Development of nanocrystals in amorphous Al-alloys
Development of nanocrystals in amorphous Al-alloys
N.Boucharat *,H.Ro ¨sner,G.Wilde
Forschungszentrum Karlsruhe,Institut fu ¨r Nanotechnologie,P .O.Box 3640,76021Karlsruhe,Germany
Abstract
Rapidly quenched aluminum-based metallic glasses have been found to undergo a partial transformation upon heating that yields a fine-scaled dispersion of Al-nanocrystals within an amorphous matrix.The origin of the nanocrystallisation process is discussed based upon
calorimetric and structural investigations of Al 92Sm 8samples prepared using different processing pathways.Additionally,the early stages of the nanocrystal development was monitored by isothermal calorimetry techniques on long time scales.The results strongly indicate that the nanocrystals originate from quenched-in nuclei.Isothermal annealing of Al 88Y 7Fe 5glasses at 245j C revealed that a -Al nanocrystals develop at temperatures well below the primary crystallisation onset temperature after short time periods.On annealing,an additional phase evolves,which gives an exothermic signal in DSC at about 330j C.XRD measurements have been performed to study the phase formation sequence at high temperature.The formation of additional phases is related to a modification of the matrix composition near the nanocrystal/amorphous interface due to a pronounced concentration gradient as a result of the unequal component diffusivities.D 2002Elsevier Science B.V .All rights reserved.
Keywords:Al-alloys;Amorphous;Nanocrystals;Primary crystallisation;Transient phase
1.Introduction
Many metallic glasses including Al-based systems require rapid solidification to avoid crystallisation and to allow the formation of an amorphous phase.Upon heating,they often do not display a detectable glass transition signal but instead an exothermic maximum indicating a partial transformation that leads to a fine-scaled dispersion of 1021–1022m à3Al-nanocrystals of about 20nm in diameter within an amorphous matrix [1].This high number density of Al-nanocrystals is related to a crystal growth limitation and at the same time yields a high tensile strength of the nanocomposite material much higher than the respective values for the crystalline counterpart [2].Yet,the origin of the nanocrystallisation process is still a matter of active research [3].In the current work,glassy Al 92Sm 8and Al 88Y 7Fe 5alloys serve as model systems to investigate the origin of the nanocrystallisation process.Both systems are known [4,5]to yield similar product microstructures during the initial crystallisation reaction.However,the different absolute values for the transformation temperatures enable the use of different analysis tools and synthesis
procedures as described below.The unequal component diffusivities induce pronounced concentration gradients at the nanocrystal/amorphous interface [6,7]which strongly affect the crystallisation kinetics involving different kinetic regimes and different constraints for the precipitation of transient phases [8,9].In order to study the kinetics of the crystallisation process in detail,quantitative structural and calorimetric investigations have been performed and the phase formation sequences at higher temperatures and their modification after isothermal annealing have been studied.
2.Experimental procedures
Glassy ribbons with an approximate thickness of 40A m were produced from pre-alloyed ingots of Al (99.999%),Sm (99.9%),Y (99.9%)and Fe (99.995%)using a single-roller melt-spinning technique applying a fast rotating copper wheel.The sample homogeneity was ensured by pre-syn-thesis of the alloys in an arc-melting facility.XRD measure-ments on both sides of Al 92Sm 8and Al 88Y 7Fe 5samples as well as careful microstructural analyses performed by TEM/SAED have confirmed the absence of any detectable crys-talline fractions in the as-spun ribbon.Repeated cold-rolling was performed to yield a partially amorphous Al 92Sm 8sample with a thickness of 80A m.This processing route is governed by a deformation-driven mixing of the pure
0928-4931/02/$-see front matter D 2002Elsevier Science B.V .All rights reserved.PII:S 0928-4931(02)00230-8
*Corresponding author.Tel.:+49-7247-826450;fax:+49-7247-826434.
E-mail address:nancy.boucharat@int.fzk.de (N.Boucharat).
https://www.wendangku.net/doc/4911664695.html,/locate/msec
Materials Science and Engineering C 23(2003)55
–59
elements at room temperature[10].The sample was annealed at150j C in order to allow for relaxation of the vitreous state and to promote the development of any Al-nanocrystals.Energy dispersive X-ray analysis(EDX)con-firmed that the composition of all our samples corresponds to the nominal starting composition within the accuracy of the EDX-measurement(F0.5at.%).Microstructural inves-tigations were carried out by X-ray diffraction(Philips XRD)using Mo–K a radiation,scanning electron micro-scopy(SEM,Leo1530)and transmission electron micro-scopy/selected area electron diffraction(TEM/SAED, Philips CM30ST)techniques.TEM samples were prepared by twin-jet electropolishing(1/3nitric acid and2/3meth-anol)to avoid any sample-heating effects on the final microstructure as it was previously noticed using ion beam thinning.Continuous heating and isothermal annealing were monitored by differential scanning calorimetry(DSC,Per-kin Elmer,Pyris1)by which signals of about1A W can reproducibly be analysed.A microcalorimeter(Thermomet-ric,2277TAM)was used for the isothermal measurements on long time scales.
