Construction and Building Materials 161 (2018) 381–388

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Construction and Building Materials

journal homepage: www.elsevier .com/locate /conbui ldmat

TiO2-SiO2 nanocomposite aerogel loaded in melamine-impregnatedpaper for multi-functionalization: Formaldehyde degradation and smokesuppression

https://doi.org/10.1016/j.conbuildmat.2017.11.1290950-0618/� 2017 Published by Elsevier Ltd.

⇑ Corresponding author at: No. 159 Longpan Road, 210037 Nanjing, China.E-mail address: zhouxiaoyan@njfu.edu.cn (X. Zhou).

Weimin Chen a,b,c,d, Shuai Li a,d, Mohammad Feizbakhshan b, Biniyam Tefera Amdebrhan b, Shukai Shi a,d,Wang Xin a,d, Thiphuong Nguyen a,d, Minzhi Chen a,d, Xiaoyan Zhou a,d,⇑aCollege of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, ChinabDepartment of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 2W2, CanadacNanjing Suman Plasma Technology Co., Ltd, Enterprise of Graduate Research Station of Jiangsu Province, Nanjing 210001, Chinad Jiangsu Engineering Research Center of Fast-growing Trees and Agri-fiber Materials, Nanjing 210037, China

h i g h l i g h t s

� Multi-functions of formaldehyde degradation and smoke suppression were achieved.� Both high gaseous and liquid formaldehyde degradation rates (56.6% and 65.8%) were achieved.� The coated melamine-impregnated paper is easy to realize industrial production.

a r t i c l e i n f o

Article history:Received 1 July 2017Received in revised form 10 October 2017Accepted 24 November 2017

Keywords:TiO2-SiO2 nanocomposite aerogelPhotocatalytic activityFormaldehydeSmoke suppression

a b s t r a c t

A raw decorative paper was coated with a mixture of TiO2-SiO2 nanocomposite aerogel and melamine-formaldehyde resin to achieve dual functions, namely formaldehyde degradation and smoke suppression.The physical and chemical structure of TiO2-SiO2 nanocomposite aerogel and its photocatalytic activityon liquid formaldehyde degradation were revealed. Moreover, the coated melamine-impregnated paperwas further decorated into the surface of a poplar wood veneer to prepare a real indoor panel. A self-designed sealed box and cone calorimeter were used to test its photocatalytic activity on gaseousformaldehyde degradation and smoke suppression. The results showed that the presence of massivemesopores in TiO2-SiO2 nanocomposite aerogel and the appearance of anatase nanocrystal of TiO2 syner-gistically lead to both the high liquid and gaseous formaldehyde degradation rates of 65.8% and 56.6%. Inaddition, the porous structure and incombustibility of TiO2-SiO2 nanocomposite aerogel also result inhigh smoke suppression, demonstrating the maximum decrease in CO and CO2 production by 56.2%and 33.2%. The preparation process of the coated melamine-impregnated paper is easy to realize indus-trial production. After decorated into the surface of wood-based panels, it can be used as the indoor mate-rials of wall, floor, and furniture.

� 2017 Published by Elsevier Ltd.

1. Introduction

Melamine-impregnated paper is widely applied to decorate thesurface of wood-based panels such as particleboard, fiberboard,and plywood. It can improve the dimensional stability of wood-based panels via resisting naturally absorption of humidity [1].Physical and mechanical properties can be also enhanced espe-

cially on the modulus of elasticity [2]. Moreover, the panel surfacecoated with multi-layer of melamine-impregnated paper results inthe significant reduction in formaldehyde emissions, since thepaper provides a physical isolation layer to prevent the emissionof gaseous formaldehyde from panel itself [3]. However,melamine-impregnated paper is easy to be damaged during theprocess of application, and thus the gaseous formaldehyde gener-ated from wood-based panels would be released into externalenvironment. In addition, melamine-impregnated paper has no

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effect on the degradation of gaseous formaldehyde from externalenvironment.

