Dependence of the composition and bonding structure of carbon nitride films deposited by direct current plasma assisted pulsed laser ablation on the deposition temperature

Carbon nitride films were deposited by direct current plasma assisted pulsed laser ablation of a graphite target under nitrogen atmosphere. Atomic force microscopy (AFM), Fourier transform infrared (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface morphology, bonding structure, and composition of the deposited films. The influence of deposition temperature in the range 25–400 °C on the composition and bonding structure of carbon nitride films was systematically studied. AFM images show that surface roughness and cluster size increase monotonically with deposition temperature. XPS, FTIR, and Raman spectra indicate directly the existence of CN, CN, and CN bonds in the deposited films. The increase of deposition temperature results in a drastic decrease in the N/C ratio, the content of CN bond and N atoms bonded to sp³ C atoms, in addition to the increase in the content of disorder sp² C atoms and N atoms bonded to sp² C atoms in the deposited films. Raman spectra show that the intensity ratio of D peak over G peak increases with increasing deposition temperature to 200 °C, then decreases with the further increase of deposition temperature, which results from the continuous growth of sp² cluster in the films.     

Enhancement of fluorine doped amorphous carbon thin films from microwave surface wave plasma activated above room temperature

Fluorinated amorphous carbon (a-C:F) thin films were synthesized above room temperature by microwave surface wave plasma chemical vapour deposition (MW SWP CVD). The effect of deposition temperature on optical, electrical, chemical and bonding properties of the a-C:F films were studied by ultraviolet–visible spectroscopy (UV–VIS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), Raman spectrometry and TEM measurements. The film exhibits high transparency and decrease in optical band gap with increasing deposition temperature. FTIR study shows the increase in CC and decrease in C–Fx bonds of the films with increasing deposition temperature. Raman study shows some important structural changes in the films due to fluorine incorporation. XPS result shows the shift of carbon peak to higher binding energy due to carbon fluorine link to the films. TEM shows the increasing graphitic layer in the films with increasing deposition temperature.     

The effect of argon on the electron field emission properties of α-C:N thin films

Amorphous carbon nitride (α-C:N) thin films were synthesized on silicon as electron emitters by the electron cyclotron resonance chemical vapor deposition (ECR-CVD) system in which a negative dc bias was applied to the graphite substrate holder and a mixture of C₂H₂ and N₂ was used as precursors. The addition of Ar combined with the application of a negative dc bias can increase nitrogen content (N/C) measured by X-ray photoelectron spectroscopy (XPS), eliminate the dangling bonds in the film determined by Fourier transform infrared (FTIR) spectroscopy, decrease the film thickness measured by field emission scanning electron microscope (FE-SEM), increase the film roughness measured by atomic force microscope (AFM) and raise the graphitic content examined by Raman spectroscopy. The result shows that the onset emission field of α-C:N with Ar addition to the precursors can be as low as 4.5 V μm⁻¹ compared with 9.5 V μm⁻¹ of the film without the addition of Ar.     

Effect of deposition voltage on the microstructure of electrochemically deposited hydrogenated amorphous carbon films

Hydrogenated amorphous carbon (a-C:H) films were deposited on Si substrates by electrolysis in a methanol solution at ambient pressure and a low temperature (50 °C), using various deposition voltages. The influence of deposition voltage on the microstructure of the resulting films was analyzed by visible Raman spectroscopy at 514.5 nm and X-ray photoelectron spectroscopy (XPS). The contents of sp³ bonded carbon in the various films were obtained by the curve fitting technique to the C1s peak in the XPS spectra. The hardness and Young’s modulus of the a-C:H films were determined using a nanoindenter. The Raman characteristics suggest an increase of the ratio of sp³/sp² bonded carbon with increasing deposition voltage. The percentage of sp³-bonded carbon is determined as 33–55% obtained from XPS. Corresponding to the increase of sp³/sp², the hardness and Young’s modulus of the films both increase as the deposition voltage increases from 800 V to 1600 V.     