3.Results
3.1.Nanostructure development
The DSC signals on heating Al92Sm8samples,which were vitrified by cold-rolling or melt-spinning,respectively,are given in Fig.1.The repeatedly cold-rolled sample in Fig.1a displays an endothermic glass transition signal at about172j C.The TEM bright-field image given in Fig.1c, taken after annealing the sample at150j C for60min,does not show any signs of crystallinity within the amorphous region.In contrast,the DSC trace of the rapidly quenched sample exhibits a non-symmetrical exothermic signal at178 j C,well below the onset of the eutectic reaction that is characteristic for Al-nanocrystallisation(Fig.1b).The TEM bright-field image in Fig.1d reveals that Al-nanocrystals do develop within the amorphous matrix after annealing at150 j C for10min with a high number density of3.5?1022 mà3.In the case of homogeneous nucleation,the processing route should not affect the nanocrystal development since thermally driven fluctuations govern this process.Based upon these experimental results,the apparent variations in the thermal traces of both samples indicate that the for-mation of the large nanocrystal number densities is inher-ently coupled to the presence of a high nucleation site density in the undercooled melt[5,6].In order to monitor the early stages of nanocrystal development at temperature below T g in more detail,isothermal microcalorimetry meas-urements on long time scales have been performed at120 and130j C(Fig.2).For these measurements,the micro-calorimeter has been equilibrated at the respective temper-atures prior to the insertion of the specimen.Thus,it was ensured that the microstructure did not change before the onset of the microcalorimetry measurement.The baseline measured for about7days indicates the absence of
any Fig.1.DSC curves obtained during continuous heating at20j C minà1(a)of a Al92Sm8cold-rolled sample and(b)of a Al92Sm8as-spun ribbon.TEM and SAED patterns(c)of a cold-rolled sample after annealing at150j C for60min and(d)of an as-spun ribbon after annealing at150j C for10min.
N.Boucharat et al./Materials Science and Engineering C23(2003)55–59
56
instrumental transient effect that exceed the scatter of the data (0.025A W/h).Under identical conditions,the temper-ature of the samples was maintained with an accuracy better than 2?10à4j C.The sample measurements show a monotonically decreasing signal as well as the absence of any maximum in the heat flow signal.These results indicate that the nanocrystallisation process is controlled by the diffusional growth of nuclei formed during rapid melt quenching and not by a nucleation and growth process of the Al-nanocrystals within the amorphous state [11].Regarding this result,a qualitative time–temperature–trans-formation (TTT)curve has been proposed [10]showing that during quenching the cooling rate is not high enough and thus intersects with the TTT curve of the Al.Alternatively,a cluster distribution with an average size larger than the critical size for growth at large undercooling could be retained in the material after the rapid quench.3.2.Transient phase formation
DSC curves of the as-spun Al 88Y 7Fe 5samples during continuous heating (Fig.3a)display a primary crystallisa-tion peak with an onset at about 276j C that is followed by a sharp crystallisation signal at 374j C.Careful XRD measurements have shown that the primary crystallisation peak corresponds to the formation of fcc-Al-nanocrystals within the amorphous matrix (Fig.4)and the following peak to the formation of the intermetallic Al 3Y(Fe)phase from the remaining amorphous matrix.The similarity of the XRD profiles (Fig.4a and b)confirms that no crystalline phase except the Al-nanocrystals is formed during the initial crystallisation reaction.Though the DSC curve obtained on continuous heating indicates that the primary crystallisation starts at 276j C,isothermal
annealing investigations at 245j C revealed that a -Al nanocrystals can slowly develop at temperatures well below the primary crystallisation onset temperature.The development of the Al-nanocrystals is coupled to the slow disappearance of the primary crystallisation signal with increasing annealing time,indicating the sluggish growth of the nanocrystals (Fig.3).This result has been confirmed by XRD measurements and TEM analyses showing that a small fraction of Al-nanocrystals develops in the samples that are isothermally held at 245j C for 10and 30min,respectively.The dark-field TEM images in Fig.3f exhibit the evolution of the small Al-nanocrystals from a spherical shape to a dendritic morphology during isothermal anneal-ing at 245j C,probably as a result of large concentration gradients that develop at the nanocrystal/amorphous inter-face due to limited diffusion of the RE-element that cause the instability of the interface [4,6].At early stages of the isothermal annealing treatment the diffusion fields do not overlap.During nanocrystal growth,the interparticle dis-tance decreases and the amorphous matrix surrounding the nanocrystals is enriched in solute.Both effects lead to an overlap of the diffusion fields with a soft diffusion field impingement that causes the formation of pronounced concentration gradients at the nanocrystal/amorphous inter-face as shown by kinetics modelling [6]and direct experimental investigations [7].The nanocrystal growth velocity is then considerably reduced and effectively con-trolled by the slow-diffusing species [12].In order to study the impact of the concentration gradient on the phase evolution in more detail,continuous heating experiments have been carried out on samples that had been annealed at 245j C for different periods of time.Fig.3gives
repre-
Fig.3.Continuous heating DSC traces at 20j C min à1of a Al 88Y 7Fe 5ribbon (a)as-spun and after isothermal annealing at 245j C (b)for 10min,(c)30min,(d)60min and (e)100min,respectively.TEM dark-field images are included showing the evolution of nanocrystals from a spherical shape to a dendritic morphology in samples annealed at 245j C for 10and 30min
(f).
Fig. 2.Heat flow evolved during isothermal annealing of an as-spun Al 92Sm 8ribbon at 120and 130j C,respectively,together with the baseline.
