Kinetics Analysis of Direct Nitridation of Silicon Powders at Atmospheric Pressure

Silicon nitride powders were prepared via direct nitridation of silicon powders diluted with -Si3N4at atmospheric pressure. The nitridation temperature and time were ranged from1623K to 1823K and from 0 minute to 20 minutes respectively. Based on the relations between the conversion rate of silicon and the time at different temperatures, and using shrinking core model, a simple model for the reaction between silicon and nitrogen was derived. The model showed that the relations between the conversion rate of silicon and the time displayed asymptotic exponential conversion trend. Using this model, the kinetics parameters of nitridation of silicon powder at atmospheric pressure were calculated, including pre-exponential factor in Arrhenius equation, activation energy, effective diffusion coefficient, and the formula of the reaction rate constant.

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Not Reacted Core Model Applied in Palm Nut Shell Pyrolysis

International Journal of Chemical Engineering ◽

10.1155/2019/9561265 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8

Author(s):

Ernesto de la Torre ◽

Sebastián Gámez

Keyword(s):

Kinetic Parameters ◽

Elaeis Guineensis ◽

Effective Diffusion ◽

Reaction Rate Constant ◽

Core Model ◽

Scanning Calorimetry ◽

Differential Scanning Calorimetry Study ◽

Different Temperatures ◽

Char Conversion ◽

Pyrolysis Of Biomass

One of the main sources of activated carbon is biomass which can be transformed into char by pyrolysis. Apart from the obtaining coal, the pyrolysis of biomass can be used for the preparation of fuels, and this is why it is very important to determine its kinetic parameters for modelling. In the present research, the pyrolysis enthalpy of palm nut shells (Elaeis guineensis) was determined with the use of a differential scanning calorimetry study (DSC). To determine the kinetic parameters, the Not Reacted Core model was employed. This model considers that there is a heat and mass gradient between the furnace atmosphere and the interface formed during pyrolysis. To obtain the required data for the model, palm nut shells were submitted to pyrolysis in a Nichols furnace under reducing atmosphere. Samples were taken every 10 minutes to calculate char conversion. The experimental pyrolysis enthalpy resulted to be 301.81 J/g and then the monomeric units of cellulose, hemicellulose, and lignin were employed in order to determine the pyrolysis enthalpy per mole. The three biopolymers react with different mechanisms at different temperatures. The molecular weight resulted to be 172.38 g/mole, and the enthalpy for pyrolysis was 52.03 kJ/mol. For the application of the Not Reacted Core model, the amorphous char heat transfer coefficient was selected, and the value is 1.6 J/s·m·K. The reaction rate constant was 6.64 × 10−9 1/s assuming a first-order reaction, whereas the effective diffusion across the char layer was 4.83 × 10−7 m2/s.

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Effect of the Addition of α-Si3N4 on the Direct Nitridation of Silicon Powder at Atmospheric Pressure

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.486.247 ◽

2012 ◽

Vol 486 ◽

pp. 247-252 ◽

Cited By ~ 4

Author(s):

Fu Ming Yang ◽

Li Wang ◽

Shao Wu Yin ◽

Yan Hui Li ◽

Chuan Ping Liu ◽

...

Keyword(s):

Silicon Nitride ◽

Atmospheric Pressure ◽

Silicon Powder ◽

Initial Increase ◽

Β Phase ◽

Peak Point ◽

Direct Nitridation

Effect of the addition of α-Si3N4 on the nitridation of silicon powder was studied at 1550 and atmospheric pressure. Silicon powder of 2.2μm in size and 99.99% in purity was adopted as experimental materials, α-Si3N4 powder of 2.2μm in size and 99% in purity was used as diluent, and nitrogen of 99.9993% in purity was used as reaction gas. The morphologies and phase compositions of the products were analyzed by SEM and XRD respectively. The results show that the conversion of silicon is improved considerably by increasing the adding proportion of α-Si3N4 diluent. When the adding proportion of α-Si3N4 increases from 10% to 50%, the conversion of silicon powder increases from 38% to 92.55%. The content of β-Si3N4 in product decreases, after an initial increase, with the adding proportion of α-Si3N4 increases, and it reaches the peak point when the adding proportion of α-Si3N4 was 30%. The sinterability of silicon nitride decreases as the content of β phase increases, so the adding proportion of α-Si3N4 should be kept away from 30%.

