Calculation of the coefficient and dynamics of water diffusion in graphite joints Calculation of the coefficient and dynamics of water diffusion in graphite joints

Calculation of the coefficient and dynamics of water diffusion in graphite joints

  • 期刊名字:哈尔滨工程大学学报(英文版)
  • 文件大小:318kb
  • 论文作者:WANG Jun,LIU Wen-bin
  • 作者单位:College of Chemical Engineering
  • 更新时间:2020-07-08
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论文简介

Journal of Marine Science and Applicaion, Vol. 5 ,No. 2 ,June 2006 ,pp.65 -70Calculation of the coefficient and dynamics of water diffusionin graphite jointsWANG Jun and LIU Wen-binCollege of Chemical Engineering , Harbin Eninering Uniersity, Harbin 150001, ChinaAbstract: The coefficient and dynamics of water diffusion in adhesive- graphite joints were calculated in-situ with energy dispersive X-ray ( EDX) analysis, a method that is significantly simpler than elementalanalysis. w ater diffusion cofficient and dynamics of adhesive-graphite joints treated by different surfacetreatment methods were also investigated. Calculation results indicated that the water diffusion rate inadhesive-graphite joints treated by sandpaper was higher than that treated by chemical oxidation or bysilane couple agent. Also the durability of graphite joints treated by coupling agent is superior to thattreated by chemical oxidation or sandpaper burmishing.Keywords: adhesive -graphite joints , difusion coffcient, difusion dynamics, energy dispersive X-ray(EDX)CLC number :063 ;TQ43 Document code: A Article ID:1671 - 9433(2006)02 -0065 -061 Introductionthat water is adsorbed and diffuses in the cohesive andinterfacial regions. Water may penetrate and affect theCompared with traditional joining methods such as rive-adhesive joints by one or a combination of the followingting and bolting, adhesive technology can simplify as-processes'! : diffusion through the adhesive , transportsembling processes, increase productivity and quality ,along the interface ; capillary action through cracks andas well as reduce production cost. Therefore it hascrazes within the cohesive layer; diffusion in the layer;been widely used in modern shipbuilding engineering,and molecular interactions. The water penetration insuch as sealing of deck and other places, adhesivecohesive layer leads to swelling; migration of reactionbonding of inner-decorations, oil filtration, and adhe-products from interior to surface; and degradation ofring between stern shaft and shaft slee. The bene-adhesives. Water can permeate into majority of poly-fits related to using adhesives ensure that adhesivemers due to its strong osmosis; weakening the interac-technology will continue to grow as a part of the engi-tion among polymers,consequently decreasing polymerneering design and manufacturing process.performance. Bowditch4I investigated the effect of wa-ter on the adhesive itself. Loh' 5 J investigated environ-Environmental factors including moisture and tempera-mental degradation of the interfacial fracture energy inture greatly affect adhesive degradation in both the co-n adhesively bonded joint. Comyn 61 systematicallyhesive and interfacial regions of ships navigating in theanalyzed the dynamics process of water diffusion intosea. The adhesive degradation can result in a changepolymer, but only invetigated static diffusion. In fact,in mechanical properties between adhesives and materi-water concentration varies with time in any position ofals ( metals or nonmetals),, thus shortening the adhe- adhesive layer. Other research focus mostly on environ-sive/ 'materials joint life' 21 。Therefore adhesives shouldmen中国煤化工sive-metal or metal-have good adhesion strength and durability, stronglyadhe|YHCNMHGthedurabilityofad-depending on wet and heat resistance. Studies of thehesives have been presented'- 9 . Detailed research onwet and heat aging process of adhesives demonstratethe preparation of adhesives for graphite/ adhesive/Reeved data:2005 -11 -14.