2014-11-場(chǎng)誘導(dǎo)化學(xué)反應(yīng)

1、,,場(chǎng)誘導(dǎo)化學(xué)合成與制備材料Materials Induce-synthesized & Prepared by Fields,管自生,南京工業(yè)大學(xué)材料科學(xué)與工程學(xué)院,,,包括：1）尋找新合成與制備方法的科學(xué)問(wèn)題New Strategy；2）以適當(dāng)?shù)臄?shù)量和形態(tài)合成材料的技術(shù)問(wèn)題；3）已有材料的新合成方法（如Sol-gel）及其新形態(tài)（如Fiber、Film、Hierarchical Structures）的合成。,合成與制備(

2、synthesize & Prepare),合成： 指促使原子、分子結(jié)合而構(gòu)成材料的化學(xué)與物理過(guò)程。制備:研究如何控制原子與分子使之構(gòu)成有用的材料。,場(chǎng)：包括磁場(chǎng)；電場(chǎng)；微波；等離子體；光；聲場(chǎng)；重力場(chǎng)包括加熱等；為材料的合成與制備針對(duì)反應(yīng)提供反應(yīng)能量或者提高反應(yīng)速度或者改變反應(yīng)途徑等,,,5.電場(chǎng)合成 靜電合成-靜紡Electric-field induced Synthesize &Electrospinning

3、,主要內(nèi)容(Main contents)：,1.光誘導(dǎo)合成 Light-induced Synthesize & Prepare,2. 微波等離子合成 Microwave & Plasma,3. 聲波合成 Acoustic wave Synthesize,4. 重力場(chǎng)(Gravity field)在材料合成中的應(yīng)用,,,Electromagnetic spectra,1. Introduction Lights,,,電磁

4、波的范圍,,,,分子光譜,,Molecular Spectra,,,2. 光與物質(zhì)作用理論基礎(chǔ)Theories of Light-excited Materials,2.1原子分子受光激發(fā) Excited Atom & Molecules 原子分子軌道；電子躍遷與輻射；分子能級(jí)圖；原子分子受光激發(fā)后變化過(guò)程 2.2半導(dǎo)體受激光激發(fā)Excited Semicondutors半導(dǎo)體躍遷；半導(dǎo)體受光激發(fā)的變化過(guò)程2.3

5、 金屬受激光激發(fā) Excited Metals,,,,,,,,,Figure Excitation and deexcitation process in molecule,Absorption~ 10-15 s,S0,S2,Internal conversion10-14-10-13 s,S1,T1,Fluorescence10-9-10-5,,,Internal and External radiationless con

6、version,Intersystem crossing 10-6 s,Chemical reaction,Singlet excited state,Triplet excited state,Electron transfer（ms),Phosphorescence10-5-10-3,Ground state,2.1原子分子受光激發(fā),,,當(dāng)基態(tài)分子的一個(gè)成對(duì)電子吸收光輻射后，被激發(fā)躍遷到能較高的軌道上，通常它的自旋方向spinni

7、ng direction不改變，即?S=0，則激發(fā)態(tài)仍是單線態(tài)，即“單線(重)激發(fā)態(tài)”；    如果電子在躍遷過(guò)程中，還伴隨著自旋方向的改變，這時(shí)便具有兩個(gè)自旋不配對(duì)的電子，電子凈自旋不等于零，而等于1： S=1/2+1/2=1 其多重性： M=2S+1=3    即分子在磁場(chǎng)中受到影響而產(chǎn)生能級(jí)分裂，這種受激態(tài)稱(chēng)為“三線(重)激發(fā)態(tài)”；,,,原子核外電子受不同能量光子激發(fā)

8、后，輻射過(guò)程,,,1)平動(dòng)-平動(dòng)轉(zhuǎn)移 Translation-Translation2)平動(dòng)-轉(zhuǎn)動(dòng)轉(zhuǎn)移 Translation-Rotation3)轉(zhuǎn)動(dòng)-轉(zhuǎn)動(dòng)轉(zhuǎn)移 Rotation-Vibration4)振動(dòng)-平動(dòng)轉(zhuǎn)動(dòng)轉(zhuǎn)移Vibration-Translation5) 振動(dòng)-振動(dòng)轉(zhuǎn)移 Vibration-Vibration6)電子-振動(dòng)轉(zhuǎn)移 Electron-Vibration7)電子-電子轉(zhuǎn)移Electron-Electr

