Surface modification of activated carbon fabric with ozone. Part 2: Thermal analysis with TGA-FTIR and DTA

Two samples of activated carbon fabrics (ACF) with very high surface area (>1300 to >1800 m²/g) fully ozonized in the part 1 of this study were analyzed by thermogravimetric analysis (TGA) coupled both with differential thermal analysis (DTA) and FT-IR spectroscopy (TGA-FTIR). The adsorbed water and the amount of oxygenated functional groups were determined. The ozonized ACF shows an exothermal decomposition at about 181–189°C which may be due at least in part to the decomposition of ozonide and/or peroxide groups. The TGA-FTIR has revealed that the main products released from the thermal decomposition are CO₂ followed by CO. Formic acid was detected only in correspondence to the exothermal transition at 181°C and was taken as a proof of the decomposition of secondary ozonides.     

Atomic layer deposition of SiO2 from Tris(dimethylamino)silane and ozone by using temperature-controlled water vapor treatment

Atomic layer deposition of SiO₂ from tris(dimethylamino)silane (TDMAS) and ozone as precursors on Si(100) surfaces at near-room temperatures was studied by infrared absorption spectroscopy with a multiple internal reflection geometry. TDMAS can be adsorbed at OH sites on hydroxylated Si surfaces at room temperature. Ozone oxidation of the TDMAS-treated Si surface is effective in removing hydroaminocarbon adsorbates introduced during TDMAS adsorption at room temperature. After oxidation by ozone, treatment with H₂O vapor at a substrate temperature of around 160 °C causes regeneration of OH sites for TDMAS adsorption. Cycles involving TDMAS adsorption and ozonization at room temperature followed by H₂O treatment at 160 °C permit the buildup of layers of SiO₂. The amount of residual hydroaminocarbon at the interface between the growing SiO₂ film and the substrate can be reduced with the ozone treated Si surface as a starting surface.     

Influence of ozone on N-doped multi-walled carbon nanotubes

Nitrogen-doped multi-walled carbon nanotubes (N-MWCNT) were selectively grown on oxidised silicon substrate by means of catalytic chemical vapour deposition with decomposition of acetonitrile in the presence of ferrocene (FeCp₂) at 900°C. The synthesised N-MWCNT film was initially treated with continuous ozone flow for various time periods and characterised by means of scanning electron microscopy and Raman spectroscopy. The electrochemical response of ozone-treated N-MWCNT film towards ferrocyanide/ferricyanide, [Fe(CN)₆]^3?/4? redox couple was investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy. The results were compared with those obtained for untreated N-MWCNT film. The findings reveal the occurrence of structural defects on surface of ozone-treated N-MWCNT film due to oxidation of nanotubes. Furthermore, the handling of N-MWCNT film with ozone increases the barrier for interfacial electron transfer and slows down the kinetics of redox reaction occurring on this particular electrode.     

Alkaline hydrothermal kinetics in titanate nanostructure formation

In this study, the mechanism of precursor dissolution and the influence of kinetics of dissolution on titanate nanotube formation were investigated. This comparative study explored the dissolution kinetics for the case of commercial titania powders, one composed of predominantly anatase (>95%) and the other rutile phase (>93%). These nanoparticle precursors were hydrothermally reacted in 9 mol L⁻¹ NaOH at 160 °C over a range of reaction times of between 2 and 32 h. The high surface area nanotube-form product was confirmed using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscopy. The concentration of nanotubes produced from the different precursors was established using Rietveld analysis with internal and external corundum standardization to calibrate the absolute concentrations of the samples. Interpretation of the dissolution process of the precursor materials indicated that the dissolution of anatase proceeds via a zero-order kinetic process, whereas rutile dissolution is through a second-order process. The TiO₂ nanostructure formation process and mechanism of TiO₂ precursor dissolution was confirmed by non-invasive dynamic light scattering measurements. Significant observations are that nanotube formation occurred over a broad range of hydrothermal treatment conditions and was strongly influenced by the order of precursor dissolution.     