During the last decade, TiO2 was doped into the nano-SiO2

structure in order to synthesize TiO2-SiO2 nanocomposite aero-gel. Its photocatalytic activity is significantly enhanced owingto the improvement on specific surface area for TiO2. Early stud-ies have demonstrated the high efficiency of TiO2-SiO2 nanocom-posite aerogel on the decomposition of hazardous chemicals,especially for liquid phase [9–11]. Yoda has found thatTiO2-SiO2 composite aerogel can lead to the effective decomposi-tion of benzene and the decomposition degree mainly dependson the crystallinity of TiO2 [4]. Deng has prepared theTiO2-SiO2 composite aerogel via the sol-gel method and reportedthat phenol decomposition rate of 34% was achieved [5]. Ander-son has studied the synergistical effect between TiO2 and SiO2

during the photocatalytic decomposition of organic compounds,which revealed that the particle size of SiO2 and its distributionon composite structure have a significant effect on the photocat-alytic activity of TiO2 [6]. In addition, Su has proved that the for-mation of network structure based on cross-linked Si-O-Ti bondand oxygen vacancies in TiO2 has a synergetic effect on bothphases [7]. The photocatalytic decomposition effect ofTiO2-SiO2 composite aerogel on organic chemicals of indoor airpollutants becomes the recent research topic, since the most partof furniture and indoor decorating materials will release haz-ardous organic chemicals, especially gaseous formaldehyde[12,13]. Suligoj has applied the TiO2-SiO2 films to decomposegaseous formaldehyde and the decomposition rate reached 91%[8]. Therefore, melamine-impregnated paper coated with TiO2-SiO2 nanocomposite aerogel can be applied in gaseous formalde-hyde degradation, since high specific surface area and porousstructure lead to high adsorption capacity which can block theemission of gaseous formaldehyde from the wood-based panelitself. In addition, its high photocatalytic activity can also resultin the effective degradation on gaseous formaldehyde in indoorair. The effect of TiO2-SiO2 nanocomposite aerogel on liquidformaldehyde degradation is also worth studying since it canreveal its degradation mechanism comprehensively.

The wood-based panel is easy to burn under a fire accident. Itscombustion would also release the toxic fumes including carbonmonoxide, nitrogen oxide, and char power which can result inthe death of human life. Many methods were applied in thewood-based panel to achieve high smoke suppression. Especially,previous studies have reported the good smoke suppression ofthe wood composite coated with SiO2 or TiO2, respectively[14,15]. Mahr has found that single and double layered sol-gelderived TiO2 and SiO2-wood composites have excellent smoke sup-pression [16]. The incombustibility of SiO2 and TiO2 can form thestable and closed barrier layer during burning. Especially, the por-ous structure of SiO2 can adsorb the hazardous volatiles generatedfrom wood combustion and thus reduce the emission of smoke.Therefore, it can be expected that a raw decorative paper coatedwith the mixture of TiO2-SiO2 nanocomposite aerogel andmelamine-formaldehyde resin can achieve high smoke suppres-sion when it is used to decorate the surface of inflammablewood-based panel.

In the present study, TiO2-SiO2 nanocomposite aerogel was pre-pared via a sol-gel method and characterized by a series of charac-terization methods to reveal its physical and chemical structure. Itwas further mixed with melamine-formaldehyde resin and coatedin a decorative paper which was subsequently decorated into thesurface of a poplar wood veneer in order to prepare a real indoorpanel for achieving multi-functions of formaldehyde degradationand smoke suppression. Such understanding is essential for thedevelopment of its utilization as the indoor materials of wall, floor,and furniture.

