scholarly journals Impact of porosity on calcination and sulfation of calcium sorbents

2018 ◽  
Vol 49 ◽  
pp. 00131
Author(s):  
Renata Włodarczyk ◽  
Michał Wichliński ◽  
Zbigniew Bis
Keyword(s):  
Grain Size ◽  
Flue Gas ◽  
Total Surface Area ◽  
Chemical Processes ◽  
Reactivity Indices ◽  
Mean Diameter ◽  
Mercury Porosimeter ◽  
Capacity Index ◽  
Reaction Furnace ◽  
And Diffusion

The focus of the study was on sorbents with a grain size of 125-250 μm. Examinations of reactivity were conducted in a reaction furnace under conditions required for reactivity testing of calcium sorbents. The tests were performed according to standard calcium sorbent tests (FW). Computation of reactivity indices and capacity index were performed according to formulae contained in previous publications [1]. The process of simultaneous calcination and sulfation of calcium sorbents is controlled by the speed of chemical processes and diffusion. Therefore, surface properties of sorbents, including porosity, play an important role in the flue gas desulphurization process. Examinations of sorbent porosity were performed using a mercury porosimeter. Based on porosimetric analysis, open porosity, the total surface area of sorbents and mean diameter of pores were evaluated for the sorbents studied.

Refinement of Size Distributions for Primary Crystallizations

1997 ◽  
Vol 481 ◽  
Author(s):  
E. Pineda ◽  
T. Pradell ◽  
D. Crespo ◽  
N. Clavaguera ◽  
J. ZHU ◽  
...  
Keyword(s):  
Grain Size ◽  
Metastable Phase ◽  
Primary Crystallization ◽  
Controlled Growth ◽  
Diffusion Controlled ◽  
Average Grain Size ◽  
Soft Impingement ◽  
Single Grain ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTThe microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled.

What is Behind the Inverse Hall-Petch Behavior in Nanocrystalline Materials?

2006 ◽  
Vol 976 ◽  
Author(s):  
Christopher Carlton ◽  
P. J. Ferreira
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Nanocrystalline Materials ◽  
Critical Value ◽  
Petch Relationship ◽  
And Diffusion ◽  
Critical Grain Size

AbstractAn inverse Hall-Petch effect has been observed for nanocrystalline materials by a large number of researchers. This result implies that nanocrystalline materials get softer as grain size is reduced below a critical value. Postulated explanations for this behavior include dislocation based mechanisms and diffusion based mechanisms. In this paper, we report an explanation for the inverse Hall-Petch effect based on the statistical absorption of dislocations by grain boundaries, showing that the yield strength is both dependent on strain rate and temperature, and that it deviates from the Hall-Petch relationship at a critical grain size.

scholarly journals A unifying basis for the interplay of stress and chemical processes in the Earth: support from diverse experiments

2020 ◽  
Vol 175 (12) ◽  
Author(s):  
John Wheeler
Keyword(s):  
Chemical Potential ◽  
Chemical Processes ◽  
Phase Changes ◽  
Solid State Reactions ◽  
Fundamental Aspect ◽  
Diffusion Creep ◽  
Pressure Solution ◽  
Polymorphic Transformations ◽  
The Earth ◽  
And Diffusion

