Effects of Silica Nanoparticles and Silica-Zirconia...

Research ArticleEffects of Silica Nanoparticles and Silica-ZirconiaNanoclusters on Tribological Properties of DentalResin Composites

Henry A Rodrıguez 12 and Herley Casanova1

1Grupo de Coloides Instituto de Quımica Universidad de Antioquia Medellın Colombia2New Stetic SA Guarne Colombia

Correspondence should be addressed to Henry A Rodrıguez hrodrigueznewsteticcom

Received 5 August 2018 Revised 18 October 2018 Accepted 28 October 2018 Published 21 November 2018

Academic Editor Marco Rossi

Copyright copy 2018 Henry A Rodrıguez and Herley Casanova )is is an open access article distributed under the CreativeCommons Attribution License which permits unrestricted use distribution and reproduction in any medium provided theoriginal work is properly cited

Roughness and hardness are among the most important variables in the wear (resistance) performance of dental resin compositesIn this study silica nanoparticles and nanoclusters of silica and silica-zirconia nanoparticles were evaluated for use as re-inforcement agents in dental resin composites Nanoclusters with spherical morphology were obtained from aqueous dispersionsof nanoparticles by spray drying Roughness was measured through atomic force microscopy (AFM) while nanohardness wasevaluated by nanoindentation )e roughness values obtained with silica nanoparticles were lower (226 plusmn 66 nm) than thoseobtained with silica and silica-zirconia nanoclusters (1381 plusmn 366 nm 1162 plusmn 322 nm resp) while the hardness values of allcomposites were similar (nanoparticles 024 plusmn 001GPa silica nanoclusters 025 plusmn 004GPa and silica-zirconia nanoclusters

022 plusmn 002GPa) Based on this study it can be established that particle size is a determining factor in the roughness of the finalmaterial while the key variable for nanohardness was the concentration of the reinforcement materials

1 Introduction

Composite dental materials are widely used to repair an-terior and posterior teeth due to their ability to replicatenatural dental structure workability mechanical propertiesand clinical performance [1ndash3] Wear resistance is an im-portant property in the performance of dental compositesbecause lack of wear resistance will produce an excessivereduction in structure resulting in the loss of posterior toothsupport vertical dimension of occlusion masticatory effi-ciency and esthetics as well as alterations in the functionalpath of masticatory movement fatigue of masticatorymuscles and faulty tooth relationship [4] Wear (resistance)performance of dental resin composites is affected byroughness and hardness while roughness also influencesaesthetic appearance discoloration plaque accumulationthe appearance of secondary caries gum inflammation andwear of opposing and adjacent teeth [5ndash8] and hardness

defined as how resistant the material is to penetration can beused to predict wear resistance and the tendency of thematerial to erode the opposing tooth or material [7 9 10]

It is accepted that roughness being caused by the loss ofparticles is reduced when the particle size is decreased [11]Finer particles for a fixed-volume-fraction have been shownto result in decreased interparticle spacing and therebyreduced wear of dental composites [12] )is indicates thatthere is a relationship between roughness and wear re-sistance lower roughness being related with an increase inwear resistance Meanwhile wear resistance tends to in-crease with increasing hardness but quantitative relation-ships between wear resistance and hardness have not beenestablished with some studies finding a direct correlationand others not [4] )is may be due to the fact that hardnessis an intrinsic property of the material which depends onlyon composition and microstructure while abrasion re-sistance is not an intrinsic property since it may also depend

HindawiJournal of NanotechnologyVolume 2018 Article ID 7589051 10 pageshttpsdoiorg10115520187589051

on variables such as the testing technique used the abrasiveproperties and environmental conditions [13] )ereforehardness is a parameter that is related to wear resistance butdue to other variables that affect it there is not a directrelationship in all cases In general the literature reports thathardness increases with the quantity of filling [7 10 14ndash16]However it is not necessarily the case that a larger quantityof filling causes an increase in the hardness of the material orgenerates an increase in wear resistance )is is becausehardness also depends on the type and quantity of thesilanization agent the method of surface modification [17]the dispersion degree of nanoparticles the particle size andthe hardness of the filler particles since harder particlesexhibit higher surface hardness in the composite [18]

As particle size is related to roughness hardness andother properties it is proposed that the use of nanofillers willallow materials to be obtained with better mechanicalproperties such as compression fracture and bending re-sistance [19ndash21] and improved surface properties such asbetter gloss polish and wear resistance [5 6 22ndash24] It isalso proposed that the use of nanoparticles will allow re-duced roughness [6] although other studies have pointed toa lack of evidence supporting this since the difference inmeasuring methods and processes for polishing makes itdifficult to compare them [11] )ere are reports that in-dicate that nanoclusters in spite of having bigger particlesize than individual nanoparticles allow materials to beobtained with improved surface properties such as bettergloss polish and wear resistance [5 6 22ndash24] Nanoclustersare nanoparticle aggregates with controlled size and mor-phology obtained prior to the dispersion process in the resin[25ndash27] One of the methodologies used to obtain theseaggregates is spray drying using nanoparticle dispersions[28ndash30] Examples of dental materials that use nanoparticleaggregates are Filtek Supreme Body resins and Filtek Su-preme Translucent resin (3M) which use aggregates of silicaand zirconia nanoparticles [23 25] )ese aggregates areapproximately 760 nm in size and are used in thematerials incombination with nonaggregated silica nanoparticles[22 24] Nanoclusters have been proposed as an alternativeto nanoparticles in order to solve problems such as ex-cessive increase in the viscosity of the composite materialbefore it is polymerized [19] and the tendency of nano-particles to agglomerate due to their high surface energypreventing nanomaterials with nonaggregate nanoparticlesbeing obtained [19] With regard to hardness studies reportimproved hardness on the part of microparticles at relativelyhigher concentrations than nanoparticles and high hard-ness values for dental composites reinforced with nano-particles [18] but there is a lack of evidence about differencesin hardness between composites that use nanoparticles ornanoclusters

)e objective of this study is to correlate the properties ofroughness and hardness with the use of nanoparticles andnanoclusters in order to provide information facilitating theuse of reinforcement agents of this nature in dental resincomposites Our hypothesis is that lower roughness is ob-tained with nonaggregate silica nanoparticles than withnanoclusters while hardness is similar in both cases For the

purpose of this study spray drying was used to obtainnanoclusters of silica and silica-zirconia )is kind ofnanoclusters was chosen because they are used in com-mercial dental composites Composites of nonaggregatedsilica nanoparticles silica nanoclusters and silica-zirconiananoclusters were prepared )e roughness of these mate-rials was evaluated by atomic force microscopy (AFM) andtheir nanohardness by nanoindentation

