Scalable gas-phase processes to create nanostructured particles

Particuology 8(2010)572-577Contents lists available at Science DirectPARTICUOLOGYParticuologyELSEVIERjournalhomepagewww.elsevier.com/locate/particScalable gas-phase processes to create nanostructured particlesJ Ruud van Ommen a, Caner U. Yurteria, Naoko Ellis, Erik M. Kelder aing, Julianalaan 136, 2628 BL Delft, The Nethb University of British Columbia, Department of Chemical and Biological Engineering, 2360 East Mall, Vancouver, B. C, Canada V6T 1Z3ARTICLE IN FOABSTRACTThe properties of nanoparticles are often different from those of larger grains of the same solid material25May201025Juy2010because of their very large specific surface area. This enables many novel applications, but properties suchIs agglomeration can also hinder their potential use. By creating nanostructured particles one can takeptimum benefit from the desired properties while minimizing the adverse effects. We aim at developingigh-precision routes for scalable production of nanostructured particles. Two gas-phase synthesis routesNanoparticlesNanocomposite materialare explored. The first one- covering nanoparticles with a continuous layer- is carried out using atomiclayer deposition in a fluidized bed. Through fluidization the full surface area of the nanoparticles becomesvailable. With this process, particles can be coated with an ultra-thin film of constant and well-tunableParticle coatingthickness For the second route -attaching nanoparticles to larger particles-a novel approach usingtomic layer depositionwith one potrI-Core-shell particlesTheir charge prevents agglomeration, while it enhances efficient deposition at the surface of the hostElectrohydrodynamic atomizationparticle. While the proposed processes offer good potential for scale-up further work is needed to realizeElectrostatic forcesrge-scale processes.Fluidizationo 2010 Chinese Society of Particuology and Institute of Process engineering, Chinese Academy ofSciences. Published by Elsevier B V. All rights reservedIntroductionng cathode material for Li-ion batteries, but unstable because ofthe dissolution of transition metal ions in an electrolyte. this canIn the past decade, interest in nanoparticles has been strongly be alleviated by forming an Al2 O3 layer of a few atoms thick onincreasing. As the size of particles becomes smaller, i.e, down the surface of LiMn2 O4(Beetstra, Lafont, Nijenhuis, Kelder, vanto the nano-scale, the surface area per unit volume substantially Ommen, 2009). For these examples to be applied in practice, quanincreases, thus dramatically changing the particle properties. This tities of coated nanostructured particles in the kg to tonne scalemay result in unique added value to the particulate materials will be neededbecause of their specific chemical, electro-magnetic, optical orCurrently, there are few examples of nanoparticles producedother physical properties. However, certain properties that are typ- on a large scale, e.g., titania and carbon black. More sophisticatedical for nanoparticles can make it challenging during production nanostructured particles are still typically produced in very smalland application (Liu Bell, 2006). For example, the high sur- quantities for research purposes. Most research in this field isface energy of nanoparticles leads to quick agglomeration, which devoted to the specific properties of nanostructured particles promakes it difficult to disperse. By smart design of the nanoparti- duced in small scale, and not to scalable production processes forles and the processes to manufacture them, these challenges could nanostructured particles. Furthermore, many synthesis approachesbe overcome. For example, nanoparticles of active pharmaceutical for nanostructured particles are carried out in the liquid phaseingredients are in principle very effective but hard to transport partly because of historical reasons: many more chemists areinto the lungs for treatment of respiratory diseases. Deposiresearching nanoparticles, and they tend to work in the liquidthem on micron-sized carrier particles can facilitate the disper- phase. Prof Kwauk(2004)clearly pointed out how the convenand delivery of nanoparticles to targeted areas(Islam Gladki, tional chemical industry has benefited from the introduction of2008). On the other hand, nanoparticles of LiMn2 O4 are a promis- engineering concepts such as unit operations and