Evaluation of the Apatite Coating on Silicon Nitride Based Ceramics Sintered With RE 2 O 3 Additives (RE = Y, La, Yb) Juliana Marchi 1, a , Cecília Chaves Guedes e Silva 2, b , Eliana Cristina da Silva Rigo 3, c , Ana Helena de Almeida Bressiani 2, d and José Carlos Bressiani 2, e 1 Centro de Ciências Naturais e Humanas, (CCNH), Universidade Federal do ABC (UFABC), Santo André, SP, 09210-170, Brazil 2 Centro de Ciência e Tecnologia de Materiais (CCTM), Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Paulo, SP, 05508-000, Brazil 3 Departamento de Ciências Básicas (ZAB), Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo (USP), Pirassununga, SP, 13635-900, Brazil a juliana.marchi@ufabc.edu.br, b cguedes@ipen.br, c eliana.rigo@usp.br, d abressia@ipen.br, e jbressia@ipen.br Keywords: silicon nitride, sintering additives, biomimetic coating, bioactive surface. Abstract. As alternative for alumina and zirconia implants, silicon nitride based ceramics are considered promising candidate due to its biocompatibility and mechanical properties. However, this materials exhibit a bioinert character, leading to clinical failures. To overcome this problem, a biomimetic coating of hydroxyapatite is proposed in this paper, so that the surface can be bioactive and, consequently, the osteointegration process can be enhanced. Silicon nitride samples were sintered with different additives (Y, La and Yb) and the surfaces before and after coating were characterized by diffuse reflectance infrared Fourier transformed (DRIFT), X ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the surfaces of bioinert silicon nitride samples sintered with different additives could be transformed into bioactive by the formation of a hydroxyapatite layer through biomimetic process. Introduction Alumina (Al 2 O 3 ) was the first ceramic applied as biomaterial for total joint replacement. Despite the excellent biocompatibility, the low fracture toughness of such material can induce to brittle fractures. Zirconia (ZrO 2 ) was considered an alternative biomaterial, but have the disadvantage of high degradation rate in biological medium [1,2]. To overcome these limitations, other structural ceramics have been researched and proposed as bioinert materials, such as silicon carbide (SiC) [3,4] and silicon nitride (Si 3 N 4 ) [5,6]. Si 3 N 4 based ceramics have been used as structural materials in a wide range of applications due to their high hardness, high heat resistance, high fracture toughness and excellent wear resistance. The structural applications include heat exchangers, turbine and automotive engine components, valves and cam roller followers for gasoline and diesel engines, wear surfaces, etc [7,8,9]. As biomaterial, Si 3 N 4 is promising due to its non-cytotoxic behavior [10]. Nowadays, total hip arthroplastic bearings have been successfully manufactured from Si 3 N 4 powders [11]. It is known that additives are required to promote densification of Si 3 N 4 ceramics due to Si-N covalent bond and the low diffusion coefficient [12]. These additives are in general oxides, such as alumina, yttria, magnesia and rare earth oxides [13] that react with the silica layer on the Si 3 N 4 powder surfaces to form a liquid phase. Liquid phase sintering involves α-Si 3 N 4 particle rearrangement, dissolution of the α-phase, diffusion of Si and N atoms and precipitation of the β- phase [14], followed by grain growth [15]. The type and total amount of additives used can be adjusted to optimize the process and to increase the desired properties of the final Si 3 N 4 -based ceramics, depending on the application. These modifications render controlled microstructures that are composed of elongated grains. Eighth International Latin American Conference on Powder Technology, November 06 to 09, Costão do Santinho, Florianópolis, SC, Brazil 1747