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Preparation of α‐Si <sub/>3</sub> N <sub/>4</sub> by direct nitridation using the polysilicon waste by diamond wire cutting
摘要： With the rapid development of the semiconductor industry and solar photovoltaic industry, a large number of polysilicon wastes from diamond wire cutting are accumulated, which not only pollute the environment, but also cause safety problems due to the ultrafine particle size and high reactivity. The diamond wire cutting polysilicon waste was used to prepare α-Si3N4 by direct nitridation method. This method could not only fully recycle the waste and reduce environmental pollution, but also reduce the production cost of α-Si3N4. Furthermore, the effects of FeCl3, NaCl and metal Cu on the nitridation of polysilicon waste are investigated in detail, respectively. It is found that FeCl3 and NaCl are not ideal additives for the preparation of α-Si3N4. However, α-Si3N4 dominated Si3N4 can be obtained via adding 5 wt. % Cu after nitridation at 1250 oC for 8 h, and the relative content of α-Si3N4 reaches 92.37 %.
关键词： silicon nitride,crystal growth,nitridation,catalysts/catalysis,powders
更新于2025-11-14 14:48:53
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Effect of NaN<sub>3</sub> Addition Content on NaCl-NaF Medium Nitridation Synthesis β-Sialon Powders
摘要： β-Sialon powders were synthesized via salt-assisted nitridation synthesis from Al, Si, SiO2 powders and molten salt medium (NaCl and NaF) with the addition of different content of NaN3 at different temperature for 3 h. NaN3 were employed as auxiliary nitrogen source which effectively provide sufficient nitrogen. The results indicated that the growth of β-Sialon powders had better effect when the NaN3 was added. And the β-Sialon powders grew more completely and the morphology of β-Sialon powders showed the rod-like crystal with hexagonal smooth tips instead of conical tips. In addition, the products displayed different sizes when the content of NaN3 was changed. These results of this work suggested that β-Sialon could be synthesized with specific morphology by adding different content of NaN3.
关键词： β-Sialon,synthesis,Morphology,nitridation,salt-assisted
更新于2025-09-23 15:22:29
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Mechanisms of GaN quantum dot formation during nitridation of Ga droplets
摘要： We have examined the formation mechanisms of GaN quantum dots (QDs) via annealing of Ga droplets in a nitrogen ?ux. We consider the temperature- and substrate-dependence of the size distributions of droplets and QDs, as well as the relative roles of Ga/N diffusivity and GaN nucleation rates on QD formation. We report on two competing mechanisms mediated by Ga surface diffusion, namely, QD formation at or away from pre-existing Ga droplets. We discuss the relative roles of nucleation- and coarsening-dominant growth, as well as zincblende vs wurtzite polytype selection, on various substrates. These insights provide an opportunity for tailoring QD size distributions and polytype selection for a wide range of III-N semiconductor QDs.
关键词： polytype selection,surface diffusion,GaN quantum dots,nitridation,Ga droplets
更新于2025-09-23 15:19:57
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Two-Stage Plasma-Thermal Nitridation Processes for the Production of Aluminum Nitride Powders from Aluminum Powders
摘要： The synthesis of aluminum nitride (AlN) powders is traditionally done via the thermal nitridation process, in which the reaction temperature reaches as high as 960 ?C, with more than several hours of reaction time. Moreover, the occurrence of agglomeration in melting Al particles results in poor AlN quality and a low ef?ciency of nitridation. In this study, an atmosphere-pressure microwave-plasma preceded the pre-synthesis process. This process operates at 550 ?C for 2–10 min with the addition of NH4Cl (Al: NH4Cl = 1:1) for generating a hard AlN shell to avoid the ?ow and aggregation of the melting Al metals. Then, the mass production of AlN powders by the thermal nitridation process can be carried out by rapidly elevating the reaction temperature (heating rate of 15 ?C/min) until 1050 ?C is reached. X-Ray Diffractometer (XRD) crystal analysis shows that without the peak, Al metals can be observed by synthesizing AlN via plasma nitridation (at 550 ?C for 2 min, Al: NH4Cl = 1:1), followed by thermal nitridation (at 950 ?C for 1 h). Moreover, SEM images show that well-dispersed AlN powders without agglomeration were produced. Additionally, the particle size of the produced AlN powder (usually < 1 μm) tends to be reduced from 2–5 μm (Al powders), resulting in a more ef?cient synthesizing process (lower reaction temperature, shorter reaction time) for mass production.