9、on,能量轉(zhuǎn)移 Energy Transfer ：,Molecule orbits & Energy Levels 分子軌道與能級(jí),2.1原子分子受光激發(fā),,,Illumination of Electron Levels、 Vabriation Levels、 Rotation Levels,Electron Levels,Vabriation Levels,Rotation Levels,

10、2.1原子分子受光激發(fā),,,量子力學(xué)理論，分子的振 – 轉(zhuǎn)躍遷也是量子化的或者說(shuō)將產(chǎn)生非連續(xù)譜。因此，分子的能量變化 ΔE 為各種形式能量變化的總和：,運(yùn)動(dòng)的分子外層電子Outlayer Electrons - 吸收外來(lái)輻射 - 產(chǎn)生電子能級(jí)躍遷 – 分子吸收譜Molecular absorption spectra。,其中?Ee 最大： 1-20 eV; ?Ev 次之： 0.05-1 eV; ?Er 最?。?<0.05 eV

11、,2.1原子分子受光激發(fā),,,光源簡(jiǎn)介:普通光源;激光光源,太陽(yáng)光模擬光源,,,,鹵素?zé)?,,氙燈,紫外燈高壓汞燈,,,(一)光誘導(dǎo)合成法 Light-induced Synthesize,5. 其它光與材料合成,4.激光與材料化學(xué)合成,2. 光與物質(zhì)作用理論基礎(chǔ) Principles,1.光與激光laser簡(jiǎn)介,3. 激光誘導(dǎo)化學(xué)反應(yīng)Laser-induced Chemical Reactions,,,1.激光簡(jiǎn)介Introd

12、uction of Laser,近幾十年來(lái)，隨著激光技術(shù)的應(yīng)用與發(fā)展，出現(xiàn)了一門(mén)嶄新的邊緣學(xué)科——激光化學(xué)Laser chemistry 。 它和經(jīng)典的光化學(xué)反應(yīng)(Photochemistry )一樣，是研究在光子Photon與物質(zhì)相互作剛的過(guò)程中，物質(zhì)激發(fā)態(tài)Exited States 的產(chǎn)生、結(jié)構(gòu)、性能及其相互轉(zhuǎn)化的一門(mén)學(xué)科。,,,特點(diǎn): 1)具有亮度高、單色性好homochromatism、方向性好 Orien

13、tation ;2) 高亮度，可以成為一種特殊熱源; 利用這種熱源:直接加熱Heating蒸發(fā)Evaporation解離Ionization 化學(xué)物質(zhì)使許多繁雜、艱難的化學(xué)操作變得簡(jiǎn)單可行；3) 激光對(duì)原子、分子選擇性相互作用Selective Reactions 提供了必要條件；4)利用激光的方向性，可實(shí)現(xiàn)微區(qū)域Microarea的高溫化學(xué)反應(yīng)High-temperature Reactions。,,,激

14、光器類(lèi)型,1 CO2激光器 Carbon Dioxide Laser2 He-Ne激光器 Helium-neon3氬激光器:Argon laser4 準(zhǔn)分子激光器 excimer laser5 固體激光器:釹激光器:neodymium laser/Nd laser6 自由電子激光器 Free Electron Laser,,,CO2 Laser,屬于氣體激光器，分子激光器molecular laserWavelength

15、 9-11?m，最常見(jiàn)10.6 ?m效率高 High efficiency光束質(zhì)量好 High Quality功率范圍大 （幾瓦～幾兆瓦）運(yùn)行方式多樣結(jié)構(gòu)多樣,,,,He-Ne Laser,氣體原子激光器 Gas Atomic LaserOutput 輸出譜線Spectrum line ：632.8nm，1.15 ?m，3.39 ?m，以632.8 nm為最常見(jiàn) 功率在mW級(jí)，最大1W光束質(zhì)量好，發(fā)散角可小于1mrad