Simultaneous reduction and N-doping of graphene oxides by low-energy N2+ ion sputtering

An easy and catalyst-free method was used to obtain N-doped reduced graphene oxides (N-RGO) through low-energy N₂⁺ ion sputtering of graphene oxides (GO). The simultaneous reduction and N-doping of GO during the sputtering were systematically investigated by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure and Raman spectroscopy. The N-doping and reduction levels, which are determined by the N/C and O/C atomic ratios from the quantitative XPS analysis, respectively, can be easily controlled by varying the N₂⁺ ion sputtering time. In addition, three different N species, namely, nitrile-like N, graphitic N and pyridinic N, can be distinguished in N-RGO.     

Deposition of hydrogenated amorphous carbon films with enhanced sp3-C bonding on nanocrystalline palladium interlayer

The present study deals with the deposition of hydrogenated amorphous carbon (a-C:H) films on Si (100) substrates with and without an interlayer of nanocrystalline palladium (nc-Pd) on them, by high-voltage electro-dissociation of N,N-dimethyl formamide (DMF). Significant improvement in the sp³ carbon content has been observed for a-C:H films grown on nc-Pd interlayer as revealed by Fourier transformed infrared (FTIR), Raman, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopic techniques. It is inferred that H₂ activation on palladium sites leads to the stabilization of sp³-C bonding, thereby improving the quality of the deposits grown on them.     

Photodegradation of Azathioprine in the Presence of Sodium Thiosulfate

The effect of sodium thiosulfate (ST) on the photodegradation of azathioprine (AZA) was analyzed by UV-VIS spectroscopy, photoluminescence (PL), FTIR spectroscopy, Raman scattering, X-ray photoelectron (XPS) spectroscopy, thermogravimetry (TG) and mass spectrometry (MS). The PL studies highlighted that as the ST concentration increased from 25 wt.% to 75 wt.% in the AZA:ST mixture, the emission band of AZA gradual downshifted to 553, 542 and 530 nm. The photodegradation process of AZA:ST induced: (i) the emergence of a new band in the 320–400 nm range in the UV-VIS spectra of AZA and (ii) a change in the intensity ratio of the photoluminescence excitation (PLE) bands in the 280–335 and 335–430 nm spectral ranges. These changes suggest the emergence of new compounds during the photo-oxidation reaction of AZA with ST. The invoked photodegradation compounds were confirmed by studies of the Raman scattering, the FTIR spectroscopy and XPS spectroscopy through: (i) the downshift of the IR band of AZA from 1336 cm⁻¹ to 1331 cm⁻¹, attributed to N-C-N deformation in the purine ring; (ii) the change in the intensity ratio of the Raman lines peaking at 1305 cm⁻¹ and 1330 cm⁻¹ from 3.45 to 4.57, as the weight of ST in the AZA:ST mixture mass increased; and (iii) the emergence of a new band in the XPS O1s spectrum peaking at 531 eV, which was associated with the C=O bond. Through correlated studies of TG-MS, the main key fragments of ST-reacted AZA are reported.     

Properties of amorphous a-CH(:N) films synthesized by direct ion beam deposition and plasma-assisted chemical vapour deposition

Hydrogenated carbon films and hydrogenated carbon films containing nitrogen have been synthesized by direct ion beam deposition (IBD) using cyclohexane and methane as precursors and by plasma-assisted chemical vapour deposition (PACVD) using cyclohexane and acetylene as precursors. The elemental composition has been assessed by gas chromatography. The films' structure has been analysed by FTIR, Raman, NEXAFS spectroscopy and X-ray reflectivity. The hardness has been determined by nanoindentation and microhardness measurements, and the stress by optical profilometry.FTIR measurements reveal an increasing nitrile and amine group absorption with a corresponding decrease of C–H stretching modes as the nitrogen concentration in the film increases. The nitrogen-containing functional groups are proposed to be at peripheral positions of graphitic domains. The corresponding reduction of the domain size is detected in the Raman data, and the increase of delocalized bonding in a-CH(:N) films with respect to a-CH films is confirmed by the NEXAFS results. In the carbon K-edge spectra, the intensity of the π^* CC resonance at ≃285.3 eV has been found to increase as a function of N content. This indicates principally an increment of the sp² hybridization. Such a structural change leads to a decrease in the hardness and the internal compressive stress with respect to a-CH films. In a film containing 15 at% N, the hardness is reduced to 44% and the stress to 36% of that for a-CH.     