关键词： agglomeration,aluminum nitride,thermal nitridation,plasma nitridation,pre-synthesis
更新于2025-09-19 17:15:36
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Zinc doping of Ga-rich GaN powders obtained by nitridation of the Ga-Zn liquid metallic solution
摘要： Zn-doped GaN powders were obtained by supersaturation of the Ga-Zn liquid metallic solution at 440 °C, followed by a nitridation process in ammonia flow at 1000 °C for two hours. Photoluminescence spectrum measured at room temperature for Zn-doped GaN powders, showed an emission band with a maximum energy of 2.89 eV (429 nm), which might be related to the excitons binding to the Zn acceptors. The Raman spectra agree with the incorporation of Zn as dopant into GaN powders, demonstrating a shoulder at 651.89 cm?1 and a slight shift (1.55 cm?1) to low frequency of the vibration mode A1(TO) with respect to undoped GaN powders. The Raman spectra showed a separation between the E1(TO) and E2(High) modes, confirming that Ga-rich GaN was obtained. X-ray diffraction patterns did not show any shift of the peaks of the Zn-doped GaN with respect to the undoped GaN powders. Scanning electron microscopy micrographs demonstrated that the surface morphology of the Zn-doped GaN powders was composed of platelets of irregular structure with an average length of 2.80 mm. Finally, x-ray photo-electron spectroscopy spectra did not show an important elemental contribution of zinc due to the small amount of the dopant element (1.05 mol%).
关键词： Diffusion,Nitridation,Doped,Liquid metallic solution
更新于2025-09-19 17:15:36
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Influence of the GaAs crystals diffusion in the shift towards low energies in the photoluminescence emission band of the GaN/GaNbuffer/GaAs structure
摘要： GaN buffer layers were obtained by nitridation of GaAs substrates and GaN upper layers were growth by MOCVD to make the GaN/GaNbuffer/GaAs structure. It was observed GaAs crystals diffusion in GaN upper layer from buffer layer, when the growth temperature reach 900 °C. Photoluminescence spectrum showed the decrease in the maximum energy from 3.2 eV (381 nm) to 2.9 eV (414 nm) with contributions in 2.6 eV (462 nm) and 2.5 eV (487 nm) related to GaAs crystals diffused in GaN upper layer and hydrogen impurities respectively, which induce extended defects in the lattice. It is considered that the temperature and the growth method of GaN buffer layer, influences the photoluminescence emission of the GaN upper layer, shifting its maximum energy to low energies. X-ray diffraction patterns and transmission electron microscopy micrographs support the presence of GaAs in the GaN upper layer of the GaN/GaNbuffer/GaAs structure obtained at 900 °C. The decrease of GaAs crystal diffusion in the GaN upper layer is observed, when its growth temperature increases from 900 to 1000 °C, with a maximum energy of 3.2 eV (381 nm).
关键词： MOCVD,Buffer layer,Diffusion,Nitridation
更新于2025-09-19 17:15:36
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Diffusion of Oxygen and Nitrogen into Titanium under Laser Irradiation in Air
摘要： This paper examines the dynamic interactions between pure titanium and ambient air under transient laser processing conditions. The microstructures and composition distributions of the reaction products on and within the titanium samples are reported, which lead to the estimation of high-temperature diffusion coefficients for nitrogen and oxygen into the titanium substrate. In-situ synchrotron X-ray diffraction testing is conducted to reveal the high temperature reaction steps between titanium and air. The formation mechanisms of both titanium nitrides and titanium oxides are discussed.
