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Molten salt electrolyzer

Molten salt electrolyzer

Nov 25,2022

It is mainly used to produce low melting point metals. It is characterized by operating at high temperatures, and should try to prevent moisture from entering and hydrogen ions from reducing on the cathode. For example, when preparing metal sodium, because the cathodic reduction potential of sodium ions is very negative, it is difficult to reduce. It is necessary to use anhydrous molten salt or molten hydroxide without hydrogen ions to avoid hydrogen precipitation from the cathode. For this reason, the electrolysis process needs to be carried out at a high temperature. For example, when sodium hydroxide is melted by electrolysis, the temperature is 310 ℃. If sodium chloride is contained in it as a mixed electrolyte, the electrolysis temperature is about 650 ℃. The high temperature of the electrolytic cell can be achieved by changing the electrode spacing and converting the electric energy consumed by the ohmic voltage drop into heat energy. When electrolyzing molten sodium hydroxide, iron or nickel can be used as the tank body. When electrolyzing molten electrolytes containing chlorides, a small amount of water is inevitably brought into the raw materials, which will cause the anode to generate moist chlorine gas, which has a strong corrosion effect on the electrolytic tank. Therefore, ceramic or phosphate materials are generally used for electrolyzing molten chlorides, and iron can be used for the parts not affected by chlorine gas. The cathode and anode products in the molten salt electrolyzer are also required to be properly separated, and should be led out of the bath as soon as possible to prevent the cathode product sodium metal floating on the electrolyte surface for a long time, which will further interact with the anode product or the oxygen in the air.

Classification according to electrolyte

Classification according to electrolyte

Nov 25,2022

Aqueous solution electrolyzer The form of aqueous solution electrolyzer can be divided into diaphragm electrolyzer and non diaphragm electrolyzer. Diaphragm electrolyzer can also be divided into homogeneous membrane (asbestos wool), ionic membrane and solid electrolyte membrane (such as β- Al2O3); Diaphragm free electrolytic cell is also divided into mercury electrolytic cell and oxidation electrolytic cell. When different electrolytes are used, the structure of the electrolytic cell is different. Aqueous solution electrolyzers are divided into diaphragm and non diaphragm. Diaphragm electrolyzer is generally used. Diaphragm free electrolytic cells are used in chlorate production and mercury production of chlorine and caustic soda. The production intensity of electrolytic cell can be improved by increasing the electrode surface area in unit volume as much as possible. Therefore, most of the electrodes in modern diaphragm electrolyzers are vertical. The performance and characteristics of electrolytic cells are different due to different materials, structures and installation of internal components

Shape and advantages of titanium electrode

Shape and advantages of titanium electrode

Nov 25,2022

Considerations for designing titanium electrode types 1. Requirements for anode in the installation of titanium electrode electrolyzer 2. Titanium electrode process conditions, such as electrolyte (liquid) composition, temperature, current density, service life, etc 3. Mechanical load of titanium electrode 4. Conductivity of titanium electrode matrix material Titanium electrode shape Plate, rod, sheet, filament, reticulate, tubular, annular, ribbon, basket and other shapes Advantages of titanium electrode 1. High current efficiency and good energy-saving effect 2. Excellent corrosion resistance 3. After the active layer is deactivated, it can be recoated and the substrate can be reused 4. Long service life of electrode 5. Titanium electrode has light weight and good dimensional stability 6. It can be made into any complex shape and size to meet the actual needs

