The results of computer optimization of visual transmission factor Tv of the heat-reflective coating SnO2-Ag-SnO2 и TiO2-Ag-TiO2 with protective layers are presented. It is stated that for the condition Tv?80 % to be fulfilled the thickness of protective silver layers for SnO2-Ag-SnO2 should not exceed 1,5 nm, but for TiO2-Ag-TiO2 it is 2 nm. Heat reflective coatings with one protective layer are shown to possess better optical characteristics in comparison with two protective layers

Dyskin, V. G.

Electronic archive of Tomsk Polytechnic University

As a consequence of oil crisis and steady growth offuel prises an urgent problem has become not only development of energy on the basis of alternative, for example renewable sources of energy, but also introduction ofnew energysaving technologies into construction of residential, office and industrial buildings. Application ofenergysaving glazing in construction decreases energyconsumption for building heating in winter, and for theircooling in summer. The basic element of energysavingglazing constructions is either heatabsorbing or neutrallycoloured or heatreflecting glasses [1–4].Heatreflecting glass is sheet glass, on which a heatreflecting coating (HRC) representing a selective dielectricmetaldielectric coating is applied. Applicationof threelayer structure of HRC is explained by the factthat for increasing metal adhesion with glass an intermediate layer is used, but for decreasing metal reflectioncoefficient and its environmental protection a antireflective layer is applied. As a metal layer thin films fromCr, Ni, Ag, Cu, Au, Al are employed, but the main metal of HRC is silver that reflects radiation of infraredspectrum strongly and has a small degree of polarizationeven at large angles of radiation falling [5, 6].On the commercial scale application of HRC on flatstructural glass is made by magnetron spraying machine. Toprotect silver layer from the action of oxygen plasma atmagnetron application protective (barrier) layers are used[1–4]. As metals, semiconductors, oxides and etc. formcontinuous films by different thickness, investigating influence of structure, material and thickness of barrier layers onoptical characteristics of HRC is of great practical interest.The purpose of the given work is to study the influenceof structure, material and layer thickness on optical characteristics of heatreflective coating, to determine optimalthickness of protective layers by the computer simulationmethod. As an object of investigation the SnO2AgSnO2(SAS) and TiO2AgTiO2 (TAT) HRC have been chosen.As a criteria of HRC optimization visual transmission factor Tv, which is defined by the formula, is chosen(*)where V(λ) is the relative spectrum sensitivity of human eye[7], T(λ) is the HRCglass system transmission factor, λ1and λ2 are the boundaries of visual spectrum region, E(λ) isthe standard spectrum of direct flux of solar radiation AM1.5[8]. The spectrum is normalized to the maximum value.Fig. 1. HRC structure without protective layer (а), with twoprotective layers (b), with one protective layer (c). Thenumbering of layers is from the top downBy optimization in the given work is meant searchfor structures, materials and layer thicknesses of HRC,for which Tv have maximum values. Materials, layerthicknesses and structures of HRC realizing the maximum values of Tv, are called optimal below.Computer methods of optical coating design are based on mathematical methods of multiparametric optimization [9–11]. The results of optimization are knownto depend on the choice of initial values of objective variables, therefore, in the present work search for themost value (*) is carried out by the method of layer thickness enumeration. The step of thickness change ischosen not less than the accuracy with which one canapply layers, but the interval of layer thickness change ischosen in such a way that it would include all values taking place in practicewhere di is the thickness of ithlayer coating,γ1=0,25λ1/n1, γ2=0.25λ2/n2, n1, n2 are the refractive indexes of ithlayer for λ1=0,40 mkm λ2=0,75 mkm. Thethickness of silver layer is 12 nm, corresponding to continuous film, remains constant at simulation. Description of mathematical model of multilayer thinfilm system and recurrence formulas for calculation ofrefractive, transmittance, absorption indexes is presented in [9]. The glass refractive index is taken to be equalto 1,5. The integral is calculated numerically, opticalconstants of layer materials are borrowed from [10–14].min maxmin 1 2max 1 2[0,75 ,1,25 ],min( , ),max( , ),id d dddγ γγ γ∈==Protective layer MetalGlassDielectric???2121( ) ( ) ( ),( ) ( )vE V T dTE V dλλλλλ λ λ λλ λ λ=∫∫Bulletin of the Томsк Pоlytеchnic University. 