2. Experimental

2.1. Preparation of TiO2-SiO2 nanocomposite aerogel

All reagents and substances used in this study are of analyticalgrade and purchased from a local chemical factory in Nanjing city.In order to obtain TiO2-SiO2 nanocomposite aerogel with uniformstructure, TiO2 sol solution and SiO2 sol solution were prepared,respectively. Acetic acid, distilled water, and 1/3 of absolute ethylalcohol were mixed in order to prepare solution A. Meanwhile,tetrabutyl titanate and absolute ethyl alcohol were mixed to obtainsolution B. Subsequently, solution A was added into solution B witha speed of 60 drops/min and stirred in order to obtain uniform solsolution. The total molar ratio of n(Ti(OC4H9)4): n(C2H5OH): n(H2O): n(CH3COOH) was 1: 18: 3: 0.5. Similarly, SiO2 sol solutionwas prepared under the total molar ratio of n(Si(C2H5)4): n(C2H5OH): n(H2O): n(CH3COOH) = 1: 5: 2: 0.5. The as-preparedTiO2 sol solution and SiO2 sol solution were mixed and stirredunder the molar ratio of n(Ti)/n(Si) = 4. Then, methanamide wasadded into the mixed solution with a molar ratio of n(CH3NO)/[(n(Ti) + n(Si))] = 0.25 and subsequently dispersed using ultrasonicfor 10 min. The mixture was subjected to magnetic stirring untilthe gel solution appears. Absolute ethyl alcohol was used toreplace the water in as-prepared gel solution which was subse-quently placed into the mixed solution (tetraethyl orthosilicate/absolute ethyl alcohol with a volume ratio of 2: 1). Absolute ethylalcohol was used once again to remove the tetraethyl orthosilicate.Finally, the TiO2-SiO2 nanocomposite aerogel was successfully pre-pared after applying supercritical drying method and calcinationfor the appearance of anatase type TiO2.

2.2. Characterization of TiO2-SiO2 nanocomposite aerogel

Fourier transform infrared spectroscopy (FT-IR) was carried outon the NEXUS 870 to study the chemical structure of as-preparedTiO2-SiO2 nanocomposite aerogel. The spectrum was recorded inthe wavenumber region of 400–4000 cm�1 under a resolution of4 cm�1. Scanning electron microscope (SEM) was conducted onJSM-6360LV to observe the surface morphology of TiO2-SiO2

nanocomposite aerogel which was first coated with gold using acoating machine in order to decrease the charging effect. The sur-face morphology was further revealed by transmission electronmicroscope (TEM, Tecnai G220). X-ray diffraction (XRD) was per-formed on an Ultima-IV to investigate the crystalline structure ofas-prepared TiO2-SiO2 nanocomposite aerogel. A Cu Ka radiation(40 kV, 200 mA) was applied to record the diffraction angle of 2hin the range of 10–80� under a step rate of 0.02��s�1. The auto-mated surface analyzer was applied on ASAP 2020 in order toinvestigate the Brunauer-Emmett-Teller (BET) surface area andpore distribution of TiO2-SiO2 nanocomposite aerogel. The N2

adsorption/desorption isotherms were both recorded. The BETsurface area and pore size distribution were calculated anddetermined by applying the BET standard method and Barrett-Joyner-Halenda (BJH) method, respectively.

2.3. Liquid and gaseous formaldehyde degradation

Aerogel was added into the melamine-formaldehyde resinunder a desired mass ratio and dispersed by ultrasonic for 30min. A raw decorative paper was subsequently dipped into themixed solution for 2 min and removed out. Then, a glass rod wasused to remove the excessive mixed solution on the paper surface.Finally, the loaded amounts of the resin and TiO2-SiO2 nanocom-posite aerogels were determined by the difference between rawpaper and the coated one. The coated melamine-impregnated

W. Chen et al. / Construction and Building Materials 161 (2018) 381–388 383

paper was further decorated into the surface of a poplar woodveneer to prepare a real indoor panel via a hot pressing processusing urea formaldehyde resin (UF) as adhesive. The process dia-gram was presented in Fig. 1.

