Mechanistic and processing studies in combustion synthesis of niobium aluminides

1995 ◽  
Vol 10 (9) ◽  
pp. 2260-2270 ◽  
Author(s):  
C.R. Kachelmyer ◽  
A.S. Rogachev ◽  
A. Varma
Keyword(s):  
Melting Point ◽  
Combustion Synthesis ◽  
Heating Rate ◽  
Ignition Temperature ◽  
Product Formation ◽  
Green Density ◽  
Combustion Mode ◽  
Heating Rates ◽  
Niobium Aluminide ◽  
Niobium Aluminides

Combustion synthesis of NbAl3 and Nb2Al was studied using the volume combustion mode. The effects of heating rate and green density were examined for NbAl3 synthesis. The effect of green density was also investigated for Nb2Al. Greater reaction completion was achieved at higher heating rates and green densities. In both NbAl3 and Nb2Al samples, the reaction was initiated above the melting point of Al. Quenching (Nb+3Al) samples pressed at relatively high and low densities below the ignition temperature, and results of a particle-foil experiment, identified the spreading characteristic of molten Al over Nb, providing mechanistic details about niobium aluminide product formation.

Reaction kinetics in the combustion synthesis of Al–Ir–Ni intermetallic compounds

2008 ◽  
Vol 23 (7) ◽  
pp. 1953-1960
Author(s):  
Kai Cai ◽  
Machiko Ode ◽  
Hideyuki Murakami
Keyword(s):  
Differential Scanning Calorimetry ◽  
Combustion Synthesis ◽  
Heating Rate ◽  
Ignition Temperature ◽  
Effective Control ◽  
Vacuum Furnace ◽  
Heating Rates ◽  
Product Density ◽  
Scanning Calorimetry ◽  
Reactant Powder

The combustion synthesis of Al50Ir48Ni2 (at.%) was conducted at different heating rates in both a differential scanning calorimetry (DSC) chamber and a vacuum furnace. It was found that a higher heating rate, a sufficient amount of reactant powder, and effective control of the heat loss facilitated the complete reaction and resulted in combusted single IrAl phase products. Otherwise, multiphase products containing IrAl, unreacted Ir, and Al3Ir were synthesized. The reactions involved in different processes were discussed in terms of the thermal competition between heat generation and loss during the reaction. All ignition temperatures were below 773 K, indicating that the combustion reaction occurs at the solid–solid state. With increasing heating rate, the ignition temperature increased while the product density decreased.

Combustion Synthesis of Niobium Aluminide Matrix Composites

1994 ◽  
Vol 350 ◽  
Author(s):  
C. R. Kachelmyer ◽  
A. Varma
Keyword(s):  
Melting Point ◽  
Combustion Synthesis ◽  
Thermal Explosion ◽  
Matrix Composites ◽  
Product Density ◽  
B Additions ◽  
Reaction Completion ◽  
Niobium Aluminide

AbstractCombustion synthesis of NbAl3-matrix composites with Al2O3 and B additions was studied using the thermal explosion mode. The addition of B to the reaction mixture resulted in the formation of NbB2, small amounts of NbB and unreacted Al. The Al2O3 addition did not affect the NbAl3-matrix reaction completion but the final product density increased with increasing Al2O3 loading. In both NbAl3-matrix composites, the reaction was initiated above the melting point of Al.

A crystallographic and thermal study of pridinol mesylate and its monohydrated solvate

2018 ◽  
Vol 74 (3) ◽  
pp. 304-310 ◽  
Author(s):  
Pablo Gaztañaga ◽  
Ricardo Baggio ◽  
Daniel Roberto Vega
Keyword(s):  
Hydrogen Bonding ◽  
Melting Point ◽  
Heating Rate ◽  
Thermal Study ◽  
Molecular Structures ◽  
Heating Rates ◽  
Structural Collapse ◽  
Bond Angles ◽  
Crystal And Molecular Structures ◽  
Solvate Form

Herein are reported the crystal and molecular structures of the pridinol mesylate salt (C20H25NO+·CH3O3S−) (I) and its monohydrated solvate form (C20H25NO+·CH3O3S−·H2O) (II). A comparison of both with the already reported structure of pure pridinol [1,1-diphenyl-3-piperidino-1-propanol, C20H25NO; Tacke et al. (1980). Chem. Ber. 113, 1962–1980] is made. Molecular structures (I) and (II) are alike in bond distances and bond angles, but differ in their spatial conformation, and, more relevant still, in their hydrogen-bonding motifs. This gives rise to quite different packing schemes, in the form of simple dimers in (I) but water-mediated hydrogen-bonded chains in (II). The dehydration behaviour of form (II) is highly dependent on the heating rate, with slow rates leading to a clear endothermic dehydration step, towards anhydrous (I), with subsequent melting of this latter phase. Increased heating rates result in a more unclear behaviour ending in a structural collapse (melting of the hydrated phase), at temperatures significantly lower than the melting point of the anhydrous phase. The eventual relevance of the water link in the structure of (II) is discussed in regard to this behaviour.