16、單色性好Homochromatism ，帶寬Bandwidth可小于20HzHigh stability,,,準(zhǔn)分子激光器Excimer laser,準(zhǔn)分子指在激發(fā)態(tài)能夠暫時(shí)結(jié)合成的不穩(wěn)定分子高重復(fù)率 可調(diào)諧 量子效率高、波長(zhǎng)短，紫外到可見(jiàn)區(qū),主要的準(zhǔn)分子激光器,Excimer laser是一種紫外線化學(xué)激光器Ultraviolet Chemical Laser，常用于眼科手術(shù)及半導(dǎo)體工藝上。,,,YAG Solid Laser

17、Yttrium Aluminum Garnet石榴石,Nd: YAG固體脈沖激光器主要性能指標(biāo)：Wavelength：213、266、355、532、1064 nm Repeat Frequency：1-50 Hz（可調(diào)） Energy：連續(xù)可調(diào)，Max 300 mJ （瞬間可融化、氣 化多種材料及其表面） 脈寬Pulse width：3-5 ns,Energy Levels,(1) Changes of Atoms o

18、r Molecules Excited by Laser,Coulomb explosion 庫(kù)侖裂解Relativistic regime 相對(duì)論區(qū)間,Timescales of various electron and lattice processes in laser-excited solids. Each green bar represents an approximate range of characteristi

19、c times over a range of carrier densities from1017 to 1022cm–3.The triangles at the top show the current state-of the-art in the generation of short pulses of electromagnetic radiation: 1. 5 fs, 2. 120 fs (X-ray), 3. 0.5

20、 fs (far ultraviolet).,Time Scales,碰撞電離,Figure Electron and lattice excitation and relaxation processes in a laser-excited direct gap semiconductor. CB is the conduction band and VB the valence band. d, Carrier distribut

21、ion before scattering. e, Carrier–carrier scattering. f, Carrier–phonon scattering. g, Radiative recombination. h,Auger recombination. i, Diffusion of excited carriers.j,Thermal diffusion. k,Ablation. l, Resolidification

22、 or condensation.,a, Multiphoton absorption.b, Free-carrier absorption. c, Impact ionization.,,,中國(guó)“低空衛(wèi)士”激光系統(tǒng),,,,鋁背鈍化的太陽(yáng)能電池,,,3.2,,用各種波長(zhǎng)激光（紅外、可見(jiàn)、紫外）誘發(fā)的化學(xué)反應(yīng)大約有幾百種。根據(jù)波長(zhǎng)的不同，激光誘發(fā)化學(xué)反應(yīng)的機(jī)理也不相同: 例如：紅外激光Infrared Laser誘導(dǎo)化學(xué)反應(yīng):

23、 紅外敏化反應(yīng)Infrared sensitized Reactions; 振動(dòng)異構(gòu)化反應(yīng)Isomerization reaction; 紅外異相催化反應(yīng)Heterocatalysis; 紅外誘導(dǎo)鏈反應(yīng)Chain reaction; 紅外光解范德華分子反應(yīng)Photolysis Van der Waals Molecules; 紅外多光子離解反應(yīng)Multiphoton dissociation; 紅外多光子離解反應(yīng)要求激光

24、必須有足夠高的強(qiáng)度（至少108瓦/平方厘米）。,3. 激光如何誘導(dǎo)化學(xué)反應(yīng),1). 激光誘導(dǎo)化學(xué)反應(yīng)是指在常溫常壓下不能進(jìn)行但在激光的照射下可被誘發(fā)的化學(xué)反應(yīng)。激光具有單色性、高強(qiáng)度和短脈寬等優(yōu)越性能，是誘發(fā)光化學(xué)反應(yīng)最理想的光源。,2) 激光誘導(dǎo)化學(xué)反應(yīng)主要是指激光光解反應(yīng)Laser-induced Photolysis以及由光解碎片splinter引起的后續(xù)化學(xué)反應(yīng)，例如，自由基Free radical或原子Atom，所產(chǎn)生的自由

25、基又可以誘發(fā)鏈鎖反應(yīng)Chain reaction。,,,紅外激光誘導(dǎo)化學(xué)反應(yīng)中，激光的作用不是簡(jiǎn)單的熱作用，而是紅外光子同分子內(nèi)的特定鍵或振動(dòng)膜之間發(fā)生共振耦合。 紅外激光誘導(dǎo)化學(xué)反應(yīng)是一種定向的Orientation、低反應(yīng)活化能Low activation energy的快速過(guò)程，具有高度的選擇性Selectivity。以三氯化硼分子為例，該分子的反對(duì)稱(chēng)伸縮振動(dòng)v3(955cm-1) 。當(dāng)用低功率的二氧化碳紅外激光（λ＝10.

