电化学合成技术（Electrochemical synthesis）

1、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 pressur

2、e, 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

3、 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 sl

4、ow 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 p

5、ressure 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, relat

6、ive 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

7、 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, medi

8、um vacuum high vacuum, high vacuum, high vacuum, high vacuumThe 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 escapin

9、g 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 vac

10、uum 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 b

11、y 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 elec

12、tromotive 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 (

13、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 t

14、he 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

15、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 r

16、esponse 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 r

17、eaction 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, surfa

18、ce, 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

19、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, H is pos

20、itive, 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, H negative, then control s

21、ource 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

22、 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 divide

23、d 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 5

24、20 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 usedCommonly used refrigeration methods. Answer: the common method to cooling can be divided into p

25、hysical 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 trans

26、fer 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 cont

27、ainers. 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 wit

28、h 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

29、conditions, such as ultra high temperature, super high, super vacuum, plasma, etcSoft chemistry: a chemical reaction that is achieved under mild conditionsGreen chemistry: green chemistry refers to the use of chemical products only in the manufacture and application of chemical products (preferably

30、renewable) materials, eliminating waste and avoiding the use of toxic and dangerous reagents and solvents. Todays 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

31、condensation process, gradually gel post-processing accordingly, finally get the new technology of oxide and other compoundsHydrothermal synthesis: in a certain temperature (100 1000 C) and pressure (1 100 mpa) under the condition of using the chemical reaction of synthesis in solutionCoprecipitatio

32、n 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 polymeriza

33、tion, 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 conti

34、nues 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 crystal

35、linity of target productInorganic 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, polymerizati

36、on, bridge oxygen hydroxyl polymerHigh temperature self-propagating synthesis: materials are prepared using the heat energy of raw materials themselvesThe characteristics of the high temperature self-propagating technology energy fully, products with high purity and high yield, product defects and n

37、on 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 interfaceThe characteristics of high temperature and high pressure water are characterized by the increase of

38、vapor pressure and the ion deposition of water. Water density, viscosity, surface tension and dielectric constant decreaseThe 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

39、% 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 occursThe reaction of qian yitais preparat

40、ion of diamond with solvent heat is as followsCCl + 4 na - C + 4 nacl reaction conditions is 700 CHigh 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

41、 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 dont have to graphite, diamond, C to replace the Cl in CClElectrochemical synthesis: a method of synthesis by elect

42、rochemical 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

43、 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 particl

44、es.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 depositio

45、n 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 m

46、etal 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

47、 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 dThe lifting method of the growth crystals in the melt, the moving crucible method and the equipment of the zone melting method

48、,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 an

49、d 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 th

50、e 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

51、have certain limitationsMoving 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 real

52、ize 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 efficiencyShortcoming is not suitable for growth in the make a volume increase of crystal b because the crystals in th

53、e 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 c

54、rystal in high temperature is neither completely fused, and must make it with partial melting to full growth, it is hard to control technical problemsZone 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 doesnt need a crucible, melt with itself o