Characteristics of nitrogen doped diamond-like carbon thin films grown by microwave surface-wave plasma CVD

Nitrogen doped diamond-like carbon (DLC:N) thin films were deposited on p-type silicon (p-Si) and quartz substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at low temperature (< 100 °C). For films deposition, argon (Ar: 200 sccm), acetylene (C₂H₂:10 sccm) and nitrogen (N: 5 sccm) were used as carrier, source and doping gases respectively. DLC:N thin films were deposited at 1000 W microwave power where as gas composition pressures were ranged from 110 Pa to 50 Pa. Analytical methods such as X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, FTIR and Raman spectroscopy were employed to investigate the chemical, optical and structural properties of the DLC:N films respectively. The lowest optical gap of the film was found to be 1.6 eV at 50 Pa gas composition pressure.     

Synthesis of amorphous carbon nitride using reactive ion beam sputtering deposition with grazing bombardment

Amorphous carbon nitride (a-C:N) thin films were synthesised on steel substrates using reactive ion beam sputtering deposition (RIBSD). A single ion beam is arranged to sputter the graphite target at 75° incidence and concurrently bombard the growing film at grazing incidence angles of the ion beam. Nanoindentation, Raman spectroscopy, FTIR, FT-Raman and XPS were employed to characterise the mechanical and structural properties of the films. It was found that grazing incident bombardment has a significant effect on film structure through an increase in nitrogen content and formation of nitrogen doped structure.     

Structural and ion transport properties of sodium ion conducting Na2MTeO6 (M= MgNi and MgZn) solid electrolytes

Solid-state electrolytes Na₂MTeO₆ (M = MgNi and MgZn) were prepared via a conventional solid-state reaction method. Structural properties of the samples were investigated by using powder X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS) techniques. XPS and XRD studies indicate the phase pure hexagonal layered P2-type structure of samples. Raman and FTIR spectroscopy reveal the possible bending and stretching vibration modes for Te–O and other metal oxides. The ion transport properties of the solid electrolytes were investigated by using AC impedance spectroscopy. The electrical properties were examined by means of classical brick layer model. The specific grain conductivity (σ_g) is found to be 2.13 × 10⁻⁵ S cm⁻¹ and 0.90 × 10⁻⁵ S cm⁻¹ at 20 °C for Na₂MgNiTeO₆ and Na₂MgZnTeO₆ electrolytes, respectively. The activation energy of σ_g for Na₂MgNiTeO₆ and Na₂MgZnTeO₆ is found to be 0.59 eV and 0.36 eV respectively for the temperature below 30 °C. Summerfield AC conductivity scaling analysis of samples is performed. These electrolytes could be potential candidates in solid-state Na⁺ battery applications.     

Synthesis of graphene paper from pyrolyzed asphalt

A new technique for the synthesis of large sheets (>10 cm²) of multi-layered graphene is presented. The condensation onto a heated surface (≈650 °C) of fumes from the thermal decomposition of asphalt in a ceramic crucible produces carbon films with a metallic sheen. Heating was done by a Fisher burner (natural gas/air) flame and the crucible was covered but exposed to laboratory atmosphere. These films were determined to be multi-layered graphene by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), Raman and infrared spectroscopy and X-ray diffraction. XPS indicates that the films are primarily sp² hybridized carbon with small amounts of sp³ C–H and C–O or C–N functionalities. Based on the D band shift (1593 cm⁻¹) and the ratio of D band to G band (1354 cm⁻¹) of 0.93, the Raman spectrum also indicates that the material is sp² C with some nanocrystalline features. The infrared spectrum exhibits A_1U (868 cm⁻¹) and E_1U (1599 cm⁻¹) stretching of the intralayer bonds of graphene. This form of chemical vapor deposition may be a scalable to give much larger surface areas. Furthermore, the process does not require metal substrates. Deposition onto silica nanosprings and diatomites is demonstrated.     