●66●Journal of Marine Science and Application , Vol.5 ,No.2 , June 2006graphite joints are scarce, especially on the durabilitycoupling agent.of the adhesive joints.Adhesives were applied to the surface of the aboveIn this work , the increase of water content in graphitetreated graphite joints, and cured at 130C for 3 hoursadhesive joints was calculated in-situ using energy dis-under the pressure of 0.15 ~ 0.3 MPa. The obtainedpersive X-ray spectroscopy ( EDX) and elemental anal-adhesive-graphite joints were cured at room tempera-ysis method, from which the diffusion coefficient andture for 24 hours, then heated at 55 ,65 ,and 75 C un-diffusion dynamics of water in graphite adhesive jointsder a relative humidity of 98% ~ 100% for humidifica-under moisture and heat aging process were obtained.tion and aging in a humidifying and aging equipmentCompared with elemental analysis method, the EDX a-(HL-2, Harbin Instrument Corp.,China).nalysis method does not break the adhesive bondingjoints, making the calculation of the diffusion coeffi-2.3 Sample analysiscient and dynamics of water in the adhesive joints veryEDX analysis on the joint samples was performed witheasy and resulting in fewer errors. Moreover, water dif-an ISIS-300 energy dispersive X -ray spectrometerfusion dynamics in adhesive bonding joints subjected to(Link Corp.,USA) with the depth of observation ofdiferent suface treatments were also determined in this20nm. Elemental analysis of the samples was carriedstudy. Results of experiments show that the durabilityout on PE2400 equipment (PE Corp., USA). Allof graphite adhesive joints treated by silane couple a-tests were conducted at room temperature after 24 hoursgent is better than that treated by chemical oxidationof preparation. Each piece of data was based on an av-and by sand paper bumishing, respectively , indicatingerage value of ten samples. Standard deviation of thethat methods of surface treatments are of great impor-data was 10% .tance for preventing water diffusion.2.4 Calculation methods of the speed of wateruptake2 Experiment2.4. 1 EDX analysis method2.1 MaterialsThe water uptake of the adhesive was caleulated withThe adhesives consisting of a thermosetting phenolicEDX. If the water diffusion speed in the adhesive is .resin modified by polyphenylmethyl siloxane werepresumed to be constant, water uptake formula of thehomemade. Graphite joints were from the Tianjin Ele-adhesive is described as follows:gant Carbon & Graphite Co. , Ltd.c" =(cxr-co)xM(1)2.2 Adhesion processwhere, c" is the water uptake in the adhesive joints. cPrior to adhesion, the graphite surface was treated u-is the percentage of oxygen element in the total of car-sing dfferent methods: 1 ) sandpaper burnishing treat-bon and oxygen elements in the adhesive, which wasment: burnished by #80 sandpaper; 2) chemical oxida-obtained with EDX. Co is the uptake of oxygen elementtion treatment: burmished by #60 sandpaper, heated atin the adhesive before aging, r is the sum of carbon80C for 0.5 hours in an oxidizing reagent (K2Cr20, :and oxygen elements in the adhesive before aging. InH2SO&: H20=1 :3 : 10),washed by water, andthis study, Co is 7%,r is 89. 06%,both were deter-dried; 3) silane coupling agent treatment: burnishedmined by chemical structure characteristics of the ad-by #60 sandpaper, heated at 80C for 1 hour in an oxi-hesiv中国煤化工analysis. Mno anddizing reagent ( K2Cr2O2: H2SO2:H20=1 :3: 10),MoYHCNMHGand oxygen, respec-washed by water, dabbed by covered with silane cou-tivelypling agent ( H2 NCH2 CH2 CH2Si (OC,H3)3), and .then heated at 150 C for 1 hour. If not specified, thesurface of the graphite joints was all treated by a silane.WANC Jun.at a:Calaion of the ofion and drnamio of waler dfusion in goaphie joints.67.2. 4.2 Elemental analysis method( =20mm) is the widh of the joints because the difu-The water uptake of the adhesive is calculated with ele-sion is considered to be one dimensional. Accordingly,the difusion coficient D can be calculated using EDXmental analysis :and elementary analysis.c"= (c'-co) xMu2O(2)M。where, c' is the uptake of oxygen element in the adhe-2.5. 2 Calculation of water difusion dynamics in theadhesive jointssive joints, which was obtained with elemental analy-sis. Other symbols are the same as equation (1). .Because of the lack of more mechanistic descriptions,2.5 Calculation foundation of difusion eoffcientthe relation between the difusion dynamics and activa-tion energy is usually described by the following equa-and diffusion dynamicstions:2.5. 1 Calculation of water difusion cofficienti =f(c),f(c) =c",(7)By Fick's Second Law, diferential mass transfer equation of water diffusion at different direction is ex-h = Ae前,(8)pressed as:kC公=exp*[-中一划小(9)=D(影+影+导).