Papers by Author: M.F. Rodrigues

Abstract: The open photoacoustic cell technique (OPC) was carried out in order to measure the thermal diffusivity of hardmetal. Hardmetal is usually processed by the conventional powder technology techniques: mix of WC + Co powders, compacting, and liquid phase sintering A new method to process hardmetal parts is hereby described. Parts of WC-15%wt Co were processed by using high pressure – high temperature sintering. It was used the pressure of 5GPa, temperature of 1350 oC, and time of 2 minutes of sintering. In addition to the thermal diffusivity, heat capacity was considered and the thermal conductivity achieved. Results matched with the values of the literatures where others photoacoustic techniques have been employed. It was achieved a thermal capacity of 3.34J/cm3K, thermal diffusivity of 0.35cm2/s, and thermal conductivity of 116.9W/mK. It reveals that the HPHT processed WC- 15%wtCo hardmetal is able to work as a cutting tool, in the thermal point of view.

Abstract: In Campos oil Basin (Brazil), which is responsible for more than 80 % of the national petroleum production, it is generated a great amount of wastes from deep crude oil extraction related activities. Particularly, the oil sludge waste has been intensely studied in order to search alternatives for the reuse of the waste in treated form in the ceramic industry. the present work focuses on the photoacoustic thermal characterization of sintered ceramic bodies containing up to 5 wt.% added waste. Specimens were uniaxially pressed at 25 MPa, and sintered between 850 °C and 1000 °C. The results of thermal diffusivity indicate that the use of petroleum waste in structural ceramic up to 5 wt.% does not cause significant changes in the structure or composition of the clay/waste system, resulting in great advantages in waste minimization.

Abstract: Hardmetal is usually processed by the conventional powder technology techniques: mix of WC + Co powders compacted and liquid phase sintering. A new method to process hardmetal parts is hereby described. Parts of WC-15%wt Co were processed by using high pressure – high temperature sintering. It was used the pressure of 5GPa, temperatures of 780-1200-1350-1400oC, and times of 2-4 minutes of sintering. Results are shown as a function of micro-structural evolution, densification, and hardness measurements.