Stacked-cup-type MWCNTs as highly stable lithium-ion battery anodes

Stacked-cup type multiwall carbon nanotubes (MWCNTs) were synthesized by floating catalyst chemical vapor deposition methods. The materials were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements showed that the stacked-cup-type MWCNTs as lithium-ion battery anode materials delivered a stable capacity of ~310 mAh g^?1 at a rate of C/2 to 300 cycles. Furthermore, the materials were very stable and the coulombic efficiency exceeded 99.9 % over more than 300 cycles. Stable materials structure and the solid electrolyte interphase films were the main reasons for the durable cycling behavior, as confirmed by ex situ TEM and Raman spectroscopy, as well as electrochemical impedance spectroscopy (EIS). The results indicated that the stacked-cup-type MWCNTs produced in this work are candidate materials for lithium-ion battery anodes.     

Effect of nitrogen atomic percentage on N+-bombarded MWCNTs in cytocompatibility and hemocompatibility

N⁺-bombarded multi-walled carbon nanotubes (N⁺-bombarded MWCNTs), with different nitrogen atomic percentages, were achieved by different N ion beam currents using ion beam-assisted deposition (IBAD) on MWCNTs synthesized by chemical vapor deposition (CVD). Characterizations of N⁺-bombarded MWCNTs were evaluated by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and contact angle. For comparison, the in vitro cytocompatibility of the N⁺-bombarded MWCNTs with different N atomic percentages was assessed by cellular adhesion investigation using human endothelial cells (EAHY926) and mouse fibroblast cells (L929), respectively. The results showed that the presence of nitrogen in MWCNTs accelerated cell growth and proliferation of cell culture. The higher nitrogen content of N⁺-bombarded MWCNTs, the better cytocompatibility. In addition, N⁺-bombarded MWCNTs with higher N atomic percentage displayed lower platelet adhesion rate. No hemolysis can be observed on the surfaces. These results proved that higher N atomic percentage led N⁺-bombarded MWCNTs to better hemocompatibility.     

Structural and chemical analysis of amorphous B–N–C thin films deposited by RF sputtering

Ternary Boron–Nitrogen–Carbon (B–N–C) thin films were deposited, onto silicon substrates, by reactive radio frequency (RF) sputtering from a boron carbide (B₄C) target in a gas mixture of nitrogen and argon. The influence of the RF power (P_RF) on the structure and the chemical composition of these films are studied by Fourier transform Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements. The two techniques reveal the presence of B, C and N atoms in the deposited films. The presence of nitrogen in the atmosphere of the deposition chamber produces ternary B–N–C films composed mainly with a mixture of B–N and CN bonds as revealed by these techniques. The boron content increases while carbon and nitrogen contents decrease with P_RF. The higher proportion of boron atoms produced a strong contribution of the boron nitride in the final compound B–N–C films.     

Sputter deposition of highly dispersed platinum nanoparticles on carbon nanotube arrays for fuel cell electrode material

Vertically aligned carbon nanotube (VACNT) arrays were synthesized using a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system for polymer electrolyte fuel cell (PEMFC) electrode applications. Platinum nanoparticles (Pt NPs) were deposited on as grown VACNT arrays by a DC sputtering system. Pt NPs in the size range of 3–5 nm were formed on the CNT surfaces. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and electron microscopy were employed to study the structural and chemical bonding changes post deposition of Pt NPs. Variable particle density along the nanotube length was observed with cluster formation on tip ends and individual Pt NPs forming farthest away from tip ends. Change observed in the C1s and N1s core level spectra and its possible implications on the Pt/VACNT properties were also discussed.     

