research article oleophobic modification of hollow...

Research ArticleOleophobic Modification of Hollow GlassMicrospheres and Its Effect on the Foaming Capacity andStability of Foam Extinguishing Agent

Baohua Tang12 and Zhaoliang Wu1

1School of Chemical Engineering and Technology Hebei University of Technology Tianjin 300130 China2Fundamental Department Chinese Peoplersquos Armed Police Academy Langfang Hebei 065000 China

Correspondence should be addressed to Zhaoliang Wu zhaoliangwu hebut163com

Received 9 November 2014 Accepted 19 March 2015

Academic Editor Guillaume Galliero

Copyright copy 2015 B Tang and Z Wu This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

We utilized tridecafluorooctyltriethoxysilane (F8261) for the surface modification of hollow glass microspheres (HGM) We thenmeasured the contact angles and the residing timeof oil droplets on theHGMsurface under different conditions and investigated theeffects of themodifier concentration reaction time and reaction temperature and other factors on the outcomes of themodificationreactionWe also compared the effects ofHGMon the expansion ratio and 25drainage time of protein foam liquid before and afterthe modification treatment and investigated the effects of HGM surface oleophobic modification on the foaming capacity and sta-bility of foam extinguishing agent The results showed that when the F8261 concentration was 10 the temperature was 60∘C andthe ultrasound treatment time was 20 h the contact angle was up to 1325∘ the oleophobic property of HGM could be significantlyenhanced and the foaming capacity and the oil surface stability were significantly improved by the oleophobic modification

1 Introduction

Protein foam extinguishing agent is most commonly usedfire extinguishing material when fighting oil fires It achievesthe fire-fighting purpose mainly based on the phenomenonthat foam can suppress oil evaporation It has been foundin practice that the thermal stability of regular protein foamis poor If the supply of foam is of insufficient strengthfoam will continue to break down under the effect of flamesand heat radiation and the fire thus can lose control againand is prone to recrudescence [1 2] It has been shownthat after adding hollow glass microspheres (HGM) to foamextinguishing agent a stable scaffold of three-phase foamcan form inside the foam so that the thermal stability offoam can been significantly improved [3] However sinceHGM has a strong ability to absorb oil it was found thatthe stability of foam added with HGM on oil surface wassignificantly lower than regular two-phase protein foamwhen fighting oil fires [4] Adding fluorocarbon surfactantto foam extinguishing agent might improve the stability ofHGM foam on oil surface However it still cannot meet

the actual fire-fighting needs [5] Xiao and Shou foundthat the modification of ultrafine particle fire extinguishingagent with 1 fluorocarbon surfactant could increase theoleophobicity of ultrafine particles [6] This paper usedtridecafluorooctyltriethoxysilane (hereinafter referred to asF8261) for the oleophobic treatment of HGM surface Wealso investigated the effects of the modifier concentrationreaction time and reaction temperature and other factorson the modification effect and compared the stability offoam extinguishing agent on oil surface before and after theoleophobic modification

2 Experimental Equipment and Materials

21 Experimental Equipment We used the following equip-ment electric stirrer (WH7401290 speed 200sim3000 rmin30 cm times 35 cm times 76 cm Tianjin Weihua ExperimentalInstrument Factory) thermostatic stirrer (Jintan GuoshengExperimental Instrument Factory Jintan Jiangsu Province)ultrasonic cleaner (sk3310LHC) sessile drop contact angle

Hindawi Publishing CorporationJournal of ChemistryVolume 2015 Article ID 923894 6 pageshttpdxdoiorg1011552015923894

2 Journal of Chemistry

measuring instrument (JC2000C Shanghai Powereach Dig-ital Technology Equipment Co) three-necked flask 500mLbeaker and stopwatch

22 Experimental Materials TheHGMwere purchased fromthe Qinhuangdao Aoge glass beads company The range ofHGM particle size was 10sim100 120583m the bulk density was018sim020 gcm3 the floating rate was ge93 and the crush-ing strength was 3sim5MPa Tridecafluorooctyltriethoxysilane(hereinafter referred to as F8261) was from Wuhan De FuEconomic Development Co Ltd We used 90 kerosene(commercially available) protein foam fire-extinguishingsolution (6 of animal protein liquid with the quality inaccordance with the ZBC84007 technology requirement Firepharmaceutical factory of the Armed Police Academy) andkerosene (commercially available)

