Strength of Neoprene Compounds and the Effect of Salt Solutions

1983 ◽  
Vol 56 (4) ◽  
pp. 845-852 ◽  
Author(s):  
A. K. Bhowmick ◽  
A. N. Gent
Keyword(s):  
Tensile Strength ◽  
Lower Limit ◽  
Low Temperatures ◽  
Environmental Effect ◽  
Room Temperature ◽  
Characteristic Temperature ◽  
Salt Solutions ◽  
A Value ◽  
Fecl3 Solution ◽  
Tear Propagation

Abstract Soft CR vulcanizates resemble NR vulcanizates in many ways. Their tensile strength is high at low temperatures and drops sharply at a characteristic temperature to a value of about 1–1.5 MPa. Their tear resistance decreases smoothly as the temperature is raised and does not reach a lower limit, even at temperatures as high as 150°C. However, they show continuous tear propagation at room temperature under relatively large tear forces, whereas NR materials do not. This difference must reflect different strengths of the crystallites formed at the tear tip, those in CR being significantly weaker. Also, a specific environmental effect is noted: When immersed in solutions of FeCl3, the CR materials show more rapid tearing, and they tear at significantly lower forces than in water or in NaCl solutions (or in air). Although they swell continuously in water and in salt solutions, the rate of swelling seems far too low to account for the weakening observed. Moreover, the swelling is greater in water, whereas the weakening is specific to FeCl3 solution. It is attributed to a chemical reaction between FeCl3 and the CR molecule.

Considerations in Low-Temperature Mechanical Behavior of Polymer Composite Materials

2015 ◽  
Vol 760 ◽  
pp. 323-328
Author(s):  
Stefan Cotae ◽  
Constantin Popescu ◽  
Horatiu Iancau
Keyword(s):  
Tensile Strength ◽  
Mechanical Behavior ◽  
Fiber Orientation ◽  
Low Temperatures ◽  
Composite Structures ◽  
Room Temperature ◽  
Experimental Program ◽  
Independent Variables ◽  
Factorial Method ◽  
Degree Of Reinforcement

In this paper it has been sought to highlight the mechanical behavior of composite structures at low temperatures compared to mechanical behavior at room temperature. For researches an experimental program has been conceived and built using factorial method. In this method, as dependent variable was taken the tensile strength (σr), while as independent variables were taken: the fiber orientation angles (θ), the degree of reinforcement (Mf) of the composite structure and the temperature (t) at which the tests were carried out (+25°C,-25°C and-50°C respectively). It has been used a complex experimental installation, specific to tests at low temperatures.

The thermal expansion of alkali halides at low temperatures

1965 ◽  
Vol 286 (1405) ◽  
pp. 204-217 ◽  
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Alkali Halides ◽  
Theoretical Models ◽  
Liquid Oxygen ◽  
Rock Salt Structure ◽  
General Behaviour ◽  
A Value ◽  
Salt Structure ◽  
Expansion Coefficients

Linear thermal expansions of eight alkali halides have been determined at liquid oxygen temperatures and at temperatures from 30 °K down to 2 °K. For temperatures T ≤ θ/20, where θ is the Debye temperature, the expansion coefficients are well represented by α = AT 3 + BT 5 . Values are reported for the Grüneisen parameter γ = 3α V/Cx , where C/V is the heat capacity per unit volume and x is the compressibility. For CsBr (b.c.c. structure) γ appears to be nearly independent of temperature, with a value of 2·0 but for the other crystals, which have the rock-salt structure, the parameter γ varies with temperature, chiefly betw een θ/10 and θ/5. At room temperature, γ lies between 1·45 and 1·7 but at low temperature this generally decreases to a value γ 0 which is ca. —0·1 for RbI, +0·3 for KCl, KBr and KI and 1·0 for NaCl and Nal; LiF does not show this decrease, γ 0 being 1·7. The values observed for γ 0 are compared with those calculated from elastic constants and their pressure derivatives and the general behaviour of γ( T ) is observed to conform qualitatively to the predictions of simple theoretical models of Born, Blackman and Barron.

