Preparation of Ultrafine Silver Powder Using Glycerol as Reducing Agent

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1 Journl of Metls, Mterils n Minerls, Vol.18 No.2 pp.1-5, 28 Preprtion of Ultrfine Silver Power Using Glyerol s Reuing Agent Eksit NISARATANAPORN n Kittiporn WONGSUWAN Deprtment of Metllurgil Engineering, Fulty of Engineering, Chullongkorn University, Phythi R., Pthumwn, Bngkok 133, Thiln. Astrt Reeive June. 6, 28 Aepte Ot. 1, 28 The proution of silver nnoprtiles n su-miron prtiles n e hieve y silver lkoxie from silver sulfte n susequently reuing with glyerol. To reue the prtile size of silver sulfte preursors, ll milling ws employe to reue prtile sizes own to.81 mirons. However, silver sulfte without grining provie smller prtile sizes of silver prtiles s oppose to groun speimens. Stirring silver lkoxie simultneously ws effiient to provie for uniform istriution of silver power. The silver power thus proue h rin-like shpe onsiste of very fine ggregte silver prtiles. The yiel of silver power ws in the rnge of %. Silver power h f rystl struture y X-ry iffrtion (XRD). The verge prtile size n power luster sizes were in the rnge of 6 to 25 nnometers n from 6 to 3 mirons, respetively. The surfe res were pproximtely m 2 /g n pprent ensities were from.6 to 1.2 g/m 3. Key wors : silver nnoprtiles; silver power; ontrol of size Introution Nowys the hemil syntheses to ontrol uniform size n istriution of silver prtiles hve een ttrtive euse ultrfine prtiles n e wiely use in tlysts, eletronis, teriil tion n the jewelry inustry. Silver power n e proue through vrious methos suh s hemil reution, (1-3) physil proess (tomiztion n milling), eletrohemil n therml eposition. Among the vrious preprtive methos employe, hemil proesses offer istint vntge over the others in terms of power morphology s well s effiient sle-up for mss proution. The polyol proess inluing glyerol reuer (4) hs lso een suessfully use to otin reue metl power in finely isperse form. The ojetive of this pper is to stuy pproprite initil silver sulfte size, retion temperture, time n onition for ontrolling silver power sizes whih were proue from silver sulfte reue with glyerol s reuing gent. Mterils n Experimentl Proeures All hemils of regent gre qulity were use without further purifition. Silver sulfte ws proue y retion of silver metl with 98% onentrte sulfuri i (AR). Silver sulfte, use s preursor, ws groun y ll milling for 5, 1 n 2 h. in orer to reue silver sulfte size. Eh of the preursors ontining 1 g of Ag 2 SO 4 ws rought to ret with soium lkoxie in solute ethnol (Crlo, AR) for 1 h thus silver lkoxie ws ompletely otine. No protetive gent in the form of PVP or see prtile (nuleting gent) ws use. Then the smple of silver lkoxie ws reue y glyerol with mgneti stirring (8 rpm) t onstnt tempertures of 15 C n 18 C for 3 min n 1 h, respetively. The retion temperture ws mesure using thermometer sumerge in the solution through glss port. Silver power ws otine y retion of silver lkoxie with glyerol. The metlli silver power ws reovere from the solution, wshe n rie t 11 C for 1 h. The rystl struture of silver power ws hrterize y using X-ry iffrtion (XRD) metho on n X pert, moel PW381 (Phillipe) to ensure tht the metlli silver power ws ompletely n suessfully proue. Diret oservtion of the silver power luster n prtile morphology ws me y snning eletron mirosope (SEM) on JEOL (moel JSM-64) to revel the shpe, size n size istriution. The verge sizes n the