2 Materials and Methods

21 Materials For dental resin composites the followingkind of nanoparticles were used silica in an aqueous dis-persion (20 by weight of nanoparticles) with a pH between2 and 4 brand name SNOWTEXreg ST-OL made by NissanChemical (USA) and zirconia in an aqueous dispersion(30 by weight of nanoparticles) pH 3 brand nameNanoUsereg ZR 30-AL made by Nissan Chemical (USA)Silica nanoparticles were functionalized by methacrylox-ypropyltrimethoxysilane (MPS) (97) (Alfa Aesar)

)e monomers were bisphenol A glycidyl methacrylate(Bis-GMA) (90) bisphenol A polyethylene glycol dietherdimethacrylate (Bis-EMA) (90) urethane dimethylacry-late (UDMA) (90) and triethylene glycol dimethacrylate(TEGDMA) (90) )ese were acquired from Esstech (USA)

Polymerization initiation system was composed by ethyl4-(dimethylamino) benzoate (4EDMAB) (99) provided byAlfa Aesar and (CQ) Camphorquinone (97) provided bySigma Aldrich

22 Methods

221 Characterization of Silica and Zirconia NanoparticlesMorphology of the silica nanoparticles was determinedusing a S4700 scanning electron microscope (Hitachi Ja-pan) An AuPd alloy particle coating of approximately 2 nmthickness was deposited on the sample using a sputteringdevice All the samples were analyzed at a work distance of5mm and a voltage of 150 kV

)e morphology of zirconia particles was determinedusing a 2010LAB6 transmission electron microscope (TEM)(Jeol Japan) For this analysis the dispersion was diluted inethanol After this a drop of each dispersion was depositedin a TEM grid allowing the water and ethanol to evaporate)e samples were analyzed using a voltage of 200 kV

)e ζ potential measurements of the silica and zirconiananoparticles were performed using the light scatteringtechnique for which Zetasizer Nano ZS equipment (Mal-vern Instruments UK) was used Before each measurementthe particle dispersion was diluted using distilled water

222 Functionalization of Silica NanoparticlesFunctionalization of silica nanoparticles was carried out byheating a suspension of silica nanoparticles (20 wt) in thepresence of MPS at 65degC for 30 hours under constantstirring )e weight percent of MPS required for nano-particle silanization was calculated according to the fol-lowing equation [31]

2 Journal of Nanotechnology

X A

w1113874 1113875f (1)

where A is the surface area of the silica in m2g which is763m2g [32] w is the surface coverage by gram of thesilanization agent which for MPS is 2525m2g [31] and f isthe quantity of silica in grams Taking into account thesevalues to cover 1 gram of silica (f) 003 g of silanizationagent or 3 by weight with respect to the weight of the silicais required In order to have an excess of functionalizing agentand thereby generate better coverage 4 by weight was usedwith respect to the silica )e nanoparticles functionalizedwere dried at 80degC in a vacuum oven for 24 h and wereanalyzed by infrared spectroscopy in FT-IR Spectrum Oneequipment (Perkin Elmer USA) using the KBr pelletsmethod)e average spectrum reported was obtained from 16scans at a resolution of 4 cmminus1)e thermic degradation of thefunctionalized silica nanoparticles was studied by thermog-ravimetric analysis applying a heating rate of 10degCmin be-tween 30 and 800degC in air )e weight loss was recorded as afunction of time and temperature using TGA Q500 equip-ment (TA Instruments USA)

223 Production of Nanoclusters

(1) Silica Nanoclusters Silica functionalized aqueous dis-persion (20 wt) was dried using a B290 Mini Spray Dryer(Buchi Switzerland) to obtain silica nanoclusters )edrying conditions were air temperature at the entrance of thedryer of 180degC air temperature at the exit of the dryerbetween 70 and 80degC air flow at the nozzle of 600 Lh (50of the nozzle rotameter scale) drying air flow of 30m3h(75 of the dryer scale) and pump speed of 5mLmin (15of maximum speed)

(2) Silica-Zirconia Nanoclusters )e silica-zirconia nano-clusters were obtained using an aqueous dispersion (20 wt)of functionalized silica nanoparticles (obtained as described inSection 222) and an aqueous dispersion (30 wt) of zirconiananoparticles A blend with 83 wt by weight of nano-particles (30 wt were zirconia) was stirred using a paddleagitator set to 600 rpm for 30 minutes before drying )edrying was performed using a B290 dryer (Buchi Suiza) underthe same conditions used to obtained the silica nanoclusters

224 Characterization of Silica and Silica-ZirconiaNanoclusters )e particle size distribution of the nano-clusters was evaluated by static light scattering using Mas-tersizer 2000 equipment (Malvern Instruments UK) and theHydro 2000 accessory Morphology of nanoclusters wasdetermined using a S4700 scanning electron microscope(Hitachi Japan) using the same procedure employed toanalyze silica nanoparticles morphology

225 Nanoparticles and Nanoclusters Dispersion

(1) Dispersion of Silica Nanoparticles To obtain a dispersionof nonaggregated functionalized silica nanoparticles an

aqueous dispersion of said particles (20 wt) was put intocontact with the monomer mix (TEGMAUDMABis-EMABis-GMA 03 07 1 1 respective weight ratios) containing02 CQ and 08 4EDMAB based on the weight of themonomers )e quantity of this mixture was determinedtaking into account the expected concentration of silicananoparticles at the end of the process (ie 30 wt) )emixture was subjected to heating at 50degC and stirring using aBDC 3030 stirrer (Caframo USA) with paddles inclined at45deg working at 350 rpm for 40 minutes then 450 rpm for 10minutes and finally 750 rpm for 23 hours and 10 minutes)is is a variation of a methodology performed in ourlaboratory and previously reported [26] and the difference isthat the system in this investigation used an aqueous phaseand an organic phase while in the previously reportedmethodology only an organic phase was used

(2) Dispersion of Silica and Silica-Zirconia Nanoclusters )edispersions of nanoclusters (30 wt) were obtained by itsmanual dispersion in the monomer blend TEGMAUDMABis-EMABis-GMA 03 07 1 1 respective weight ratioscontaining 02 CQ and 08 4EDMAB based on theweight of the monomers

226 Tribologial Properties

(1) Roughness Test cylinders of 4mm diameter and 2mmthickness were prepared using a metallic mold )e cyl-inders were photopolymerized by overlapping irradiationfor 60 s on the two circular faces using a Sunlite 1275 lightcuring lamp (FEN Dental USA) with a light source of450minus490 nm )e cylinders were then placed on a stainlesssteel metallic disc of 12mm diameter and polished withEcomet III equipment (Buehler USA) using panels em-bedded with a dispersion of diamond particles of 15 6 1and 025 microm

