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A 1.5 GHz passive third harmonic superconducting cavity was proposed to improve the beam quality and lifetime in the Shanghai Synchrotron Radiation Facility Phase-II beamline project. Lifetime improvement highly depends on the resonant frequency of the passive third harmonic superconducting cavity. It is important that the operating frequency of the cavity is within the design range and the cavity has reasonable mechanical stability. A simulation method for the multiphysics coupled analysis has been developed based on the ANSYS code. Multiphysics coupled simulations have been performed under different conditions, such as etching, evacuation, cooling, and preloading. Analyses of mechanical modes and structural stress have been executed. A possible stiffening ring method for the two-cell superconducting niobium cavity has been investigated. In this paper, we present a multiphysics coupled analysis of the third harmonic cavity using a finite element analysis code. The results of the analysis show that a reliable frequency for the cavity after electron beam welding is 1498.033 MHz, and the corresponding frequency of the pre-tuning goal is 1496.163 MHz. A naked cavity is a reasonable option based on structural stress and mechanical modal analyses. A frequency range of ± 500 kHz and limiting tolerable displacement of ± 0.35 mm are proposed for the design of the frequency tuner.

Nitrogenated tetrahedral amorphous carbon (N:ta-C) films prepared by the filtered cathodic vacuum arc technique were studied by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, spectroscopic ellipsometry, ultraviolet photoelectron spectroscopy and temperature dependent resistance measurement. As the nitrogen flow rate varies from 0 to 20 sccm, the nitrogen content in the deposited film increases from 0 to 4.6 at. %. Curve fitting of the C 1s and N 1s XPS spectra shows that the C–C sp3 fraction decreases with an increase in nitrogen content and that the nitrogen atoms are mainly bonded in sp2 C–N bonds. The pure ta-C film has a work function of 4.35 eV and the N:ta-C films have a value around 4.55 eV. With an increase in nitrogen flow rate, the intensity ratio of the D peak to the G peak, ID/IG increases monotonously from 0.44 to 1.25 and the G peak width decreases from 220 to 199 cm−1. The Tauc optical band gap decreases from 2.2 to 1.8 eV.

Nanocrystalline diamond films with different size were characterized by ultraviolet (UV) (244 nm) Raman spectroscopy. It was found that a diamond peak at 1333 cm −1 was enhanced, while the D and G peak of graphite as well as photoluminescence was suppressed, compared with that measured by visible (514.5 nm) Raman. With decreasing the particle size from 120 to 28 nm, the diamond peak shifts from 1332.8 to 1329.6 cm −1 , the line width of the peak becomes broader, the intensity ratio of diamond and G peak decreases. The down shift and broadening of the diamond peak depending on the particle size by UV Raman measurements are consistent with the phonon confinement model.

The field-emission properties of a Si–O bond-containing diamond-like nanocomposite (DLN) film were investigated as a function of annealing temperature (Ta). It was found that with increasing Ta the emission threshold voltage decreased gradually. After annealing at Ta=500 °C, the emission current decreased significantly. At Ta=700 °C, however, the field-emission properties of the DLN film improved greatly, the threshold field became very low (∼1.5 V/μm), and the emission current rather high (e.g., ∼2.3 μA/mm2 at an electric field of 22 V/μm). The structural variation of the film after annealing at different temperatures was monitored by ultraviolet Raman spectroscopy, spectroscopic ellipsometry, atomic-force microscopy, and electrical resistivity measurements. By using a three-step model: (i) electron injection from the substrate, (ii) electron transport through the film, and (iii) electron emission at the film surface, the annealing effect on field-emission properties of the DLN film were qualitatively in...