2 2 NISARATANAPORN, E. n WONGSUWAN, K. stnr evition were iretly mesure from SEM imge using SemAfore progrm. Surfe re ws mesure with BET surfe nlyzer on Miromeritis. Figure 1 illustrtes the flow hrt of the proess use for prouing the very fine silver prtiles using glyerol s reuing gent. Pure silver Sulfuri i Stirring silver lkoxie uring the retion with glyerol offers the uniform power luster s shown in Figure 3-. The unstirre system results in very huge power luster sizes ue to more gglomertion whih ours t the ottom of the eker. It ws foun tht metlli silver prtiles in the rnge of nnometer to su-miron ourre ue to the reue silver lkoxie power. Silver prtiles strte to join eh other to form silver lusters whih h rin-like or orl struture. Silver sulfte Soium s. ethnol Soium lkoxie Silver lkoxie + Soium sulfte Heting Preipitte silver power Glyerol Wshing 3 times y ethnol s. Wshing 1 times y istille wter Drying t 11 C for 1h Silver power Figure 1. Flow hrt of the proution proess Results n isussion To otin uniformly smll silver sulfte prtiles, ll milling ws use. The snning eletron mirogrphs of silver sulfte preursors fter grining for -2 h re shown in Figure 2-. Mesurement oring to (5) in ASTM stnr E2 ws use to mesure the sizes of irregulrly shpe prtiles. An initil verge size of silver sulfte (4.35 μm) n e reue to 2.88, 1.35 n.81 μm y ll milling for 5, 1 n 2 h, respetively. After stirring n heting the silver lkoxie for 1 h, white silver sulfte power eme lkish silver lkoxie. The shpe n size of silver lkoxie were similr to those of the initil silver sulfte. Figure2. SEM of silver sufte prepre from ll milling with vrious grining time (), () 5, () 1 n () 2 hr. A suitle onition to otin the smllest luster (Figure 3) with verge luster size of 6.5 μm is silver sulfte with initil size of 1.35 μm

3 Preprtion of Ultrfine Silver Power Using Glyerol s Reuing Agent 3 (ll milling for 1 h). Although the smllest initil size of silver sulfte (.81 μm) ws prepre y using the onition fter milling for 2 h, ut very lrge silver lusters were otine s shown in Figure 3. This might e ue to high surfe energy of the smll prtiles while there ws no protetive regent e. silver sulfte ffets the morphology of silver prtiles in the luster. The onversion of silver sulfte to silver power in ll teste onitions ws 95-99%. The power ws ollete n nlyze y XRD. The XRD ptterns of silver powers prepre through glyerol route in ll onitions re shown in Figure 4. The ptterns revel the iffrtion peks orresponing to f silver phse n no other elements n ompoun our. The SEM oservtion with higher mgnifition (15x) on the silver power luster from omplete retion is shown in figure 5-. Aggregte silver nnoprtiles n sumiron prtiles were proue on the surfe of silver lusters. Silver proue from groun (5 h) silver sulfte Ag [111] Retion temperture 15 C for 3 min Ag [2] Ag [22] Ag [311] Intensity Retion temperture 15 C for 1 hr Retion temperture 18 C for 3 min Retion temperture 18 C for 1 hr Thet Figure 4. XRD ptterns of silver power fter reution uner vrious onitions. Figure 3. Silver power ws proue t 15 C for 3 min y using preursors with () no grining, with grining time of () 5, () 1 n () 2 hr. Retion temperture t 15 C-18 C n holing time of 3 mins-1h uring the reution with glyerol insignifintly ffet the size n shpe of the silver luster. Only the initil size of The silver prtiles were in the form of irregulr shpe n joine together s rin-like shpe or orl struture. The gglomertion of silver prtiles is ue to the high surfe energy of silver prtiles. The exess surfe energy (6) is relese n onverte to therml energy. Besies, it ws foun tht grining, retion temperture n holing time uring the reution with glyerol ffete the verge prtile size. Tle 1 inites tht silver prtiles proue from silver sulfte without ll milling h smller verge size in rnge of 6-13 nm while those silver sulftes with ll milling provie lrger size (1-24 nm) Retion temperture n time tene to inrese the prtile size of metlli silver ue to higher quntity of retions ourring t higher temperture n over longer time spn. At