Thermal degradation of flame‐retarded polyethylene/magnesium hydroxide/poly(ethylene‐co‐propylene) elastomer composites

Magnesium hydroxide‐based halogen‐free flame retarded linear low‐density polyethylene (LLDPE) composites containing poly(ethylene‐co‐propylene) (EP) elastomer were prepared by a melt process and subsequently vulcanized thermally. The thermal degradation of the composites was studied using thermogravimetric (TG) analysis and real‐time Fourier transform infrared (RT‐FTIR) spectroscopy. The combustion residues from the composites were characterized by Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS). The results from TG and RT‐FTIR tests show that the incorporation of a suitable amount of the elastomer into polyethylene/magnesium hydroxide composites after vulcanization increases the thermal stability. A graphite‐like char was found for the composites with EP elastomer, from Raman spectroscopy studies. XPS results indicate that there are several forms of carbon present in the combustion residues of the composites with EP elastomer, compared with only one form of carbon in the residues of the composites without the elastomer. Copyright © 2003 Society of Chemical Industry     

Surface modification of bioceramics by grafting of tailored allyl phosphonic acid

Abstract

A new route to interfacial bonding between ceramic and matrix in biocomposites is identified. A tailored allyl phosphonic acid is used as a coupling agent bound to the surface of a bioceramic to form a 'grafted' calcium phosphate (CAP). The allyl phosphonic acid coupling agent is synthesised by reaction of allyl halide and trialkyl phosphite. Successful synthesis was confirmed by nuclear magnetic resonance and Fourier transform infrared spectroscopy (FTIR). The allyl phosphonic acid was incorporated onto calcium phosphate using a wet chemical coprecipitation synthesis route. The resulting 'grafted' CAP was characterised using FTIR coupled with photoacoustic sampling, and Fourier transform Raman spectroscopy (FTR). The spectroscopic data suggest an interaction between the allyl phosphonic acid and calcium phosphate resulting from observed reductions in intensity of the hydroxyl (3570 cm^?1) and phosphate ν ₃ (1030 cm^?1) peaks. The continued presence of C=C functionality on the surface of the grafted CAP was indicated by FTIR and FTR spectra (peaks at 1650 and 1635 cm^?1 respectively) and confirmed by X-ray photoelectron spectroscopy (XPS). On the basis of these results, it is concluded that grafted CAP may be used to produce a chemically bonded composite with superior mechanical properties.     

Structure of chemically prepared poly-(para-phenylenediamine) investigated by spectroscopic techniques

The structure of chemically prepared poly-p-phenylenediamine (PpPD) was investigated by Resonance Raman (RR), FTIR, UV-VIS-NIR, X-ray photoelectron (XPS), X-ray Absorption at Nitrogen K edge (N K XANES), and Electron paramagnetic Resonance (EPR) spectroscopies. XPS, EPR and N K XANES data reveal that polymeric structure is formed mainly by radical cations and dication nitrogens. It excludes the possibility that PpPD chains have azo or phenazinic nitrogens, as commonly is supposed in the literature. The RR spectrum of PpPD shows two characteristic bands at 1527 cm⁻¹ and 1590 cm⁻¹ that were assigned to νCN and νCC of dication units, respectively, similar to polyaniline in pernigraniline base form. The presence of radical cations was confirmed by Raman data owing to the presence of bands at 1325/1370 cm⁻¹, characteristic of νC-N of polaronic segments. Thus, all results indicate that PpPD has a doped PANI-like structure, with semi-quinoid and quinoid rings, and has no phenazinic rings, as observed for poly-o-phenylenediamine.     

热处理温度对对位芳纶纤维表面聚集态结构和性能影响

以不同温度(200,250,300,350℃)热处理对位芳纶纤维,用傅立叶变换红外光谱(FTIR)、拉曼光谱(Raman)、X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)分析了氧化热处理对对位芳纶纤维表面基团和聚集态结构的影响.FTIR和XRD分析结果表明,经250℃及以上热处理,纤维表层分...