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Wyświetlanie 1-15 z 81
Tytuł:
An analysis of non-isothermal primary crystallization kinetics of Fe95Si5 amorphous alloy
Autorzy:
Frączyk, Adam
Kuś, Krzysztof
Wojtkowiak, Adam
Powiązania:
https://bibliotekanauki.pl/articles/950068.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie
Tematy:
metallic glass
energy activation
Avrami exponent
crystallization kinetics parameter
DSC
Opis:
The paper describes the primary crystallization of metallic Fe95Si5 glass which was studied by differential scanning calorimetry (DSC) with non-isothermal methods. The activation energy of crystal transformation was calculated with the equations proposed by Kissinger, Mahadevan and a modified version of the equation developed by Augis and Bennett. Activation energy was determined at Ea = 242.0 - 254.2 kJ / mol, subject to the applied method. The Avrami exponent of crystallization in the amorphous phase n was determined in the range of n = 2.40 - 2.52, depending on the method of calculating the transformation of activation energy.
Źródło:
Technical Sciences / University of Warmia and Mazury in Olsztyn; 2019, 22(3); 237-247
1505-4675
2083-4527
Pojawia się w:
Technical Sciences / University of Warmia and Mazury in Olsztyn
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetics of pearlite spheroidization
Autorzy:
Matusiewicz, P.
Augustyn-Nadzieja, J.
Czarski, A.
Skowronek, T.
Powiązania:
https://bibliotekanauki.pl/articles/352748.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
pearlite spheroidization
sterology
activation energy
Opis:
The pearlite spheroidization in Fe-0.76%C high purity steel was investigated. The samples of a coarse pearlite microstructure were isothermal annealed at 700, 680, 660, 640 and 620°C for various times, up to 800 hours. For quantitative description of the spheroidization process stereological parameter, SV (ferrite/cementite interface surface density) was used. The activation energy 104.8±11.4 kJ/mol was found for the spheroidization process. This value shows good agreement with the activation energy for iron and carbon diffusion along a ferrite/cementite interface, so the coupled interface diffusion is the rule-controlling process.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 1; 231-234
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermogravimetry of chitosan with nanofillers
Autorzy:
Puchalska, Anna
Mucha, Maria
Powiązania:
https://bibliotekanauki.pl/articles/1035418.pdf
Data publikacji:
2011
Wydawca:
Sieć Badawcza Łukasiewicz - Polskie Towarzystwo Chitynowe
Tematy:
activation energy
biopolymers
chitosan
thermogravimetry
Opis:
In the present paper the degradation of chitosan and its blends with hydroxyapatite, nanoclay and nanosilver as well as the impact of those nanofillers added to chitosan on its decomposition at high temperatures are studied. The applied films of thickness 50 μm were obtained by casting the acidic solutions: chitosan and its blends with hydroxyapatite, nanoclay and nanosilver. To mix solutions with nanofillers ultrasounds were applied. To study the thermal degradation we applied thermogravimetry in dynamic and static conditions, which is a method of thermal analysis involving the continuous recording of weight loss Based on experimental data activation energies of thermal decomposition close to a maximum rate loss were calculated using different methods for chitosan and its blends with hydroxyapatite, nanoclay and nanosilver. The addition of three nanofillers mentioned above result in a visual increase of activation energy of thermal degradation process of chitosan due to slower evolution of decomposed gases from chitosan matrix reflected by a slower rate of weight loss.
Źródło:
Progress on Chemistry and Application of Chitin and its Derivatives; 2011, 16; 31-42
1896-5644
Pojawia się w:
Progress on Chemistry and Application of Chitin and its Derivatives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Boride Layer Growth Kinetics of AISI H13 Steel Borided with Nano-Sized Powders
Autorzy:
Karakaş, M. S.
Günen, A.
Kanca, E.
Yilmaz, E.
