scholarly journals The effect of thermal agitaion on atomic arrangement in alloys—II

1935 ◽  
Vol 151 (874) ◽  
pp. 540-566 ◽  
Keyword(s):  
High Temperatures ◽  
Experimental Work ◽  
Low Temperatures ◽  
Theoretical Treatment ◽  
X Ray ◽  
Atomic Arrangement ◽  
Metal Atoms ◽  
Theoretical Investigations ◽  
The Subject ◽  
Kinetics Of

The transformations between a disordered arrangement of the metal atoms in an alloy at high temperatures and an ordered arrangement of the atoms at low temperatures have formed the subject of many experimental and theoretical investigations. The process of segregation into regular positions was first envisaged by Tammann in 1919. It was proved to take place in the gold-copper and other alloy systems by Johannson and Linde by X-ray investigation. Theoretical treatments of the problem have been given in papers by Borelius, Johannson, and Linde, Gorsky, and Dehlinger and Graf, and the same authors have published a large amount of experimental work on this type of transformation in the Au-Cu system. Some experiments on order-disorder transformations in the Fe-Al system, carried out by Bradley and Jay in this laboratory, led us to examine the kinetics of the change, and we recently published a paper in these Proceedings dealing with various aspects of it. Since publishing this paper, we have become aware that our theoretical treatment has in several respects a closer parallelism to those of Borelius, Gorsky, and Dehlinger than we realized at the time of writing it. We shall try to make a proper acknowledgment in the present paper.

scholarly journals The combustion of aromatic and alicyclic hydrocarbons. II. The ignition of aromatic hydrocarbons at high temperatures

1939 ◽  
Vol 171 (946) ◽  
pp. 421-433 ◽  
Keyword(s):  
High Temperatures ◽  
Aromatic Hydrocarbons ◽  
Isothermal Oxidation ◽  
Present Communication ◽  
Temperature Range ◽  
Benzene Toluene ◽  
The Subject ◽  
Kinetics Of

In the first paper of this series (Burgoyne 1937) the kinetics of the isothermal oxidation above 400° C of several aromatic hydrocarbons was studied. The present communication extends this work to include the phenomena of ignition in the same temperature range, whilst the corresponding reactions below 400° C form the subject of further investigations now in progress. The hydrocarbons at present under consideration are benzene, toluene, ethylbenzene, n -propylbenzene, o-, m - and p -xylenes and mesitylene.

scholarly journals The Stability of Icosahedral Cd-Yb

2003 ◽  
Vol 805 ◽  
Author(s):  
Günter Krauss ◽  
Sofia Deloudi ◽  
Andrea Steiner ◽  
Walter Steurer ◽  
Amy R. Ross ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ambient Temperature ◽  
Mechanical Stress ◽  
Single Crystals ◽  
High Temperatures ◽  
Low Temperatures ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

ABSTRACTThe stability of single-crystalline icosahedral Cd-Yb was investigated using X-ray diffraction methods in the temperature range 20 K ≤ T ≤ 900 K at ambient pressure and from ambient temperature to 873 K at about 9 GPa. Single-crystals remain stable at low temperatures and in the investigated HP-HT-regime. At high temperatures and ambient pressure, the quasicrystal decomposes. The application of mechanical stress at low temperatures yields to the same decomposition, the formation of Cd. A reaction of icosahedral Cd-Yb with traces of oxygen or water causing the decomposition seems reasonable, but a low-temperature instability of this binary quasi-crystal cannot be ruled out totally.

Disorder in decagonal quasicrystals

2003 ◽  
Vol 218 (2) ◽  
Author(s):  
F. Frey ◽  
E. Weidner
Keyword(s):  
High Temperature ◽  
Neutron Diffraction ◽  
High Temperatures ◽  
Experimental Work ◽  
Diffuse Scattering ◽  
Diffuse Intensity ◽  
X Ray ◽  
Decagonal Quasicrystals ◽  
Ordered Alloys ◽  
Insight Into

AbstractComplementary neutron and x-ray diffuse scattering may provide insight into structural super-ordering and disordering of decagonal quasicrystals (d-phases), and, in consequence, into the formation and stability of aperiodically ordered alloys. Neutron diffraction makes a contrasting almost isoelectronic atomic species possible, as well as a separation of elastic and inelastic diffuse intensity contributions. Experimental work at high temperatures is comparatively unproblematic. The method suffers, however, from the difficulty in obtaining sufficiently sized mono-grain samples and a lack of dedicated neutron diffraction instruments. Recent results, with a main focus on high-temperature (<1000°C) investigations of disordered decagonal Al—Ni—Co phases are reported and some tentative models are discussed.

scholarly journals The conductivity of heat insulators

1900 ◽  
Vol 65 (413-422) ◽  
pp. 283-288 ◽  
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
Comparative Efficiency ◽  
The Subject ◽  
Materials Used

The comparative efficiency of materials used as insulators has been the subject of several investigations ; the majority of these have been conducted at fairly high temperatures, and it may be questioned whether the results can be applied to the same materials when used as a lagging to protect bodies at low temperatures. Moreover the methods adopted do not seem susceptible of any considerable accuracy.

