电化学Investigation of Structural and Electrical Properties of Polyaniline Gold Nanocomposites

电化学Investigation of Structural and Electrical Properties of Polyaniline Gold Nanocomposites
电化学Investigation of Structural and Electrical Properties of Polyaniline Gold Nanocomposites

Investigation of Structural and Electrical Properties of Polyaniline/Gold Nanocomposites

Asma B.Afzal,?,?M.Javed Akhtar,*,?Muhammad Nadeem,?and M.M.Hassan ?

Physics Di V ision,PINSTECH,P.O.Nilore,Islamabad 45650,Pakistan,and Department of Chemical and Material Engineering,PIEAS,Islamabad 45650,Pakistan

Recei V ed:March 26,2009;Re V ised Manuscript Recei V ed:July 31,2009

Gold nanoparticles are synthesized by the reduction of gold salt using extract of tea leaves in 1-methyl-2-pyrrolidinone (NMP)solution.Transmission electron microscopy (TEM)con?rmed the formation of gold nanoparticles having average size of ~20nm.These nanoparticles have been incorporated in NMP solution of polyaniline emeraldine base (PANIEB)to cast the nanocomposite ?lms.Thermogravimetric analysis (TGA)revealed that the thermal stability of the nanocomposites has improved as compared to the pure PANI.TEM con?rmed the presence of gold nanoparticles in polyaniline matrix.The impedance spectroscopic studies showed that gold nanoparticles have considerable effects on the electrical properties of PANI by reducing the charge trapping centers and increasing conducting channels,which causes substantial decrease in the real part of impedance.

1.Introduction

The nanosized metallic particles have attracted attention of the materials community due to their unique properties.1,2In recent years,the synthesis of organic/inorganic nanocomposites has become the subject of extensive studies.The nanocomposites containing organic polymers and inorganic particles in nanoscale regime provide a completely new class of materials with novel properties.3-5Conducting polymers are interesting materials in modern technology because of their potential applications such as electromagnetic radiation shielding,antistatic coatings and sensors.6,7Polyaniline (PANI)is unique among the family of conjugated polymers due to its good environmental stability,ease of preparation,inexpensiveness and reversible control of conductivity both by charge-transfer doping and protonation.The polyaniline emeraldine base (PANIEB)consists of equal number of reduced [-(C 6H 4)NH(C 6H 4)NH -]and oxidized [-(C 6H 4)N d (C 6H 4)d N -]repeat units.It is the most stable form of PANI and its conductivity can be enhanced by incorporation of metal nanoparticles.It is insoluble in common organic solvents (such as chloroform,xylene,THF,etc.)and mostly soluble in 1-methyl-2-pyrrolidinone (NMP)and can be cast into a ?exible ?lm with residual NMP,about 10-18%by weight,as a plasticizer.During ?lm casting,the slow controlled evaporation of the solvent freezes the rapidly changing diblock nature of the polymer leading to phase separation.8The residual NMP in the resulting ?lm causes the microphase separation into reduced repeat units and oxidized repeat units,which affects the bulk conductivity of the polymer.9

A number of studies have shown that the electrical and mechanical properties of the conducting polymers can be improved by the incorporation of metal nanoparticles.For instance,Breimer et al.10observed that the electrical conductivity of polypyrrole has been enhanced by incorporating gold nanoparticles into photosynthesized polypyrrole ?lms.Zhou et al.11reported the synthesis of novel stable nanometer-sized metal (M )Pd,Au,Pt)colloids protected by a π-conjugated polymer.

Cho et al.12examined the electrical properties of contacts formed between conducting polymers and noble metal nanoparticles (platinum,gold,and silver)using current sensing atomic force microscopy.Sarma et al.13have prepared PANI-gold nanocom-posites by ?rst reducing gold salt solution and then polymerizing aniline in the same medium.Ma et al.5employed one-step synthesis of water-soluble gold nanoparticles/PANI composite for glucose sensing applications;whereas Pillalamarri et al.14also used one-pot synthesis method in which composite materials consisting of polyaniline nano?bers decorated with noble-metal (Ag or Au)nanoparticles were synthesized with γ-radiolysis.The electrical conductivity of the composites increased with the loading of nanometals in the polymer.Wang et al.15synthesized nanosized metallic particles via reduction of the metal salts by PANIEB in both NMP and aqueous media;as a result of these reactions,the polyaniline is converted to a higher oxidation sate.Recently,we have studied the structural and electrical properties of PANI/Ag nanocomposites and found that silver nanoparticles have profound effects in improving the thermal stability and electrical conductivity of PANI.16In the present study,we report a new method for the synthesis of gold nanoparticles.These nanoparticles were suspended in NMP solution and their different concentrations were incorporated in PANI to cast NMP plasticized PANI-Au nanocomposite ?lms.This method is cheap and clean with minimum risk of contamination to get the nanocomposite.Various techniques including Fourier transform infrared spectroscopy (FTIR),transmission electron microscopy (TEM),and thermogravimetric analysis (TGA)were used to characterize the PANI/gold nanocomposites for structural characterization and impedance measurements have been carried out for the determination of the electrical properties.

