XRD,TEM and thermal analysis of Fe doped boehmite nanofibres and nanosheets

Iron doped boehmite nanofibres with varying iron content have been prepared at low temperatures using a hydrothermal treatment in the presence of poly(ethylene oxide) surfactant. The resultant nanofibres were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). TEM images showed the resulting nanostructures are predominantly nanofibres when Fe doping is no more than 5%; in contrast nanosheets were formed if Fe doping was above 5%. For the 10% Fe doped boehmite, a mixed morphology of nanofibres and nanosheets were obtained. Nanotubes instead of nanofibres were observed in samples with 20% added iron. The Fe doped boehmite and the subsequent nanofibres/nanotubes were analysed by thermogravimetric and differential thermogravimetric methods. Boehmite nanofibres decompose at higher temperatures than non-hydrothermally treated boehmite and nano-sheets decompose at lower temperatures than the nanofibres.     

Synthesis, characterization, and surface properties of iron-doped boehmite nanofibers

Iron-doped boehmite nanofibers with varying iron contents have been prepared at low temperatures using hydrothermal treatment in the presence of poly(ethylene oxide) surfactant. The resulting nanofibers were characterized by transmission electron microscopy (TEM), X-ray diffraction, energy-dispersive X-ray analysis, and N2 adsorption. TEM images showed that the resulting nanostructures are predominantly nanofibers when the doped iron content is less than 5% (mol/mol); in contrast, nanosheets were formed when iron doping was above 4%. Nanotubes instead of nanofibers and iron-rich particles were observed in samples with 20% added iron. A detailed characterization and discussion on the iron-doped nanofibers is presented.     

Synthesis and surface characterization of yttrium doped boehmite nanofibers

Yttrium doped boehmite nanofibers with varying yttrium content have been synthesized at low temperatures using a soft-chemistry route in the presence of polyglycol ether surfactant. The effect of yttrium content, hydrothermal temperature on the growth of boehmite nanostructures was systematically studied. Nanofibers were formed in all samples with varying doped Y% treated at 100 °C; large Y(OH)₃ crystals were also formed at high yttrium doping. Treated at an elevated temperatures resulted in a remarkable changes in size and morphology for samples with the same doped Y content. The resultant nanofibers were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray analysis (EDX), N₂ adsorption and thermogravimetric analysis. The detailed characterization and discussion on the Y doped nanostructures are presented.     

Tuning the Surface Structure of Nitrogen‐Doped TiO2 Nanofibres—An Effective Method to Enhance Photocatalytic Activities of Visible‐Light‐Driven Green Synthesis and Degradation

Nitrogen‐doped TiO₂ nanofibres of anatase and TiO₂(B) phases were synthesised by a reaction between titanate nanofibres of a layered structure and gaseous NH₃ at 400–700 °C, following a different mechanism than that for the direct nitrogen doping from TiO₂. The surface of the N‐doped TiO₂ nanofibres can be tuned by facial calcination in air to remove the surface‐bonded N species, whereas the core remains N doped. N‐Doped TiO₂ nanofibres, only after calcination in air, became effective photocatalysts for the decomposition of sulforhodamine B under visible‐light irradiation. The surface‐oxidised surface layer was proven to be very effective for organic molecule adsorption, and the activation of oxygen molecules, whereas the remaining N‐doped interior of the fibres strongly absorbed visible light, resulting in the generation of electrons and holes. The N‐doped nanofibres were also used as supports of gold nanoparticle (Au NP) photocatalysts for visible‐light‐driven hydroamination of phenylacetylene with aniline. Phenylacetylene was activated on the N‐doped surface of the nanofibres and aniline on the Au NPs. The Au NPs adsorbed on N‐doped TiO₂(B) nanofibres exhibited much better conversion (80 % of phenylacetylene) than when adsorbed on undoped fibres (46 %) at 40 °C and 95 % of the product is the desired imine. The surface N species can prevent the adsorption of O₂ that is unfavourable for the hydroamination reaction, and thus, improve the photocatalytic activity. Removal of the surface N species resulted in a sharp decrease of the photocatalytic activity. These photocatalysts are feasible for practical applications, because they can be easily dispersed into solution and separated from a liquid by filtration, sedimentation or centrifugation due to their fibril morphology.     