transport phenomena. We believe that chemical engineers can contribute in alar manner totion of nanostructi中国煤化工 it is advantageouss Corresponding author. Fax: +31 15 2785006E-mail address: j r, vanommen@tudelft nl (R van Ommen)to look beyond tICNMHGase approach for674-2001/s- see front matter o 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B V. All rights reserveddoi:10.1016/ 1. partic.2010.07.010J.R. van Ommen et al. Particuology 8 (2010)572-577573anoparticle production Gas phase methods offer inherent advan- individually, but fluidized as large, very porous, fractal structuredages such as the absence of solvent waste, the feasibility of agglomerates due to the large cohesive forces between them(see,continuous processing as opposed to batch processing in the liquid for example, Chaouki, Chavarie, Klvana, Pajonk, 1985: Jungphase, a better potential for scaling-up, and the versatility of these Gidaspow, 2002; Wang, Gu, Wei,& Wu, 2002; Wang, Kwauk, Liprocesses with respect to particle material and size and structure 1998). During fluidization of nanopowders, problems such as bub-(Samyel-Shall& Schmidt-Ott, 2006). In this paper, we will give two bling, channelling, clustering, and elutriation of particles are oftenexamples of gas phase production routes for nanostructuredencountered, which disrupt good dispersion of the powder in thecles that can be scaled-up to produce large volumes without loosing gas phase and lead to appreciable gas bypassing. Various assistcontrol of particle specifications.ing remedial methods have been developed to overcome theseproblems and enhance the fluidization of nanopowders(Quevedo,2. Atomic layer deposition in a fluidized-bed reactorOmosebi, Pfeffer, 2010: van Ommen Pfeffer, 2010). In this studywe have used vibration to enhance fluidizationA common technique for gas-phase coating objects withIn the semi-conductor industry, ALD is typically carried outlayer is chemical vapour deposition(CVD). In a typical CVD pro- under vacuum to enhance the removal of non-reacted precursorsess the subsed toore gaseous precursors, and gaseous by-products. Typically Weimer and co-workers (e.gwhich react on a surface to produce the desired film. CVD is com- Ferguson et al., 2000; Hakim et al., 2005)applied ald to particles atmonly used in the semiconductor industry but can also be used low pressure, 100 Pa. However, we recently showed that ALd ofto produce coated particles, e.g., noble metal catalyst particles fluidized particles can also be carried out at atmospheric pressureand layered luminescent pigments(Czok Werther, 2006). Since (Beetstra, Nijenhuis, Kelder, van Ommen, 2007a, 2007b)whichdifferent chemical reactants coexist in the gas phase during the simplifies the fluidization of the particles and facilitates processCVD reaction, homogeneous reactions can take place that form scale upnanoparticles contaminating the product. Moreover, truly uniformWhile continuous coating of nanoparticles can be used forind conformal films on individual nanoparticles have not been wide range of applications (e.g, catalysis or imaging), we firstachieved(hakim, Blackson, George, Weimer, 2005aimed at the production of nanoparticulate cathode material for LiInstead of CVD, atomic layer deposition(ald)can provide par- ion batteries. Use of nanoparticles increases the effffective capacitycles with an ultra-thin, uniform layer This technique is different of batteries and reduces the charging time through reduction of thefrom CVD in that the chemistry is split into two half-reactions: the diffusion length. We have used LiMnO2 nanoparticles(100 nm)different reactant gases are fed to the sample consecutively rather supplied by Erachem Comilog(St-Ghislain, Belgium). The reactorthan simultaneously For example, for an alumina coating process, consisted of a 26 mm internal diameter, 500 mm long glass tubea precursor such as tri-methyl-aluminium(TMA) binding to the that was filled with 100-120 g of particles. The reactor was placedchemisorption in step(a)reacts with an oxidiser such on a shaker driven by two vibromotors that producedas water in step(B)(see Fig. 1). A simplified version of the reaction tude vibration at adjustable frequency to assist fluidization. For thescheme is( Puurunen, 2005):experimental runs reported here, the vibration frequency was set(A)IIAl-OH+Al(CH3 )3()-|Al-0-Al(CH3)+CHa(g)to 45 Hz. The nitrogen flow, controlled through the reactant