Anodes needle

Iron carbide (3 1), Fe C mol wt 179.56 carbon 6.69 wt % density 7.64 g/cm mp 1650°C is obtained from high carbon iron melts as a dark gray air-sensitive powder by anodic isolation with hydrochloric acid. In the microstmcture of steels, cementite appears in the form of etch-resistant grain borders, needles, or lamellae. Fe C powder cannot be sintered with binder metals to produce cemented carbides because Fe C reacts with the binder phase. The hard components in alloy steels, such as chromium steels, are double carbides of the formulas (Cr,Fe)23Cg, (Fe,Cr)2C3, or (Fe,Cr)3C2, that derive from the binary chromium carbides, and can also contain tungsten or molybdenum. These double carbides are related to Tj-carbides, ternary compounds of the general formula M M C where M = iron metal M = refractory transition metal. 

Property Aluminum anode-grade coke Graphite electrode-grade needle coke... 

Petroleum cokes, on the other hand, represent the second largest source of consumable industrial carbon in the United States. In 1992, about 2 million tons of anode coke and 250,000 tons of needle coke were used in the United States. 

FIGURE 4. Electrochemical reactor composed of a 2 cm3 capacity filter funnel and (A) stainless steel wire, (B, G) stainless steel needles for N2 entry and exit ports, (C) rubber septum, (D) lead foil cathode, (F) fine porosity glass filter, (H) plug of silicone glue and (I) silver wire anode. (Taken from Reference 176.)... 

Most petroleum coke is used for fuel, but some premium delayed coke known as needle coke is used to make anodes for the aluminum industry. That coke is first calcined to less than 0.5 percent volatiles at 1300 to 1400°C before it is used to make anodes. 

LMI sources with needle emitters operate in essentially the same way as field ionization or field desorption sources. The filament is resistively heated to melt the metal film and/or promote its flow to the tip of the emitter. Typically, the emitter or anode is positively biased 3-5 kV with respect to its counter electrode, the cathode the actual operating voltage is determined... 

S-shaped current potential curves emerge when a surface phase transition of an organic adsorbate is coupled with a faradaic reaction of some electroactive species. As a representative of such a system, the periodate reduction on Au(lll) single crystal electrodes in the presence of camphor was studied [160], Camphor adsorbed on Au(lll) electrodes exhibits two first-order phase transitions upon variation of the electrode potential [161]. In a cyclic voltammogram, the phase transition manifests itself in a pair of needle-like peaks (Fig. 28 (A)). Between the peak pairs, a condensed, well-ordered camphor film exists. At more negative potentials, the camphor coverage is low, while the state of the adsorbate at positive potentials beyond the second phase transition is not yet known. The small hystereses between the respective anodic and cathodic peaks are caused by the finite nucleation rate of the respective thermodynamically stable phase. 

The arc is ignited by means of an ignition needle which carries auxiliary anode H at first this is electromagnetically drawn into the mercury-filled dish then the contact is interrupted which gives rise to an arc which spreads quickly to anodes A. The necessary vacuum in the tubes, some 0.001 millimeters of mercury column (apart from the partial pressure of mercury vapour) is maintained by a diffusion vacuum pump compounded with an oil type rotary vacuum pump. 

A,. A. — Anodes (six). K —Cathode, II — Needle Igniter, C — Condensation cylinder, M — Electromagnetic breaking off of the ignition needle. 

Cobaltic Sulphate, Co2(S04)3.18H20, is obtained by electrolysis of cobaltous sulphate in a platinum dish, which serves as anode, the cathode consisting of a platinum wire immersed in a porous cell containing dilute sulphuric acid. The salt is deposited as blue silky needles round the anode. It is soluble in water, yielding an unstable blue solution which evolves oxygen, the salt being reduced to cobaltous sulphate. Upon exposure to air the crystals gradually decompose. In contact with hydrochloric acid, chlorine is evolved.3... 

Lead Dichromate, PbCr.20, containing 2 molecules of water of crystallisation, was described by Preis and Rayman, but its existence was subsequently denied. When a very concentrated solution of chromic acid (130 grams CrOg per 100 c.c.) is electrolysed with a lead anode, a solution is obtained which evolves oxygen when kept, and deposits reddish-brown needles of lead dichromate, PbCr O,. From the volume of oxygen evolved it appears that plumbic dichromate is formed and decomposes thus ... 

Field emission from a heteroepitaxial undoped (lOO)-oriented diamond film of 20-[rm thickness deposited on Ir(lOO) substrate was investigated in Ref [441] using a W needle as an anode. As compared with a polycrystalline diamond film also deposited on Ir(lOO), the heteroepitaxial film emitted electrons at lower voltage, roughly 1/3 of the voltage needed for the polycrystalline film. The emission was uniform over the entire area of 3 mm in diameter. The threshold voltage when the emission current was 10 " A was estimated to be 40 V/pm, which was fairly high, because the film surface was flat and the film was thick. 

In the second approach, the required localization of metal dissolution is achieved by other means. Some of them were considered in the previous sections. Here, TEs of several types are used [92-97] (1) An electrode with the shape and dimensions corresponding to the required cavity in the WP (2) a TE in the form of a wire or needle, which penetrates into the WP at the expense of its local anodic dissolution and moves according to a certain program, in order to obtain a given contour and (3) a high-speed jet beam of electrolyte from a micronozzle. 

A mixture of acryrlonitrile (24.8 g) and aqueous solution of 2N K2HPO4 (145 ml) was electrolyzed (0.5 A, 7 h) at 22°C in a divided cell with a bismuth cathode and a platinum anode. During electrolysis, 4.81 g of the anode was consumed. The organic layer of the solution in the anode compartment was separated and cooled to — 10°C, giving tris(2-cyanoethyl)bismuthine as white needles (8.22 g). The yields based on the current and electrode were 50 and 97%, respectively [74EL(10)1424],... 

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