Diamond-like carbon (DLC) films have been deposited by a magnetically enhanced plasma (MEP) chemical vapor deposition (CVD) system. The properties and structures of DLC films deposited by MEP-CVD using various gases (methane, He/methane, Ne/methane, and Ar/methane) were studied. The mechanical properties in terms of hardness, Young’s modulus and stress, and optical properties in terms of optical band gap and refractive index were enhanced by adding inert gas in methane plasma. The magnitude of the effects on the properties for various inert gases was found as Ne, Ar, and He, on the surface roughness was found as Ar, Ne, and He. The Raman characteristic shows a dependence of the bias voltage and inert-gas/methane ratio, as well as the inert gases dilution. The Raman spectroscopy analysis indicates that the changes of properties of the DLC films are due to the structural changes, such as sp2 and sp3 content in the films prepared under various deposition conditions. The films deposited in Ne/methane show the lowest disordered (D) peak to graphitic (G) peak intensity ratio, the D and G peak positions; highest stress, hardness, Young’s modulus, optical band gap, and lowest reflective index. The films deposited in Ar/methane show the lowest surface roughness. This was proposed due to the optimum balance in the inert gas ionization potential and atomic mass.

Hydrogen-free amorphous carbon films were deposited at different deposition bais voltage on a single silicon wafer by a process known as Filtered Cathodic Vacuum Arc (FCVA). The influences of different deposition bias voltages on the microstructure and the properties of thin tetrahedral amorphous carbon (ta-C) films, such as surface roughness, film mass density and thickness, have been studied by means of the x-ray reflectivity technique (XRR) for the first time. The microstructure of these films deposited on silicon wafers was stimulated by a four-layer model consisting of a ta-C layer, a mixed ta-C:Si layer, Si-O layer and the silicon subtrate. The mixed ta-C:Si layer consisting of the mixture of ta-C and silicon simulates the carbon ion impinging / diffusion into the surface of the silicon substrate. The mass density and the roughness of the film are found to be dependent on the impinging ion bombardment energy. The mass density increases with increase in ion bombardment energy up to 100 eV. Beyond 100 eV, the mass density decreases with further increase in ion bombardment energy up to 100 eV. Beyond 100 EV, the mass density decreases with further increase in ion bombardment energy. The surface roughness decreases with increasing ion bambardment energy to a minimum value at 100 eV, after which it increases with further increase in ion bombardment energy. The thickness of the films obtained by XRR technique correlates well with the thickness measurement obtained by spectral reflectometry. The existence of the Si-O layer was verified by Auger depth profiling.

The structure of tetrahedral amorphous carbon (ta-C) films deposited by a filtered cathodic vacuum arc has been studied using micro-Raman spectroscopy in terms of substrate bias, nitrogen gas partial pressure (ta-C:N films) or aluminum content in a mixed aluminum/carbon target (ta-C:Al films) during deposition. The first-order Raman spectra generally show a broad feature overlaid by a disordered (D) peak and a graphitic (G) peak. The contribution of sp3 bonding to the Raman spectrum is not explicit, since the Raman phonon line is more sensitive to the sp2 carbon bonding due to its larger Raman scattering cross section. However by comparing the ratios of the intensities, the full widths at half maximum (FWHM), and the peak areas between the D and G peaks, the sp3 contribution may indirectly be reflected by the complex Raman features. The G peak position for the ta-C and ta-C:N films appears to not change significantly with the change of substrate bias voltage or N2 partial pressure, whereas the shift of the D peak is more appreciable. On the contrary, the G peak position for the ta-C:Al films shows a continuous decrease with increasing Al content. For the undoped ta-C films, the minimum intensity, area, and FWHM ratios between the D peak and the G peak are obtained at a bias around −100 V, which corresponds to the maximum sp3 content in the ta-C films. These ratios for the ta-C:N and ta-C:Al films, however, generally increase with increased N or Al content, which indicates the increase of sp2 bonded clusters.

The morphological properties of the tetrahedral amorphous carbon (ta-C) films deposited by the filtered cathodic vacuum arc (FCVA) technique have been studied over the carbon ion energy range 15 to 200 eV. All the films studied are very smooth with a roughness below 0.6 nm. The minimum roughness ( nm) occurs at the highest content. The lateral feature size increases with ion energy. There appear to be two different growth mechanisms before and after the peak content. The morphological result suggests an upper limit content of about 89% in the ta-C films deposited by FCVA technique.

