Cryomilling and Characterization of Metal/Ceramic Powders

2012 ◽  
Vol 512-515 ◽  
pp. 127-131 ◽  
Author(s):  
Qing Hou ◽  
Zhi Cheng Shi ◽  
Run Hua Fan ◽  
Li Cheng Ju
Keyword(s):  
Liquid Nitrogen Temperature ◽  
Mechanochemical Reaction ◽  
Solid Reaction ◽  
Scanning Calorimetry ◽  
Model Free ◽  
Particle Size Analyzer ◽  
Long Time ◽  
Solid Liquid ◽  
Kinetics Of

Al/Fe2O3 thermite powders were prepared by cryomilling at liquid nitrogen temperature. The cryogenic temperature will restrain the mechanochemical reaction between alumina and iron oxide, leading to high reactivitive nanoscale powders. The size distribution of the powders was analyzed using laser particle size analyzer, and cryomilling was proved to be an effective method to prepare ultrafine powders. The differential scanning calorimetry (DSC) analysis indicated that the cryomilled powders get more fully-reacted, a larger proportion of solid-solid reaction and more heat release in the solid-liquid reaction, comparing with the powders milled at room temperaure. Furthermore, the reaction kinetics of Al-Fe2O3 system is analyzed by a model-free Starink method. The activation energy for solid-solid reaction of 2Al-Fe2O3 thermite mixture cryomilled for 40 min is determined as 250 kJ/mol. The alternating gradient magnetometer (AGM) analysis shows that long time milling evoked the thermit reaction between Al and Fe2O3, leading to the increase in saturation magnetization (Ms) and remanent magnetization (Mr).

scholarly journals Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1686
Author(s):  
Andrey Galukhin ◽  
Roman Nosov ◽  
Ilya Nikolaev ◽  
Elena Melnikova ◽  
Daut Islamov ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Single Step ◽  
Polymerization Kinetics ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Polymerization Product ◽  
The One ◽  
Kinetics Of

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics. A transition of polymerization from a kinetic- to a diffusion-controlled regime is detected. Kinetic analysis is performed by combining isoconversional and model-based computations. It demonstrates that polymerization in the kinetically controlled regime of the present monomer can be described as a quasi-single-step, auto-catalytic, process. The diffusion contribution is parameterized by the Fournier model. Kinetic analysis is complemented by characterization of thermal properties of the corresponding polymerization product by means of thermogravimetric and thermomechanical analyses. Overall, the obtained experimental results are consistent with our hypothesis about the relation between the rigidity and functionality of the cyanate ester monomer, on the one hand, and its reactivity and glass transition temperature of the corresponding polymer, on the other hand.

Effect of Soy Protein on Kinetics of Polyurethane Formation

2010 ◽  
Vol 160-162 ◽  
pp. 1712-1715
Author(s):  
Guang Heng Wang
Keyword(s):  
Soy Protein ◽  
Soy Protein Isolate ◽  
Kissinger Method ◽  
Toluene Diisocyanate ◽  
Polymerization Reaction ◽  
Dibutyltin Dilaurate ◽  
Ozawa Method ◽  
Scanning Calorimetry ◽  
Model Free ◽  
Kinetics Of

The polymerization reaction kinetics of biodegradable polyurethane extended with soy protein isolate (SPI) with dibutyltin dilaurate (DBTDL) as the curing catalyst was studied by means of non-isothermal differential scanning calorimetry (DSC). Model-free methods, Kissinger method and Ozawa method, were applied for analyzing the DSC data. The Ea and lnA obtained from Kissinger method for catalyzed reaction between toluene diisocyanate (TDI) and Polyoxypropyleneglycol (PPG) are 60.80 kJ•mol-1 and 12.09, and for catalyzed reaction among TDI, PPG, and SPI they were 65.91 kJ•mol-1and 14.04. Similarly the Ea obtained from Ozawa method for catalyzed reaction between TDI and PPG and catalyzed reaction among TDI, PPG, and SPI were 63.49 kJ•mol-1 and 64.78 kJ•mol-1, respectively. The results showed that, the incorporation of a small amount of SPI into polyurethane did not affect the reaction kinetic strongly, but increases the reaction activation energy Ea and lnA.

Preparation and Crystallization Kinetics of FeSiB Amorphous Ribbons under Non-Isothermal Regime

2014 ◽  
Vol 605 ◽  
pp. 35-38
Author(s):  
Eirini Varouti
Keyword(s):  
Thermal Stability ◽  
Differential Scanning Calorimetry ◽  
Chemical Composition ◽  
Crystallization Kinetics ◽  
Structural Changes ◽  
Scanning Calorimetry ◽  
Amorphous Ribbons ◽  
Isothermal Regime ◽  
Kinetics Of

The aim of the present work was the preparation and characterization of FeSiB amorphous magnetic ribbons with the following chemical composition: Fe80SixB20-x, x=5,6,8 and Fe75Si15B10. Differential Scanning Calorimetry was employed in order to study the thermal stability and structural changes during the transformations that took place. Much emphasis is placed on the analysis of the crystallization kinetics.