26、55微米)輻照含有BCl3分子的混合氣體時(shí)，將誘發(fā)化學(xué)反應(yīng)。如混合氣體為BCl3＋H2S，常溫常壓下不發(fā)生反應(yīng)。在激光輻照時(shí)，使B-Cl鍵被激發(fā)，并發(fā)生以下反應(yīng)過(guò)程：,,3BCl2SH→（BClS）3＋3HCl   （BClS）3→B2S3＋BCl3,,,反應(yīng)物分子被激發(fā)至電子激發(fā)態(tài)excited electronic state絕大多數(shù)分子的離解能Dissociation energy在60～752.

27、4 kJ.mol-1或3～7eV之間，這就需要波長(zhǎng)為400～140 nm的紫外光輻照才行。原則上講，只要選擇合適波長(zhǎng)的激光，任何分子都能被光解，對(duì)同一分子來(lái)說(shuō)，不同波長(zhǎng)的激光輻照時(shí)有可能按不同的方式光解。例如，激光法生產(chǎn)氯乙烯（C2H3Cl）：,C2H4Cl·＋Cl·,C2H3Cl＋Cl·這是一個(gè)紫外激光誘導(dǎo)的自由基鏈反應(yīng)radical chain reaction，關(guān)鍵是二氯乙烷被準(zhǔn)分子激光光解所引發(fā)。

28、激光誘導(dǎo)化學(xué)反應(yīng)已用于10余種同位素的分離。,C2H4Cl2,,hv,C2H4Cl2＋Cl·→C2H3Cl2·＋HCl C2H3Cl2· → C2H3Cl＋Cl·,紫外或可見(jiàn)激光光解反應(yīng)Ultraviolet & Visible Laser-induced Reactions,,,,,光電離 Photoionization,1）光直接電離 Directly Photoion

29、ization分子電子直接被激發(fā)出2) 自電電離分子被激發(fā)到高于電離能的超激發(fā)態(tài)superexcited states，然后被微擾Disturbance電離一個(gè)離子ion和電子electron的狀態(tài),,,4.激光與材料制備Materials of Laser-induced Synthesise,4.1激光催化化學(xué)反應(yīng) Laser-induced Catalytic Chemical Reactions4.2激光誘導(dǎo)化學(xué)反應(yīng)

30、Laser-induced Chemical Reactions4.3激光選擇化學(xué)反應(yīng)Laser-induced Selective ChemicalReactions 4.4激光顯微化學(xué)反應(yīng) Laser-induced Microarea Chemical Reactions4.5激光合成陶瓷粉體 Ceramic Powder of Laser-induced Synthesis 4.6 脈沖激光沉積鍍膜

31、 Pulse Laser-induced Deposition Films4.7其它高能射線High Energy Rays在材料合成中的應(yīng)用,1. Laser-induced Catalytic Chemical Reactions,激光催化加快化學(xué)反應(yīng)速度表1列舉了一些激光催化反應(yīng)的效果。,,,4.2 Laser-induced Chemical Reactions,,,,,,,,,,,,光解制備氧化物半導(dǎo)體,Fast Sy

32、nthesis of ZnO Nanostructures byLaser-Induced Decomposition of Zinc Acetylacetonate,Presenting very attractive engineering properties like large exciton binding energy, photoluminescence, and piezoelectricity while bein

33、g easily synthesizable in a plenty of different morphologies in single-crystal form, nanostructured zinc oxide has become one of the most studied semiconductor nanomaterials of the beginning of the 21st century.,Because

34、of their great potential for the fabrication of new devices, in particular for optoelectronic and gassensing applications, 1D ZnO nanostructures have attracted much attention，oriented ZnO microtube arrays have been grown

35、 by solution chemistry for bio-/gas sensors by the selective UV light response.,Figure . Schematic depiction of the synthesis process. (A) Laser-induced decomposition of precursor solution. (B) Detail of the reaction zon