2.Experimental Section

2.1.Materials.Aniline monomer (Riedel-de-Hae ¨n)was distilled under vacuum before use.Ammonium peroxydisulfate (APS,Riedel-de-Hae ¨n),NMP (Panreac),HAuCl 4(Alfa Aeser),and HCl (Panreac)were used as-received without further puri?cation.Deionized water was used throughout the experiment.

*To whom correspondence should be addressed.E-mail:javeda@https://www.360docs.net/doc/6314568327.html,.pk.Phone:+92-51-9290231.Fax:+92-51-9290275.?

PINSTECH.?

PIEAS.

J.Phys.Chem.C 2009,113,17560–17565

1756010.1021/jp902725d CCC:$40.75 2009American Chemical Society

Published on Web 09/11/2009

2.2.Synthesis.Gold nanoparticles can be synthesized by using various plant extracts;17in the present study,extract of black tea leaves was used to reduce the gold salt to gold nanoparticles.Black tea leaves are rich in polyphenolic com-pounds such as thea?avins and thearubigins that belong to catechin group of?avinols.Many of them have well-de?ned antioxidant properties that are directly correlated to the total phenolics content of tea;18recently,it has been suggested that quercetin may play an important role in the reduction of Au(III) to gold nanoparticles.19We have used the extract of black tea leaves by soaking2.0g of tea leaves in20mL of NMP overnight.NMP extract of tea was then?ltered using a common ?lter paper and stored at4°C until further use.An aqueous solution of HAuCl4(50mL,0.5mM)was re?uxed for5-10 min,and1mL of a warm(50-60°C)NMP extract of tea was added to it quickly.Re?ux was continued for another40min until the appearance of a deep-red solution of gold nanoparticles. The particle solution was?ltered through0.45μm Millipore syringe?lters to remove any precipitate.Gold nanoparticles were then pelletted twice using a benchtop centrifuge at13000rpm for30min and resuspended in NMP to make a solution having 72μg/mL of gold nanoparticles for further use.

PANIEB was prepared by chemical oxidation of aniline with

APS as oxidant in1M HCI solution.20In a typical procedure,

aniline(20mL)was dissolved in300mL of1M HC1and

cooled to5°C in an ice bath.A precooled solution(200mL)

of11.5g APS in1M HC1was added to the aniline solution

dropwise over a period of~2min under constant stirring.After ~1.5h,the precipitates were collected on a Buchner funnel and washed with1M HCI.The polyaniline hydrochloride so

obtained was converted into PANIEB by treatment with0.1M

NH4OH and drying under dynamic vacuum for48h at room

temperature.The PANIEB powder obtained was stored for

further study.

PANIEB?lm was made by dissolving PANIEB powder in

NMP.In a typical procedure,1g of?nely ground PANIEB

was stirred magnetically in250mL of NMP at room temperature

for~8h;an intense blue solution was formed,which was

?ltered through a Buchner funnel indicating the formation of

PANIEB.21In addition,we performed the UV-vis spectroscopy

(not shown here),where a peak at about620nm was observed

that con?rmed that PANIEB was synthesized.22We used three

concentrations(0.24,0.48,and0.72wt%)of gold nanoparticles

(in NMP solution)and mixed with the NMP solution of

PANIEB;mixture of both solutions was stirred in ultrasonic

bath for~12h.This mixture was poured in Petri dish and the

solvent was evaporated at120°C to cast the PANI/gold

nanocomposite?lms.Hereafter,these polymer?lms are referred

as PANI-Au1(0.24wt%Au),PANI-Au2(0.48wt%Au),

PANI-Au3(0.72wt%Au)and pure PANI.Pure PANI?lm

had also been prepared using the above-mentioned procedure.

2.3.Characterization.FTIR spectra of PANI?lms were recorded using Nicolet6700FTIR with ATR in the4000-400 cm-1range for50scans.The TGA of the?lms was carried out on a Mettler Toledo in the temperature range of50-850°C under nitrogen atmosphere at heating rate of10°C/min.The gold nanoparticles and the nanocomposites were characterized by TEM,JEM-1010(JEOL)operating at120kV.Specimens for TEM examination were prepared by slow evaporation of one drop of Au/NMP and PANI/Au solutions on a carbon-coated copper mesh grid.