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Simulation Studies on Transformation of Mercury during Combustion Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1092-1093.912 ◽

2015 ◽

Vol 1092-1093 ◽

pp. 912-916

Author(s):

Jian Yi Lu ◽

Jie Gao ◽

Cheng Long Meng

Keyword(s):

Combustion Process ◽

Reaction Rate Constant ◽

Transformation Mechanism ◽

Exponential Factor ◽

Homogeneous Oxidation ◽

Constant Change ◽

Different Temperatures ◽

Oxidation Model ◽

Reaction Activation Energy ◽

Kinetics Of

Mercury is one of important trace heavy metal elements and about 1/3 of mercury in the air comes from emissions of coal-fired flue gas. In this study, we simulated mercury’s 4 important reactions of the oxidation kinetics mechanism and got every reactions’ rate variations; meanwhile we studied the kinetics of four reactions and got the reacting paths, five pre-exponential factor in different temperatures, reaction activation energy change and reaction rate constant change, a relatively comprehensive homogeneous oxidation model established. Through the above simulation study, the kinetics and thermodynamics parameters of 4 primitive reactions are obtained, having a great benefit for understanding the transformation mechanism of mercury in the process of coal combustion.

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Effect of Si3N4 diluent on direct nitridation of silicon powder

Ceramics International ◽

10.1016/j.ceramint.2019.02.175 ◽

2019 ◽

Vol 45 (8) ◽

pp. 10943-10950 ◽

Cited By ~ 1

Author(s):

Xing Jin ◽

Pengfei Xing ◽

Yanxin Zhuang ◽

Jian Kong ◽

Shengnan Jiang ◽

...

Keyword(s):

Silicon Powder ◽

Direct Nitridation

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Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

Revista Brasileira de Engenharia Agrícola e Ambiental ◽

10.1590/1807-1929/agriambi.v20n2p174-180 ◽

2016 ◽

Vol 20 (2) ◽

pp. 174-180 ◽

Cited By ~ 8

Author(s):

Hellismar W. da Silva ◽

Renato S. Rodovalho ◽

Marya F. Velasco ◽

Camila F. Silva ◽

Luís S. R. Vale

Keyword(s):

Experimental Data ◽

Activation Energy ◽

Free Energy ◽

Thermodynamic Properties ◽

Gibbs Free Energy ◽

Removal Rate ◽

Effective Diffusion ◽

Drying Time ◽

Three Samples ◽

Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

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Superior Degradation Performance of Nanoporous Copper Catalysts on Methyl Orange

Metals ◽

10.3390/met11060913 ◽

2021 ◽

Vol 11 (6) ◽

pp. 913

Author(s):

Jinyi Wang ◽

Sen Yang

Keyword(s):

Activation Energy ◽

Methyl Orange ◽

High Efficiency ◽

Low Cost ◽

Degradation Process ◽

Copper Catalysts ◽

Reaction Rate Constant ◽

Nanoporous Structure ◽

Intra Particle Diffusion ◽

Different Temperatures

The development of low-cost and high-efficiency catalysts for wastewater treatment is of great significance. Herein, nanoporous Cu/Cu2O catalysts were synthesized from MnCu, MnCuNi, and MnCuAl with similar ligament size through one-step dealloying. Meanwhile, the comparisons of three catalysts in performing methyl orange degradation were investigated. One of the catalysts possessed a degradation efficiency as high as 7.67 mg·g−1·min−1. With good linear fitting by the pseudo-first-order model, the reaction rate constant was evaluated. In order to better understand the degradation process, the adsorption behavior was considered, and it was divided into three stages based on the intra-particle diffusion model. Three different temperatures were applied to explore the activation energy of the degradation. As a photocatalytic agent, the nanoporous structure of Cu/Cu2O possessed a large surface area and it also had low activation energy, which were beneficial to the excellent degradation performance.

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Thermal Conductivities of Choline Chloride-Based Deep Eutectic Solvents and Their Mixtures with Water: Measurement and Estimation

Molecules ◽

10.3390/molecules25173816 ◽

2020 ◽

Vol 25 (17) ◽

pp. 3816

Author(s):

Taleb H. Ibrahim ◽

Muhammad A. Sabri ◽

Nabil Abdel Jabbar ◽

Paul Nancarrow ◽

Farouq S. Mjalli ◽

...