bub(B)|A-CH3A-CH3+H2O(g)→‖Al-OH+CH4(g)(1) blers, was set to 0.5 L/min; in some experiments this was dilutedwith a secondary flow of nitrogen to a total flow of 1.0 L/min. thewhere ll denotes the solid surface. The number of times the(A)-(B) gas entering the reactor was preheated in an inline heater to aroundcycle is repeated determines the thickness of the coating, resulting 80 C; the reactor temperature was kept at 160 using an infraredin full control over the layer thickness at the atomic levellamp Effluent gases from the reactor were led through a double setAtomic layer deposition can be applied to a wide range of of gas washers filled with mineral oil. The streams containing TMAparticles sizes(10 nm-500 um)and materials. Weimer and co- and streams containing water were led through separate gas washworkers(e.g, Ferguson, Weimer, George 2000 Hakim et al., ers. Any TMA absorbed in the gas washers was neutralised after the2005)showed that applying atomic layer deposition( ald) to par- experiment. The effluent from the gas washers was filtered usingticles is best carried out when these particles are fluidized, i.e., Pall Kleenpak pharmaceutical-grade sterilizing filters to capturesuspended in an upward gas stream, to ensure good gas-solids con- elutriatedat the outlet was atmospherictacting. While fluidization is widely applied to disperse and processPresently, the drawback of using materials such as LiMn2 04 forparticles on the micron-scale it seems counterintuitive to apply it Li-ion batteries is that they suffer from degradation in the chemicalto nanoparticles. It is, however, possible, since they are not fluidized environment of the battery as Mn-ions dissolve in the electrolyteSince this is a surface related process, the problem increases whennanoparticles are used as well with the presence of high voltagesTherefore, the surface of LiMn2 O4 was coated with an inert layer(in this case Al2O3)that prevents dissolution of Mn-ions but does@not influence the electrochemical behaviour of the battery that isthe Li-ions should be able to diffuse through the layerFig 2 shows transmission electron microscopy (TEM)images ofthe coated and uncoated material. The crystalline surfaces in theseimages are the LiMn2 O4 base particles. Coatings formed by aLdare generally amorphous, and are therefore more diffuse in theimages. A coating cannot always be distinguished in the images.art nf tim. (d)seems to disappeartowards the中国煤化工was not fully hetion of theCNMHG the lattice orientaFig 1. Schematic representation of ALD half reactions: (1)chemisorption of precurto adsorb on certainsor(e.g, tri-methyl-aluminium) at substrate surface and(2)reaction of adsorbedlattice faces of the spinel material. Alternatively the treatment ofspecies with second reactant(e.g, water)the particles after the process may also break up some agglomerJ.R. van Ommen et al. Particuology 8(2010 572-577a20 nm100nmd0 nm5 nm20 nmFig. 2. TEM photos of coated and uncoated LiMn2 O4 particles: (a)uncoated material-overview: (b)uncoated material; (c)coated after 5 ALD cycles and(d)coated after 28ALD cycles.ates and therefore expose non-coated particle surfaces (Beetstra et 3. Electrospray deposition of nanoparticles on hostaL., 2009). Although a high surface coverage is attractive to obtain particles100% coverage is not necessary to lead to a much better batteryperformance in terms of degradationThe second route to fabricate nanostructured particles we willTo determine whether or not primary particles are coated rather discuss is the deposition of nanoparticles(guest particles )on largerthan the agglomerates as a whole, we measured the surface area particles(host particles), e.g., for transportation, catalytic activ-of the particles before and after coating, using the bet adsorption ity, or as biological contact points. This is referred to as discretemethod, as shown in Table 1. The surface area decreases slightly, coating(Pfeffer, Dave, Wei, Ramlakhan, 2001: see Fig 3). Mostand the effective particle diameter increases from 7.3 x 102 to processes currently used in the upcoming field of discrete coating1.1 x 10nm. If the agglomerates are coated as a whole, the effec- use mechanical forces in order to bring the nanoparticles in contive particle diameter of the coated material would be close to the tact with the micron-sized particles( pearnchob Bodmeier, 2003agglomerate size, around 30 um. The decrease of the total surface