Comparative Structural Studies of the Silver and Nickel Nano Composites Synthesized by Chemical Methods


 Silver and nickel nanoparticles were synthesized from urea and formaldehyde by using chemical method, followed by calcination at 8000C. The chemical composition and crystallographic structure of silver and nickel nanoparticles were confirmed by XRD. Surface imaging studies like AFM was carried out for understanding surface morphology and particles size distribution. The spherical and porous-like morphology of silver and nickel nanoparticles were confirmed by SEM and TEM. White spots are observed because of the the presence of silver and nickel metal ions in spherical forms. The particles size of silver and Nickel metal ions obtained through XRD are found to be 41.43 nm and 13.71 nm respectively.


Introduction
Polymeric materials are widely used in industry due to their ease of production, lightweight and ductile nature. A very effective approach to improve mechanical properties of polymer is to add bers, whiskers, platelets or particles as reinforcements to the polymer matrix. The polymer nanoparticles show enhanced properties after the incorporation of low amount of Nano llers such as carbon black (CB), carbon nanotubes(CNTs), graphene and Nano clay (Huang, 2002, Moniruzzaman et al. 2006, Kim et al. 2010,Fischer, 2003. Polymers have been lled with several inorganic compounds, either synthetic or natural, in order to increase heat and impact resistance, ame retardancy and mechanical strength, and to decrease electrical conductivity and gas permeability with respect to oxygen and water vapor (Hajji et al. 1999). Such composites are widely used in many areas like in electronics, catalysis, transportations and construction, because of their novel properties. Compared to conventional composite nanoparticles, polymer nanocomposites have ultra ne nanometer size phase dimensions and offer unique combination of properties due to the size (Sanchez et al. 2000, Sanchez et al. 1999, Pomogilo, 2000, Novak, 1993, Lichtenha et al. 2001, Sanchez et al. 1994, Ells et al. 1999, Kwiatko et al. 2000, Schubert et al. 1995, Mori Kawa et al. 1992, Giannelis et al. 1999, Jordan et al. 2005. The properties of polymers can be improved by doping with metal nanopartilces , Chang et al. 2002, Zavyalov et al. 2002. Another important aspect of nanoscale reinforcement is that it has exceptional potential to generate new phenomena giving rise to special properties in these materials. Urea-Formaldehyde (UF) resin is widely used as thermosetting materials due to low cost and good thermal and mechanical properties including chemical resistance. This resin, which is the condensation product of urea and formaldehyde, are used with reinforcing llers or bers to produce composite materials for use in a wide  (Liu et al. 2003) and micro emulsion polymerization ). All these methods of nanoparticle formation require high temperature and expensive instruments. One of the simplest and cost effective techniques to prepare the silver and nickel nanoparticles is by thermal decomposition. This technique has various advantages over other method. These include a reaction that can be easily controlled requiring short reaction time for the preparation of different type of nanoparticles (Traversa et al. 1998, Farhadiet al. 2010).
Amongst the metal nanoparticles, Ag NP is becoming an increasingly important material in many technologies. Ag NPs exhibit the highest e ciency of Plasmon excitation and is the only material whose Plasmon resonance can be tuned to any wavelength in the visible spectrum. Ni NPs have also been getting importance because of its application as catalysts and conducting and magnetic materials (Kulkarni, 2015). The objective of this study has been to synthesize silver and nickel nanoparticle by using urea and formaldehyde resin as precursors, followed by thermal decomposition. The synthesized nanoparticles have been characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM).

Material And Methods
Silver nitrate (AgNO 3 ), Nickel Chloride Hexahydrate (NiCl 2 .6H 2 O), Formaldehyde (HCHO) and Urea (NH 2 CONH 2 ) were purchased from Central Drug House Pvt. Ltd. and Sodium Hydroxide (NaOH), hydrochloride Acid (HCl) were purchased from Fisher Scienti c. All solvent was of analytical reagent grade and were used without further puri cation for the preparation of metal solutions.
Silver and Nickel nanoparticle were synthesized by the following steps: Step1: Formation of polymer metal complex Step2: Formation of silver/ nickel nanoparticle Step 1: Formation of Polymer metal complex 1.38 mole of urea, 1.13 moles of formaldehyde and 15 ml glacial acetic acid add in three-necked round bottom ask equipped with re ux condenser and stirrer. The mixture was agitated and was allowed cool off. Water was removed by slowly raising the temperature to 60 0 Cand applying a vacuum by means of water pump. This temperature was maintained till the melting of sample which on cooling solidi es into a white colored solid. Then 15 ml of silver and nickel metal solution were added to prepare polymer metal complex respectively. The reaction is exothermic in nature. The dried solid sample was puri ed by washing with distilled water.
Step2: Formation of silver and nickelnanoparticles: The polymer metal complex calcinated at 800 0 C for 45 minutes in mu e furnace. Black colored silver and nickel nanoparticles were obtained (Chaudhary et al. , 2018. Puri cation of silver and nickel nanoparticles: Metallic ions were removed from the nanoparticle by keeping it in 12N hydrochloric acid solution for 24 hours. The mixture was centrifuged and washed with distilled water till hydrochloric acid was completely removed (Chaudhary et al. 2018). The volatile impurities got separated at time of calcination.

Result And Discussion
Morphological Studies: SEM images of silver nanoparticles are shown in Fig. 1 ((A and B). The grey coloured bulk regions indicate bulk polymer matrix and white spherical spots are the distribution of silver nanoparticles. The surface is completely rough due to homogeneous distribution of silver particles which are aggregated on polymer surface. SEM images of nickel nanoparticles are shown in Fig. 2(A andB). Spherical pores are observed on the polymer surface. Interestingly, the morphology of nickel nanoparticle show the carbon black porous like structure and some particles show granular type structure.
Microstructural characterization studies were conducted to determine the size of nanoparticles, homogeneity and size distribution. TEM images of silver nanoparticles as shown in Fig. 3

(A) and (B)
respectively show globular as well as rod-like structure on the polymer surface. The black coloured spot on polymer surface indicate metal particles and white bulk part is polymer matrix. X-ray Diffraction (XRD) Analysis:   Table 4 Calculations of XRD for Nickel Nanoparticles

Conclusion
Silver and nickel nanocomposites were synthesized by chemical precipitation method followed by thermal decomposition which is greener and environmentally suitable, cheap and time-saving as compared to conventional methods.The morphology studies by SEM show that the silver nanoparticles are spherical and nickel nanoparticles have pore-like shapes like that of carbon-black. The particle sizes were determined by XRD and compares well with previous studies and surface to volume area results of AFM studies also indicate the exact structure and probable properties of the synthesized nanoparticles.Our results are good indicative of the e cacy of the chemical precipitation method in the synthesis of the nanoparticles.In future, these Silver nanoparticles can be further analyzed for its heat transfer properties and application in nano uids and conductive gels. It is also proposed to investigate the catalytic activity of nickel nanoparticles in future. Not applicable. The corresponding author may be contacted for data.

Competing interest
The authors declare no con ict of interest.

Funding statement
This research did not receive any speci c grant from funding agencies in the public, commercial, or notfor-pro t sectors.

Author contributions
Giriraj Tailor: Conceived and designed the experiments; Analyzed and interpreted the data; Drafted the paper.
Jyoti Chaudhary: Contributed reagents, materials, analysis tools for data.
Bhupendra Kr. Sarma: Provided lab facilities for carrying out the experiments and checked the draft of manuscript.

Con icts of Interest:
The author(s) declare(s) that there is no con ict of interest regarding the publication of this paper.    Reaction for the nickel and silver nanoparticle