Keyword(s):

Atmospheric Pressure ◽

Choline Chloride ◽

Deep Eutectic Solvents ◽

Standard Uncertainty ◽

Heat Transfer Fluids ◽

Wide Range ◽

Different Temperatures ◽

Experimental Values ◽

Water Measurement ◽

Thermal Conductivities

The thermal conductivities of selected deep eutectic solvents (DESs) were determined using the modified transient plane source (MTPS) method over the temperature range from 295 K to 363 K at atmospheric pressure. The results were found to range from 0.198 W·m−1·K−1 to 0.250 W·m−1·K−1. Various empirical and thermodynamic correlations present in literature, including the group contribution method and mixing correlations, were used to model the thermal conductivities of these DES at different temperatures. The predictions of these correlations were compared and consolidated with the reported experimental values. In addition, the thermal conductivities of DES mixtures with water over a wide range of compositions at 298 K and atmospheric pressure were measured. The standard uncertainty in thermal conductivity was estimated to be less than ± 0.001 W·m−1·K−1 and ± 0.05 K in temperature. The results indicated that DES have significant potential for use as heat transfer fluids.

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Molecular Interactions Investigation of L-Histidine in Water and in Aqueous Citric Acid at Different Temperatures Using Volumetric and Acoustic Methods

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2017-0977 ◽

2018 ◽

Vol 232 (3) ◽

pp. 393-408 ◽

Cited By ~ 5

Author(s):

Dinesh Kumar ◽

Shashi Kant Sharma

Keyword(s):

Citric Acid ◽

Molar Volume ◽

Atmospheric Pressure ◽

Apparent Molar Volume ◽

Adiabatic Compressibility ◽

Acid Solutions ◽

Solvent Interactions ◽

Intermolecular Free Length ◽

Acoustic Methods ◽

Different Temperatures

AbstractDensities,ρand ultrasonic speeds, u of L-histidine (0.02–0.12 mol·kg−1) in water and 0.1 mol·kg−1aqueous citric acid solutions were measured over the temperature range (298.15–313.15) K with interval of 5 K at atmospheric pressure. From these experimental data apparent molar volume ΦV, limiting apparent molar volume ΦVOand the slopeSV, partial molar expansibilities ΦEO, Hepler’s constant, adiabatic compressibilityβ, transfer volume ΦV, trO, intermolecular free length (Lf), specific acoustic impedance (Z) and molar compressibility (W) were calculated. The results are interpreted in terms of solute–solute and solute–solvent interactions in these systems. It has also been observed that L-histidine act as structure maker in water and aqueous citric acid.

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Reaction Kinetics of Iron Oxides in Ok Tedi Magnetite Skarn Ore

Asian Journal of Physical and Chemical Sciences ◽

10.9734/ajopacs/2020/v8i430121 ◽

2020 ◽

pp. 1-13

Author(s):

Mary Kama ◽

Kaul Gena ◽

Tindi Seje Nuru

Keyword(s):

Reaction Kinetics ◽

Papua New Guinea ◽

Iron Reduction ◽

New Guinea ◽

Reaction Rate Constant ◽

Close Monitoring ◽

Significant Difference ◽

Different Temperatures ◽

C 30 ◽

Kinetics Of

Magnetic skarn ore (MSO) is one of the major copper bearing ore extracted by the Ok Tedi Copper Mine in Papua New Guinea (PNG). Copper minerals are recovered by flotation while the iron not associated with copper are discarded as tailings. The objective of this investigation was to determine the iron ore reduction kinetics for the Ok Tedi MSO and ascertain if it can be processed to produce sponge iron for a mini steel plant in Papua New Guinea. SEM-EDAX analyses of the Ok Tedi MSO indicated 10.1% C, 30% O, 0.6% Mg, 1.1% Si, 21.1% S, 0.8% Ca and 36.2 % Fe. Most of the iron is in sulfide form. Both naturally occurring and roasted sinters of Ok Tedi MSO samples of different particle sizes were reduced by charcoal carbon at three different temperatures and seven different reduction times. Analyses of the reduced products indicated a metallic iron content of more than 65 wt. % on average. Results showed that there was no significant difference in reduction between fluxed and control materials. Only a slight increase in kinetics with reduced particle size, hence the reaction rate constant (K) did not vary much within the temperatures investigated. Reaction kinetics increases with increasing reduction time at 900°C. Therefore, more iron reduction is observed with particles of 106 µm size. In addition, the results also confirmed that the reduction energy used was higher at 800°C and lower at 1000°C. In conclusion, iron reduction can be improved but close monitoring of temperature and reduction times are essential to determine the reaction kinetics of the Ok Tedi MSO.

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