Papers by Keyword: Nitridation

Abstract: The article proposes possible increase of durability of tool steel X210Cr12 as regards working conditions under consideration of abrasive wear. From such steel tools are made for pressing wooden briquettes and saw dust waste. In practical environment a condition is held that if a material should work in abrasive wear conditions, it should have high hardness and should contain carbides in the structure. The proposed paper deals with the heat and chemical-heat treatment (nitriding) of tool steel which is working in hard abrasive wear conditions. From the obtained results it is not easy to conclude a definitive conclusion or to set the boundaries between the factors that are responsible for wear resistance. It is shown that the chemical-heat treatment can in the last step of the heat treatment lead to an increase or even to a decrease in the abrasive wear resistance of the material. The aim of the paper is to set a proper heat treatment of materials used for pressing in abrasion wear conditions.

Abstract: The fabrication of ultra thin silicon nitride (SiN_X) layer (< 2 nm) on amorphous silicon (a-Si) in-situ hot-wire CVD by decomposing ammonia (NH₃) gas is reported. Approximately 1.5 nm thin SiN_X is formed by nitridation of 40 nm thick a-Si for 10 min at substrate temperature of 250 °C. The amorphous phase of SiN_X formed on a-Si and a-Si layer deposited on c-Si wafer is identified by Raman spectroscopy. The formation of ultra thin SiN_X by nitridation of a-Si at 250 °C is confirmed by X-ray photoelectron spectroscopy (XPS) depth profile measurement of SiN_X/a-Si structured film. The report indicates that the HWCVD method can be used for fabricating superlattice structures consisting of ultra thin SiN_X layers (< 2 nm).

Abstract: We have studied gate oxide processes for SiC trench MOSFETs. It is demonstrated that nitridation of gate oxide is effective to suppress the variation of channel mobility depending on channel plane orientation and substrate off-angles. In addition, improved channel mobility has been obtained by the combined process of NH₃ and N₂O POA.

Abstract: In this article, GaN thin films were successfully grown on p-type silicon (p-Si) substrates with orientation (100) through spin coating method followed by nitridation in ammonia ambient at various temperatures (750 °C, 850 °C, and 950 °C). The morphology of the GaN thin films were performed by using field-emission scanning electron microscopy. The results showed that the grain size increases with increasing nitridation temperature from 750 °C to 950 °C. Optical analysis of the GaN thin films was performed using Fourier transform infrared spectroscopy. It was confirmed from the results that the reflectance intensity of the transverse optical and longitudinal optical phonon modes of wurtzite GaN increases with increasing nitridation temperature. All the measured results show that nitridation temperature plays a very important role in improving the quality of the GaN thin films. Finally, the results revealed that the 950 °C was the optimal growth nitridation temperature for synthesizing GaN thin film.

Abstract: In the present study, we have successfully grown Si-doped AlN developed by solution growth technique using Ga-Al melt as a solvent under nitrogen atmosphere at 1300 °C. Si doping was introduced to the Ga-Al melt by adding pure Si metal. To allow homoepitaxial growth during solution growth experiment, sapphire substrate were nitrided with precise control to produce hiqh quality single crystalline AlN films with low dislocation density. With the help of AlN film template from above methods, we have successfully grown Si-doped AlN single crystalline layer with a flat surface and almost free from cracks. The full width at half maximum (FWHM) of x-ray rocking curve values for (0002) and (10-12) diffraction from the Si-doped AlN film were 43,2 and 594 arcsec, respectively.

Abstract: The reduction of Malaysia Ilmenite (FeTiO₃) with coal by carbothermal reduction under N₂ atmosphere was studied. Characterization of raw materials was done by XRD, XRF, Optical Microscopy (OM) and SEM analysis. Isothermal experiments were carried out using the pellets in a horizontal tube reactor with continuously flowing gas. From the experiments, 0-10 wt. % of FeCl₃ was added in the ilmenite-coal mixtures before reduction. The mixture was reduced at 1100°C for 60, 120 and 180 minutes. The addition of FeCl₃ acted as a catalyst and increased the rate of reduction. The microstructures of the reduced sample were porous with the addition of FeCl₃. Furthermore, defects were observed due to increase release of Cl₂ and CO during reduction. FeCl₃ acted as catalyst in the gasification of coal by the Boudouard reaction. SEM analysis indicates that the microstructure of the particles was coarsened due to the addition of catalyst. Besides that, there was less agglomeration of metallic iron particles at higher addition of FeCl₃. The effect of FeCl₃ on the morphology iron was the nucleation of microscopic iron rich zones in the reduced sample. Keywords: Carbothermal Reduction, Iron Chloride, Malaysian Ilmenite, Nitridation, Titanium Oxycarbonitride.

Abstract: Statistical design analysis (factorial design) was utilized to verify the significance and the interaction between the studied factors include temperature, reduction time and catalyst amount. Carbothermal reduction of iron ore sample was carried out at temperature between 1000°C to 1200°C. The effects of operating parameters studied were extent of reduction (X), carbon consumed (C_consumed ) and nitridation (X_N). Temperature was the most influential parameter that showed strong interaction with the operating parameters, meanwhile, reduction time and catalyst have showed the contrary results and had a very low percentage of contribution. The results of the experimental design showed that the extent of reduction reached up to 93% at 1200°C using 10 wt. % catalysts after 180 minutes reduction. The use of 0-10 wt % catalyst at 1200°C for 180 min reduction significantly affect the X but did not for C_consumed and X_N.Keywords: Carbothermal Reduction, Factorial Design, Malaysian Ilmenite, Nitridation.

Abstract: In situ NH₃ plasma nitridation was utilized to passivate InP surface, HfLaO_x film was grown by plasma enhanced atom layer deposition method, and the HfLaO_x film remain amorphous after 500°C annealing. High-resolution transmission electron microscopy (HRTEM) images showed that in situ NH₃ plasma nitridation process make the boundary between InP and HfLaO_x smooth and sharp, and could suppress the formation of the interfacial layer. X-ray photoelectron spectra (XPS) results indicated In-N and P-N bonds were formed on the nitride InP surface. The electrical measurements indicated in situ NH₃ plasma nitridation process reduced the hysteresis improved capacitance density and to 7 mV, a sharp transition from depletion to accumulation was observed, the interfacial density states (D_it) of the sample with nitridation was 1.67×10¹² cm² eV¹, and the equivalent oxide thickness (EOT) was 0.6 nm. The leakage current was 1.5 mA/cm² at V_g-V_fb=1V.

Abstract: The SiO₂ layer was deposited on the 4H-SiC Si face by the thermal decomposition of tetraethylorthosilicate(TEOS) in N₂ atmosphere to from MIS diodes. The post deposition annealing was effective to improve the interface properties. The interface state density of the deposited SiO₂/SiC MIS structure was estimated to be the order of 10¹¹ cm^-2eV^-1 by Terman method. The direct nitridation of SiC surface prior to the deposition of the SiO₂ layer was effective to reduce the interface state density.

Abstract: Based on aluminum powder, Silicon powder, activated alumina and flake graphite as the main starting materials, SiAlON-Graphite composites were produced in N₂ atmosphere. The influence of firing temperature and atmosphere on Si-Al-O-C-N system was investigated. It is proposed that the introduction of graphite produces a certain CO partial pressure and affects the nitridation of metal silicon, therefore reducing the mass change. In addition, large amount of 15R are formed through carbothermic reduction. CO hinders the growth of β-SiAlON. Z value of β-SiAlON in sample C with graphite is less than sample S without graphite.