Fuel effects on properties of alumina nanoparticles synthesized by combustion technique

Transcription

1 Indian Journal of Pure & Applied Phyic Vol. 54, June 2016, pp Fuel effect on propertie of alumina nanoparticle yntheized by combution technique M Fazli a *, M J Tafrehi b, F Butan Afruz b & A Rahmani a a Faculty of Chemitry, Semnan Univerity, Semnan, Iran b Faculty of Phyic, Semnan Univerity, Semnan, Iran Received 22 June 2014; revied 21 March 2016; accepted 11 May 2016 Alumina nanopowder have been produced by olution combution ynthei uing aluminum nitrate a oxidizer and urea (U), ammonium acetate (AA) and ammonium nitrate (AN) a fuel. The fuel effect on propertie of product have been tudied. Enthalpy and adiabatic flame temperature are calculated theoretically for each fuel baed on thermodynamic concept to determine it exothermicity. Thermogravimetric (TG) analyi ha alo been carried out to determine the thermal propertie of the metal nitrate and fuel. The prepared ample have been characterized by X-ray diffraction (XRD), N 2 adorption (BET) and canning electron microcopy (SEM). The reult how that by reducing the exothermicity of reaction, alumina nanopowder with maller crytallite ize, finer agglomerate and higher pecific urface area are produced. Keyword: Solution combution ynthei, Fuel, Alumina, Thermodynamic calculation 1 Introduction Among the large number of technique employed for the ynthei of oxide, olution combution ynthei i imple, low cot and rapid production proce with energy and time aving 1-. Thi technique ha uccefully been applied to produce variety of alumina phae uch a γ-alumina that i an extremely important material in catalytic urface activity 4,5. Variou method uch a ol gel 6, hydrothermal proceing 7 and control precipitation 8 have been employed to produce alumina nanopowder. Mot of thee technique are quite complicated and need high temperature and long proceing time 1,9. Among the variou control parameter in a combution proce, fuel play an important role in determining the propertie of product. It ha been reported that characteritic uch a particle ize, urface area, extent and nature of agglomeration are primarily governed by enthalpy or flame temperature generated and the amount of the gae that ecape during combution. Thee factor themelve depend on the nature of the fuel Combution proce ha the advantage of choice of a wide variety of fuel. Urea eem to be the mot convenient one to be employed in thi technique to produce alumina nanotructure, but uing urea a fuel directly yield *Correponding author ( mfazli@emnan.ac.ir) α-alumina powder with high crytallite ize, low pecific urface area and hard agglomerate, becaue of the formation of table polymeric intermediate that prevent the diipation of heat and thereby intering the oxide during combution 10, 1. So, other fuel have been ued in pure form or mixed with urea to reduce energy of reaction and improve ize and pecific urface area of alumina nanoparticle. Thee reearche have hown that utilization of variety fuel lead to different thermal reaction and production of powder with different propertie 2,5,1-18. Recently, we reported ynthei of alumina nanoparticle uing ammonium carbonate ((NH 4 ) 2 CO ) and ammonium ulfate ((NH 4 ) 2 SO 4 ) a two new fuel. Thee fuel can produce alumina nanoparticle of maller crytallite ize and higher urface area in compared with other fuel 19. Therefore, fuel containing ammonium are propoed a a new group of fuel to produce alumina nanoparticle of maller crytallite ize and higher urface area. In thi paper, we are reporting ynthei of alumina nanoparticle uing ammonium acetate, ammonium nitrate and urea to compare the reult obtained from utilizing fuel containing ammonium with urea. Thee two fuel have lower enthalpy and flame temperature compared with urea, o we predict production of better reult. In addition, fuel effect and thermodynamic of combution

