Crystalline structures in ultrathin poly(ethylene oxide)-poly(methyl methacrylate)

Crystalline structures in ultrathin poly(ethylene oxide)/poly(methyl

methacrylate)blend ?lms

Mingtai Wang *,Hans-Georg Braun *,Evelyn Meyer

Institute of Polymer Research Dresden,Hohe Strasse 6,D-01069Dresden,Germany Received 26May 2003;received in revised form 2June 2003;accepted 10June 2003

Abstract

Amorphous poly(ethylene oxide)/poly(methyl methacrylate)(PEO/PMMA)blend ?lms in extremely constrained states are meta-stable and phase separation of fractal-like branched patterns happens in them due to heterogeneously nucleated PEO crystallization by diffusion-limited aggregation.The crystalline branches are viewed ?at-on with PEO chains oriented normal to the substrate surface,upon increasing PMMA content the branch width remains invariant but thickness increases.It is revealed that PMMA imposes different effects on PEO crystallization,i.e.the length and thickness of branches,depending on the ?lm composition.q 2003Elsevier Science Ltd.All rights reserved.

Keywords:Crystallization;Poly(ethylene oxide);Surface pattern

1.Introduction

Even though polymer crystallization has been exten-sively studied during the past decades [1,2],the crystal-lization in ultrathin ?lms is a new topic in this ?eld.Special enthalpic and entropic factors at polymer/substrate interface cause the organization of polymer chains in ultrathin ?lms to deviate from their bulk states [3–6],and substrate adsorption effect,due to which polymer chains form stable loops dangling in the direction perpendicular to the substrate surface,reduces the thermodynamic potential of hetero-geneous nucleation for crystallization [7].Studying the crystallization in ultrathin polymer ?lms has offered a possibility to reveal polymer chain organization during crystallization in real space [8–15].However,observation of crystalline morphology has mainly been done in ultrathin ?lms containing only one polymer,and branched structures due to non-equilibrium crystallization by a diffusion-limited aggregation (DLA)process are always the case in the ?lms of a thickness less than 10nm,as shown by the terrace structures with ?ngers [8,9],the ?nger-like [10–13]and fractal-like [15]patterns.In forming these structures,

heterogeneous nucleation is necessary and polymer chains fold without in?uence of other polymers and by a stem length of 7–13nm.In this report we show the crystalline structures in ultrathin poly(ethylene oxide)/poly(methyl methacrylate)(PEO/PMMA)blend ?lms and the effects on PEO crystallization imposed by PMMA.

2.Experimental

Polyethylene glycol standard (M w ?6000;M w =M n ?1:03)from Fluka and PMMA standard (M w ?4200;M w =M n ?1:06)from Polymer Standards Services (PSS,Germany)were used as received to prepare PEO/PMMA blend ?lms.The radius of gyration,R g ;of a polymer chain is calculated by R g ?eNb 2=6T1=2;where N is the degree of polymerization and b the average statistical segment length.For b PMMA ?0:69nm [16],the R g of the PMMA chain is 1.77nm.According to the data in literature [17],the b PEO and R g of the PEO chain are calculated to be 0.70and 3.30nm,respectively.Au ?lms of 100nm thickness were prepared by thermal evaporation (rate 0.1nm/s)of gold on the glass slides primed with a Cr adhesive layer of 3nm thickness.PEO/PMMA blend ?lms were dip-coated on the Au ?lms from chloroform solutions (totally 1mg/ml)at an average lifting rate of 1.90mm/s.The coated polymer layers (given a refractive index of 1.5)

0032-3861/03/$-see front matter q 2003Elsevier Science Ltd.All rights reserved.

doi:10.1016/S0032-3861(03)00492-0

Polymer 44(2003)5015–5021

https://www.sodocs.net/doc/1716029663.html,/locate/polymer

*Corresponding authors.Tel.:t49-351-4658633;fax:t49-351-4658284.

E-mail addresses:mingtaiwang@https://www.sodocs.net/doc/1716029663.html, (M.Wang),braun@ipfdd.de (H.G.Braun).

had a thicknesseDTof2–3.0nm within the tested composition range(0–50%PMMA,by weight).For D# R g of the longest component(PEO),the?lms can be de?ned as extremely constrained two-dimensional ones[16,18].

To provide de?ned areas for studying crystallization by means of scanning electron microscopy(SEM)and atomic force microscopy(AFM),an newly-coated?lm was?rst scratched once with a razor blade after drying in the air for 15min,and then put immediately into a vacuum(in SEM sample chamber,ca.1026h Pa)to crystallize for about17h. For grazing incidence re?ection infrared(GIR-IR)spec-troscopy,the?lms that had been dried in the air for15min were crystallized in the vacuum for24h without scratching. The temperature in the vacuum chamber was estimated by ambient temperatures to be21–228C.In vacuum condition the moisture in?uence on crystallization was eliminated.