Surface interaction and desorption of trimethyl phosphate from ozonized activated carbon fabric

Trimethyl phosphate (TMP) is a typical simulant of the CWA nerve agents and its adsorption on pristine and ozonized ACF has been studied by FT-IR and ESR spectroscopy. The FT-IR analysis is effective in putting in evidence the strong interaction of TMP with the ACF surfaces through the P = O stretching band shift toward lower frequencies after adsorption. Ozonized ACF ensures a stronger interaction with the adsorbate through the hydrogen bond formation between the adsorbed TMP and the oxygenated functional groups present on carbon surface. At room temperature the ozonized ACF is able to adsorb larger amounts of TMP than the pristine ACF and shows also a better retention of the adsorbate at room temperature. The TGA-FTIR analysis of TMP desorption from both ozonized and pristine ACF has shown that TMP undergoes a partial thermal decomposition into methanol and phosphoric acid above 175°C. The maximum methanol production rate was observed at 250°C in the TMP desorption process from ozonized ACF and at 280°C from TMP desorption from pristine ACF.     

Applying Ag–TiO2/functional filter for abating odor exhausted from semiconductor and opti-electronic industries

Some of the odor-related problems from the semiconductor and opti-electronic industries are caused by the volatile organic compounds, acetic acid, and dimethyl sulfide. These odorous exhausts would persecute residents’ health and lower the environmental quality. In this study, Ag–TiO₂/functional filter was applied to removal these odorous compounds. The results indicated that K₂CO₃/activated carbon filter (ACF) would be the better composition of functional filter, which attributed to larger surface area of ACF and mid-alkalinity of K₂CO₃. Comparing the TiO₂ type, P25 TiO₂ (Degussa, Germany)/functional filter showed the more superior photodegradation efficiency than ST01 TiO₂ (Ishihra Sangyo, Japan)/functional filter. In addition, Ag-modifying TiO₂/functional filter enhanced the photocatalysis via postponing the recombination between electrons and holes. The 0.001 M AgNO₃ solution was the optimal immersing concentration to make Ag dispersed uniformly on TiO₂ surface. Operating from 25 to 50 °C, the rising temperature was contributive to photodegradation efficiency due to the increase of system reaction energy. Processing photocatalysis below 75 % of relative humidity, existing humidity could be combined with holes to from hydronium (H₃O⁺) and hydroxyl radical (OH^?) to improve photodegradation. Assisted with ozone concentration ratio of 0.7 times, the removal efficiency for high pollutant concentration via Ag–TiO₂/functional filter could be improved up to 90 % until operating 180 min; this combined method could save the oxidant consumption more than single advanced oxidation method for processing pollutant.     

Promoting Photocatalytic Performance of ZnO Particles by Photochemically Reducing Ag+ on the Particle Surfaces

Dispersive Ag nanoparticles were formed on the surface of crystalline ZnO particles, using a photochemical reduction technique, to produce the Ag/ZnO with high photocatalytic performance. The prepared Ag/ZnO particles, as well as the ZnO particles without Ag attachments, were characterized using x-ray diffractometer, transmission electron microscope, and surface area analyzer. The abilities of the ZnO and the Ag/ZnO particles to photocatalytically decompose methylene blue under 365-nm ultraviolet light irradiation were evaluated by determining the corresponding specific reaction rate constant, k′_MB,m (based on the mass of the photocatalyst used). While the ZnO crystalline particles (k′_MB,m > 0.43 m³/(kg min)) already possessed better photocatalytic performance than the commercial photocatalyst P25 (k′_MB,m = 0.39 m³/(kg min)), the Ag/ZnO particles exhibited much better photocatalytic performance than the ZnO particles. The highest k′_MB,m for the Ag/ZnO particles was 1.93 m³/(kg min), which was about five times that of the P25.     

Effect of acidic anode treatment on carbon fibers for increasing fiber-matrix adhesion and its relationship to interlaminar shear strength of composites

An anodic surface treatment of PAN-based carbon fibers has been studied in increasing the surface functional groups on fibers, resulting in increasing composite mechanical behavior. With a viewpoint of acid-base interaction chemistry, the 10 wt% phosphoric acid solution is selected for the electrolyte. As an experimental result, very low electric current densities, such as 30–300 A·m^–2, are need for the changing of morphological and mechanical properties. According to FT-IR and XPS measurements, it reveals that the oxygen functional groups on fibers are largely dominated in ILSS of the composites, whereas the nitrogen functional groups are not affected in this system. Also, it is found that a moderate 70 A·m^–2 treatment on fibers seems promising to assess the improving of the physical and mechanical properties.     