Devitrification of an FE43 CR25NI20 B12 Glass

1985 ◽  
Vol 58 ◽  
Author(s):  
Teiichi Ando ◽  
Yutaka Hara ◽  
N.J. Grant
Keyword(s):  
Low Temperatures ◽  
Annealing Temperature ◽  
Isothermal Annealing ◽  
Magnetic Measurements ◽  
X Ray ◽  
Bcc Phase ◽  
Kinetics Of

ABSTRACTThe kinetics of bcc crystallization and subsequent transformations in an Fe43Cr25Ni20B12 glass were monitored by magnetic measurements and X-ray diffrsaction. The metastable bcc phase (ferrite) which forms first transforms to austenite and a boride during isothermal annealing. At low temperatures the ferritegrows without significant partitioning of Fe, Cr and Ni. Increasing the annealing temperature results in alloy partitioning which is directly linked with the ferrite decomposition.

scholarly journals Theoretical Study of C2H5 + NCO Reaction: Mechanism and Kinetics

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Nan-Nan Wu ◽  
Shun-li OuYang ◽  
Liang Li
Keyword(s):  
Low Temperatures ◽  
High Pressures ◽  
Theoretical Study ◽  
Single Point ◽  
Structure Information ◽  
Theoretical Investigations ◽  
Mechanism And Kinetics ◽  
Combustion Processes ◽  
Low Pressures ◽  
Kinetics Of

Theoretical investigations are performed on mechanism and kinetics of the reactions of ethyl radical C2H5 with NCO radical. The electronic structure information of the PES is obtained at the B3LYP/6-311++G(d,p) level of theory, and the single-point energies are refined by the CCSD(T)/6-311+G(3df,2p) level of theory. The rate constants for various product channels of the reaction in the temperature range of 200–2000 K are predicted by performing VTST and RRKM calculations. The calculated results show that both the N and O atoms of the NCO radical can attack the C atom of C2H5 via a barrierless addition mechanism to form two energy-rich intermediates IM1 C2H5NCO (89.1 kcal/mol) and IM2 C2H5OCN (64.7 kcal/mol) on the singlet PES. Then they both dissociate to produce bimolecular products P1 C2H4 + HOCN and P2 C2H4 + HNCO. At high temperatures or low pressures, the reaction channel leading to bimolecular product P2 is dominant and the channel leading to P1 is the secondary, while, at low temperatures and high pressures, the collisional stabilization of the intermediate plays an important role and as a result IM2 becomes the primary product. The present results will enrich our understanding of the chemistry of the NCO radical in combustion processes.

scholarly journals On the reflection and refraction of X-Rays by perfect crystals

1933 ◽  
Vol 140 (841) ◽  
pp. 301-313 ◽  
Keyword(s):  
Point Of View ◽  
Theoretical Treatment ◽  
X Rays ◽  
X Ray ◽  
Reflection And Refraction ◽  
Atomic Scattering Factor ◽  
Mosaic Crystals ◽  
Atomic Scattering ◽  
Scattering Factor ◽  
The Subject

It is now well established that from the point of view of the theory of X-ray reflection, the majority of crystals can be divided into those which are relatively perfect and those which are relatively imperfect or mosaic. The intensity of reflection of X-rays by the former has been much less extensively studied than by the latter and hitherto no really satisfactory agreement appears to have been found between the observed intensities of reflection from highly perfect crystals such as diamond and the results predicted by the theoretical treatment of the subject. It will be shown in what follows that this lack of agreement is very largely removed when the atomic scattering factor, f , which plays such an important part in the theory of reflection by mosaic crystals, is taken into account for perfect crystals.

Flex Life and Crystallization of Synthetic Rubber

1944 ◽  
Vol 17 (2) ◽  
pp. 398-403 ◽  
Author(s):  
J. H. Fielding
Keyword(s):  
Natural Rubber ◽  
Experimental Work ◽  
Thermal Effects ◽  
X Ray ◽  
The Past ◽  
Synthetic Rubber ◽  
New Material ◽  
The Subject ◽  
And Performance ◽  
Ray Patterns

Abstract The crystalline structure of stretched natural rubber has been the subject of much experimental work in the past. A great deal of this has been devoted to the more theoretical aspects, such as x-ray patterns, thermal effects, and volume change. It is now known that neither Buna-N nor GR-S has a fiber diagram when stretched and that Butyl-B and Neoprene do have such patterns. Since the industry is now in the process of changing from natural rubber to GR-S, it is of interest to see just what this lack of crystallinity means from a compounding and performance standpoint. It is possible that many of our ideas based on rubber must change, that GR-S must be considered to be a new material, and that radical changes in formulation and construction must be made.

The impact of variations in temperature on early Plasmodium falciparum development in Anopheles stephensi

Parasitology ◽  
1995 ◽  
Vol 111 (5) ◽  
pp. 539-545 ◽  
Author(s):  
B. H. Noden ◽  
M. D. Kent ◽  
J. C. Beier
Keyword(s):  
Plasmodium Falciparum ◽  
High Temperatures ◽  
Low Temperatures ◽  
Anopheles Stephensi ◽  
Development Stage ◽  
Effect Of Temperature ◽  
Infection Rates ◽  
Developmental Processes ◽  
The Impact ◽  
Kinetics Of

SUMMARYThe effect of temperature on early Plasmodium falciparum development was examined in Anopheles stephensi. The rates of both ookinete development and bloodmeal digestion were lengthened as temperatures decreased from 27 to 21 °. However, low temperatures (21–27 °) did not significantly influence infection rates or densities of either ookinetes or oocysts. In contrast, high temperatures (30 and 32 °) significantly impacted parasite densities and infection rates by interfering with developmental processes occurring between parasite fertilization and ookinete formation, especially during zygote and early ookinete maturation. This study demonstrates clearly that temperature affects the sporogonic development of P. falciparum in anophelines by altering the kinetics of ookinete maturation. These studies not only confirm the ookinete as the key development stage affecting the probability of vector infectivity, they provide new insights into the epidemiology of P. falciparum infections.

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