(3)In equation (7), c is the water uptake in the adhesivewhere, C is the concentration of water, D is the diffu-joints at time t, k is the difusion rate constant, n ission coefficient, aC/ ax is the concentration gradient ofthe difusion reaction order, t is the diffusion time. E-waler, x is the difusion distance, and t is time. Waterquation (8) is the Arrhenius formula, where, E isdiffusion process in the cohesive joints is considered todifusion actiation energy,A is the Arrhenius fre-be unsteady molecule diffusion in finite thick medium.queney factor, R is the universal gas constant,and TOnly mass difusion caused by concentration diferenceis temperature. The difusion rate constant k can beis discussed here; free difusion arose by heat move-determined from the relation of the water uptake in thement was not considered. Assume diffusion cefficientadhesive and time I in Equation (8). If the plots ofand polymer volume are invariable in all diffusionIn(1/c) against time are linear, the difusion processprocess, and no chemistry reaction occurs, then theis one order, therefore, h can be calculated from themass transfer equation (3) is simplfed to equationslopes of the straight lines. Finally , water difusion ac-(4) at x axis direction.tivation energy can be determined from Equation (9).aC_ paCaax2“If equilibrium between the bath and the surface of the3 Results and discussionfilm is established instantaneously upon immersion, in-3.1 The relation between water uptake andtegration of equation (4) yields equation (5)[5,9]:aging time(5)The dependence of the water uptake of the adhesives injoints upon aging time was measured. The results areasshown in Fig.1 to Fig.6. The joints were treated by si .D=πb2 ((6)lane coupling agent, sandpaper burmishing, and chem-(些x).In these equations, Sc and Cmax is the water uptake of中国煤化工adhesives at time t and after saturation, respectively. bTYHCNMH G●68.Joumal of Marine Science and Aplicaion . Vol. 5 ,No. 2, June 20066.66.+ 55C, RH 98~100%- ssC, RH 98~100%- ssC, RH 98-100%+ 66C" RH 98- 100%+ 66C,RH98-100%一662' RH98-100%士75C, RH 98- 100% .6.4士75C, RH 98~ 100%←75C, RH 98- 100%E6.0E60点6.05.5.'5.430060900 120050300~ 450 60050 300450 600 750Aging time/h(a) Silane coupling agent(b) Sand paper burnishing(C) Chemical oxidationFig.1 Plots of In( 1/c) against humidity aging time al diferent suface treatment using EDX6.26.4.6.0当6.上*6.05.8-5.6-300 600 900 1200150300450 6000150300450600750_Aging timehFig.2 Plots of ln(1/c) against aging time at dfferent surface treatment using elemental analysisIt can be seen that most of the curves in these figuresthe slope of the plots.are nearly linear. It shows that the water diffusion3.2 Calculation of water diffusion coefficientsprocess in the cohesive joints obeys Fick’ s secondTable 1 gives the values of water diffusion coefficient inlaw. Hence, water diffusion coefficient and diffusionthe adhesives in the joints.rate constant can be calculated using equation (6) andTable 1 Water difusion coefficients in the adhesive joints at different humidity temperaturesWater difusion eoffcients D /10 -12m2. h-'Surface treatmentTemperature/CEDX analysisElemental analysis5:1.5231. 559Silane coupling agent6:2. 7732. 7997:10.57411. 4321. 6981.715Chemical oxidation2. 8992.9147513. 84114. 998中国煤化工7Sandpaper burnishing65YHCNMHG18. 19218. 746WVANG Jun, et al:Calculation of the cofficient and dynamics of water difusion in graphite joins.●69.It can be seen that the values of water diffusion coeffi-listed in Table 2 and Table 3, respectively.cient calculated with the EDX method are close to, butslightly smaller than that calculated with the elementalTable 2 Diffusion rate constant at different temperatureSurfaceDifusion rate constant/ x10-* .s-'analysis method. The reason is that the detection depthtreatment T/CEDX analysis Elemental analysisof EDX spectrometer is limited to 20 nm down to themethodsadhesives surface. In fact, the distribution of water551. 5231. 559silane coupling2.' 7732. 799within the adhesives is non-uniform due to the diffusionagent7510. 57411. 432.gradient, so the water content near the joint ' s surface1. 6981.715is higher than that in the bulk of the adhesives. In ad-chemical652.8992. 914oxidationdition, a small amount of water retained in the capillar-13.84114.998y micro-pore of sample near surface region was vapor-s52.1782.347sand paper3. 1343.578ized during the spraying gold treatment carried out un-burnishing18. 19218. 746der vacuum. As a result, the water content within thenear surface region is lower than real values. There-Table 3 Water diffusion activation energy in the jointsfore, the diffusion cofficient calculated by EDX analy-Surface treatmentDifusion activation energy/kJ *mol -1sis is slightly less than that calculated by elemental a-nalysis. It can also be found that the diffusion eoeff-Silane coupling agent96.4894. 49.cient is larger at higher temperatures. This can be ex-Chemical treatment102.74100. 