scholarly journals Analysis of DSC (differential scanning calorimetry) thermograms of milk fat

2021 ◽  
Vol 5 (3(61)) ◽  
pp. 36-39
Author(s):  
Maltam Shamilova ◽  
Sevinj Hajiyeva
Keyword(s):  
Fatty Acids ◽  
Differential Scanning Calorimetry ◽  
Melting Point ◽  
Heat Flow ◽  
Heating Rate ◽  
Milk Fat ◽  
Oxidation Time ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Melting Properties

The object of current research is the oxidation and melting properties of milk fat samples in different heating rates. One of the most problematic issues is the evaluation dependence of temperature and oxidation time regarding to heat flow, and the estimation of attitude of enthalpy values to heating rates. In order to gain a comprehensive assessment of oxidation and melting properties of milk fat samples on differential scanning calorimeter in various heating rates, it is necessary to conduct experimental studies. The analysis was performed using the dynamic option of the differential scanning calorimetry (DSC) with the following sample heating rates: 2.5, 4, 5, 7.5, 10, 12.5, 15 °C⋅min–1. Analyses were performed on 14 samples of milk fat, thus, for each heating rate were intended to two milk fat samples. As a result of the analysis, in the proper heating rates increased, it was found, that the oxidation properties of milk fat depend on the heating rates on DSC examination. In the thermal DSC analysis, the start temperature (Ts) (inlet), the onset temperature (Ton), and the maximum heat flow-peak temperatures (Tp) of oxidation were rising gradually. All the value of oxidation increased gradually with increasing heating rate, only in the Tend values were chainable among all heating rates. However, the oxidation time of milk fat is inversely proportional to the various heating rates in DSC. The oxidation enthalpy was calculated according to the heating rates too. The masses of the samples differ from each other, albeit slightly, which the individuality in the value of enthalpy could be explained through this ratio and duration of exothermic. The melting point considers the important indicator to explain the purity of samples. Melting curves of extracted milk fat samples on DSC were characterized by endothermic behavior and observed with the mild peaks, the first and the second distinct peaks due to the low-melting triacylglycerols (with high unsaturated fatty acids content) and high-melting fats, which present in milk fat. In concluded results, the characteristics of DSC oxidation curves are melting point due to the chemical structure of the fatty acids which milk fat samples contain.

Influence of heating rate and degree of oxidation on the ignition temperature

2018 ◽  
Vol 4 ◽  
pp. 25-35
Author(s):  
D.V. Miroshnichenko ◽  
V.Yu. Kramarenko ◽  
I.V. Shulga ◽  
Yu.S. Kaftan ◽  
N.A Desna ◽  
...  
Keyword(s):  
Heating Rate ◽  
Ignition Temperature ◽  
Degree Of Oxidation

Maximum heating rates for producing undistorted glassy carbon ware determined by wedge-shaped samples

1996 ◽  
Vol 11 (9) ◽  
pp. 2368-2375 ◽  
Author(s):  
Hossein Maleki ◽  
Lawrence R. Holland ◽  
Gwyn M. Jenkins ◽  
R. L. Zimmerman ◽  
Wally Porter
Keyword(s):  
Heating Rate ◽  
Treatment Process ◽  
Gaseous Product ◽  
Pyrolysis Mass Spectrometry ◽  
Heating Rates ◽  
Gaseous Products ◽  
Volatile Products ◽  
Solid Bodies ◽  
Polymeric Carbon ◽  
Maximum Heating

Polymeric carbon artifacts are particularly difficult to make in thick section. Heating rate, temperature, and sample thickness determine the outcome of carbonization of resin leading to a glassy polymeric carbon ware. Using wedge-shaped samples, we found the maximum thickness for various heating rates during gelling (300 K–360 K), curing (360 K–400 K), postcuring (400 K–500 K), and precarbonization (500 K–875 K). Excessive heating rate causes failure. In postcuring the critical heating rate varies inversely as the fifth power of thickness; in precarbonization this varies inversely as the third power of thickness. From thermogravimetric evidence we attribute such failure to low rates of diffusion of gaseous products of reactions occurring within the solid during pyrolysis. Mass spectrometry shows the main gaseous product is water vapor; some carboniferous gases are also evolved during precarbonization. We discuss a diffusion model applicable to any heat-treatment process in which volatile products are removed from solid bodies.

