Dissolution and solubility of calcite-rhodochrosite solid solutions [(Ca1-xMnx)CO3] at 25 °C

AbstractA complete series of calcite-rhodochrosite solid solutions [(Ca1-xMnx)CO3] are prepared, and their dissolution processes in various water samples are experimentally investigated. The crystal morphologies of the solid solutions vary from blocky spherical crystal aggregates to smaller spheres with an increasing incorporation of Mn in the solids. Regarding dissolution in N2-degassed water, air-saturated water and CO2-saturated water at 25 °C, the aqueous Ca and Mn concentrations reach their highest values after 1240–2400 h, 6–12 h and < 1 h, respectively, and then decrease gradually to a steady state; additionally, the ion activity products (log_IAP) at the final steady state (≈ solubility products in log_Ksp) are estimated to be − 8.46 ± 0.06, − 8.44 ± 0.10 and − 8.59 ± 0.10 for calcite [CaCO3], respectively, and − 10.25 ± 0.08, − 10.26 ± 0.10 and − 10.28 ± 0.03, for rhodochrosite [MnCO3], respectively. As XMn increases, the log_IAP values decrease from − 8.44 ~ − 8.59 for calcite to − 10.25 ~ − 10.28 for rhodochrosite. The aqueous Mn concentrations increase with an increasing Mn/(Ca + Mn) molar ratio (XMn) of the (Ca1-xMnx)CO3 solid solutions, while the aqueous Ca concentrations show the highest values at XMn = 0.53–0.63. In the constructed Lippmann diagram of subregular (Ca1-xMnx)CO3 solid solutions, the solids dissolve incongruently, and the data points of the aqueous solutions move progressively up to the Lippmann solutus curve and then along the solutus curve or saturation curve of pure MnCO3 to the Mn-poor side. The microcrystalline cores of the spherical crystal aggregates are preferentially dissolved to form core hollows while simultaneously precipitating Mn-rich hexagonal prisms.

Download Full-text

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2818137 ◽

1998 ◽

Vol 120 (2) ◽

pp. 405-409 ◽

Cited By ~ 12

Author(s):

P. Monmousseau ◽

M. Fillon ◽

J. Freˆne

Keyword(s):

Steady State ◽

Dynamic Loading ◽

Dynamic Load ◽

Journal Bearings ◽

Operating Conditions ◽

Maximum Temperature ◽

Tilting Pad ◽

Transient Period ◽

Final Steady State ◽

Tilting Pad Journal Bearings

Nowadays, tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady state to a final steady state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions, and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD, and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws < 1, Fdyn/Ws = 1 and Fdyn//Ws > 1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature, and the shaft orbit is presented. The final steady state is obtained a long time after the appearance of a dynamic load.

Download Full-text

Synthesis of Calcium Orthophosphates by Chemical Precipitation in Aqueous Solutions: The Effect of the Acidity, Ca/P Molar Ratio, and Temperature on the Phase Composition and Solubility of Precipitates

Processes ◽

10.3390/pr8091009 ◽

2020 ◽

Vol 8 (9) ◽

pp. 1009

Author(s):

Mykola V. Nikolenko ◽

Kateryna V. Vasylenko ◽

Victoria D. Myrhorodska ◽

Andrii Kostyniuk ◽

Blaž Likozar

Keyword(s):

Solid Phase ◽

Chemical Precipitation ◽

Molar Ratio ◽

Key Factors ◽

Correlation Dependence ◽

Molar Ratios ◽

Calcium Orthophosphates ◽

Calcium Cations ◽

Solubility Isotherms ◽

Solubility Products

Studies on chemical precipitation of the calcium orthophosphates have shown that their phase compositions do not vary depending on molar ratio Ca/P but are sensitive to solutions acidity and temperature. These are two key factors that determine the phase transformation progress of metastable phases into less soluble precipitates of the phosphates. It was proposed to compare calcium orthophosphates solubility products with calcium cations quantities in their formulas. It was found that there was a linear correlation between calcium orthophosphates specific solubility products and their molar ratios Ca/P if hydroxyapatite and its Ca-deficient forms were excluded from consideration. It was concluded that the relatively large deviations of their solubility products from the found correlation should be thought of as erroneous data. That is why solubility products were changed in accordance with correlation dependence: pKS for hydroxyapatite was 155, pKS for Ca-deficient hydroxyapatites was 114–155. The solubility isotherms, which were calculated on the basis of the corrected pKS values, coincided with the experimental data on solid-phase titration by Pan and Darvell.

