Dissolution kinetics of synthetic LaPO4-monazite in acidic media

MRS Advances ◽  
2018 ◽  
Vol 3 (21) ◽  
pp. 1133-1137 ◽  
Author(s):  
Yulia Arinicheva ◽  
Stefan Neumeier ◽  
Felix Brandt ◽  
Dirk Bosbach ◽  
Guido Deissmann
Keyword(s):  
Single Phase ◽  
Dissolution Kinetics ◽  
Dissolution Process ◽  
Temperature Range ◽  
Long Term Stability ◽  
Aqueous Environments ◽  
Fundamental Understanding ◽  
Acidic Conditions ◽  
Kinetics Of

Single-phase monazite-type ceramics are discussed as waste forms for the safe disposal of surplus plutonium or separated minor actinides. To derive a fundamental understanding of the long-term stability of these materials under repository relevant conditions, the dissolution kinetics of synthetic lanthanum monazite (LaPO4) were studied in dynamic dissolution experiments in the temperature range from 50 to 90°C under acidic conditions. The surface area normalised dissolution rates increased with temperature from 3.2·10-5 g m-2 d-1 at 50°C to 1.8·10-4 g m-2 d-1 at 90°C. The apparent activation energy Ea of the dissolution process was determined to be about 44 kJ mol-1, indicating a predominantly surface reaction controlled dissolution process in this temperature range. From thermodynamic considerations it can be inferred that the dissolution of the LaPO4 ceramics is governed by the dissolution of a thin layer of La-rhabdophane (LaPO4 · 0.667H2O) forming at the monazite surface in low temperature aqueous environments.

scholarly journals The UV-Vis Study On Anthocyanin Pigments Activities Extracted From Gayo Arabika Coffee Husks

Elkawnie ◽  
2019 ◽  
Vol 5 (2) ◽  
pp. 147
Author(s):  
Hasby Hasby ◽  
Nurhafidhah Nurhafidhah ◽  
Said Ali Akbar
Keyword(s):  
Hydrochloric Acid ◽  
Acid Solution ◽  
Absorption Peak ◽  
Solution Temperature ◽  
Arabica Coffee ◽  
Coffee Husk ◽  
Long Term Stability ◽  
Acidic Conditions ◽  
Anthocyanin Pigments

The anthocyanin activity of Gayo Arabica coffee husk in variations in acid solution, temperature, and pH has been assessed through UV-Vis studies. It is important to optimize these factors to increase the long-term stability of anthocyanins for use in various fields. Gayo Arabica coffee husks was extracted through maceration method with methanol. This process obtained a coffee husks extract of 1.176 mg/μL. The UV-Vis spectrum of the extract displayed the major absorption peak at λmax= 529 nm in hydrochloric acid (HCl), this assigned by the electronic transition from flavylium as the particular characteristic of anthocyanin compounds. The anthocyanin from the extract was stable at temperatures of 35oC and 50oC, to have a major absorption peak at λmax= 529 nm. Therefore, it could probably be said that the lower the temperature, the higher the absorbance value of anthocyanin. Then, husks extract was getting red at pH 1 and 3; almost colorless at pH 5, 8 and 10; and yellow at pH 12. The more acidic conditions causes more anthocyanin pigments to be observed in the form of flavylium or oxonium cations color. Finally, Gayo Arabica coffee husks extract can absorb both ultraviolet (UV) and visible light (visible).

scholarly journals Relationship Among Preparation, Structure and Superconductivity in Ti-Ca-Ba-Cu-O Compounds

1993 ◽  
Vol 15 (3-4) ◽  
pp. 117-138
Author(s):  
I. Kirschner ◽  
S. Leppävuori ◽  
A. Uusimäki
Keyword(s):  
Single Phase ◽  
Substantial Effect ◽  
Experimental Results ◽  
Characteristic Parameters ◽  
Term Stability ◽  
Long Term Stability ◽  
Preparation Conditions ◽  
Superconducting Parameters

Analysis of a comprehensive set of experimental results has proven the substantial effect of the precise preparation conditions upon the structure and superconducting parameters of Ti-Ca-Ba-Cu-O samples. The techniques required for the preparation of specimens of single phase and long-term stability, together with methods for improvement of the characteristic parameters have been determined. Comparing results derived from samples prepared by different methods has allowed the quantitative differences of the characteristic parameters to be evaluated.

