On the stability of alkali metals in the interlayer spacing of graphite

1990 ◽  
Vol 38 (3) ◽  
pp. 403-406
Author(s):  
H Shioyama ◽  
K Tatsumi ◽  
I Souma
Keyword(s):  
Alkali Metals ◽  
Interlayer Spacing ◽  
The Stability

scholarly journals Carbonitration of a Tool for Pressing Stainless Steel Pipes

2020 ◽  
Vol 7 (2) ◽  
pp. C17-C21
Author(s):  
I. V. Ivanov ◽  
M. V. Mohylenets ◽  
K. A. Dumenko ◽  
L. Kryvchyk ◽  
T. S. Khokhlova ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Treatment ◽  
Heat Resistance ◽  
Alkali Metals ◽  
Matrix Ring ◽  
High Hardness ◽  
Operating Conditions ◽  
Matrix Rings ◽  
Conventional Heat Treatment ◽  
The Stability

To upgrade the operational stability of the tool at LLC “Karbaz”, Sumy, Ukraine, carbonation of tools and samples for research in melts of salts of cyanates and carbonates of alkali metals at 570–580 °C was carried out to obtain a layer thickness of 0.15–0.25 mm and a hardness of 1000–1150 НV. Tests of the tool in real operating conditions were carried out at the press station at LLC “VO Oscar”, Dnipro, Ukraine. The purpose of the test is to evaluate the feasibility of carbonitriding of thermo-strengthened matrix rings and needle-mandrels to improve their stability, hardness, heat resistance, and endurance. If the stability of matrix rings after conventional heat setting varies around 4–6 presses, the rings additionally subjected to chemical-thermal treatment (carbonitration) demonstrated the stability of 7–9 presses due to higher hardness, heat resistance, the formation of a special structure on the surface due to carbonitration in salt melts cyanates and carbonates. Nitrogen and carbon present in the carbonitrided layer slowed down the processes of transformation of solid solutions and coagulation of carbonitride phases. The high hardness of the carbonitrified layer is maintained up to temperatures above 650 °C. If the stability of the needle-mandrels after conventional heat treatment varies between 50–80 presses, the needles, additionally subjected to chemical-thermal treatment (carbonitration) showed the stability of 100–130 presses due to higher hardness, wear resistance, heat resistance, the formation of a special surface structure due to carbonitration in melts of salts of cyanates and carbonates. Keywords: needle-mandrel, matrix ring, pressing, heat treatment, carbonitration.

scholarly journals The Stability of Intercalated Sericite by Cetyl Trimethylammonium Ion under Different Conditions and the Preparation of Sericite/Polymer Nanocomposites

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 900 ◽  
Author(s):  
Yu Liang ◽  
Dexin Yang ◽  
Tao Yang ◽  
Ning Liang ◽  
Hao Ding
Keyword(s):  
Aspect Ratio ◽  
Polymer Nanocomposites ◽  
Interlayer Space ◽  
Chemical Resistance ◽  
Interlayer Spacing ◽  
Layered Silicates ◽  
Pure Epoxy ◽  
Different Temperatures ◽  
The Stability ◽  
Ultraviolet Shielding

Layered silicates are suitable for use as fillers in nanocomposites based on their particular features, such as large aspect ratio, easy availability, and chemical resistance. Among them, sericite is distinguished for its higher aspect ratio, higher resilience, and ultraviolet shielding and absorption. Previously, sericite was structure-modified and intercalated by CTAB to expand its interlayer space. The intercalated sericite seems promising for use in the fabrication of polymer/sericite composites or pillared sericite. However, special attention should be paid to the stability of the intercalated sericite because the CTAB inside the layer may be de-intercalated, which would affect the interlayer spacing and its surface properties. In this article, the stability of the sericite intercalated by CTAB was tested by changing different variables, such as different washing solvents, different temperatures, ultrasonic cleaning, and different solution conditions. Finally, sericite/polymer nanocomposites were produced with the stable intercalated sericite, and showed excellent properties compared with pure epoxy resin.