Impedance measurements of all PANI samples were per-

formed using an Alpha-N Analyzer,Novocontrol(Germany)

in the frequency range0.1e f e106Hz at room temperature.WINDETA software was used for data acquisition,which has been fully automated by interfacing the analyzer with a PC. Before impedance experiments the dispersive behavior of the leads was carefully checked to ensure the absence of any extraneous inductive or capacitative coupling in the experimental frequency range.The ac signal amplitude used for all these studies was0.5V.The ac resistivity measurements were performed on?lms having a diameter of13mm and a thickness of~2μm.Contacts were made by silver paint on opposite sides of the?lms,which were cured at70°C for3h.In this study the results of the complex impedance are presented as Z)Z′+jZ′′and permittivity asε)ε′-jε′′,where Z′,ε′and Z′′,ε′′are the real and imaginary parts of impedance and permittivity, respectively.The relationship betweenεand Z is given byε

)(Z-1/jωC c),whereω)2πf and C c is the capacitance of the measuring cell.23

3.Results and Discussion

In order to determine the possibility of interactions between gold nanoparticles and PANI matrix,FTIR spectroscopy of the pure PANI as well as nanocomposite?lms were performed (Figure1).All of the characteristic absorption bands for the PANIEB16,24were observed in pure PANI(Figure1a).The bands at3284are assigned to N-H stretching.The presence of a strong C d O stretching band at1671cm-1indicates that the PANIEB?lm contains residual NMP solvent.The bands at1582 and1487cm-1are attributed to C d C stretching mode of vibration for the quinoid and benzoid units,while the bands at 1274and1242cm-1,shown in the inset of Figure1,are due to C-N and C d N cm-1stretching modes,respectively.The bands at1169and827cm-1are the distinctive features of C-H in-plane and C-H out-of-plane bending,respectively.These characteristic bands of PANIEB can also be seen in the infrared spectra of the nanocomposite?lms(Figure1b-d)con?rming the formation of PANI in all samples.However,we note a shift in some peak positions indicating that gold nanoparticles and the polymer have an interaction between them.The shift in peaks positions,associated with C d C(1582cm-1)by~7cm-1and C d N(1242cm-1)by~17cm-1(the shift of this band toward lower wavenumber is shown in the inset of Figure1),is due to stretching of the quinoid ring.We do not observe any signi?cant change in the peaks’positions associated with the benzoid

ring. Figure1.FTIR absorption spectra of(a)Pure PANI(b)PANI-Au1 (c)PANI-Au2and(d)PANI-Au3;inset shows the shift of1242cm-1 band.

Properties of Polyaniline/Gold Nanocomposites J.Phys.Chem.C,Vol.113,No.40,200917561

From these results we can infer that gold nanoparticles may reside more close to the imine nitrogen of the PANI.These results support the conduction mechanism in PANI/gold nano-composites proposed by Tseng et al.25From Figure 1,it can be seen that intensities of the bands have been reduced due to the presence of Au nanoparticles.The reduced intensity of the bands can be attributed to the interactions between gold nanoparticles and PANI matrix.We have observed a similar behavior in PANI/Ag nanocomposites.16

The TGA measurements of the pure PANI and PANI-Au nanocomposites,having different concentration of Au,are shown in Figure 2.The degradation occurs in three steps.The evaporation of moisture is observed up to 100°C;the second weight loss from 140to 435°C is due to the evaporation of NMP.26For pure PANI,the major weight loss occurs after 435°C indicating the structural decomposition of the polymer (Figure 2a).An improvement in the thermal stability of the nanocomposite can be seen,which increases with an increase in the nano?ller content.The onset of thermal degradation is shifted toward higher temperatures by about 40°C for the composites,having highest concentration of gold nanoparticles,that is,PANI-Au3(Figure 2d).These results are in agreement with the thermal decomposition data of the PANI/silver nano-composite,16where it was shown that the composite decomposes at higher temperature when PANI is loaded with silver nano-particles.It is important to point out that at 850°C;the weight loss of the nanocomposites is 5,10,and 20%less in PANI-Au1,PANI-Au2,and PANI-Au3,respectively,when compared with pure PANI.The improved thermal stability of the nano-composites can be attributed to the reduced mobility of the polymer chains that in turn suppresses the free radical transfer via interchain reactions.As a result,the process of degradation will be slowed and decomposition will take place at higher temperature.27

Figure 3shows transmission electron micrographs of gold nanoparticles in NMP and PANI/Au nanocomposite ?lm.It can be seen that pure gold nanoparticles in NMP have narrow size distribution,having ~20nm average particle size,as estimated from TEM (Figure 3a).In the case of nanocomposites,we note that spherical shaped Au nanoparticles,having mean diameter of ~20nm,are distributed in the polymer matrix (Figure 3b).Although some agglomerates are formed,this may be due to the synthesis of nanocomposite ?lms at 120°C for 16h.The

number of these particles increases as the concentration of gold is increased in PANI/Au nanocomposite ?lms.