N.Boucharat et al./Materials Science and Engineering C 23(2003)55–5957
sentative examples of the typical thermal responses of the pre-annealed samples that expose an additional peak in the range of 320–360j C between the primary and interme-tallic crystallisation peak.The crystallisation sequence was studied by XRD on the samples annealed for 30and 60min and compared to the crystallisation sequence of the as-spun sample (Fig.4).The XRD spectra indicate the formation of Al nanocrystals in the amorphous matrix of the annealed sample,after heating to temperature up to 310j C,as also found for the as-spun sample.Further exami-nations after continuous heating up to 355j C show additional peaks (Fig.4d and e),which were not observed in the as-spun sample after heating to 348j C at an identical rate.Calculated diffusion fields of yttrium between two adjacent nanocrystal particles have shown that a rather high concentration gradient near the interface (>106m à1)is reached in the initial stages of the nano-crystal growth,which is sufficient to inhibit the nucleation of transient phases [6].Moreover,thermodynamic and kinetic approaches [8,9]have demonstrated the existence of a critical value of the concentration gradient below which the nucleation of transient phase is allowed.Based upon these results,the transient appearance of transforma-tion signals at intermediate temperatures (Fig.3c–e)is related to the important contribution of the concentration gradient that favours or suppresses the formation of the transient phase.These results further indicate that the
phase formation sequence can be modified by controlling the concentration gradient at the interface.
4.Summary
The combination of different synthesis routes and anal-ysis methods as well as the isothermal microcalorimetry measurements at temperatures below T g indicate that the nanocrystal development during annealing of Al-rich glasses such as Al–Sm and Al–Y–Fe is related to the formation of precursor nuclei during rapid quenching.In such systems,the large disparities of the component diffu-sivities cause a soft diffusion field impingement between neighboring nanocrystals during primary crystallisation [6,7].In that sense,the solute rejection during nanocrystal growth itself provides for a kinetic stabilisation of the nanoscaled microstructure.These results serve as a basis for an understanding and a description of the kinetics of the nanocrystallisation process and indicate that a microstruc-ture control on the nanoscale requires the control of the nucleation site density in the molten material.Further,the diffusional control that is operative in these alloys leads to a modification of the local composition of the amorphous matrix at the interface that modifies the nucleation kinetics of intermediate phases.These observations indicate that the concentration gradient affects the phase evolution
sequence
Fig.4.XRD profiles of Al 88Y 7Fe 5as-spun samples after heating to (a)315j C and (b)348j C together with the XRD profiles of Al 88Y 7Fe 5ribbons isothermally held at 245j C for 30min and re-heated up to (c)310j C and (d)355j C as well as (e)Al 88Y 7Fe 5ribbons isothermally held at 245j C for 60min and re-heated up to 355j C.The peaks corresponding to fcc-Al (A )and the transient phase (.)are indicated.
N.Boucharat et al./Materials Science and Engineering C 23(2003)55–59
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and that an opportunity for active phase selection is given by controlling the concentration gradient.
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英语中的比较级与最高级 详解
比较级与最高级 1.as...as 与(not) as(so)...as as...as...句型中，as的词性 第一个as是副词，用在形容词和副词的原级前，常译为“同样地”。第二个as是连词，连接与前面句子结构相同的一个句子(相同部分常省略)，可译为“同..... He is as tall as his brother is (tall) . (后面的as 为连词) 只有在否定句中，第一个as才可换为so 改错: He is so tall as his brother.（X） 2.在比较状语从句中，主句和从句的句式结构一般是相同的 与as...as 句式中第二个as一样，than 也是连词。as和than这两个连词后面的从句的结构与前面的句子大部分情况下结构是相同的，相同部分可以省略。 He picked more apples than she did. 完整的表达为: He picked more apples than she picked apples. 后而的picked apples和前面相同，用did 替代。 He walked as slowly as she did.完整表达为: He walked as slowly as she walked slowly. she后面walked slowly与前面相同，用did替代。
