Temperature Effect On Performance Of Triboelectric Nanogenerator
FULL PAPERFull Paperswww.aem-journal.comTemperature Effect on Performance of TriboelectricNanogeneratorCun Xin Lu, Chang Bao Han, Guang Qin Gu, Jian Chen, Zhi Wei Yang, Tao Jiang,Chuan He, and Zhong Lin Wang*devices[1–4] is a good choice to solve theenergy crisis. Nowadays, a notable technological trend is the rapid growth of selfpowered electronics for applications incommunication, personal health care,and environmental monitoring, especiallyapplying in harsh environments, such asunder high/low temperature,[5,6] high humidity,[7,8] or corrosive conditions.[9,10] Inrecent years, many studies have proved thatthe TENG is a simple and attractiveapproach for converting ambient mechanical energy into electricity,[11–14] which canbe used as a potentially competitive powersource for self-powered electronic devices.[15–18] It is very important and interesting to explore the effect of temperature onthe electrical performance of TENG, especially when the self-powered electronicspowered by TENG are used in someextreme conditions such as the frigidzones, and desert regions. However, thereare few studies about this temperatureeffect on the output performance of TENG.Although several publications showed thatthe dependence of electrical output ofTENG at different temperature conditions,[19,20] the principle how the temperature affects theelectrical performance of the TENG is still not clear.Here, a TENG which worked in single-electrode mode was usedto reveal the output characteristics of TENG in various temperatureenvironments. Its short-circuit current and output power rangesfrom 1.45 to 0.875 mA and from 0.3943 to 0.1157 W m 2,respectively, under a low working frequency of 3 Hz when thetemperature varies from 20 to 150 C. The affecting principle ofthe temperature on the electrical outputs was investigated bymeasuring the relative permittivity of PTFE sheet, the theoreticalcalculations, and the characterizations of PTFE surface. Theresults proved that the output performance of TENG at differenttemperature conditions is associated with the gaining/storingelectron ability of PTFE sheet. This work will provide a referencefor the application of wearable electronics in harsh environments.The triboelectric nanogenerator (TENG) is a promising energy harvestingtechnology that can convert mechanical energy into electricity and can beused as self-powered active sensors. However, previous studies are mostlycarried out at room temperature without considering the temperature effecton the electrical performance of TENGs, which is critical for the applicationof electronics powered by TENGs in different regions in the world. In thepresent work, a TENG that worked in the single-electrode and contactseparation mode is utilized to reveal the influence of environment temperature on the electrical performance of TENG. The electrical performance of theTENG shows a decreasing tendency, as the temperature rises from 20 to150 C, which is controlled by the temperature-induced changes in the abilityof storing and gaining electrons for polytetrafluoroethylene (PTFE). Thestoring electron ability change of PTFE is attributed to two aspects: one isthe reduction of relative permittivity of PTFE sheet as the temperatureincreases, and the other is the variations of effective defects such as theescape of trapped charges in shallow traps and surface oxidation under theeffect of temperature perturbation. This work can provide useful informationfor the application of TENG in both electric power generation and selfpowered sensors in the harsh environment.1. IntroductionWith the growing threat of limited fossil fuels and relatedenvironmental issues, searching for renewable energy sourcesfrom ambient environment becomes necessary for the sustainable development of human civilization. Harvesting neglectedenergy of the ambient environment to power electronicProf. Z. L. WangSchool of Materials Science and Engineering,Georgia Institute of Technology,, Atlanta, Georgia30332-0245, USAE-mail: zhong.wang@mse.gatech.eduC. X. Lu, Dr. C. B. Han, G. Q. Gu,J. Chen, Z. W. Yang, Dr. T. Jiang,Dr. C. He, Prof. Z. L. WangBeijing Institute of Nanoenergy andNanosystems, Chinese Academy of Sciences,Beijing, 100083, ChinaThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/adem.201700275.Cun Xin Lu and Chang Bao Han contribute equally to this work.DOI: 10.1002/adem.201700275Adv. Eng. Mater. 