Roughness measurements were performed using a MFP-3D device (Asylum Research USA) )e relative heightsmap was obtained in air atmosphere in intermittent contactmode with a Tap300Al-G-10 reference point (Nano-AndMore USA) with a nominal spring constant of 40Nmand a fundamental resonant frequency of 300 kHz )e scanwas performed in an area of 90 square microns and 4cylinders per sample were used

(2) Nanohardness Test cylinders similar to those used for theroughness analysis were used )e nanoindentation mea-surements were performed with a TI-950 device (HysitronUSA) using a Berkovich tip with a nominal radius of 50 nm)e measurements were taken in air atmosphere at roomtemperature under the load control mode Load and unloadspeeds were 1mNs and 05mNs respectively with pausesof 60 s at a maximum load of 5mN To obtain the exact areafunction of the indenter the system was calibrated using astandard of quartz with an elastic modulus of 73GPa and aPoisson ratio of 017 Two cylinders per sample were ana-lyzed and 6 measurements were taken of each cylinder for atotal of 12 measurements per sample )e data analysis for

Journal of Nanotechnology 3

the determination of the nanohardness was performed usingthe Oliver and Pharr method [33]

23 Statistical Analysis )e results are expressed as themean plusmn standard deviation )e normal distribution of eachdata set was confirmed using the Shapiro-Wilk test )estatistically significant differences between groups of dataregarding the nanohardness and roughness were based onone-way variance test (ANOVA) followed by a post hocTukey test with 95 confidence (ie p 005) )eSTATGRAPHICS centurion 18101 software was used

3 Results and Discussion

31 Characterization of Silica and Zirconia Nanoparticles)e average size of silica nanoparticles according to theproduct technical specification is between 40 and 60 nm)is is consistent with the particle size observed in the SEMmicrograph shown in Figure 1 )e particles are of sphericalmorphology which is as expected for nanoparticles syn-thesized by sol-gel technology given that this is a methodthat allows spherical monodispersed particles to be obtained[34] Spherically shaped particles and a homogenous sizedistribution allow dispersions at high concentrations to beobtained as shape and size homogeneity are factors thatinfluence the viscosity of dispersions [35] )e spheres dueto their shape can generate a kind of lubricating action onthe material allowing it to flow freely and having low impacton viscosity Meanwhile amorphous particles tend to ob-struct the flow thereby generating a greater increase inviscosity [35]

)e colloidal silica particles in SNOWTEX-OL arenegatively charged on their surface according to reports inthe literature [36] )e ζ potential measured was minus54mVwhich added to the fact that silica sols present steric sta-bilization caused by the presence of oligomeric or polymericsilicate species at the interface [36] is indicative of the highstability of the dispersion of these nanoparticles [37] )isstability and nonaggregation of the particles in suspension isa factor which will affect the dispersion grade of the particleswhen dispersed in the monomers blend Dispersion degreeaffects the interaction surface area between the filler and thepolymeric matrix Lower aggregation permits higher surfacearea and interaction between filler and matrix which affectsroughness as particle loss is reduced Uniform dispersion ofnanoparticles provides enough distance between the parti-cles increasing composite hardness [18]

)e zirconia nanoparticles are aggregates of individualnanoparticles of lower size as can be seen in Figures 2(a) and2(b) Moreover they possess amorphous morphology asevidenced in Figure 2(a) )e nanoparticle aggregates arebetween 40 and 100 nm in size according to the producttechnical specification which is corroborated by TEM im-ages )e primary nanoparticles of zirconium dioxide areapproximately 5 to 10 nm in size as shown in Figure 2(b)

)e ζ potential analysis indicates that these aggregateshave a positive surface charge with a value of 43mV )is isdue to the low pH of the system which causes protonation of

the ZrOH groups to ZrOH2+ groups )is value indicatesthat the particles have high electrostatic stability [37]

32 Functionalization of Silica Nanoparticles )e func-tionalization of the silica nanoparticles does not affect theirsize or morphology as shown in Figure 3 where both theshape and size of the nanoparticles are similar to those of thebare nanoparticles

)e FT-IR spectrum of the silica nanoparticles beforeand after being functionalized is shown in Figure 4 )ebonds attributable to the extension vibrations of the CCbonds (around 1630 cmminus1) to the aliphatic CO bonds(around 1700 cmminus1) and to the CminusH bonds (around2950 cmminus1) are due to the presence of MPS as the func-tionalizing agent )ese bonds are not observed in the FT-IRspectrum of the bare silica nanoparticles)ermic analysis ofthe particles functionalized with MPS indicated that thesilanization grade was 15 associated with the weight lossbetween 200 and 600degC Silanization grade affects roughnessand hardness Silanization prevents the loss of surfaceparticles because of the covalent bond between particles andmatrix and hardness depends on the type and quantity ofthe silanization agent as well as the method of surfacemodification [17]

33 Production of Nanoclusters Figure 5 shows the particlesize distribution of the silica and silica-zirconia nanoclustersobtained by spray drying )is shows that the average particlesize of the silica nanoclusters is approximately 45 microm with adistribution varying between 1 and 20 microm while the silica-zirconia nanoclusters have an average size of 20microm withsizes between 02 and 10 microm Hence the size of the silica-zirconia aggregates is approximately half of that obtained forsilica alone Lower size of silica-zirconia nanoclusters is due tothe reduction in the concentration of the silica-zirconiadispersion along with the greater density and molecularweight of zirconium [28 38] )is difference in size will affectroughness as it is accepted that roughness caused by particleloss is reduced when particle size is decreased [11]

In Figure 6 it can be observed that both types ofnanoclusters are of spherical morphology When zooming inon the surface of the silica nanoclusters (Figure 6(b)) arelatively homogenous surface formed by nanoparticles

150kV 54mm times 100k 500nm

Figure 1 SEM micrograph of silica nanoparticles


around 50 nm in size and organized in a hexagonal ar-rangement is observed with the presence of individualparticles not forming an integral part of the nanoclusters)ese results are consistent with the sizes and morphologiesfound in another study [39] where aqueous silica dispersionswere used to obtain aggregates by spray drying