Film thickness was measured on an ELX-02C ellips-ometer(DRE GmbH,Germany;He–Ne laser source 632.8nm,708angle of incidence)in15–20min after coating when the?lm was still amorphous.GIR-IR spectra were recorded in vacuum on an IFS66V/S spectrometer (Bruker Co.),using a grazing incidence external re?ection stage(from SPECAC,incident angle808C)at a resolution of4cm21and1000scans and a bare Au?lm as reference. Optical microscopy(OM)observation was done on a light microscope(Zeiss/Sis,Germany)in dark-?eld mode in ambient conditions.SEM and AFM studies of the samples were performed immediately after crystallization,as described previously[15].

3.Results

As a typical blend system containing amorphous and semi-crystalline components,PEO/PMMA blend in bulk state has been studied by different means,such as differential scanning calorimetry(DSC)[19],nuclear magnetic resonance(NMR)[20],small-angle X-ray scatter-ing(SAXS)and small-angle neutron scattering(SANS)[21] and microscopy[22].In general,PEO and PMMA are miscible in melt and amorphous states resulting in a single concentration-dependent glass transition[23],addition of PMMA reduces the crystal growth rate[24,25]and crystal-linity[22,26]of PEO.The growth and melting of crystal lamellae of PEO spherulites in thin PEO/PMMA?lms have been revealed by hot-stage AFM[27].Recently,Ferreiro and co-workers[28]reported that the crystalline mor-phology in thin PEO/PMMA?lms(ca.200nm thick)can be tuned by?lm composition to get circular spherulites(50–100%PEO),seaweed morphology(40–50%PEO),sym-metric dendrites(30–40%PEO)and fractal structures(15–25%PEO).They also presented the growth dynamics of the symmetric dendrites with a focus on their growth pulsations [29],but how the?lm morphology is tuned by adding PMMA still remains unclear.In spite of the above extensive studies,we,to our knowledge,are still lacking the observation on the crystalline morphology in ultrathin PEO/PMMA?lms.

3.1.SEM and OM observations

After crystallization in vacuum for several hours(e.g. 17–18h),the blend?lms are decorated by branched structures stemming from the scratch line(Fig.1).The branched structures clearly resemble the fractals formed in electrodeposition[30,31]and bacterial growth[32].Fractal formation proceeds theoretically by DLA process[33,34]. Crystalline structures reminiscent of DLA process have been observed in ultrathin PEO?lms,for example,the ?nger-like pattern in PEO monolayers[10,11].Reasonably, the fractal-like structures here are related to PEO crystal-lization in the blend?lms by DLA process.Note that SEM observations of the fresh?lms showed that the PEO/PMMA ?lms were homogeneous,but the pure PEO?lm was dispersed with some PEO dots(ca.1m m in diameter and6–7nm in height)that should be due to de-wetting of PEO on the substrate during?lm formation because of the weak interaction between the Au surface and PEO[35];the non-scratched?lms were not found branched structures for at least1h when kept in the vacuum.

The branch growth depends strongly on?lm composition (Fig.1).Generally,both main branches and sub-branches became shorter with PMMA content.The branches were very long in90/10(?PEO/PMMA)?lm,and the substrate surface was covered mainly by the branches stemming from the scratch line(Fig.1(b));but the branches in75/25?lm were much shorter than those in90/10?lm and a large structureless area appeared in front of the branches(Fig. 1(c)).Further increasing PMMA content to40%,the branches along the scratch line became much shorter and a much larger structureless areas resulted in front of them (Fig.1(d)).In PEO?lm,the branches stemming from PEO dots were much longer than these from the scratch line,the substrate surface was mainly covered by the branches nucleated by PEO dots which should crystallize prior to the branch growth because of their higher thickness[11].

The scratch line was created for two purposes,to act as heterogeneous nucleation for crystallization and to provided de?ned areas for studying crystallization.Under an optical microscope,90/10?lm was observed to show,in about 3min after scratching with a needle(228C,33%relative humidity),the contrast change in the zones along the scratch line,indicating the starting of crystallization;however,we didn’t?nd evidently the crystal growth in75/25?lm for 25min after scratching.Therefore,the branched structures here were not a direct result of scratching[36],and the scratch line acted as a surface defect to nucleate polymer chains.In the case of50/50?lm,where the branches were normally very short,a fortuitous long branched structure was found stemming from the scratch line,as shown in Fig.