The impedance spectroscopy was employed at room temper-ature to explore the electrical properties of PANI ?lms contain-ing gold nanoparticles.Figure 4a shows the real part of the impedance of pure PANI and nanocomposite ?lms when plotted as a function of frequency;we note that the effect of high frequency on Z ′for both pure PANI and PANI/Au nanocom-posites is small.Below 5000Hz,there is slight dispersion of Z ′but around 30Hz a sharp change in the real part of the impedance can be observed.At low frequency,the real part of the impedance have the values of 3.0×108,1.65×108,3.71×107,and 2.57×107?for pure PANI,PANI-Au1,PANI-Au2,and PANI-Au3,respectively.It can be inferred that incorporation of 0.24,0.48,and 0.72wt %gold nanoparticles in PANI cause 2-,8-,and 12-fold decrease in resistivity when compared with the pure one.The plots for the imaginary part of impedance versus frequency,as shown in Figure 4b,are resolved into two peaks,the strong peak at low frequency and a weak peak at high frequency for all PANI samples.Both of these peaks are similar to that reported earlier in the impedance studies of PANI/Ag nanocomposites,16which may be due to microphase separation of the polymer chains.9,28,29In the case of nanocomposites both peaks are suppressed but this decrease is more distinct in PANI-Au2as compared to that of PANI-Au1.From these outcomes we observe that incorporation of the gold nanoparticles results in the frequency shift of both peaks.In PANI-Au3loading of gold nanoparticles shifts the strong peak in low frequency region and the weak peak in high frequency region from 2to 5.2and 1088to 674Hz,respectively.Thus in PANI/Au nanocomposite ?lms both peaks are sup-pressed and a shift in the peaks position is evident;the inset of Figure 4shows the weak peaks positions for PANI-Au2and PANI-Au3?lms.From these results,we can infer that incor-poration of gold nanoparticles inside the PANI matrix may lead to a faster charge transfer than pure one.It may be suggested that in pure PANI the charge is transferred by two phases,that is,the phase of oxidized repeat units and the phase of reduced repeat units;whereas,in the case of nanocomposite ?lms,gold nanoparticles provide additional conducting channels for charge transportation,which are responsible for relaxation process.30

Figure 5shows the typical impedance (Z )Z ′+jZ ′′)plane plots between real (Z ′)and imaginary (Z ′′)parts of the impedance for pure PANI and PANI/Au nanocomposite samples.It contains two arcs,a small one at high frequency preceding a large one at low frequency.Previously,it has been reported that in NMP plastisized PANI ?lms,the peak at lower frequency is due to the conductivity relaxation of the phase with oxidized repeat units and that at higher frequency to the relaxation of the phase with reduced repeat unit.It was also observed that the resistivity of the reduced repeat units is lower than that of the oxidized repeat units.9,29On this basis it has been suggested that the small arc at high frequency with low value of resistivity is due to the conductivity relaxation of the reduced repeat units and the large arc at low frequency having high value of resistivity is because of the relaxation of the oxidized repeat units.16,28The intersection values of the two arcs representing two phases give the resistance corresponding to the ac values.The reduced repeat units intersect the Z ′axis at the left-hand side and its extension on the right-hand side intersects the same axis at a point termed as R r (resistance of the phase of reduced repeat units).The extension of the oxidized repeat units on the right-hand side intersects the real part of impedance axis at a point de?ned as R o (resistance of the phase of oxidized

repeat

Figure 2.Thermogravimetric analysis of (a)Pure PANI,(b)PANI-Au1,(c)PANI-Au2,and (d)PANI-Au3.

17562J.Phys.Chem.C,Vol.113,No.40,2009Afzal et al.

units).From Figure 5,we note that the impedance plots show two well-resolved arcs representing both types of repeat units.A comprehensive decrease in the size of impedance plane plots has been observed with the addition of even very low concen-tration of gold nanoparticles (PANI-Au1).This decrease in the impedance can be attributed to the charge transfer between PANI and gold nanoparticles.With the ampli?cation of frequency the imine nitrogen of PANI may donate electrons to gold nanopar-ticles.Consequently,the gold nanoparticles become more negatively charged,whereas PANI chains become more posi-tively charged.Therefore,the electrical conductivity of PANI/Au nanocomposite signi?cantly increases.25