On the surface of the silica-zirconia nanoclusters (Fig-ure 6(d)) the presence of zirconia nanoparticles causes alower regularity of the hexagonal arrangement of the par-ticles due to their migration into the spaces left by the silica

nanoparticles reducing the porosity of the surface In silica-zirconia nanoclusters the opposing surface charge value(silica minus54mV zirconia 43mV) contributed to thehomogenization of the particles when they were mixed andsubsequently subjected to spray drying )is is because thezirconium dioxide particles tend to be surrounded by silicaparticles and there is a low possibility of the zirconiananoparticles encountering one another a phenomenonalso found in other studies [40] )is contributes to thezirconium dioxide nanoparticles being homogenously dis-tributed in the nanocluster )is can be corroborated in theSEM images (Figures 6(c) and 6(d)) where a homogenousdistribution of the zirconia in the nanoclusters can be seen)e homogeneity of zirconia inside nanoclusters will affecttheir behavior )is is because nanoclusters with only zir-conia or within which there is no homogeneity of zirconiamay show different roughness and hardness compared withnanoclusters obtained as zirconia aggregates have a highersize than silica nanoparticles (40ndash100 nm vs 40ndash60 nm resp)and are not functionalized and functionalization and sizebeing factors that affect roughness and hardness

50nm

(a)

20nm

(b)

Figure 2 TEM micrographs of (a) zirconium dioxide nanoparticles and (b) close-up view of zirconium dioxide nanoparticles


Figure 3 SEM micrograph of functionalized silica nanoparticles

4000 3500 3000 2500 2000 1500 1000 500

0

5

10

15

20

25

Tran

smitt

ance

()

Wavenumber (cmndash1)

Functionalized silica

Bare silica

1700 cmndash12950 cmndash1

Figure 4 FTIR analysis of functionalized and bare silicananoparticles

010

2

4

6

8

10

12

Vol

ume (

)

Diameter (microm)

Silica-zirconiaSilica

1 10

Figure 5 Particle size distribution of the nanoclusters


34 Dispersion of Nanoparticles and NanoclustersFigures 7(a) and 7(b) show that silica and silica-zirconiananoclusters had a good dispersion In the AFM imageshown in Figure 7(c) it can be seen that there is also anadequate dispersion of the silica particles in the polymericmatrix at 30 wt since these can be individually observed)is shows how the solvent evaporation technique alongwith the presence of the functionalization agent on thesurface of the particles allows dispersions of nonaggregatedsilica nanoparticles to be obtained and that this conditioncontinues even after polymerization )ese results permitcomparison between different kinds of materials includingboth nonaggregate nanoparticles and nanoclusters sinceaggregation could affect the roughness and hardness

35 Tribological Properties

351 Roughness Figure 8 shows the results of the roughnessanalysis Statistical analysis using the Tukey HSD test in-dicates that the samples with silica nanoparticles are sta-tistically different from those that contain the nanoclusters(plt 005) Roughness is lowest when nonaggregated silicaparticles between 40 and 60 nm in size are used as re-inforcement agent (226 plusmn 66 nm) and highest when thesilica nanoclusters with an average size of 45 microm areused (1381 plusmn 366 nm) )ere is no statistical differencebetween the two types of nanoclusters (pgt 005) the averageroughness value obtained is lower when silica-zirconia

nanoclusters with an average size of 20 microm are used(1162 plusmn 322 nm vs 1381 plusmn 366 nm) )e results thereforeshow that there is a correlation between particle size androughness with lower roughness being obtained at lowerparticle size

Some studies from the literature propose that the size hasa significant effect on surface properties like roughness [11]However other studies posit that there is a lack of evidencefor this statement [11] )is is because there are other factorsaffecting roughness such as the bond of the particles in theaggregates [41] as well as differences in measurementmethodologies and polishing processes that make com-parison between materials difficult [11] since the polishingtechnique affects the final roughness of the material [8 42]In this case the comparison is valid since all the materialswere subjected to the same polishing process and all havethe same percentage of reinforcement material and the samepolymeric matrix without particles aggregation )ereforethe changes can be attributed to the type of inorganic re-inforcement In this regard it is important to consider thatwhen relating the effects of the reinforcement material themechanical and tribological properties of the compositeresins depend on the particle size the structure of thenanoclusters the bondmechanism between the particles andthe polymeric matrix and the nature of the bond betweenthe primary particles in the nanoclusters )is last bondmechanism is responsible for micromechanical deformationbehavior and fracture of structures in nanoclusters espe-cially in the case of spray-dried nanoclusters [41 43] Taking

200kV 52mm times 200k 200μm

(a)


(b)


(c)

Zirconia nanoparticles


(d)

Figure 6 SEM micrographs of (a) silica nanoparticle nanoclusters (b) surface of silica nanoclusters (c) silica-zirconia nanoclusters and(d) surface of silica-zirconia nanoclusters


into account the above inorganic reinforcement of theevaluated materials differs in size morphology and in thestrength of the bond that exists between the reinforcementand the polymeric matrix )e nonaggregated silica particlesbond to the polymeric matrix through chemical linksgenerated by the presence of the functionalizing agent at thesurface )e same type of bond exists between the silicaaggregates and the polymeric matrix However in this casethe specific area available for bonding with the matrix ishigher in nonaggregate silica nanoparticles than in nano-clusters In nanoclusters part of the surface area of thenanoparticles is occupied by the surface interaction betweenthe nanoparticles inside the nanocluster Moreover in thecase of the silica-zirconium dioxide aggregates the presence

of zirconium dioxide negatively affects the bond to thepolymeric matrix as these particles are not functionalized)is could have been an influential factor in the highroughness values obtained with these nanoclusters which inspite of having lower particle size than silica nanoclustershave similar roughness to them For the nanoclusters it isalso necessary to take into account that the bond strengthbetween the nanoparticles is low as there is no chemicalbond between them )is could allow the nanoparticles tobecome detached from the material more easily affecting theroughness to a considerable degree In these cases the lack ofchemical bond between the nanoparticles could be modifiedby submitting the aggregates to sintering with temperatureobtaining a higher level of cross-linking of the particlesleading to an increase in the bond strength and higher ri-gidity [43] )e above may explain why the results found inthis study with nanoclusters are different to those reportedfor Filtek Supreme Body and Filtek Supreme Translucentresins (3M) [5 20] where the aggregates were subjected to asinterization process that caused a chemical bond of theindividual particles [20] allowing lower roughness values tobe obtained as well as improved surface property valuessuch as gloss and wear resistance [5 6 20 24 44]

)erefore in this case the behavior of the material wasdetermined by the large size difference between the non-aggregated silica particles and that of the nanoclusters thelower chemical bond between the particles and the matrixfor the nanoclusters and the lack of chemical union betweenthe nanoparticles of the nanocluster )e results support theuse of nanoparticles to obtain material with lower rough-ness due to the fact that with a lower particle size the surfacealterations caused by the loss of particles are reduced [6])is supports the growing use of nanoparticles in dentalrestoration resins where roughness is an important pa-rameter [6 7] Nanoparticle aggregates can be an alternative

a

Silica nanoparticles Silica nanoclusters Silica-zirconiananoclusters

b

b

0

20

40

60

80

100

120

140

160

180

Roug

hnes

s (nm

)

