Pooya Hosseini Benhangi

Borohydride-tolerant oxygen electroreduction catalyst for mixed-reactant Swiss-roll direct borohydride fuel cells

A novel and highly active Fe–aminoantipyrine (Fe–AAPyr) catalyst for oxygen reduction reaction (ORR) in alkaline media was synthesized by the modified sacrificial support method (SSM) and investigated in an innovative Swiss-roll mixed-reactant alkaline fuel cell architecture. The prepared Fe–AAPyr cathode showed excellent shorter-term (up to 200 min) durability and tolerance to electrooxidation of NaBH4. The Swiss-roll mixed-reactant Direct Borohydride Fuel Cell (DBFC) equipped with a Pt 3D anode and Fe–AAPyr gas-diffusion cathode produced an open circuit voltage and peak power density of 0.97 V and 137 mW cm−2 respectively at 45 °C and ambient pressure. These values are among the highest open circuit voltages and peak power densities reported for any mixed-reactant low temperature fuel cell and conventional dual chamber DBFCs.

Controlled Forging of a Nb Containing Microalloyed Steel for Automotive Applications

Controlled forging of microalloyed steels is a viable economical process for the manufacture of automotive parts. Ferrite grain refinement and precipitation hardening are the major microstructural parameters to enhance the mechanical properties of the forged components. In the current study, a modified thermomechanical treatment for additional ferrite grain refinement is developed by exploiting the effect of Nb in increasing the TNR (no recrystallization temperature) and via phase transformation from a pancaked austenite. This is accomplished by performing the final passes of forging below the TNR temperature followed by a controlled cooling stage to produce a mixture of fine grained ferrite, small scaled acicular ferrite as well as a limited amount of martensite. The effect of processing parameters in terms of forging strain, cooling rate and aging condition on the microstructure and mechanical properties of a medium carbon, Nb containing microalloyed steel is investigated. An attempt is made to identify a suitable microstructure that provides a proper combination of high strength and good impact toughness. The processing-microstructure relationships for the proposed novel forging procedure are discussed, and directions for further improvements are outlined.

Thermomechanical Processing of a Nb-Microalloyed Steel in a Controlled-Forging Treatment

Ferrite grain size is one of the most important microstructural parameters in steels which can be appropriately adjusted to cause a significant strengthening effect. Thermomechanical processing is an effective method for ferrite grain refinement in microalloyed steels. Transformation of deformed austenite with a pancaked grain structure to a relatively fine ferrite phase is an important phenomenon occurring during the thermomechanical processing of microalloyed steels. The final microstructure of steels can be optimized by controlling three critical processing parameters, i.e. i) applied strain (constant strain rate), ii) deformation temperature, and iii) cooling rates following the hot deformation stage. In the present study, a new approach (called controlled-forging treatment) consisting of hot deformation of steel at the austenitic temperature range using an upset forging stage was developed for the ferrite grain refinement in a Nb-microalloyed steel. The investigated steel was subjected to a thermomechanical treatment including reheating, hot deformation for two different strain levels, namely 30 and 50% reductions of height, in a single pass hot-forging stage at temperatures below the TNR (no-recrystallization) and above the TR3 (austenite to ferrite transformation) temperatures followed by cooling to room temperature using three different cooling rates. The experimental results obtained from this proposed treatment were more or less similar to those already obtained for the case of controlled-rolling process on Nb-microalloyed steel sheets.