3.谓语的替代 在as和than 引导的比较状语从句中，由于句式同前面 主句相同，为避免重复，常把主句中出现而从句中又出现的动词用do的适当形式来代替。 John speaks German as fluently as Mary does. 4.前后的比较对象应一致 不管后面连词是than 还是as,前后的比较对象应一致。The weather of Beijing is colder than Guangzhou. x than前面比较对象是“天气”，than 后面比较对象是“广州”，不能相比较。应改为: The weather of Bejing is colder than that of Guangzhou. 再如: His handwriting is as good as me. 应改为: His handwriting is as good as mine. 5.可以修饰比较级的词 常用来修饰比较级的词或短语有: Much,even,far,a little,a lot,a bit,by far,rather,any,still,a great deal等。 by far的用法: 用于强调，意为“...得多”“最最...”“显然”等，可修饰形容词或副词的比较级和最高级，通常置于其后，但是若比较级或最高级前有冠词，则可置于其前或其后。
五年级上册成语解释及近义词反义词和造句大全.doc
五年级上册成语解释及近义词反义词和造句大全 囫囵吞枣；【解释】：囫囵：整个儿。把枣整个咽下去，不加咀嚼，不辨味道。比喻对事物不加分析考虑。【近义词】：不求甚解【反义词】融会贯穿[造句];学习不能囫囵吞枣而是要精益求精 不求甚解；bùqiúshènjiě【解释】：甚：专门，极。只求明白个大概，不求完全了解。常指学习或研究不认真、不深入【近义词】：囫囵吞枣【反义词】：精益求精 造句；1；在学习上，我们要理解透彻，不能不求甚解 2；学习科学文化知识要刻苦钻研，深入领会，不能粗枝大叶，不求甚解。 千篇一律；【解释】：一千篇文章都一个样。指文章公式化。也比喻办事按一个格式，专门机械。 【近义词】：千人一面、如出一辙【反义词】：千差万别、形形色色 造句；学生旳作文千篇一律，专门少能有篇与众不同旳，这确实是平常旳练习太少了。 倾盆大雨；qīngpéndàyǔ【解释】：雨大得象盆里旳水直往下倒。形容雨大势急。 【近义词】：大雨如柱、大雨滂沱【反义词】：细雨霏霏牛毛细雨 造句；3月旳天说变就变，瞬间下了一场倾盆大雨。今天下了一场倾盆大雨。 坚决果断；áobùyóuyù：意思；做事果断，专门快拿定了主意，一点都不迟疑，形容态度坚决 近义词；不假思索斩钉截铁反义词；犹豫不决 造句；1看到小朋友落水，司马光坚决果断地搬起石头砸缸。2我坚决果断旳承诺了她旳要求。 饥肠辘辘jīchánglùlù【近义词】：饥不择食【反义词】：丰衣足食 造句；1我放学回家已是饥肠辘辘。2那个饥肠辘辘旳小孩差不多两天没吃饭了 滚瓜烂熟gǔnguālànshóu〔shú)【解释】：象从瓜蔓上掉下来旳瓜那样熟。形容读书或背书流利纯熟。【近义词】：倒背如流【反义词】：半生半熟造句；1、这篇课文我们早已背得滚瓜烂熟了 流光溢彩【liúguāngyìcǎi】解释；光影，满溢旳色彩，形容色彩明媚 造句：国庆节，商场里装饰旳流光溢彩。 津津有味；jīnjīnyǒuwèi解释：兴趣浓厚旳模样。指吃得专门有味道或谈得专门有兴趣。 【近义词】：兴致勃勃有滋有味【反义词】：索然无味、枯燥无味 造句；1今天旳晚餐真丰富，小明吃得津津有味。 天长日久；tiānchángrìjiǔ【解释】：时刻长，生活久。【近义词】：天长地久【反义词】：稍纵即逝 造句：小缺点假如不立即改掉, 天长日久就会变成坏适应 如醉如痴rúzuìrúchī【解释】：形容神态失常，失去自制。【近义词】：如梦如醉【反义词】：恍然大悟造句；这么美妙旳音乐，我听得如醉如痴。 浮想联翩【fúxiǎngliánpiān解释】：浮想：飘浮不定旳想象；联翩：鸟飞旳模样，比喻连续不断。指许许多多旳想象不断涌现出来。【近义词】：思绪万千 造句；1他旳话让人浮想联翩。2:这幅画饱含诗情，使人浮想联翩，神游画外，得到美旳享受。 悲欢离合bēihuānlíhé解释；欢乐、离散、聚会。泛指生活中经历旳各种境遇和由此产生旳各种心情【近义词】：酸甜苦辣、喜怒哀乐【反义词】：平淡无奇 造句；1人一辈子即是悲欢离合,总要笑口常开,我们旳生活才阳光明媚. 牵肠挂肚qiānchángguàdù【解释】：牵：拉。形容十分惦念，放心不下 造句；儿行千里母担忧，母亲总是那个为你牵肠挂肚旳人 如饥似渴rújīsìkě：形容要求专门迫切，仿佛饿了急着要吃饭，渴了急着要喝水一样。 造句；我如饥似渴地一口气读完这篇文章。他对知识旳如饥似渴旳态度造就了他今天旳成功。 不言而喻bùyánéryù【解释】：喻：了解，明白。不用说话就能明白。形容道理专门明显。 【近义词】：显而易见【反义词】：扑朔迷离造句；1珍惜时刻，好好学习，那个道理是不言而喻旳 与众不同；yǔzhòngbùtóng【解释】：跟大伙不一样。 〖近义词〗别出心裁〖反义词〗平淡无奇。造句； 1从他与众不同旳解题思路中，看出他专门聪慧。2他是个与众不同旳小孩
人教版(新目标)初中英语形容词与副词的比较级与最高级
人教版（新目标）初中英语形容词与副词的比较级与最高级 （一）规则变化： 1．绝大多数的单音节和少数双音节词，加词尾-er ，-est tall—taller—tallest 2．以不发音的e结尾的单音节词和少数以-le结尾的双音节词只加-r，-st nice—nicer—nicest , able—abler—ablest 3．以一个辅音字母结尾的重读闭音节词或少数双音节词，双写结尾的辅音字母，再加-er，-est big—bigger—biggest 4．以辅音字母加y结尾的双音节词，改y为i再加-er，-est easy—easier—easiest 5．少数以-er，-ow结尾的双音节词末尾加-er，-est clever—cleverer—cleverest, narrow—narrower—narrowest 6．其他双音节词和多音节词，在前面加more，most来构成比较级和最高级 easily—more easily—most easily （二）不规则变化 常见的有： good / well—better—best ; bad (ly)/ ill—worse—worst ; old—older/elder—oldest/eldest many / much—more—most ; little—less—least ; far—farther/further—farthest/furthest
用法： 1．原级比较：as + adj./adv. +as（否定为not so/as + adj./adv. +as）当as… as中间有名字时，采用as + adj. + a + n.或as + many / much + n. This is as good an example as the other is . I can carry as much paper as you can. 表示倍数的词或其他程度副词做修饰语时放在as的前面 This room is twice as big as that one. 倍数+as+adj.+as = 倍数+the +n.+of Your room is twice as larger as mine. = Your room is twice the size of mine. 2．比较级+ than 比较级前可加程度状语much, still, even, far, a lot, a little, three years. five times,20%等 He is three years older than I (am). 表示“（两个中）较……的那个”时，比较级前常加the（后面有名字时前面才能加冠词） He is the taller of the two brothers. / He is taller than his two brothers. Which is larger, Canada or Australia? / Which is the larger country, Canada or Australia? 可用比较级形式表示最高级概念，关键是要用或或否定词等把一事物（或人）与其他同类事物（或人）相分离 He is taller than any other boy / anybody else.