2.SEM revealed that the long structure grew actually along

a defect zone on the Au surface,which shows that the

M.Wang et al./Polymer44(2003)5015–5021 5016

structureless areas in front of the branches along the scratch line (Figs.1(d)and 2)consist of amorphous PMMA and PEO but the crystallization in them needs further hetero-geneous nucleation.

The crystallization in the ?lms (Fig.1)did take place in vacuum.On one hand,the time interval between the ?nish of scratching and the start of SEM vacuumization was very short (within ca.1min).On the other hand,if branch growth had ?nished before putting the ?lm into the vacuum the branches should mainly stem from the scratch line and those nucleated by PEO dots should be much shorter in PEO ?lm (Fig.1(a)).

3.2.GIR-IR measurements

Fig.3shows the GIR-IR spectra of the ultrathin ?lms.Detailed assignments of IR vibrations of PEO [35,37]and PMMA [38]have been described by https://www.sodocs.net/doc/1716029663.html,pared with the isotropic spectrum of bulk PMMA,the stretching band of methacrylate side group at 1100–1300cm 21is greatly enhanced relative to the C y O vibration at 1734cm 21in the ultrathin PMMA ?lm,indicating that the ?lm has more methoxy groups oriented normal to the Au surface than carbonyl groups and that PMMA is physically adsorbed onto the substrate due to interaction of the polar

methoxy

Fig.1.SEM images of the fractal-like structures in ultrathin PEO/PMMA ?lms of different blend compositions,(a)100/0,(b)90/10,(c)75/25and (d)60/40.The scale bar of 10m m is for all images.The samples were crystallized for 17

h.

Fig.2.A SEM image of the fractal-like structures in ultrathin PEO/PMMA ?lm of 50/50composition.The branches along the scratch line are normally very short in this sample (Inset).This image mainly shows a long branched structure stemming from the scratch line,which grew actually along a defect zone.The sample was crystallized for 17.5

h.

Fig.3.GIR-IR spectra of the ultrathin ?lms crystallized for 24h.The traces correspond to the weight ratios of PEO/PMMA marked on the curves.SEM veri?ed that the crystallization in blend ?lms started from surface defects (e.g.dust particles).

M.Wang et al./Polymer 44(2003)5015–50215017

and carbonyl groups with the Au surface[38].Reasonably, PMMA prevented PEO from de-wetting during the co-deposition of them from solution[35],resulting in homogeneous blend?lms.

The spectra of PEO at different temperatures[35,37] show that the intensity of the CH2wagging vibration of PEO at1342cm21is sensitive to the conformation order,which can be used to evaluate crystallization process[26].With respect to the CH2stretching vibration at around2888cm21 that is mainly attributed to PEO component,the change in the intensity of PEO band at1342cm21with PMMA content indicates that a higher PMMA content leads to a lower crystallinity of PEO in the?lm.As PMMA content is $40%the blend?lms are mainly amorphous.

Only bands with transition dipole moments parallel(k)to PEO chain axis(1342,1242,1107and963cm21)[35,37] are intensively observed in the GIR-IR spectra of ultrathin PEO and90/10?lms.In the spectrum of75/25?lm,the vibrations of k bands are still evident while they are much weaker than the90/10and PEO cases.In the?lms with PMMA content$40%the vibration signals of PEO crystals are very weak(1342cm21)and non-evident(963cm21)for the crystal branches in them were too short to be easily detected by the GIR-IR scans,but the orientation of the crystallized PEO chains in them can be reasonably inferred by the results of the90/10and75/25?lms since the?lms crystallized in the same condition.Thus,the PEO chains in the crystals formed in the studied?lms orient perpendicular to substrate surface and the branches are viewed?at-on, because in GIR-IR measurements only the transition dipole moment components normal to substrate surface can be observed.

3.3.AFM results

AFM measurements were performed to get the branch thickness,as shown in Fig.4.In the PEO?lm,the branches had a homogeneous thickness of8^1nm(Fig.4(a)). However,the branch thickness in the blend?lms veri?ed with PMMA content,namely,4^1nm in90/10?lm(Fig. 4(b)),6^1nm in75/25?lm(Fig.4(c))and10^1nm in 60/40and50/50?lms(Fig.4(d)).For PMMA phases may segregate beside the branches(refer to latter discussion),the actual branch thickness may be somewhat larger than the measured data in the blend?lms,particularly in those containing a high PMMA content.Notice that the branches in60/40and50/50?lms had a similar thickness by the AFM data(Fig.4(d)),but the branches in the50/50?lm may actually be thicker than those in60/40?lm because more PMMA can segregate beside the branches in50/50?lm.