Powiązania:
https://bibliotekanauki.pl/articles/351842.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
boriding
growth kinetics
activation energy
Opis:
Growth kinetics of boride layers in AISI H13 steel was investigated using the pack boriding method at temperatures of 1073, 1173 and 1273 K (800°C, 900°C and 1000°C) for periods of 2, 4 and 6 h with nano-sized boron (NB) and micron-sized Ekabor II powders as boriding agents. The total thickness of the boride layer (including both FeB and Fe2B) after boriding at 1273 K (1000°C) for 6 h was 103.8 μm and 96.5 μm for the NB and Ekabor II specimens, respectively. X-ray diffraction analysis of the boride layers on the surfaces borided with NB and Ekabor II revealed the presence of FeB and Fe2B phases with sawtooth morphology. The FeB/Fe2B volume ratio was higher in the specimens borided with NB. The thickness of the boride layer (FeB + Fe2B) increased with the increasing boriding temperature and time. The FeB layer in the NB specimen displayed a (002) preferred orientation.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 1; 159-165
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic Studies of Pt(IV) Chloride Complex Ions Reduction Reaction Using Potassium Formate
Autorzy:
Wojnicki, M.
Żabiński, P.
Csapó, Edit
Powiązania:
https://bibliotekanauki.pl/articles/351194.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
platinum
recovery
recycling
activation energy
reaction mechanism
Opis:
In this paper, the kinetics of the platinum(IV) chloride complex ions reduction reaction was studied. It was shown that the mechanism exhibits autocatalytic character. The presence of metallic platinum in the system significantly increases the reaction rate. The influence of the initial concentration of precursor, reductant, ionic strength, initial concentration of the chloride ions as well as the temperature on the process rate was investigated. The activation energy was determined and is equal to 93.57 kJ/mol. Moreover, the obtained metallic phase was analyzed, and it was observed that it has a micrometric size.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 3; 1135-1140
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on the Mechanism and Kinetics of Polymorphic Transitions of ε CL-20 in Composite Systems
Autorzy:
Guo, X.-Y.
Zhang, P.
Xu, J.-J.
Wang, Z.-H.
Jiao, Q.-J.
Powiązania:
https://bibliotekanauki.pl/articles/358032.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
polymorphic transition
kinetics
activation energy
transition temperature
Opis:
In order to explore the polymorphic transition law for ε-CL-20 in composite systems, the polymorphic transition process of pure ε-CL-20 crystals stimulated by heat was investigated by the X-ray Diffraction (XRD) method, and the kinetic parameters of the polymorphic transition process were calculated (including the apparent activation energy Ea and the pre-exponential factor lnA). Meanwhile the effects of different additives on the polymorphic transition process and kinetics of ε-CL-20 were explored in detail. The experimental results showed that the ε-form tends to transform into the γ- form on heating and that the Ea and lnA for the transition process were 209.97 kJ/mol and 57.47, respectively. The first group of additives clearly promoted the polymorphic transition of ε-CL-20 and lowered the initial transition temperature and the activation energy. The second and third groups of additives inhibited the polymorphic transition of ε-CL-20 and raised the initial transition temperature and the activation energy.
Źródło:
Central European Journal of Energetic Materials; 2015, 12, 4; 689-702
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of leaching kinetics of cerussite in sodium hydroxide solutions
Autorzy:
Feng, Q.
Wen, S.
Wang, Y.
Zhao, W.
Deng, J.
Powiązania:
https://bibliotekanauki.pl/articles/110621.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
cerussite
sodium hydroxide
leaching
kinetics
activation energy
Opis:
The leaching kinetics of cerussite in alkaline medium was investigated with respect to experimental variables such as sodium hydroxide concentration, temperature, particle size and stirring speed. The results showed that leaching reagent concentration and reaction temperature exerted significant effects on the extraction of lead, whereas particle size and stirring speed exhibited a relatively moderate effect on the leaching rate. The leaching process followed the kinetic law of the shrinking core model, and the dissolution rates were controlled by the surface chemical reaction with an apparent activation energy value of 43.79 kJ/mol. A corresponding dissolution kinetic equation was also proposed to describe the dissolution reaction. The results indicated that sodium hydroxide could be used as an effective leaching reagent for extracting lead from cerussite.