Figure 6shows the proposed equivalent circuit model of the resistance and constant phase element (CPE),which has been employed for the ?tting of impedance plane plots of pure PANI and nanocomposites.The ?rst small and second large semi-circles,representing the phases of reduced repeat units and oxidized repeat units,have been modeled with equivalent circuit con?guration (R r ,CPE r )and (R o ,CPE o ),where subscripts “r”and “o”stand for the phases of reduced and oxidized repeat units,respectively.The values of the simulated electrical circuits derived from impedance plane plots of PANI samples having different concentrations of embedded gold nanoparticles are listed in Table 1.In the pure PANI sample,the phase of reduced repeat units has values R r )2.15×107?,CPE r )7.93×10-12F,and of oxidized repeat units has R o )2.90×108?,CPE o )4.25×10-10F.When we compare present results with those previously reported PANI/Ag nanocomposites,16we observe a similar trend in both cases.Table 1shows that the addition of gold nanoparticles to PANI results in substantial rise in the CPE parameters.The resistance,R r of the phase of reduced repeat units and R o of the phase of oxidized repeat units decrease from 2.15×107to 1.6×107?and from 2.90×108to 1.69×108?,respectively,in PANI-Au1.However,

when

Figure 3.TEM micrographs of (a)gold nanoparticles in NMP and (b)

PANI-Au2.

Figure 4.(a)Real part Z ′and (b)imaginary part Z ′′vs log f for pure PANI and PANI/Au nanocomposite ?lms;insets show relaxation of second peak at higher

frequencies.

Figure 5.Impedance plane plots of pure PANI and PANI/Au nanocomposite ?lms.Inset is enlarged portion of the impedance plane plots of ?rst small

arcs.

Figure 6.Equivalent circuit model used for ?tting of pure PANI and PANI/Au nanocomposites.

Properties of Polyaniline/Gold Nanocomposites J.Phys.Chem.C,Vol.113,No.40,200917563

concentration of Au nanoparticles is increased from PANI-Au2 to PANI-Au3,R r decreases from1.6×107to1.52×106?and R o decreases from1.69×108to2.75×107?,respectively. These results indicate that incorporation of gold nanoparticles in PANI causes a sharp increase in the capacitance and a comprehensive decrease in the resistance30of both phases.The value of n r(CPE r of reduced part)increases from0.94to0.96 and n o(CPE o of oxidized part)from0.85to0.91when pure PANI is loaded with more Au nanoparticles(PANI-Au3).When n is close to1,the CPE resembles a capacitor;in the case of pure PANI,both n r and n o are less than1;therefore CPE behaves like a nonideal capacitor.31With the addition of gold nanopar-ticles,n r and n o are approaching to1;however,the phase of oxidized repeat units shows more heterogeneity as compared to that of reduced repeat units.

The variation of real part of permittivity,ε′,and imaginary part of permittivity,ε′′,versus frequency for pure PANI and PANI/Au nanocomposites are shown in Figure7.Two dielectric relaxations are observed in the spectrum of the permittivity,the low and high frequency relaxations.The low frequency relax-ation is generally associated with the structural relaxation and a dynamic glass relaxation(R-relaxation).28In the present study, the low frequency peak can be assigned to the dielectric relaxations of the phase of the oxidized repeat units.The high frequency relaxation(as shown in the inset of Figure7b),also called as Maxwell-Wagner(M-W)relaxation,32is due to the dielectric relaxations of the phase of the reduced repeat units. We note that the relaxations of the reduced repeat units become more distinct as the gold nanoparticles are incorporated in PANI when compared with pure PANI.Nanocomposites show higher

value of permittivity at all frequencies of measurement as compared to the pure PANI.

In the conducting polymers instead of permanent dipoles, there are strong charge(polaron and bipolaron)trapping centers33,34the localized motion of which serves as an electric dipole under applied external electric?eld.28This electric?eld causes the localized charge carriers to hop to neighboring sites resulting in the dielectric relaxations.Such charge hopping forms a continuous network allowing the charges to travel through the entire physical dimensions of the sample and causes electrical conduction.35In the absence of strong charge trapping centers,the charge hopping could extend throughout the sample leading to a continuous current at low frequencies.36When PANI is loaded with gold nanoparticles the charge trapping centers are reduced,thereby leading to a large number of charge participations in the relaxation process;as a result an increase in the conductivity of PANI is observed.

4.Conclusions

We have synthesized gold nanoparticles by the reduction of HAuCl4using extract of tea leaves in NMP;TEM revealed that average particle size is~20nm.These nanoparticles were successfully incorporated in PANIEB?lms,using a physical process with minimum risk of chemical contamination.FTIR con?rmed the formation of PANI in all https://www.360docs.net/doc/6314568327.html,parison of the thermal properties of pure PANI and the nanocomposite ?lms showed that the thermal stability is improved by about 40°C.TEM results showed that nanoparticles are embedded in the PANI?lms.The electrical properties of the nanocom-posites were determined by impedance spectroscopy.The conductivity relaxation analysis suggested microphase separation of NMP plasticized?lms into phases of reduced and oxidized repeat units.The conductivity of PANI?lms increases with increase in the concentration of embedded gold nanoparticles. Acknowledgment.We gratefully acknowledge the?nancial support of the Higher Education Commission of Pakistan through the Indigenous Scholarship Scheme for Ph.D.studies of Asma Binat Afzal in Science and Technology(Batch II). We are grateful to Dr.Irshad Hussain for the synthesis of gold nanoparticles.