As the branch growth mainly proceeds laterally and the PEO chains within the crystals take exclusively a confor-mation with chain axes perpendicular to substrate surface, one branch formed in the?lms studied here is reasonably a crystal lamella viewed?at-on and its thickness is related to the stem length of PEO chain folds within it.In pure PEO ?lm the thickness of such branches is a direct measure of chain folding states[11,12,15].The thickness of8^1nm (Fig.4(a))infers that PEO chains fold4times when without in?uence of PMMA,as the length L of the fully extended crystalline PEO chain is37nm according to L?eM PEO

n

=M EO nT￡0:2783nm[39].Even though the exact folding states of PEO chains in blend?lms,particularly as a?lm contains a high PMMA content,are hard to obtain from the AFM data(Fig.4(c)and(d))because of the possible discrepancy between the actual and measured values of the branch thickness,the tendency towards higher branches when increasing PMMA content will not be altered.Therefore,from the composition dependence of branch thickness one would get an evaluation of PMMA in?uences on the organization of PEO chains during crystallization.

4.Discussion

The amorphous PEO/PMMA blend?lms are obtained by constrained geometry and only meta-stable,phase separ-ation of fractal-like branched patterns happens in them due to heterogeneously nucleated PEO crystallization by DLA process.The PEO chains in the crystals come from the amorphous blend areas ahead of them[10–12,15],where PEO and PMMA are mixed.Results show that increasing PMMA content to more than10%leads to a remarkable retardation effect of PMMA on the branch length,and only the PEO chains near the heterogeneous nucleation sites in ?lms with PMMA content$40%can crystallize so that the ?lms are mainly amorphous(Figs.1–3).In bulk state,the blends with PMMA content higher than,70%are completely amorphous[19,22,40].This indicates that the retardation effect of PMMA on PEO crystallization is dramatically enhanced by constrained geometry in the ultrathin?lms.

Crystallization in the blend?lms involves the general features revealed in ultrathin PEO[10–12,15]and other polymer[8,9,14]?lms,namely,requiring necessary hetero-geneous nucleation,chain orientation normal to substrate surface and branched structures related to DLA process. Therefore,the crystal growth in the blend?lms obeys the basic principles in ultrathin polymer?lms,for example,the growth process is controlled by chain diffusion.It is believed that the retardation effect of PMMA on the branch growth is to reduce the transport property(mobility)of PEO chains in our cases,because upon increasing PMMA the mobility of PEO chains can be strongly reduced[20]and the system will become more rigid[22].

SEM and AFM provide detailed structural information on the crystals.These data contain several interesting features.First,as PMMA content was changed from10to 40%,the branch thickness increased strikingly from4^1 to10^1nm.Second,the branches in90/10?lm were much thinner than those in PEO?lm.Finally,the branch

M.Wang et al./Polymer44(2003)5015–5021 5018

width (ca.0.20m m)in the blend ?lms was independent of PEO/PMMA ratio,but smaller than that of the branches formed in the PEO ?lm.As mentioned previously,the branch thickness is directly related to the chain folding during crystallization and can give an access to the information on the organization of PEO chains under PMMA in?uence.

The thickness of the crystalline branches is determined by the kinetics of chain deposition at crystal growth fronts in diffusion-controlled growth process [11,12,15].A lowered chain deposition rate,which was achieved by evaluating crystallization temperature eT c T[11]and by reducing the polymer concentration in diffusion ?eld [15],has been proved in ultrathin PEO ?lms to favor the growth of thicker branches.Reiter and Sommer [11,12]showed that the thickness of crystal lamellae increases with crystallization temperature.They argued that at a high deposition rate (large undercooling)the molecules attached to the crystal have less time to stretch out and are thus in a state of relatively low internal chain order (folded state);in contrast,if the crystals grow slowly,the attached molecules have more time to relax towards the fully extended form of lowest free energy by rearrangements at the crystal surface.Our previous results [15]showed that,as a result of the reduction of chain availability in the diffusion ?eld,the chain deposition rate (or probability)at crystal growth fronts becomes small and the deposited polymer chains have a high probability to rearrange themselves to a state near equilibrium.

In our opinion,the increase in branch thickness with PMMA content in the blend ?lms results from the lowered chain deposition rate by adding PMMA (Fig.4(b)–(d)).PMMA has a high glass transition temperature eT g T;but PEO have a low one.As a consequence of mixing these

two

Fig.4.AFM images of the fractal-like structures in ultrathin PEO/PMMA ?lms of different blend compositions,(a)100/0,(b)90/10,(c)75/25(c)and (d)60/40.The inset to (d)is for 50/50?lm.The samples were crystallized for 17h and measured by means of non-contact AFM immediately after being taken out of the vacuum chamber;the scanned areas were near scratch line.All the branches were nucleated by the scratch lines,except for those in the left side of image (a)that were nucleated by a PEO dot.

