Preparation of Ag nanoparticles loaded TiO2 nanoplate arrays on activated carbon fibers with enhanced photocatalytic activity

Ag loaded TiO₂ nanoplate array which grew on activated carbon fiber (ACF) was prepared in the present work. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue (MB) was used to investigate the activity of the synthesized samples. Under both UV and visible light irradiation, the Ag loaded samples showed enhanced photocatalytic activity. Besides, the effect of the deposition dosage of Ag nanoparticles on the photocatalytic activity was also investigated. Under UV light irradiation, the Ag nanoparticles acted as electron traps, which enhanced electron–hole separation efficiency of TiO₂. Under visible light irradiation, the Ag nanoparticles showed surface plasmon resonance, which induced the visible light responsive photocatalytic activity for the obtained samples.     

Characterization of microstructure and surface properties of heat-treated PAN-and rayon-based activated carbon fibers

Polyacrylonitrile- and rayon-based activated carbon fibers (ACFs), subject to heat treatment over 600–1,100°C under N₂ flow, were investigated using a number of surface analytical methods, including N₂ adsorption isotherm, elemental analysis, and X-ray photoelectron spectroscopy. The adsorption capacities of benzene, carbon tetrachloride, and water vapor on as-received and heat-treated ACFs were determined. Results show that the ACFs under study were highly microporous but heat-treated ACFs contained more mesopores in the range of 20–30 Å for PAN-based and 30–45 Å for rayon-based. It can be seen that the high-resolution α_s plot provided valuable information about structure properties. The pore size distributions of ACFs gave insight into the pore development with heat treatment temperature. Besides, phenolic groups were found to be the most abundant oxygen-containing functional groups on the surface of both ACFs. The vapor adsorptions on ACFs indicated that molecular size and polarity of vapors, as well as the microstructure and chemistry of ACFs profoundly influenced the adsorption performance.     

活性炭负载TiO2的制备及其光催化性能的研究

以钛酸四丁酯（Ti（OC4H9）4）为原料,用溶胶-凝胶法制备活性炭（AC）负载（TiO2。XRD分析其晶型组成。实验研究了不同TiO2负载量、不同煅烧时间、不同煅烧温度以及不同使用次数等情况下TiO2/AC光催化剂的光催化活性。实验结果表明,当负载量为28.2%、煅烧时间为4h、煅烧温度为400℃时催化剂活性最高,甲基橙溶液的降解率到达了98.09%。同时研究表明了多次使用后的TiO2/AC光催化剂仍具有很好的光催化性能。     

Preparation and characterization of trilobal activated carbon fibers

The objective of this research was to evaluate the effectiveness of several different methods for controlling the pore size and pore size distribution in activated carbon fibers. Variables studied included fiber shape, activation time, and the addition of small amounts of silver nitrate. Pure isotropic pitch and the same isotropic pitch containing 1 wt.% silver were melt spun to form fibers with round and trilobal cross sections. These fibers were then stabilized, carbonized, and activated in carbon dioxide. Field emission scanning electron microscopy (FE SEM), electron dispersive spectra (EDS), and wavelength dispersive spectra (WDS) were used to monitor the size and distribution of the silver particles in the fibers before and after activation. Each of these analyses showed that the distribution of silver particles was extremely uniform before and after activation. The fibers were also weighed before and after activation to determine the percent burn-off. The BET specific surface areas of the activated fibers were determined from N₂ adsorption isotherms measured at −196 °C. The results showed that round and trilobal fibers with equivalent cross-sectional areas yielded similar burn-off values and specific surface areas after activation. Also, activation rates were found to be independent of CO₂ flow rate. The porosity of the activated fibers depended on the total time of activation and the cross-sectional area of fibers. The N₂ adsorption measurements showed that the activated fibers had extremely high specific surface areas (greater than 3000 m²/g) and high degrees of meso- and macro-porosity. FE SEM was also used to investigate surface texture and size of pore openings on the surfaces of the activated fibers. The photos showed that silver particles generated surface macro- and mesopores, in agreement with the inferences from N₂ adsorption measurements.     

Preparation and characterization of silicon carbide fibers from activated carbon fibers

Silicon carbide fibers were prepared by the reaction between activated carbon fibers and silicon monoxide generated from a mixture of silicon and silicon dioxide at temperatures from 1200 to 1300°C in an inert atmosphere of argon. The reaction was completed at temperatures as low as 1200°C, which means that activated carbon fibers had a high reactivity. The resulting sample maintained the original morphology of the starting material, which was an advantage because of the difficulty in post shaping silicon carbide, and led to a silicon carbide fiber with high specific surface area. The resulting samples were characterized by powder X-ray diffraction, thermal gravimetric analysis, and by nitrogen adsorption measurements at 77.4 K to obtain surface area and pore size distributions. The morphology of the resulting sample was observed by scanning electron microscopy and the electronic structure was investigated by Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy techniques.     

