Papers by Keyword: Cryogenic Properties

Abstract: Two different systems, the non-reactive Ag–diamond and the reactive Al–diamond system, were assessed by their thermal conductivity behaviour, both were fabricated by gas pressure assisted infiltration of densely packed diamond bulks with aluminium or silver and different Si-concentration and diamonds of varying particle sizes. The effect of Si-concentration on the interface thermal conductance h between Al, Ag and diamonds was investigated in dependence of temperature by measuring thermal conductivity of composites with different sized diamond particles in the temperature range from 4 K up to ambient. Composite thermal conductivities κ_c(T) can be as high as 860 W m^-1 K^-1 at roughly 100 K for Al/diamond and 1100 W m^-1 K^-1 for Ag–Si/diamond at approx. 150 K. Although the Si concentration in the matrix plays an eminent role for κ_c(T), i.e. the lower the Si concentration, the higher κ_c(T), interface thermal conductance is almost unaffected in the reactive Al-diamond system. Furthermore, they are close to values determined on clean model systems, i.e. sputtered and evaporated metal layers on diamond monocrystals. For Ag–diamond composites, the matrix composition of Ag–1Si seems to reflect an optimal composition, as the highest thermal conductivity κ_c(T) and an extraordinary higher interface conductance was achieved compared to Ag–3Si/diamond composites.

Abstract: From microstructure and technical performance of different fibers, the variation and influence of the different fibers’ properties and parameters on cryogenic properties of matrix asphalt and asphalt mixture were researched and evaluated through BBR and cryogenic trabecular bending tests. Research shows that: the addition of fibers makes the matrix asphalt’s low temperature creep stiffness S increases, creep slope m decreases, namely the matrix asphalt cryogenic flexibility and stress relaxation ability are weakened; cryogenic anti-cracking ability of asphalt mixture is significantly improved through adding different fibers, the order of improving effectiveness: Dolanit AS fiber> ARBOCEL lignin fiber> Basalt fiber; while asphalt content is constant, with the increase of fiber content, the mixture maximum bending strain, strength, deformation of mixture firstly increase and then decrease, the optimal asphalt content of asphalt mixtures and optimal fiber content of three fibers are identified according to the above three indicators’ maximum. Research points out the existed problems that are scope of application and evaluation indicators in BBR test of SHARP, optimal asphalt and fiber content are fully recommended, it provides scientific guidance and practical foundation for actual project.