Pfeffer et al, 2001). In order to achieve better control over discretearea is due to some of the smaller gaps between grains getting coating, we have developed a method using electrostatic forces tofilled with alumina As can be seen in Fig. 2(a), some of the primary bring guest and host particles into contact. This has the advantageparticles are in close proximity. With several ALD-cycles, they can of the coating being less dependent on the stochastic mixing of thebe ' glued together, resulting in the observed decrease of surface particles, thus easier to optimizearea. However, the majority of the particles are coated as individualparticles by the processDiscreteTable 1ated and uncoated particles, determined by BEt adsorptionGuests Mechanical coatingSurface area(m2/g)Effective particle diameter(nm中国煤化工19○THCNMHG82×11.593×102Fig 3. Schematic of discrete coatingAdapted from Pfeffer et al. (2001 ).J.R. van Ommen et al /Particuology 8(2010)572-577To charge and disperse the nanoparticles, we have usedNanosuspensionlectrohydrodynamic atomization(EHDA), also called electrospraying. Along with applications in mass spectrometry, theHDA is receiving much attention as a potential source for pro-luction of structured micro- and nano-materials that have avariety of applications in medicine, biology, chemistry and elec-tronics. Furthermore, the electrospraying of nanoparticle ladenElectrosprayingquids resolves the apparent problem of effectively dispersingthe nanoparticles Electrospraying of such suspension generates aHost particlesParticle feederpray of charged droplets that are seeded with nanoparticles. thus63。6ooEHDA offers a solution for dispersing and depositing nanoparticleson microparticlesa is a process in which a liquid jet breaks up into dropletsunder the influence of electrical forces(Cloupeau Prunet-FochParticle collection bin1994; Grace Marijnissen, 1994). A liquid is pumped throughnozzle at a low flow rate (uL/h to mL/ h). An electric field is appliedFig 4. Schematic of the grounded moving target set-up for controlled depositing ofnanoparticles on host particles, The particle feeder provides charged host particlesover the liquid by applying a potential difference between the noz- Note that the host particles are not drawn to scalezle and a counter electrode. when the electric strethe surface tension stresses, the emerging liquid meniscus fromthe tip of the nozzle is transformed into a conical shape. From the Fig 4, and the falling curtain method. In the GMT method, a continu-cone apex, ajet emerges which breaks up into quasi-monodisperse ous deposition method, the coating level is controlled by changingdroplets Unipolarity of the droplets prevents their coagulation and the residence time of the host particles in the spraying zone viadispersion is enhanced. Recently, the application of electrospraying conveyor speed and changing the concentration of the suspenof suspensions of nanoparticles has been demonstrated (Suh, Han, sion In the preliminary experiments, three types of nanoparticleOkuyama, Choi, 2005), generating a spray of charged nanopar- deposits were identified: single, in groups, and in agglomerates(seeicle laden droplets. The utilization of a volatile liquid leads to fig. 5). The latter type is presumably explained by the deposition ofits fast evaporation. Thus the droplets shrink, and at some crit- droplets with a high concentration of nanoparticles, or by agglomerates already present in the suspension used. The efficiency andRayleigh charge limit, which is reached when the mutual repulsion homogeneity of the obtained coating have been investigated withof electric charges at the surface exceeds the confining force of sur. techniques such as BET surface analysis, fluorescence microscopyface tension. This process repeats itself until droplets are formed and scanning electron microscopywhich contain one or a few nanoparticles, depending on their ini-tial concentration in the suspension. Eventually, when the liquid ing the particle feeder / charger out of a material, which is far awayphase is completely evaporated, a spray of charged nanoparticles removed from the host particle in the tribo-series, e.g, for glassEHDA leads to the formation of unipolar chargeehost particle, the particle feeder is made out of Teflon. However,ed suspensions charging the host particles too high causes particles to stick on theof guest nanoparticles, while host particles