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TABLE1:Fitting Parameters Calculated from Equivalent Circuit Model

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JP902725D

Properties of Polyaniline/Gold Nanocomposites J.Phys.Chem.C,Vol.113,No.40,200917565

SYS系列全程水处理器

SYS系列全程水处理器解析 全程处理器是针对工业,民用各种系统中普遍存在的四大问题:腐蚀、结垢、菌藻、水质。而利用最近的专利技术研制的综合处理器。它从根本上克服水医生系列产品“水垢净”“黄水清”“灭菌灵”“铁锈一扫净”的单一功能。使水系统处理需多种多台设备改变为单台设备即可完成综合处理。它应用航空领域的高技术——差转屏蔽效应及多点阵列组合,巧妙地解决了各种频谱间及与电晕效应场间的互相干扰、制约的重大难题,它具有对水质综合优化处理,防垢、防腐、杀菌、灭藻、超净过滤的功能,它具有机电一体化的设计,纯物理方式处理,无需化这药剂,阻力低,流量大。运行管理费用极低,操作简单,维护方便,是各用水系统最佳的选择。 SYS系列全程水处理器功效类型: 全程处理器是指该设备对不同的用水系统进行全程处理,以达到综合处理的目的。根据不同的水系统和存在的不同问题,设备分为A型、B型、C型、D型、E型、F型。 A型:防腐、除锈、脱色、超净过滤。可系统正常运行过程中完成防腐、控制二次污染、对水中的杂质进行吸附、浓缩、排污的全过程处理,使水质达标。应用系统:冷冻循环水系统、采暖循环水系统、洗浴水系统。 B型:防垢、除垢、超净过滤,可在系统正常运行过程中完成防垢、除垢、超净过滤、控制浊度、悬浮物杂质等全过程处理。应用系统:冷却循环水,工艺用水系统,洗衣机房,餐饮,各类换热设备等。 C型:杀菌、灭藻、超净过滤可在系统正常运行过程中完成杀菌、灭藻、控制二次污染、降低浊度、悬浮物、杂质等全过程处理。应用系统:采暖、空调水系统,冷却循环水,洗浴热水系统等。 D型:杀菌、灭藻、防垢、超净过滤,可在系统正常运行过程中完成杀菌、灭藻、防垢、降低浊度、悬浮物全过程处理。应用系统:冷却循环水,水质过滤,游泳池循环水等。 E型:防腐、防锈、防垢、超净过滤。可在系统正常运行过程中完成防垢、除垢、防腐、降低浊度、悬浮物、控制二次污染的全过程处理。适用于南方低硬度、低PH值、高腐蚀的水质。 F型:杀菌、灭藻、防垢、防腐、超净过滤,可在系统正常运行过程中完成防腐、防垢、杀菌、灭藻、控制水质的全过程处理。适用于中等硬度、腐蚀性的水质。 SYS系列全程水处理器工作原理: A型:水与金属接触所产生的腐蚀,从原理上讲是电化学腐蚀即“微电池效应”。全程处理器工作原理就是削弱抑制原电池效应。第一是利用特定频谱转换,依据“附肌效应”原理在水管内壁形成动态的负电荷富态层,逐渐削弱、抑制电化学腐蚀。使其腐蚀产物三氧化三铁,转换为稳态的四氧化三铁,达到以锈制锈的效果。第二是利用活性铁质滤膜,机械变孔径阻挡及电晕效应场三位一体的综合过滤体吸附,浓缩,最终排除水中的铁离子和钙离子,悬浮物、沉淀物

常用的水处理设备处理方法及功能有哪些

水处理便是通过物理的、化学的手段,去除水中一些对生产、生活不需要的物质的过程。为了适用于特定的用途而对水进行的沉降、过滤、混凝、絮凝,以及缓蚀、阻垢等水质调理的过程。 由于社会生产、生活与水密切相关,因此,水处理领域涉及的应用范围十分广泛,构成了一个庞大的产业应用。常说的水处理设备包括:污水处理和饮用水处理两种。经常用到的水处理药剂有:聚合氯化铝、聚合氯化铝铁、碱式氯化铝,聚丙烯酰胺,活性炭及各种滤料等。 常用的水处理方法有:(一)沉淀物过滤法、(二)硬水软化法、(三)活性炭吸附法、(四)去离子法、(五)逆渗透法、(六)超过滤法、(七) 蒸馏法、(八)紫外线消毒法等,现在将这些处理法之原理及功能在此一一说明。