25plained by the quick movement of water molecules athigh temperature.Sand paper burnishing105.78103.49Table 1 also shows that silane coupling agent treatmentleads to the lowest value of the water uptake and waterTable 2 and Table 3 show that diffusion rate constantincreases with temperature increasing because thdiffusion coefficient in the joints among the three treat-movement of water molecules is quicker at higher tem-ment methods tested. Sandpaper burnishing treatmentperatures. The values of water diffusion rate constantcan only increase the interface roughness and interfaceand diffusion energy calculated from EDX analysis forarea. Chemical oxidation treatment following the sand-the joints subjected to different surface treatments arpaper treatment can oxidize the surface of graphites ,almost the same as those calculated from elemental aproducing polarity groups ,forming micro-pores, andnalysis. The reasons caused by the differences are thesame as that caused by changes in the determination ofconsequently increase adhesive area and surface activi-diffusion coefficient. However, compared with elemen-ty of the joints during the curing process. Silane cou-tal analysis, EDX analysis is simpler and its errors arepling agent treatment following the chemical oxidationsmaller because the thickness of the cohesive layer hastreatment can form polarity groups, such as -O-Si-R-no influence on test results. Therefore, EDX analysisNH2, on the surface of graphite, producing a transitionis more feasible than elemental analysis for in-situ a-layer, which can reduce water penetration rate in thenalysis of water diffusion dynamics in the cohesivejoints s. The EDX method is especially applicable toadhesive joints. As a result, the durability of adhesivesthe characterization of medium- resistant performance ofis improved. Thereby the change order is reasonable.cohesive joints containing adhesives with hygroscopic.3.3 Calculation of water diffusion dynamics in theadhesive joints4 ConclusionsAs discussed above, plots of ln(1/c) against time areWater中国煤化工fusion enersy in thecohes:YHCNMHGusingEDXandele-linear (Fig.1 to Fig. 6). This indicates that the watermental analysis method are similar. However, the EDXdiffusion is a first order reaction. So the diffusion rateanalysis method is simple, feasible, and particularlyconstant and diffusion activation energy can be caleu-applicable to the characterization of medium-resistantlated using equation (9). The calculation results areperformance of cohesive joints containing adhesives●70.Joumal of Marine Science and Applicatin,Vol. 5 ,No.2, June 2006with hygroscopic.[6]RIDER A, ARNOTT D. Boilingwater and silane pre-treat-ment of aluminium alloys for durable adhesive bonding[ J].Surface treatment methods for adhesive materials playInternational Joural of Adhesion & Adhesives, 2000, 20important roles in preventing water diffusion. The dura-(3) :209 - 220.bility of graphite joints treated by coupling agent is su-[7] WYLDEJ w, SPELT J K. Measurenent of adhesive jointperior to that treated by chemical oxidation and sandpa-fracture properties as a function of environmental degrading[J]. International Joumal of Adhesion and Adhesives ,per bumishing.1998 , 10(4) :237 -246.[8] BISTAC s, VALLAT M F, SCHULIZ J. Durability ofReferences:steel/ polymer adhesion in an aqueous environment[J]. In-temational Journal of Adhesion & Adhesives, 1998, 10[1] MARCADON V, NADOT Y, ROY A, GACOUGNOLLE J(5) :365 -369.L. Fatigue behaviour of T-joints for marine applications[9] ABEL M L, ALLINGTON R D, DICBY RP, et al. Under-[J]. International Journal of Adhesion & Adhesives.standing the relationship between silane application condi-2006 ,26<7) :481 -489.tions[J]. Bond Durability and Locus of Failure, 2006 ,26[2] PROLONGO C, ROSARIO C. Comparative study on the(1-2) :50-61.adhesive properties of dfferent epoxy resins [J]. Interma-tional Jourmal of Adhesion & Adhesives , 2006 ,26(3):125WANG Jun, borm in 1965, received a- 132.3. S. in chemical engineering from Dalian[3] BOWDITCH M R. The durability of adhesive joints in theUniversity of Technology in 1988 and anpresence of water[J]. Int J Adhesion and Adhesives , 1996 ,M. S. in organic chemistry from Hei-16:73 -79.longjiang University in 2005. She is an[4]LOH W K, CROCOMBE A D. Environmental degradationassociate professor in the Schoo of Chemi-of the interfacial fracture energy in an adhesively bondedcal Engineering, Harbin Engineering Uni-joints[J]. Engineering Fracture Mechanics, 2002 , 69versity. Wang' s main research interests(18):2113 -2128.are synthesis of macromolecule material and analysis of chemical[5]CONMYN J. A Review of certain recent work on the dura-transfer processes and chemical dynamics.bility of aluminium alloy bonded with epoxide and phenolicadhesive[J]. Journal of Adhesion, 1989 ,29(2):121 -130.中国煤化工MYHCNMHG

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