Źródło:
Physicochemical Problems of Mineral Processing; 2015, 51, 2; 491-500
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ethylene Glycol Dinitrate (EGDN): from Commercial Precursors, Physicochemical and Detonation Characterization
Autorzy:
Fettaka, H.
Lefebvre, M.
Powiązania:
https://bibliotekanauki.pl/articles/358286.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
EGDN
liquid explosive
precursor
activation energy
detonation tests
Opis:
Currently, liquid explosives pose a potential threat. An important phase in the assessment of this threat is to investigate the various synthesis paths leading to their manufacture and to evaluate the potential use of readily purchasable precursors. The aim of this work was to assess the synthesis of Ethylene Glycol Dinitrate (EGDN), a liquid nitrate ester explosive, using commercially available precursors. The characteristics of the synthetic process (ease, yield), the chemical properties of the synthesized product (purity, spectra) and its explosive properties (sensitivities, detonability) were investigated. Comparisons are drawn between these products and the product obtained using laboratory ingredients. Three ingredients have been used: 1) ethylene glycol, laboratory grade, 2) ready to use, commercial coolant fluid, and 3) ethylene glycol extracted from commercial coolant fluid. The chemical composition and purity of the synthesized liquid explosive was analyzed by Gas Chromatography-Mass Spectrometry (GCMS), and infrared spectroscopy (IR). Differential Scanning Calorimetric (DSC) analysis allowed the heat of decomposition and activation energies to be assessed. The Ozawa and Kissinger models were used. The explosive properties of the pure synthesized products and comparable other explosives, have been tested. The potential use as a priming charge or as a main charge was assessed.
Źródło:
Central European Journal of Energetic Materials; 2015, 12, 2; 287-305
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal and kinetic analysis of pure and contaminated ionic liquid: 1-butyl-2.3-dimethylimidazolium chloride (BDMIMCl)
Autorzy:
Muhammad, A.
Powiązania:
https://bibliotekanauki.pl/articles/949468.pdf
Data publikacji:
2016
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
ionic liquid
thermal stability
kinetic analysis
activation energy
Opis:
In this research work, thermal decomposition and kinetic analysis of pure and contaminated imidazolium based ionic liquid (IL) has been investigated. As thermal decomposition and kinetics evaluation plays a pivotal role in effective process design. Therefore, thermal stability of pure 1-butyl-2,3-dimethylimidazolium chloride (BDMIMCl) was found to be higher than the sample of IL with the addition of 20% (wt.) NH4Cl as an impurity. The activation energy of thermal degradation of IL and other kinetic parameters were determined using Coats Redfern method. The activation energy for pure IL was reduced in the presence of NH4Cl as contaminant i.e., from 58.7 kJ/mol to 46.4 kJ/mol.
Źródło:
Polish Journal of Chemical Technology; 2016, 18, 2; 122-125
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Arrheniusan activation energy of separation for different parameters regulating the process
Autorzy:
Drzymała, J.