3 Experimental Methods

31 HGM Surface Oleophobic Treatment HGM surface oleo-phobic treatment consisted of the three sequential stepsof acid pretreatment alkaline pretreatment and surfaceoleophobic modification

311 Acid Pretreatment An appropriate amount of HGMwas added to a mixed solution of concentrated sulfuric acidand 30 hydrogen peroxide at a ratio of 7 3 (vv) followedwith 20min of ultrasound treatment The HGM were thenwashed filtered and dried in order to remove the impuritiesadsorbed on the surface of HGM

312 Alkaline Pretreatment Anappropriate amount ofHGMwas added to amixed solution of 25 aqueous ammonia 30hydrogen peroxide and water in a ratio of 1 1 5 (v v v)followed with 60min of ultrasound treatment at 60 plusmn 5∘CThe HGM were then filtered and dried

313 Oleophobic Surface Modification Concentrated hydro-chloric acid was used to adjust the pH of the F8261 ethanolsolution to about 35 An appropriate amount of HGM withsurface pretreatment was added followed with ultrasoundstirring for a certain period of time The HGM were thenfiltered and dried for use

32 Measurement of the Contact Angle and the Residing Timeof Oil Droplets on the HGM Surface An appropriate amountof HGM was placed on a slide and flattened A microinjectorwas use to apply 25 120583L of kerosene in drops onto thepowder surface And the JC2000C sessile drop contact anglemeasuring device was used to determine the contact anglebetween the oil droplets and HGM

An appropriate amount of HGM was placed into a smallcrucible that was horizontally positioned A glass slide wasused to gently press and flatten the HGM A syringe was usedto apply 01mL of kerosene in drops onto the powder surfaceThemorphology of oil droplets inHGMsurfacewas observedand the time that the oil droplets resided on the surface wasrecorded

Figure 1 Device measuring the foam drainage speed

33 Measurement of the Liquid Drainage Speed The devicemeasuring the foam drainage speed is shown in Figure 1 Theprepared foamwas quickly placed in the cylinder on the top ofthe device and the drained liquid then flowed into the liquidcarrier in the lower part of the device The readings of theelectronic balance were recorded once every 10 s in order toinvestigate the foam drainage capacityThe time when 25 ofthe liquid is drained is called the 25 drainage time (119905

25)

34 Experiments Measuring the Foaming Capacity of FoamFire Extinguishing Agent and the Stability on Oil Surface Theexperimental methods for the foaming capacity of foam fireextinguishing agent and the stability on oil surface are asdescribed in the literature [4 5]

4 Experimental Results and Discussion

41 Effect of F8261 Concentration on the HGM OleophobicProperty In order to investigate the effect of F8261 con-centration on the HGM oleophobic property 1 g of HGMwith acid and alkaline pretreatments was added into 100mLof different concentrations of F8261 ethanol solutions Theultrasound treatment time and the stirring time were fixed at20 h and 6 h respectivelyThe results of theHGMoleophobicproperty measurement are shown in Table 1 where 119883 is theF8261 concentration 120579 is the contact angle and 119905

119904is the

residing time of the oil droplets on the HGM surface Figures2 and 3 are photos that were taken whenHGMmodified withdifferent concentrations of F8261 were used for the contactangle measurement

Table 1 shows that the F8261 concentration can signifi-cantly affect the oleophobic property of the HGM surfaceWhen the F8261 concentration was below 1 the contactangle and the residing time increased with increasing F8261concentration When the concentration exceeded 1 theF8261 concentration had little effects on the contact angle andthe residing time This is because the modification of HGMby F8261 is a surface chemical reaction Therefore whenthe F8261 concentration is low the number of fluorocarbon

Journal of Chemistry 3

(a) (b)

(c) (d)

Figure 2 Comparison of the contact angles of HGM modified by different concentrations of F8261 ((a) 01 (b) 025 (c) 075 and (d)10)