2 FAZLI et al.: FUEL EFFECTS ON PROPERTIES OF ALUMINA NANOPARTICLES 407 ynthei on pecific urface area, crytalline ize and agglomerate ize ditribution of the prepared powder are invetigated. 2 Experimental Procedure In all the experiment Merck analytical reagent were ued a raw material. Aluminum nitrate nonahydrate (Al(NO ).9H 2 O) wa ued a oxidizing agent. Urea (CO(NH 2 ) 2 ), ammonium acetate (CH COONH 4 ) and ammonium nitrate (NH 4 (NO ) were ued a fuel. Suitable amount of toichiometric tarting material wa diolved in minimum amount of deionized water. Then, the dih containing aprepared precuror heated in a pre-heated furnace maintained at 400 С. The material foamed, decompoed and generated large volume of gae. Then pontaneou ignition occurred and underwent moldering combution with enormou welling, producing a foamy, voluminou ma. The voluminou foamy ma wa eaily cruhed to the powder. The ample prepared from ammonium acetate and ammonium nitrate were calcined at 700 С. The alumina powder obtained were named a SU (urea a fuel), SN (ammonium nitrate a fuel) and SA (ammonium acetate a fuel). The crytallinity and phae identification of yntheized powder were determined by uing D4 Bruker X-ray diffractometer with Cu-Kα a the radiation ource and Ni a the filter. To confirm the reult obtained from X-ray diffraction regarding phae and nature of product, TG analyi wa carried out in air atmophere with TGA Q50 V6. ytem in the temperature range between 25 C and 700 C at a heating rate of 20 C/min to ae the weight loe due to converion of precuror. The urface area of yntheized powder wa calculated according to the Brunnauer-Emmet-Teller (BET) procedure by uing the data of adorption of nitrogen on the ample at 77 K auming the cro ectional area of 0.16 nm 2 for the nitrogen molecule by adorption analyzer (BEL Japan, Inc). SEM micrograph of the ample were recorded uing XL-0 /TMP electron microcope. Reult and Dicuion.1 Thermodynamic modeling In combution ynthei of a fuel-nitrate mixture, an exothermic reaction occurred and mixture underwent a elf-propagating and non-exploive reaction. Different type of fuel caued different thermal reaction 20. Combution reaction occurred following different fuel-to-nitrate mixture. Thee reaction are expreed a follow: 2Al ( NO).9H + 5H 4N 2CO Al + 5CO ( ) 2( g ) + 28H g ) + 8N 2( g ) (1) 2Al ( NO).9H + 2.7CH COONH 4 Al + 4.6N H ( ) 2( ) g ) CO g 2( g (2) 2 Al ( NO ),9H + NH 4 NO Al + 10 NO ( ) 2 + N ( ) H g ( g ) g ) () For comparing exothermicity of different fuel in reaction with the nitrate, enthalpy and adiabatic flame temperature of the reaction between urea, ammonium acetate and ammonium nitrate with aluminium nitrate were calculated in the toichiometric condition, by the following equation: T H c = ( n H p ) - ( n H r ) = - f and T = T0 f H + r H nc p p T0 ( nc p ) dt (4) (5) where H c, H p and H r are the enthalpie of combution, product and reactant, repectively; T f i the adiabatic flame temperature, T 0 i 298 K and C P i the molar heat capacity of product at contant preure. The thermodynamic data for the variou reactant and product are lited in Table 1. To invetigate evolution of energy and flame temperature during combution, the enthalpie of combution and adiabatic flame temperature were calculated for each fuel according to Eq (4) and (5) and preented in Fig. 1. Urea ha higher exothermicity due to higher enthalpy of reaction with aluminum nitrate and it how more flame than AN and AA fuel during combution reaction, o thi enthalpy of combution and adiabatic flame temperature effect on propertie of produced powder. Table 1 Thermodynamic data for the variou reactant and product 2,1 Compound ( H f ) (kcal/mol) C p (cal/mol.k) Al(NO ).9H 2 O () NH 4NO () CH COONH CO(NH 2 ) 2() -56. N 2(g) T Al 2 O () T H 2 O (g) T CO 2(g) T )