2007. V. 310. № 190UDC 537.533OPTIMIZATION OF TRANSMISSION FACTOR OF HEATREFLECTIVE COATINGV.G. Dyskin«Physics – Sun» SPA of Uzbekistan AS. The Physicotechnical institute, TashkentEmail: dyskin@uzsci.netThe results of computer optimization of visual transmission factor Tv of the heatreflective coating SnO2AgSnO2 и TiO2AgTiO2 withprotective layers are presented. It is stated that for the condition Tv≥80 % to be fulfilled the thickness of protective silver layers forSnO2AgSnO2 should not exceed 1,5 nm, but for TiO2AgTiO2 it is 2 nm. Heat reflective coatings with one protective layer are shown topossess better optical characteristics in comparison with two protective layers.b сOptimization of layer thickness of SAS and TAT isperformed without protective layers (fig. 1, а). Calculations show (fig. 2) that for optimal thicknesses the transmittance indexes in infrared region of the spectrum arepractically the same, but in shortwave region of thespectrum of TAT they have better optical characteristicsin comparison with SAS. Visual transmittance coefficient of both coatings is equal to 97,0 %.Fig. 2. Spectrum transmittance indexes: 1) SnO2(44 нм)AgSnO2(55 nm) and 2) TiO2(39 nm)AgTiO2(47 nm)аbFig. 3. Influence of protective layer thickness on visual transmittance index TiO2AgTiO2 (а) and SnO2AgSnO2 (b). Fordifferent materials: 1) Si, 2) Al, 3) Ti, 4) Ni85Cr15, 5) Ni, 6) CrIn fig. 3 the calculation results of dependence Tv onthickness of protective layer of different materials are presented. Requirements for the material of protective layerare obvious: minimal decrease in Tv, stability to corrosiveoxygen medium, capacity for formation of continuousfilms of small thickness on the layer surfaces. Simulationshowed that for HRC with barrier layers (fig. 1, b) optimalstructure is a symmetrical one, i. e. a structure with equal thickness of protective layers. Limiting thickness andoptimal material of protective layer can be determinedusing the condition Tv≥Tv,min, where Tv,min is the specifiedminimal value of Tv. For example, if Tv,min=80 % (in fig. 3is the line parallel to abscissa axis), then:• Maximum thickness of protective layers for SAS is1,5 nm, for TAT it is 2 nm;• The use of chromium as a protective layer is of nopoint;• The use of Ti as a protective layer instead of Ni85Cr15decrease the duration of spraying operation cycle(one need not season the targets from NiCr alloy inplasma of magnetron charge);• Barrier layers of 1,5 nm thick and 2 nm from Al, Ti,Ni85Cr15, Ni make visual transmittance index of SAS10 and 20 % less, but TAT make 8,0 and 17,0 % less.To improve optical characteristics of HRC in [4] oneprotective layer is suggested to use (fig. 1, c). In order tocompare optical characteristics of the same materialsoptimization of visual transmittance index of HRC withone protective layer has been performed. The results ofoptimization are presented in the table.Table. The results of Tv calculation for HRC with one (the value is at the top) and two (the value is at the bottom)protective layersFig. 4. Spectral transmittance index TiO2AgTiO2 (1, 3) andSnO2AgSnO2 (2, 4) with one (1, 2) and two (3, 4)Ni85Cr15 protective layers0,5 1,0 1,5 2,0020406080100, ????T,%4312Barrier layerSnO2AgSnO2 TiO2AgTiO21 nm 2 nm 1 nm 2 nmAl94,1 89,9 94,9 92,190,0 80,1 92,3 84,9Ti92,0 86,6 92,7 88,287,2 77,8 88,9 80,6Ni85Cr1591,5 85,8 92,3 87,586,4 76,3 88,1 79,4Ni91,0 84,8 91,6 86,785,4 74,4 87,3 77,80,0 0,5 1,0 1,5 2,060708090100623451Tv??????? ????????? ????, ??0,0 0,5 1,0 1,5 2,060708090100 Tv526431??????? ????????? ????, ??6789100,4 0,6 0,8 1,0 1,25060708090100, ????T,%21Mathematics and mechanics. Physics91Comparison of Tv values and that in fig. 4 indicatesthe advantage of HRC with one protective layer in comparison with that with two layers. It is evident that application of one protective layer is possible if silver does notdiffuse into dielectric and protective layers.It should be noted that use of SnO2 in HRC productionis conditioned by the fact that its spraying index (cooling rate correspondingly) is several times higher than that of TiO2[14]. In our opinion, modification in construction of magnetron spraying devices on the purpose of increasing spraying index of target materials will contribute to introductionof HRC on the basis of TiO2 into the production [15].The author is grateful to Dr. of phys.math. Sciences, ProfessorV.P. Krivobokov for discussion of the work and useful remarks. Bulletin of the Томsк Pоlytеchnic University. 