Table 1 Effect of F8261 concentration on the oleophobic property of HGM

119883 120579∘ 119905

119904

Morphology of oil droplets on HGM surface

0 mdash mdash Oil droplets immediately penetrate the powder aftercontacting with the powder

01 785 36 s Oil droplets are fattened-sphere shaped with short residingtime

025 955 78 s Oil droplets are fattened-sphere shaped with slightly shortresiding time

05 1185 386 s Oil droplets are hemispherical shaped with long residing time075 1210 gt72 h Oil droplets are roughly spherical shaped10 1325 gt120 h Oil droplets are spherical shaped20 133 gt120 h Same as above

chains grafted to the HGM surface is low and the HGMoleophobic property is poor (Figures 2(a) and 2(b)) HigherF8261 concentrations lead to higher grafting rates of thereaction and larger contact angles The oleophobic propertyof HGM is significantly enhanced and the residing time of theoil droplets on the powder surface is also longer (Figures 2(c)and 2(b)) Once the concentration of F8261 reaches the level

that saturates the number of hydroxyl groups on the HGMsurface further increase in the F8261 concentration has littleeffect on the oleophobic property of the powder

42 Effects of the Reaction Temperature on the HGMOleopho-bic Property In order to investigate the pattern underlying


Table 2 Effect of reaction temperature on the oleophobic property of HGM

119879∘C 120579∘ 119905 Note

36 1185 386 s Oil droplets immediately penetrate the powder after contactingwith the powder

40 1260 576 s Same as above60 1280 gt72 h Oil droplets are spherical shaped with long residing time80 1315 gt72 h Same as above

Table 3 Effect of reaction time on the oleophobic property ofHGM

119905

119900

h 120579∘ 119905

0 mdash mdash05 1055 900 s10 1120 sim22 h15 1285 gt43 h

the effects of the reaction temperature on the HGM oleo-phobic modification the amount of HGM was fixed at 1 gthe volume of ethanol was 100mL the F8261 concentrationwas 05 the ultrasound treatment time was 20 h and thestirring timewas 30 hWe compared the oleophobic propertyof HGM modified under different temperatures and theresults are shown in Table 2

Table 2 shows that the reaction temperature has a greatinfluence on the oleophobic properties of the HGM surfaceUnder the conditions of same F8261 concentration and reac-tion time as the reaction temperature increases the contactangle between the oil droplets and the powder graduallyincreases and the time that the powder remains oleophobicbecomes longer Modification under room temperature didnot lead to significant effects on the powder However whenthe reaction temperature exceeded 60∘C the contact angle ofthe oil droplet was up to 1280∘ and the time that the powderremained oleophobic was for more than three days

43 Effects of Ultrasound Reaction Time on the OleophobicProperty of the F8261 Modified HGM When investigatingthe effects of ultrasound reaction time on the oleophobicproperty of the HGM surface the amount of pretreatedpowder was fixed at 1 g anhydrous ethanol was fixed at100mL the F8261 concentration was 10 and the reactiontemperature was 60∘C The results are shown in Table 3 and119905

0in the table is the ultrasound reaction timeTable 3 shows that ultrasound treatment time has a big

impact on the HGM surface oleophobic property At thesame temperature concentration stirring and reaction timelonger ultrasound treatment time leads to better surfacemodification effect of the powderThis is because the graftingreaction on the HGM surface is slow The propagation of theultrasonic wave in the liquid can produce a strong cavitationwhich can increase the speed of response Therefore longerultrasonic reaction time leads to a more thorough contactreaction between the HGM and the silane coupling agent ahigher grafting ratio and stronger oleophobic properties ofthe HGM

9

8

7

6

5

4

3

2

1

0

0 30 60 90 120 150

1

2

Figure 3 Comparison of the expansion ratios of foam after HGMis modified by F8261 (1 modified 2 unmodified)

44 Effect of the Oleophobic Modification of HGM on theFoaming Capacity and Stability of Foam Extinguishing AgentIn order to investigate the effect of the oleophobic modifiedHGM on the foaming capacity and stability of foam solutionwe fixed the concentration of the protein foam extinguishingagent at 10 and detected the expansion ratios and 119905