关键词： titanium oxidation,titanium nitridation,synchrotron X-ray diffraction.,in-situ phase transformation,laser irradiation
更新于2025-09-12 10:27:22
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Chemical and structural heterogeneities in Nd-doped oxynitride phosphate laser glasses
摘要： The application of oxynitride glasses in optics has been limited due the issues inherent in their preparation that result in bubbles, metallic inclusions or opacity. Although the synthesis of oxynitride phosphates is easier than in silicates, due to their lower melt viscosity, the remaining water in the form of OH causes, for instance, the neodymium luminescence to be negatively affected. We report on the preparation of oxynitride Nd phosphate glasses that are submitted first to a dehydroxylation, so that their structure and properties can be studied as a function of the nitrogen content taking a completely homogeneous OH-free glass as the starting point of each synthesis. Raman and Brillouin Spectroscopy confirmed the segregation in oxide and N-enriched regions, and NMR of the glasses has been used to calculate the O/P ratio from the distribution of P(O,N)4 groups. The difference between this and the experimental one obtained from the elemental analyses confirms the segregation in oxide and oxynitride regions that is produced during the ammonolysis of the phosphate glass. The oxynitride glass network could thus be considered a non-homogeneous mixture of the oxide and the nitrided phases that are segregated due to the non-randomness of the nitridation reaction.
关键词： Nitridation,Phosphate glasses,Laser glasses,Oxynitride glasses,Water
更新于2025-09-12 10:27:22
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Bandgap trimming and optical properties of Si <sub/>3</sub> N <sub/>4</sub> :Al microbelt phosphors for warm white light-emitting diodes
摘要： Si3N4:Al microbelts with tunable bandgap energy and resultant yellow-orange phosphors are prepared through a facile direct nitridation method. The bandgap energy of Si3N4:Al microbelts has been gradually trimmed from 2.58 eV to 2.67, 2.74 and 2.85 eV by regulating the Si/Al molar ratio from 1000 : 1 to 50 : 1. Si3N4:Al:Eu phosphors display a wide emission ranging from 500 to 800 nm when excited by a 450 nm blue LED light source. The crystal structure of Si3N4:Al microbelts is of the α-Si3N4 phase as characterized by X-ray diffraction, high-resolution TEM and crystal models. Si3N4:Al microbelts grow along the (012) stacking direction in a low doping concentration case and grow along the (011) stacking direction in a high doping concentration case. Theoretical calculation results show that Al prefers to occupy the low energy interstitial sites in the (012) plane. There are more substitutional sites in the (011) plane occupied by Al in the high doping concentration case with increasing the bandgap energy of Si3N4:Al. Warm white light emission has been achieved by precoating Si3N4:Al:Eu phosphors onto a blue LED chip, whose correlated color temperature (CCT) can be tailored from 3000 K to 6500 K by altering the phosphor amount, indicating a promising potential application of Si3N4:Al:Eu phosphors in warm white LEDs.
关键词： direct nitridation method,Si3N4:Al microbelts,tunable bandgap energy,yellow-orange phosphors,warm white LEDs
更新于2025-09-12 10:27:22
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Titanium and nitrogen interactions under laser additive manufacturing conditions
摘要： To understand how to make bulk titanium parts or coatings with desired levels of titanium nitrides, this paper investigates the dynamic interactions between titanium and nitrogen under representative laser-based additive manufacturing (AM) conditions. Under a set of gas environments containing different concentrations of nitrogen, the titanium and nitrogen reaction products—formed under typical Selective Laser Melting (SLM) and Laser Engineered Net Shaping (LENS) AM scanning conditions—are examined for compositions, phases, and microstructures. In-situ synchrotron X-ray diffraction (SXRD) test is performed to reveal the high temperature reaction steps between titanium and nitrogen.
关键词： Synchrotron X-ray diffraction,in-situ phase transformation,Titanium nitridation,Laser melting
更新于2025-09-11 14:15:04