Pd nanoparticles immobilized on boehmite by using tannic acid as structure-directing agent and stabilizer: a high performance catalyst for hydrogenation of olefins

Boehmite-supported Pd nanoparticles (Pd–TA–boehmite) were successfully synthesized by a hydrothermal method using tannic acid as the structure-directing agent as well as stabilizer. The physicochemical properties of the Pd–TA–boehmite catalyst were well characterized by XPS, XRD, N₂ adsorption/desorption, and TEM analyses. Catalytic hydrogenation of olefins was used as the probe reaction to evaluate the activity of the Pd–TA–boehmite catalyst. For comparison, the Pd–boehmite catalyst prepared without tannic acid was also employed for olefin hydrogenation. For all the investigated substrates, the Pd–TA–boehmite catalyst exhibited superior catalytic performance than the Pd–boehmite catalyst. For the example of hydrogenation of allyl alcohol, the initial hydrogenation rate and selectivity of the Pd–TA–boehmite catalyst were 23,520 mol/mol h and 99 %, respectively, while those of the Pd–boehmite catalyst were only 14,186 mol/mol h and 93 %, respectively. Additionally, the hydrogenation rate of the Pd–TA–boehmite catalyst could still reach 20,791 mol/mol h at the 7th cycle, which was much higher than that of the Pd–boehmite catalyst (5,250 mol/mol h) at the 4th cycle, thus showing an improved reusability.     

Evaluation and correlation of electrochemical and mechanical properties of PVA/SA nanofibres

The present study evaluates and correlates the morphology of poly (vinyl alcohol) (PVA) and sodium alginate (SA) nanofibres with their internal structure to determine dielectric and tensile properties for future applications as long-lasting and resistant cell scaffolds. This work generates electrospun nanofibres mixing SA concentration in a PVA solution cross-linked in calcium chloride media. The dielectric properties of the nanofibres that were obtained using electrochemical impedance spectroscopy (EIS) show that at higher amount of SA in the PVA/SA fibres, the cross-linking process occurs at shorter times, indicating the modification of the internal structure of the PVA/SA. The X-ray photoelectron spectra (XPS) demonstrate that the chemical composition of the nanofibres varies depending on the depth profile. The transmission electron microscopy (TEM) proves that the PVA/SA is formed as a core-shell coaxial nanofibre. The tensile testing demonstrates that with a higher SA concentration, the mechanical properties show brittleness.     

胶溶法制备镧-钡共稳定氧化铝的性能

以硝酸为胶溶剂, 两种拟薄水铝石为前驱体, 用胶溶法制备了镧-钡共稳定的氧化铝. 采用X 射线衍射(XRD)、表面分析仪(BET)、氨气程序升温脱附(NH3-TPD)和NO2程序升温脱附(NO2-TPD)技术对所制备的镧改性和镧钡共改性氧化铝的结构特性和表面性能进行了表征. XRD结果表明, 改性氧化铝在1273 K焙烧后均以γ-Al2O3相存在. 当BaO添加量达到14%(w)时, 有少量BaCO3生成. BET结果表明, 在1273 K下焙烧5 h后, 5%(w)La2O3稳定的氧化铝(Ba-0)和5%La2O3与8%BaO共同稳定的氧化铝(Ba-8)均具有较大的比表面积, 各种氧化铝的吸附等温线表明它们的孔形状均为狭缝型孔和瓶型孔, 孔径分布曲线表明, 仅有样品Ba-8的孔径分布较宽, 孔径为6-10 nm, 其它三种样品的孔径均集中在10 nm; NH3-TPD结果表明, 随着氧化钡添加量的逐渐增多, 氧化铝表面的酸量、酸强度逐步减少. NO2-TPD结果表明, 添加BaO后载体对NO2的吸附量增多, 随着BaO含量的增多, 体相Ba(NO3)2增多. 由于样品Ba-8同时具有很好的织构性质、适中的表面酸量和酸强度分布及NO2吸附脱附能力, 使得以它为载体的催化剂具有最好的催化性能,丙烷的起燃温度和完全转化温度分别为526 K和593 K.     