Fig. 2 presents the schematic diagram of the self-designedsealed box and sampling system which were used to evaluatethe photocatalytic activity of coated melamine-impregnated paperon liquid and gaseous formaldehyde degradation. A UV–vis spec-trophotometer (TU1810) was used to determine the photocatalyticactivity of TiO2-SiO2 nanocomposite aerogel on the formaldehydedegradation. The wavelength region was selected from 300 nm to600 nm. Data were recorded every 0.5 nm of wavelength. Thedetailed test method for liquid formaldehyde degradation waslisted as follows: 38% formaldehyde solution (analytical grade)was first diluted into the solution with 5% formaldehyde by addingdistilled water in order to prevent the volatilization of liquidformaldehyde. Then, the solution was transferred into a beakerwhich has the coated melamine-impregnated paper fixed at itsbottle. It was placed into the self-designed sealed box and was irra-diated ceaselessly (0, 2, 4, 6, and 8 h) by applying an ultravioletlamp in order to test the photocatalytic activity of coatedmelamine-impregnated paper on the liquid formaldehydedegradation. Regarding the measurement of the degradation rateof liquid formaldehyde, 10 ml of irradiated solution was extractedfrom the beaker and mixed with 10 ml of both acetylacetone andammonium acetate solution into the conical flask with a stopper.The mixed solution was oscillated and heated in a water bath at60 �C for 10 min. Subsequently, 50 mm cuvette was used to mea-sure the absorbance of the mixed solution at 412 nm of the spec-trophotometer. Similarly, the absorbances after irradiation by theultraviolet lamp for 0, 2, 4, 6, and 8 h were also measured andrecorded. The relation between absorbance and formaldehyde con-centration was determined via drawing the formaldehyde standardcurve as shown in Fig. 3. For the test on gaseous formaldehydedegradation, 1 m2 coated melamine-impregnated paper and 38%formaldehyde solution were both placed in the box. An hour later(liquid formaldehyde was already volatilized completely), a vac-uum pump was applied to sample the gas from the box into thetwo collecting beakers and measure its formaldehyde concentra-tion (C0) which was defined as initial formaldehyde concentration.Meanwhile, an electric fan was applied to balance the pressure of

Raw Papermixed with aerogel

Cim

Popl

Gaseous formaldehyde degradation

Melamine-formaldehyde resin

Fig. 1. The process diag

the box when the vacuum pump is working. The measurementfor formaldehyde concentration was described detailed as follow:the solutions in the two collecting beakers were mixed into a con-ical flask with stopper and oscillated for 10 min. Then, 10 ml of col-lecting solution was extracted and mixed with 10 ml of bothacetylacetone and ammonium acetate solution into the conicalflask with a stopper. The mixed solution was oscillated and heatedin a water bath at 60 �C for 10 min. Subsequently, 50 mm cuvettewas used to measure the absorbance of the mixed solution at412 nm of the spectrophotometer. Similarly, the absorbances afterirradiation by a light source for 8, 16, 24, and 48 h were also mea-sured and recorded. The single factor experiment was applied todetermine the photocatalytic activity of as-prepared melamine-impregnated paper in terms of aerogel dosage (2.5, 5.0, 7.5, and10%), initial formaldehyde dosage (1, 3, 5, and 8 lL of 38%formaldehyde solution), and light source (no light, fluorescentlamp, and ultraviolet lamp with output power of 20 W and 30 W).

2.4. Smoke suppression

As shown in Fig. 1, the poplar wood veneer decorated withcoated melamine-impregnated paper which achieves the highestgaseous formaldehyde degradation rate and the uncoated one wereboth subjected to smoke suppression test by a cone calorimeter. Areal combustion environment was simulated according to ISO 5660standard under a constant irradiation of 50 kW�m�2. The nominalduct flow rate is set at 24 s�1 and the data recording interval is5 s. In order to avoid the appearance of bend and expansion duringcombustion, the testing samples were horizontally placed and cov-ered using a stainless steel grid. The profiles of smoke suppressionsuch as heat release rate (HRR), total smoke production (TSP), COproduction (COP), and CO2 production (CO2P) were processed bythe ‘ConeCale’ software.