英语中的比较级和最高级
大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和 -est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音字母然后再加 -er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不 形容词比较级的用法: 形容词的比较级用于两个人或事物的比较,其结构形式如下: 主语+谓语(系动词)+ 形容词比较级+than+ 对比成分。也就是, 含有形容词比较级的主句+than+从句。注意从句常常省去意义上和主句相同的部分, 而只剩下对比的成分。
悲惨的近义词反义词和造句
悲惨的近义词反义词和造句 导读：悲惨的近义词 悲凉(注释:悲哀凄凉：～激越的琴声。) 悲惨的反义词 幸福(注释:个人由于理想的实现或接近而引起的一种内心满足。追求幸福是人们的普遍愿望，但剥削阶级把个人幸福看得高于一切，并把个人幸福建立在被剥削阶级的痛苦之上。无产阶级则把争取广大人民的幸福和实现全人类的解放看作最大的幸福。认为幸福不仅包括物质生活，也包括精神生活;个人幸福依赖集体幸福，集体幸福高于个人幸福;幸福不仅在于享受，而主要在于劳动和创造。) 悲惨造句 1.一个人要发现卓有成效的真理，需要千百个人在失败的探索和悲惨的错误中毁掉自己的生命。 2.贝多芬的童年尽管如是悲惨，他对这个时代和消磨这时代的地方，永远保持着一种温柔而凄凉的回忆。 3.卖火柴的小女孩在大年夜里冻死了，那情景十分悲惨。 4.他相信，他们每个人背后都有一个悲惨的故事。 5.在那次悲惨的经历之后，我深信自己绝对不是那种可以离家很远的人。 6.在人生的海洋上，最痛快的事是独断独航，但最悲惨的却是回头无岸。 7.人生是艰苦的。对不甘于平庸凡俗的人那是一场无日无夜的斗
争，往往是悲惨的、没有光华的、没有幸福的，在孤独与静寂中展开的斗争。……他们只能依靠自己，可是有时连最强的人都不免于在苦难中蹉跎。罗曼·罗兰 8.伟大的心胸，应该表现出这样的气概用笑脸来迎接悲惨的厄运，用百倍的勇气来应付开始的不幸。鲁迅人在逆境里比在在顺境里更能坚强不屈。遇厄运时比交好运时容易保全身心。 9.要抓紧时间赶快生活，因为一场莫名其妙的疾病，或者一个意外的悲惨事件，都会使生命中断。奥斯特洛夫斯基。 10.在我一生中最悲惨的一个时期，我曾经有过那类的想法：去年夏天在我回到这儿附近的地方时，这想法还缠着我;可是只有她自己的亲自说明才能使我再接受这可怕的想法。 11.他们说一个悲惨的故事是悲剧，但一千个这样的故事就只是一个统计了。 12.不要向诱惑屈服，而浪费时间去阅读别人悲惨的详细新闻。 13.那起悲惨的事件深深地铭刻在我的记忆中。 14.伟大的心胸，应该用笑脸来迎接悲惨的厄运，用百倍的勇气来应付一切的不幸。 15.一个人要发现卓有成效的真理，需要千百万个人在失败的探索和悲惨的错误中毁掉自己的生命。门捷列夫 16.生活需要爱，没有爱，那些受灾的人们生活将永远悲惨;生活需要爱，爱就像调味料，使生活这道菜充满滋味;生活需要爱，爱让生活永远充满光明。
英语比较级和最高级的用法归纳
英语比较级和最高级的用法归纳 在学习英语过程中，会遇到很多的语法问题，比如比较级和最高级的用法，对于 这些语法你能够掌握吗？下面是小编整理的英语比较级和最高级的用法，欢迎阅读！ 英语比较级和最高级的用法 一、形容词、副词的比较级和最高级的构成规则 1.一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级 在后面加-est; (1)单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest (2)双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2.以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st; 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3.在重读闭音节(即：辅音+元音+辅音)中，先双写末尾的辅音字母，比较级加-er，最高级加-est; 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4.以“辅音字母+y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est; 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5.其他双音节词和多音节词，比较级在前面加more，最高级在前面加most; 如：bea utiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily 注意：(1)形容词最高级前通常必须用定冠词 the，副词最高级前可不用。 例句： The Sahara is the biggest desert in the world. (2) 形容词most前面没有the，不表示最高级的含义，只表示"非常"。 It is a most important problem. =It is a very important problem.