Figure 8 Roughness of materials reinforced with 30 by weight ofparticles )e letters indicate statistically homogenous groups(Tukey HSD test (pgt 005))

016 micromndash028 microm

x 25

micromy 25 microm

1631 nm100050000ndash500ndash1000

ndash2000

ndash2818ndash2500

ndash1500

(a)


036 microm 030020

005ndash005

ndash020

ndash033

ndash010

x 25 micromy 25 microm

025015010000

ndash015ndash025

(b)

6 nmndash16 nm

x 10

0 microm

y 100 microm

57 nm40

00

ndash40

ndash120ndash100

20

ndash20

ndash60ndash80

ndash140ndash162

(c)

Figure 7 Images obtained by AFM (a) Silica-zirconia nanoclusters (b) silica nanoclusters and (c) nonaggregated silica nanoparticles


option but a chemical union needs to exist between theindividual particles to improve their performance and it isnecessary to ensure a chemical bond of the aggregate to thepolymeric matrix through functionalization

351 Nanohardness Figure 9 shows the results of thenanohardness measurements )e nanohardness values forthe three materials are in the order of 02 to 025 GPa )esemeasurements are within the hardness values obtained forcomposite resins for dental use which according to studiesare from 02 to 16 GPa [10 45] while the hardness value ofnatural tooth enamel is 558 [46] and the values found fordentine are between 05 and 13 GPa )is last value de-pends on the distance from the center of a dentinal tubuleto the place where the measurement is taken being greaterwhere this distance is lower [47]

Figure 9 shows the results of the nanohardness analysisStatistical analysis using the Tukey HSD test indicates thatthere is no significant statistical difference between thesamples (plt 005) )is may be due to the fact that allmaterials have same filler concentration and literaturepostulates that hardness depends on the quantity of filler[9 10 14 25] However other studies postulate that thehardness and other tribological properties are determinednot only by the quantity of filler but also by the type andquantity of silanizing agent as well as the method ofsurface modification of the filler [17 48] )is may beresponsible for the fact that the lowest average hardnessvalue was obtained with materials containing zirconiawhich was not functionalized (022 plusmn 002 GPa vs nano-particles 024 plusmn 001 GPa and silica nanoclusters 025 plusmn004 GPa)

Some studies report that particle size affects hardnessand that microparticles have improved hardness at relativelyhigher concentrations than nanoparticles while dentalcomposites reinforced with nanoparticles display highhardness values [18] )e results of this investigation showno effects on hardness either on the part of particle size orbased on the use of nonaggregate nanoparticles In this casethe filler concentration was the determinant variable relatedto hardness

4 Conclusions

Statistical analysis using the Tukey HSD test indicates thatthe samples with silica nanoparticles are statisticallydifferent to those that contain nanoclusters (plt 005) )eroughness values obtained with silica nanoparticles werelower (226 plusmn 66 nm) than those obtained with silica andsilica-zirconia nanoclusters (1381 plusmn 366 nm and 1162 plusmn322 nm resp) )erefore our hypothesis that lowerroughness is obtained with nonaggregate silica nano-particles was confirmed Based on this investigation it canbe established that particle size is a determining factor inthe roughness of the final material supporting what hasbeen stated in some studies in the literature andredressing the lack of clinical data supporting thisstatement [34] as the methodology used allowed the use

of different types of particles to be compared However inthis regard it should be taken into account that there areother variables that affect roughness such as the bondstrength between the particles that make up the nano-clusters an aspect to consider when seeking to improvethe performance of this kind of reinforcement materials

With regard to nanohardness according to Tukeystatistical analysis there are no significant statistical dif-ferences between the composite materials analyzed(pgt 005) )erefore our hypothesis that hardness issimilar using nonaggregate nanoparticles and nanoclusterswas confirmed (nanoparticles 024 plusmn 001GPa silicananoclusters 025 plusmn 004GPa and silica-zirconia nano-clusters 022 plusmn 002GPa) Although nanohardness can beinfluenced by variables such as functionalization and particlesize the results of this study show that nanohardness wasdetermined by the concentration of the reinforcementmaterials

Data Availability

)e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was carried out in part in the Frederick SeitzMaterials Research Laboratory Center for Microanalysis ofMaterials at the University of Illinois at Urbana-Cham-paign )is work was supported by Colciencias andSumicol SA (Grant 1115-562-38446 Cto 0162-2014)

a


a

a

000

005

010

015

020

025

030

Nan

ohar

dnes

s (G

Pa)

Figure 9 Nanohardness of materials reinforced with 30 byweight of particles )e letters indicate statistically homogenousgroups (Tukey HSD test (pgt 005))


References

[1] F Angeletaki A Gkogkos E Papazoglou and D KloukosldquoDirect versus indirect inlayonlay composite restorations inposterior teeth A systematic review and meta-analysisrdquoJournal of Dentistry vol 53 pp 12ndash21 2016

[2] S O Alsharif H Bin Md Akil N Abbas Abd El-Aziz andZ Arifin Bin Ahmad ldquoEffect of alumina particles loading onthe mechanical properties of light-cured dental resin com-positesrdquo Materials amp Design vol 54 pp 430ndash435 2014

[3] F F Demarco K Collares F H Coelho-De-Souza et alldquoAnterior composite restorations a systematic review onlong-term survival and reasons for failurerdquo Dental Materialsvol 31 no 10 pp 1214ndash1224 2015

[4] P Suwannaroop P Chaijareenont N KoottathapeH Takahashi and M Arksornnukit ldquoIn vitro wear resistancehardness and elastic modulus of artificial denture teethrdquoDental Materials Journal vol 30 no 4 pp 461ndash468 2011

[5] N Jain and A Wadkar ldquoEffect of nanofiller technology onsurface properties of nanofilled and nanohybrid compositesrdquoInternational Journal of Dentistry and Oral Health vol 1no 1 pp 1ndash5 2015

[6] J Janus G Fauxpoint Y Arntz H Pelletier and O EtienneldquoSurface roughness and morphology of three nano-composites after two different polishing treatments by amultitechnique approachrdquo Dental Materials vol 26 no 5pp 416ndash425 2010

[7] V Prakash P Kumar S Banu V G Sukumaran A Subbiyaand P Vivekanandhan ldquoComparison of true nano withmicrohybrid and nanocluster composite before and aftertooth brushingrdquo Biosciences Biotechnology Research Asiavol 13 no 4 pp 2365ndash2370 2016

[8] I A D Lopes P J V C Monteiro J J B MendesJ M R Gonccedilalves and F J F Caldeira ldquo)e effect of differentfinishing and polishing techniques on surface roughness andgloss of two nanocompositesrdquo Saudi Dental Journal vol 30pp 197ndash207 2018