Preparation of a pitch-based activated carbon with a high specific surface area

Pitch based activated carbons (PAC) with a high specific surface area were produced by a direct chemical activation route in which oxidative stabilized pitch derived from ethylene tar oil was reacted with potassium hydroxide under various activation conditions. It was found that PACs with a surface area of around 2600–3600 m² g^-1 could be obtained under suitable activation conditions. N₂ adsorption (at 77 K) and X-ray photoelectron spectroscopy experiments showed that the PAC has a uniformly developed micropore structure and a narrow pore size distribution (radius 0.8–1.6 nm). Abundant oxygen-containing functional groups (such as C–OH, C–O–C, C=O, COOR etc.) were found to exist on its surface. Compared with a commercially available activated carbon (AC) and also a pitch based activated carbon fibre, PAC has a quicker adsorption–desorption velocity and a larger adsorptive capacity to benzene due to its higher surface area. Clear surface differences between PAC and AC were observed by transmission electron microscopy. This revised version was published online in November 2006 with corrections to the Cover Date.     

Fabrication of hydrophobic/super-hydrophobic nanofilms on magnesium alloys by polymer plating

Hydrophobic/super-hydrophobic nanofilms with improved corrosion resistance were fabricated on the surfaces of Mg-Mn-Ce magnesium alloy by a surface modification technique, named as polymer plating, which has been developed to modify superficial characteristics of magnesium alloys with polymeric nanofilms through synthesized organic compounds of triazine dithiol containing functional groups. The nanofilms were prepared by the electrochemical and polymerization reactions during polymer plating analyzed from characteristics of Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy and scanning electron microscopy. The fabricated nanofilms changed the surface wettability of blank magnesium alloy from hydrophilic to hydrophobic with contact angle 119.0° of distilled water with lower surface free energy of 20.59 mJ/m² and even super-hydrophobic with contact angle 158.3° with lowest surface free energy of 4.68 mJ/m² by different functional nanofilms on their surfaces. Alteration of wettability from hydrophilic to hydrophobic and super-hydrophobic resulted from their low surface free energy and surface morphology with micro- and nano-rough structures. The corrosion behaviors from potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that the super-hydrophobic nanofilm has higher corrosion resistance and stability in 0.1 mol/L NaCl solution and lower corrosion current density (I_corr) with R_ct increasing two orders of magnitude of 16,500 Ω·cm² compared to that obtained for blank of 485 Ω·cm².     

XPS study of oxygen plasma activated PET

A study on oxygen plasma functionalization of polyethyleneterephthalate (PET) is presented. Samples were exposed to a weakly ionized, highly dissociated RF oxygen plasma with an electron temperature of 5 eV, a density of positive ions of 8×10¹⁵ m⁻³ and a density of neutral oxygen atoms of 4×10²¹ m⁻³. The oxygen pressure was 75 Pa and the discharge power was 200 W. The wettability of plasma-modified samples was determined by measuring the contact angle of a water drop, while the appearance of the functional groups on the sample surface was determined by using a high-resolution X-ray photoelectron spectrometer (XPS). Already in the order of seconds of the plasma treatment the samples were covered by the surface functional groups. These results were explained by the high flux of oxygen atoms onto the sample surface. The stability of functional groups on the plasma-modified PET surface stored in a dry plastic box was monitored by using XPS as a function of the ageing time. After 1 day of ageing, the concentration of newly formed functional groups decreased by about 15%.     