2017, 00, 17002752. Experimental SectionFabrication of the TENG: The TENG in this work was made up of a Al foil(55 55 1 mm), polyethylene terephthalate (PET) insulation tapes,PTFE sheets (55 55 3 mm). The PTFE sheet is a commercial product1700275 (1 of 8) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.advancedsciencenews.comwww.aem-journal.comthat was purchased from DuPont Company. It was used as one of twofriction layers for its outstanding electronegativity,[21] low frictionalcoefficient,[22,23] and high thermostability.[24] The Al foil that has excellentelectrical conductivity serves as an electrode and another friction layer. Asshown in Figure 1a, the PTFE sheet and Al foil were fixed on twosupporting plates with the help of PET insulation tape. The component ofPTFE and its supporting plate attached to a push rod of linear vibrationgenerator serves as the movable part. The linear vibration generator withtunable frequency and amplitude acted as the vibration source thatprovides the mechanical vibration for the TENG.Electrical Measurement of the TENG: To investigate the electrical outputperformance of TENG devices in various temperatures, the whole devicewas placed in a high-low temperature-testing chamber (Wuxi ZhongTian,GDW-50L). To keep the testing temperature stable, an interval of 10 minwas reserved to re-establish the thermal equilibrium in the chamberduring the test process. Five hundred and forty cycles were performed ateach test to ensure the stability of electric output. The output frequency ofvibration source was set to be 3 Hz. Throughout the testing process, therelative humidity in chamber was controlled within 10 2%. The shortcircuit current, open-circuit voltage, and transferred charge weremeasured by the current amplifier (Keithley 6514, USA), oscilloscope(Agilent DSO-X 2014A, USA) and low-noise preamplifier (Keithley SR570,USA), respectively.Relative Permittivity Test: The relative permittivity of the PTFE sheet wastested through a LCR meter (4263B, Agilent, USA) in a variabletemperature system. Firstly, the PTFE sheet was inserted between twoParallel plate electrodes to form a plate capacitor. Then, the capacitanceswere tested under a frequency of 100 KHz. Finally, the relative permittivityof PTFE sheets was obtained by the parallel-plate capacitor formula.Characterization of the PTFE Sheets: The physical, chemical, andstructural properties of the PTFE surface were studied by the means of IR,SEM, and XPS.Finite Element Method Simulations: In the finite element method(FEM) simulations, we used the “electrostatics” module of COMSOL tocalculate the electric potential distribution through the “stationary”study. First, we constructed the model of TENG used for simulation inthis work. The geometry parameters of the parts of model are as follows:the length and width of both friction materials are 55 and 55 mm,respectively; the thickness of aluminum foil and PTFE sheet,respectively, are 0.4 and 3 mm. The gap between aluminum foil andPTFE is 10 mm. Second, in the “material” section, we selected thealuminum and PTFE materials. The relative permittivity of PTFE was setto be 2.0. Third, the boundary conditions such as the surface chargedensity was be set and the mesh was built on the model by subdivisiontriangular grid. Finally, we could implement the computation to obtainthe electric potential information.3. Result and Discussion3.1. Working Principle of the TENGThe working principle of TENG in one cycle has beenschematically depicted in Figure 1b–e. In this paper, the termsurface is referred to a thin surface layer that thickness is small,compared to the PTFE sheet thickness. Owing to the fact thattwo contacting materials have different abilities to attractelectrons,[25] the surface charge transfer will take place on thecontact interface between Al electrode and PTFE during acontact process. More specifically, the PTFE has higher electronaffinity and higher work function than aluminum,[26,27]negative triboelectric charges would be injected from Al toPTFE sheet, and equal positive charges will be left on Alelectrode during the contact process shown in Figure 1b. Otherworks have revealed that dielectric materials such as PTFEcould keep charges for a long time.