XVI.—The Stability of Suspensions. II. The Rate of Sedimentation of Kaolin Suspensions Containing Colloidal Silicic Acid

1928 ◽  
Vol 47 ◽  
pp. 202-221
Author(s):  
William Ogilvy Kermack ◽  
William Turner Horace Williamson
Keyword(s):  
Silicic Acid ◽  
Alkali Metals ◽  
Hydrogen Ion ◽  
Base Exchange ◽  
Ion Concentrations ◽  
Insoluble Material ◽  
Rate Of Sedimentation ◽  
The Stability ◽  
Clay Suspensions ◽  
Complete Precipitation

Summary1. The experiments previously reported on the effect of salts at various hydrogen ion concentrations on the rate of sedimentation of kaolin suspensions have been extended so as to include the chlorides of the alkali metals, including ammonium but excluding rubidium.In acid suspensions the action in inhibiting sedimentation is least in the case of cæsium and greatest in the case of sodium. The results are discussed in the light of the Gedroiz-Wiegner theory of base exchange in soils and stability of clay suspensions.2. When kaolin suspensions contain a small quantity of colloidal silicic acid the normal effect appears to be one of slight protection.3. Under certain conditions the effect of silicic acid is to produce precipitation of a film of insoluble material over the surface of the particles. In this case an abnormally rapid sedimentation of the particles results, and there ensues an extremely rapid and complete precipitation.4. Under other conditions the presence of the silicic acid prevents the formation of a precipitate, and in this case the abnormal sedimentation occurring in the absence of silicic acid tends to disappear.5. The meaning of the terms “abnormal flocculation” and “anomalous flocculation” is discussed, and it is pointed out that the use of these terms is sometimes attended with ambiguity.

The stability of gaseous lithium hydroxide at high temperatures and its relation with the hydroxyl concentration of flame gases

1953 ◽  
Vol 219 (1137) ◽  
pp. 204-215 ◽  
Keyword(s):  
Hydroxyl Radicals ◽  
Thermal Equilibrium ◽  
Alkali Metals ◽  
Lithium Hydroxide ◽  
The Other ◽  
Theoretical Treatment ◽  
Free Hydroxyl ◽  
The Stability ◽  
Comparison Of The Results ◽  
Fair Degree

The techniques developed by Sugden and collaborators have been applied to the measurement of the ionization resulting from the addition of lithium compounds to hydrogen/air flames. Comparison of the results with those for the other alkali metals shows that lithium gives many too few electrons, and it is suggested, as a result of a comparison of the hydroxides and halides, that this is due to the removal of a large proportion of the lithium as gaseous hydroxide. A quantitative test of this hypothesis shows a very marked agreement with theoretical treatment. The consistency is such that the method appears to be very suitable for the estimation of the concentration of free hydroxyl radicals in flame gases, provided that a fair degree of thermal equilibrium obtains.

Influence of Sub-angstrom Change in Interstitial Ion Size on Clay Swelling

2020 ◽  
Author(s):  
Sai Adapa ◽  
Ateeque Malani
Keyword(s):  
Adsorbed Water ◽  
Interlayer Spacing ◽  
Layered Materials ◽  
Clay Swelling ◽  
Gas Recovery ◽  
The Stability ◽  
Ion Size ◽  
Stability Of Water ◽  
Hydration Characteristics ◽  
Cation Size