3. Results and discussion

3.1. Characterization of prepared aerogel and its photocatalyticactivity on liquid formaldehyde degradation

Fig. 4(a) presents the FTIR spectrum of TiO2-SiO2 nanocompos-ite aerogel. The band at 1628 cm�1 represents the stretching

oated melamine-pregnated paper

Liquid formaldehyde degradation

ar wood veneer

Smoke suppression

ram of this study.

Fig. 2. The schematic diagram of the self-designed sealed box and sampling system: (1) electric fan, (2) sample holder, (3) light source, (4) injection orifice, (5) gas flow valve,(6) drying bottle, (7) gas flowmeter, (8) vacuum pump.

Fig. 3. The linear relationship between absorbance and formaldehydeconcentration.

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vibrations of –OH, which is attributed to the adsorbed water on theSiO2 surface. The absorption peaks at 1069 cm�1 and 802 cm�1 areassigned to the asymmetric stretching of Si–O–Si. The band at954 cm�1 corresponds to the vibration of Si–O–Ti, indicating thatthe cross-reaction occurs during gel process. In addition, theabsorption peak at 635 cm�1 refers to the bending vibration ofTi–O.

Fig. 4(b) shows the XRD pattern of TiO2-SiO2 nanocompositeaerogel. The diffraction peaks at 2h = 25.3�, 37.4�, 48.1�, 54.8�,and 62.9� are observed indicating the presence of typical anatasephase of TiO2, which favors its photocatalytic property.

Fig. 4(c) and (d) depict the nitrogen adsorption-desorption iso-therm and pore size distribution of TiO2-SiO2 nanocomposite aero-gel. Based on IUPAC classification, the aerogel demonstrates thetype IV isotherm which is typical for mesopores. Low absorptionquantity is observed at the relative pressure region of 0–0.1, indi-cating fewer micropores contained in this aerogel. It also can beobserved that the presence of a continuous increasing trend inabsorption quantity and a hysteresis loop implying the prominentexistence of mesopores. Subsequently, a rapid rise in absorptionquantity indicates the presence of macropores. These facts achievethe high BET surface of 186.3 m2/g even after calcination. A broaddistribution of mesopores and macropores is observed in Fig. 4(d),which confirms the analysis results discussed above.

The micromorphology of TiO2-SiO2 nanocomposite aerogel isrevealed by SEM and TEM and the images are presented in Fig. 4(e) and (f). A three-dimensional network structure containingmassive macropores and mesopores are observed, which further

confirms the analysis results of pore size distribution. Moreover,TiO2-SiO2 nanocomposite aerogel consists of massive nanoparticleswhich appear obvious cluster phenomenon.

Fig. 5 shows the UV-vis absorption spectra of TiO2-SiO2

nanocomposite aerogel. It can be observed that adsorption peaksof formaldehyde solution remain at approximately 412 nm. Thisfact indicates the good photocatalytic degradation effect ofTiO2-SiO2 nanocomposite aerogel on liquid formaldehyde. The con-tinuously increasing trend of degradation rate is observed with theUV irradiation time increased. Especially, the spectrum under 8 hUV irradiation demonstrates the highest liquid formaldehydedegradation rate of 65.8%. Massive mesopores in TiO2-SiO2

nanocomposite aerogel lead to the high surface area which pro-vides good adsorption. Moreover, anatase nanocrystal of TiO2 cangenerate OH radicals under UV irradiation which are subsequentlyreacted with formaldehyde. These facts synergistically lead to thehigh degradation rate of liquid formaldehyde.