25 of theprotein foam extinguishing agent added with different pro-portions of HGM before and after oleophobic modificationThe results are shown in Figures 3 and 4

Figures 3 and 4 prove that after the oleophobic mod-ification the foaming capacity and the stability of foamextinguishing agent are significantly improved Before themodification treatment the foaming capacity of the foamextinguishing agent was significantly inhibited by the addi-tion of HGM and the stability was also significantly reducedThe larger the added amount is the more obvious this effectis When the proportion of added HGM exceeded 50 thefoam extinguishing agent could not foam effectively andshowed poor stability After the oleophobic modificationthe foaming capacity and the stability of foam extinguishingagent are improved significantly As shown in Figure 4 beforethe addition ofmodifiedHGM the liquid drainage volume ofthe ordinary two-phase protein foam increased linearly withtime and 1297 of the liquid was drained from the foamwithin 2min In contrast the liquid drainage speed of thefoam added with modified HGM slowed down significantlyand its 119905

25 value gradually increased When the proportion


0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

14

16

18

12

Figure 4 Comparison of 11990525 of foam after HGM is modified by

F8261 (1 unmodified 2 modified)

of modified HGM added was 100 11990525 of the foam was up

to 1810158401510158401015840 around 84 times of the ordinary two-phase foamThis is because the impurities adsorbed on the surface

of the unmodified HGM have a certain extent of inhibitoryeffect on foaming Larger amounts of unmodified HGMadded lead to more significant defoaming effects Afterthe F8261 oleophobic modification the HGM surface iscoated with fluorine-containing groups reducing the tensionbetween the beads and the foam interface and significantlyreducing the liquid drainage speed of the foam

45 Effect of HGM Oleophobic Modification on the Stability ofFoam on Oil Surface The level of HGM added to the foamsystem was fixed at 30 and the concentration of the proteinsolution was 10 We compared the trends by which theheight of the foam changed over time on oil surface beforeand after oleophobic modification And the results are shownin Figure 5

Figure 5 shows that compared with the protein foamwithout the addition of HGM the presence of HGM led topoor foam stability and the foam rapidly burst with the foamheight decreased by 830 within 50min In contrast for thethree-phase foam added with HGM with F8261 oleophobicmodification the height was decreased less than 6 in30minThis indicates that after the oleophobic modificationHGM can significantly enhance the foam stability on oilsurface

This is due to the fact that the unmodified HGM has astrong oil-absorbing ability Once the foam contacts the oilsurface the HGM keep absorbing oil and thus continuouslyenter the oil phase As a result the foam scaffold is rapidlydeconstructed from bottom to top and the air bubblesinside the foam constantly integrate with each other leadingto increased volume and reduced air pressure inside thebubbles When exceeding its critical carrying capacity theupper foam will sink quickly due to gravity causing the

10

9

8

7

6

5

4

3

2

1

0

0 5 10 15 20 25 30

1

2

3

Figure 5 Effect of HGM on the stability of foam on oil surface (1without HGM 2 unmodified HGM and 3 modified HGM)

instantaneous reduction of the foamoverall height (Figure 6)After beingmodified by the fluorinated silane coupling agentthe oleophobicity of the HGM is increased Although thebottom of the foam is still in contact with the oil the HGMwill not enter the oil phase and the phenomenon of bottom-up destruction will not occur Therefore the foam scaffold ismaintained longer and the foam shows stronger oil surfacestability (Figure 6(b))

5 Conclusions

(1) After the treatment of fluorinated silane couplingagent F8261 the HGM oleophobic property can besignificantly improved and can be further improvedby increasing the F8261 concentration raising thereaction temperature and increasing the reactiontime Under the conditions of 60∘C 10 F8261 and20 h of ultrasound reaction the contact angle wasup to 1325∘ and the oil droplets could stay on HGMsurface over five days

