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电化学合成技术(Electrochemical synthesis)

电化学合成技术(Electrochemical synthesis)
电化学合成技术(Electrochemical synthesis)

电化学合成技术(Electrochemical synthesis)Refrigeration, cold, cold, extreme cold: reduce the temperature of local space to less than ambient temperature, known as refrigeration. Reduced to 123K is called pu cold, 123k-4.2 K is called deep cold, reduced to 4.2 K, which is called extreme cold.

Dynamic pressure, the use of explosion (nuclear explosion, gunpowder, etc.), such as strong discharge produced by shock wave, in an instant effect on objects at high speed, can make the object interior pressure over dozens of GPa, even thousands of GPa, accompanied by a sudden warming. This high pressure is called dynamic high pressure.

Static pressure: using the external mechanical loading way, by applying load slow gradually extrusion research object or sample, when its smaller, just inside the object or sample of internal high pressure. The high pressure produced is called static pressure because of the slow loading of the outside world (usually not accompanied by the temperature of the object).

Primary pressure measurement: based on the known basic relationship between pressure and other parameters, the corresponding parameters are established to calculate the pressure. Secondary pressure test: the pressure is measured according to the variation of the pressure component.

Vacuum, vacuum, vacuum pump: a given space that is lower than the atmospheric pressure. The degree of vacuum close to vacuum is in the system. A device for producing a vacuum is called a vacuum pump.

Absolute vacuum gauge, relative vacuum gauge: measuring the vacuum measure, the direct measurement of pressure is called an absolute vacuum gauge; The measurement of the physical quantity relating to the pressure, its pressure scale needs to be calibrated with an absolute vacuum gauge, called a relative vacuum gauge.

Illustrate manometry and secondary manometry answer: primary manometry: mercury manometer and free piston meter is according to the relation between p = F/a measurement function in the area of a force F, the two primary stress of pressure p.

What are the criteria for dividing a vacuum? Answer: low vacuum, medium vacuum high vacuum, high vacuum, high vacuum, high vacuum

The operating characteristics of the vacuum pump are usually characterized by the following parameters:

A limit pressure: the minimum pressure that can be reached at the entrance of the pump after a long period of pumping without gas escaping into the pump.

B pumping rate: the volume of gas flowing through the air inlet section of the pump at a certain pressure.

C maximum inlet pressure: the pressure of the pump before starting to work.

D maximum pressure: the maximum pressure that the pump outlet can withstand without damaging the vacuum pump.

E vacuum production rate: the quality of the gas discharged by the pump in a unit time.

F compression ratio: the ratio of the outlet pressure of the vacuum pump to its inlet pressure.

Chemical vapor deposition method: a technique of producing solid sediments in gas or gas-solid interfaces by gaseous or vapor pressure.

Working principle of thermocouple, advantages and disadvantages. A: two different ingredients of conductor (called the thermocouple wire or hot electrode) synthesis loop at both ends, when the junction temperature is not at the same time, in the circuit will generate electromotive force, this kind of phenomenon called the thermoelectric effect, and the electromotive force called thermoelectric potential. Thermocouple is to use the principle of temperature measurement, which directly used for measuring the medium temperature is called the work at the end of the end (also known as measuring side), the other end is called the cold end (also known as compensation); The cold end is connected with the display instrument or supporting instrument, indicating the thermoelectric potential generated by the thermocouple. Advantages: high accuracy of measurement. Because the thermocouple is directly in contact with the measured object, it is not affected by the intermediate medium. The measurement range is wide. The commonly used thermocouple from - 50 ~ + 1600 ℃ are measured. The structure is simple and easy to use. Thermocouples are usually made of two different kinds of wires, and they are not limited by size and opening, and they are very convenient to use.

