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Determination of nanoscale titanium oxide thin film phase composition using X-ray photoelectron spectroscopy valence band analysis
摘要： The phase compositions of nanoscale thick titania films on the titanium were determined using X-ray photoelectron spectroscopy valence band analysis for the first time, by deconvoluting the two-peak structure of valence band into five peaks and analysing the relative peak area. The titania films of thickness varying from about 2 nm to 8 μm were obtained by the air oxidation of commercially pure titanium at different temperatures. The titania films formed on titanium for oxidizing temperatures up to 200 °C were amorphous, with thickness < 10 nm. The sub-stoichiometric oxides present at the TiO2-Ti interface were composed of Ti3+, Ti2+ and Ti1+ states when the film of thickness was < 10 nm. At 300 °C, when the titania film thickness was < 20 nm, it was fully converted to rutile phase and remained stable up to 1000 °C. A broadening of full-width half-maxima of the core level peaks for the titania layers was attributed to the presence of surface hydroxyl group and stress gradient within the oxide layer. The absence of metastable anatase phase in the titania layers at lower temperatures was attributed to the presence of high stresses within the oxide layers owing to their nanoscale thickness.
关键词： X-ray Photoelectron Spectroscopy,Thin film,Valence band,Surface phase composition,Titania,Titanium
更新于2025-11-21 11:24:58
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Investigation of the Phase Composition and Morphology of Silicon Structures by Using the Raman Spectroscopy to Determine the Parameter of Crystallinity
摘要： This work aims to investigate the dependence of the phase composition of thin films of microcrystalline silicon deposition on process parameters. The films of microcrystalline silicon were obtained by plasma-chemical deposition method (PECVD). Phase composition and correlation between degree of crystallinity and structure of the obtained layers were analyzed by Raman Spectroscopy. The results show that the control of several technical parameters, e.g. pressure, discharge power and monosilane flow, allows to reach the crystallinity parameter in the range 50-70 %. Based on the conducted experiments, the recommendations for the control of the crystallinity parameter, which are planned to be implemented when working with silicon-based porous structures, were proposed.
关键词： Morphology,Semiconductors,Silicon,Por-silicon,Phase composition,Raman spectroscopy,Raman Crystallinity
更新于2025-09-23 15:23:52
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Excellent electrostrictive coefficient in bismuth sodium titanate-based ceramics via regulating degree of diffuseness and phase composition
摘要： Herein, the strain (S) with low hysteresis can be achieved in [Bi0.5(Na0.72K0.18Li0.10)0.5]0.995Sr0.005(Ti0.995Ta0.005)O3-BaZrO3-NaNbO3 ceramics by an electrostrictive effect, and an excellent electrostrictive coefficient (Q33) of ～0.037 m4/C2 can be obtained under an electric field of 60 kV/cm. The enhancement of the degree of diffuseness regulated by phase compositions can effectively promote the electrostrictive response and increase the Q33 value. A higher ratio of P4bm and a larger Ps in P4bm guarantee the good linear relationship between S and P2 (P represents polarization), where a larger Ps (P4bm) can effectively restrict the expression of ferroelectric state with the increase of electric fields (E). Consequently, high Q33 values (0.033–0.037 m4/C2) are nearly independent of the applied electric fields. Although the strain from the electrostrictive effect is not tremendous, the good linear relationship between S and P2 is meaningful to the accurate displacement control in displacement actuators.
关键词： phase composition,degree of diffuseness,electrostrictive coefficient,bismuth sodium titanate-based ceramics
更新于2025-09-23 15:19:57
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Iron and the other metal species as phase-composition controllers the photocatalytic activity of TiO2 materials
摘要： The goal of the work is to verify which properties of TiO2-based materials, influenced by small amounts of Fe, Co, Ga, Bi, W, Mo, V and Ni species used as modifiers, play the predominant role in changing the photoactivity of TiO2. Two groups of materials were studied: TiO2 synthesized in the presence of nanocrystalline metal oxide and dissolved metal ions (cations or oxyanions). Sols were calcined at 450, 600 or 900°C. Physicochemical properties of the materials were characterized by XRD, DRS, SEM, EPR, porosimetry and photocurrent measurements. The most detailed studies were focused on modifications by iron species. TiO2 doping was achieved for both Fe3+ and Fe2O3 modifiers after calcination at temperatures equal to or higher than 450 and 900°C, respectively. Morphology of the materials (phase composition, specific surface area, etc.) were influenced by iron species even if they were not introduced into the crystal lattice of TiO2. Comparison of activity of photocatalysts and elucidation of the role of various reactive oxygen species were based on photooxidation tests involving Azure B and terephthalic acid. In general, iron species improved photocatalytic activity, nevertheless, doping of the materials appeared detrimental. A particular improvement of the activity was achieved for composites with low iron contents (ca. 0.01%mol Fe:Ti). The studies revealed, that beside the widely discussed mechanisms (photo-Fenton processes, charge separation, photosensitization, etc.) iron species can indirectly influence the photocatalytic activity of TiO2 acting as phase-composition controllers (PCC) during the synthesis of this oxide, which determine morphology of the resulting photocatalyst. To support this hypothesis, several sets of other TiO2 materials were modified with Co, Ga, Bi, W, Mo, V and Ni species. We show, that the use of these modifiers in small amounts can influence indirectly the activity of photocatalysts regardless to the type of modifier. Therefore different photoactivity of the tested materials should be attributed rather to these modifier-induced structural and electronic changes of the photocatalysts than to any other function of dopants, including photosensitization, enhanced charge separation, catalytic activity, at which most of studies are focused.