can be charged with feeder making it difficult to handle to the conveyor for coatingopposite polarity by means of tribocharging, corona, or induc- The falling curtain set up, on the other hand, omits the contact oftive charging. When these particles are brought into contact in an particles with the conveyor surface, while reducing the particle resappropriate way, the mutual electrostatic attraction force between idence time. applying multiple electrosprays as well as applying ahe negative and positive charges will cause a coating to be counter air flow increases the residence time of the particles in thedeposited on the surface Interaction can be realized in two ways: spray zone and thus enhances targeting of the nanoparticles on thehost particles can be encapsulated with a polymer and nanopalhost particles. This can lead to higher surface coverage, similar toticles; or nanoparticles can be discretely deposited on the surface those obtained with stationary host particles(see Fig. 6)of the host particles. We will focus on the latter case, in whichfast evaporating nanoparticle suspensions are sprayed to deposit auniform coating. Depending on the initial nanoparticle concentration and size of electrospray formed droplets, single nanoparticlesor nanoparticle agglomerates will be deposited to the surface. Formost applications, the deposition of single nanoparticles is pre-Agglomeratered. We apply tribocharging (or electrostatic charging to givhost particles the opposite polarity. For example, using a Tefloncontainer, alumina particles can be provided with a relatively highnet positive charge. While the charge obtained by tribochargingmuch lower than that by electrospraying, some preliminaryGroexperiments and simulations we performed showed an unexpectedstrong effect of tribocharging(Dabkowski, van Ommen, YurterHochhaus, Marijnissen, 2007). By subsequent contacting of guestand host particles in an appropriate manner the electric attractionSingleforces will bring the host and guest particles into contact and vander Waals forces will effectuate the coatingWe have studied two possibilities for mutually interactingoppositely charged particles in order to deposit nanoparticles onFig. 5. SEM picture of 65YH中国煤化工500mmCNMHbe named as thetyrene particles deposited on a 165 um almina particle. Three different deposition types are distinguished: singles, groupsing target(GMT )method(Dabkowski et al., 2007), as depicted in and agglomeratesJ.R. van OmmenParticuology 8(2010)572-572010), advanced cathode material for Li-ion batteries(Beetstra et2009). For these applications, large quantities of coated materialThe electrospray deposition method is currently carried out atle gram scale. As a first step, we foresee this method suitablefor pharmaceutical applications, i.e scale-up to the kg range tobe sufficient as the first target. This will require both changes tothe charging of the host particles and the electrospraying of theguest particles. Recently, Ellis, Yurteri, and van Ommen(2010)showed a novel concept of charging the host particles in a flu2idized bed, and subsequently entraining them out of the bed, afterwhich the nanoparticles can be deposited onto the charged hostparticles. To be able to coat a larger flow of host particles and/ orobtain a larger surface coverage, it will be essential to use a configFig. 6. SEM image of 500 nm polystyrene particles deposited with electrospraying uration with multiple electrosprays. Providing a uniform electricn a falling flow of 200 um glass beadsfield to each nozzle and a uniform flow rate is essential for getting uniform droplets from an outscaled electrospray assembly4. OutlookArnanthigo, Yurteri, Marijnissen, and Schmidt-Ott(2010)recentlydemonstrated a nozzle assembly in which the nozzles are arrangedDue to their unique properties, nanoparticles are finding in a close circle, so that the electric field situations are identical forincreasing applications in daily life and industrial processes. We each nozzlehave successfully demonstrated two techniques for producing suchWe have limited ourselves in this brief paper to just two methnanostructured particles: atomic layer deposition(Ald)in a flu- ods we are currently working on. However, many more promisingidized bed to provide nanoparticles with a continuous film; and approaches for gas phase production of nanostructured particlesdeposition of nanoparticles on larger host particles