<div>Clay minerals in contact with aqueous bulk reservoir undergo a geological transformation of swelling or shrinking by exchanging interstitial cations. For geological applications, it is crucial to understand the stability of these layered materials. Here, we demonstrate that a sub-angstrom change in the interstitial cation size with similar hydration characteristics is enough to destabilize the optimum spacing of layered materials. We used molecular simulations to investigate the stability of water layers in the K-, Rb-, and Cs-mica pores. We find that ±0.1 Å, change in the size of interstitial cation - from Rb<sup>+</sup> to K<sup>+</sup> or Cs<sup>+</sup> ion - leads to -15 to 5 % change in equilibrium loading of adsorbed water and 2 to 35 % change in interlayer spacing. Our thermodynamic analysis reveals an intricate interplay between enthalpic and entropic contributions caused by the structural change of water in the pores due to the hydration of interstitial cations. The understanding from this work has direct implications in designing clay swelling inhibitors in the oil/gas recovery using fracking and sealing materials for radioactive waste. </div>

The change in the standard Gibbs energy during the formation of the acid selenites of the alkali metals

1986 ◽  
Vol 51 (9) ◽  
pp. 1933-1941 ◽  
Author(s):  
Zdeněk Mička ◽  
Miroslav Ebert
Keyword(s):  
Gibbs Energy ◽  
Alkali Metals ◽  
Standard Gibbs Energy ◽  
Cesium Salts ◽  
The Stability

The heterogeneous M2SeO3-H2SeO3-H2O systems (M = Li, Na, K, Rb, Cs) were studied at 298 K using the Filippov eutonic method, yielding the values of the change in the standard Gibbs energy of reactions leading to the formation of the acid selenites of these metals. It follows from the ΔG0 values that the stability of hydrogenselenites and trihydrogenbis(selenites) increases from lithium to cesium and also, except for cesium salts, on transition from MHSeO3 to MH3(SeO3)2.

scholarly journals Influence of Amino Acids on the Mobility of Iodide in Hydrocalumite

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 836
Author(s):  
Mengmeng Wang ◽  
Hirofumi Akamatsu ◽  
Keiko Sasaki
Keyword(s):  
Amino Acids ◽  
Ion Exchange ◽  
Interlayer Spacing ◽  
Organic Substances ◽  
Cement System ◽  
Anionic Species ◽  
Alkaline Conditions ◽  
Living Organisms ◽  
The Stability ◽  
Formation Energies

In the cement system, hydrocalumite is a candidate adsorbent for low-level 129I anionic species. However, the stability of hydrocalumite after immobilizing I− is unclear when they are exposed to pedosphere characterized by organic substances derived from living organisms. In the present work, five amino acids were selected as simplified models of natural organic substances under alkaline conditions. L-cysteine (H2Cys) and L-aspartic acid (H2Asp) accelerated the release of I− from I-hydrocalumite through ion-exchange. Ion-exchange of Cys2− with I− in I-hydrocalumite was faster than Asp2−, and the interlayer spacing (d003) of Cys-hydrocalumite was smaller than that of Asp-hydrocalumite. DFT simulations not only supported the above results but also predicted that there was a positive correlation between the formation energies and interlayer spacings of amino acids intercalated hydrocalumite, depending on the configurations. Moreover, in the DFT predictions, the interaction between amino acids and metallic hydroxide layers was responsible for the formation of hydrogen bonds and Ca-O chemical bonds between the -COO− groups and [Ca2Al(OH)6]+. The other three amino acids did not show intercalation through ion-exchange. The stability of I-hydrocalumite is influenced differently by coexisting amino acids, depending on the ionic sizes, charge numbers, and hydrophilicity, which cause the second contamination.

scholarly journals Thermal Stability of Potassium-Promoted Cobalt Molybdenum Nitride Catalysts for Ammonia Synthesis

Catalysts ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 100
Author(s):  
Paweł Adamski ◽  
Wojciech Czerwonko ◽  
Dariusz Moszyński
Keyword(s):  
Thermal Stability ◽  
Alkali Metals ◽  
Ammonia Synthesis ◽  
Stability Test ◽  
Molybdenum Nitride ◽  
Molybdenum Nitrides ◽  
Cobalt Molybdenum Nitride ◽  
Synthesis Catalysts ◽  
Two Phases ◽  
The Stability

