Nano-Meter Size WC Whiskers Grown over a Compacted Pellet of Graphite/Tungsten Powder Mixture Heated with an Ultra-Fast Heating Rate by a Concentrated Solar Beam

The effect of ultra-fast heating on the microstructures of steel has been thoroughly studied over the last year as it imposes a suitable alternative for the production of ultra high strength steel grades. Rapid reheating followed by quenching leads to fine-grained mixed microstructures. This way the desirable strength/ductility ratio can be achieved while the use of costly alloying elements is significantly reduced. The current work focuses on the effect of ultra-fast heating on commercial dual phase grades for use in the automotive industry. Here, a cold-rolled, low-carbon, medium-manganese steel was treated with a rapid heating rate of 780 °C/s to an intercritical peak temperature (760 °C), followed by subsequent quenching. For comparison, a conventionally heated sample was studied with a heating rate of 10 °C/s. The initial microstructure of both sets of samples consisted of ferrite, pearlite and martensite. It is found that the very short heating time impedes the dissolution of cementite and leads to an interface-controlled α → γ transformation. The undissolved cementite affects the grain size of the parent austenite grains and of the microstructural constituents after quenching. The final microstructure consists of ferrite and martensite in a 4/1 ratio, undissolved cementite and traces of austenite while the presence of bainite is possible. Finally, it is shown that the texture is not strongly affected during ultra-fast heating, and the recovery and recrystallization of ferrite are taking place simultaneously with the α → γ transformation.

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Evaluation of Hydrogen Yield Evolution in Gaseous Fraction and Biochar Structure Resulting from Walnut Shells Pyrolysis

Energies ◽

10.3390/en13236359 ◽

2020 ◽

Vol 13 (23) ◽

pp. 6359

Author(s):

Elena David

Keyword(s):

Heating Rate ◽

Pyrolysis Temperature ◽

Walnut Shell ◽

Hydrogen Yield ◽

X Ray Diffraction ◽

Fast Heating ◽

X Ray ◽

Walnut Shells ◽

Water Vapors ◽

Gaseous Fraction

Conversion experiments of wet and dry walnut shells were performed, the influence of moisture content on the hydrogen yield in the gas fraction was estimated and the resulted biochar structure was presented. Measurements of the biochar structures were performed using X-ray diffraction and scanning electron microscopy methods. The results demonstrate that heating rate played a key role in the pyrolysis process and influenced the biochar structure. Under fast heating rate, the interactions between the water vapors released and other intermediate products, such as biochar was enhanced and consequently more hydrogen was generated. It could also be observed that both biochar samples, obtained from wet and dry walnut shells, had an approximately smooth surface and are different from the rough surface of the raw walnut shell, but there are not obvious differences in shape and pores structure between the two biochar samples. The increasing of the biochar surface area versus pyrolysis temperature is due tothe formation of micropores in structure. The biochar shows a surface morphology in the form of particles with rough, compact and porous structure. In addition the biochar structure confirmed that directly pyrolysis of wet walnut shells without predried treatment has enhanced the hydrogen content in the gas fraction.

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Effect of Heating Rate on the Phases Formation in Ti-20 wt. % Al Powder Mixture

MANUFACTURING TECHNOLOGY ◽

10.21062/ujep/258.2019/a/1213-2489/mt/19/1/139 ◽

2019 ◽

Vol 19 (1) ◽

pp. 139-143

Author(s):

Andrea Školáková ◽

Pavel Salvetr ◽

Pavel Novák

Keyword(s):

Heating Rate ◽

Powder Mixture ◽

Al Powder

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The effect of heating factors on the properties of heat-induced surimi gel under ohmic heating

Can Tho University Journal of Science ◽

10.22144/ctu.jen.2021.028 ◽

2021 ◽

Vol 13 (2) ◽

pp. 32-42

Author(s):

Van Nguyen

Keyword(s):

Electrical Conductivity ◽

Heating Rate ◽

Salt Concentration ◽

Ohmic Heating ◽

Heating Time ◽

Holding Time ◽

Water Bath ◽

Heating Rates ◽

Fast Heating ◽

Water Bath Heating

Ohmic heating (OH) is a method that heat is generated within the food due to its electrical resistance, resulting in a relatively linear heating rate and uniform temperature distribution. Because surimi-based paste contains water and salts, the conductivity is sufficiently good for the ohmic effect. Gelation induced by OH greatly depends on heating conditions such as heating speed, heating time, or electrical conductivity. However, the detailed information obtained is quite limited. Therefore, in order to clarify how ohmic heating affects the physical properties of surimi gel under OH, gels from croaker surimi (SA grade) were obtained using different heating conditions (heating speed, heating time, or salt concentration - electrical conductivity). Furthermore, the gels heated by ohmic heating were compared with the gel obtained by conventional water-bath heating. The results showed that, at the same heating rates, higher salt concentration generated better surimi gels for croaker surimi. Gels cooked ohmically at a slow heating rate performed significantly better than those cooked at a fast heating rate or heated conventionally in a water bath. There was little discernible difference in protein pattern between gels heated by OH and conventional water bath heating at fast heating rates with two different salt concentrations. The results also indicated that holding time at target temperature showed no effect on the gel. These results suggested that the properties of heat-induced surimi gels by OH are affected by not only heating speed but also holding time at maximum temperature and salt content.

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