(2) After the oleophobic modification the foamingcapacity and stability of foam extinguishing agentscontaining HGM can be significantly improved Afterthe modification the amount of added HGM hasno significant effect on the foaming capacity of theprotein foam liquidHowever the rate bywhich liquidis drained from the foam slowed down significantlywith increasing amounts of HGM while the 25drainage time gradually extended And larger amountof HGM with oleophobic modification led to greaterstability of the foam When the level of modifiedHGM reached 100 the 25 drainage time of thefoam was up to 1810158401510158401015840 and was about 84 times thatof the ordinary two-phase foam


(a)

(b)

Figure 6 Comparison of the stability of foam after themodificationof HGM by F8261 ((a) before modification (b) after modification)

(3) After the modification of fluorine-containing silanecoupling agent the oleophobic property of the HGMstrengthens the skeleton structure inside the foamand the modified foam can maintain its structure fora long time and demonstrate the superior stability onthe oil surface

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was financially supported by the Ministry ofPublic Security the application of innovation projects (no2013YYCXWJXY105) Key Laboratory of the Ministry ofPublic Security and open project (no KF201309) andNaturalScience Foundations of China (21236001)

References

[1] B Y Lattimer and J Trelles ldquoFoam spread over a liquid poolrdquoFire Safety Journal vol 42 no 4 pp 249ndash264 2007

[2] C F Boyd and M di Marzo ldquoThe behavior of a fire-protectionfoam exposed to radiant heatingrdquo International Journal of Heatand Mass Transfer vol 41 no 12 pp 1719ndash1728 1998

[3] C Weihong L Ran and G Zidong ldquoEffects of the hollow glassmicrosphere on the foaming ability and stability of fire fightingfoamrdquo Fire Science vol 16 no 3 pp 133ndash136 2007

[4] W-H Chen W-F Du and X-N Xu ldquoExperimental study onsnti-solubility and snti-burning property of hollowmicrospherethree-phase foamrdquo Fire Safety Science vol 17 no 1 pp 15ndash192008

[5] W-H Chen W-F Du and W He ldquoEffect of fluorocarbonsurfactants on anti-solubility and anti-burning property ofhollow microsphere three-phase foamrdquo Fire Safety Science vol18 no 3 pp 182ndash186 2009

[6] J-S Xiao and J Shou ldquoSpreading of aqueous mixtures of flu-orocarbon hydrocarbon surfactants on oilrdquo Chemical Researchand Application vol 14 no 2 pp 137ndash140 2002

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measuring instrument (JC2000C Shanghai Powereach Dig-ital Technology Equipment Co) three-necked flask 500mLbeaker and stopwatch

22 Experimental Materials TheHGMwere purchased fromthe Qinhuangdao Aoge glass beads company The range ofHGM particle size was 10sim100 120583m the bulk density was018sim020 gcm3 the floating rate was ge93 and the crush-ing strength was 3sim5MPa Tridecafluorooctyltriethoxysilane(hereinafter referred to as F8261) was from Wuhan De FuEconomic Development Co Ltd We used 90 kerosene(commercially available) protein foam fire-extinguishingsolution (6 of animal protein liquid with the quality inaccordance with the ZBC84007 technology requirement Firepharmaceutical factory of the Armed Police Academy) andkerosene (commercially available)

3 Experimental Methods

31 HGM Surface Oleophobic Treatment HGM surface oleo-phobic treatment consisted of the three sequential stepsof acid pretreatment alkaline pretreatment and surfaceoleophobic modification

311 Acid Pretreatment An appropriate amount of HGMwas added to a mixed solution of concentrated sulfuric acidand 30 hydrogen peroxide at a ratio of 7 3 (vv) followedwith 20min of ultrasound treatment The HGM were thenwashed filtered and dried in order to remove the impuritiesadsorbed on the surface of HGM

312 Alkaline Pretreatment Anappropriate amount ofHGMwas added to amixed solution of 25 aqueous ammonia 30hydrogen peroxide and water in a ratio of 1 1 5 (v v v)followed with 60min of ultrasound treatment at 60 plusmn 5∘CThe HGM were then filtered and dried

313 Oleophobic Surface Modification Concentrated hydro-chloric acid was used to adjust the pH of the F8261 ethanolsolution to about 35 An appropriate amount of HGM withsurface pretreatment was added followed with ultrasoundstirring for a certain period of time The HGM were thenfiltered and dried for use