M.Wang et al./Polymer 44(2003)5015–50215019

miscible polymers,the amorphous phase T g increases as the

concentration of PMMA increases[23],resulting in a more

rigid crystallization system with a more reduced mobility of

PEO chains.The reduction of PEO chain mobility will

inevitably lower the chain deposition rate at crystal growth

fronts,leading to an easier relaxation of the deposited chains

towards the extended state and further higher branches as

described elsewhere[11,15].

In a blend consisting of a semi-crystalline polymer and

an amorphous one the equilibrium melting pointeT m80T

depends on composition,increasing amorphous concen-

tration will depress T m80[24,41,42].One question may arise,

concerning whether the origin of the increase in branch

thickness with PMMA content comes from the decrease in

the effective undercooling D TeD T?T m802T cTat which

crystallization occurs.T m80in PEO/PMMA blends decreases

with increase of PMMA content in the blends[24,41],but

the decreases is slight and only a maximum depression of

ca.2.58C was observed[24].In spite of the depression of

T m80;moreover,the crystalline thickness in PEO/PMMA blends is independent of composition[21,41],but increases

with T c:The equilibrium melting pointeT o mTof the pure PEO used in this study was ca.648C,which was obtained by

referring to the data of a similar PEO(M w?6000;

M w=M n?1:03;from Fluka Co.)in literature[24].There is no reason to believe that the increase in branch thickness with increasing PMMA content in our cases results mainly from the decrease in the effective undercooling,of which the contribution would be very faint if it could not be completely ruled out because the T c in our experiments was about428C below the T o m of the pure PEO.

Interestingly,the branches in90/10?lm were much

thinner than those in PEO?lm(Fig.4(a)and(b)),which

should not be caused by the PMMA segregating beside the

branches in the blend?lm because PMMA content was

rather low.A slow deposition rate of PEO chains at growth

fronts favors the formation of higher branches,whereas a

fast deposition rate will result in thinner branches[11,15].It

is clear that the crystallization was accelerated in90/10?lm

as compared with that in PEO?lm.The crystal growth was

also found to be enhanced in90/10blend of PEO/isotactic-

PMMA(i-PMMA)when compared to the pure PEO,rather

than being disrupted,this phenomenon was considered to

relate to the immiscibility between PEO and i-PMMA[25].

Therefore,two competitive effects may be imposed by

PMMA on PEO crystallization depending on the?lm

composition,to retard the crystallization by reducing the

mobility of PEO chains and to accelerate the crystallization

by probably de-mixing,where the latter effect is dominant

as PMMA concentration is low but the former one will be

enhanced by increasing PMMA content(Fig.4).

As shown previously[15],a surface-tension effect,

which favors the minimized interface area of crystal growth

fronts,is coming into effect with the reduction in deposition

rate of chains and the deposited chains will occupy a highest

number of nearest neighbors at the growth fronts.With this consideration,one might expect a broadening of branches as the deposition rate reduces with increasing PMMA content. However,the branch width(ca.0.20m m)in the blend?lms is independent of?lm composition and generally smaller than that in PEO?lm(Figs.1and4).No external factors could impose in?uences on the branch width in our experiments,except for the presence of PMMA in the system.On the other hand,the width difference between the branches in the blend and PEO?lms could not result from the two competitive effects imposed by PMMA in that the branch width did not changed with increasing PMMA content.The possible origin of the small and constant branch width in blend?lms lies in the laterally excluded PMMA phases from the crystals,which can be rationalized by the fact that the‘impurities’(PMMA)segregate away from the growth front and between the growing lamellae during the growth of PEO spherulites in thin PEO/PMMA ?lms[27]and by the invariant crystalline lamellar thickness and increasing small-angle long period of crystalline phases with addition of PMMA[21,41].The deposition of PEO chains at the side faces of branches can be prevented by the excluded PMMA phases,but this will not be the case in the PEO?lm.