Dielectric Properties of Pd/Y8Z Composites

1999 ◽  
Vol 575 ◽  
Author(s):  
Mark G.H.M. Hendriks ◽  
Henk Verwei ◽  
Manon P. Timmerman
Keyword(s):  
Dielectric Properties ◽  
Percolation Threshold ◽  
Double Layer ◽  
Low Temperatures ◽  
Room Temperature ◽  
Electronic Conductivity ◽  
Impedance Measurements ◽  
High Frequencies ◽  
A Value ◽  
Double Layer Capacity

ABSTRACTImpedance measurements are performed on Pd/Y8Z composites. At 500 'C a 2- 108 times enhancement of the permittivity of the composite at a Pd composition near the percolation threshold for electronic conductivity relative to Y8Z at room temperature is obtained. At high frequencies, the enhancement decreases to a value comparable to geometric capacity of the composite as the double-layer capacity diminishes. At relatively low temperatures the capacity of Y8Z, due to ionic polarisability, increases with temperature.

Darstellung und thermische Zersetzung von Erdalkalimetall-Carbamoylphospliaten / Preparation and Thermal Decomposition of Carbamoylphosphates of Alkaline-earth Metals

1978 ◽  
Vol 33 (4) ◽  
pp. 374-381 ◽  
Author(s):  
Fritz Seel ◽  
Fritz Schinnerling
Keyword(s):  
Low Temperatures ◽  
Alkaline Earth ◽  
Room Temperature ◽  
Chemical Shifts ◽  
Alkaline Earth Metals ◽  
Second Step ◽  
Barium Salt ◽  
Salt Solutions ◽  
Fractional Precipitation ◽  
Preparation And Thermal Decomposition

Abstract After the formation of carbamoylphosphate through the reaction of KH2PO4 with KNCO in aqueous solution, unreacted phosphate and carbamoylphosphate can be separated by fractional precipitation with barium (first step) and calcium or strontium or barium salt solutions (second step) at low temperatures. The carbamoylphosphates of the alkaline earth metals are decomposed above 100 °C to yield predominantly diphosphates and urea. In aqueous suspensions the decomposition proceeds even at room temperature. - The chemical shifts of the phosphorus atom of the carbamoylphosphate ion between pH 6.5 and 8.2 are given.

scholarly journals Review of Multi-Physics Modeling on the Active Magnetic Regenerative Refrigeration

2021 ◽  
Vol 26 (2) ◽  
pp. 47
Author(s):  
Julien Eustache ◽  
Antony Plait ◽  
Frédéric Dubas ◽  
Raynal Glises
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
Room Temperature ◽  
State Of The Art ◽  
Vapor Compression ◽  
Crucial Step ◽  
Potential Alternative ◽  
Vapor Compression Refrigeration ◽  
Preliminary Study ◽  
Physics Modeling

Compared to conventional vapor-compression refrigeration systems, magnetic refrigeration is a promising and potential alternative technology. The magnetocaloric effect (MCE) is used to produce heat and cold sources through a magnetocaloric material (MCM). The material is submitted to a magnetic field with active magnetic regenerative refrigeration (AMRR) cycles. Initially, this effect was widely used for cryogenic applications to achieve very low temperatures. However, this technology must be improved to replace vapor-compression devices operating around room temperature. Therefore, over the last 30 years, a lot of studies have been done to obtain more efficient devices. Thus, the modeling is a crucial step to perform a preliminary study and optimization. In this paper, after a large introduction on MCE research, a state-of-the-art of multi-physics modeling on the AMRR cycle modeling is made. To end this paper, a suggestion of innovative and advanced modeling solutions to study magnetocaloric regenerator is described.

scholarly journals On the measurement of the ratio of the specific heats using small volumes of gas.—The ratios of the specific heat of air and of hydrogen at atmospheric pressure and a temperatures between 20°C. and —183°C

1925 ◽  
Vol 107 (743) ◽  
pp. 510-543 ◽  
Keyword(s):  
Systematic Error ◽  
Low Temperatures ◽  
Room Temperature ◽  
Expansion Chamber ◽  
Small Vessels ◽  
Specific Heats ◽  
Large Expansion ◽  
Before And After ◽  
The One ◽  
Chamber Capacity