The mechanism of high temperature fixation should be composed of two processes: chemical reaction in phase interface and material transfer in solid phase. The chemical reaction on the

phase a, for different response systems, involves different stages,

But all these include the following three processes: the contact between the reactants and the surface effect, the chemical reaction and the new phase composition, crystal growth and structural defect correction. When the reaction is active or liquid, the reaction will not be limited to the interface of the direct contact of the material, but may also be carried out along the free surface of the whole reactant particle. B. The reactant is diffused through the product layer. Migration diffusion can be carried out through crystal internal lattice, surface, interface or crystal fissure. Characteristics: 1) the solid opposite should generally include the reaction of matter in the phase interface and the process of material migration.

2) it usually takes place at high temperature. 3) the entire solid should be controlled by the slowest speed. 4) the reaction products of solid reaction should be periodic: raw materials, original products, intermediate products, and final products.

In chemical transport reaction, how to select and control temperature according to the heat effect of the reaction? A: if the reaction is endothermic reaction, ΔH is positive, then control source area temperature T1, T2 is higher than deposit zone temperature T2 is greater than the T1, namely this kind of reaction is to transport material has a high temperature to low temperature area. Conversely, when the reaction is exothermic reaction, Δ H negative, then control source area temperature is lower than the deposition area, namely the T2 is less than the T1, this kind of reaction is the material to the high transportation by the low temperature area.

To prepare solid powders under high temperature and reducing atmosphere conditions, which equipment are needed and how to install them? Answer: equipment: tube furnace, electrolytic hydrogen plant. A thin layer of WO3 is sprinkled into the nickel boat, and the flow of the hydrogen is gradually moving the nickel boat through the tube, then through the high temperature zone into the cooler. This process is divided into two stages, the first stage is to make the WO3 at 720 c, reductive into brown WO2, then will get WO2, mixed with the same amount of WO3 and mixture in 800 ~ 860 c temperature reduction of metal tungsten, in the first stage of the reduction furnace temperature along the pipe heating parts from 520 c heats up to 720 c. In the second stage of the reduction, the furnace temperature increased from 650C to 860C. The quality of WO3 in each nickel boat was 50 ~ 180g because of the size of the furnace used

Commonly used refrigeration methods. Answer: the common method to cooling can be divided into physical methods and chemical methods, one of the commonly used gas adiabatic expansion refrigeration and cases of refrigeration, another half of the semiconductor refrigeration, gas throttling, eddy current cooling, adiabatic deflated refrigeration, thermoelectric refrigeration.

The storage and transfer of liquefied gases: the containers of liquefied gases, which are different from the size and purpose of the volume, usually have low temperature containers, liquid gas storage tanks and so on. Small containers consist of a two-layer copper ball, which is divided into liquid nitrogen and gas containers. The liquid gas storage tank is composed of

the outer shell, adiabatic structure and the mechanical structure of the inner and outer shell. There are many ways to go from a liquid gas plant to a liquid. Such as liquid air removed from a liquid air tank, the available methods of dumping or with a small siphon, is a large amount of liquid air, a small rubber ball pump up available liquid air play.

Hard chemical: originally refers to the high temperature solid instead should method, and with the development of the synthesis technology, the concept of hard chemical tend to "chemistry" extreme conditions, such as ultra high temperature, super high, super vacuum, plasma, etc

Soft chemistry: a chemical reaction that is achieved under mild conditions

Green chemistry: green chemistry refers to the use of chemical products only in the manufacture and application of chemical products (preferably renewable) materials, eliminating waste and avoiding the use of toxic and dangerous reagents and solvents. Today's green chemistry is chemical technology that protects the environment.