36、e with the different nanostructures obtained.,Solution Preparation. A quantity of 0.4 g of zinc acetylacetonate hydrate [æsiti'læsit?u,neit]乙酰丙酮 (Zn(C5H7O2)2?H2O, >95% purity) was manually mixed with

37、2 mL of deionized water and 2 mL of denatured ethanol (EtOH 85.47%, MeOH 13.68%, EtOAc 0.85%) for 5 min, forming a slurry of 0.355 M of Zn(AcAc)2?H2O. The pH of the solution was measured to be 8.25. A few drops of the

38、 solution was then transferred to a fused quartz substrate,Laser Decomposition. A CO2 laser ?=10.6 ?m,,Figure (A) Low-magnification view of deposit grown at 20 W, 2 s; (B) nanoparticle film; (C) nanowires; (D) nanoro

39、ds grown at the same parameters.,Only a few seconds of irradiation, various zinc oxide (ZnO) nanostructures including nanorods and nanowires are formed near the center of the irradiated zone, surrounded by a porous thin

40、film of ZnO nanoparticles,indeterminate shape with a very rough surface in the center.,nanoparticle aggregates,Ridges: nanowires nanorods,Different Zone,,,Figure . Influence of laser power on deposit morphology at a cons

41、tant irradiation time of 10 s: (A) 5 W, 40 W/cm2; (B) 10 W, 80 W/cm2; (C) 15 W, 119 W/cm2; (D) 20 W, 159 W/cm2.,The type of structures produced and their localization on the substrate can be varied by selecting adequate

42、irradiation time and laser power ranges.,crystalline whiskersan average length: 1.3um an average width of 167 nm,more randomly grown ZnO whiskers can be seen,,,Figure . SEM images of nanowires and nanonails grown with

43、different laser irradiation parameters: (A and B) 20 W, 5 s; (C and D) 20 W, 2 s.,The type of structures produced and their localization on the substrate can be varied by selecting adequate irradiation time and laser pow

44、er ranges.,UV lasing has been observed from ZnO whiskers and gas-sensing devices, and UV photodiodes were made from multipod-shaped nanorods.,Nanowires: 4.4 um further away from the center of the reaction zone,width of 4

45、7 nm,Nanoplates and nanonails with hexagonal tips between 100 and 300 nm wide,an assortment ofnanowire,,,Laser-Induced Mutual Transposition of the Core and the Shell of a Au@Pt Nanosphere,Noble-metal clusters and colloi

46、ds with nanometer dimensions, exhibiting new optical and physical properties, have attracted a great deal of interest.,光誘導(dǎo)制備納米晶金屬,The design and controlled fabrication of nanostructured materials with functional properti

47、es have been extensively studied recently.,Nanostructured metals attract considerable attention scientifically as well as industrially because they can be used in diverse applications such as catalysts, magnetic devices,

48、 single electron transistors, and optoelectronics.,,,Figure. Illustration of processes taking place in a platinum-topped gold nanosphere during irradiation with 1064-nm laser pulses of 30 ps. The black indicates gold, wh

49、ile the gray indicates platinum. 1)The thermalized photon energy of platinum-plasmon resonances melts small platinum nanoparticles surrounding the core gold to convert the topped nanosphere into a smooth Au@Pt core-shell

50、 nanosphere. 2)Gold having the lower melting point melts and soaks out to the surface with further irradiation to produce a reversed core/shell Pt@Au core-shell nanosphere.,The optical properties of platinum, palladium,

51、silver, and gold colloidal nanoparticles have received considerable attention because of this plasmon band.,Figure . TEM (A) and HRTEM images (B) of platinum-topped gold nanoparticles before (left) and after irradiation

52、(right) with 1064-nm laser pulses of 30 ps for 120 min. Note that the actual particles transformed into the particles of the right are different from those of the left.,1) Aqueous 15-nm gold colloids of 50 mL having sur

53、factant-free gold nanospheres a gold atomic concentration of 1.0 mM were prepared by the citrate檸檬酸 reduction of HAuCl4。 2) platinum-topped gold nanoparticles were prepared by adding 21 mL of a 10 mM 2-day-aged

54、H2PtCl6 aqueous solution and 8 mL of a 100 mL-ascorbic acid抗壞血酸 aqueous solution to 30 mL of the above-prepared gold colloids under vigorous stirring.,Experimental Sections,Citratic Acid,ascorbic acid,2-nm Pt,,,Figure 1.