关键词： phase composition,photocatalysis,synthesis of photocatalysts,modified titanium dioxide
更新于2025-09-19 17:15:36
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Study of the phase composition and tribological properties of carbon tool steels after laser surface hardening by quasi - CW fiber laser
摘要： The paper contains the investigation results on the structure and phase composition of the laser radiation area (LRA) of the U8 and U10 steels over its entire thickness. In the present study, the laser surface hardening of both U8 (ASTM - W1-7) and U10 (ASTM - W1-9) steels in the air was performed by exploiting a quasi - CW fiber laser with a 130 W power and 3 mm/s processing speed. The phase composition of the oxide layer formed as a result of laser treatment (LT) in air, as well as the structure of the oxide-metal interface on the surface of U8 (ASTM–W1-7) and U10 (ASTM–W1-9) carbon tool steels were studied by X-ray photoelectron spectroscopy (XPS). It was established that the thickness of the completely oxidized surface layers for U8 and U10 steels is 38.7 nm and 99 nm, respectively. The composition of the oxides of the steel surface after LT was determined. The presence of a wüstite-based film on U8 steel evidences the low wear properties of the LRA surface, while the thicker oxide layer of the modified U10 steel which contains Fe2O3 and Fe3O4 oxides with better strength properties, on the contrary, provides U10 steel surface with higher wear resistance. It was found that the wear rate of U10 steel modified surface decreases by more than two times, while the given value for U8 steel reduces no more than 17%. The paper reports the metallographic examination of the LRA structure. It was shown that the wear-resistant structural components that appeared after laser treatment lead to an increase in the deformation properties of steels. The maximum microhardness value of the LRA is 710 HV0.1 for U8 steel and 750 HV0.1for U10 steel.
关键词： Laser radiation,Oxidized surface layers,X-ray photoelectron spectroscopy,Phase composition,Surface finishing treatment,Elemental composition
更新于2025-09-19 17:13:59
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Analysis of the effect of the thermomechanical processing on the laser weld joint of aluminum alloys of Al-Mg-Li and Al-Cu-Li
摘要： The paper presents the experimental investigation of the laser welding of high-strength aluminum-lithium alloys of Al-Cu-Li and Al-Mg-Li system followed by the thermal processing, aimed to the production of a high-strength weld joint. It is founded that the thermal processing (quenching, artificial ageing) of the welded joint increases its strength, however the variation of the microstructure and phase composition is different for the two systems of the alloys. The thermal processing permits getting the tensile strength of the welded sample of 0.9 of the basic alloy strength for Al-Cu-Li and 0.95 for Al-Mg-Li.
关键词： microstructure,thermal processing,CO2 laser,laser welding,phase composition
更新于2025-09-12 10:27:22
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Effect of BaO on the phase composition and properties of aluminates for Ba-W cathodes
摘要： In this study, we prepared (4.8+x)BaO·CaO·2Al2O3(0≤x≤1.6) aluminates by calcining the precursors under static air at 1500 °C for 120 min. The precursor powders were prepared using a liquid phase co-precipitation method. The effects of the molar content of BaO on the phase composition (before and after melting), melting properties, environmental stability, evaporation, and emission properties of the aluminates was investigated systematically The results showed that the phase of the aluminates completely transformed from Ba5CaAl4O12 to Ba3CaAl2O7 with an increase in the BaO content. After melting, the phase changed from Ba5CaAl4O12 to a mixed phase of Ba5CaAl4O12 and Ba3CaAl2O7. In the high-temperature molten state, the aluminates were in the ionic state, which generated a relatively low-energy Ba5CaAl4O12 phase during cooling crystallization. With every 0.4 mol increase in the BaO content, the initial melting temperature of the aluminates decreased by 10–20 ℃, while the environmental stability deteriorated gradually. When the aluminates reacted with H2O and CO2 in the air, the original phase still existed and the characteristic peaks gradually broadened, but with the formation of Ca(OH)2, CaCO3, and BaCO3. At 1050 °C, with an increase in the BaO content, the evaporation rate of the Ba-W cathodes increased and the emission current density first increased and then decreased. The main components of the Ba-W cathode evaporation were Ba and BaO. At n(BaO):n(CaO):n(Al2O3)=6:1:2, the Ba-W cathode showed the best emission performance, and its pulse emission current density at 1050 °C was as high as 35.31 A/cm2.
关键词： Ba-W cathode,Emission current,BaO content,Phase composition,Evaporation rate
更新于2025-09-09 09:28:46