4 4 NISARATANAPORN, E. n WONGSUWAN, K. temperture of 15 C the prtile sizes reue from silver sulfte without grining were out 6-7 nm while the prtiles reue t 18 C h n verge of nm in size. However, there is no ler eviene to etermine the reltionship mong prtile size, temperture n time in the onition of the groun silver sulfte experiments ue to the flutution of mesure silver prtile size t elevte temperture whih my resulte from ll milling s shown in Tle 1. Tle 1. Averge prtile size of silver reue with glyerol in vrious onitions. Ag 2 SO 4 grining time Temp ( C), Time (min) Averge prtile size (nm) (mesure) Crystlline size (nm) (lulte) The rystlline size n e etermine y Deye-Sherrer eqution (7) from iffrtion pek of XRD results. The lulte verge rystlline sizes were in the rnge from 3 to 45 nm s shown in Tle 1 n then plotte (grph is shown in Figure 6). Although the results of rystlline size from lultion o not meet the tul size, they show liner reltion etween mesure tul prtile size n lulte rystlline size. When rystlline size is lrge, prtile size is lrge, too. Crystlline size (nm) Prtile size, Ag 2 SO 4 (nm) Figure 6. Shows liner reltionship etween tul prtile size n lulte rystlline size. Figure 5. SEM of silver prtiles proue from Ag 2 SO 4 t 15 C for 3 min with vrious grining onitions ; () without grining, grining time for () 5, () 1 n () 2 h Surfe res mesure y BET surfe re nlysis re shown in Figure 7. Surfe re of silver power from this proess is in rnge of m 2 /g. It ws foun tht surfe re strongly epens on the prtile size rther thn

5 Preprtion of Ultrfine Silver Power Using Glyerol s Reuing Agent 5 silver luster. Therefore high surfe re with more thn 2 m 2 /g n e hieve in the speimens without grining in whih smll verge prtile size exists (Figure 5 ), wheres the lower surfe re resulte from the lrge prtile size. Apprent ensity ws mesure in the rnge of g/m 3 Surfe re (m 2 /g) Figure 7. Shows liner tren of reltionship etween verge size of silver prtiles n surfe re mesure y BET metho Conlusions Averge Prtile size 4 (nm) In onlusion, the synthesis of very fine silver power y the retion of silver lkoxie n glyerol were hieve. The size of preursor, silver sulfte, n e suessfully reue y ll mill grining tehnique. When using milling time of 2 h, silver sulfte size ws reue from 4.35 to.81 mirons. Stirring silver lkoxie uring glyerol reution is essentil for voiing the gglomertion of prtiles whih les to unexpetely lrge silver lusters. The silver powers in this tehnique hve f rystl struture n n hve proess yiel of out %. The verge prtile size proue from silver sulfte without grining hs een foun to e smller thn 1 nm n lso epens on retion temperture n holing time. 2. Khnn, P.K. n Suro, V.V.V.S. 23. Nnosize silver power vi reution of silver nitrte y soium formlehyesulfoxylte in ii ph meium. Mter. Lett. 57(15) : Soni, I., Goi, D.V. n Mtijevi, E. 23. Preprtion of highly onentrte stle ispersions of uniform silver nnoprtiles. J. Colloi Interfe Si. 26 : Sinh, A. n Shrm, B.P. 25. Preprtion of silver power through glyerol proess. Bull. Mter.Si. 28(3) : Klr, E.R Power Metllurgy. Mterils Prk, OH : ASM Interntion. 9 th e. Vol Li, Y., Dun, X., Qin, Y., Yng, L. n Lio, H Dun.Xingfeng Nnorystlline silver prtiles: synthesis, gglomertion, n sputtering inue y eletron em. J. Colloi Interfe Si. 29 : Cullity, B. D Elements of X-Ry iffrtion Reing, Mss. : Aison Wesley Pu. Co. Surfe re ws mesure in the rnge of m 2 /g. n epene on the verge prtile size of silver power proue. Referenes 1. Nersisyn, H.H., Lee, J.H. n Son, H.T. 23. A new n effetive hemil reution metho for preprtion of nnosize silver power n olloi ispersion. Mter. Res. Bull. 38(6) :