55、 (A) Pictures of dried film 1 20, 40, and 60 min after the 355 nm laser irradiation. (B) Picture of formic acid-doped film (degree of doping 6 wt %) containing BP and HAuCl4 5 min afterthe 355 nm laser irradiation.,Accel

56、eration of Laser-Induced Formation ofGold Nanoparticles in a Poly(vinyl alcohol) Film,PVA (Mw ) (8.9-9.8)x104), BP, 2-mercaptoethane sulfonate, 2-巰乙基磺酸,Polyvinyl alcohol,,,反應(yīng)歷程：Reaction mechanism,formic acid-doped,BPH?

57、 radical,PVA radical,,,Laser-Induced Self-Assembly of Pseudoisocyanine J-Aggregates Yoshito Tanaka isocyanine [ais?u'sai?ni:n]異花青 Pseudo [‘psju:d?u]偽-,Laser-Induced Organic Molecules Self-Assembly,A 1064 nm near

58、-infrared (NIR) laser beam from a continuous waveNd-YAG laser was introduced into an inverted microscope and focused on a 520 nm spot by a 100 Plan-Neofluar objective lens,光誘導(dǎo)異構(gòu)化反應(yīng),花青,,,4.3.激光選擇化學(xué)反應(yīng)Laser-induced select

59、ive chemical reaction2,有些化學(xué)反應(yīng)(熱反應(yīng)、經(jīng)典光化學(xué)反應(yīng)等)在通常條件下是一種方向，而在激光的作用下則會(huì)改變反應(yīng)方向。或是在混合物中，或是同位素中，激光能激發(fā)某些原于、分子或同位素，而其余則不被激發(fā)，這種反應(yīng)稱(chēng)之為定向反應(yīng)或選擇化學(xué)反應(yīng)。激光選擇化學(xué)反應(yīng)已成了無(wú)機(jī)物分離提純的全新技術(shù)手段。,,,激光選擇分離稀土元素 稀土元素的化學(xué)性質(zhì)是非常近似的。用化學(xué)方法分離，不但工藝繁雜，而且效率低，成

60、本高。美國(guó)海軍研究所Donohue等人用準(zhǔn)分子激光器的紫外輸出引發(fā)液相中的稀土元素反應(yīng)，成功地分離了銪和鈰。,,氧化態(tài)的變化會(huì)引起溶解度、可萃取性或反應(yīng)性的變化，再用適當(dāng)?shù)幕瘜W(xué)方法就可達(dá)到分離之目的。例如，用氟化氬激光器193nm的紫外光輸出激光激發(fā)Eu3+的水溶液，可使Eu3+還原為Eu2+，再用SO42-沉淀，而鈰留在溶液之中。反應(yīng)為： 在0.01mol/L的Ce稀土溶液中進(jìn)行實(shí)驗(yàn)，用250nm的激光照

61、射稀土溶液，就會(huì)發(fā)生光氧化反應(yīng)，再用IO3-沉淀，反應(yīng)為：,,,,,4,,,利用激光的方向性可實(shí)現(xiàn)顯微化學(xué)反應(yīng)，這在集成電路和半導(dǎo)體器件的生產(chǎn)中可用于修補(bǔ)、掃描無(wú)掩膜光刻、歐姆接觸及局部摻雜等。,4.4 激光顯微化學(xué)反應(yīng),（a)激光化學(xué)沉積（LCVD） 化學(xué)氣相沉積(CVD)是晶體生長(zhǎng)和薄膜生長(zhǎng)的一種有效技術(shù)， 它是通過(guò)加熱置于氧化或還原氣氛中的基板進(jìn)行氣相沉積，通常在整個(gè)基板表面上都有沉積發(fā)生。CVD特點(diǎn)：基板進(jìn)行長(zhǎng)時(shí)間

