Oxygen Transfer Reactions during Sintering of Ferrous Powder Compacts

Powder metallurgy products may be started from powders with widely varying oxygen affinity. Thus the natural oxygen content of the powder compacts also varies in reducibility in the early stages of sintering. Here it is shown that prealloyed powders containing Cr require higher temperatures for oxygen removal than e.g. unalloyed or Ni-Cu alloyed grades. In case of powder mixes of base iron powder with Cr, Mn or Si, oxygen transfer from Fe to the additive powders may occur during heating up to sintering temperature, the “internal getter effect”. A similar effect can be observed in Cr prealloyed powders in which iron oxides initially present on the powder surfaces are transformed to more stable oxides in a fairly early stage of heating. Finally, also the formation of CH4observed when sintering alloy steels containing Si, Mn or Cr in H2can be attributed to an oxygen transfer effect.

Dielectric properties of ternary composites of triblock polymer surfactant, liquid crystal and organic solvent

Dielectric spectroscopy, at room temperature (20°C), is used to study the dielectric response of ternary mixtures of commercial nematic liquid crystal mixtures E7 and E33, an organic solvent N-Methyl-2-Pyrrolidone (NMP) and a triblock polymers in the frequency range from 0.01 Hz to 1 MHz. The results indicate a dielectric relaxation in the hectohertz region. Individually, both E7 and NMP have rather large low frequency conductivities; however, the low frequency (0.01–10 Hz) behavior of the mixtures has no such behavior. We attribute this behavior to an ion getter effect of the triblock polymer surfactant. Optimized ternary mixtures obtain a real dielectric constant near 230, and loss tangent less than 0.05 at frequencies near 10 mHz.

Thermal Properties of Vacuum Insulation Panels with Glass Fiber

The VIPs consist of the glass-fiber core material and two types of envelope film. The glass fiber was fabricated by a centrifugal blowing process. The core material was prepared by the wet method. The thermal conductivities of the core material and VIPs were measured by the heat flow meter. The thermal conductivity for six pieces of 1mm thick core material is less than that for one piece of 6mm thick core material, which is affected by the fiber diameter, porosity ratio and the largest pore size diameter. The VIP for the building material has a low thermal conductivity (<0.008W/mK). The VIP for the home appliance has a lower thermal conductivity (<0.003W/mK). The VIP maintains a high-uniform thermal conductivity values due to the getter effect.

Titanium Surface Hardening by Pulsed Nitrogen Ion Implantation

ABSTRACTLayers of TiN have been developed on pure titanium samples using pulsed ion beams generated with a Plasma Gun operated in the detonation mode.XPS analyses show TiNx formation in depths >0.6μm, with stoichiometric x>0.8. The efficient TiN formation in this process can be attributed to the fast energy released by the pulsed beams, which can increase the surface layer temperatures at a ∼15K/ns rate, generating thermal gradients of ∼1500K/μm. This thermal effect can help the titanium getter effect on the nitrogen plasma bubble.