Thermal and morphological study of Al2O3 nanofibers derived from boehmite precursor

The boehmite nanofibers were prepared by using NaAlO₂ and Al₂(SO₄)₃ as the starting materials without any surfactant. The phase transitions of the boehmite nanofibres against different temperature were studied and various phases were derived from well-crystallized boehmite nanofibers. All these phases had the same morphology even after high temperature calcination. In addition, the retention of specific surface area of the samples were very high because of the limited aggregation occurred in calcinations for each sample. For instance, the ??-Al₂O₃ obtained at 500?°C had the specific surface area (208.56?m²/g) with an average pore diameter of 6.0?nm. With the further increase of the calcination temperature, the nanofibers became shorter and coarsening, which resulted in the decrease of the specific surface area. It is worthwhile to notice that the BET surface areas (40.97?m²/g) and the pore volume (0.27?cm³/g) of the fibrous structures obtained after 1200?°C calcination are substantially higher than that of the non-fibrous alumina because of the morphology maintenance.     

Preparation and characterization of diphasic sol-gel derived unsupported mullite membranes

Diphasic gels prepared by mixing freshly prepared polymeric silica and polymeric boehmite sols through a modified Al-alkoxide route in mullite compositions led to the crystallization of mullite upon heat treatment at 775 °C. Mullite formation was observed at a 100 °C higher temperature when diphasic gels were formed by mixing aged polymeric sols containing about 2 nm in diameter boehmite species. These relatively low mullite formation temperatures were attributed to the nanoscale sizes of the polymeric species of the two amorphous phases present in the diphasic gels.     

负载Cu氧化铝纳米管合成及在NO+CH4反应中催化性能研究

采用过氧化氢调节反应条件,在水热体系中合成了新型的勃姆石纳米管,经520℃焙烧2h后,晶型由AlOOH转化为γ-Al2O3;采用XRD、氮吸附、TEM等对合成的纳米管进行表征.结果表明,合成的γ-Al2O3纳米管长约300nm,外径20nm,比表面积达到230m2/g以上.以此为载体,采用等体积浸渍法用Cu(NO3)2...     

Sodium-doped lithium zirconate nano squares: synthesis,characterization and applications for CO<Subscript>2</Subscript> sequestration

Nano squares of sodium-doped lithium zirconate have been synthesized by a simple citrate based sol–gel method at room temperature in the presence of cetyl trimethylammonium bromide (CTAB) as a surfactant. The structural and morphological properties were investigated by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) respectively. XRD analysis of sample calcined at 900 °C for 4 h shows the formation of monoclinic lithium zirconate phase. The TEM shows the interesting morphology of formation of nano squares of sodium doped lithium zirconate sample. The carbon dioxide sorption capacity was carried out by TGA analysis at different high temperatures. It is observed that the sample shows ~20 wt% carbon dioxide sorption at higher temperature (650 °C) within 20 min which are better than the known reports.     