Sol-gel synthesis: an organic metal compound, metal inorganic compound or the mixture of two kinds of the hydrolytic condensation process, gradually gel post-processing accordingly, finally get the new technology of oxide and other compounds

Hydrothermal synthesis: in a certain temperat ure (100 ~ 1000 ° C) and pressure (1 ~ 100 mpa) under the condition of using the

chemical reaction of synthesis in solution

Coprecipitation synthesis technology of the requirements of a metal ion salt solution of dissolved in the water large b precipitant to metal ion precipitation precipitation c at the same time according to certain stoichiometric ratio sol agglutination of synthetic process of a source material molecules polymerization, condensation, clusters and colloidal particles grew up the formation of sol b with former body polymerization and polycondensation, gradually form a network structure of the gel, in the process, can form a variety of polymer gel structure c aging, polycondensation reaction in the process continues until the form has a solid 3 d mesh structure d gel dry, accompanied by evaporation of water and volatile matter e pyrolysis stage, in the process, the reticular formation of the gel completely collapsed, before bodies decompose organic matter, completely volatile, at the same time, the crystallinity of target product

Inorganic salt hydrolysis and polymerization of type a hydrolysis: metal ion hydrolysis polymerization b: hydroxyl polymerization, polymerization metal organic molecular oxygen hydrolysis and polymerization of type a polymerization: the aggregation of alkylation, polymerization, bridge oxygen hydroxyl polymer

High temperature self-propagating synthesis: materials are prepared using the heat energy of raw materials themselves

The characteristics of the high temperature self-propagating technology energy fully, products with high purity and high

yield, product defects and non equilibrium phase in the more concentrated, so as to make the product more flexible, can make certain the stoichiometric ratio of products, intermediate products and the stationary phase interface

The characteristics of high temperature and high pressure water are characterized by the increase of vapor pressure and the ion deposition of water. Water density, viscosity, surface tension and dielectric constant decrease

The properties of other substances in water under high temperature and pressure change a SiO2: it is not soluble in water at normal temperature, and the solubility can reach 0.16% with the increase of temperature. The solubility of SiO2 in NaOH solution can reach 2.4% b NaBr at room temperature, which is 100% dissociated in water, and the dissociation degree decreases at high temperature and high pressure, and the recrystallization occurs

The reaction of qian yitai's preparation of diamond with solvent heat is as follows

CCl + 4 na - > C + 4 nacl reaction conditions is 700 ° C

High temperature and high pressure should also convert graphite into diamond. The design of the experimental design for the preparation of diamond was analyzed by using non-hydrolytic Na as solvent. The three-dimensional network structure of diamond is C (sp3 hybridization), two-dimensional plane structure of graphite is C (sp2 hybridization) C in the CCl is sp3 hybridization, so you don't have to graphite, diamond, C to

replace the Cl in CCl

Electrochemical synthesis: a method of synthesis by electrochemical reaction.

Photochemical synthesis: photochemical reactions that are difficult or must be synthesized by chemical reactions with a chemical reaction.

Decomposition voltage: the electrolyte begins to decompose the voltage.

Overvoltage: the difference between the actual starting voltage and the theoretical decomposition voltage.

Plasma: plasma is also called plasma, which is the ionized gas formed by the ionization of the atoms and atoms after the partial electrons are ionized. It is a state of highly ionized matter, a collection of positive and negative ions, electrons and neutral particles.

Microwave synthesis technology, the use of microwave strong electric fields, generated in the microwave using thermodynamic method is less than the upper state atoms, molecules and ions, thus can make some on thermodynamics was not able to response to the synthesis technology.

When metal deposition is carried out in electrochemical synthesis technology, how does the current density affect the morphology of the metal? Low - crystal growth time sufficient, not to form new nucleation, large, coarse. High - form more

nuclei, tiny and even powdery grains. High - the crystals tend to grow in the metal ion concentration and grow into a tree.

How does hot plasma come about? How is cold plasma produced? Hot plasma is produced by arc or ion moment. The cold plasma is produced by low intensity arc, microwave heating and glow discharge.

