian data agree well but above 230 K they differ, the difference reaching 10 × 10−8K−1 near room temperature. Comparison of &agr;‐values for Si is a useful guide when considering the reliability of these reference data.

ISSN:0094-243X    

DOI:10.1063/1.2945923

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The anisotropic thermal expansion and compressibility coefficients of black phosphorus have been determined by high temperature single‐crystal x‐ray diffraction, by high pressure x‐ray diffraction and by neutron (time‐of‐flight) diffraction and areKa = 1.5(2),Kb = 15.1(4),Kc = 12.1(4),Kv = 30.2(1.0) × 10−4 kbar−1. The volume changes agree well with that reported by Bridgman. The Burch‐Murnaghan coefficient BTis 325 kbar and B′Tis 6.114. The a‐axis parameter undergoes irreversible and inconsistent changes not yet understood so that the data on the thermal expansion coefficients is unreliable. Single crystals have been grown from a bismuth‐red phosphorus solution at 400°C and have been examined by x‐ray diffractometer techniques in a miniature high temperature single crystal furnace to 200°C. The zig‐zag phosphorus bond lengths and angles along the a‐axis increase from 2.209A.U. and 96.2° at room temperature to 2.224A.U. and 96.5° at 200°C whilst the other bond lengths show little change. These anisotropic properties of black phosphorus appear to be determined to a large extent by the structural feature of the zig‐zag chain of atoms along the a‐axis.

ISSN:0094-243X    

DOI:10.1063/1.2945940

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The elastic constants of non‐metamict and partly metamict (density 4.531 g.cm−3) zircon have been determined at room temperature and pressure by means of ultrasonic phase comparison method demonstrating the large effect of radiation damage on the elastic constants of zircon. Using the elastic constants data of nonmetamict and metamict zircons various isotropic, anisotropic and polycrystalIine properties have been derived, including thermal and axial Gru¨neisen parameters, Young's and the shear moduli, average longitudinal and shear sound velocities and the Debye temperature. These values are compared with the available data in the literature.

ISSN:0094-243X    

DOI:10.1063/1.2945926

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The anisotropic thermal expansion of manganese diboride has been determined with neutron diffraction over the temperature range 5–298 K. The variation of lattice parameter with temperature is defined by the equationsa = 3.0044 + 4.9 × 10−6 Tc = 3.0358 − 2 × 10−6 T + 7 × 10−8 T2. The c parameter is found to contract initially, passing through a minimum at 14 K.

ISSN:0094-243X    

DOI:10.1063/1.2945933

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper presents the values of thermal expansion anisotropy for various types of beryllium, including hot pressed, hot isopressed, cold isopressed, and extruded beryllium. The results were obtained by means of foil resistance strain gages. The data was collected in the temperature range of 75F to 200F. Included in the paper is a method devised to characterize the thermal expansion of a piece of single crystal silicon. This piece of silicon has been used to verify the manufacturer's values of thermal expansion compensation for the strain gages.

ISSN:0094-243X    

DOI:10.1063/1.2945934

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Invar and Elinvar alloys are widely applied for precision measurement instruments. These practical alloys are all ferromagnetic, and the ferromagnetism of these alloys often limits the scope of their application. In recent years, therefore, a considerable amount of efforts are devoted to the research and development for nonferromagnetic Invar or Elinvar alloys.Cr is an antiferromagnetic metal and its magnetic properties can be explained by the SDW theory. The physical properties such as thermal expansivity and electrical resistivity change anomalously near the Ne´el temperature, and these properties are sensibly modified by the addition of other elements.Taking the above‐mentioned results into consideration, present authors investigated the temperature dependences of the physical properties for some Cr‐base primary solid solution alloys, and found these alloys have a certain temperature region in which both Invar and Elinvar characteristics coexist.It is the first time that these both characteristics have been found in the same alloys. And these alloys are practically free from the effect of any magnetic field.

ISSN:0094-243X    

DOI:10.1063/1.2945935

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The thermal expansion of europium fluoride(EuF2)has been measured with a push‐rod dilatometer. Over the range 25°C–200°C the expansion coefficient is given by&agr; = 14.23 × 10−6 −0.007 × 10−8 t + 2.88 × 10−10 t2where t is the temperature in °C. The thermal Gruneisen constant has a value 1.17 while a calculation based on an ionic model gives a value of 1.64 for the Gruneisen constant.

ISSN:0094-243X    

DOI:10.1063/1.2945936

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Rock is a complex brittle solid consisting of heterogeneous aggregates of polycrystalline minerals which are characteristically anisotropic. An estimation of rock damage induced by cyclic temperature changes is important for planning utilization of underground space for storing energy. A method of predicting the damage induced by temperature variations from the thermal dilation characteristics of intact and fractured mine rocks was formulated and tested in this study. A dilatometer system capable of controlled heating and cooling rates was designed and used for the measurements. Test results of the thermal dilation characteristics of granitic rock types for heating up to and cooling from 400° C at different rates up to 50° C/min indicate that predominant damage takes place during initial exposure of intact rock to temperature cycling. The damage induced in granitic rocks reaches a steady state after three successive thermal cycles.

ISSN:0094-243X    

DOI:10.1063/1.2945937

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A method is described for the measurement of linear thermal expansion in the plane of thin materials. The measurements are performed by a thermomechanical analysis (TMA) technique developed for polymer films, in which samples are held in a specially designed set of Invar chucks. A critical aspect of this technique is the mode in which the chucks grip the composites, as compared to the thinner, more pliable polymer films. Thermal expansions of composite materials with&agr;≥ 5 ppm/°Cwere found to be precise to within ±3% and accurate to within ±6% when dry specimens were measured at 0% relative humidity.

ISSN:0094-243X    

DOI:10.1063/1.2945938

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A volume dependent lattice dynamical model is presented for the inert gas solids. The model, which incorporates first and second neighbor interactions, utilizes the three elastic constants to predict the phonon dispersion. The volume dependences of the individual phonon frequencies are deduced with the use of a Lennard‐Jones potential. The coefficient of thermal expansion is then calculated from the associated mode‐Gru¨neisen parameters. Finally, the melting curves for solid argon, neon and xenon are calculated with the aid of Lindemann's criterion and the Gr¨neisen equation of state. The calculated results indicate fair agreement with available experimental data.

ISSN:0094-243X    

DOI:10.1063/1.2945939

出版商:AIP    

年代:1974

数据来源: AIP