Gentamicin‐loaded poly(acrylic acid)‐grafted cotton fibers,part 1: Synthesis,characterization, and preliminary drug release study

This study describes preparation of poly (acrylic acid)‐grafted cotton fibers and release of antibiotic drug gentamicin sulfate from them under physiological conditions. Poly(acrylic acid) has been grafted onto cellulose backbone of cotton fibers via Ce(IV)‐initiated polymerization in aqueous medium. The conditions obtained for optimum grafting were as follows: initiation time 30 min; initiation temperature 37°C; monomer concentration 27.8 mM; grafting temperature 30°C; nitric acid (catalyst) concentration 0.1M. The grafted fibers were characterized by FTIR, TGA, and SEM analysis. The antibiotic drug gentamicin sulfate (GS) was loaded into the grafted fibers by equilibration method and release was studied under physiological conditions. The kinetic release data was interpreted by first‐order kinetic model. Finally, drug‐loaded fibers showed fair antibacterial action against Escherichia coli. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation,characterization and photocatalytic activity evaluation of micro- and mesoporous TiO2/spherical activated carbon

The influences of heat-treatment temperature and activation time on the properties of TiO₂ supported on spherical activated carbon (TiO₂/SAC) were investigated. Nano-sized TiO₂ was dispersed on the spherical activated carbon with the size of 10–30 nm. Some anatase phase of TiO₂ was transformed to rutile phase of TiO₂ with an increase of heat-treatment temperature. All of the TiO₂/SAC photocatalysts had microporous structure, with the mesopore volume increasing over an activation time of 6 h. The TiO₂/SAC photocatalysts obtained at activation times of 6 h and 9 h were observed synergistic effects between adsorption and photocatalysis in the removal of humic acid.     

The effect of processing conditions on microstructure of Pd-containing activated carbon fibers

Palladium-doped activated carbon fibers are being evaluated as candidate materials for enhanced hydrogen storage at near ambient conditions. Pd-doped fibers were spun using a Pd salt mixed with an isotropic pitch precursor. Experimental techniques such as in situ X-ray analysis, thermogravimetric studies, scanning transmission electron microscopy and gas adsorption were employed to understand how processing conditions for the production of Pd-doped activated carbon fibers affect the microstructure, pore development, and dispersion of metal particles throughout the fibers. The results showed that PdO phase is present in the stabilized fibers and that this oxide phase is stable up to about 250 °C. The oxide phase transforms into Pd metal with increasing heat treatment temperature, going through the formation of an intermediate carbide phase. Sintering of Pd particles was observed with heat treatment at temperatures over 750 °C. It was also found that pore development during physical activation with CO₂ was not significantly affected by the presence of Pd particles within the fibers.     

Synthesis and characterization of conducting polyaniline‐activated carbon nanocomposites

Conducting polyaniline (PAni)/activated carbon (AC) nanocomposites were synthesized by the in situ chemical polymerization method. The resultant shell–core PAni–AC nanocomposites were characterized by elemental analysis, Fourier transform infrared, scanning electron microscopy, thermal gravimetric analysis, X‐ray diffraction, and transmission electron microscopy. We did not observe any significant chemical interaction between the PAni and AC, only core–shell coupling between the AC and the tightly coated polymer chain was revealed. Measurement of the physical properties showed that the incorporation of conducting PAni on to AC particles during chemical synthesis increased electrical conductivity and thermal stability by several orders of magnitude to that of the pristine PAni powders. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1973–1977, 2007     

Fabrication and characterization of a solid polymeric electrolyte of PAN‐TiO2‐LiClO4

The ionic conductivity of PAN‐TiO₂‐LiClO₄ as a function of TiO₂ concentration and temperature has been reported. The electrolyte samples were prepared by solution casting technique. Their conductivity was measured using the impedance spectroscopy technique. The highest room temperature conductivity of 1.8 × 10^?4 S cm^?1 was obtained at 7.5 wt % of TiO₂ filler. It was observed that the relationship between temperature and conductivity were linear, fitting well in Arrhenius and not in Vogel‐Tamman‐Fulcher equation. The pre‐exponential factor, σ₀ and E_a are 1.8 × 10^?4 S cm^?1 and 0.15 eV, respectively. The conductivity data have been supported by differential scanning calorimeter (DSC) analysis. DSC analysis showed that there was a significant change in glass transition temperature (T_g) with the filler concentration. The SEM micrograph revealed that the TiO₂ particles are dispersed in the electrolyte, thus enhancing its conductivity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,densification, and microstructure of TaC‐TaB2‐SiC ceramics