The key to the growth of crystal growth in solution? A solution should be sufficiently high to eliminate the micro-crystal b to find the quasi-saturation point c to be strictly sealed in the growth process by the high precision cooling d

The lifting method of the growth crystals in the melt, the moving crucible method and the equipment of the zone melting method,

Advantages and disadvantages of various methods? Pulling method advantages in the process of growth, a class to observe the growth condition of crystal directly, that provides a favorable conditions to control the crystal shape b crystal growth on the surface of the melt child accidentally place and do not contact with the crucible, can significantly reduce the stress of the crystal and prevent crucible wall send generating nuclear c can convenient use directional seed crystal and the "neck". Get a different orientation of single crystal, reduce the dislocation density in the crystal, reduce the Mosaic structure, improve the integrity of the crystal d to faster the rate of growth of high quality crystal defects of a general to make container with crucible, lead to melt with varying degrees of pollution when the melt containing volatile matter, b

control component is difficult to use c to have certain limitations

Moving crucible advantages due to seal the raw material in the crucible, a reduced can cause leakage and pollution of the hair, to the composition of crystal easy control operation, can grow a large size of crystal, crystal varieties can grow to be also many, and easy to realize programmed growth c because each crucible melt can separate nucleation, so that we can in a crystal furnace into several crucible, at the same time, it may improve the yield and efficiency

Shortcoming is not suitable for growth in the make a volume increase of crystal b because the crystals in the whole growth process in direct contact with the crucible, tend to introduce large internal stress in the crystal and more impurity c is difficult to directly observed in the process of crystal growth, growth cycle is long d if using seed crystal growth in the descent method, how to make the seed crystal in high temperature is neither completely fused, and must make it with partial melting to full growth, it is hard to control technical problems

Zone melting method (1) the horizontal zone melting method merit a reduced the crucible melt pollution, and reduce the heating rate b zone melting process can be repeated, so as to improve the purity of crystals or make doping uniformity

(2) the advantages of floating zone method doesn't need a crucible, melt with itself only contact, pollution can be reduced to a minimum b growth process is easy to observe drawback strict in heating technology and mechanical

transmission device flame fusion method merit a growth of single crystal don't need crucible, do the high temperature resistance of the crucible, the material is saved, and avoid the pollution problem of crucible b oxyhydrogen flame combustion, the temperature can reach 2800 degrees Celsius, gu grow high melting point of single crystal growth rate and rapid d c can grow larger crystal defects of a flame temperature gradient is bigger, in the growth of single crystal in poor quality b because the heat source is burning gas, temperature control of stable c grow single crystal of the dislocation density is higher, larger internal stress d for volatile or easy to be oxidized materials, should not use this method single crystal growth

Crystallization: the process of crystallization of a liquid metal into a solid metal forming a crystal.

Phase change: the mutation occurs in a particular condition (or critical value) in the process of change in the external conditions.

Partial coagulation: a kind of operation that condenses a mixture of steam to a certain temperature and the higher components of some boiling point in the original steam.

Uniform nucleation: in a cold liquid metal, the driving force is obtained by the energy change of the liquid metal itself, which is directly nucleated by the embryos.

Nonuniform nucleation: the process of crystallization of the embryo in a cooled liquid metal in the presence of other

substances on the surface.

Supersaturation: the concentration of a substance at a certain temperature, the concentration of the solution at the time of crystallization, and the saturation concentration of the substance at the temperature, or saturation.