AbstractThe interplay between stress and chemical processes is a fundamental aspect of how rocks evolve, relevant for understanding fracturing due to metamorphic volume change, deformation by pressure solution and diffusion creep, and the effects of stress on mineral reactions in crust and mantle. There is no agreed microscale theory for how stress and chemistry interact, so here I review support from eight different types of the experiment for a relationship between stress and chemistry which is specific to individual interfaces: (chemical potential) = (Helmholtz free energy) + (normal stress at interface) × (molar volume). The experiments encompass temperatures from -100 to 1300 degrees C and pressures from 1 bar to 1.8 GPa. The equation applies to boundaries with fluid and to incoherent solid–solid boundaries. It is broadly in accord with experiments that describe the behaviours of free and stressed crystal faces next to solutions, that document flow laws for pressure solution and diffusion creep, that address polymorphic transformations under stress, and that investigate volume changes in solid-state reactions. The accord is not in all cases quantitative, but the equation is still used to assist the explanation. An implication is that the chemical potential varies depending on the interface, so there is no unique driving force for reaction in stressed systems. Instead, the overall evolution will be determined by combinations of reaction pathways and kinetic factors. The equation described here should be a foundation for grain-scale models, which are a prerequisite for predicting larger scale Earth behaviour when stress and chemical processes interact. It is relevant for all depths in the Earth from the uppermost crust (pressure solution in basin compaction, creep on faults), reactive fluid flow systems (serpentinisation), the deeper crust (orogenic metamorphism), the upper mantle (diffusion creep), the transition zone (phase changes in stressed subducting slabs) to the lower mantle and core mantle boundary (diffusion creep).

Adsorption and diffusion of moisture and wet flue gas on silica gel

2020 ◽  
Vol 227 ◽  
pp. 115890 ◽  
Author(s):  
Prerna Goyal ◽  
Mark J. Purdue ◽  
Shamsuzzaman Farooq
Keyword(s):  
Silica Gel ◽  
Flue Gas ◽  
And Diffusion

Nmos Transistors Fabricated by Simultaneous Laser-Assisted Crystallization and Diffusion on Silicon on Electro-Optic PLZT

1988 ◽  
Vol 100 ◽  
Author(s):  
J. H. Wang ◽  
T. H. Lin ◽  
S. C. Esener ◽  
S. Dasgupta ◽  
S. H. Lee
Keyword(s):  
Grain Size ◽  
Carrier Mobility ◽  
Silicon Crystal ◽  
Hall Effect Measurement ◽  
Cw Laser ◽  
Crystal Film ◽  
Electro Optic ◽  
Doped Silicon ◽  
And Diffusion ◽  
Nmos Transistors

ABSTRACTSimultaneous CW laser assisted crystallization and diffusion for fabricating NMOS transistors on Si/SiO2/PLZT is presented. Hall effect measurement (mobility 74cm2V−1sec×1019cm−3 of phosphorus dopping), crystal delineation (grain size 50×30μm) and Raman spectroscopy (stress 6.0×109dynescm−2) indicated that good quality doped silicon crystal film can be produced with this method. NMOS transistors fabricated by this technology show good performances such as high breakdown voltage (45 V), small leakage current (2 nA/μm), reasonable channel carrier mobility (140cm2V−1−1) and photosensitivity (1.5 A/W).

Magnetite in soils: I. The synthesis of single-domain and superparamagnetic magnetite

Clay Minerals ◽  
1986 ◽  
Vol 22 (4) ◽  
pp. 411-422 ◽  
Author(s):  
R. M. Taylor ◽  
B. A. Maher ◽  
P. G. Self
Keyword(s):  
Grain Size ◽  
Single Domain ◽  
Ph Values ◽  
Neutral Ph ◽  
Mean Diameter ◽  
Series Of Experiments

AbstractA series of experiments has been carried out to investigate the possible formation of magnetite, Fe3O4, under ambient soil-forming conditions. Rapid and easy synthesis of magnetite was achieved through controlled oxidation of Fe2+ solutions at room temperatures and near neutral pH values. The synthetic products were found to range in size between 0·01–0·07 µm (mean diameter) and hence span the theoretical superparamagnetic-single-domain grain-size boundary.

scholarly journals GRAINet: mapping grain size distributions in river beds from UAV images with convolutional neural networks

2021 ◽  
Vol 25 (5) ◽  
pp. 2567-2597
Author(s):  
Nico Lang ◽  
Andrea Irniger ◽  
Agnieszka Rozniak ◽  
Roni Hunziker ◽  
Jan Dirk Wegner ◽  
...  
Keyword(s):  
Grain Size ◽  
Training Data ◽  
Grain Size Analysis ◽  
Training Dataset ◽  
Size Analysis ◽  
Size Distributions ◽  
Mean Diameter ◽  
Grain Size Distributions ◽  
Gravel Bars ◽  
Uav Images