[25,28,29] The negative chargeson the PTFE sheet could induce positive charges on the Alelectrode. The positive inductive charges on the Al electrodewill be reduced when the PTFE sheet move upwards to add thedistance between two materials, as shown in Figure 1c. Thedecrease in positive induced charges on the Al electrode can beunderstood as a consequence of being counteracted by sameamount of electrons that flow from ground to Al electrodethrough external circuit. Figure 1d describes the inductivecharges on the Al electrode is reduced further as the distancebetween two materials continues to augment. On the contrary,Figure 1. a) Schematic diagram of experimental set-up. b–e) The working principle of the TENG during one cycle: b) The PTFE sheet contacted with theAl electrode. c) The PTFE sheet move upwards to add the distance between two materials, and the positive inductive charges on the Al electrode to bereduced, causing the negative charges to flow from the ground to the Al electrode. d) The PTFE sheet continues to move upwards further until thepositive inductive charges on Al electrode decreased to minimum value. There is no charges to flow. e) The PTFE sheet move downwards to reduce thedistance between two materials, causing negative charges to flow from the Al electrode to the ground.Adv. Eng. Mater. 2017, 00, 17002751700275 (2 of 8) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.advancedsciencenews.comwww.aem-journal.comthe inductive charges on the Al electrode is increased as thePTFE sheet move downwards to diminish the distance betweentwo materials, as shown in Figure 1e. The electrons will flowfrom Al electrode to ground through external circuit. Therefore,the output current, whose direction relies on the mechanicalmotion direction, can be formed by the flow of induced chargeson the Al electrode.3.2. The Electrical Performance of TENG Under VirousTemperature ConditionsFigure 2 illustrates the electrical performance of TENG,including the short-circuit current (Isc), open-circuit voltage(Voc), and short-circuit transferred charges (DQsc). Figure 3a–cillustrate the Isc, Voc, and DQsc of TENG signal curves at 20, 10, 0, 20, 60, 100, 130, and 150 C, respectively. It showsintuitively that the electrical output of TENG could stay stable ateach temperature point. Figure 2d–f, respectively, shows that theVoc, Isc, and DQsc decrease with the augment of temperature from 20 to 20 C. Although the Voc and Isc have a tendency of smallincreasing when the temperature changes from 20 to 60 C, theycan be regarded as keeping stable in the whole temperaturerange of 20–100 C, but drop rapidly when the temperaturegrows continuously, as shown in Figure 2d and e, respectively.This result is consistent with Wen’s study19. Figure 2f shows thatDQsc increases as the temperature rises from 20 to 60 C, butdecreases rapidly when the temperature is over 100 C or below20 C.3.3. The FEM Simulation Result and Relative Permittivity ofPTFEThe relative permittivity of PTFE sheet is a function oftemperature shown in Figure 3a. The measurement of PTFE’srelative permittivity is accordant with results ofprevious researches.[30,31] For a nonpolarity soliddielectric such as PTFE sheet, the variation ofrelative permittivity will be caused by thermalexpansion according to the Clausius–Mossottirelation. The inset of Figure 4b shows theschematic diagram of utilizing the TENG tocharge a capacitor through a rectifier bridge. Thehigher the temperature, the lower chargingvoltage of capacitor becomes within a samecharging time, as described in Figure 3b.Additionally, the space potential distributionbetween the PTFE and the Al electrode had beensimulated when the TENG works at differenttemperatures of 20, 20, 60, and 150 C, asshown in Figure 3c–f, respectively. The maximum of electric potential can be reached to 825 V( 20 C), 700 V (20 C), 720 V (60 C), and 400 V(150 C). It indicates that the temperature maystimulate the surface electric potential to decay.The variation trend of simulation results issimilar to the measured result shown inFigure 2d.As discussed above, the temperature indeedaffects the electrical performance of TENG. Tworeasons that contribute to this temperatureinduced effect are as follows.3.4. The Theoretical CalculationFigure 2. a–c) Show the electrical signal curves of short-circuit current (Isc), open-voltage(Voc), and short-circuit transferred charges (DQsc), respectively, at 20, 10, 0, 20, 60, 100,130, and 150 C. The inset in Figure 3a–c shows, respectively, the enlarged view of Isc, Voc,and DQsc at 20 C. d–f) describe, respectively, Isc, Voc, and DQsc in the temperature range of 20–150 C.Adv. Eng. Mater. 