Introduction .—In nearly all the previous determinations of the ratio of the specific heats of gases, from measurements of the pressures and temperature before and after an adiabatic expansion, large expansion chambers of fror 50 to 130 litres capacity have been used. Professor Callendar first suggests the use of smaller vessels, and in 1914, Mercer (‘Proc. Phys. Soc.,’ vol. 26 p. 155) made some measurements with several gases, but at room temperature only, using volumes of about 300 and 2000 c. c. respectively. He obtained values which indicated that small vessels could be used, and that, with proper corrections, a considerable degree of accuracy might be obtained. The one other experimenter who has used a small expansion chamber, capacity about 1 litre, is M. C. Shields (‘Phys. Rev.,’ 1917), who measured this ratio for air and for hydrogen at room temperature, about 18° C., and its value for hydroger at — 190° C. The chief advantage gained by the use of large expansion chambers is that no correction, or at the most, a very small one, has to be made for any systematic error due to the size of the containing vessels, but it is clear that, in the determinations of the ratio of the specific heats of gases at low temperatures, the use of small vessels becomes a practical necessity in order that uniform and steady temperature conditions may be obtained. Owing, however, to the presence of a systematic error depending upon the dimensions of the expansion chamber, the magnitude of which had not been definitely settled by experiment, the following work was undertaken with the object of investigating the method more fully, especially with regard to it? applicability to the determination of this ratio at low temperatures.

scholarly journals Effects of Substitution of Y with Yb and Ce on the Microstructures and Mechanical Properties of Mg88.5Zn5Y6.5

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 31
Author(s):  
Hongxin Liao ◽  
Taekyung Lee ◽  
Jiangfeng Song ◽  
Jonghyun Kim ◽  
Fusheng Pan
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Creep Resistance ◽  
Room Temperature ◽  
High Thermal Stability ◽  
Long Period ◽  
Microstructures And Mechanical Properties

The microstructures and mechanical properties of the Mg88.5Zn5Y6.5-XREX (RE = Yb and Ce, X = 0, 1.5, 3.0, and 4.5) (wt.%) alloys were investigated in the present study. Mg88.5Zn5Y6.5 is composed of three phases, namely, α-Mg, long-period stacking ordered (LPSO) phases, and intermetallic compounds. The content of the LPSO phases decreased with the addition of Ce and Yb, and no LPSO phases were detected in Mg88.5Zn5Y2.0Yb4.5. The alloys containing the LPSO phases possessed a stratified microstructure and exhibited excellent mechanical properties. Mg88.5Zn5Y5.0Ce1.5 exhibited the highest creep resistance and mechanical strength at both room temperature and 200 °C, owing to its suitable microstructure and high thermal stability. The yield strength of Mg88.5Zn5Y5.0Ce1.5 at room temperature was 358 MPa. The ultimate tensile strength of Mg88.5Zn5Y5.0Ce1.5 at room temperature and 200 °C was 453 MPa and 360 MPa, respectively.

The Influence of Silicon Dopant and Processing on Thermoelectric Properties of B4C Ceramics

1998 ◽  
Vol 545 ◽  
Author(s):  
Ke-Feng Cai ◽  
Ce-Wen Nan ◽  
Xin-Min Min
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Hot Pressing ◽  
Figure Of Merit ◽  
Room Temperature ◽  
A Value ◽  
Si Doped

AbstractB4C ceramics doped with various content of Si (0 to 2.03 at%) are prepared via hot pressing. The composition and microstructure of the ceramics are characterized by means of XRD and EPMA. Their electrical conductivity and Seebeck coefficient of the samples are measured from room temperature up to 1500K. The electrical conductivity increases with temperature, and more rapidly after 1300K; the Seebeck coefficient of the ceramics also increases with temperature and rises to a value of about 320μVK−1. The value of the figure of merit of Si-doped B4C rises to about 4 × 10−4K−1 at 1500K.

Effect of Small Iron, Chromium and Boron Additions as Alloying Elements on Microstructure and Mechanical Properties of Ni3Al

2007 ◽  
Vol 23 ◽  
pp. 123-126
Author(s):  
Radu L. Orban ◽  
Mariana Lucaci
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Room Temperature ◽  
Alloying Elements ◽  
Alloyed Powder ◽  
Mechanically Alloyed ◽  
Powder Mixtures ◽  
B Additions ◽  
Strength And Ductility ◽  
Iron Chromium

This paper investigates the effect of Fe, Cr and B additions, in small proportions, as alloying elements in Ni3Al with the purpose to reduce its intrinsic fragility and extrinsic embrittlement and to enhance, in the same time, its mechanical properties. It represents a development of some previous research works of the authors, proving that Ni3Al-Fe-Cr-B alloys obtained by reactive synthesis (SHS) starting from Mechanically Alloyed powder mixtures have superior both room temperature tensile strength and ductility, and compression ones at temperatures up to 800 °C, than pure Ni3Al. These create premises for their using as superalloys substitutes.

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