scholarly journals Pulsed direct current field-induced thermal stability and phase transformation of nanodiamonds to carbon onions

RSC Advances ◽  
2019 ◽  
Vol 9 (25) ◽  
pp. 14360-14371 ◽  
Author(s):  
Faming Zhang ◽  
Kuowei Fan ◽  
Jin Yu ◽  
Farhad Saba ◽  
Jing Sun

The pulsed DC field-induced thermal stability of nanodiamonds (NDs) and their transformation to carbon onions lack detailed understanding.

2019 ◽  
Vol 35 (5) ◽  
pp. 727-732
Author(s):  
Minjie Xu ◽  
Chao Hu ◽  
Haiyan Xiang ◽  
Haozi Lu ◽  
Travis Shihao Hu ◽  
...  

2017 ◽  
Vol 36 (3) ◽  
pp. 822-828
Author(s):  
SG Bawa ◽  
AS Ahmed ◽  
PC Okonkwo

Thermal stability of transitional alumina phases produced from ammonium alum using Kankara kaolin as starting material was studied. Wet beneficiation method was employed to purify the starting material, after which it was calcined and dealuminated with sulphuric acid. The elemental composition, mineralogical, and physiological analyses were carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) techniques respectively. The ammonium alum was thermally treated by varying the calcination temperature from 700 to 1200°C and varying the time of calcination from 1 to 4 h. The formation of gamma alumina began at calcination temperature of 825°C for calcination time of 3 h, which was found to be lower than reported works of 900°C. It was found to be stable at higher temperature of 1125°C, above which phase transformation to alpha alumina was observed. The observed wide range of thermal stability of the gamma alumina phase gives it good advantage to be used for high temperature applications, such as support for catalyst promoters. Alpha alumina phase formation began at 1150°C and was fully formed at 1200°C. BET specific surface area of 166 m2/g was obtained for the gamma alumina phase which was high enough for it application as support for catalyst, catalyst and adsorbent. http://dx.doi.org/10.4314/njt.v36i3.23


2014 ◽  
Vol 1073-1076 ◽  
pp. 66-72
Author(s):  
Wei Zhai ◽  
Guang Ming Liu ◽  
Fei Yu ◽  
Yuan Kui Wang

In this paper, additive A and additive B were added into Hitec molten salts in order to optimize the properties of the molten salt. The melting point, latent heat of phase transformation, specific heat capacity, thermal gravity, and thermal stability of the modified Hitec molten salt was characterized. The results showed that compare to Hitec molten salt the modified Hitec molten salt showed low melting point, proper latent heat of phase transformation, greater heat of fusion, wide using temperature range and other advantages. The modified molten salt had good thermal properties and thermal stability. This modified Hitec molten salt has good application prospect in the aspect of high temperature heat storage/transfer.


2007 ◽  
Vol 124-126 ◽  
pp. 45-48
Author(s):  
J.W. Lee ◽  
Cheol Woong Yang

We investigated the phase transformation and thermal stability of Ni silicides formed in Ni/Si and Ni0.95Ta0.05/Si systems. The sheet resistance values of the silicide in the Ni0.95Ta0.05/Si system were lower than those in Ni/Si system at any temperature. The enhancement of thermal stability is closely related to the phase transformation occurred during post heat-treatment. Microstructure of the phases formed by reaction was investigated by analytical electron microscopy (AEM) and the phase identification of Ni silicide was carried out using convergent beam electron diffraction (CBED) technique. It was found that a Ta rich layer formed on the top of the Ni silicide layer and small amount of Ta dissolved into the silicide layer. By addition of Ta atoms, phase transformation from NiSi to NiSi2 is retarded and thermal stability of Ni silicide is improved.


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