Efficient removal of partially hydrolysed polyacrylamide in polymer-flooding produced water using photocatalytic graphitic carbon nitride nanofibres

In this work, graphitic carbon nitride (GCN) photocatalyst-incorporated polyacrylonitrile (PAN) nanofibres (GCN/PAN nanofibres) were successfully prepared using electrospinning technique. The physicochemical properties of the fabricated GCN/PAN nanofibres were analysed using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), elemental analyser, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV–vis–NIR spectroscopy. The photocatalytic degradation by GCN/PAN nanofibres exhibited 90.2% photodegradation of partially hydrolysed polyacrylonitrile (HPAM) after 180 min under UV light irradiation in a suspension photocatalytic reactor. The results suggest that the photodegradation of HPAM contaminant by GCN/PAN nanofibres was due to the synergetic effects of HPAM adsorption by the PAN nanofibres and HPAM photodegradation by the GCN. This study provides an insight into the removal of HPAM from polymer-flooding produced water (PFPW) through photocatalytic degradation of liquid-permeable self-supporting nanofibre mats as a potentially promising material to be used in industrial applications.     

Y掺杂的ZnO纳米纤维材料的制备及其气敏传感器作用机理

采用静电纺丝法成功制备了Y掺杂的ZnO纳米纤维.并通过X射线衍射(XRD),扫描电子显微镜(SEM),能量色散X射线(EDX),透射电子显微镜(TEM)以及热重差热分析(TG-DTA)等手段对样品的结构和形貌进行了表征分析.同时用纯的ZnO和Y掺杂的ZnO纳米纤维制备了传感器,对浓度为(1-200)×10^-6 (体积分数)丙酮的气敏特性进行了测试分析.测试结果表明,可以通过简单控制纳米纤维中Y的含量,来微调该传感器的气敏特性.同时也发现通过Y掺杂, ZnO纳米纤维对丙酮的气敏特性有所改善,表现出很高的响应.纯ZnO和Y掺杂ZnO制成的传感器对几种潜在干扰气体表现出良好的选择性,比如氨气、苯、甲醛、甲苯以及甲醇.本文最后也讨论了该传感器的气敏作用机理.     

Linear low‐density polyethylene nanocomposites by in situ polymerization using a zirconium‐nickel tandem catalyst system

A series of linear low‐density polyethylene (LLDPE) nanocomposites containing different types of nanofiller (TiO₂, MWCNT, expanded graphite, and boehmite) were prepared by in situ polymerization using a tandem catalyst system composed of {Tp^Ms}NiCl ( 1 ) and Cp₂ZrCl₂ ( 2 ), and analyzed by differential scanning calorimetry, dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). Based on these analyses, the filler content varied from 1.30 to 1.80 wt %. The melting temperatures and degree of crystallinity of the LLDPE nanocomposites were comparable to those of neat LLDPE. The presence of MWCNT as well as boehmite nucleated the LLDPE crystallization, as indicated by the increased crystallization temperature. The DMA results showed that the presence of TiO₂, EG, and CAM 9080 in the LLDPE matrix yielded nanocomposites with relatively inferior mechanical properties compared to neat LLDPE, suggesting heterogeneous distribution of these nanofillers into the polymer matrix and/or the formation of nanoparticle aggregates, which was confirmed by TEM. However, substantial improvement in the storage modulus was achieved by increasing the sonication time. The highest storage modulus was obtained using MWCNT (1.30 wt %). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3506–3512     

General synthesis and aggregation behaviour of new single-chain bolaphospholipids: variations in chain and headgroup structures

The chemical structures of polymethylene-1,omega-bis(phosphocholines) that self-assemble into nanofibres was modified on the one hand in the hydrophobic chain region, by introduction of sulfur and oxygen atoms, and on the other hand by variation of the polar headgroup structure with functionalised tertiary amines. The temperature-dependent self-assembly of these novel bolaphospholipids into nanofibres and spherical micelles was investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The thermal stabilities of the nanofibres strongly depend on the chemical compositions of the headgroups and of the hydrophobic chains. The insertion of new functionalities in the headgroup region by click chemistry makes these substances interesting for potential applications in bioscience and materials science.     