[9] N A Alrobeigy ldquoMechanical properties of contemporaryresin composites determined by nanoindentationrdquo TantaDental Journal vol 14 no 3 p 129 2017

[10] S El-Safty R Akhtar N Silikas and D C Watts ldquoNano-mechanical properties of dental resin-compositesrdquo DentalMaterials vol 28 no 12 pp 1292ndash1300 2012

[11] M R Kaizer A de Oliveira-Ogliari M S CenciN J M Opdam and R R Moraes ldquoDo nanofill or submicroncomposites show improved smoothness and gloss A sys-tematic review of in vitro studiesrdquo Dental Materials vol 30no 4 pp e41ndashe78 2014

[12] L Cao X Zhao X Gong and S Zhao ldquoAn in vitro in-vestigation of wear resistance and hardness of compositeresinsrdquo International Journal of Clinical and ExperimentalMedicine vol 6 no 6 pp 423ndash430 2013

[13] S Luyckx and A Love ldquo)e relationship between the abrasionresistance and the hardness of WC-Co alloysrdquo Journal of theSouthern African Institute of Mining and Metallurgy vol 104pp 579ndash582 2004

[14] C Zha J Hu A Li et al ldquoNanoindentation study on me-chanical properties and curing depth of dental resin nano-compositesrdquo Polymer Composites vol 39 pp 57ndash64 2018

[15] A Eskandarizadeh N Elm-Amooz and F Rahimi ldquo)e effectof aging on nano-hardness and modulus of elasticity of fourtypes of composites an in-vitro studyrdquo Journal of Dentistryvol 5 no 4 pp 162ndash171 2016

[16] H Y Fan X Q Gan Y Liu Z L Zhu and H Y Yu ldquo)enanomechanical and tribological properties of restorativedental composites after exposure in different types of mediardquoJournal of Nanomaterials vol 2014 Article ID 7590389 pages 2014

[17] J Kleczewska D M Bielinski J Nowak J Sokołowski andM Łukomska-Szymanska ldquoDental composites based ondimethacrylate resins reinforced by nanoparticulate silicardquoPolymers and Polymer Composites vol 24 no 6 pp 411ndash4182016

[18] F Kundie C H Azhari A Muchtar and Z A AhmadldquoEffects of filler size on the mechanical properties of polymer-filled dental composites a review of recent developmentsrdquoJournal of Physical Science vol 29 no 1 pp 141ndash165 2018

[19] M Atai A Pahlavan and N Moin ldquoNano-porous thermallysintered nano silica as novel fillers for dental compositesrdquoDental Materials vol 28 no 2 pp 133ndash145 2012

[20] S B Mitra D Wu and B N Holmes ldquoAn application ofnanotechnology in advanced dental materialsrdquo Journal of theAmerican Dental Association vol 134 no 10 pp 1381ndash13902003

[21] C Kumari K Bhat and R Bansal ldquoEvaluation of surfaceroughness of different restorative composites after polishingusing atomic force microscopyrdquo Journal of ConservativeDentistry vol 19 no 1 p 56 2016

[22] A R Curtis W M Palin G J P Fleming A C C Shortalland P M Marquis ldquo)e mechanical properties of nanofilledresin-based composites the impact of dry and wet cyclic pre-loading on bi-axial flexure strengthrdquoDental Materials vol 25no 2 pp 188ndash197 2009

[23] A R Curtis W M Palin G J P Fleming A C C Shortalland P M Marquis ldquo)e mechanical properties of nanofilledresin-based composites characterizing discrete filler particlesand agglomerates using a micromanipulation techniquerdquoDental Materials vol 25 no 2 pp 180ndash187 2009

[24] E Habib R Wang Y Wang M Zhu and X X Zhu ldquoIn-organic fillers for dental resin composites present and futurerdquoACS Biomaterials Science amp Engineering vol 2 no 1 pp 1ndash112016

[25] L D Randolph W M Palin G Leloup and J G LeprinceldquoFiller characteristics of modern dental resin composites andtheir influence on physico-mechanical propertiesrdquo DentalMaterials vol 32 no 12 pp 1586ndash1599 2016

[26] H A Rodrıguez L F Giraldo and H Casanova ldquoFormationof functionalized nanoclusters by solvent evaporation andtheir effect on the physicochemical properties of dentalcomposite resinsrdquo Dental Materials vol 31 no 7 pp 789ndash798 2015

[27] R Wang M Zhang F Liu et al ldquoInvestigation on thephysical-mechanical properties of dental resin compositesreinforced with novel bimodal silica nanostructuresrdquo Mate-rials Science and Engineering C vol 50 pp 266ndash273 2015

[28] F Iskandar I W Lenggoro B Xia and K OkuyamaldquoFunctional nanostructured silica powders derived fromcolloidal suspensions by sol sprayingrdquo Journal of NanoparticleResearch vol 3 no 4 pp 263ndash270 2001

[29] M Wozniak G Derkachov K Kolwas et al ldquoFormation ofhighly ordered spherical aggregates from drying micro-droplets of colloidal suspensionrdquo Langmuir vol 31 no 28pp 7860ndash7868 2015

[30] W Liu X D Chen and C Selomulya ldquoOn the spray drying ofuniform functional microparticlesrdquo Particuology vol 22pp 1ndash12 2015


[31] M Karabela and I Sideridou ldquoEffect of the structure of silanecoupling agent on sorption characteristics of solvents bydental resin-nanocompositesrdquo Dental Materials vol 24no 12 pp 1631ndash1639 2008

[32] K Itatani A Ooe I J Davies T Umeda Y Musha andS Koda ldquoEffect of colloidal silica addition on the formation ofporous spherical α -calcium orthophosphate agglomerates byspray pyrolysis techniquerdquo Journal of the Ceramic Society ofJapan vol 117 no 1363 pp 363ndash368 2009

[33] W C Oliver and G M Pharr ldquoMeasurement of hardness andelastic modulus by instrumented indentation advances inunderstanding and refinements to methodologyrdquo Journal ofMaterials Research vol 19 no 1 pp 3ndash20 2011

[34] H Zou S Wu and J Shen ldquoPolymersilica nanocompositespreparation characterization properties and applicationsrdquoChemical Reviews vol 108 no 9 pp 3893ndash3957 2008

[35] J H Lee C M Um and I B Lee ldquoRheological properties ofresin composites according to variations in monomer andfiller compositionrdquo Dental Materials vol 22 no 6pp 515ndash526 2006

[36] M J Schick and A T Hubbard Colloidal Silica Fundamentalsand Applications Taylor amp Francis Group Boca Raton FLUSA 2006

[37] J A A Junior and J B Baldo ldquo)e behavior of zeta potentialof silica suspensionsrdquo New Journal of Glass and Ceramicsvol 4 no 2 pp 29ndash37 2014