The usual way to prepare TaC‐TaB₂ ceramics by adding B₄C to TaC leads to formation of residual C, which degrades samples’ mechanical properties. To eliminate the residual C, we suggest incorporating Si together with B₄C into TaC ceramics, resulting in new ultrahigh‐temperature ceramics (TaC‐TaB₂‐SiC). Dense ceramics (>99%) with SiC volume fraction ranging from 15.86% to 41.04% were fabricated by reactive spark plasma sintering at 1900°C for 5 minutes. The formation of SiO₂‐based transient liquid phase was evidenced by the “film” in intermediate products, which can promote densification. The fine‐grained microstructure in final products was found to be associated with the in situ formed SiC, which impeded TaC and TaB₂ grains from coarsening by the pinning effect. Besides, ultrafine TaB₂ grains (~100 nm) produced during the reaction and then rearranged in liquid also contributed to grain refinement. Compared to TaC‐TaB₂(‐C) ceramics prepared from TaC and B₄C, the acquired composites exhibit better mechanical properties, due to their fine‐grained microstructures and the elimination of residual C.     

聚丙烯腈基活性碳纤维吸附CO2的性能

以国产聚丙烯腈(PAN)基碳纤维为原料,采用KOH为活化剂制备PAN基活性碳纤维。测定了不同ACF样品的CO2吸附量,并通过氮气吸附、碘吸附以及红外光谱对所得活性碳纤维的比表面积、孔结构及表面官能团进行表征。研究了活化温度、活化时间和表面改性对活性碳纤维CO2吸附量的影响。结果表明,活化温度是影响活性碳纤维CO2吸附量的主要因素。当活化温度为850℃时,所得活性碳纤维BET比表面积为1235m2/g,微孔比表面积为745 m2/g,在吸附温度为273 K、吸附相对压力P/P0为1时,CO2的吸附量达到87.29 mL/g。     

Preparation and characterization of a novel activated carbon‐supported N‐doped visible light response photocatalyst (TiO2−xNy/AC)

A photocatalyst, TiO_2?xN_y/AC (activated carbon (AC) supported N‐doped TiO₂), highly active in both the Vis and UV range, was prepared by calcination of the TiO₂ precursor prepared by acid‐catalyzed hydrolysis in an ammonia atmosphere. The powders were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, X‐ray diffraction, N₂ adsorption, Fourier transform infrared spectroscopy and phenol degradation. The doped N in the TiO₂ crystal lattice creates an electron‐occupied intra‐band gap allowing electron‐hole pair generation under Vis irradiation (500–560 nm). The TiO_2?xN_y/AC exhibited high levels of activity and the same activity trends for phenol degradation under both Vis and UV irradiation: TiO_2?xN_y/AC calcined at 500 °C for 4 h exhibited the highest activity. The band‐gap level newly formed by doped N can act as a center for the photo‐generated holes and is beneficial for the UV activity enhancement. The performance of the prepared TiO_2?xN_y/AC photocatalyst revealed its practical potential in the field of solar photocatalytic degradation of aqueous contaminants. Copyright © 2007 Society of Chemical Industry     

天然矿物负载纳米二氧化钛复合材料的制备与表征

采用水解沉淀法制备了白炭黑、硅藻土和蛋白土负载纳米二氧化钛复合材料。通过SEM和XRD等手段对复合材料分别进行了表征,并用罗丹明B溶液的光催化脱色率来评价复合材料的光催化性能。结果表明,在复合材料表面负载了大量的二氧化钛且主要以锐钛型为主,白炭黑、硅藻土、蛋白土复合材料表面负载的二氧化钛的平均粒径分别为14.6、25.7、22.9 nm。二氧化钛/白炭黑、二氧化钛/硅藻土、二氧化钛/蛋白土3种复合材料的最佳制备条件分别为：700 ℃煅烧2 h,二氧化钛负载量为30%;700 ℃煅烧2 h,二氧化钛负载量为20%;600 ℃煅烧2 h,二氧化钛负载量为20%。3种复合材料对罗丹明B溶液15 min的降解率分别达到98.6%、97.4%和87.7%。     

Preparation,characterization, and drug release behaviors of drug‐loaded ε‐caprolactone/L‐lactide copolymer nanoparticles