Characterization of Nanocrystalline γ–Fe2O3Prepared by Wet Chemical Method

1999 ◽  
Vol 14 (4) ◽  
pp. 1570-1575 ◽  
Author(s):  
G. Ennas ◽  
G. Marongiu ◽  
A. Musinu ◽  
A. Falqui ◽  
P. Ballirano ◽  
...  
Keyword(s):  
Isothermal Treatment ◽  
X Ray Diffraction ◽  
Ferrous Chloride ◽  
Scanning Calorimetry ◽  
Direct Transformation ◽  
X Ray ◽  
Transmission Electron ◽  
Xrd Techniques ◽  
Kinetics Of

Homogeneous maghemite (γ–Fe2O3) nanoparticles with an average crystal size around 5 nm were synthesized by successive hydrolysis, oxidation, and dehydration of tetrapyridino-ferrous chloride. Morphological, thermal, and structural properties were investigated by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and x-ray diffraction (XRD) techniques. Rietveld refinement indicated a cubic cell. The superstructure reflections, related to the ordering of cation lattice vacancies, were not detected in the diffraction pattern. Kinetics of the solid-state phase transition of nanocrystalline maghemite to hematite (α–Fe2O3), investigated by energy dispersive x-ray diffraction (EDXRD), indicates that direct transformation from nanocrystalline maghemite to microcrystalline hematite takes place during isothermal treatment at 385 °C. This temperature is lower than that observed both for microcrystalline maghemite and for nanocrystalline maghemite supported on silica.

SOĞUK HADDELENMİŞ AA3105 VE AA5005 LEVHALARIN DSC ANALİZİ İLE YENİDEN KRİSTALLENME KİNETİĞİ

2021 ◽  
Vol 8 (17) ◽  
pp. 80-85
Author(s):  
Atae RAOUGUI ◽  
Ion GRECU ◽  
Volkan Murat YILMAZ ◽  
Kenan YILDIZ
Keyword(s):  
Differential Scanning Calorimetry ◽  
Aluminum Alloy ◽  
Activation Energies ◽  
Isothermal Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Recrystallization Kinetics ◽  
Model Free ◽  
Cold Rolled ◽  
Kinetics Of

In this study, the non-isothermal recrystallization kinetics of cold rolled AA3105 and AA5005 aluminum alloy sheets obtained from ASAŞ Aluminum located in Akyazı-Sakarya was studied by using differential scanning calorimetry (DSC). The non – isothermal kinetics was performed by using Kissenger, Boswell, Ozawa and Starink methods known as model – free methods. The recrystallization temperatures on DSC graphics at different heating rates (β) were deduced and the activation energies were calculated from the slopes from Y – 1/T diagrams. Y is ln(β/T2) for Kissenger, ln(β/T) for Boswell, ln(β) for Ozawa and ln(β/T1.92) for Starink. The results showed that the activation energies of recrystallization are in the range of 194 – 206 kJ/mol for cold rolled AA5005 sheet and in the range of 235 – 257 kJ/mol for cold rolled AA3105 sheet, according to four non-isothermal kinetics model.

Modified Carbon Cryogel-Ammonia Borane Nanocomposites for Hydrogen Storage

2007 ◽  
Vol 1042 ◽  
Author(s):  
Saghar Sepehri ◽  
Betzaida Batalla Garcia ◽  
Qifeng Zhang ◽  
Guozhong Cao
Keyword(s):  
Hydrogen Storage ◽  
Photoelectron Spectroscopy ◽  
Ammonia Borane ◽  
Scanning Calorimetry ◽  
Dehydrogenation Kinetics ◽  
Carbon Cryogel ◽  
Nitrogen Doped Carbon ◽  
Kinetics Of ◽  
Catalytic Effects

AbstractThis paper reports the synthesis and characterization of coherent Boron/Nitrogen –doped –carbon cryogels- ammonia borane nanocomposites for hydrogen storage. Resorcinol formaldehyde derived doped carbon cryogels (CC) were obtained via chemical modification.CC- ammonia-borane nanocomposites were made by incorporation of ammonia borane (AB), in CCs. Nitrogen sorption analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy, are used to investigate the structure and morphology of the modified CCs. Differential scanning calorimetry is used to study the dehydrogenation of coherent doped-CC-AB nanocomposites. Modified CCs show higher mesoporosity, and more homogeneous porous structure compared to undoped CCs. Also, dehydrogenation kinetics of nanocomposites is enhanced as compared to neat AB. Possible nanoscale and catalytic effects of nanocomposites in improved dehydrogenation kinetics are discussed.