2017, 00, 17002751700275 (3 of 8)Firstly, as we know, the permittivity of a mediumdescribes how much electric field is generatedper unit charge in that medium, which alsomeans the ability of storing charges in materials.Therefore, the diminution of relative permittivitywill reduce the number of electrons stored on thePTFE surface. There are many [32–35] The volume charge density on thePTFE sheet during the process of metal-insulator 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ity and relative permittivity of PTFE on thecharge density of PTFE surface.Due to the principle of charge conservation,the same amount of positive charges will beinduced on the Al electrode when two materialscontact together. Therefore, we can calculate theelectric surface density (sAl) on the Al electron,Zs Al ¼ lts p ðxÞdx 11 2 1 ¼ ðfP fAl ÞðeN t Þe0ð2ÞThen, the quantity of charges DQAl could bedescribed by,DQ Al ¼ Ss Al tÞ¼ SðfP fAl ÞðeN1 2 1 1eð3ÞWe assumed the electric charges on the Alelectrode will transfer totally through externalcircuit to form short circuit current, so theamount of transferred charges (DQsc) can bedescribed by t Þ1 2 1 1DQ sc ¼ Q Al ¼ SðfP fAl ÞðeNeFigure 3. a) Shows the relative permittivity (er) of PTFE sheet as the function of temperatureranging from 20 to 150 C as its test frequency is 120 Hz. b) The charging for a capacitor(50 V, 2 mF) with the load resistance R (510 V) at various temperatures within 300 s. Theinset shows the Schematic circuit diagram of TENG for charging a capacitor through a fullbridge rectifier. c–f) Finite-element simulation about the space potential distribution ofTENG and its color gradient bar with different potential values under different temperatures:c) 20 C, d) 20 C, e) 60 C, and f) 150 C. The up-plate is Al elctronde, the down-plate isPTFE sheet. The deeper red color (or blue color) is, the more positive (or negative) the spacepotential is.contact electrification is given by Chowdry and Westgate,[36] t ðfAl fP Þexpð xÞ t VðxÞ ¼ qNs P ðxÞ ¼ q2 Nlt lt ¼e tq2 Nð1Þ 1n2where, V(x) is the electric potential on the PTFE sheet, lt is theDebye length, q is the electron charge, the sp is the volume t ð cm3 eVÞ is the volume defectscharge density of PTFE, Ndensity in unit energy. Here, the term defect is referred to thoseeffective traps that can be occupied by electrons. The ФAl and Фpare the work function of the Al and PTFE, respectively. Thechosen model, in this paper, is a simple and approximate model,that is, suitable for this paper to explain the effect of defectAdv. Eng. Mater. 2017, 00, 1700275ð4ÞTo our best knowledge, the work function of Aland PTFE is 4.30 and 5.75 eV, respectively.[37] Byquantitatively fitting the experimental data, wecan obtain a nonlinear fitting equation of therelative permittivity of PTFE, as shown inEquation 5 and its numerical fitted curve isshown in Figure 4a.er ¼ 5:86037 10 8 T 3 þ 8:38492 10 6 T 2 7:02889 10 4 T þ 2:05ð5ÞThe amount of transferred charges (DQsc) areinfluenced by the temperature-induced changes t from theof relative permittivity and effective traps density NEquation 4. First of all, only the temperature effect on relativepermittivity of PTFE was taken into regarded and the influence t on (DQsc) was ignored, we takeof effective traps density N t ¼ 1:3 10 5 ðcm3 eVÞ. Therefore, from Equations 4 and 5,Nthe relationship between DQsc and T could be described byDQ sc ¼ 28:747 ð 5:86037 10 8 T 3 þ 8:38492 10 6 T 2 17:02889 10 4 T þ 2:05Þ2 10 9 Cð6ÞFrom Equation 6, the relation curve between the transferred t ¼ 1:3 charges and temperature can be achieved by taking N 5310 ðcm eVÞ shown in Figure 4b, which is basically accordantwith the measurement of short-circuit transferred charges. Thedifference of theoretical calculation and experimental measurement of transferred charges may be the temperature-induced1700275 (4 of 8) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