英语比较级和最高级的用法
More than的用法 A. “More than+名词”表示“不仅仅是” 1)Modern science is more than a large amount of information. 2)Jason is more than a lecturer; he is a writer, too. 3) We need more than material wealth to build our country.建设我们国家，不仅仅需要物质财富. B. “More than+数词”含“以上”或“不止”之意，如： 4)I have known David for more than 20 years. 5)Let's carry out the test with more than the sample copy. 6) More than one person has made this suggestion. 不止一人提过这个建议. C. “More than+形容词”等于“很”或“非常”的意思，如： 7)In doing scientific experiments, one must be more than careful with the instruments. 8)I assure you I am more than glad to help you. D. more than + (that)从句，其基本意义是“超过（=over）”，但可译成“简直不”“远非”.难以，完全不能（其后通常连用情态动词can） 9) That is more than I can understand . 那非我所能懂的. 10) That is more than I can tell. 那事我实在不明白。 11) The heat there was more than he could stand. 那儿的炎热程度是他所不能忍受的 此外，“more than”也在一些惯用语中出现，如： more...than 的用法 1. 比……多，比……更 He has more books than me. 他的书比我多。 He is more careful than the others. 他比其他人更仔细。 2. 与其……不如 He is more lucky than clever. 与其说他聪明，不如说他幸运。 He is more （a）scholar than （a）teacher. 与其说他是位教师，不如说他是位学者。 注：该句型主要用于同一个人或物在两个不同性质或特征等方面的比较，其中的比较级必须用加more 的形式，不能用加词尾-er 的形式。 No more than/not more than 1. no more than 的意思是“仅仅”“只有”“最多不超过”，强调少。如： --This test takes no more than thirty minutes. 这个测验只要30分钟。 --The pub was no more than half full. 该酒吧的上座率最多不超过五成。-For thirty years，he had done no more than he （had）needed to. 30年来，他只干了他需要干的工作。 2. not more than 为more than （多于）的否定式，其意为“不多于”“不超过”。如：Not more than 10 guests came to her birthday party. 来参加她的生日宴会的客人不超过十人。 比较： She has no more than three hats. 她只有3顶帽子。（太少了） She has not more than three hats. 她至多有3顶帽子。（也许不到3顶帽子） I have no more than five yuan in my pocket. 我口袋里的钱最多不过5元。（言其少） I have not more than five yuan in my pocket. 我口袋里的钱不多于5元。（也许不到5元） more than, less than 的用法 1. （指数量）不到，不足 It’s less than half an hour’s drive from here. 开车到那里不到半个钟头。 In less than an hour he finished the work. 没要上一个小时，他就完成了工作。 2. 比……（小）少 She eats less than she should. 她吃得比她应该吃的少。 Half the group felt they spent less than average. 半数人觉得他们的花费低于平均水平。 more…than,/no more than/not more than (1)Mr．Li is ________ a professor; he is also a famous scientist． (2)As I had ________ five dollars with me, I couldn’t afford the new jacket then． (3)He had to work at the age of ________ twelve． (4)There were ________ ten chairs in the room．However, the number of the children is twelve． (5)If you tel l your father what you’ve done, he’ll be ________ angry． (6)－What did you think of this novel? －I was disappointed to find it ________ interesting ________ that one． 倍数表达法 1. “倍数+形容词（或副词）的比较级+than+从句”表示“A比B大（长、高、宽等）多少倍” This rope is twice longer than that one.这根绳是那根绳的三倍（比那根绳长两倍）。The car runs twice faster than that truck.这辆小车的速度比那辆卡车快两倍（是那辆卡车的三倍）。 2. “倍数+as+形容词或副词的原级+as+从句”表示“A正好是B的多少倍”。
初中英语比较级和最高级讲解与练习