有机电化学合成及研究进展

有机电化学合成及其发展方向 摘要 介绍有机电化学合成的原理,研究内容。有机电化学合成与传统合成的优势,介绍中国有机电化学合成的发展以及有机电化学的新进展。有机电化学的高效、经济、无污染性。还有有机电化学合成的若干发展方向。 关键词 有机电化学发展方向绿色化学 Review on organic electrosynthesis and its Development trend Abstract In this paper,the principle and the research method of organic electro- ynthesis---one of the most efficient green technology was discussed. The principle of organic electrosynthesis, applications, and the advantages co- mparing to the tradition organic synthesis were expounded. Introduction to Chinese organic electrosynthesis development and advancement of organic electrochemistry. Organic electrosynthesis of high efficiency, no pollution. There are several development directions of organic electrosynthesis. Key words:organic electrosynthesis;developments of research;Green Chemistry; 引言部分 以电化学方法合成有机化合物称为有机电合成,它是把电子作为试剂,通过电子得失来实现有机化合物合成的一种新技术,这是一门涉及电化学、有机合成及化学工程等学科的交叉学科。由于电化学早已有之,合成技术、化学工程技术和化学材料不断更新,因而,有人称之为“古老的方法,崭新的技术”[1]。 有机电合成是有机合成的一个分支学科,有其独特的优点和优势。有机电合成与一般有机合成相比,有机电合成反应是通过反应物在电极上得失电子实现的,一般无需加入氧化还原试剂,可在常温常压下进行,通过调节电位、电流密度等来控制反应,便于自动控制。这样,简化了反应步骤,减少物耗和副反应的发生。可以说有机电合成完全符合“原子经济性”要求,而传统的合成催化剂和合成“媒介”是很难达到这种要求的。从本质来说,有机电合成很有可能会消除传统有机合成产生环境污染的根源。有机电化学合成也是一种绿色化学,中国走可持续发展战略,在化学合成中有机电合成将会占很大比例。将是未来的合成化学的

电化学合成技术研究进展

电化学合成技术研究进展 摘要:电化学合成作为一种新型的合成方法,其研究和工业应用进展迅速,本文重点介绍了在溶液体系和熔盐体系中一些材料的电化学合成的合成工艺研究进展。最后展望了电化学合成的发展前景。 关键词:电化学合成氧化还原合成工艺 1溶液体系的电解合成 1.1 金属及合金的电沉积 金属电沉积,主要是在外加电场的作用下,金属或其合金从电解质中以晶体形式沉积。它包含了电镀、电提取、电解精炼等多种电沉积方式,是目前电化学合成金属材料的主要方法之一。其中电镀要求沉积金属与基体结合牢固,结构致密,厚度均匀,多用于表面工程处理,合成膜材料;其余两种方法则对合成产物与基体的结合力无特殊的要求,多用作材料的制备。用电解法制备的金属产品的优点主要是:产物的纯度高,控制电解条件可制得不同聚集态的金属,另外还可制备合金、金属镀层膜材料、有色金属的冶炼和提纯。 1.2 特殊高价态元素化合物的电氧化合成 19世纪初期,Rheinold和Erman发现电是一种强有力的氧化剂和还原剂。若要进行一个氧化反应,就必须找到一个强的氧化剂。但是若需要制备这些强的氧化剂,则很难再找到更强的氧化剂,因此,必须采用电化学方法。高锰酸钾是重要的锰化合物之一,目前,电解法制备高锰酸钾的优点是利用率高、能耗少。由于在电解过程中,阳极表面容易形成一层钝化膜,阻止阳极的进一步溶解,导致电流效率不高。Bouzek分别采用电解前阳极的阴极极化和交直流叠加的方法,提高了电解效率。Denvir等发现随着阳极中碳含量的增加,相应制备的高铁酸盐产率也有所提高。 1.3 低价态元素化合物的电还原合成 阳极能够制备高价态的氧化剂,而阴极则可以进行电还原反应,制备特殊低价态的元素化合物。曾海燕以活性炭纤维作为阴极,钛钌网作为阳极,无水硫酸钠作为溶液电解质,通过硫酸和氢氧化钠调节溶液的pH值,保持恒温的条件下电解后制得H2O2。半导体材料Si 的制备目前主要依据西门子法获得,林会会选用价格相对低廉的SUP13Cr不锈钢作为工作电极,在室温条件下非水溶剂碳酸丙烯酯中利用电化学方法还原SiCl 4在室温下获得沉积Si。范小振利用草酸的电还原成功地制备了羟基乙酸,是一种有机合成中间体和化工产品,应用很广,可用于医学工程材料和高分子材料等领域。一种重要的有机精细化工中间体-对氨基苯酚(PAP)可利用硝基苯电解还原法制取,与传统的化学制备方法相比具有污染较少,产品品质高,工艺简单等优点。但是这种方法的关键问题在于硝基苯在介质中的溶解度很小,而电解合成中只有溶解的硝基苯才能有效的参与反应,Noman在含7%的硝基苯中,以硫酸作支持电解质的电解液中加入氧化二甲基十二烷基胺,作为表面活性剂,以Cu(Hg)为阴极,PAP的产率高达95%。目前,电化学方法合成有机物的报道较多,主要是利用较为廉价的有机原料(如草酸,葡萄糖等)通过电还原制备附加值较高的电化学中间体,这种方法工艺简单,节能环保,应该在以后的生物医学、高分子材料等领域发挥越来越大的作用。1.4 纳米金属氧化物的电化学合成 电化学合成是制备纳米材料的一种新思路,能够有效地控制合成产物的成分和形貌。金属氧化物是一类重要的功能材料,常需要达到纳米尺度才能表现其具备独特的物化性能。如廖学红在不同配位剂存在下,用电合成方法制备出球形银纳米粒子和树枝状的纳米银;Switzer率先介绍了用电化学的方法合成陶瓷薄膜和多晶粉体,并电解硝酸铈合成了纳米级CeO2粉体。周幸福率先实现了在非水体系中电解金属直接水解法制备纳米NiO 粉体。