act/friction electrification.[36] We suppose theeffect of temperature perturbation would declinethe stability of charges so that the magnitude ofcharges on the PTFE thin layer of surface wouldbe reduced base on the theoretical calculations.And the more and more defects that can beoccupied may be reduced owning to reduction ofdangling bonds of the PTFE surface.3.5. The Characterization of PTFE SheetsThe SEM images of PTFE sheet after the TENGworked at different conditions are shown inFigure 5. There are more and more flaking offthin sheets or small debris on the worn PTFEsurface as the temperature rises. More and moreflaking off thin sheets indicate that the intermolecular bonding force of PTFE become weakereven chemical bonds rupture. The abrasionresistance of PTFE get worse when the temperature rises.[38]Secondly, the FTIR spectra of PTFE sheet afterFigure 4. a) The curve of nonlinear fitting equation of the relative permittivity of PTFE sheet. friction with the Al electrode at various temperb) The theoretical calculation of transferred charges of TENG at various temperatureatures is illustrated in Figure 6a. Figure 6b showsconditions (Nt ¼ 1.3 10 5/cm3 eV), only the temperature effect on relative permittivity of that the absorption bands appear at 773 andPTFE was taken into regarded. c) The coefficient sensitivity of DQsc to T, which is just 793 cm 1 owing to the presence of groupcontributed by the temperature indcued changes of relative permittivity of PTFE. d) The CF O.[39,40] As shown in Figure 6c, three2DQsc of TENG under the combined effect of er and Nt.absorption bands which reveal the asymmetricstretching vibration and stretching vibration of CF2 appear at about 1100–1300 cm 1 when thechanges of the number of effective traps. Therefore, S(DQsc, T), thetemperature is below 70 C, but they gradually become a singlesensitivity coefficient of DQsc to T, can be defined by using the ratiowide absorption peak when the temperature increase fromof relative change of both DQsc and T,SðDQsc; TÞ ¼dDQscT dTDQscS(DQsc, T) 0 means that the growingtemperature will cause the increase in DQsc. Incontrast, S(DQsc, T) 0 indicates that DQsc will bereduced as the temperature rises. For example, S(DQsc, T) is 0.1 when temperature is 140 C, andit means that 1% increase in temperature willlead to 10% decrease of DQsc. There is a littleincrease of DQsc in the temperature range of40–85 C, but the DQsc drops rapidly when thetemperature is above 90 C or below 40 C, shownin Figure 4c. It is accordant with the profileshown in Figure 2f. tIn addition, the DQsc is also related to Naccording to Equation 3. The electrical output of t is shown inTENG as a function of er and N tFigure 4d. It implies that the decrease of er and Nwill weaken the PTFE’s ability of bound electronsduring the triboelectrification process. Thetriboelectric charges on the PTFE just aregenerated on the several hundred nanometersthin layer of the PTFE surface during a process ofAdv. Eng. Mater. 2017, 00, 1700275Figure 5. SEM photographs of the PTFE and flaking off thin sheets (as the pointing ofarrows). a) is the photo of primitive PTFE without friction. And the PTFE after friction 10 minwith Al electrode at different temperatures: b) 20 C, c) 30 C, d) 150 C.1700275 (5 of 8) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
orine atoms or combine with the danglingbonds of C atoms on the PTFE surface, which is atype of the electron traps. This is a process thattemperature accelerate the surface oxidation anddefluorinate on the PTFE surface, which may addthe antistatic propensity of the polymers.[44,45] Asthe electron affinity of fluorine is stronger thanoxygen, the molecular chains occupied by oxygenatoms would attract fewer electrons than theintact molecular chains. Besides, the molecularweight of PTFE would increase when the fluorineatoms are replaced largely by oxygen atoms. Theincrease of molecular weight will cause thedecrease of relative permittivity of PTFE surfacethin layer, according to the Clausius–Mossottirelation. For the reasons given above, the abilityof PTFE about storing and gaining electrons willbecome weaker, so that result in the decreasedelectrical output of TENG along with thetemperature rising.Figure 7a and b, respectively, demonstrates theO 1 s and C 1 s peaks of PTFE characterized byFigure 6. a) The FTIR absorption spectra of PTFE versus various temperatures (30, 50, 70, XPS. As shows in Figure 7b, a shift of bonding90, 110, 130, and 150 C, respectively). The absorbance peak from: b) 600 cm 1 to 900 cm 1, energy can be evaluated to about 0.4 0.2 eV foreach oxygen atom and is roughly additive with thec) 1050 cm 1 to 1800 cm 1, d) 2250 cm 1 to 2450 cm 1.augment of temperature (C 1 s (2) at a bindingenergy Eb ¼ 292.5 eV). The binding energy shift70 C. This changes of the absorption peaks may be interpretedof C 1 s (2) is due to an inductive effect, which is dependent onas the relaxation of PTFE crystal and the regular spiral chain ofthe number of O atoms replaced position of F atoms andPTFE turning into irregular winding due to the effect of thermalcombined with dangling bonds of C atoms. As we know, theperturbation. Figure 6d shows two absorptionpeaks appear at 2350 cm 1 (O55C55O) and2383 cm 1. But, the two absorption peaksgradually turn into a big single peak (nearby2350 cm 1). It indicates the PTFE surface wouldabsorb more and more CO2, when the temperature rises from 30 to 150 C. The carbonyl groupis observed at 1700–1800 cm 1 (C55O stretching),720 cm 1 ( CF2 scissoring).