Study of structural and magnetic properties of (Co–Cu)Fe2O4/PANI composites

The nanocomposites of the polyaniline and Co_1−xCu_xFe₂O₄ (PANI/CoCuFe) were prepared by in-situ oxidative polymerization of aniline. Prepared nanocomposites samples were characterized by using various experimental techniques like X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), Mössbauer spectroscopy and ultraviolet–visible spectrophotometry (UV–VIS). The elemental analysis as obtained from the energy dispersive X-ray spectroscopy (EDAX) measurement is in close agreement with the expected composition from the stoichiometry of the reactant solutions. XRD result confirms that all the samples have the single phase cubic spinel structure. Unit cell parameter ‘a’ is found to decrease with the increase in copper ion substitution. The crystallite size was investigated by using the Debye–Scherer formula and it was found in the range of ∼28–37 nm. FE-SEM confirmed the homogeneous and well defined surface morphology of the synthesized samples. FT-IR study showed the main absorption bands corresponding to the spinel structure those arose due to the tetrahedral and octahedral stretching vibrations. Cation distribution was estimated using XRD data. Hysteresis measurements revealed that the saturation magnetization decreased with increase in Cu²⁺ substitution. Magnetic environment of ⁵⁷Fe in Cu-doped cobalt ferrite was investigated by using Mössbauer spectroscopy. Mössbauer study evidenced the ferrimagnetic behavior of the synthesized samples.     

Comparative study of nanocrystalline Zr0.85Ce0.15O2 powders synthesised by spray-pyrolysis and gel-combustion methods

Zr_0.85Ce_0.15O₂ nanopowders synthesised by gel-combustion and spray-pyrolysis methods were comparatively studied by means of X-ray diffraction, Raman spectroscopy, thermogravimetric and differential thermal analyses, specific surface area measurements, scanning and transmission electron microscopies and chemical analysis. Fully tetragonal powders were obtained by both methods, as determined by X-ray diffraction and Raman spectroscopy. Both materials exhibited extremely small crystallite sizes (about 6 nm) and high specific surface areas (93 m²/g and 42 m²/g for gel-combustion and spray-pyrolysis powders, respectively). In both cases, no tetragonal-to-monoclinic transition was observed in the whole temperature range up to 1300 °C by differential thermal analysis. The amounts of the expected impurities (Si, B, C) were acceptable and comparable in both cases.     

Sol-gel synthesis of titania hollow spheres

TiO₂ hollow spheres are prepared by a convenient sol-gel method at room temperature. The products were characterized by XRD, FESEM, TEM and FT-IR. It was found that these spheres are hollow inside with outer diameters of 200-500 nm. The average mesoporous diameter is about 9.8 nm. And the BET surface area and specific pore volume are about 161.9 m²/g and 0.441 cm³/g, respectively.     

Clew-like hierarchical ZnO nanostructure assembled by nanosheets as an efficient photocatalyst for degradation of azure B

In this study, hierarchical ZnO nanostructure assembled by nanosheets was synthesized via a facile and rapid ultrasound assisted route without any surfactant or template. The phase structure, morphology and optical property of the ZnO sample were investigated by XRD, FT-IR, SEM, and UV–Vis spectroscopy. Nitrogen sorption was also studied to determine the specific surface area and the pore size distribution. The ZnO sample was hexagonal pure phase of hierarchical clew-like microspheres consisting of nanosheets with average thickness and specific surface area of 50 nm and 41 m² g^?1, respectively. Synthesized ZnO was applied for the photocatalytic degradation of an organic dye, azure B as a pollutant model under UV irradiation. The effects of several parameters including dye concentration, catalyst dosage, pH, and irradiation time on photocatalytic degradation have been studied. The results indicated hierarchical ZnO has potential application for degrading of organic pollutants. Hydroxyl radicals were found to be main reactive species in this photodegradation process.     

Synthesis of mesoporous silica grafted with 3-glycidoxypropyltrimethoxy-silane

Hexagonal mesoporous silicas chemically modified with 3-glycidoxypropyltrimethoxy-silane functional groups were synthesized through the post-synthesis of surfactant free mesoporous silica (OSU-6-W). The solid state ²⁹Si NMR, titration method and elemental analysis of the modified samples showed that the average number of pendant groups in these hybrids were around 2.17 and 3.49 group/nm², respectively. The surface area analysis showed that these materials have pore diameters of 40.7 and 33.2 Å and surface areas of 966 and 720 m²/g, respectively. Infrared spectroscopy, solid state NMR for ¹³C and ²⁹Si nuclei and X-ray diffraction patterns are in agreement with the success of the proposed synthetic procedures, as confirmed for the formation of the mesoporous hybrids. They have shown good performance towards metal-ion adsorption.     

