An analytical densification model describing the final stages of hot pressing and sintering has been developed and found to be consistent with empirical findings. The behaviour of composite powders for the matrices of diamond tools has been studied under hot pressing conditions. Differential scanning calorimetry was used to determine the heat capacity at constant pressure C p of pure Co, 663Cu, and composite iron-and cobalt based powders (also containing WC, Ni and 663Cu). The relationship between C p and composite densification has been analysed, and it has been found that optimised rare earth additions to the iron based composite powders can produce C p characteristics close or equivalent to that of pure Co powders. This modified composite powder has been used to hot press diamond drill and saw bits that show good properties. Employing a densification regime guided by the dynamic model has been found radically to improve stability in service (bend strength, hardness, impact, ductility and porosity).
In this paper layered and gradient structures of Ni-Al SHS system were adopted to manufacture Ni-Al/diamond composites. The effect of the layered and the diamond mesh gradient structures of Ni-Al/diamond on the SHS process and the microstructure of the composites were investigated. It is found that with the increasing of the number of layers, the combustion wave velocity is decreased. The combustion wave velocity for diamond mesh size gradient structure of Ni-Al SHS is faster than that for the layered structure. A well bonding can be formed between diamond and the matrix in layered and gradient structure Ni-Al/diamond composites due to the melt of Ni-Cr brazing alloy.
Herein,
by screening 89 porous materials (metal–organic
frameworks and covalent organic frameworks), the ultradeep desulfurization
from model gasolines was investigated by the facile adsorptive approach
by grand canonical Monte Carlo simulations. The accessible surface
area and void fraction ratio of porous materials are of great significance
for the ultradeep desulfurization of gasoline. ZnBDC, MOF-70, MOF-69C,
UIO-66, Cd3BTB2, ZIF-77, ZIF-69, and ZIF-2 are identified with ultrahigh
selectivity for thiophene/n-octane systems at 298
K and 10 kPa. The relationship between the loading amount of thiophene
in materials and the difference of isosteric heat of thiophene and n-octane (or benzene) was confirmed. The pressure swing
adsorption and temperature swing adsorption are considered to mimic
the separation in industrial processes. Functionalization (impregnation)
is an efficient route to boost the selectivity of removal of sulfur-containing
compounds from gasoline. Adsorption and separation mechanisms for
thiophene from gasolines are determined by the composition and inner
structure of materials.
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