[41] The absorptionpeak at 1790 cm 1 has been identified as olefinend group CF55CF2[42] shown in Figure 6c.As shown in previous research,[31] the abovereactions analogous to those encountered inhydrocarbon oxidation that can occur on theeffect of electric field in the air, such as CF2 þ O2 ! CF2 O2 ! CF2 O CF2 CF2 CF2 þ O2 ! CF2 CF2 COF þ FThe electron traps on the PTFE are mainlyattributed to quantities of F atoms existing on thesurface of PTFE due to its molecular chain with Catoms surrounded by F atoms spirally.[43] According to the IR absorption spectra of PTFE, wecould know that the dangling bonds on the PTFEsurface will react with the oxygen-containingelectron acceptors in the air to form variousoxygen-containing groups. This means that theoxygen atoms may occupy the positions of someAdv. Eng. Mater. 2017, 00, 1700275Figure 7. The XPS narrow scan spectra of four PTFE samples under different treatments: a)The O 1 s peak and b) the C 1 s peak under different conditions: the primary PTFE samplewithout contact or friction under 30, 90, and 150 C. c) and d) demonstrate, respectively, theO and C peak fitting of XPS spectra of PTFE after a friction process under150 C environment.1700275 (6 of 8) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
e 1. Surface elementary compositions of the PTFE sheets: Primarysample (without friction or contact), and the sample contacted with anAl electrode under 30, 90, and 150 C.Elementary composition [%]Supporting Information is available from the Wiley Online Library or fromthe author.Atom ratio [%]ConditionC 1sO 1sF 1sC/OF/CPrimary sample33.931.2264.5827.811.9030 C37.542.2059.8917.061.6090 C41.152.8455.6014.491.35150 C41.74.6353.379.011.30magnitude of electronegativity ranks in following order:F O C. Owing to the difference of electronegativity betweenoxygen and fluorine, the ability of oxygen to attract electron isweaker than fluorine. Therefore, the PTFE attract less and lesselectrons during the friction process with the increase oftemperature. Figure 7c and d show, respectively, the O and Cpeak fitting of XPS spectra of PTFE sheet contacted verticallywith Al electrode at the temperature condition of 150 C. Thebinding energy of C (1 s) in those chemical groups will be284.6 eV (C C), 292.5 eV ( (CF2 CF2) n),[46,47] 286.45 eV(C O C),[46] 294.1 eV ( CF3), 298.2 eV (O C55O), and288.5 eV (C O).[41] Table 1 (please see the Supporting Information for detail) describes the surface element compositions fromthe XPS data for PTFE sheets. The surface oxygen concentrations were in the range of 1.22–4.63%. The atom ratio of F/Creduces gradually, when the temperature rises during thefriction process. This fact gives clear indication that the fluorineatoms are replaced by oxygen to form oxygen-containingchemical bonds. Namely, defluorination or surface oxidationis stronger with the increase of temperature. Thus, it means thatmore and more chemical groups occur on the surface of PTFEwith the temperature growing. From the above analysis, theincrease of oxygen-containing groups is possibly another factorthat affects the electrical output performance of TENG.AcknowledgementThis research is supported by the “Thousands Talents” Program forPioneer Researcher and His Innovation Team, China, the National Key R& D Project from Minister of Science and Technology (2016YFA0202704),National Natural Science Foundation of China (Grant No. 51432005,5151101243, 51561145021, 61504009, and 51608039).Conflict of InterestThe authors declare no conflict of interest.Keywordsrelative permittivity; surface electron traps; temperature effect;triboelectric nanogeneratorReceived: March 27, 2017Revised: May 26, 2017Published online:[1][2][3][4][5][6][7][8][9][10][11]4. ConclusionIn summary, the effected temperature performance of TENG wasinvestigated experimentally and numerically in a variabletemperature system. It is