一、沉淀物过滤法 沉淀物过滤法的目的是将水源内之悬浮颗粒物质或胶体物质清除乾净。这些颗粒物质如果没有清除,会对透析用水其它精密的过滤膜造成破坏或甚至水路的阻塞。这是最古老且最简单的净水法,所以这个步骤常用在水纯化的初步处理,或有必要时,在管路中也会多加入几个滤器(filter)以清除体积较大的杂质。滤过悬浮的颗粒物质所使用的滤器种类很多,例如网状滤器,沙状滤器(如石英沙等)或膜状滤器等。只要颗粒大小大於这些孔洞之大小,就会被阻挡下来。对於溶解于水中的离子,就无法阻拦下来。如果滤器太久没有更换或清洗,堆积在滤器上的颗粒物质会愈来愈多,则水流量及水压会逐渐减少。人们就是利用入水压与出水压差来判断滤器被阻塞的程度。因此滤器要定时逆冲以排除堆积其上的杂质,同时也要在固定时间内更换滤器。

沉淀物过滤法还有一个问题值得注意,因为颗粒物质不断被阻拦而堆积下来,这些物质面或许有细菌在此繁殖,并释放毒性物质通过滤器,造成热原反应,所以要经常更换滤器,原则上进水与出水的压力落差升高达到原先的五倍时,就需要换掉滤器。 二、硬水软化法 硬水的软化需使用离子交换法,它的目的是利用阳离子交换树脂以钠离子来交换硬水中的钙与镁离子,*此来降低水源内之钙镁离子的浓度。其软化的反应式如下: Ca2++2Na-EX→Ca-EX2+2Na+1 Mg2++2Na-EX→Mg-EX2+2Na+1 式中的EX表示离子交换树脂,这些离子交换树脂结合了Ca2+及Mg2+之後,将原本含在其内的Na+离子释放出来。 现在市面上出售的离子交换树脂为球状的合成有机物高分子电解质。树脂基质(resin matrix)内藏氯化钠,在硬水软化的过程中,钠离子会逐渐被使用耗尽,则交换树脂的软化效果也会逐渐降低,这时需要作还原(regeneration)的工作,也就是每隔固定时间加入特定浓度的盐水,一般是10%,其反应方式如下: Ca-EX2+2Na+ (浓盐水)→2Na-EX+Ca2+

电化学阻抗谱的应用及其解析方法

电化学阻抗谱的应用及其解析方法 交流阻抗法是电化学测试技术中一类十分重要的方法,是研究电极过程动力学和表面现象的重要手段。特别是近年来,由于频率响应分析仪的快速发展,交流阻抗的测试精度越来越高,超低频信号阻抗谱也具有良好的重现性,再加上计算机技术的进步,对阻抗谱解析的自动化程度越来越高,这就使我们能更好的理解电极表面双电层结构,活化钝化膜转换,孔蚀的诱发、发展、终止以及活性物质的吸脱附过程。 阻抗谱中的基本元件 交流阻抗谱的解析一般是通过等效电路来进行的,其中基本的元件包括:纯电阻R ,纯电容C ,阻抗值为1/j ωC ,纯电感L ,其阻抗值为j ωL 。实际测量中,将某一频率为ω的微扰正弦波信号施加到电解池,这是可把双电层看成一个电容,把电极本身、溶液及电极反应所引起的阻力均视为电阻,则等效电路如图1所示。 图1. 用大面积惰性电极为辅助电极时电解池的等效电路 图中A 、B 分别表示电解池的研究电极和辅助电极两端,Ra 、Rb 分别表示电极材料本身的电阻,Cab 表示研究电极与辅助电极之间的电容,Cd 与Cd ’表示研究电极和辅助电极的双电层电容,Zf 与Zf ’表示研究电极与辅助电极的交流阻抗。通常称为电解阻抗或法拉第阻抗,其数值决定于电极动力学参数及测量信号的频率,Rl 表示辅助电极与工作电极之间的溶液 电阻。一般将双电层电容Cd 与法拉第阻抗的并联称为界面阻抗Z 。 实际测量中,电极本身的内阻很小,且辅助电极与工作电极之间的距离较大,故电容Cab 一般远远小于双电层电容Cd 。如果辅助电极上不发生电化学反映,即Zf ’特别大,又使辅助 电极的面积远大于研究电极的面积(例如用大的铂黑电极),则Cd ’很大,其容抗Xcd ’比串 联电路中的其他元件小得多,因此辅助电极的界面阻抗可忽略,于是图1可简化成图2,这也是比较常见的等效电路。 图2. 用大面积惰性电极为辅助电极时电解池的简化电路 Element Freedom Value Error Error %Rs Free(+)2000N/A N/A Cab Free(+)1E-7N/A N/A Cd Fixed(X)0N/A N/A Zf Fixed(X)0N/A N/A Rt Fixed(X)0N/A N/A Cd'Fixed(X)0N/A N/A Zf'Fixed(X)0N/A N/A Rb Free(+)10000N/A N/A Data File: Circuit Model File:C:\Sai_Demo\ZModels\12861 Dummy Cell.mdl Mode: Run Fitting / All Data Points (1 - 1) Element Freedom Value Error Error %Rs Fixed(X )1500N/A N/A Zf Fixed(X )5000N/A N/A Cd Fixed(X ) 1E-6 N/A N/A Data File: Circuit Model File:C:\Sai_Demo\ZModels\Tutor3 R-C.mdl Mode: Run Simulation / Freq. Range (0.01 - 10000Maximum Iterations: 100 B