3 408 INDIAN J PURE & APPL PHYS, VOL 54, JUNE 2016 Fig. 1 Calculated enthalpie and adiabatic flame temperature of reaction between fuel and nitrate.2 Thermal analyi In order to explain the predilection of aluminum nitrate with repect to different fuel, thermal analyi wa carried out. The decompoition rate of aluminum nitrate below 160 C i much higher than it value above 160 C, o thermal decompoition of aluminum nitrate take place at 15 C. Urea decompoe at 1 C which lie in the temperature range in which aluminum nitrate decompoe with maximum rate. Overlapping the decompoition temperature of aluminum nitrate and urea trigger an energetic combution reaction that yield α-alumina powder. On the other hand, it ha been oberved that fuel uch a glycine and citric acid which decompoe at 240 C and 175 C, repectively, give moldering combution with aluminum nitrate leading to the formation of amorphou powder 21. Similarly, in thi work ammonium acetate decompoe at 165 C and ammonium nitrate decompoe above 200 C, o their reaction give moldering combution leading to the formation of amorphou powder and only after annealing they change to crytalline alumina. An elevated adiabatic temperature doe not necearily imply a vigorou combution reaction. According to different author, the ignition mechanim of combution proce uually take place between the gaeou decompoition product of metal nitrite and fuel 21. Therefore, it can be inferred that a prerequiite for the occurrence of combution reaction in metal nitrate/fuel ytem i the exitence of an overlapping temperature interval in which thermal decompoition of metal nitrate and fuel occur imultaneouly 21. The thermal behavior of aluminum nitrate mixture with different type of fuel uing TG analyi i Fig. 2 TG analyi for different type of fuel-to-nitrate mixture Fig. XRD pattern of prepared powder hown in Fig. 2. Different fuel how different thermal decompoition behavior. Decompoition tart below 200 C for all the ample. The reaction of ample SU take place rapidly. It i very teep, howing that the reaction take place rapidly. The rapid lope weight lo at C aociated with the rapid auto ignition, another crucial factor, i the fat cooling due to the rapid evolution of the gae during auto-ignition. In the SN and SA ample, the lope were le teep when compared to SU, indicating leer decompoition in temperature range of C.. Phyico-chemical characterization The XRD pattern of the ample have been hown in Fig.. It how that ample SU (alumina prepared by urea) i in the alpha phae correponding to previou which i in conitent with other report 10,1. Thi figure alo how that the ample SA and SN are in gamma phae and they are pure crytalline in nature. Broadening of the peak clearly how the

4 FAZLI et al.: FUEL EFFECTS ON PROPERTIES OF ALUMINA NANOPARTICLES 409 nano-ize nature of crytallite (Fig. ). The crytallite ize were calculated uing the Scherrer equation. kλ D = β coθ where k i a contant ~0.9, λ i the wave length of the X-ray, β i the full width of diffraction peak at half maximum (FWHM) intenity and θ i Bragg angle. The calculated crytallite ize were found to be almot 7,.5 and nm for ample SU, SN and SA, repectively. Thee reult how that uing ammonium group fuel lead to reduction in exothermicity of reaction and production of alumina with maller crytallite ize. The urface area, pore ize ditribution and average pore volume data for different ample are given in Table 2. The pore ize ditribution of prepared powder from BJH method i hown in Fig. 4. Table 2 how that the ample SN and SA have higher urface area a compared to that of the ample SU, and ample SA ha bigger average pore ize and pore volume