Abstract. Grain size analysis is the key to understand the sediment dynamics of river systems. We propose GRAINet, a data-driven approach to analyze grain size distributions of entire gravel bars based on georeferenced UAV images. A convolutional neural network is trained to regress grain size distributions as well as the characteristic mean diameter from raw images. GRAINet allows for the holistic analysis of entire gravel bars, resulting in (i) high-resolution estimates and maps of the spatial grain size distribution at large scale and (ii) robust grading curves for entire gravel bars. To collect an extensive training dataset of 1491 samples, we introduce digital line sampling as a new annotation strategy. Our evaluation on 25 gravel bars along six different rivers in Switzerland yields high accuracy: the resulting maps of mean diameters have a mean absolute error (MAE) of 1.1 cm, with no bias. Robust grading curves for entire gravel bars can be extracted if representative training data are available. At the gravel bar level the MAE of the predicted mean diameter is even reduced to 0.3 cm, for bars with mean diameters ranging from 1.3 to 29.3 cm. Extensive experiments were carried out to study the quality of the digital line samples, the generalization capability of GRAINet to new locations, the model performance with respect to human labeling noise, the limitations of the current model, and the potential of GRAINet to analyze images with low resolutions.

scholarly journals Spatial variability and the fate of cesium in coastal sediments near Fukushima, Japan

2014 ◽  
Vol 11 (18) ◽  
pp. 5123-5137 ◽  
Author(s):  
E. E. Black ◽  
K. O. Buesseler
Keyword(s):  
Grain Size ◽  
Nuclear Power ◽  
Sediment Cores ◽  
Chemical Processes ◽  
Coastal Sediments ◽  
Full Extent ◽  
Fdnpp Accident ◽  
Sediment Mixing ◽  
Mixing Rates ◽  
Water Depths

Abstract. Quantifying the amount of cesium incorporated into marine sediments as a result of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident has proven challenging due to the limited multi-core sampling from within the 30 km zone around the facility; the inherent spatial heterogeneities in ocean sediments; and the potential for inventory fluctuations due to physical, biological, and chemical processes. Using 210Pb, 234Th, 137Cs, and 134Cs profiles from 20 sediment cores, coastal sediment inventories were reevaluated. A 137Cs sediment inventory of 100 ± 50 TBq was found for an area of 55 000 km2 using cores from this study and a total of 130 ± 60 TBq using an additional 181 samples. These inventories represent less than 1% of the estimated 15–30 PBq of cesium released during the FDNPP disaster. The time needed for surface sediment activities (0 to 3 cm) at the 20 locations to be reduced by 50% via sediment mixing was estimated to range from 0.4 to 26 yr. Due to the observed variability in mixing rates, grain size, and inventories, additional cores are needed to improve these estimates and capture the full extent of cesium penetration into the shallow coastal sediments, which was deeper than 14 cm for all cores retrieved from water depths less than 150 m.

A Creep Model for Solder Alloys

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Yongchang Lee ◽  
Cemal Basaran
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Diffusion Processes ◽  
Dislocation Motion ◽  
Creep Model ◽  
Solder Alloys ◽  
Creep Models ◽  
And Diffusion ◽  
Cycling Loading

Demand for long-term reliability of electronic packaging has lead to a large number of studies on viscoplastic behavior of solder alloys. Various creep models for solder alloys have been proposed. They range from purely empirical to mechanism based models where dislocation motion and diffusion processes are taken into account. In this study, most commonly used creep models are compared with the test data and implemented in ABAQUS to compare their performance in cycling loading. Finally, a new creep model is proposed that combines best features of many models. It is also shown that, while two creep models may describe the same material stress–strain rate curves equally well, they may yield very different results when utilized for cycling loading. One interesting observation of this study is that the stress exponent, n., also depends on the grain size.

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