The application of cobalt molybdenum nitrides as ammonia synthesis catalysts requires further development of the optimal promoter system, which enhances not only the activity but also the stability of the catalysts. To do so, elucidating the influence of the addition of alkali metals on the structural properties of the catalysts is essential. In this study, potassium-promoted cobalt molybdenum nitrides were synthesized by impregnation of the precursor CoMoO4·3/4H2O with aqueous KNO3 solution followed by ammonolysis. The catalysts were characterized with the use of XRD and BET methods, under two conditions: as obtained and after the thermal stability test. The catalytic activity in the synthesis of ammonia was examined at 450 °C, under 10 MPa. The thermal stability test was carried out by heating at 650 °C in the same apparatus. As a result of ammonolysis, mixtures of two phases: Co3Mo3N and Co2Mo3N were obtained. The phase concentrations were affected by potassium admixture. The catalytical activity increased for the most active catalyst by approximately 50% compared to non-promoted cobalt molybdenum nitrides. The thermal stability test resulted in a loss of activity, on average, of 30%. Deactivation was caused by the collapse of the porous structure, which is attributed to the conversion of the Co2Mo3N phase to the Co3Mo3N phase.

Improved stability of alkali metals on catalysts during analytical electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 1016-1017
Author(s):  
Kathleen B. Reuter ◽  
Charles E. Lyman
Keyword(s):  
Alkali Metals ◽  
Ion Beam ◽  
Analytical Electron Microscopy ◽  
Cold Trap ◽  
Alcohol Synthesis ◽  
Glass Slides ◽  
Analytical Electron ◽  
Carbon Coated ◽  
Improved Stability ◽  
The Stability

Determination of the location and quantity of poison or promoter elements on catalyst surfaces is an ideal application for the high spatial resolution available on the analytical electron microscope (AEM). However, these elements are often unstable under an electron beam making them difficult to detect consistently. This paper describes a method to enhance the stability of cesium, a mobile alkali metal, on the surface of a catalyst using a thin coating of chromium.The catalyst in this study was MoS2 doped with 5.3 wt% CsOOCH (4.8 mol% Cs) which is used for alcohol synthesis. After grinding with a mortar and pestle and spreading between glass slides, the Cs/MoS2 was supported on a carbon coated Cu grid. The Cs/MoS2 particles were coated with 10nm of Cr using a VCR Group, Inc. ion beam sputterer model IBS/TM200. During sputtering, the vacuum produced by a turbo pump and LN2 cold trap was better than 10-5 torr and the sample was continuously rotated and tilted.

ON THE PHASE STABILITY OF ALKALI METALS UNDER EXTERNAL PRESSURE

1993 ◽  
Vol 07 (01n03) ◽  
pp. 305-308
Author(s):  
BEKIR KARAOGLU ◽  
S. M. MUJIBUR RAHMAN
Keyword(s):  
Phase Stability ◽  
Alkali Metals ◽  
Structural Phase ◽  
Pair Potential ◽  
External Pressure ◽  
Simultaneous Application ◽  
Pseudopotential Theory ◽  
Spherical Waves ◽  
Total Energies ◽  
The Stability

Structural phase stability of certain alkali metals under external pressure is investigated in terms of the pseudopotential and augmented-spherical-waves (ASW) methods. The pair potential trend and the free energy differences between structures — both treated in a second-order pseudopotential theory — are invoked to explain qualitatively some aspects of the stability of the underlying phases at various pressures. Simultaneously, the ASW method is employed to compute the total energies and density-of-states (DOS) at the Fermi level for the phases concerned. The calculated differences in total energies between structures and the DOS curves shade some light in understanding the phase stability of the alkali metals under pressure. The simultaneous application of a perturbative and a nonperturbative treatment on the same footing has brought along some unified concluding remarks in dealing with this particular problem of phase stability.

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