3.2. Gaseous formaldehyde degradation

Fig. 6 presents the photocatalytic property of poplar woodveneer decorated with coated melamine-impregnated paper ongaseous formaldehyde degradation. Poplar wood veneer demon-strates better photocatalytic property on gaseous formaldehydedegradation with the aerogel dosage increased except for the onewith 10% aerogel dosage. More aerogel dosage can generate moreradicals and provide more reacting contact area resulting in theincrease in photocatalytic reaction rate. These facts lead to theincrease in gaseous formaldehyde degradation rate, while exces-sive aerogel dosage may block the UV visible light and thereforelower the utilization rate of light energy. More aerogel dosagemay also appear cluster phenomenon which blocks the mesopores.In addition, high aerogel dosage will also increase the productioncost. It should be noted that the highest gaseous formaldehydedegradation rate of 56.6% is achieved under the 7.5% aerogeldosage. The same changing tendency of gaseous formaldehydedegradation rate is observed under different initial formaldehydeconcentration. More surface area of aerogel is utilized sufficiently,thus more reactions between photocatalytic radicals and formalde-hyde occur demonstrating the highest formaldehyde degradationrate of 56.6% under the 5 lL initial formaldehyde dosage. Adsorp-tion quantity of formaldehyde molecule on aerogel tends to satura-tion when using excessive initial formaldehyde concentration,which results in the decline in gaseous formaldehyde degradationrate. It also can be observed that more irradiation power of ultra-violet lamp can lead to the higher gaseous formaldehyde degrada-tion rate showing the highest value of 56.6%. Aerogel can absorbmore light energy under higher ultraviolet irradiation power andthus provide more oxidizing radicals for gaseous formaldehydedegradation. Interestingly, the gaseous formaldehyde degradation

Fig. 4. Characterization of TiO2-SiO2 nanocomposite aerogel: (a) FTIR spectrum, (b) XRD pattern, (c) nitrogen adsorption-desorption isotherm, (d) pore size distribution, (e)SEM image with the magnification of 15,000�, (f) TEM image.

W. Chen et al. / Construction and Building Materials 161 (2018) 381–388 385

rates of 7.1% and 20.6% are observed even under no light and fluo-rescent lamp, respectively. This result can be attributed to the por-ous structure of aerogel which leads to physical adsorption ofgaseous formaldehyde molecule. In addition, the photocatalyticproperty of TiO2 needs to be activated by absorbing the wavelengthless than 387.5 nm, which leads to electronic transition and there-

fore forms electron hole with strong oxidizability. Thus, onlyapproximately 5% energy of visible light can be utilized. This factis responsible for the increase in gaseous formaldehyde degrada-tion rate under a fluorescent lamp. It can be concluded that thehighest gaseous formaldehyde degradation rate of 56.6% can beachieved when applying the conditions of 7.5% aerogel dosage, 5

Fig. 5. Uv–vis absorption spectra for liquid formaldehyde degradation.

Fig. 6. The effects of aerogel dosage, initial formaldehyde dosage, and light s

386 W. Chen et al. / Construction and Building Materials 161 (2018) 381–388

lL initial formaldehyde concentrations, and 30 W ultraviolet irra-diation power.

3.3. Smoke suppression

It is well-known that toxic fumes in real fire accident includingcarbon monoxide, nitrogen oxide, and char power can result in thedeath of human life [14]. In this study, a poplar wood veneer,which possesses the advantages of wide source, renewable, cheap,and easy to process, was decorated with only one layer of coatedmelamine-impregnated paper into its surface to prepare a com-monly wood-based panel. A cone calorimeter which can simulatethe environment of a real fire accident was used to investigatethe smoke suppression of this panel. Fig. 7 shows the profiles ofheat release rate (HRR), total smoke production (TSP), CO produc-tion (COP), and CO2 production (CO2P) of the untreated wood-based panel (the panel decorated by melamine-impregnated paperwithout TiO2-SiO2 nanocomposite aerogel loaded) and the coatedone which achieves the highest gaseous formaldehyde degradationrate. Both of the samples show the typical characteristics of wood

ource on the photocatalytic property of decorated poplar wood veneer.