Copolymers of ε‐caprolactone and L ‐lactide (PCLLA) with different monomer ratio were synthesized by ring opening polymerization, and drug‐loaded nanoparticles of poly‐ε‐caprolactone (PCL), poly‐L ‐lactide (PLLA), and their copolymers were prepared by precipitation method, respectively. The results of differential scanning calorimetry and X‐ray diffraction indicated that the copolymerization of PCLLA decreased the crystallinity of the polymers, and the results of transmission electron micrograph and laser light scattering (LLS) revealed that the prepared nanoparticles had a spherical shape, and the size of PCLLA nanoparticles (∼ 85 nm) was smaller than that of the PCL and PLLA nanoparticles. The experiment of in vitro drug release showed that the drug release rate from PCLLA nanoparticles was slower than that from PCL and PLLA nanoparticles, and the release profile of PCL6/LA4 nanoparticles appeared to follow zero order kinetics. These results suggested that the polymer composition made a great influence on the nanoparticle size and drug release behavior. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 874–882, 2000     

Photocatalytic and adsorptive treatment of 2,4-dinitrophenol using a TiO2 film covering activated carbon surface

Anatase titanium dioxide (TiO₂) in particle sizes of roughly 0.5–20 μm was prepared from amorphous TiO₂ in an aqueous H₂O₂ solution by heating at 90 °C for 9 h and directly deposited on a PET film. On the other hand, granular activated carbon (AC) particles in sizes of 1–2 mm in diameter were adhesively deposited on a PET film, and their surfaces were also coated with TiO₂. The resulting three preparations (TiO₂-, AC-, and TiO₂/AC-PET films) were set up in an annular-flow reactor to treat aqueous solutions of 2,4-dinitrophenol (DNP) in a batch-recirculation mode. The rate of DNP adsorption onto the TiO₂/AC-PET film without UV irradiation was almost the same as that onto the AC-PET film, indicating that the attraction of DNP to AC was not lowered in the presence of TiO₂ film. Observation of SEM photographs suggests that this result is attributed to the porous structure of the thin TiO₂ film covering AC particles. The rate of DNP removal by the TiO₂-AC PET film under UV irradiation was 2.9 times higher than that by the TiO₂-PET film under UV irradiation, and was 1.1 times higher than the rate of DNP adsorption onto the AC-PET film. The rate of DNP removal by the AC-PET film decreased by 40% after six runs, while that by the TiO₂/AC-PET film decreased by 22%. Durable experiments using the TiO₂/AC-PET and AC-PET films clarified that the lifetime of the TiO₂/AC-PET film is at least two times longer than that of the AC-PET film. This result suggests that DNP molecules are photocatalytically decomposed when passing through the porous TiO₂-PET film, which lessens a burden of DNP adsorption on AC. Moreover, the DNP treatments in the batch-recirculation flow system suggested that the TiO₂/AC-PET film saturated with DNP can be successfully regenerated at 60 °C.     

Rattle‐Structured Ag/TiO2 Nanocomposite Capsules with Bactericide and Photocatalysis Activities

A structural design featuring rattle‐type silver/titania (Ag/TiO₂) core/shell, that is, Ag@TiO₂, composite microcapsules is produced. The TiO₂ shell protects the encapsulated, movable Ag nanoparticles from breaking away under moderate loading, minimizing hence adverse environmental and biological exposure due to the metal loss, whereas the mesoporous shell serves as conduits for Ag ions released from the caged Ag nanoparticles to kill Escherichia coli in aqueous solutions under dark condition. The anatase TiO₂ shell imparts an additional, synergistic photocatalysis activity under ultraviolet irradiation. A pronouncedly enhanced photocatalysis activity results when the Ag@TiO₂ composite capsules were thermally annealed under vacuum. This “rattle‐in‐ball” hybrid architecture enables bifunctional bactericide and photocatalysis capability under both light and dark conditions, as well as mitigated environmental and biological impact in practical use.     

改性活性碳纤维对CO2的吸附性能

为了进一步提高活性碳纤维的CO₂吸附量和抗水性能,采用浸渍法将活性碳纤维进行改性处理,得到一系列改性样品,并对其进行了SEM和FTIR表征。研究了活性碳纤维种类、浸渍试剂（NaOH溶液、ZnCl₂溶液及离子液体）等对吸附剂孔结构、CO₂吸附量、循环使用性和抗水性能的影响,并探讨了CO₂在改性活性碳纤维内的动力学吸附扩散行为。研究结果表明：改性活性碳纤维的CO₂吸附性能和抗水性能均显著改善,其中CO₂最高吸附量达24.4%（0.1MPa和25℃）,吸湿率减小到1.33%,且具有良好的吸附/脱附循环使用性。均相扩散模型（HSDM）描述了实时吸附数据,此模型能够较好地反映CO₂在样品内的扩散行为,改性活性碳纤维仍能保持良好的扩散速率,扩散系数D_s值数量级为10^-5m²/s,与空白活性碳纤维相当。