初中英语比较级和最高级讲解与练习 形容词比较级和最高级 一．绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 1. 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 2. 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基 础上变化的。分为规则变化和不规则变化。 二．形容词比较级和最高级规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加-er 和-est 构成。 great (原级) greater(比较级) greatest(最高级) 2) 以-e 结尾的单音节形容词的比较级和最高级是在词尾加-r 和-st 构成。 wide (原级) wider (比较级) widest (最高级) 3) 少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和-est构成。 clever(原级) cleverer(比较级) cleverest(最高级)， slow(原级) slower(比较级) slowest (最高级) 4) 以-y 结尾,但-y 前是辅音字母的形容词的比较级和最高级是把-y 去掉,加上-ier 和-est 构成. happy (原形) happier (比较级) happiest (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该 辅音字母然后再加-er和-est。 原形比较级最高级原形比较级最高级 big bigger biggest hot hotter hottest red redder reddest thin thinner thinnest 6) 双音节和多音节形容词的比较级和最高级需用more 和most 加在形容词前面来构 成。 原形比较级最高级 careful careful more careful most careful difficult more difficult most difficult delicious more delicious most delicious 7)常用的不规则变化的形容词的比较级和最高级: 原级比较级最高级 good better best 好的 well better best 身体好的 bad worse worst 坏的 ill worse worst 病的 many more most 许多 much more most 许多 few less least 少数几个 little less least 少数一点儿 （little littler littlest 小的） far further furthest 远（指更进一步，深度。亦可指更远） far farther farthest 远（指更远，路程）
知己的近义词反义词及知己的造句
知己的近义词反义词及知己的造句 本文是关于知己的近义词反义词及知己的造句，感谢您的阅读！ 知己的近义词反义词及知己的造句知己 基本解释：顾名思义是了解、理解、赏识自己的人，如"知己知彼，百战不殆";更常指懂你自己的挚友或密友，它是一生难求的朋友，友情的最高境界。正所谓:"士为知己者死"。 1.谓了解、理解、赏识、懂自己。 2.彼此相知而情谊深切的人。 【知己近义词】 亲信，好友，密友，心腹，挚友，深交，相知，知交，知友，知心，知音，石友，老友，至友 【知己反义词】 仇人敌人陌路 【知己造句】 1、我们想要被人爱、想拥有知己、想历经欢乐、想要安全感。 2、朋友本应是我们的亲密知己和支持者，但对于大多数人来说，有一些朋友比起帮助我们，更多的却是阻碍。 3、那么，为什么你就认为，随着年龄的增长，比起女人来男人们的知己和丰富的人际关系更少，因此一般容易更孤独呢？ 4、他成了我的朋友、我的知己、我的顾问。 5、无论在我当州长还是总统的时候，布鲁斯都是我的密友、顾问和知己。他这样的朋友人人需要，也是所有总统必须拥有的。
6、波兰斯基有着一段声名卓著的电影生涯，也是几乎所有电影界重要人物们的挚友和同事，他们是知己，是亲密的伙伴。 7、搜索引擎变成了可以帮追我们的忏悔室，知己，信得过的朋友。 8、这样看来，奥巴马国家安全团队中最具影响力的当属盖茨了――但他却是共和党人，他不会就五角大楼以外问题发表看法或成为总统知己。 9、我们的关系在二十年前就已经和平的结束了，但在网上，我又一次成为了他精神层面上的评论家，拉拉队，以及红颜知己。 10、这位“知己”，作为拍摄者，站在距离电视屏幕几英尺的地方对比着自己年轻版的形象。 11、父亲与儿子相互被形容为对方的政治扩音筒、知己和后援。 12、这对夫妻几乎没有什么至交或知己依然在世，而他们在后纳粹时期的德国也不可能会说出实话的。 13、她把我当作知己，于是，我便将她和情人之间的争吵了解得一清二楚。 14、有一种友谊不低于爱情；关系不属于暖昧；倾诉一直推心置腹；结局总是难成眷属；这就是知己！ 15、把你的治疗师当做是可以分享一切心事的知己。 16、莉莉安对我敞开心胸，我成了她的知己。 17、据盖洛普民意调查显示，在那些自我认同的保守党人中，尽管布什仍维持72%支持率，但他在共和党领导层中似乎很少有几位知
英语比较级和最高级
形容词比较级和最高级的形式 一、形容词比较级和最高级的构成 形容词的比较级和最高级变化形式规则如下 构成法原级比较级最高级 ①一般单音节词末尾加 er 和 est strong stronger strongest ②单音节词如果以 e结尾，只加 r 和 st strange stranger strangest ③闭音节单音节词如末尾只有一个辅音字母， 须先双写这个辅音字母，再加 er和 est sad big hot sadder bigger hotter saddest biggest hottest ④少数以 y, er(或 ure), ow, ble结尾的双音节词， 末尾加 er和 est(以 y结尾的词，如 y前是辅音字母， 把y变成i，再加 er和 est，以 e结尾的词仍 只加 r和 st) angry Clever Narrow Noble angrier Cleverer narrower nobler angriest cleverest narrowest noblest ⑤其他双音节和多音节词都在前面加单词more和most different more different most different 1) The most high 〔A〕mountain in 〔B〕the world is Mount Everest，which is situated 〔C〕in Nepal and is twenty nine thousand one hundred and fourty one feet high 〔D〕 . 2) This house is spaciouser 〔A〕than that 〔B〕white 〔C〕one I bought in Rapid City，South Dakota 〔D〕last year. 3) Research in the social 〔A〕sciences often proves difficulter 〔B〕than similar 〔C〕work in the physical 〔D〕sciences. 二、形容词比较级或最高级的特殊形式：
高中英语的比较级和最高级用法总结
比较级和最高级 1.在形容词词尾加上―er‖ ―est‖ 构成比较级、最高级： bright（明亮的）—brighter—brightest broad（广阔的）—broader—broadest cheap（便宜的）—cheaper—cheapest clean（干净的）—cleaner—cleanest clever（聪明的）—cleverer—cleverest cold（寒冷的）—colder—coldest cool（凉的）—cooler—coolest dark（黑暗的）—darker—darkest dear（贵的）—dearer—dearest deep（深的）—deeper—deepest fast（迅速的）—faster—fastest few（少的）—fewer—fewest great（伟大的）—greater—greatest hard（困难的,硬的）—harder—hardest high（高的）—higher—highest kind（善良的）—kinder—kindest light（轻的）—lighter—lightest long（长的）—longer—longest loud（响亮的）—louder—loudest low（低的）—lower—lowest near（近的）—nearer—nearest new（新的）—newer—newest poor（穷的）—poorer—poorest quick（快的）—quicker—quickest quiet（安静的）—quieter—quietest rich（富裕的）—richer—richest short（短的）—shorter—shortest slow（慢的）—slower—slowest small（小的）—smaller—smallest smart（聪明的）—smarter—smartest soft（柔软的）—softer—softest strong（强壮的）—stronger—strongest sweet（甜的）—sweeter—sweetest tall（高的）-taller-tallest thick（厚的）—thicker—thickest warm（温暖的）—warmer—warmest weak（弱的）—weaker—weakest young（年轻的）—younger—youngest 2.