Reverse biased nanocrystalline graphite (NCG)/p-Si schottky junction for methane gas sensor

An investigation on the effect of the reverse biased operation of NCG/p-Si Schottky contact during methane gas exposure at room temperature has been presented. The experimental results show the larger current shift at the reverse bias operation, compared to the forward bias by exposing to methane gas. This can be attributed to the adsorption of methane gas into the metal surface layer and produces a negative charge at the junction, thus reduces the barrier height of the device. The reverse barrier height was calculated under the reverse bias condition, demonstrated the value decreased from 0.58-0.53eV towards a higher concentration of methane gas. The Schottky junction also affected by the increase in a free carrier when exposure to the reducing gas such as methane. Raman spectra are reported to be detected at G, D and 2D band with the grain size 1.88nm to exhibit single crystallite graphite properties. The results correlate well with the 3D AFM scans reveal the RMS surface roughness of 1.1 to 2.8nm.

Regarding a technology of Sulphur removal in acidic induction furnaces

Sulphurremoval is a rather complicated metallurgical task, which require implementation of new energy-saving technologies, including metal desulphurization in induction furnaces. Results of analysis of different methods of metal desulphurization in the acidic induction furnaces. A technology of hot metal refining with Sulphurremoval by basic slags by extraction mechanism in the acidic induction furnaces proposed, tested and implemented at several plants. The essence of the xtraction mechanism applied to desulphurization method is as follows: particles of calcic slag involved by electromagnetic flows deep into an induction furnace. The surface layer of slag particles deoxidizes by carbon of the metal and silicon, resulting in the Sulphursolubility increases sharply due to its absorption by the metal surface layer of slag particles. Next, the metal flows deliver to the surface the slag particles saturated by Sulphur, the surface contacted with the furnace atmosphere, where the surface layer of slag particles is oxidized by oxygen of the atmosphere. It results in the Sulphursolubility decreasing sharply and after precipitating out of the slag; it oxidizes by oxygen to SO2 and removes into the furnace atmosphere. The process repeats multiply. The mechanism of theSulphur removal in the induction furnaces with acidic lining was studied at OJSC ZSMK foundry shop using IChT-10M furnaces when melting hot metal for melt bases and warmth-keeping jackets. To increase the proposed technology efficiency, the influence of different technological parameters on the rate and degree of metal desulphurization in the acidic induction furnaces of industrial frequency studied. Results of the study allowed to make a conclusion that induction furnaces, traditionally used for smelting of burden materials, convert into active refining melting facilities.

Hardness Optimization Based on Nitriding Time and Gas Pressure in the Plasma Nitriding of Aluminium Alloys

Plasma nitriding has attracted much interest to improve the hardness of aluminium alloys. However, the contradictive properties can be produced on the metal surface due to the saturated condition of the diffused nitrogen atom in the metal surface layer. The objective of this work was to investigate the effect of nitriding time and gas pressure to improve the hardness of aluminium using plasma nitriding. The nitriding processes were conducted in a DC glow discharge with nitrogen gas flowing inside the vacuum chamber. Firstly, the sample was nitrided using a fixed gas pressure of 1.2 mbar with the varied nitriding times of 3, 4, 5 and 6 hours. The optimum time producing the highest hardness of the surface was then used in the next nitriding process with varied gas pressure of 1.2, 1.4, 1.6 and 1.8 mbar (1 bar = 105 Pa). The optimum gas pressure producing the highest hardness was then used again in the last nitriding process using varied nitriding time of 3, 4, 5 and 6 hours. The result showed that the highest hardness was achieved using the gas pressure and nitriding time of 1.6 mbar and 4 hours, respectively. The formed AlN phase on the aluminium surface was identified by XRD, whereas the surface morphology was observed by SEM image. Compared to the untreated sample, the hardness of the treated samples was significantly high.

The Metal Surface Layer Mechanical Condition Transformation in Machining Processes

The metal surface layer mechanical condition transformation at the product life cycle stages key provisions are presented. The described approach feature is the hardened body effect consideration: the metal mechanical properties changing during it displacement through the deformation zone space. On the basis of the developed for surface plastic deformation process hardened elastic-plastic body model, the cumulative shear strain level, plasticity reserve exhaustion level and residual stress tensor components calculations are performed. It is established that the greatest residual compressive stresses are characteristic for the axial component, and the extremum can be located both on the workpiece surface and at some distance from it. The metal hardening influence on the residual stresses distribution is revealed. On the axial (largest) component example shown that the difference between the maximum values is almost 30%. The obtained result corresponds to the idea that the hardened metal having an increased yield strength allows a larger residual stresses presence.

Change of Void Volume of Steel Sheet Rough Layer after Deformation by Roll with Given Surface Roughness

New 3D metrology and new possibilities of modern measuring equipment allows observing in more details the process of metal surface layer deformation by rough surface of roll. The article covers the question of the change in the void volume of steel sheet rough layer at different section levels of rough layer by roll with different surface roughness.