found that electrical output performancesuch as short-circuit current, open-circuit voltage, and short-circuittransferred charge of the TENG decrease with the augment oftemperature from 20 to 20 C. Although the short-circuit currentand open-circuit voltage have trends of small increasing when thetemperature changes from 20 to 60 C and then decrease a little,they can be regarded as keeping stable in the whole temperaturerange of 20–100 C, but drop rapidly when the temperature growscontinuously. The variations in relative permittivity of PTFE,which means that its ability of storing charges show similarvariation patterns to the electrical output of TENG. Based on theexperiment and the theoretical analysis, the changes of relativepermittivity and effective defects on the PTFE surface arecontributed to this temperature-induced effect as the temperatureincreases. This work could provide meaningful information for theapplication of TENG in both power generation and self-poweredsensing in the harsh environments.Adv. Eng. Mater. 2017, 00, 1700275Supporting ][22][23][24]N. S. Lewis, Science 2007, 315, 798.M. S. Dresselhaus, I. L. Thomas, Nature 2001, 414, 332.Z. L. Wang, W. Wu, Angew. Chem. 2012, 51, 11700.X. Chen, C. Li, M. Gratzel, R. Kostecki, S. S. Mao, Chem. Soc. Rev.2012, 41, 7909.M. A. Fonseca, J. M. English, M. Von Arx, M. G. Allen, J.Microelectromech. Syst. 2002, 11, 337.E. Birdsell, M. G. Allen, Solid-State Sens. Actuators Microsyst.Workshop 2006, 6, 212.K. Takahata, Y. B. Gianchandani, Sensors 2008, 8, 2317.E. L. Tan, W. N. Ng, R. Shao, B. D. Pereles, K. G. Ong, Sensors 2007, 7, 1747.Z. Wang, L. Cheng, Y. Zheng, Y. Qin, Z. L. Wang, Nano Energy 2014,10, 37.Y. Yu, G. Qiao, J. Ou, IEEE Sens. J. 2010, 10, 1901.M. Han, X.-S. Zhang, X. Sun, B. Meng, W. Liu, H. Zhang, Sci. Rep.2014, 4, 4811.M. Ha, J. Park, Y. Lee, H. Ko, ACS Nano 2015, 9, 3421.W. Tang, C. B. Han, C. Zhang, Z. L. Wang, Nano Energy 2014, 9, 121.J. H. Kim, J. Chun, J. W. Kim, W. J. Choi, J. M. Baik, Adv. Funct. Mater.2015, 25, 7049.X. H. Li, C. B. Han, T. Jiang, C. Zhang, Z. L. Wang, Nanotechnology2016, 27, 085401.P. Song, S. Kuang, N. Panwar, G. Yang, D. J. H. Tng, S. C. Tjin,W. J. Ng, M. B. A. Majid, G. Zhu, K. T. Yong, Adv. Mater. 2017, 29,1605668.R. Hinchet, S.-W. Kim, ACS Nano 2015, 9, 7742.B. Saravanakumar, S. Soyoon, S.-J. Kim, ACS Appl. Mater. Interfaces2014, 6, 13716.X. Wen, Y. Su, Y. Yang, H. Zhang, Z. L. Wang, Nano Energy 2014, 4, 150.Y. Su, J. Chen, Z. Wu, Y. Jiang, Appl. Phys. Lett. 2015, 106, 013114.C. A. Chang, Y. K. Kim, A. G. Schrott, J. Vac. Sci. Technol. A: Vac. Surf.Films 1990, 8, 3304.H. Unal, A. Mimaroglu, U. Kadıoglu, H. Ekiz, Mater. Des. 2004, 25, 239.S. K. Biswas, K. Vijayan, Wear 1992, 158, 193.D. W. Brown, L. A. Hymo, D. Michaelsen, J. Res. Natl. Bur. Stand.1954, 53, 121.1700
separation mode is utilized to reveal the influence of environment tempera-ture on the electrical performance of TENG. The electrical performance of the TENG shows a decreasing tendency, as the temperature rises from 20 to 150 C, which is controlled by the temperature-induced changes in the ability
4.3.1 Effect of Temperature at pH 4.5 57 4.3.2 Effect of Temperature at pH 5.0 58 4.3.3 Effect of Temperature at pH 5.5 59 4.3.4 Effect of Temperature at pH 6.0 60 4.3.5 Effect of Temperature at pH 6.5 61 4.3.6 Combination Effect of Temperature on Enzymatic Hydrolysis 62
Effect of temperature on nitrification kinetics 4 Effect of pH on nitrification kinetics . 5 Results and discussion 6 Effect of temperature on nitrification kinetics 6 Effect of pH on nitrification kinetics 13 Summary and conclusions 16 Literature cited 17 Appendix A: Data collected for the temperature experiment . . 21
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temperature sensors. The LogTag Temperature Data Logger measures and stores up to 7770 temperature readings over -40 C to 99 C (-40 F to 210 F) measurement range from a remote temperature probe. Statistical temperature and duration readings for up to 30 days can be reviewed on the display. The visual display of current temperature
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shrinkage which are directly depending on the effect of temperature. In this paper it is discussed about the effect of temperature gradient for continuous beams of various spans and the flexural moment developed in the structure due to positive and negative temperature gradient using MIDAS Civil analysis software.