5.Conclusion

The results presented in this study show the crystalline morphology in ultrathin PEO/PMMA blend?lms.The blend?lms in extremely constrained states are amorphous and meta-stable,and phase separation in them follows a fractal-like branched pattern due to heterogeneously nucleated PEO crystallization by DLA process.The crystal branches are viewed?at-on with polymer chains oriented normal to the substrate surface;the PEO chains in the crystalline branches come from the amorphous blend areas ahead of them.The branch width in blend?lms is independent of the?lm composition,which relates to the laterally excluded PMMA phases from the crystals.The presence of PMMA in?uences strikingly the branch length and thickness by imposing two competitive effects on the PEO crystallization,to accelerate and to retard the crystal-lization,depending on the?lm composition.The acceler-ated crystallization,probably by de-mixing between PEO and PMMA,leads to thinner and longer crystal branches; the retardation effect of PMMA,which results in thicker and shorter crystal branches,is attributed to reducing the mobility of PEO chains in the system. Acknowledgements

The authors thank the DFG for supporting this work (priority program‘Wetting and structure formation at surfaces’).M.Wang acknowledges the Alexander von Humboldt Foundation for a research fellowship.

M.Wang et al./Polymer44(2003)5015–5021 5020

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M.Wang et al./Polymer44(2003)5015–50215021

小学joinin剑桥英语单词汇总

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1N系列常用整流二极管的主要参数

1N 系列常用整流二极管的主要参数
反向工作 峰值电压 URM/V 额定正向 整流电流 整流电流 IF/A 正向不重 复浪涌峰 值电流 IFSM/A 正向 压降 UF/V 反向 电流 IR/uA 工作 频率 f/KHZ 外形 封装
型 号
1N4000 1N4001 1N4002 1N4003 1N4004 1N4005 1N4006 1N4007 1N5100 1N5101 1N5102 1N5103 1N5104 1N5105 1N5106 1N5107 1N5108 1N5200 1N5201 1N5202 1N5203 1N5204 1N5205 1N5206 1N5207 1N5208 1N5400 1N5401 1N5402 1N5403 1N5404 1N5405 1N5406 1N5407 1N5408
25 50 100 200 400 600 800 1000 50 100 200 300 400 500 600 800 1000 50 100 200 300 400 500 600 800 1000 50 100 200 300 400 500 600 800 1000
1
30
≤1
＜5
3
DO-41
1．5
75
≤1
＜5
3
DO-15
2
100
≤1
＜10
3
3
150
≤0.8
＜10
3
DO-27
常用二极管参数： 05Z6.2Y 硅稳压二极管 Vz=6~6.35V,Pzm=500mW,

(完整版)JOININ小学三年级英语(上册)重点知识归纳

小学三年级英语（上册）重要知识点归纳 一、单词 Unit 1学习文具：pen (钢笔) pencil (铅笔) pencil-case ( 铅笔盒) ruler(尺子) eraser(橡皮) crayon (蜡笔) book (书) bag (书包) sharpener (卷笔刀) school (学校) Unit 2身体部位：head (头) face( 脸) nose (鼻子) mouth (嘴) eye (眼睛)leg (腿) ear (耳朵) arm (胳膊)finger (手指) leg (腿) foot (脚)body (身体) Unit 3颜色：red (红色的) yellow (黄色的)green (绿色的)blue (蓝色的) purple (紫色的) white (白色的) black (黑色的) orange (橙色的) pink (粉色的)brown (棕色的) Unit 4动物：cat (猫)dog (狗)monkey (猴子)panda (熊猫)rabbit( 兔子) duck (鸭子)pig (猪)bird (鸟) bear (熊)elephant (大象)mouse (老鼠) squirrel (松鼠) Unit 5食物：cake (蛋糕)bread (面包) hot dog (热狗) hamburger (汉堡包) chicken (鸡肉)French fries (炸薯条)coke (可乐)juice (果汁)milk (牛奶) water (水)tea (茶) coffee (咖啡) Unit 6数字：one (一) two (二) three (三)four (四) five (五)six( 六)seven (七) eight (八) nine( 九) ten( 十)doll (玩具娃娃) boat (小船)ball (球) kite (风筝) balloon (气球) car (小汽车)plane (飞机) 二、对话 1、向别人问好应该说――A: Hello! (你好!) B: Hi! (你好!) 2、问别人的名字应该说-――A：What's your name? 你的名字是什么? B：My name's Chen Jie. 我的名字是陈洁。 3、跟别人分手应该说――A: Bye.\ Good bye!(再见) B: See you.(再见) \ Goodbye.(再见) 4、A: I have a pencil\ bag\ruler 我有一只铅笔\书包\尺子。 B: Me too . 我也有。 5、早上相见应该说-――A: Good morning. 早上好!

