İbrahim Özsert

Processing of Al2O3/SiC ceramic cake preforms and their liquid al metal infiltration

Abstract In order to prepare ceramic preforms, chemical processes were used rather than using mixing of ceramic powders to obtain porous Al 2 O 3 /SiC ceramic foams. A slurry was prepared by mixing aluminium sulphate and ammonium sulphate in the water, and silicon carbide powder was added into the slurry so that a uniform mixture of Al 2 O 3 /SiC cake could be produced. The resulting product was (NH 4 ) 2 SO 4 ·Al 2 (SO 4 ) 3 ·24H 2 O plus silicon carbide particles (SiC p ) after dissolving chemicals in the water. This product was heated up in a ceramic crucible in the furnace. With the effect of heat it foamed and Al 2 O 3 /SiC cake was obtained. Resulting Al 2 O 3 grains were arranged in a 3D honeycomb structure and the SiC particles were surrounded by the alumina grains. Consequently, homogeneous powder mixing and porosity distribution were obtained within the cake. The morphology of the powder connections was networking with flake like particles. These alumina particles resulted in large amounts of porosity which was desired for ceramic preforms to allow liquid metal flow during infiltration. The resulting high porous ceramic cake (preform) was placed in a sealed die and liquid aluminium was infiltrated by Ar pressure. The infiltration was achieved successfully and microstructures of the composites were examined.

The Wear Behaviour of Dual Ceramic Particles (Al2O3/SiC) Reinforced Aluminium Matrix Composites

Al2O3/SiC powder mix was prepared by reacting of aqueous solution of aluminium sulphate, ammonium sulphate and water containing SiC particles at 1200°C. 10 wt% of this dual ceramic powder with different sized SiC particles was added to a liquid matrix alloy during mechanical stirring between solidus and liqudus under inert conditions. The wear behaviour of the dual ceramic reinforced aluminium matrix composites was investigated using pin-on-disc test at room temperature under dry conditions. It was found that dual and bimodal particle reinforcement decreased wear loss especially when SiC powder with larger grain size was used. Microstructural examination showed that as well as coarse SiC particle reinforcement, a fine alumina particle reinforcement phase was observed within the aluminium matrix (A332). The improvement in wear resistance of the dual ceramic reinforced aluminium matrix composites (AlMCs) could be attributed to the ability of the larger SiC particles to carry a greater portion of the applied load, as well as to the function of the larger SiC particles in protecting the smaller alumina particles from being gouged out during the wear process. Furthermore, the incorporation of dual and bimodal particles increased hardness of the composites with respect to the composite with fully small sized particles.

Application of Taguchi’s methods to investigate factors affecting emissions of a diesel engine running with tobacco oil seed methyl ester

Different kinds of vegetable oils and their methyl/ethyl esters have been tested in diesel engines. However, studies reporting the effects of tobacco seed oil and Tobacco Seed Oil Methyl Ester (TSOME) on emissions of diesel engines are limited. One of the most important issues is to investigate parameters that affect the yield of biodiesel and their interactions on emissions of a diesel engine. The Taguchi method is a useful tool for this purpose. Two different catalysts (KOH and NaOH), four different blends (B10, B20, B50 and B100) and four engine speeds were used during full-load tests. Optimal catalyst type, engine speed and TSOME blends on exhaust emissions were determined using Taguchis technique. The Taguchi design method revealed that choosing right catalyst and the blend rate are important two factors in view of minimisation of pollutant emissions.

Compressive Behavior of Al2O3—SiC Ceramic Composite Foams Fabricated by Decomposition of Aluminum Sulfate Aqueous Solution

In recent years, a new class of ceramic foams with porosity levels up to 95% has been produced by the chemical method with aeration of a suspension containing foaming agents. The method of foamed suspensions has originated from the chemical reactions of water-soluble salts. In this study, sintered cellular ceramic composites with varying degrees of reticulation are prepared using coarse and fine silicon carbide (SiC) powder. A new process has been developed in order to produce SiC particles containing alumina (Al2 O3) foam by chemical route. An aqueous solution of aluminum sulfate and ammonium sulfate plus SiC particles is fired to prepare ceramic foams up to 1200°C in a ceramic crucible. During heating, the viscous suspension is foamed, sulfate ions are volatilized, and an Al 2O3—SiC composite cake is obtained. The resulting Al2O3 are in networking morphology with flaky struts whereas SiC particles are encapsulated in the flaky alumina. These 3D connections of the struts are responsible for macropores and Al2O3 and SiC grains within the struts are responsible for micropores. Thus, a ceramic composite foam containing bimodal pore distribution is obtained. After sintering at 1550°C, compression tests are applied for the ceramic composite foams. High compressive strength is achieved after post sintering. Both sintering temperature and addition of SiC particles increase the compressive strength of the foam. Both SEM image and XRD analyses are carried out to examine composite microstructures and properties.

Effects of tobacco seed oil methyl ester on performance and exhaust emissions of diesel engine

Tobacco seed oil (TSO) was considered as a potential alternative fuel for compression ignition engines as the tobacco plant has high ecological tolerance and its farming can be realised on five different climatic regions in Turkey. In this study, the effects of TSO methyl ester (TSOME) on the performance and exhaust emissions of a single cylinder water cooled four-stroke diesel engine were experimentally investigated at full load conditions. The TSOME is mixed with diesel fuel in the mass rates of 10, 20, 50 and 100% (B10, B20, B50 and B100), and all the results tested with TSOME blends were compared with those of the standard diesel fuel. Comparing TSOME with standard diesel fuel, both the brake torque and the power of the engine were found higher 2·5% at B50. Hydrocarbon, CO and smoke emissions are measured lower, whereas the NOx emissions are found high.

Duvar akışlı bir partikül filtresindeki basınç kaybının deneysel ve nümerik incelenmesi

Dizel motorlarda yanmanin tam verimle gerceklesmemesi sonucunda zararli gazlar ve partikul madde cevreye atilmaktadir. Dizel motorlar fakir karisimda calistiklarindan dolayi azot oksit ve partikul madde emisyonlari fazladir. Dizel motorlarda, partikul madde emisyonlarini kontrol altina almak icin partikul filtreleri kullanilmaktadir. Partikul filtresi, icerisinde egzoz gazlarinin capraz akis yapmasini saglayarak kati ve sivi partikul madde emisyonlarini biriktirmek icin tasarlanmistir. Bu calismada, dizel partikul filtresinin basinc kaybi kurulan deney duzenegi uzerinde olculmustur. Olcumler sonucunda partikul filtresine ait gecirgenlik ve icsel kayip katsayisi hesaplanmistir. Sonlu elemanlar yazilimi kullanilarak basinc kaybi analizi gerceklestirilmistir. Calisma sonunda deneysel ve numerik sonuclar karsilastirmali olarak verilmistir.