一步一步教你用Zview拟合交流阻抗谱(入门篇)

1.导入数据 [有人PM我,说看不到图,估计是最近教育网连google不畅之故,因为我的图是上传至g oogle空间的。今天索性把图重新上传至本坛,以消除此问题。另,如果图有错,请pm我] [第二次重新上传部分不能显示图,呵呵,留影,看看还会不会再出错07-07-17] 注意了, 有人反映显示为演示版无法使用, 其实是自己操作不当造成的! 如果仔细按照图做肯定能用. 今天偶然发现他们的问题出在哪里, 请注意二楼的特别说明! [ Last edit by maxwell] 仪器专场展示:电化学工作站电化学配件PH电极 关键词:zview拟合入门交流阻抗谱一步一步 收藏分享评分 maxwell ?技术 ?财富

?个人资料加为好友 ?给他留言帖子合集 沙发只看作者回复于:2006-9-12 19:32:00 回复本贴 回复主题编辑举报管理 2.数据格式要求: 只要是三列数据,如下图:实部、虚部和频率即可;(有人抱怨说,应该是频率、虚部+频率,呵呵,我原来也是顺手打了;这里顺便再纠正一个:虚部要是付的,有些仪器测试结果给出的是-z'',绘制origin到时方便了,但在这里拟合却麻烦了,好心办坏事^ ^。) 特别注意: 用不同仪器测试时导出的结果, 一般前面都有些题头, 记得一定要删除掉, 也就是开始就是数据!!! [ Last edit by maxwell] maxwell ?技术 ?财富

?个人资料加为好友 ?给他留言帖子合集 板凳只看作者回复于:2006-9-12 19:33:00 回复主题编辑举报管理 回复本贴 3.激活数据: [ Last edit by maxwell] maxwell ?技术 ?财富 ? ?个人资料加为好友 ?给他留言帖子合集 3# 只看作者回复于:2006-9-12 19:35:00 回复本贴 回复主题编辑举报管理

Y型过滤器与全程水处理器

Y型过滤器与全程水处 理器 Company Document number:WTUT-WT88Y-W8BBGB-BWYTT-19998

一、Y型过滤器 1.目数的定义:指物料的粒度或粗细度,一般定义是指在1英寸×1英寸 (×)的面积内有多少个网孔数,即筛网的网孔数。滤网目数越大,说明物料粒度越细;Y型过滤器目数越小,说明物料粒度越大。各国标准筛的规格不尽相同,常用的泰勒制是以每英寸长的孔数为筛号,称为目。例如100目的筛子表示每英寸筛网上有100个筛孔。 图1 Y型过滤器及滤网 2. Y型过滤器的目数选择 (1)网上答案:一般用于设备前起过滤作用保证设备安全,当介质为水时一般选择4-18目,当介质为蒸汽时一般选择40-90目。 (2)厂家答案:Y型过滤器是输送介质的管道系统不可缺少的一种过滤装置,Y型过滤器通常安装在减压阀、泄压阀、定水位阀或其它设备的进口端,用来清除介质中的杂质,以保护阀门及设备的正常使用。Y型过滤器具有结构先进,阻力小,排污方便等特点。Y型过滤器适用介质可为水、油、气。一般通水网为18~30目,通气网为10~100目,通油网为100~480目。 (3)规范中的答案(存在问题):《管道过滤器的设置》HG/(规范较老)中原文:“临时过滤器按结构可分为平板型、篮型、T型、Y型等。平板(多孔)型通常使用于离心泵的吸入管道上。篮型、T型、Y型通常使用于往复式压缩机或油类等粘度较大的液体的吸入管道上。临时过滤器使用的过滤网,一般选用100孔/cm2的滤网。” 经过计算可知,100孔/cm2=孔/英寸2≈645目,这个数大的离谱, 3. Y型过滤器的筛孔尺寸与标准目数对应 筛孔尺寸:标准目数:4目 筛孔尺寸:标准目数:5目

污水处理电化学处理技术

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8种电化学水处理方法

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