Fig. 7. The profiles of heat release rate (HRR), total smoke production (TSP), CO production (COP), and CO2 production (CO2P) of the untreated wood-based panel and thecoated one.

W. Chen et al. / Construction and Building Materials 161 (2018) 381–388 387

which contains two HRR peaks. The first one corresponds to thegradual flame burning through the direction of sample thickness,while the second peak represents the increased rate of volatilesgeneration from the thin unburned section of sample before theend of flame burning [15]. Significant reduction of 21.4% (firstpeak) and 26.8% (second peak) in HRR was observed for the coatedsample, respectively. Moreover, the initial time of the second peakfor the coated sample is delayed by 154.7 s in comparison tountreated one. Interestingly, the coated sample demonstrates 40s more of the entire combustion time than that of untreated one.All of these facts are related to the incombustibility of TiO2-SiO2

nanocomposite aerogel which can form the stable and closed bar-rier layer, thus prevent the heat and mass transfer. It also can beobserved from Fig. 7(b) that the coated sample possesses lowerTSR value at any combustion time than that of untreated one, espe-cially demonstrating the maximum reduction of TSR value by 9.4%.Significant decrease of CO and CO2 production are also observed forthe coated sample which shows the maximum decrease by 56.2%and 33.2%, respectively. These results are attributed to the porousstructure and high specific surface area of TiO2-SiO2 nanocompos-ite aerogel which adsorbs the hazardous volatile generated fromwood combustion. These facts also evidence that the wood-basedpanel decorated with the coated melamine-impregnated papercan be applied as the indoor materials of wall, floor, and furnituredue to its multi-functions, namely formaldehyde degradation andsmoke suppression.

4. Conclusion

The decorative paper coated with the mixture of TiO2-SiO2

nanocomposite aerogel and melamine-formaldehyde resin demon-strates good photocatalytic activity on both liquid and gaseousformaldehyde degradation (65.8% and 56.6%). Massive mesoporesin TiO2-SiO2 nanocomposite aerogel lead to high surface area forformaldehyde adsorption. Then, anatase nanocrystal of TiO2 cangenerate oxidizing radicals under UV irradiation which are subse-quently reacted with formaldehyde resulting in its degradation.Moreover, the porous structure of TiO2-SiO2 nanocomposite aero-gel can adsorb the hazardous volatiles generated from wood com-bustion and thus reduce the CO and CO2 production by 56.2% and33.2%, respectively. The incombustibility of TiO2-SiO2 nanocom-posite aerogel can form the stable and closed barrier layer duringburning and effectively prevent the heat and mass transportation,demonstrating the maximum decrease in heat release rate by26.8%. The preparation process of melamine-impregnated paperand its coating process onto the surface of wood-based panels havebeen already realized large-scale industrialization. Thus, the prepa-ration process of the coated melamine-impregnated paper in thisstudy can be easily applied on the industrial production. After dec-orated into the surface of wood-based panels (particleboard, fiber-board, and plywood), it can be used as the indoor materials of wall,floor, and furniture due to its multi-functions, namely formalde-hyde degradation and smoke suppression.

388 W. Chen et al. / Construction and Building Materials 161 (2018) 381–388

Acknowledgement

The authors are grateful for the National Key Research andDevelopment Program of China (Grant No. 2016YFD0600702),the Natural Science Foundation of Jiangsu Province (Grant No.BK20161524), the National Science and Technology AchievementsProject in Forestry (Grant No. [2016]42), the Program for 333Talents Project in Jiangsu Province (Grant No. BRA2016381), theDoctorate Fellowship Foundation of Nanjing Forestry University(2015), the Jiangsu Province Ordinary University Students’ Scien-tific Research Innovation Project (KYZZ16_0319), the National Nat-ural Science Foundation of China (Grant No. 31400515), and thePriority Academic Program Development of Jiangsu Higher Educa-tion Institutions (PAPD).

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