常见二极管参数大全

1N系列稳压管

快恢复整流二极管

常用整流二极管型号和参数 05Z6.2Y 硅稳压二极管 Vz=6~6.35V,Pzm=500mW, 05Z7.5Y 硅稳压二极管 Vz=7.34~7.70V,Pzm=500mW, 05Z13X硅稳压二极管 Vz=12.4~13.1V,Pzm=500mW, 05Z15Y硅稳压二极管 Vz=14.4~15.15V,Pzm=500mW, 05Z18Y硅稳压二极管 Vz=17.55~18.45V,Pzm=500mW, 1N4001硅整流二极管 50V, 1A,(Ir=5uA,Vf=1V,Ifs=50A) 1N4002硅整流二极管 100V, 1A, 1N4003硅整流二极管 200V, 1A, 1N4004硅整流二极管 400V, 1A, 1N4005硅整流二极管 600V, 1A, 1N4006硅整流二极管 800V, 1A, 1N4007硅整流二极管 1000V, 1A, 1N4148二极管 75V, 4PF,Ir=25nA,Vf=1V, 1N5391硅整流二极管 50V, 1.5A,(Ir=10uA,Vf=1.4V,Ifs=50A) 1N5392硅整流二极管 100V,1.5A, 1N5393硅整流二极管 200V,1.5A, 1N5394硅整流二极管 300V,1.5A, 1N5395硅整流二极管 400V,1.5A, 1N5396硅整流二极管 500V,1.5A, 1N5397硅整流二极管 600V,1.5A, 1N5398硅整流二极管 800V,1.5A, 1N5399硅整流二极管 1000V,1.5A, 1N5400硅整流二极管 50V, 3A,(Ir=5uA,Vf=1V,Ifs=150A) 1N5401硅整流二极管 100V,3A, 1N5402硅整流二极管 200V,3A, 1N5403硅整流二极管 300V,3A, 1N5404硅整流二极管 400V,3A,

JOININ英语三年级下册课本重点

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stand nose to nose 鼻子对鼻子站着 Unit 1 Pets 1 Words cat猫dog狗bird 鸟mouse老鼠fish鱼rabbit 兔子frog青蛙hamster仓鼠 budgie鹦鹉tiger老虎monkey 猴子panda熊猫giraffe 长颈鹿elephant 大象bear 熊run跑sit坐fly飞swim游泳roar吼叫eat吃 2 Grammar ★名词的复数:一般在词尾直接加s,不规则变化要牢记: fish-----fish mouse------mice 3 Sentences 1.Have you got a pet ? 你有宠物吗?Yes ,I have. 是的,我有。/No, I haven’t. 不,我没有。 2.2. What have you got ? 你有什么宠物吗?I’ve got a dog . / A dog. 我有一只狗。 3.What colour is the cat ? 你的猫是什么颜色的?It’s black. 它是黑色的。 What iswizard’s pet? 巫师的宠物是什么? 4.What is it ? 它是什么? It’s a rabbit .它是只兔子。

三年级下学期英语(Joinin剑桥英语)全册单元知识点归纳整理-

Starter Unit Good to see you again知识总结 一. 短语 1. dance with me 和我一起跳舞 2. sing with me 和我一起唱歌 3. clap your hands 拍拍你的手 4. jump up high 高高跳起 5.shake your arms and your legs晃晃你的胳膊和腿 6. bend your knees 弯曲你的膝盖 7. touch your toes 触摸你的脚趾8. stand nose to nose鼻子贴鼻子站 二. 句子 1. ---Good morning. 早上好。 ---Good morning, Mr Li. 早上好，李老师。 2. ---Good afternoon. 下午好。 ---Good afternoon, Mr Brown. 下午好，布朗先生。 3. ---Good evening，Lisa. 晚上好,丽莎。 ---Good evening, Bob. 晚上好，鲍勃。 4. ---Good night. 晚安。 ----Good night. 晚安。 5. ---What’s your name? 你叫什么名字？ ---I’m Bob./ My name is Bob. 我叫鲍勃。 6. ---Open the window, please. 请打开窗户。 ---Yes ,Miss. 好的，老师。 7. ---What colour is it? 它是什么颜色？ 它是蓝红白混合的。 ---It’s blue, red and white. 皮特的桌子上是什么？ 8. ---What’s on Pit’s table? ---A schoolbag, an eraser and two books. 一个书包，一个橡皮和两本书。 9. ---What time is it? 几点钟？ 两点钟。 ---It’s two. 10.---What’s this? 这是什么？ ---My guitar. 我的吉他。