32 Measurement of the Contact Angle and the Residing Timeof Oil Droplets on the HGM Surface An appropriate amountof HGM was placed on a slide and flattened A microinjectorwas use to apply 25 120583L of kerosene in drops onto thepowder surface And the JC2000C sessile drop contact anglemeasuring device was used to determine the contact anglebetween the oil droplets and HGM

An appropriate amount of HGM was placed into a smallcrucible that was horizontally positioned A glass slide wasused to gently press and flatten the HGM A syringe was usedto apply 01mL of kerosene in drops onto the powder surfaceThemorphology of oil droplets inHGMsurfacewas observedand the time that the oil droplets resided on the surface wasrecorded

Figure 1 Device measuring the foam drainage speed

33 Measurement of the Liquid Drainage Speed The devicemeasuring the foam drainage speed is shown in Figure 1 Theprepared foamwas quickly placed in the cylinder on the top ofthe device and the drained liquid then flowed into the liquidcarrier in the lower part of the device The readings of theelectronic balance were recorded once every 10 s in order toinvestigate the foam drainage capacityThe time when 25 ofthe liquid is drained is called the 25 drainage time (119905

25)

34 Experiments Measuring the Foaming Capacity of FoamFire Extinguishing Agent and the Stability on Oil Surface Theexperimental methods for the foaming capacity of foam fireextinguishing agent and the stability on oil surface are asdescribed in the literature [4 5]

4 Experimental Results and Discussion

41 Effect of F8261 Concentration on the HGM OleophobicProperty In order to investigate the effect of F8261 con-centration on the HGM oleophobic property 1 g of HGMwith acid and alkaline pretreatments was added into 100mLof different concentrations of F8261 ethanol solutions Theultrasound treatment time and the stirring time were fixed at20 h and 6 h respectivelyThe results of theHGMoleophobicproperty measurement are shown in Table 1 where 119883 is theF8261 concentration 120579 is the contact angle and 119905

119904is the

residing time of the oil droplets on the HGM surface Figures2 and 3 are photos that were taken whenHGMmodified withdifferent concentrations of F8261 were used for the contactangle measurement

Table 1 shows that the F8261 concentration can signifi-cantly affect the oleophobic property of the HGM surfaceWhen the F8261 concentration was below 1 the contactangle and the residing time increased with increasing F8261concentration When the concentration exceeded 1 theF8261 concentration had little effects on the contact angle andthe residing time This is because the modification of HGMby F8261 is a surface chemical reaction Therefore whenthe F8261 concentration is low the number of fluorocarbon


(a) (b)

(c) (d)



119883 120579∘ 119905

119904











119879∘C 120579∘ 119905 Note




119905

119900

h 120579∘ 119905







9

8

7

6

5

4

3

2

1

0

0 30 60 90 120 150

1

2







0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

14

16

18

12









10

9

8

7

6

5

4

3

2

1

0

0 5 10 15 20 25 30

1

2

3



5 Conclusions




(a)

(b)





Acknowledgments


References
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

(c) (d)



119883 120579∘ 119905

119904











119879∘C 120579∘ 119905 Note




119905

119900

h 120579∘ 119905







9

8

7

6

5

4

3

2

1

0

0 30 60 90 120 150

1

2







0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

14

16

18

12









10

9

8

7

6

5

4

3

2

1

0

0 5 10 15 20 25 30

1

2

3



5 Conclusions




(a)

(b)





Acknowledgments


References
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



119879∘C 120579∘ 119905 Note




119905

119900

h 120579∘ 119905







9

8

7

6

5

4

3

2

1

0

0 30 60 90 120 150

1

2







0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

14

16

18

12









10

9

8

7

6

5

4

3

2

1

0

0 5 10 15 20 25 30

1

2

3



5 Conclusions




(a)

(b)





Acknowledgments


References
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

14

16

18

12









10

9

8

7

6

5

4

3

2

1

0

0 5 10 15 20 25 30

1

2

3



5 Conclusions




(a)

(b)





Acknowledgments


References
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a)

(b)





Acknowledgments


References
















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article oleophobic modification of hollow...

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