[38] F Iskandar L Gradon and K Okuyama ldquoControl of themorphology of nanostructured particles prepared by the spraydrying of a nanoparticle solrdquo Journal of Colloid and InterfaceScience vol 265 no 2 pp 296ndash303 2003

[39] W N Wang I W Lenggoro and K Okuyama ldquoDispersionand aggregation of nanoparticles derived from colloidaldroplets under low-pressure conditionsrdquo Journal of Colloidand Interface Science vol 288 no 2 pp 423ndash431 2005

[40] S Y Lee L Gradon S Janeczko F Iskandar andK Okuyama ldquoFormation of highly ordered nanostructures bydrying micrometer colloidal dropletsrdquo ACS Nano vol 4no 8 pp 4717ndash4724 2010

[41] S Zellmer M Lindenau S Michel G Garnweitner andC Schilde ldquoInfluence of surface modification on structureformation and micromechanical properties of spray-driedsilica aggregatesrdquo Journal of Colloid and Interface Sciencevol 464 pp 183ndash190 2016

[42] P M Ferreira S H A Souto B C D BorgesI V de Assunccedilatildeo and G de F A da Costa ldquoImpact of a novelpolishing method on the surface roughness and micromor-phology of nanofilled and microhybrid composite resinsrdquoRevista Portuguesa de Estomatologia Medicina Dentaria eCirurgia Maxilofacial vol 56 no 1 pp 18ndash24 2015

[43] C Schilde C F Burmeister and A Kwade ldquoMeasurementand simulation of micromechanical properties of nano-structured aggregates via nanoindentation and DEM-simu-lationrdquo Powder Technology vol 259 pp 1ndash13 2014

[44] Z Khurshid M Zafar S Qasim S Shahab M Naseem andA AbuReqaiba ldquoAdvances in nanotechnology for restorativedentistryrdquo Materials vol 8 no 2 pp 717ndash731 2015

[45] J L Drummond ldquoNanoindentation of dental compositesrdquoJournal of Biomedical Materials Research Part B AppliedBiomaterials vol 78B no 1 pp 27ndash34 2005

[46] L H He and M V Swain ldquoNanoindentation derived stress-strain properties of dental materialsrdquo Dental Materialsvol 23 no 7 pp 814ndash821 2007

[47] M Hayashi Y Furuya KMinoshima et al ldquoEffects of heatingon the mechanical and chemical properties of human dentinrdquoDental Materials vol 28 no 4 pp 385ndash391 2012

[48] M Abdelaaziz J Mars C Greyling A Atbayqa andM Abdelaaziz ldquoEffect of different sizes of nano-TiO2 on wearresistances and surface hardness of resin-based dental com-positesrdquo Science and Its Applications vol 52 pp 99ndash1022017


CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

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Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

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TribologyAdvances in



ChemistryAdvances in


Advances inPhysical Chemistry


BioMed Research InternationalMaterials

Journal of


Na

nom

ate

ria

ls


Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

on variables such as the testing technique used the abrasiveproperties and environmental conditions [13] )ereforehardness is a parameter that is related to wear resistance butdue to other variables that affect it there is not a directrelationship in all cases In general the literature reports thathardness increases with the quantity of filling [7 10 14ndash16]However it is not necessarily the case that a larger quantityof filling causes an increase in the hardness of the material orgenerates an increase in wear resistance )is is becausehardness also depends on the type and quantity of thesilanization agent the method of surface modification [17]the dispersion degree of nanoparticles the particle size andthe hardness of the filler particles since harder particlesexhibit higher surface hardness in the composite [18]

As particle size is related to roughness hardness andother properties it is proposed that the use of nanofillers willallow materials to be obtained with better mechanicalproperties such as compression fracture and bending re-sistance [19ndash21] and improved surface properties such asbetter gloss polish and wear resistance [5 6 22ndash24] It isalso proposed that the use of nanoparticles will allow re-duced roughness [6] although other studies have pointed toa lack of evidence supporting this since the difference inmeasuring methods and processes for polishing makes itdifficult to compare them [11] )ere are reports that in-dicate that nanoclusters in spite of having bigger particlesize than individual nanoparticles allow materials to beobtained with improved surface properties such as bettergloss polish and wear resistance [5 6 22ndash24] Nanoclustersare nanoparticle aggregates with controlled size and mor-phology obtained prior to the dispersion process in the resin[25ndash27] One of the methodologies used to obtain theseaggregates is spray drying using nanoparticle dispersions[28ndash30] Examples of dental materials that use nanoparticleaggregates are Filtek Supreme Body resins and Filtek Su-preme Translucent resin (3M) which use aggregates of silicaand zirconia nanoparticles [23 25] )ese aggregates areapproximately 760 nm in size and are used in thematerials incombination with nonaggregated silica nanoparticles[22 24] Nanoclusters have been proposed as an alternativeto nanoparticles in order to solve problems such as ex-cessive increase in the viscosity of the composite materialbefore it is polymerized [19] and the tendency of nano-particles to agglomerate due to their high surface energypreventing nanomaterials with nonaggregate nanoparticlesbeing obtained [19] With regard to hardness studies reportimproved hardness on the part of microparticles at relativelyhigher concentrations than nanoparticles and high hard-ness values for dental composites reinforced with nano-particles [18] but there is a lack of evidence about differencesin hardness between composites that use nanoparticles ornanoclusters

)e objective of this study is to correlate the properties ofroughness and hardness with the use of nanoparticles andnanoclusters in order to provide information facilitating theuse of reinforcement agents of this nature in dental resincomposites Our hypothesis is that lower roughness is ob-tained with nonaggregate silica nanoparticles than withnanoclusters while hardness is similar in both cases For the

purpose of this study spray drying was used to obtainnanoclusters of silica and silica-zirconia )is kind ofnanoclusters was chosen because they are used in com-mercial dental composites Composites of nonaggregatedsilica nanoparticles silica nanoclusters and silica-zirconiananoclusters were prepared )e roughness of these mate-rials was evaluated by atomic force microscopy (AFM) andtheir nanohardness by nanoindentation

2 Materials and Methods

21 Materials For dental resin composites the followingkind of nanoparticles were used silica in an aqueous dis-persion (20 by weight of nanoparticles) with a pH between2 and 4 brand name SNOWTEXreg ST-OL made by NissanChemical (USA) and zirconia in an aqueous dispersion(30 by weight of nanoparticles) pH 3 brand nameNanoUsereg ZR 30-AL made by Nissan Chemical (USA)Silica nanoparticles were functionalized by methacrylox-ypropyltrimethoxysilane (MPS) (97) (Alfa Aesar)