JOININ英语三年级下册知识点

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★名词的复数：一般在词尾直接加s,不规则变化要牢记: fish-----fish mouse------mice 3 Sentences 1.Have you got a pet ? 你有宠物吗？ Yes ,I have. 是的,我有。/No, I haven’t. 不，我没有。 2.What have you got ? 你有什么宠物吗？I’ve got a dog . / A dog. 我有一只狗。 3.What colour is the cat ? 你的猫是什么颜色的？It’s black. 它是黑色的。 What is wizard’s pet? 巫师的宠物是什么？ 4.What is it ? 它是什么? It’s a rabbit .它是只兔子。 5.How many budgies /mice are there? 这里有多少只鹦鹉/老鼠？ There are + 数字budgies/mice. 这里有------只鹦鹉/老鼠。 6.Fly like a budgie. 像鹦鹉一样飞。Run like a rabbit. 像兔子一样跑。 Swim like a fish. 像鱼一样游泳。Eat like a hamster. 像仓鼠一样吃东西。 Sit like a dog. 像狗一样坐。Roar like a tiger. 像老虎一样吼叫。 7.What are in the pictures. 图片里面是什么？Animals. 动物。 8. What animals? 什么动物？ 9.How many pandas (elephants /bears/ giraffes/ monkeys/ budgies) are there?有多少.？ How many + 可数名词的复数形式 Unit 2 The days of the week

RBT214-2017检验检测机构通用要求

检验检测机构资质认定能力评价检验检测机构通用要求 RB/T214-2017 4 要求 4.1机构 4.1.1 检验检测机构应是依法成立并能够承担相应法律责任的法人或者其他组织。检验检测机构或者其所在的组织应有明确的法律地位，对其出具的检验检测数据、结果负责，并承担相应法律责任。不具备独立法人资格的检验检测机构应经所在法人单位授权。 4.1.2 检验检测机构应明确其组织结构及管理、技术运作和支持服务之间的关系。检验检测机构应配备检验检测活功所需的人员、设施、设备、系统及支持服务。 4.1.3 检验检测机构及其人员从事检验检测活动，应遵守国家相关法律法规的规定，遵循客观独立、公平公正、诚实信用原则，恪守职业道德，承担社会责任。 4.1.4 检验检测机构应建立和保持维护其公正和诚信的程序。检验检测机构及其人员应不受来自内外部的、不正当的商业、财务和其他方面的压力和影响，确保检验检测数据、结果的真实、客观、准确和可追溯。检验检测机构应建立识别出现公正性风险的长效机制。如识别出公正性风险，检验检测机构应能证明消除或减少该风险。若检验检测机构所在的组织还从事检验检测以外的活动，应识别并采取措施避免潜在的利益冲突。检验检测机构不得使用同时在两个及以上检验检测机构从业的人员。 4.1.5 检验检测机构应建立和保持保护客户秘密和所有权的程序，该程序应包括保护电子存储和传输结果的的要求。检验检测机构及其人员应对其在检验检测活功中听知悉的国家秘密、商业秘密和技术秘密负有保密义务，并制定和实施相应的保密措施。 4.2 人员

4.2.1 检验检测机构应建立和保持人员管理程序，对人员资格确认、任用、授权和能力保持等进行规范管理。检验检测机构应与其人员建立劳动、聘用或录用关系，明确技术人员和管理人员的岗位职责、任职要求和工作关系，使其满足岗位要求并具有所需的权力和资源，履行建立、实施、保持和持续改进管理体系的职责。检验检测机构中所有可能影响检验检测活动的人员。无论是内部还是外部人员,均应行为公正，受到监督,胜任工作，并按照管理体系要求履行职责。 4.2.2 检验检测机构应确定全权负责的管理层，管理层应履行其对管理体系的领导作用和承诺： a.对公正性做出承诺； b.负责管理体系的建立和有效运行； c.确保管理体系所需的资源； d.确保制定质量方针和质量目标； e.确保管理体系要求融入检验检测的全过程； f.组织管理体系的管理评审； g.确保管理体系实现其预期结果； h.满足相关法律法规要求和客户要求； i.提升客户满意度； j.运用过程方法建立管理体系和分析风险、机遇。 4.2.3 检验检测机构的技术负责人应具有中级及以上相关专业技术职称或同等能力，全面负责技术运作；质量负责人应确保质量管理体系得到实施和保持;应指定关键管理人员的代理人。 4.2.4 检验检测机构的授权签字人应具有中级及以上专业技术职称或同等能力,并经过资质认定部门批准,非授权签字人不得签发检验检测报告或证书。 4.2.5 检验检测机构应对抽样、操作设备、检验检测、签发检验检测报告或证书以及提出意见和解释的人员，依据相应的教育、培训、技能和经验进行能力确认。应由熟悉检验检测目的、程序、方法和结果评价的人员，对检验检测人员包括实习员工进行监督。 4.2.6 检验检测机构应建立和保持人员培训程序，确定人员的教育和培训目标，明确培训需求和实施人员培训，并评价这些培训活动的有效性。培训计划应