Research progress of titanium alloys for aviation

Research progress of titanium alloys for aviation

Nov 25,2022

1. High strength and toughness β Type I titanium alloy β Type I titanium alloy has good processability, is easy to forge, roll and weld, and can obtain high strength and fracture toughness through solution aging treatment. At present, it has obtained high strength and toughness for practical application in aircraft β Type I titanium alloys mainly include the following: Ti-1023 (Ti-10V-2Fe-3Al) titanium alloy was developed by American Timet Company in 1971. It is a forged titanium alloy with high structural efficiency, high reliability and low manufacturing cost to adapt to the damage tolerance design principle. The Al equivalent of this alloy is 4.0, and the Mo equivalent is 11.1（ α+β)/β The phase transition temperature is 790~805 ℃, which has greater hardenability, significant heat treatment strengthening effect and excellent forging performance. Isothermal forging can be carried out at 760 ℃, providing various near net machined forgings. After heat treatment σ B is 965 ～ 1310MPa, KIC is 99 ～ 33 MPa · m1/2. It has been used for the landing gear main beam of Boeing 777 passenger aircraft and the main landing gear strut of Airbus A380. Ti-l5-3 (Ti-15V-3Cr 3Al - 3Sn) high strength β Titanium alloy was developed in the 1970s under the support of the US Air Force β High strength corrosion-resistant alloy. The Al equivalent and Mo equivalent of the alloy are 5.0 and 15.7 respectively（ α+β)/β The phase transition temperature is 750~770 ℃. It has excellent cold deformation, age hardening and weldability. Its cold workability is better than that of industrial pure titanium. It can be used for cold forming of various complex parts in the solid solution state. It has small crack sensitivity σ B ≥ 1310MPa, this alloy is particularly suitable for manufacturing rocket engine propellant tanks, conduits and other components, and has been applied to the application control system pipes and fire extinguishers on the Boeing 777. β- 21S (Ti-15Mo-3Al-2.7Nb-0.2Si) alloy is an anti-oxidation and ultra-high strength titanium alloy developed by American Timet Company in 1989. The Al equivalent of the alloy is 4.0, and the Mo equivalent is 15.8（ α+β)/β The phase transition temperature is 793 ～ 810 ℃, which has good oxidation resistance and can work at 540 ℃ for a long time; Excellent cold and hot working performance. After heat treatment, σ b=1150～1350MPa， δ 5=6%～8%。 The alloy is suitable for engine liner and nozzle, and has been used as the matrix material of silicon carbide/titanium composite by NASA. BT22 (Ti-5Al-5Mo-5V-1Fe-1Cr) alloy is a high strength alloy developed in Russia in the 1970s β Type I titanium alloy. The Al equivalent of the alloy is 6.0, and the Mo equivalent is 11.8（ α+β)/β The phase transition temperature is 860 ～ 990 ℃, which has good processing and welding properties. It is mainly used to produce die forgings. Its quenching depth reaches 200mm σ b≥1105MPa。 The alloy can be used to manufacture fasteners for fuselage, wing force bearing parts and operating system, etc. that work at 350~400 ℃ for a long time, and also can be used to manufacture fan disks and blades of engines that work at temperatures below 350 ℃. It has been used for the fuselage, wing, landing gear and other high load bearing parts of 1L-86 and 1L-96-300.

Multilevel structure high activity electrolytic water electrode

Multilevel structure high activity electrolytic water electrode

Nov 25,2022

With the rapid consumption of fossil fuels and environmental pollution, it is imperative to develop renewable energy. Hydrogen is expected to replace traditional fossil fuels because of its clean and renewable characteristics. The key to the deep utilization of hydrogen energy lies in the low-cost and large-scale preparation of hydrogen. Hydrogen production by electrolysis of water is one of the effective ways, but its anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER) still show high overpotential, which greatly limits the efficiency of hydrogen production by electrolysis of water. So far, precious metal materials Pt/C and IrO2 are efficient catalysts for HER and OER respectively, but their high price and limited storage limit their large-scale application. Although the research of non noble metal HER and OER catalysts has made a series of progress, there are still some challenges. For example, how to prepare highly active multi-stage nanostructured electrodes in a simple and large-scale way to achieve full water electrolysis under high current density is still one of the problems and challenges to be solved. Recently, the research team of Hu Jinsong, a researcher of the Institute of Chemistry of the Chinese Academy of Sciences, cooperated with Professor Li Jihui of Hebei Normal University, and reported a simple chemical etching method, in which industrial NiAl alloys are immersed in strong alkaline solutions. Because metal Al is easy to be etched by strong alkaline solutions, and metal Ni is easy to react with strong alkaline, Ni (OH) 2 nano sheet arrays are directly generated on the NiAl alloy substrate, A multi-stage framework Ni (OH) 2/NiAl with high porosity is formed. Electrochemical studies showed that the framework exhibited good OER catalyst performance, and the overpotentials at current densities of 10 and 100 mA cm-2 were 289 and 425 mV, respectively. On this basis, the researchers deposited NiMo alloy with higher activity for hydrogen evolution reaction and NiFe alloy with higher activity for oxygen evolution reaction on the Ni (OH) 2/NiAl active skeleton respectively by a simple electrodeposition method, and obtained more efficient hydrogen evolution electrode NiMo/Ni (OH) 2/NiAl and oxygen evolution electrode NiFe/Ni (OH) 2/NiAl through the composite of active material and three-dimensional multi-stage active bone frame structure. The overpotential of the obtained composite hydrogen evolution electrode at 10 mA cm-2 is only 78 mV; And the overpotential of the composite oxygen evolution electrode at the current density of 10, 100 and 500 mA cm-2 is only 246, 315 and 374 mV respectively. The cell voltage of the electrolyzed water device composed of these two electrodes under alkaline conditions is only 1.59 V at a current density of 10 mA cm-2. Because the preparation method of the electrolytic water electrode in this research work is extremely simple, and the raw materials are easy to obtain, the high efficiency water electrolysis can be achieved by directly immersing industrial NiAl alloy in alkaline electrolyte. At the same time, the design of multi-stage electrode structure is conducive to the realization of electrolytic water under current density, so it is very convenient for large-scale preparation and practical industrial application, and is expected to achieve large-scale production and application. This method of etching industrial alloys to prepare electrodes of electrochemical devices with multi-level nanostructures also provides a new idea for designing other highly active electrodes.

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