in comparion with other ample which i in conitent with Fig. 4. So, by reduction in exothermicity of reaction between fuel and aluminum nitrate the urface area increae and there i reduction in crytallite ize and agglomerate ize attributed to decreae in flame temperature. There i a correlation between the increae in crytallite ize and the reduction of urface area a a function of type fuel (Table 2). Many author have already reported thi relationhip 2,18. A particularly deirable property of γ- alumina i it high pecific urface area and the related adorption characteritic, which can be affected by the raw material and the preparation procedure 22. The SEM micrograph of the ample are hown in Fig. 5. For all the ample, the micrograph have exhibited foamy agglomerated particle and large void in their tructure, which are attributed to the evolution of a large amount of ga during combution. A it can be een, all ample have exhibited flaky Table 2 The urface area, pore volume and average pore ize for ample yntheized by different fuel Sample Specific urface area (m 2 /g) Pore volume (cm /g ) Average pore ize (nm) SU SN SA Fig. 4 Pore ize ditribution of prepared powder obtained from BJH method Fig. 5 SEM micrograph of the ample

5 410 INDIAN J PURE & APPL PHYS, VOL 54, JUNE 2016 morphology, and ample SA and SN have finer agglomerate. 4 Concluion Effect of fuel and thermodynamic of combution on propertie of alumina nanoparticle prepared by combution reaction were tudied. Ammonium acetate, ammonium nitrate and urea were ued to produce alumina nanoparticle via olution combution ynthei. For thee three fuel, thermal behavior wa predicted by thermodynamic calculation and meaured by TG analyi. Due to change in thermal parameter uch a enthalpy, adiabatic flame temperature, energy releaed from reaction and decompoition temperature, ammonium group fuel reulted in yntheizing high pecific urface area (200 m 2 /g) and fine particle ize (nm) γ-alumina nanoparticle where a thee two value were found to be 18.4 m 2 /g and 7 nm for α-alumina nanoparticle yntheized by urea. Pore ize, pore volume and micrograph of the ample were found to be in conitent with our earlier tudied reult. Acknowledgement The author are much thankful to Iran Nano Technology Initiative council and reearch council of Semnan Univerity for all their financial upport. Reference 1 Biaminoa S, Ambroiob E P, Manfredib D, Finoaand F & Badini C, J Ceram Proc Re,12 (2011) Toniolo J C, Lima M D, Takimi A S & Bergmann C P, Mater Re Bull, 40 (2005) 561. Tyagi A K, Chavan S V & Purohit R D, Indian J Pure Appl Phy, 44 (2006) 1. 4 Gangwara J, Deya K K, Praveena K, Tripathib S, Srivatavaa A K, Adv Mater Lett, 2(6) (2011) Butan Afruz F & Tafrehi M J, Indian J Pure Appl Phy, 52 (2014) Akia M, Alavi S M, Rezaei M & Yan Z F, Porou Mater, 17 (2010) Noguchi T, Matui K, Ilam N M, Hakuta Y & Hayahi H, Supercrit Fluid, 46 (2008) Parida K M, Pradhan A C, Da J & Sahu N, Mater Chem Phy, 11 (2009) Baburao N S & Arun M U, Int J Emerg Technol Adv Eng, (201) Aruna S T, Kini S N & Rajam K S, Mater Re Bull, 44 (2009) Prakah A S, Shivakumara C & Hegde M S, Mater Sci Eng B, 19 (2007) Mukayan A S & Dinka P, Int J Self-Propag High-Temp Synth, 16 (2007) 2. 1 Tahmaebi K & Paydar M H, Mater Chem Phy, 109 (2008) Aruna S T & Rajam K S, Curr Opin Solid State Mater Sci, 12 (2008) Ganeh I, Torre P M C & Ferreira J M F, Ceram Int, 5 (2009) Edrii M & Norouzbeigi R, Mater Sci-Poland, 25 (2007) Peng T, Liu X, Dai K, Xiano J, Song H, Mater Re Bull, 41 (2006) Edrii M & Norouzbeigi R, J Am Ceram, 94 (2011) Butan Afruz F, Fazli M & TafrehiM J, J Nanotruct, 2 (2012) Jamil R S, Razak K A, Ahmad N F& Mohamad H, Mater Eng Perform, 21 (2012) Iano R, Lazau I & Pacurariu C, Mater Sci, 44 (2009) Granado-Correa F, Int J Appl Ceram Technol, 1 9 (2012).