62、的高溫加熱，因此不能避免雜質(zhì)的遷移和來(lái)自基板的自摻。 LCVD優(yōu)點(diǎn)：不用直接加熱整塊基板，可按照需要進(jìn)行沉積?？臻g選擇性好，甚至可使薄膜生長(zhǎng)限制在基板的任意微區(qū)上。局部可控沉積,,,激光沉積與化學(xué)氣相沉積相比具有很多優(yōu)點(diǎn)：(1)激光學(xué)沉積面積只有10-4 cm2，而化學(xué)氣相沉積則是數(shù)個(gè)cm2。(2) SiH4的壓力比化學(xué)氣相沉積高2-3數(shù)量級(jí)。沉積速率比化學(xué)氣相沉積快2-3數(shù)量級(jí)。,SiH4/Ar,CO2激光作用熱源,,石英片作基

63、板,1000-1200℃,硅沉積在石英片,Si-SiO2,美國(guó)南加利福尼亞大學(xué)Christensen,,,4.5 激光合成精細(xì)陶瓷粉末,,?m,美國(guó)麻省理工學(xué)院的能量及材料加工實(shí)驗(yàn)室的J.Haggar等人,CO2激光器(10.6?m),SiH4和NH3混合氣體(強(qiáng)吸收10.6 ?m光子),,在同樣條件下也可合成SiC粉末：,?m,氮化硅是一種重要的結(jié)構(gòu)陶瓷材料。它是一種超硬物質(zhì)，本身具有潤(rùn)滑性，并且耐磨損，為原子晶體；高溫時(shí)抗氧化。而

64、且它還能抵抗冷熱沖擊，在空氣中加熱到1000℃以上，急劇冷卻再急劇加熱，也不會(huì)碎裂。,,,激光合成精細(xì)陶瓷粉末的基本原理：1）利用了反應(yīng)物對(duì)激光的強(qiáng)吸收性，用吸收的能量引發(fā)氣相化學(xué)反應(yīng)，生成固態(tài)精細(xì)粉末。2）生成物最好對(duì)激光不吸收或很少吸收。 特點(diǎn)：a.反應(yīng)區(qū)界限很分明，而且范圍??； b. 具有反應(yīng)氣體均勻快速的加熱率； c. 具有生成物的快速冷卻率；

65、 d. 具有反應(yīng)溫度的閾值； 當(dāng)溫度高于這一值時(shí)，反應(yīng)快速進(jìn)行，均勻成核。,,綜上所述：激光在無(wú)機(jī)化學(xué)中的應(yīng)用是非常廣泛的。隨著現(xiàn)代科學(xué)技術(shù)的進(jìn)步和激光技術(shù)的發(fā)展，光技術(shù)一定會(huì)在無(wú)機(jī)化學(xué)中得到更廣泛的應(yīng)用。,,,4.6 脈沖激光沉積鍍膜Pulse Laser-induced Deposition Films,Pulse Excimer laser所產(chǎn)生的高功率脈沖激光束聚焦作用于靶材料表面，使靶材料表面產(chǎn)生高溫及熔蝕

66、，并進(jìn)一步產(chǎn)生高溫高壓等離子體（T≥104K）High Temperature and High Pressure Plasma, 這種等離子體定向Orientation局域膨脹發(fā)射并在襯底上沉積而形成薄膜。,,脈沖激光沉積鍍膜示意圖,優(yōu)點(diǎn)：,①易于保證鍍膜后化學(xué)計(jì)量比的穩(wěn)定②反應(yīng)迅速，生長(zhǎng)快。③定向性強(qiáng)、薄膜分辯率高，能實(shí)現(xiàn)微區(qū)沉積 ④生長(zhǎng)過(guò)程中可原位引入多種氣體 ⑤易制多層膜和異質(zhì)膜 ⑥易于在較低溫度下原位生長(zhǎng)取向一致的結(jié)

67、構(gòu)和外延單晶膜,Scanning electron microscopy micrographs of the deposited films revealed that PTFE grains were uniformly grown on the cotton surface with an average grain size of about 50–70 nm.,using a KrF 248 nm excimer laser,

68、The laser energy was fixed at 1 J/cm2,Pulsed laser deposition (PLD) was utilized to deposit polytetrafluoroethylene (PTFE) thin films on cellulosic cotton substrates at room temperature.,a cellulosic cotton fiber,PTFE de