scholarly journals Towards a better representation of the solar cycle in general circulation models

2007 ◽  
Vol 7 (20) ◽  
pp. 5391-5400 ◽  
Author(s):  
K. M. Nissen ◽  
K. Matthes ◽  
U. Langematz ◽  
B. Mayer
Keyword(s):  
Solar Cycle ◽  
Heating Rate ◽  
General Circulation ◽  
Temperature Response ◽  
General Circulation Models ◽  
Short Wave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Heating Rates ◽  
Radiation Scheme

Abstract. We introduce the improved Freie Universität Berlin (FUB) high-resolution radiation scheme FUBRad and compare it to the 4-band standard ECHAM5 SW radiation scheme of Fouquart and Bonnel (FB). Both schemes are validated against the detailed radiative transfer model libRadtran. FUBRad produces realistic heating rate variations during the solar cycle. The SW heating rate response with the FB scheme is about 20 times smaller than with FUBRad and cannot produce the observed temperature signal. A reduction of the spectral resolution to 6 bands for solar irradiance and ozone absorption cross sections leads to a degradation (reduction) of the solar SW heating rate signal by about 20%. The simulated temperature response agrees qualitatively well with observations in the summer upper stratosphere and mesosphere where irradiance variations dominate the signal. Comparison of the total short-wave heating rates under solar minimum conditions shows good agreement between FUBRad, FB and libRadtran up to the middle mesosphere (60–70 km) indicating that both parameterizations are well suited for climate integrations that do not take solar variability into account. The FUBRad scheme has been implemented as a sub-submodel of the Modular Earth Submodel System (MESSy).

INVESTIGATION OF THERMAL DEGRADATION OF POULTRY PROCESSING DEWATERED SLUDGE USING THERMOGRAVIMETRIC ANALYSIS METHOD

2015 ◽  
Vol 76 (5) ◽  
Author(s):  
N. Aniza ◽  
S. Hassan ◽  
M. F. M. Nor ◽  
K. E. Kee ◽  
Aklilu T.
Keyword(s):  
Particle Size ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Heating Rate ◽  
Degradation Process ◽  
Heating Rates ◽  
Initial Stage ◽  
Poultry Processing ◽  
Effect Of Particle Size ◽  
Dewatered Sludge

Thermal degradation of Poultry Processing Dewatered Sludge (PPDS) was studied using thermogravimetric analysis (TGA) method. The effect of particle size on PPDS samples and operational condition such as heating rates were investigated. The non-isothermal TGA was run under a constant flow of oxygen at a rate of 30 mL/min with temperature ranging from 30ºC to 800ºC. Four sample particle sizes ranging between 0.425 mm to 2 mm, and heating rate between 5 K/min to 20 K/min were used in this study. The TGA results showed that particle size does not have any significant effect on the thermogravimetry (TG) curves at the initial stage, but the TG curves started to separate explicitly at the second stage. Particle size may affect the reactivity of sample and combustion performance due to the heat transfer and temperature gradient. The TG and peak of derivative thermogravimetry (DTG) curves tend to alter at high temperature when heating rate is increased most likely due to the limitation of mass transfer and the delay of degradation process. 

scholarly journals Effect of heating rates on the microstructure and gas permeation properties of carbon membranes

2018 ◽  
Vol 14 (3) ◽  
pp. 378-381
Author(s):  
Norazlianie Sazali ◽  
Wan Norharyati Wan Salleh ◽  
Ahmad Fauzi Ismail ◽  
Kumaran Kadirgama ◽  
Mohamad Shahrizan Moslan ◽  
...  
Keyword(s):  
Heating Rate ◽  
High Performance ◽  
Room Temperature ◽  
Gas Permeation ◽  
Carbon Membrane ◽  
Heating Rates ◽  
Polymer Blending ◽  
Carbon Membranes ◽  
Permeation Properties ◽  
Fine Turning

High performance tubular carbon membrane (TCM’s) for CO2 separation were prepared by controlling the carbonization heating rates in range of 1-7 oC/min carbonized at 800 oC under Argon environment. A single permeation apparatus was used to determine the gas permeation properties of the membrane at room temperature. Fine turning of the carbonization condition was necessary to obtain the desired permeation properties. The preparation of PI/NCC-based TCM at low heating rate caused the gas permeance for the examined gas N2 and CO2 decreased whereas the selectivity of CO2/N2 increased. It was also identified that the gas permeation properties of the resultant TCM and its structure was highly affected by the heating rate. The best carbonization heating rate was found at 3oC/min for the fabrication of TCM derived via polymer blending of PI/NCC for CO2/N2 separation.

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