a SciTechnol journal Research Article Kumar and Kailas, Res Rep Metals 2017, 1:4 All articles published in Research and Reports on Metals are the property of SciTechnol, and is protected by copyright laws. Copyright © 2017, SciTechnol, All Rights Reserved. Research and Reports on Metals International Publisher of Science, Technology and Medicine Evolution of In-Situ Nano-Pores during Friction Stir Processing of Polymer Derived Ceramic Reinforced Metal Matrix Composites Ajay Kumar P 1 * and Satish V. Kailas 2 Abstract Nano-porous ceramics have potential applications as diverse as biomedical implants, catalysis, and armors. This work shows that in- situ Nano-porous Polymer Derived Ceramics (PDC) can be produced in Metal Matrix Composites (MMCs) using solid state Friction Stir Processing (FSP). Direct insertion of cross-linked polymer into the metal by FSP in solid state is a signifcant step toward inserting different chemistry of polymer precursors to generate a variety of in-situ porous structures in Polymer Derived (PD)-MMC. The PDC route is an effcient and cost effective way to produce SiCN- based PD-MMC and tailored pore architecture suitable for high temperature applications. Microstructural observations indicate a uniform distribution of ~100 nm size pores in the ceramic phase after pyrolysis. Keywords Polymer derived ceramics; Porous materials; Friction Stir Processing; Metallic composites *Corresponding author: Ajay Kumar P, Department of Materials Science and Engineering, University of Wisconsin-Milwaukee-53201 WI, USA, E-mail: ajaykumarmech85@gmail.com Received: December 13, 2017 Accepted: December 25, 2017 Published: December 30, 2017 Introduction Polymer Derived Ceramics (PDCs) represent a unique class of high-temperature stable materials synthesized directly by the thermal decomposition of polymers. PD silicon carbonitride (Si-C-N) ceramics are candidate materials for high temperature structural and functional applications in the form of fbers [1], protective coatings [2], fber and particulate-reinforced composites [3]. In air, they are stable up to 1500 o C. Te synthesis of the materials involves cross-linking and/or pyrolysis of suitable organo-silicon precursor polymers in inert atmosphere, leading to ceramics with high purity, controlled structure and chemical composition [4]. Fabrication of the non-oxide Polymer Derived Porous Ceramics (PDPC) via the method of PDC is a novel technique. Furthermore, PDPC can be synthesized at a temperature as low as 1000 o C free of any additives, and cost- efcient manners which cannot be performed by the powder-route technique. Porous ceramics possess number of favorable properties which combine the merits of ceramics and porous materials such as light weight, low density, low thermal conductivity, low dielectric constant, thermal stability, high specifc strength, high specifc surface area, high porosity, high permeability, high wear resistance, and high resistance to chemical attack [5]. FSP has successfully evolved as an alternative technique for fabricating MMCs [6]. FSP depends on the standards of Friction Stir Welding (FSW) [7]. In FSW, a rotating tool with a pin and a shoulder are inserted into the material to be joined and traversed along the line of the joint. Te friction between the tool and the work piece resulting in localized heating that sofens and plasticizes the material. In the FSP of MMCs, the material undergoes intense plastic deformation resulting in the mixing of ceramic particles and the metal. FSP also results in signifcant grain refnement [8] and has also been used to homogenize the microstructure of Nano composites [9]. Our previous published work reported the fabrication of in- situ Nano PD-MMC by Friction Stir Processing (FSP) [10]. In this paper, a unique method of producing in-situ Nano porous PDC in solid state using FSP has been introduced. We report the evolution of in-situ Nano pores/cracks in PDC particles when SiCN cross- linked polymer was reinforced in copper metal matrix during multi- pass FSP. Tis method difers from the conventional methods used for producing porous ceramics and nobody has reported as per the author’s knowledge. Te pores developed in PDC particles have been micro structurally characterized in detail to understand the pore distribution and its morphology. Experimental Procedure A commercially available product, KDT Ceraset Polysilazane 20 (VL20) owned by Kion Corporation was used as the polymeric precursor for preparation of SiCN ceramics. Te VL20 is a versatile liquid thermosetting resin. Tis polymer contains repeated units of silicon and nitrogen atoms which are bonded in an alternating sequence. Te matrix material selected in the present study is pure copper (99.9%). SiCN cross linked polymer powder, having angular shaped particles with an average size of 10μm is used as reinforcement [10]. Te powder is a cross-linked polymer having a density of ~1.0 gcm −3 . Grooves (3 mm x 4 mm) were cut and holes (ϕ=3 mm) were drilled into a 6 mm thick copper plate and were flled with the above mentioned polymer powder. Four passes of FSP were carried out on a fve-axis friction stir welding machine (BiSS - ITW, Bangalore) on the groove at a tool rotation speed of 1500 rpm and traverse speed of 25 mm/min. A frustum shaped threaded Densimet tool with shoulder diameter, pin diameter and pin length of 25 mm, 6 mm and 5 mm, respectively was used. A tool tilt angle of 3 o was used. Te processed plate was then pyrolysed at 800 °C in mufe furnace for 30 min to convert polymer into ceramic [10]. Te samples were carefully polished using standard methods and ground with SiC abrasive papers through 3000 grit. Ten the samples were polished with alumina slurry and fnally with diamond paste using polishing machine. Ultrasonic cleaning was done for all samples to make the surface of the specimen free from dust/abrasive particles and preferably free of oxide layers. Samples were characterized using Scanning Electron Microscopy (SEM) (Sirion, Model VL 30FEG) with Energy Dispersive Spectroscopy (EDS) and Transmission Electron Microscopy (TEM, F-30).