)e monomers were bisphenol A glycidyl methacrylate(Bis-GMA) (90) bisphenol A polyethylene glycol dietherdimethacrylate (Bis-EMA) (90) urethane dimethylacry-late (UDMA) (90) and triethylene glycol dimethacrylate(TEGDMA) (90) )ese were acquired from Esstech (USA)

Polymerization initiation system was composed by ethyl4-(dimethylamino) benzoate (4EDMAB) (99) provided byAlfa Aesar and (CQ) Camphorquinone (97) provided bySigma Aldrich

22 Methods

221 Characterization of Silica and Zirconia NanoparticlesMorphology of the silica nanoparticles was determinedusing a S4700 scanning electron microscope (Hitachi Ja-pan) An AuPd alloy particle coating of approximately 2 nmthickness was deposited on the sample using a sputteringdevice All the samples were analyzed at a work distance of5mm and a voltage of 150 kV

)e morphology of zirconia particles was determinedusing a 2010LAB6 transmission electron microscope (TEM)(Jeol Japan) For this analysis the dispersion was diluted inethanol After this a drop of each dispersion was depositedin a TEM grid allowing the water and ethanol to evaporate)e samples were analyzed using a voltage of 200 kV

)e ζ potential measurements of the silica and zirconiananoparticles were performed using the light scatteringtechnique for which Zetasizer Nano ZS equipment (Mal-vern Instruments UK) was used Before each measurementthe particle dispersion was diluted using distilled water

222 Functionalization of Silica NanoparticlesFunctionalization of silica nanoparticles was carried out byheating a suspension of silica nanoparticles (20 wt) in thepresence of MPS at 65degC for 30 hours under constantstirring )e weight percent of MPS required for nano-particle silanization was calculated according to the fol-lowing equation [31]


X A

w1113874 1113875f (1)

































50nm

(a)

20nm

(b)




4000 3500 3000 2500 2000 1500 1000 500

0

5

10

15

20

25

Tran

smitt

ance

()



Bare silica



010

2

4

6

8

10

12

Vol

ume (

)

Diameter (microm)


1 10









(a)


(b)


(c)



(d)






a


b

b

0

20

40

60

80

100

120

140

160

180

Roug

hnes

s (nm

)



x 25

micromy 25 microm

1631 nm100050000ndash500ndash1000

ndash2000

ndash2818ndash2500

ndash1500

(a)


036 microm 030020

005ndash005

ndash020

ndash033

ndash010


025015010000

ndash015ndash025

(b)

6 nmndash16 nm

x 10

0 microm

y 100 microm

57 nm40

00

ndash40

ndash120ndash100

20

ndash20

ndash60ndash80

ndash140ndash162

(c)







4 Conclusions




Data Availability




Acknowledgments


a


a

a

000

005

010

015

020

025

030

Nan

ohar

dnes

s (G

Pa)



References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




X A

w1113874 1113875f (1)

































50nm

(a)

20nm

(b)




4000 3500 3000 2500 2000 1500 1000 500

0

5

10

15

20

25

Tran

smitt

ance

()



Bare silica



010

2

4

6

8

10

12

Vol

ume (

)

Diameter (microm)


1 10









(a)


(b)


(c)



(d)






a


b

b

0

20

40

60

80

100

120

140

160

180

Roug

hnes

s (nm

)



x 25

micromy 25 microm

1631 nm100050000ndash500ndash1000

ndash2000

ndash2818ndash2500

ndash1500

(a)


036 microm 030020

005ndash005

ndash020

ndash033

ndash010


025015010000

ndash015ndash025

(b)

6 nmndash16 nm

x 10

0 microm

y 100 microm

57 nm40

00

ndash40

ndash120ndash100

20

ndash20

ndash60ndash80

ndash140ndash162

(c)







4 Conclusions




Data Availability




Acknowledgments


a


a

a

000

005

010

015

020

025

030

Nan

ohar

dnes

s (G

Pa)



References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






















50nm

(a)

20nm

(b)




4000 3500 3000 2500 2000 1500 1000 500

0

5

10

15

20

25

Tran

smitt

ance

()



Bare silica



010

2

4

6

8

10

12

Vol

ume (

)

Diameter (microm)


1 10









(a)


(b)


(c)



(d)






a


b

b

0

20

40

60

80

100

120

140

160

180

Roug

hnes

s (nm

)



x 25

micromy 25 microm

1631 nm100050000ndash500ndash1000

ndash2000

ndash2818ndash2500

ndash1500

(a)


036 microm 030020

005ndash005

ndash020

ndash033

ndash010


025015010000

ndash015ndash025

(b)

6 nmndash16 nm

x 10

0 microm

y 100 microm

57 nm40

00

ndash40

ndash120ndash100

20

ndash20

ndash60ndash80

ndash140ndash162

(c)







4 Conclusions




Data Availability




Acknowledgments


a


a

a

000

005

010

015

020

025

030

Nan

ohar

dnes

s (G

Pa)



References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls










(a)


(b)


(c)



(d)






a


b

b

0

20

40

60

80

100

120

140

160

180

Roug

hnes

s (nm

)



x 25

micromy 25 microm

1631 nm100050000ndash500ndash1000

ndash2000

ndash2818ndash2500

ndash1500

(a)


036 microm 030020

005ndash005

ndash020

ndash033

ndash010


025015010000

ndash015ndash025

(b)

6 nmndash16 nm

x 10

0 microm

y 100 microm

57 nm40

00

ndash40

ndash120ndash100

20

ndash20

ndash60ndash80

ndash140ndash162

(c)







4 Conclusions




Data Availability




Acknowledgments


a


a

a

000

005

010

015

020

025

030

Nan

ohar

dnes

s (G

Pa)



References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls







a


b

b

0

20

40

60

80

100

120

140

160

180

Roug

hnes

s (nm

)



x 25

micromy 25 microm

1631 nm100050000ndash500ndash1000

ndash2000

ndash2818ndash2500

ndash1500

(a)


036 microm 030020

005ndash005

ndash020

ndash033

ndash010


025015010000

ndash015ndash025

(b)

6 nmndash16 nm

x 10

0 microm

y 100 microm

57 nm40

00

ndash40

ndash120ndash100

20

ndash20

ndash60ndash80

ndash140ndash162

(c)







4 Conclusions




Data Availability




Acknowledgments


a


a

a

000

005

010

015

020

025

030

Nan

ohar

dnes

s (G

Pa)



References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls








4 Conclusions




Data Availability




Acknowledgments


a


a

a

000

005

010

015

020

025

030

Nan

ohar

dnes

s (G

Pa)



References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls

























Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




Effects of Silica Nanoparticles and Silica-Zirconia...

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Transcript of Effects of Silica Nanoparticles and Silica-Zirconia...