Characterization of Type B Carbonate Apatite Sintered Bodies

2011 ◽  
Vol 1301 ◽  
Author(s):  
N. Watanobe ◽  
T. Yoshioka ◽  
T. Ikoma ◽  
T. Kuwayama ◽  
T. Higaki ◽  
...  
Keyword(s):  
Dissolution Kinetics ◽  
Carbonate Apatite ◽  
Artificial Bone ◽  
Type B ◽  
Desorption Process ◽  
Different Temperatures ◽  
Acidic Conditions ◽  
Kinetics Of ◽  
Potential Use

ABSTRACTThe dissolution kinetics of type B carbonate apatite (CAp) disks sintered at different temperatures were investigated under acidic conditions similar to an osteoclastic desorption process in bone remodeling. The type B CAp disks, which were uniaxially pressed at 98MPa and sintered at temperatures of 600 to 700 ºC, showed single crystalline phase and a high relative density of 60-62 % compared to the stoichiometric density of 3.16g/cm3 of hydroxyapatite (HAp). The dissolution rate of type B CAp disks sintered at 650 ºC was 3.5 times faster than that of HAp disks at 650 ºC. These results indicate that the Type B CAp sintered disks show potential use as a biodegradable material for artificial bone.

Dissolution kinetics of meta-torbernite under circum-neutral to alkaline conditions

2009 ◽  
Vol 6 (6) ◽  
pp. 551 ◽  
Author(s):  
Dawn M. Wellman ◽  
Bruce K. McNamara ◽  
Diana H. Bacon ◽  
Elsa A. Cordova ◽  
Ruby M. Ermi ◽  
...  
Keyword(s):  
Dissolution Kinetics ◽  
Coupled Processes ◽  
Effect Of Temperature ◽  
Subsurface Environments ◽  
Alkaline Conditions ◽  
Flow Through ◽  
Uranium Phosphate ◽  
The Stability ◽  
Kinetics Of

Environmental context. Uranium-phosphate minerals have been identified as a long-term controlling phase that limit the mobility of uranium to groundwater in many contaminated subsurface environments. Complex, coupled processes confound the ability to isolate the rates attributed to individual processes. Results of this investigation provide the necessary information to refine current prediction on the release and long-term fate of uranium in subsurface environments. Abstract. The purpose of this investigation was to conduct a series of single-pass flow-through (SPFT) tests to (1) quantify the effect of temperature (23–90°C) and pH (6–10) on meta-torbernite dissolution; (2) compare the dissolution of meta-torbernite to other autunite-group minerals; and (3) evaluate the effect of aqueous phosphate on the dissolution kinetics of meta-torbernite. Results presented here illustrate meta-torbernite dissolution rates increase by ~100× over the pH interval of 6 to 10, irrespective of temperature. The power law coefficient for meta-torbernite, η = 0.59 ± 0.07, is greater than that quantified for Ca-meta-autunite, η = 0.42 ± 0.12. This suggests the stability of meta-torbernite is greater than that of meta-autunite, which is reflected in the predicted stability constants. The rate equation for the dissolution of meta-torbernite as a function of aqueous phosphate concentration is log rdissol (mol m–2 s–1) = –4.7 × 10–13 + 4.1 × 10–10[PO43–].

Evaluation of The Long-Term Stability of Passive Corrosion On The Drip Shield and Waste Package Under Yucca Mountain Conditions

2002 ◽  
Vol 713 ◽  
Author(s):  
D.W. Shoesmith
Keyword(s):  
Environmental Conditions ◽  
Yucca Mountain ◽  
Localized Corrosion ◽  
Waste Package ◽  
Long Term Stability ◽  
Alloy 22 ◽  
Aqueous Environments ◽  
Engineered Barriers ◽  
Titanium Grade

ABSTRACTPossible long term corrosion scenarios for the engineered barriers proposed for the Yucca Mountain (Nevada, USA) repository are reviewed.Introduction:The materials proposed for the engineered barriers in the Yucca Mountain repository (Nevada, USA), Alloy-22 for the waste packages (WP) and titanium Grade-7 (Ti-7) for the drip shield (DS), appear unlikely to suffer localized corrosion (LC) and have very low passive corrosion (PC) rates (1–3). Since environmental conditions will become more benign as temperatures decline and aqueous environments become more dilute (4), this leads to the prediction of exceedingly long waste package lifetimes. In this review, possible corrosion scenarios are discussed in the context of the anticipated evolution in the repository environment.