Effects of Ion Implantation on Crystallization of Amorphous CoSi2

1992 ◽  
Vol 279 ◽  
Author(s):  
Q. Z. Hong ◽  
K. Barmak ◽  
S. Q. Hong ◽  
L. A. Clevenger
Keyword(s):  
Kinetic Parameter ◽  
Ion Implantation ◽  
Crystallization Kinetic ◽  
Three Dimensional ◽  
Sharp Decrease ◽  
Liquid Nitrogen Temperature ◽  
Avrami Equation ◽  
Scanning Calorimetry ◽  
Reduced Rate ◽  
Kinetics Of

ABSTRACTThe effects of Si and Kr ion implantation on the crystallization kinetics of amorphous COSi2 have been investigated by differential scanning calorimetry and in situ sheet resistance measurement. Without ion implantation, the crystallization of coevaporated COSi2 is characterized by three dimensional growth from preexisting nuclei. When the as-deposited COSi2 is implanted with Si or Kr ions at liquid nitrogen temperature, the kinetics of the subsequent crystallization is significantly altered. A 180 keV 5×1015 cm−2Si ion implantation increases the crystallization temperature by 34°C. When the Si dose is below 1×1015 cm−2, ion implantation causes a sharp decrease in the crystallization kinetic parameter defined by the Avrami equation. The amount of decrease is shown to scale with the deposited nuclear energy. At higher doses, the kinetic parameter continues to decrease with increasing dose but at a much reduced rate.

Isothermal DSC Study of the Curing Kinetics of an Epoxy/Silica Composite for Microelectronics

2017 ◽  
Vol 14 (2) ◽  
pp. 45-50 ◽  
Author(s):  
Lérys Granado ◽  
Stefan Kempa ◽  
Stefanie Bremmert ◽  
Laurence J. Gregoriades ◽  
Frank Brüning ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Kinetic Method ◽  
Base Material ◽  
Curing Kinetics ◽  
Circuit Board ◽  
Heat Of Reaction ◽  
Scanning Calorimetry ◽  
Kinetic Measurements ◽  
Model Free ◽  
Kinetics Of

Abstract Curing kinetics of an industrially important printed-circuit board (PCB) base material (epoxy–phenol/glass fillers) were studied by isothermal differential scanning calorimetry (DSC) measurements between 150 and 190°C, as relevant curing temperatures for the PCB industry. The extent of cure was calculated by integration of the exothermic peak and normalization by the total heat of reaction (obtained by nonisothermal DSC). Although the cross-linking was completed above 180°C, the kinetic profiles show two regimes: one fast and one slow. The kinetic parameters have been elucidated using an isoconversional model-free kinetic method, with the exact method of Friedman, to give to the PCB manufacturers a road map to predict curing behavior of base material. The linearity of Arrhenius plots was satisfactory. The apparent activation energy of curing reaction has been found to increase with the degree of conversion. The elucidation of the kinetic parameters allows us to propose an accurate and predictive description of the curing kinetics within the fast regimen of reaction (i.e., without vitrification). Finally, we discuss how these kinetic measurements and models can be completed and optimized.

Effect of lignin-containing cellulose nanofibrils on the curing kinetics of polymeric diphenylmethane diisocyanate (PMDI) resin

Holzforschung ◽  
2019 ◽  
Vol 73 (9) ◽  
pp. 879-887 ◽  
Author(s):  
Guomin Wu ◽  
Xinhao Feng ◽  
Can Jin ◽  
Zhenwu Kong ◽  
Siqun Wang
Keyword(s):  
Cellulose Nanofibrils ◽  
Curing Kinetics ◽  
Diphenylmethane Diisocyanate ◽  
Scanning Calorimetry ◽  
Oh Groups ◽  
Curing Reaction ◽  
Model Free ◽  
Speed Up ◽  
Polymeric Diphenylmethane Diisocyanate ◽  
Kinetics Of

Abstract In order to increase the curing rate of polymeric diphenylmethane diisocyanate (PMDI) resin, different contents of lignin-containing cellulose nanofibrils (L-CNFs) were blended into the PMDI. Differential scanning calorimetry (DSC) was used to examine how the addition of L-CNFs influences the curing kinetics of PMDI resin. The activation energy (Ea) of the curing reaction of PMDI/L-CNF systems was calculated using the Kissinger, Friedman and Flynn-Wall-Ozawa model-free methods. The results showed that Ea values calculated by the aforementioned three methods varied in a similar trend with the increase in the L-CNF content. Adding L-CNFs could decrease the Ea value of the curing reaction of PMDI and speed up the curing reaction. The acceleration of the cure rate of the PMDI resin upon the addition of L-CNFs may be attributable to the effective dispersion of the L-CNFs into the PMDI resin as well as the reaction between the hydroxyl (-OH) groups of the L-CNFs and the isocyanate (-NCO) groups of the PMDI.

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