电化学法处理生活污水的性能研究

洛阳理工学院毕业设计(论文) 题目电化学法处理生活污水的性能研究 姓名杨振宇 系(部)环境工程与化学系 专业环境工程 指导教师吴长航 2013 年 6 月 2 日

电化学法处理生活污水性能的研究 摘要 鉴于生活污水处理存在设备复杂、残留物浓度过高等问题,采用电化学法对生活污水进行试验研究,分析了电化学法在水处理中的反应原理,以及其具有操作简单、自动化性强、环境兼容性好等优点。实验以IrO2 - Pt / Ti惰性电极为阳极,铜片为阴极,分别考察了电流密度、极板间距、氯离子浓度对污水中氨氮去除率的影响。实验得出当电流密度为30 mA/cm2,极板间距为2 cm,氯离子浓度为200mg/L时为最佳去除工况,这时氨氮的去除率最高,达到了国家要求的生活污水二级排放标准。同时提出了电化学法处理生活污水还需要解决能耗大、工业化应用等问题。 关键词:电化学法,生活污水,去除率,氨氮

The Research on Electrochemical Treatment of Sewage ABSTRACT According to the problem that the sewage treatment equipment complex and residue concentration is too high, experimental study of the sewage by electrochemical method, and analyzes the principle of electrochemical reaction in water treatment, and it has simple operation, automatic strong sex, as well as good environmental compatibility. As IrO2-Pt / Ti inert electrode is for anode, copper cathode, respectively investigates the current density, plate spacing, the chloride ion concentration of ammonia nitrogen removal rate in wastewater. Experiment when the current density of 30 mA/cm2, plate spacing is 2 cm, the chloride ion concentration of 200 mg/L when is the best working condition of removing, then ammonia nitrogen removal rate is highest, up to the national request of sewage secondary emission standards. Proposed the electrochemical method deal with sewage also need to solve the problem of large energy consumption, industrial application, etc. KEY WORDS: Electrochemical method, Sewage, Removal, NH4-N

