Papers by Author: J.N.F. Holanda

Abstract: In this work the possibility of production of cemented carbide doped with rare-earth element (Y₂O₃) under condition of high pressure and high temperature (HPHT) was investigated. Initially, the cemented carbide powder (WC10wt.%Co) was submitted to conventional pressing at 800 MPa. The compacts were then sintered at 1400 °C for 40 s under a pressure of 5.5 GPa. The cemented carbide pieces were characterized in terms of relative density, coercive force, mechanical strength, microhardness, and wear resistance. The phase analysis was done by X-ray diffraction. It was established promising results on the production of cemented carbide under high pressure. Moreover, the addition of up to 1.5 wt.% of yttrium oxide in relation the cobalt phase enhanced the technical properties of the cemented carbide.

Abstract: The petroleum industry generates huge amounts of oily sludge during the process of oil and gas extraction. This waste is a pollutant material that can cause environmental damage. Because of this, it has been treated with bentonite clay, being referred as encapsulated petroleum waste. In this work the chemical-environmental characterization and classification of the petroleum waste were done according to ABNT standards. The results indicated that the encapsulated petroleum waste should be classified as Class IIA – “No Inert”. Therefore, it could be used in manufacture of ceramic products for civil construction.

Abstract: The objective of this work is to characterization of sugarcane bagasse ash waste aiming the use it in red ceramic industry. The characterization was done in terms of chemical composition, X-ray diffraction, particle size distribution, morphology, and plasticity. The results show that the cane bagasse ash waste is a non plastic material, which contains high content of silica and minor amounts of Al, Fe, Ca, Mg, and K oxides. Thus, the sugar cane bagasse ash waste presents high potential for application in the manufacture of ceramic products such as bricks, roofing tiles, and ceramic tiles.

Abstract: Aluminous electrical porcelains are used in the production of materials of high voltage insulators. The microstructure plays an important role in the performance of electrical porcelain. On the other hand, the porcelain materials undergo a series of physical and chemical transformations during firing. This makes the understanding of their microstructures rather complex. In this work was studied the microstructural development of electrical porcelain containing up to 35 wt.% of ornamental rock waste. The pieces ceramics were pressed at 50 MPa and sintered at 1300 °C. The porcelain pieces were characterized via X-ray diffraction and scanning electron microscopy. The results indicate that the presence of the ornamental rock waste influenced the microstructural development of the pieces of electrical aluminous porcelain.

Abstract: In this work is done a study on the sintered microstructure of ceramic tile paste incorporated with petroleum waste. The raw materials used were kaolin, sodic feldspar, quartz and petroleum waste. The ceramic tiles containing up to 5 wt% petroleum waste were prepared by uniaxial pressing and sintered at 1200°C. The microstructural evolution was examined by SEM. In addition, water absorption, linear shrinkage, and sintered density were determined. The results showed that the microstructure of the ceramic tiles is influenced by the added petroleum waste.

Abstract: The ornamental rock industry generates huge amounts of waste in form of fine powder, demanding adequate alternatives for its final disposal. The possibility of using ornamental rock waste as a flux in porcelain tile has been assessed. The porcelain tile formulations are constituted mainly by kaolin, feldspar and quartz. The waste was added to a typical porcelain tile body, replacing the sodic feldspar by up to 15 wt. %. The prepared pastes were fired of 1240°C using a fast-firing cycle. The specifications of porcelain floor tile in terms of physical properties were achieved.

Abstract: This work presents the results of a study concerning the influence of the addition of rareearth elements (La2O3 and CeO2) on the sintering of the WC/10Co cemented carbide. Several WC/10Co mixtures containing up to 3 wt.% rare-earth of the cobalt phase were prepared. Specimens were uniaxially pressed at 200 MPa, and sintered in a vacuum furnace at 1400 °C during 60 minutes. The sintering behaviour was accompanied by the linear shrinkage, density, and mechanical strength. The development of the microstructure was followed by XRD and SEM. The results showed that the sintering behaviour of the WC/10Co cemented carbide was influenced by adding of rare-earth element. In addition, the lanthanium oxide addition was more effective on the improvement of the physical-mechanical properties of the studied carbide.

Abstract: The industry of ornamental stones processing from Espírito Santo State produces high amounts of powder waste from sawing and polishing of granite. This waste is a non-biodegradable material that when disposed generates pollution and environmental damage. Clay/waste mixtures were prepared with a kaolinitic clay and waste additions up to 10 wt.%. Various bodies were prepared by uniaxial pressing and sintered in air between 850°C and 1150°C. Emphasis is given on the drying and firing properties. The results revealed that the ceramic bodies containing granite powder waste are adequate for manufacture of structural ceramic. In addition, the employed methodology is environmentally correct and can contribute to the sustainable development.

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.