Microwave synthesis and magnetic investigations of surfactant assisted NiO nanostructures G. Anandha Babu a , Y. Hayakawa b , G. Ravi a,n a Department of Physics, Alagappa University, Karaikudi-630004, Tamilnadu, India b Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8011, Japan article info Article history: Received 16 November 2014 Accepted 21 February 2015 Available online 2 March 2015 Keywords: Nanoparticles Thermal analysis Microwave Surfactants CTAB Magnetization abstract Cubic phase of NiO nanoparticles have been prepared by applying microwave method and by using cetyl trimethyl ammonium bromide (CTAB), citric acid (CA) and hexamine (H). Size and morphology of nanoparticles have been ascertained through SEM and TEM analyses. Room temperature magnetic measurements reveal week ferromagnetic nature of NiO nanoparticles with higher saturation magne- tization (1.20 emu/g) for CTAB than citric acid and hexamine. FC and ZFC magnetization curves display low temperature peak around 12 K and it is due to the formation of hydroxide layers on NiO surface as well as due to the addition of surfactants during the synthesis. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Nickel oxide is of greater significance, because it is applied in diverse fields due to its excellent electrical, mechanical, optical, thermal and magnetic properties. The nanostructured nickel oxide has attracted significant interest and it shows anomalous behavior when its size is reduced to nano dimensions [1,2]. The size and morphology of NiO nanostructures are important factors to improve the magnetic performance of the materials. It is believed that the addition of surfactants can be used to produce the materials with well defined size and shape [3]. Recently, microwave assisted heating finds relatively appreciable method for production of NiO with definite shape and uniform size as well as their excellence perfor- mance on synthesis route. This method is not simply used to reduce reaction time and suppresses side reaction which is a most preferable condition for aligned morphology [4]. In the present study, the effect of adding CTAB, citric acid and hexamine were investigated for magnetic performance of NiO nanostructures. 2. Experimental section Analytical grade of nickel nitrate, sodium hydroxide, citric acid, cetyl trimethyl ammonium bromide (CTAB) and hexamine were purchased from Merck. All the chemical reagents were used as received without any further purification. In a typical experiment, 0.5 M of Ni (NO 3 ) 2 Á 6H 2 O was dissolved in 50 ml distilled water to form a transparent solution. 1 g of CTAB was added to the above solution under vigorous stirring, followed by the addition of 20 ml of 2 M NaOH solution drop wise to form a clear blue solution at pH 9. The resultant solution was transferred to poly propylene capped autoclave bottles. Then, the solution was irradiated by microwave with the power of 300 W for 15 min. The same procedure was followed for citric acid (1 g) and hexamine (1 g) assisted nickel nitrate solutions. The resulting pale green precipitates were collected by centrifugation and the precipitates were rinsed with distilled water and absolute ethanol for several times to remove soluble ions and impurities. The precipitate was dried at 110 1C in a hot air oven for 12 h to get the sample of Ni (OH) 2 architectures. Then, the prepared powder was calcined under air at 400 1C for 2 h to obtain NiO nanoparticles. The NiO synthesized by using CTAB, citric acid and hexamine is denoted as S1, S2 and S3. 3. Results and discussion Fig. 1a demonstrates the TGA curve of as-synthesized sample (S1). The weight loss occurs below 140 1C is an indication of removal of water content from the sample. The weight loss appears between 140 and 290 1C is attributed to the decomposi- tion of nickel hydroxide and elimination of nitrate and surfactant related compound in the sample. Hussin et al. elucidated the Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters http://dx.doi.org/10.1016/j.matlet.2015.02.107 0167-577X/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. E-mail addresses: gravicrc@gmail.com, raviganesa@rediffmail.com (G. Ravi). Materials Letters 149 (2015) 54–57