Powiązania:
https://bibliotekanauki.pl/articles/109713.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
flotation
activation energy
separation
Gibbs potential
Arrhenius plot
Opis:
The Arrhenius model, that relates the activation energy with the kinetic constant and process temperature, was applied for flotation as a separation process, and next was extended to other incentive parameters such as the frother concentration, NaCl content and hydrophobicity. It was shown that determination of the activation energy caused by other incentive parameters (i.e. particle size, surface potential) was also possible. The units of the activation energy depend on the type of the separation process and incentive parameter. For contact angle regulating flotation the activation energy unit is mJ/m2, while for the frother concentration is J. It is known that instead in joules, the activation energy can also be expressed in J/mol and in kT or RT units, where k is the Boltzmann constant, R gas constant and T is absolute temperature in kelvins. Even though different formulas of the specific Gibbs potential were used for calculation of activation energy caused by various incentive parameters, there was generally a good agreement between the extend of changes of the first order kinetic constants of the process and activation energy value. It was found that for flotation of copper-bearing carbonaceous shale the activation energy was equal to 1.1 kT for NaCl as the incentive parameter, 3.0 kT for temperature and 32.7 kT for butyl diethylglycol ether used as a flotation frother. For methylated quartz the hydrophobicity-induced activation energy was 42 mJ/m2 for contact angle as the incentive parameter.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 4; 1152-1158
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A procedure of Arrhenius activation energy determination for salt flotation of particles in the vicinity of one molar salt aqueous solutions
Autorzy:
Ratajczak, Tomasz
Kurkiewicz, Szymon
Drzymala, Jan
Powiązania:
https://bibliotekanauki.pl/articles/1450643.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
activation energy
salt flotation
Arrhenius equation
Gibbs potential
Opis:
A modified Arrhenius equation, in which thermal energy is replaced with chemical (Gibbs) potential, and a special calculation procedure were used to evaluate the flotation activation energy for salt solutions in the one molar range of concentrations. The proposed formula overcomes the difficulties of calculating the salt flotation activation energy caused by mathematical problems of finding 1/(ln($c$/$c_o$)) for the standard salt concentration $C_o$ =1 M (1 kmol/m3 and when the applied salt concentration c is in the vicinity of 1 M. The salt flotation activation energy was calculated for flotation of copper-bearing carbonaceous shale in the 0.25, 0.50, 1.00 and 2.00 M NaCl solutions performed in a laboratory machine as equal to 1.9 RT for standard salt solution equal to 1 M.
Źródło:
Physicochemical Problems of Mineral Processing; 2020, 56, 6; 1-5
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal behavior and kinetic decomposition of sweet potato starch by non-isothermal procedures
Autorzy:
Liu, Ying
Yang, Liutao
Zhang, Yingzhe
Powiązania:
https://bibliotekanauki.pl/articles/240460.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
starch
kinetic analysis
thermal degradation
activation energy
mechanism
Opis:
In this study, X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry (DSC) method were used to analyze the main characteristics of sweet potato starch, and to analyze the thermal degradation process of sweet potato starch. Specifically, X-ray diffraction to study its structure, thermogravimetric analysis to study the thermal degradation kinetics, and differential scanning calorimetry to study the thermogram of sweet potato starch. The thermal decomposition kinetics of sweet potato starch was examined within different heating rates in nitrogen atmosphere. Different models of kinetic analysis were used to calculate the activation energies using thermogravimetric data of the thermal degradation process. Activation energies obtained from Kissinger, Flynn-WallOzawa, and Šatava-Šesták models were 173.85, 174.87 and 174.34 kJ/mol, respectively. The values of activation energy indicated that the thermal degradation of the sweet potato starch was a single reaction mechanism or the combination of multi-reaction mechanisms. The differential scanning calorimetry analysis show that two decomposition stages were presented: the first at a low temperature involves the decomposition of long chain; and the second at a high temperature represents the scission of glucose ring. This information was helpful to design the processing process of many natural polymers. Thermogravimetric Fourier transform-infrared (TG–FTIR) analysis showed that the main pyrolysis products included water, methane, carbon dioxide, ammonia, and others.
Źródło:
Archives of Thermodynamics; 2019, 40, 4; 67-82
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of the Semtex Matrix on the Thermal Behavior and Decomposition Kinetics of Cyclic Nitramines
Autorzy:
Yan, Q. L.
Zeman, S.
Elbeih, A.
Zbyněk, A.