2007. V. 310. № 192REFERENCES1. Sleptsov V.V., Spivakov D.D., Alexandrov А.Yu. Heatsaving glassesand energysaving // Thermal engineering. – 1999. – № 4. –P. 45–47.2. Minko N.I., Mikhalchuk I.N., Lipko М.Yu. Modification of sheetglass surface // Glass and ceramics. – 2000. – № 4. – P. 3–7.3. MartinPalma R.J., Vazquez L., MartinezDuart J.M., MalatsRiera. Silverbased lowemissivity coatings for architectural windows:Optical and structural properties // Solar Energy Materials and Solar Cells. – 1998. – № 5. – P. 55–66.4. Bainov D.D., Krivobokov V.P., Legostayev V.N. Optimization in antireflection of heatreflective coating // Heleoengineering. – 2004. –№ 3. – P. 85–91.5. Rozenberg G.V. Presentday practice in optical property theory ofsemitransparent metal surfaces // Successes in Physical Sciences. –1956. – V. 58. – № 3. – P. 487–518.6. Vvedenskiy V.D., Pinskaya R.Ya., Furman Sh.А., Shestakova Т.V.Wideband reflectors on the basis of silver films // Opticalmechanical Industry. – 1983. – № 12. – P. 48.7. Irodov I.Е. Problems on general physics. – Moscow: Nauka. 1979.– 368 p.8. Koltun М.М. Solar elements. – Moscow: Nauka, 1987. – 192 p.9. Yakovlev P.G., Meshkov B.B. Design of interference coating. –Moscow: Machine building. 1987. – 186 p.10. Himmelblau D. Applied nonlinear programming. – Moscow: Mir,1975. – 534 p.11. Gusnin S.Yu., Omelyanov G.А., Reznikov G.А., Sirotkin V.S. Minimization in engineering computer calculations. – Moscow: Machine building, 1981. – 121 p.12. Zolotarev V.М., Morozov V.N., Smirnova Е.V. Optical constants ofnatural and technical media. – Leningrad: Chimiya, 1984. – 215 p.13. Sasovskaya I.I, Noskov М.М. Optical properties of nickel // Physicsof Metals and Metal Science. – 1971. – V. 32. – № 4. – P. 723–727.14. Gorban N.Ya., Stashchuk V.S., Shishlovskiy А.А. Peculiarities oflight absorption in NiCr alloys // Journal of Applied Spectroscopy.– 1974. – V. 20. – № 5. – P. 881–885.15. Pleshivtsev N.V. Physical problems of cathode spraying. – Moscow:Kurchatov’s IAE, 1979. – 80 p.16. Zhukov V.V., Krivobokov V.P., Yanin S.N. Spraying magnetron diode target in the presence of external ion beam // Journal of Technical Physics. – 2006. – V. 76. – № 4. – P. 61–67.Arrived on 15.09.2006IntroductionOne of the reasons for rapid destruction of polyethylene products and constructions of high pressure(PEHP) is their cracking under the action of externalmechanic stress. At the same time polyethylene is widely used in everyday life, in industry, as well as in highvoltage electrophysical devices operating under the condition of high voltage field, stresses, high temperature,different climatic factors. To increase cracking resistance is possible introducing powder mineral substances, forexample, aerosol, chalk, talc into the polymer, but theeffect is achieved at additives significant in content [1]. Awide application of the given method is inhibited by theabsence of efficient modifiers which would increasecracking resistance sufficiently even in low content andwould not impair other polymer characteristics. Fromthe viewpoint of economical and technological utility ofnew polymer modifiers the problem is to produce composite materials by means of the equipment and methodsapplied in manufacturing goods at present [2].UDC 541.16:182INCREASING CRACKING RESISTANCE OF HIGHPRESSURE POLYETHYLENE MODIFIED BY ULTRAFINE POWDERSМ.А. Ilyin, V.I. Vereshchagin, D.V. Tikhonov*, О.B. Nazarenko*Tomsk Polytechnic University*TPU High Voltage Research InstituteEmail: nanolab@hvd.tpu.ruThe affect of small additions (≤1 wt. %) of ultrafine fillers AlN и Al2O3 on cracking resistance of highpressure polyethylene has been investigated. The most increase of cracking resistance is obtained for polyethylene samples produced at low cooling rate filled with AlN(0,075 wt %).

Optimization of transmission factor of heat-reflective coating

Abstract

Similar works

Full text

Available Versions

Electronic archive of Tomsk Polytechnic University