双写最后一个字母,再加上―er‖ ―est‖构成比较级、最高级： big（大的）—bigger—biggest fat（胖的）—fatter—fattest hot（热的）—hotter—hottest red（红的）—redder—reddest sad（伤心的）—sadder—saddest thin（瘦的）—thinner—thinnest wet（湿的）—wetter—wettest mad（疯的）—madder—maddest 3.以不发音的字母e结尾的形容词,加上―r‖ ―st‖ 构成比较级、最高级：able（能干的）—abler—ablest brave（勇敢的）—braver—bravest close（接近的）—closer—closest fine（好的,完美的）—finer—finest large（巨大的）—larger—largest late（迟的）—later—latest nice（好的）—nicer—nicest ripe（成熟的）—riper—ripest
小学语文反义词仿照的近义词反义词和造句
仿照的近义词反义词和造句 仿照的近义词 【仿制解释】：仿造：～品 【模仿解释】：个体自觉或不自觉地重复他人的行为的过程。是社会学习的重要形式之一。尤其在儿童方面，儿童的动作、语言、技能以及行为习惯、品质等的形成和发展都离不开模仿。可分为无意识模仿和有意识模仿、外部模仿和内部模仿等多种类型。 仿照的反义词 【独创解释】：独特的创造：～精神ㄧ～一格。 仿照造句 一、老师让我们仿照黑板上的图画一幅画。 二、仿照下面的句式，以“只有”开头，写一结构与之相似的复句。 三、仿照例句的句子，在下面两句的横线上补写相应的内容。 四、仿照例句，以“记忆”或“友情”开头，另写一句话。 五、仿照下面两个例句，用恰当的词语完成句子，要求前后语意关联。 六、仿照开头两句句式，通过联想，在后面两句横线上填上相应的词语。 七、仿照所给例句，用下面的词展开联想，给它一个精彩的解释。 八、仿照例句，以“你”开头，另写一个句子。 九、仿照下列句式，续写两个句子，使之与前文组成意义相关的.句子。 十、我们也仿照八股文章的笔法来一个“八股”,以毒攻毒,就叫做八大罪状吧。
十一、仿照例句，任选一种事物，写一个句子。 十二、仿照下面一句话的句式和修辞，以“时间”开头，接着写一个句子。 十三、仿照例句，以“热爱”开头，另写一句子。 十四、仿照下面的比喻形式，另写一组句子。要求选择新的本体和喻体，意思完整。 十五、根据语镜，仿照划线句子，接写两句，构成语意连贯的一段话。 十六、仿照下面句式，续写两个句式相同的比喻句。 十七、自选话题，仿照下面句子的形式和修辞，写一组排比句。 十八、仿照下面一句话的句式，仍以“人生”开头，接着写一句话。 十九、仿照例句的格式和修辞特点续写两个句子，使之与例句构成一组排比句。 二十、仿照例句，另写一个句子，要求能恰当地表达自己的愿望。 二十一、仿照下面一句话的句式，接着写一句话，使之与前面的内容、句式相对应，修辞方法相同。 二十二、仿照下面一句话的句式和修辞，以“思考”开头，接着写一个句子。 二十三、仿照下面例句，从ABCD四个英文字母中选取一个，以”青春”为话题，展开想象和联想，写一段运用了比喻修辞格、意蕴丰富的话，要求不少于30字。 二十四、仿照下面例句，另写一个句子。 二十五、仿照例句，另写一个句子。 二十六、下面是毕业前夕的班会上，数学老师为同学们写的一句赠言，请你仿照它的特点，以语文老师的身份为同学们也写一句。
(完整版)初中英语比较级和最高级的用法
英语语法---比较级和最高级的用法 在英语中通常用下列方式表示的词:在形容词或副词前加more(如 more natural,more clearly )或加后缀 -er(newer,sooner )。典型的是指形容词或副词所表示的质、量或关系的增加。英语句子中，将比较两个主体的方法叫做“比较句型”。其中，像“A比B更……”的表达方式称为比较级；而“A最……”的表达方式则称为最高级。组成句子的方式是将形容词或副词变化成比较级或最高级的形态。 一、形容词、副词的比较级和最高级的构成规则 1．一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est； （1）单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest （2）双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2．以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st； 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3．在重读闭音节（即：辅音＋元音＋辅音）中，先双写末尾的辅音字母，比较级加-er，最高级加-est； 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4．以“辅音字母＋y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est； 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5．其他双音节词和多音节词，比较级在前面加more，最高级在前面加most； 如：beautiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily
暗示的近义词和反义词 [暗示的近义词反义词和造句]
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初中英语形容词比较级和最高级讲解与练习
初中英语形容词比较级和最高级讲解与练习 形容词比较级和最高级 绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。 例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。 wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加-er 和-est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音 字母然后再加-er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不"