by electrostatic are being investigated worldwide. Molecular layer deposition isforces, electrohdrodynamic atomization(EHDA). Both techniques a technique related to ALD: with this coating technique organichave the advantage that they can be applied to a wide range of layers instead of inorganic layers are deposited(liang, King, Li,materials, both concerning the core particle and the coating mate- George, Weimer, 2009). Several authors have been using plasmaial aLd can be used to deposit a wide range of metal oxides, pure enhanced chemical vapour deposition to provide micron-sizedmetals, and other inorganic materials(Puurunen, 2005 ) Also with and nanoparticles with a very thin layer ung, Park, Park, Kimelectrospray deposition, a wide range of materials can be deposited. 2004; Sanchez et al., 2001; Spilmann, Sonnenfeld, von rohile have recently demonstrated that not only nanoparticles but 2006: van Ommen, Abadjieva, Creyghton, 2010), although of thealso proteins can be deposited on carrier particles in this way(van listed papers only Spilmann et al, coated nanoparticles. AnotherOmmen, Tavares Cardoso, Talebi, Yurteri, 2010)successful technique to make nanostructured particles ofBoth ALd and electrospray deposition are in principle fit to be compositions in the gas phase is flame spray pyrolysis(madlerscaled up. However, there are some hurdles to overcome before Kammler, Mueller, Pratsinis, 2002: Teleki, Heine, Krumeichlarge quantities can be processed. aLD has already been demon- Akhtar, Pratsinis, 2008). Esmaeili, Chaouki, and Dubois(2009)strated to be able to produce particles on the kg scale. Recently used a fluidized-bed reactor for encapsulating nanoparticles bySpencer, King, van Ommen, and Weimer (2009) showed that few nm of polyethylene using Ziegler-Natta catalysts. Chen, Yang,particle ALD can be scaled up to 150 mm; there is no clear limi- Dave, and Pfeffer(2009 )used dry powder coating carried out in atation to further increase of this diameter. However, in order to magnetically assisted impaction coater to improve the flowabilityobtain smooth fluidization behaviour for a wide range of mate- of 15 um cornstarch by coating it with 7 nm silica nanoparticlesrials, assistance methods are needed. Recently, Quevedo et al. An alternative approach is to employ plasticizer-electrostatic(2010)demonstrated that adding a secondary flow in the form of a heat-dry-coating to improve the flowability of various powdershigh-velocity jet produced by one or more micronozzles pointing(Luo, Zhu, Ma, Zhang, 2008). These are just a few examtance method They showed that such a micro-jet is effective in developments concerning gas-phase processes to create nanosimproving fluidization, simple to use, does not require expensive tructured particles are taking place, yielding a wide range of novelequipment or adding foreign materials to the bed and can be used productsto mix and blend different species of nano-particles on the nano-scale to form nano-composites Quevedo et al. (2010)also mademore insight into the mechanism of the micro-jet is needy but Referencesa first step towards scale-up(from a 76 to a 127 cm column).effective scale-up to much larger diameters(van Ommen, King,Yurteri, C, Marijnissen, ., Schmidt-Ott, A(2010, April). Immulti-electrospray unit with circular symmetry In G Meesters, T VWeimer, Pfeffer, van Wachem, 2010). Moreover, the optimum&C. Hauser-Vollrath(Eds ) Proceedings of the sixth world congress oroperating pressure needs further research work. For the ald chemistry, a lower pressure is more favourable to enhance the removalBeetstra, R, Lafont, U, Nijenhuis, ], Kelder, E M,& van Ommen, J.R. (2009).Atmo-of non-reacted precursors and gaseous by-products. On the otherpheric pressure process for coating particles using atomic layer depositemical Vapour Deposition, 15, 227-233hand, atmospheric operation is easier concerning the hydrodynam- Beetstra, R Nijenhuis, J, Kelder. E M,& van Ommen, J. R (2007a). Thin coatings toicS Scaling-up particle ald to the tonne range seems feasible. Thisreduce degradation of cathode nano-particles in Li-ion batteries. In C.R. KleijnEd.). 