埃马克高精密电解加工(PECM)技术2_图文

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过程中所需的高难度任务。正如 EMAG ECM 技术销售主管理查德 ·凯勒所说:“在加工高强度合金时,许多用户至今仍依赖高速铣削和电火花放电加工。但是这项技术有自己的劣势,比如,工具磨损非常大,而且产生高温对材料造成不良影响。在PECM 中,则不会存在这些问 页码 2 — 6 题,即使出现这些现象,所造成的影响也是微不足道的。事实上,这正是该项工艺的特殊优势所在。” 高质量的工艺 该项工艺具有出众的优势:加工高强度合金(又被称为“超级合金”以及其它难加工材料时,工具基本上没有明显的磨损。产品表面光洁度非常高:没有毛刺,也没有材料结构损害。这是如何实现的呢?首先, EMC 工艺在清除材料的过程中,动作非常柔和。工件作为阳极,工具作为阴极,在这两极之间有电解液,电解液可以将金属离子从工件上剥离。由于工具的阴极形状代表了所期望的工件形状,因此仅在需要清除的地方清除材料即可。通过这种技术, 可以在非接触式、不受热效应影响的情况下加工出曲面、环形通道、凹槽或腔室等形状,并且能够确保最高的精确度。 更高的效率 凯勒先生说:“这项工艺使我们能够生产最为精致和复杂的零部件。我们已经有意识地将 ECM 发展为 PECM ,以确保我们能够在越来越小的部件上实现更高精度

电化学发展史

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8种电化学水处理方法

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电化学方法合成聚苯胺

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Abstract The technology of film science has developed rapidly since the 1950s. It is widely used in industry, agriculture, medicine and other fields. The organic film was developed first. It is well applied in many filds because of its flexibility, film-forming properties, and has many kinds of product. The electrochromic display film of polyaniline is one of electronically conducting polymers, it has a broad market prospect because it is easily synthesized, character uniform and can be firmly attached to the substrates. The work studied synthesis of polyaniline film on carbon cloth with three elctrodes by means of cyclic voltammograms. Synthesis of polyaniline films on carbon cloth are related to aniline concentration, solution acidity, bronsted acid type, linear scan rate and scanning numbers etc. It was found that the polyaniline electrochemical oxidation process is a self-catalytic process. It was found the higher the aniline concentration is, the esaier polyaniline synthesize is, because of the solubility of aniline in the water, sulfuric acid and aniline should be more than 1: 1 in concentration. Furthermore it was favorable to synthesize polyaniline films when reduce scan rate and increase the numbers of scanning appropriately, and the best scan rate is 25 mv/s. The activity of polyaniline films was significantly depended on the extent of the proton, in the solution of aniline and sulfuric acid bath, the greater the H2SO4concentration is, the greater the film’s redox reversible is, the stronger the self-catalytic effect is ,and sulfuric acid can promote the speed of synthesis of

电化学加工

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电化学合成技术(Electrochemical synthesis)

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电化学加工原理及应用总结

电化学加工原理及应用 电化学加工(Electrochemical Making),也称电解加工,是利用金属在外电场作用下的高速局部阳极溶解实现电化学反应,对金属材料进行加工的方法。常用的电化学加工有电解加工、电磨削、电化学抛光、电镀、电刻蚀和电解冶炼等。 电化学加工的原理: 电化学加工是利用金属在电解液中的电化学阳极溶解来将工件成型的。如图1 所示,工件接直流电源的正极为阳极,按所需形状制成的工具接直流电源的负极为阴极。阳极表面铁原子在外电源的作用下放出两个电子,成为正的二价铁离子而溶解进入电解液中(Fe-2e=Fe+2)。溶入电解液中的Fe+2又与OH-离子化合,生成Fe(OH)2沉淀,随着电解液的流动而被带走。Fe(OH)2 又逐渐为电解液中及空气中的氧氧化为Fe(OH)3红褐色沉淀。 正的H+被吸收到阴极表面,从电源得到电子而析出氢气(2H++2e=H2↑)。电解液从两极间隙(0.1~0.8 mm)中高速(5~60 m/s)流过。当工具阴极向工件进给并保持一定间隙时即产生电化学反应,在相对于阴极的工件表面上,金属材料按对应于工具阴极型面的形状不断地被溶解到电解液中,随着工件表面金属材料的不断溶解,工具阴极不断地向工件进给,溶解的电解产物不断地被电解液冲走,工件表面也就逐渐被加工成接近于工具电极的形状,如此下去直至将工具的形状复制到工件上。 电化学加工的应用: 电化学加工应用主要有电解加工、电化学抛光、电镀、电铸、电解磨削等方面。具体应用于发动机叶片加工、火炮膛线加工、加工锻模型腔、深孔、小孔、长键槽、等截面叶片整体叶轮以及零件去毛刺、难导电硬脆材料加工等。

