Seramik tozlarının çeşitli şekillendirilme yöntemleri vardır. Bu yöntemler soğuk veya sıcak, yaş veya kuru olmak üzeri çeşitli şekillerde sınıflandırılabilir. Bu çalışmada, mühendislik seramiklerinin şekillendirilmesinde diğer şekillendirme yöntemlerine nazaran daha düşük maliyetli ve daha kolay bir üretim prosesine sahip yeni bir şekillendirme yöntemi denenmiştir. Bu yöntem iki farklı şekillendirme yönteminin birleştirilmesi esasına dayanır. Yaş döküm yöntemi ile enjeksiyon kalıplama yönteminin birleşimi şeklindedir. Polimer katkılı sıcak akışkan seramik toz karışımı bir kalıp içine basınç uygulamadan dökülerek şekillendirilir. Zirkonya ($ZrO _2$), magnezya (MgO) ve kalsiya (CaO) tozlarından farklı bileşimlerde mekanik alaşımlama tekniği ile karışımlar hazırlanmıştır. Bağlayıcı sistemi, parafin (%95 ağ.) ve oleik asit (%5 ağ.) olan, hacimce %60 bağlayıcı ve %40 seramik tozu içeren karışımlardan basınçsız sıcak şekillendirme yöntemiyle numuneler hazırlanmıştır. Hazırlanan numunelerden bağlayıcı giderme çalışmalarında iki kademeli bir işlem kullanılmıştır. Bağlayıcı giderme çalışmalarının ilk aşamasına ait şartlar, 120°C’de 5 saat olarak belirlenmiştir. Ağırlıkça yaklaşık %33 bağlayıcı giderilen söz konusu şartlar, çalışılan tüm numunelere uygulanmıştır. İkinci aşamada ise, geri kalan bağlayıcı, atmosfer şartlarında bağlayıcı giderme fırınında 600°C’nin altında tamamen giderilmiştir. Bu işlem tamamlandıktan sonra numuneler, 1600°C’de 3 saat sinterlenmiş ve oda sıcaklığına soğutulmuştur. Sinterlenmiş bazı numuneler 1450°C’de 4 saat yaşlandırmaya bırakılmıştır. Sinterlenmiş numunelerin XRD ve SEM kullanılarak faz analizi ve mikroyapısal karakterizasyonu yapılmıştır.

Oxide ceramics include alumina, zirconia, silica, aluminum silicate, magnesia and other metal oxide based materials. Oxide ceramics have high melting points, low wear resistance, and a wide range of electrical properties. Oxide ceramics are used in a variety of applications. Examples include chemical and materials processing, electrical and high voltage power applications, Radio Frequency (RF) and microwave applications, and foundry and metal processing. “Zirconia-Ceramic steel?” The title of the first scientific paper to highlight the possibilities offered by the "transformation toughening" mechanism which occurs in certain zirconia ceramics. Since the publication of this seminal work in 1975, considerable research, development, and marketing efforts have been expanded on this single material which offer the traditional ceramic benefits of hardness, wear resistance and corrosion resistance, without the characteristic ceramic property of absolute brittleness. Zirconia, $ZrO _2$ exists as a monoclinic crystal at room temperature inverting to tetragonal phase above approximately 1200°C. The addition of large amounts of a stabilizer such as magnesium oxide will induce a cubic crystal structure during firing that does not revert to the monoclinic phase upon cooling. The addition of generally less than 10% by weight of stabilizers yields high-density ceramic bodies known as transformation toughened zirconia. Two fundamentally different microstructures exist depending upon the added stabilizer. The addition of MgO yields a relatively coarse grained (50-100 micron) microstructure known as Mg-PSZ. The grains are predominantly cubic morphology with a fine precipitate of tetragonal phase dispersed within the grain. Yttria, $Y _2O _3$, additions yield an extremely fine grained (less than 1 micron) microstructure known as Y-PSZ or TZP or tetragonal zirconia polycrystal. The individual grains are completely tetragonal. In present study, Calcia and Magnesia stabilized fine Zirconia powders in various ratios were studied. Powder mixtures (Ca(OH)2, Mg(OH)2 and ZrO2) were prepared in acetone and milled as wet with YSZ (yitria stabilized zirconia) balls of 10 mm Ø for 3 h. Particle size of Calcia, Magnesia and Zirconia powders were submicrometer. The pressureless hot molding technique has been selected for forming of the partial stabilized zirconia with MgO and CaO. Binder system for pressureless hot molding was a mixture of paraffin wax as primary binder and oleic acid as surfactant. Paraffin wax/oleic acid ratio was maintained at a value close to 95/5 as weight. Typical feedstock contained 40 vol. % ceramic powders, and 60 vol. % binder phases. A two-step process was used for debinding of green samples. In wicking step by capillary action, samples embedded in same ZrO2 powder in a copper box were put in an furnace in the 120, 150 and 180°C temperatures for 1, 3, 5 and 10 hours. The variation of sample weight with temperature and time was measured to calculate the debinding ratio. In the second step of debinding process, partially debinded samples were heated to 600°C at a slow heating rate. After completing this process, green ceramics were fired at 1600 °C for 3 hours in an electric-heated furnace and then cooled quickly. Some of the fired ceramics were aged in the same furnace for 4 hours at 1450 °C. After annealing, the some specimens were sectioned, ground, polished to 1 mm surfacefinish and finally thermally etched in air for 30 min. at a temperature 1420 °C. The density and porosity of sintered samples were measured by Archimedes principle. The microstructural characterization of the sintered samples was carried out using scanning electron microscopy. The morphological parameters of the various phases were characterized by using a semiautomatic image analyzer, EDS and the formed phases were analyzed by X-ray powder diffractometer using Co Kα radiation. Ca-$ZrO _2$ and Mg-$ZrO _2$ ceramics have been prepared by solid state reaction synthesis. The beneficial effects on the binder removal, microstructural characterization and phase structure of zirconia ceramics prepared by pressureless hot molding have been analyzed. t- $ZrO _2$ and c- $ZrO _2$ phase value increased with the addition of Calcia (CaO) and fired temperature and time. The addition of Calcia (CaO) to Zirconia ($ZrO _2$) matrix the highest the value of t- $ZrO _2$ and c- $ZrO _2$.