A novel nitrile butadiene rubber (NBR)/ magnetite (Fe 3 O 4 ) nanocomposite for electromagnetic interference (EMI) shielding at microwave frequency was successfully fabricated. The structural features of assynthesized magnetite and NBR/Fe 3 O 4 were examined by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and energydispersive X-ray spectroscopy. The number of elastically effective chains, volume fraction of rubber, interparticle distance among conductive sites, polymer-filler interaction, and porosity of the nanocomposites were evaluated. The mechanical properties, including the tensile strength, elongation at break, and hardness, of the composites were measured. The static electrical properties, such as the elec-trical conductivity, carrier mobility, and number of charge carriers, as a function of magnetite content were evaluated. The interrelation between the electrical conductivity, shielding effectiveness (SE), dielectric constant, and skin depth of the composites are discussed. Finally, the EMI SE versus frequency was tested. The results reveal that an SE of 28-91 dB against EMI in the 1-12 GHz range depended on the loading of the conducting magnetite within the NBR matrix. Accordingly, these nanocomposites may used in the field of microwave absorption devices.

A new negative temperature coefficient of resistor (NTCR) thermistors based on nitrile butadiene rubber/magnetite (NBR/Fe 3 O 4 ) nanocomposites were successfully fabricated by conventional roll milling technique. X-ray diffraction and transmission (TEM) analysis showed that the product is mainly magnetite nanoparticles with diameter of 10-13 nm. The microstructure of (NBR/Fe 3 O 4 ) nanocomposites were examined by scanning electron microscopy (SEM) and FTIR spectroscopy. The dispersion of magnetite nanoparticles in the NBR rubber matrix and interfacial bonding between them were rather good. The thermal stability of nanocomposites was also obviously improved with the inclusion of the magnetite nanoparticles. The thermal conductivity, thermal diffusivity and specific heat of nanocomposites were investigated. The electrical conductivity of the NBR/Fe 3 O 4 increases with the rise in temperature exhibiting a typical negative temperature coefficient of resistance (NTCR) behavior like a semiconductor. The nature of the temperature variation of electrical conductivity and values of activation and hopping energy, suggest that the transport conduction process is controlled by hopping mechanism. Values of characteristics parameters of the thermistors like thermistor constant, thermistor sensitivity and thermistor stability is quite good for practical application as NTCR devices at high temperature.

Transient creep tests are performed under constant stress conditions at temperatures ranging from 373 to 453 K for Sn‐0.5 wt% Zn, Sn‐9 wt% Zn, and Pb‐10 wt% Sn, and from 363 to 433 K for Pb‐61.9 wt% Sn samples. The transient creep is described by ϵtr = Btn, where ϵtr and t are the transient creep strain and time. The parameters B and n are calculated. The activation enthalpy of the transient creep shows for each alloy two regions at low and high temperatures. The values of activation enthalpies show that the mechanism controlling transient creep in Sn‐Zn alloys is a dislocation mechanism, while in Pb‐Sn alloys it consists of dislocation intersections and grain boundary diffusion.