Powiązania:
https://bibliotekanauki.pl/articles/357984.pdf
Data publikacji:
2013
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
cyclic nitramines
thermal decomposition
activation energy
Semtex
PBX
Opis:
The thermal behavior and decomposition kinetics of Semtex 10 polymeric matrix (Semtex) bonded PBXs containing RDX (1,3,5-trinitro 1,3,5-triazinane), HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX (cis-1,3,4,6tetranitrooctahydroimidazo [4,5-d] imidazole), HNIW (2,4,6,8,10,12-hexanitro2,4,6,8,10,12-hexaazaisowurtzitane) have been investigated by means of nonisothermal TG and DSC techniques. It is shown that only a single decomposition process occurs for RDX-SE and HMX-SE whilst an obvious two-step process occurs for CL-20-SE and BCHMX-SE. The onset of the exotherms were observed at 210.6, 239.7, 279.2 and 229.4 °C with the peak maxima at 232.2, 249.4, 280.4 and 240.2 °C, and energy changes of 1808, 2140, 612 and 1757 J·g-1 for RDX-SE, BCHMX-SE, HMX-SE and CL-20-SE, respectively. It has been found that the Semtex matrix has little influence on the activation energy distribution for RDX, BCHMX and ε-CL-20. The activation energies for BCHMX-SE and CL-20-SE decomposition are almost independent of the degree of conversion, with mean values of 159.6 ±1.9 and 187.3 ±1.8 kJ·mol-1. It has been proved that Semtex and Viton A are better binders than C4 and Formex for ε-CL-20 and RDX based PBXs in terms of their greater thermal stability, and Formex is a poor binder for BCHMX.
Źródło:
Central European Journal of Energetic Materials; 2013, 10, 4; 509-528
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-isothermal Studies on the Thermal Decomposition of C4 Explosive Using the TG/DTA Technique
Autorzy:
Pouretedal, H. R.
Damiri, S.
Ghaemi, E. F.
Powiązania:
https://bibliotekanauki.pl/articles/358520.pdf
Data publikacji:
2014
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
C4 explosive
non-isothermal
decomposition
activation energy
Opis:
The thermal behaviour of energetic materials is very important for their safe production, storage, handling and even demilitarization. In this work, the thermal behaviour and decomposition kinetics of conventional C4 plastic explosive has been studied experimentally by a non-isothermal thermogravimetric (TG)/differential thermal analysis (DTA) technique at different heating rates (2, 4, 6 and 8 °C·min-1). The kinetic triplet of activation energy, frequency factor and model of thermal decomposition of this compound has been evaluated via model-fitting and model-free methods. The results show a single thermal decomposition process for C4, with the model of integral function (g(α)) of [(1−α)-1/3 −1]2 and differential function (f(α)) of [(1−α)2/3(3α−3)/2(1−α)1/3−2], indicating a 3-dimensional diffusion mechanism. In addition, Ea values of 207.1 ± 17.3, and 241 kJ·mol-1, by using the isoconversional model-free modified Kissinger-Akahira-Sunose (KAS) and the Kissinger method, respectively, were obtained for the conversion interval of 0.3-0.7. The C4 matrix shows a significant effect on the activation energy distribution of pure RDX.
Źródło:
Central European Journal of Energetic Materials; 2014, 11, 3; 405-416
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural and functional changes of bovine carbonic anhydrase as a consequence of temperature.
Autorzy:
Sarraf, N
Saboury, A
Ranjbar, B
Moosavi-Movahedi, A
Powiązania:
https://bibliotekanauki.pl/articles/1041543.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
activation energy
Arrhenius plot
circular dichroism
bovine carbonic anhydrase
Opis:
The temperature dependence of the activity and structure of the enzyme carbonic anhydrase was studied. The Arrhenius plot shows a jump which is seen usually in proteins with more than one subunit or with one subunit but more than one domain. Since carbonic anhydrase has only one subunit with one domain, the fine conformational changes of the protein motifs could only be detected through circular dichroism polarimetry. It seems that the jump in Arrhenius plot is a result of some slight structural changes in the secondary and tertiary structures of the enzyme.
Źródło:
Acta Biochimica Polonica; 2004, 51, 3; 665-671
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 81

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