航空发动机叶片加工----相对于叶片的几何结构及采用的材料, 电解加工能充分发挥其技术特长。尽管由于叶片精密锻造、精密铸造、精密辊轧技术的提高而有更多的叶片采用精密成形, 使电解加工叶片的数量有一些减少, 但随着叶片材料向高强、高硬、高韧性方向发展和钛合金、钴镍超级耐热合金的采用, 以及超精密、超薄、大扭角、低展弦比等特殊结构叶片的出现, 对电解加工又提出了新的、更高的要求, 电解加工依然是优选工艺方法之一。 如空心冷却涡轮叶片和导向器叶片上的许多小孔, 特别是深小孔和呈多向不同角度分布的小孔,用普通机械钻削方法特别困难, 甚至不能加工;而用电火花、激光加工又有表面再铸层问题, 且加工孔深也有限;采用电解方法则加工效率、加工质量明显提高, 加工孔深大大增加, 还可以采用复合多孔加工方式, 使加工效率提高几倍、十几倍。 为了满足第三代、第四代飞机高推重比、高可靠性的要求, 各类新型航空、航天发动机相继采用整体叶轮、整体叶盘结构。电解加工与数控技术的结合,是可望解决难切削材料整体叶盘的优质、高效、低成本加工问题的有效途径。 火炮膛线加工----随着兵器技术的发展,对火炮身管的要求也越来越高。随 着炮管材料变硬,膛线数目增多,槽线变深,缠角变大,机械拉削难以实现膛线的加工;因电解加工具有一次成型、加工效率高,离子级溶解、表面质量好,工具损耗小、无残余应力的优点,在深孔和膛线加工中尤为突出。因此,电解加工膛线变得不可或缺。 零件去毛刺----去毛刺是机械加工最后阶段必须进行的一项重要的技术,对 于可达性差、与主孔垂直的内部交叉阵列孔毛刺,一般的加工方法难以实现对其去除。目前国内主要采用手工的方法进行去除,该方法存在去除效率低、成本高的缺点,故需寻求一种去除效率高、自动化程度高的加工方法。 电化学去毛刺是金属在电解液中发生基于电化学作用的阳极溶解而去除零 件毛刺的加工工艺方法,这是一种先进的去毛刺技术,是电化学加工中发展较快、应用较广的一项工艺,它具有去除毛刺质量好、安全可靠、高效等优点,且能去除可达性差的复杂内腔部位的毛刺,现已在汽车发动机、航空航天、气动液压等领域得到运用。在汽车转向器中的螺杆轴上内交叉阵列小孔毛刺去除的实例实验验证中得到了良好的加工效果。 难导电硬脆材料加工----因半导体、光学玻璃、工程陶瓷等难导电硬脆材料 具有耐磨性强、硬度高等优良性能,故在电子、光学等领域得到了广泛应用。但难导电硬脆材料的脆性大,采用传统机械加工方法成本高、效率低,且易产生微裂纹,从而严重影响表面质量和性能。电加工是依靠电能、热能而不是机械能实现加工的,可以加工任何硬、脆、韧、软及高熔点的导电材料,而难导电硬脆材料一般不能直接采用电加工方法加工。郭永丰等研究了基于绝缘陶瓷辅助电火花加工原理在煤油中对绝缘陶瓷的电火花磨削加工,但加工效率较低。黑松彰雄研究了机械电解电火花复合磨削技术,该技术能实现对非导电陶瓷的高效精密加工,但仍存在放电难以控制和电能利用率低等问题。刘永红等提出了双电极同步伺服电火花机械复合磨削技术,实现了对非导电陶瓷的磨削加工,但辅助电极送给及控制系统较为复杂,导致放电状态难以精确控制。

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