Amorphous silicon-carbon films have been successfully deposited by the filtered cathodic vacuum arc technique. The silicon concentration in the films determined by x-ray photoelectron spectroscopy measurement varies from 2.4 to 55 at.%. The structural properties of the films were investigated by using atomic force microscopy, Raman spectroscopy, and x-ray diffraction. All of the films have smooth surface morphology with RMS roughness below 0.6 nm. Both Raman spectroscopy and x-ray diffraction show the existence of silicon carbide clusters in the films with silicon contents between 42 and 48 at.%. The G-peak position of the carbon cluster is shifted to very much lower values of the Raman shift with increasing silicon content. The silicon atoms predominantly substitute for the carbon atoms in the carbon cluster at low silicon content, and form amorphous silicon carbide clusters or amorphous silicon clusters at high silicon content.

The thermal degradation of cotton cellulose treated with chemical mixtures containing P and N was studied by thermal analysis, infrared spectroscopy, Char yield and limiting-oxygen-index (LOI). Our experiments demonstrated the following facts. The temperatures and activation energies of pyrolysis were lower for cotton cellulose treated with flame retardants than those for untreated samples and the values of Char yield and LOI were greater for treated cotton than those for untreated one.

Fabrication and characterization of nitrogenated tetrahedral amorphous carbon (ta-C:N) semiconductor/crystalline p-type silicon (p-Si) heterojunction structures are reported. The electron-hole pairs generated from both ta-C:N and Si depletion regions were observed from photoresponse measurements. The peaks are centered at about 540 and 1020 nm, which correspond to the optical absorption edge of ta-C:N and p-Si, respectively. The reverse current increased by three orders of magnitude when the structures were exposed to AM1 light. A photovoltaic effect was observed from ta-C:N and the values of short circuit current, open circuit voltage, and field factor obtained are 5.05 mA cm−2, 270 mV, and 0.2631, respectively.

Raman spectra of the internal,nodes of ND4+-ion in (ND4)(2)PbCl6 crystal have bees recorded in the temperature range of 5-300K. A new structural Phase transition was observed at 34K because of deuterium effect. Discontinuous behaviours of the internal,nodes of the ND4+-ion at this temperature show that the structural transition is one of first order.

Nitrogenated amorphous carbon (a-CNx) films were prepared by unbalanced magnetron sputtering (UBMS) at different N2∕Ar gas flow rate ratios and different bias voltages. The films were characterized using x-ray photoelectron spectroscopy, Raman scattering, nanoindenter, atomic force microscopy nanoscratch, and contact angle measurement. It was found that a negative bias of 150V is the optimal condition for the formation of sp3 bonded carbon atoms. As the N2∕Ar flow rate ratio changes from 0 to 0.47, the nitrogen to carbon ratio in deposited films increases from 0 to 0.22, and the sp3 fraction of carbon atoms decreases from 0.51 to 0.28. The pure carbon film has the highest sp3 faction of carbon atoms and therefore the highest hardness and the lowest scratching depth. Comparing to the films prepared by conventional magnetron sputtering, all the a-CNx films prepared by UBMS show a lower scratching depth. The a-CNx films have a hydrophilic characteristic with a surface free energy from 56.6to65.6mN∕m and a pr...

The multilayer granular structure has been developed and has proved to be a promising candidate for extremely high-density magnetic recording. Recently, the properties of friction and wear of the structure have been studied and the in-situ nanoscale protection concept has been proposed. In this paper, two series of CoCrPt–C multilayer samples with various interlayer carbon concentration and with/without carbon overcoat (top layer) are compared, having been prepared by using facing target sputtering (FTS) and normal dc sputtering (DCS), respectively. The corrosion resistance of the sample is investigated using environmental and electrochemical methods. Optical microscopy and time-of-flight secondary ion mass spectrometry are used to characterize the corrosion test samples. For the samples prepared by FTS, both top and interlayer carbon can provide protection for the media. In terms of the samples prepared by DCS, the carbon layer may increase the porous density during the corrosion process. It is concluded...