16th etis attractive, since the method is pre-eminently suited for produc中国煤化工on- ook of extendeing various materials that can be used in energy conversion and Beetstra, R, Nijenhuistorage, e.g., quantum-dots for third generation photo-voltaic cellsCNMHGonibeer et al., 2008), hydrogen storage in coated nanoparticlessitionIn F Berruti, X Bi, &T Pugsley(Eds ) Proceedings of the twelfth engineerinfoundation conference on fluidization-New horizons in fluidization engineeringof light metal alloys( Krishnan, Kooi, Palasantzas, Pivak, Dam(pp 369-376). Berkeley: Berkeley Electronic Press.J.R. van Ommen et al. Particuology 8 (2010)572-577577Chaouki. ], Chavarie, C, Klvana, D, Pajonk, G(1985). Effect of interparticle forces Madler, L, Kammler, H K, Mueller, R, Pratsinis, S E(2002). Controlled synthesison the hydrodynamic behaviour of fluidized aerogels Powder Technology, 43,ed particles by flame spray pyrolysis. Journal of Aerosol Sci117-12533,369389Chen, Y Yang, Dave, R N,& Pfeffer, R(2009). Granulation of cohesive Geldart Pearnchob, N,& Bodmeier, R(2003). Coating of pellets with micronized ethylPharmaceutics. 268. 1Conibeer, G, Green, M, Cho, E.-C, KOnig, D117,40-67Solid films.516,6748-6756for the trimethylter pology,162,100-110.Samyel-Shall, M.,& Schmidt-Ott, A (2006). Special issue: Nanoparticles from theDabkowski, M. F, van Ommen, J. R, Yurteri, C U, Hochhaus, G,& Marijnissen. Jvapor phase synthesis with chemical and biochemical applications -Guest ecC M. (2007). The coating of particles with nanoparticles by means of electro-torial. Journal of Nanoparticle Research, 8, 299-300static forces. In C. Schreglmann, & W. Peukert(Eds. Partec 2007-CDngs Sanchez, L, Flamant, G, Gauthier, D, Flamand, R Badie. J M,& Mazza, G (2001).Ellis, N, Yurteri, C U,& van Ommen, ]. R (2010). Development of a continuousPowder Technology, 120, 134-140nanoparticle coating with electrospraying. In S D Kim, Y Kan, J K Lee, &Y C. Spencer, J.A., King, D M, van Ommen, J.R,& Weimer, A wSeo(eds Fluidization XIll-New paradigm in fluidization engineering. New York:re dependence of atomic layer depositionfluidized bed reactor. Paper presented at the AlChE annual meeting 2009,Esmaeili, B, Chaouki, J ,& Duboismerization compounding in aenfeld, A,& von Rohr, Ph R(2006, May). Flowability modificaNSTI nanotechnology conference and trade show-NSTI Nanotech 2006 tecproceedings, Vol 1 Massachusetts, USA, (pp 315-31795-104uh, J, Han, B, Okuyama, K,& Choi, M.(2005). Highly charging of nanoparticleC M. (1994). A review of liquid atonelectricaray of nanoparticle suspension. Journal of Colloid and Interfacemeans. Journal of Aerosol Science, 25, 1005-1019cience,287,135-140.Hakim, L F, Blackson, J, George, S M,& WeimerTeleki, A, Heine, M. C, Krumeich, F, Akhtar, M.K.& Pratsinis, S. E. (2008). In sitdual silica nanoparticles byic layer deposition in a flating of flame-made TiO2 particles with nanothin SiO2 films. Langmuir, 24,Chemical vapor Depositi2553-12558Islam, N,& Gladki, E.(2008). Dry powder inhalers (DPIs)A review ovan Ommen, ]R Abadjieva, E. Creyghton, Y L M (2010). Plasma-enhanced chemdevice reliability and innovation. International Journal of pharmaceutics, 360,in an atmosphericd bed In S D. Kim」K.LeJung J.,& Gidaspow, D (2002). Fluidization of nano-size particles. Journal of nanoparngineering(pp, 495-502) New York: Engineering Conferences Internationalvan Ommen, J.R., King, D M, Weimer, A, Pfeffer, R. van Wachem, B G M. (2010)Jung, S H, Park, S M, Park, S H& Kim, S D (2004) Surface modification of fineriments and modelling of micro-jet assisted fluidization of nanoparticles.In S D. Kim, Y Kan, J K Lee, &Y C Seo(Eds ) Fluidization XIll-New paradigmin fluidization engineering(pp 479-486) New York: Engineering ConferencesKrishnan, G. Kooi, B ], Palasantzas, G. Pivak, Y, Dam, B (2010). Thermal stabilityInternationale magnesium nanoparticles. Journal of Applied Physics, 107, 053504. van Ommen, J.R., Pfeffer, R (2010). Fluidization of nad applications. In S D. Kim, Y. Kan. .KLiang, X, King, D M, Li, P, George, S.M.,& Weimer, A W (2009).Nanocoating hybridpolymer films on large quantities of cohesive nanoparticles by molecular layer van Ommen. J.R, Tavares Cardoso, M. A Talebi, M.& Yurteri, C U (2010).activation by electrospraying for dryLiu, G,& Bell, T (2006, April). Nanoparticle application by dry palfer, &C. Hauser-Vollrath( Eds ) Proceedings of the sixth world congress onLuo, Y. Zhu, J, Ma. Y,& Zhang, H (2008). Dry coating, a novelg technology forSioz nanoparticles Powder Technology, 124, 152-159olid pharmaceutical dosage forms. International Journal of pharmaceutics, 358, Wang Z, Kwauk, M., &Li, H (1998). Fluidization of fine particles. Chemical Engineer-6-22.ing Science, 53. 377-395中国煤化工CNMHG