利用铈盐改性修饰活性炭纤维结构

利用硝酸铈铵对活性炭纤维进行了化学改性。研究了铈盐改性前后活性炭纤维的微观结构和表面化学结构的变化。结果表明，活性炭纤维经铈盐处理后，比表面积降低10％～20％左右，微孔孔径分布没有发生明显的变化，表面氧含量从原子分数11％提高至25％，使活性炭纤维表面形成更多的高价态含氧基团。并通过X射线光电子能谱和热重-红外联用的分析结果相结合，较为详细地、定量地分析了活性炭纤维表面的含氧基团。结果表明，利用热重一红外联用技术对活性炭纤维表面含氧基团的种类及其相对量分析结果与基于X射线光电子能谱的C1s分峰结果定量分析基本一致，两种结果可互为验证。     

UV Raman spectroscopic probing into nitrogen-doped hydrogenated amorphous carbon

From the viewpoint of hardness, chemical bonding states of nitrogen-doped hydrogenated amorphous carbon film were characterized by Ultra violet (UV) Raman spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. UV Raman spectra revealed that disorder of the structure in nitrogen-doped hydrogenated amorphous carbon was promoted by applying higher bias voltages in the preparation. FT-IR spectra showed that NH bonds decreased and sp³Csp³N bonds increased with the increase of the bias voltages. The content of sp³Csp³N bonds was maximized at the bias voltage of −800 V. We found out a guarantee that the content of sp³Csp³N bonds against bias voltages correlated with the hardness obtained by nanoindentation test. The structural disorder and the increase of sp³Csp³N bonds are possible source of the hardness in the case of nitrogen-doped hydrogenated amorphous carbon.     

Plasma treatment as a method for functionalising and improving dispersion of carbon nanotubes in epoxy resins

This study reports on the results of plasma-treated carbon nanotubes (CNTs) in the presence of oxygen and ammonia which can be scaled up for relatively large quantities of nanomaterials. The plasma treatment has been shown to change the surface chemistry and energy as well as the morphology of the carbon nanotubes. X-ray photoelectron spectroscopy analysis shows increases in oxygen and nitrogen groups on the oxygen- and ammonia-treated CNTs, respectively. Titration of the enhanced oxygen plasma-treated CNTs reveals an increased presence of carboxylic acid groups at 2.97 wt% whilst bulk density decreases from 151 kg/m³ for untreated carbon nanotubes to 76 kg/m³ after the enhanced oxygen treatment. The free surface energy has also been shown to increase from 33.70 up to 53.72 mJ/m² determined using a capillary rise technique. The plasma-treated carbon nanotubes have been mixed in epoxy and have shown an improvement in dispersion, which was quantitatively evaluated using an optical coherence tomography (OCT) technique shown to be suitable for nanocomposite characterisation. This research has demonstrated that it is possible to surface functionalise large quantities of carbon nanotubes in a single process, and that this process improves the dispersion of the carbon nanotubes in epoxy.     

The influence of different alkaline earth oxides on the structural and optical properties of undoped,Ce-doped,Sm-doped,and Sm/Ce co-doped lithium alumino-phosphate glasses

Undoped, singly Sm doped, Ce doped, and Sm/Ce co-doped lithium alumino-phosphate glasses with different alkaline earth modifiers were prepared by melt quenching. The structure of the prepared glasses was investigated by FT-IR and Raman, as well as by optical spectroscopy. The effect of the optical basicity of the host glass matrix on the added active dopants was studied, as was the effect doping had on the phosphate structural units. The optical edge shifts toward higher wavelengths with an increase in the optical basicity due to the increased polarizability of the glass matrix, but also with increasing CeO₂ concentration as a result of Ce³⁺/Ce⁴⁺ inter valence charge transfer (IV-CT) absorption. The optical band gap for direct and indirect allowed transitions was calculated for the undoped glasses. The glass sample containing Mg²⁺ modifier ions is found to have the highest value (4.16 eV) for the optical band gap while Ba²⁺ has the lowest value (3.61 eV). The change in the optical band gap arises from the structural changes and the overall polarizability (optical basicity). Refractive index, molar refractivity R_m and molar polarizability α_m values increase with increasing optical basicity of the glasses. The characteristic absorption peaks of Sm³⁺ were also investigated. For Sm/Ce co-doped glasses, especially at high concentration of CeO₂, the absorption of Ce³⁺ hinders the high energy absorption of Sm³⁺ and this effect becomes more obvious with increasing optical basicity.