Download Full-text

Experimental Identification of Steady-State Turbomachinery Heat Transfer Using Nondimensional Groups

Journal of Heat Transfer ◽

10.1115/1.4046794 ◽

2020 ◽

Vol 142 (6) ◽

Author(s):

Markus Baumann ◽

Christian Koch ◽

Stephan Staudacher

Keyword(s):

Heat Transfer ◽

Steady State ◽

Gas Turbines ◽

Experimental Identification ◽

Wide Range ◽

Nonsteady State ◽

Data Points ◽

Steady State Heat ◽

Steady State Heat Transfer ◽

Turboshaft Engine

Abstract Diabatic performance modeling is a prerequisite for engine condition monitoring based on nonsteady-state data points (e.g., Putz et al. 2017, “Jet Engine Gas Path Analysis Based on Takeoff Performance Snapshots,” ASME J. Eng. Gas Turbines Power, 139(11), p. 111201.). The importance of diabatic effects increases with decreasing engine size. Steady-state diabatic modeling of turbomachinery components is presented using nondimensional parameters derived from a dimensional analysis. The resulting heat transfer maps are approximated using the analytic solution for a pipe. Experimental identification of the maps requires the measurement of casing and gas path temperatures. This approach is demonstrated successfully using a small turboshaft engine as a test vehicle. A limited amount of measurements was needed to generate a steady-state heat transfer map which is valid for a wide range of operating points.

Download Full-text

Ultrarelativistic Plasma Shell Collisions in γ‐Ray Burst Sources: Dimensional Effects on the Final Steady State Magnetic Field

The Astrophysical Journal ◽

10.1086/426066 ◽

2005 ◽

Vol 618 (2) ◽

pp. 822-831 ◽

Cited By ~ 61

Author(s):

C. H. Jaroschek ◽

H. Lesch ◽

R. A. Treumann

Keyword(s):

Magnetic Field ◽

Steady State ◽

Plasma Shell ◽

Dimensional Effects ◽

Final Steady State ◽

Γ Ray

Download Full-text

Effect of stacking-fault energy on steady-state creep rates in copper-base solid solutions

Scripta Metallurgica ◽

10.1016/0036-9748(71)90068-8 ◽

1971 ◽

Vol 5 (10) ◽

pp. 909-914 ◽

Cited By ~ 11

Author(s):

Hiroshi Oikawa ◽

Seiichi Karashima

Keyword(s):

Steady State ◽

Solid Solutions ◽

Stacking Fault ◽

Steady State Creep ◽

Stacking Fault Energy ◽

Copper Base

Download Full-text

Effect of Humic Substances and Silicon Ions on Stability of Iron Hydroxide (III) Nanoparticles

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.872.237 ◽

2013 ◽

Vol 872 ◽

pp. 237-240 ◽

Cited By ~ 5

Author(s):

Ludmila N. Shiyan ◽

Ksenia I. Machekhina ◽

Elena A. Tropina ◽

Elena N. Gryaznova ◽

Vladimir V. An

Keyword(s):

Steady State ◽

Humic Substances ◽

Organic Substance ◽

Iron Hydroxide ◽

Molar Ratio ◽

Colloidal System ◽

Colloid System ◽

System Composition ◽

Silicon Ions ◽

The Stability

The paper reports on experimental modeling of the colloid system composition in natural groundwater. It is shown that the stability of iron hydroxide nanoparticles relates to the presence of silica and humic substances. It was found out the molar ratio of iron/silicon/organic substance is equal to 1/7/2, where stable iron (III) hydroxide nanoparticles form. The iron hydroxide nanoparticle size ranging from 30 to 600 nm was determined. It characterizes the steady state of the colloidal system.

Download Full-text

On the evolution of thermally driven shallow cavity flows

Journal of Fluid Mechanics ◽

10.1017/s0022112094000054 ◽

1994 ◽

Vol 259 ◽

pp. 107-124 ◽

Cited By ~ 6

Author(s):

P. G. Daniels ◽

P. Wang

Keyword(s):

Steady State ◽

Numerical Solutions ◽

Temporal Evolution ◽

Initial Conditions ◽

Lateral Wall ◽

Cavity Flows ◽

Thermally Driven ◽

Order Of Magnitude ◽

Final Steady State ◽

Shallow Cavity

The temporal evolution of thermally driven flow in a shallow laterally heated cavity is studied for the nonlinear regime where the Rayleigh number R based on cavity height is of the same order of magnitude as the aspect ratio L (length/height). The horizontal surfaces of the cavity are assumed to be thermally insulating. For a certain class of initial conditions the evolution is found to occur over two non-dimensional timescales, of order one and of order L2. Analytical solutions for the motion throughout most of the cavity are found for each of these timescales and numerical solutions are obtained for the nonlinear time-dependent motion in end regions near each lateral wall. This provides a complete picture of the evolution of the steady-state flow in the cavity for cases where instability in the form of multicellular convection does not occur. The final steady state evolves on a dimensional timescale proportional to l2/κ, where l is the length of the cavity, κ is the thermal diffusivity of the fluid and the constant of proportionality depends on the ratio R/L.

Download Full-text