scholarly journals Optomechanics based soft artificial skin

2021 ◽  
Author(s):  
Abhijit Chandra Roy ◽  
Navin Kumar ◽  
Shreyas B S ◽  
Ananya Gupta ◽  
Aloke Kumar ◽  
...  
Keyword(s):  
Research Effort ◽  
Cost Effective ◽  
Artificial Skin ◽  
Large Area ◽  
Long Term Stability ◽  
Large Numbers ◽  
Fundamental Understanding ◽  
Extreme Sensitivity ◽  
Consistent Performance

Abstract Soft artificial skin capable of sensing touch, pressure and bending similar to soft human skin is important in many modern-day applications including socially interactive robotics, modern healthcare, augmented reality, etc. However, most of the research effort on soft artificial skin are confined to the lab-scale demonstration. We have demonstrated how a fundamental understanding of the contact mechanics of soft material and a specially constructed soft optical waveguide let us develop a highly efficient, resilient, and large-area soft artificial skin for futuristic applications. The soft artificial skin capable of detect touch, load and bending shows extreme sensitivity (up to \({150 \text{k}\text{P}\text{a}}^{-1}\)) to touch, and load, which is 750 times higher than earlier work. The soft-a-skin shows excellent long-term stability i.e. it shows consistent performance up to almost a year. In addition, we describe a 3D printing process capable of producing large areas, large numbers yet cost-effective soft artificial skin. We have shown the functioning of the soft-a-skin in various means.

Effects of film thickness and alkaline concentration on dissolution kinetics of poly(4-hydroxystyrene) in alkaline aqueous solution

2022 ◽  
Author(s):  
Naoki Tanaka ◽  
Kyoko Matsuoka ◽  
Takahiro KOZAWA ◽  
Takuya Ikeda ◽  
Yoshitaka Komuro ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Film Thickness ◽  
Thick Films ◽  
Dissolution Kinetics ◽  
Dissolution Behavior ◽  
Chemically Amplified ◽  
Fundamental Understanding ◽  
Chemically Amplified Resists ◽  
Kinetics Of ◽  
Simple Combination

Abstract The dissolution behavior of a simple combination of poly(4-hydroxystyrene) (PHS) films and tetramethylammonium hydroxide (TMAH) aqueous solution was analyzed to gain a fundamental understanding of the effects of film thickness and alkaline concentration on the dissolution kinetics of chemically amplified resists (CARs). Films of four different thicknesses, from thick (approximately 900 nm) to thin (approximately 50 nm), were developed in 22 different developers of different concentrations. The dissolution behavior of each combination was observed using a quartz crystal microbalance (QCM). Differences in dissolution kinetics due to film thickness were observed even between relatively thick films such as 900- and 500-nm thick films in dilute developers. These differences were considered to be caused by the diffusion of the solution into the films. Thin films also showed characteristic behavior with dilution. This behavior was due to the interaction between the substrate and the films, unlike in the case of thick films.

scholarly journals Tracing the Acetalization of Cyclohexanone in CO2-Expanded Alcohols by Attenuated Total Reflection Infrared Spectroscopy

2009 ◽  
Vol 63 (9) ◽  
pp. 1008-1014 ◽  
Author(s):  
Tsunetake Seki ◽  
Jean-Michel Andanson ◽  
Fabian Jutz ◽  
Alfons Baiker
Keyword(s):  
Ir Spectroscopy ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Znse Crystal ◽  
Promising Alternative ◽  
Practical Tool ◽  
Acidic Conditions ◽  
Kinetics Of

The CO2-catalyzed acetalization is regarded as a promising alternative to the conventional acid-catalyzed method from a viewpoint of green chemistry (C. A. Eckert et al., Ind. Eng. Chem. Res. 43, 2605 (2004)). We have applied in situ attenuated total reflection infrared (ATR-IR) spectroscopy for elucidating and monitoring the acetalization of cyclohexanone in CO2-expanded ethylene glycol and methanol at 50 °C and 3 MPa. The ATR-IR spectra of the reaction mixtures periodically recorded with a ZnSe crystal demonstrate that ATR-IR spectroscopy is a practical tool for tracing the kinetics of acetalizations in situ. In addition, the rate of CO2 dissolution as well as CO2 solubility into the cyclohexanone–alcohol mixtures could be evaluated from the CO2-v3-antisymmetric stretching band. The ZnSe ATR crystal, however, was corroded during longer use under the acidic conditions realized by the dissolution of CO2 in the alcohols. In contrast, the corrosion did not occur when a Ge crystal was used instead of a ZnSe crystal, and therefore the application of a Ge ATR crystal is recommended for continuous long-term experiments with these media.

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