Boehmite nanorod‐reinforced‐polyethylenes and ethylene/1‐octene thermoplastic elastomer nanocomposites prepared by in situ olefin polymerization and melt compounding

Nanocomposites of polyethylene (HDPE) and poly(ethylene‐co‐1‐octene) thermoplastic elastomers, both containing boehmites with variable sizes, shapes, and aspect ratios (1–20), were prepared by means of in situ olefin polymerization and melt compounding. The in situ olefin polymerization in the presence of boehmite nanorods afforded nanocomposites containing 4–8 wt % of boehmite. In an alternative process, the in situ olefin polymerization was used to produce polyolefins with high boehmite content of 50 wt % as masterbatches for polyolefin melt compounding with ethylene homo‐ and copolymers. The addition of the boehmite nanofillers improved the stiffness without sacrificing high elongation at break. The stiffness, as expressed by Young's modulus, increased with increasing boehmite aspect ratio. In case of thermoplastic elastomer nanocomposites the increase of stiffness was accompanied by a simultaneous increase of elongation at break. According to transmission electron microscopy (TEM), fine dispersion of the polar boehmite nanorods and nanoplatelets within the nonpolar hydrocarbon polymer matrix was obtained without requiring the addition of special dispersing agents or functionalized polyolefin compatibilizers. The comparison of melt compounding of polyethylene with boehmites or polyethylene/boehmite masterbatches revealed that compounding of masterbatches prepared by in situ polymerization filling afforded much finer and more uniform nanoboehmite dispersions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2755–2765, 2008     

Control of the morphology and particle size of boehmite nanoparticles synthesized under hydrothermal conditions

The spontaneous nucleation under hydrothermal conditions often leads to aggregation of crystallizing particles, which is an undesired phenomenon when the goal is the preparation of nanocrystals with narrow particle size distribution. The present paper reports on the synthesis of boehmite nanocrystals under hydrothermal conditions. An aqueous aluminum chloride salt solution was first prepared, and the pH was increased to 11 using a 5 M sodium hydroxide solution. The hydrothermal treatment was performed at 160 degrees C for different periods of time. The system yielded relatively small (15-40 nm) boehmite crystallites aggregated into larger (160 nm) particles. To avoid the aggregation, a biocompatible polymer, sodium polyacrylate (NaPa) 2100, was employed as a size-/morphology-controlling agent. Thus, stable colloidal suspensions of rounded boehmite nanoparticles having a size between 15 and 40 nm were obtained at 160 degrees C for 24 h. Further, the effect of synthesis time on the morphological features of boehmite synthesized in such a NaPa-containing system was investigated. The increase of the synthesis time from 24 to 168 h resulted in the formation of very long boehmite fibers (1000-2000 nm) with an average diameter of about 10 nm. The boehmite samples were characterized by XRD, DLS, TEM, IR, N2 adsorption, and zeta potential measurements. The colloidal stability of the obtained suspension was also studied.     

Long-term aging characteristics of atmospheric-plasma-treated poly(?-caprolactone) films and fibres

This paper reports the change in the surface properties and aging behaviours of surface-modified poly(?-caprolactone) films and nanofibres after atmospheric plasma treatment with a reactive gas. The morphologies, roughness, chemical bonding states, and surface energies of pristine and atmospheric-plasma-treated nanofibres were investigated. The nanofibres subjected to O₂ atmospheric plasma treatment showed higher surface roughness (∼88%), fibre diameter (∼14%), surface energy (∼19.2 times), and hydrophilicity (O/C atomic ratio, ∼43%) than did the pristine nanofibres. Over a 6-month period, the characteristics of the nanofibres isolated from air were not significantly altered; however, in the case of the nanofibres exposed to air, there was a subsequent increase in the surface roughness (∼82%), fibre diameter (∼7%), surface energy (∼27%), and hydrophilicity (O/C atomic ratio, ∼17.6%). We confirmed that the properties of the atmospheric-plasma-treated poly(?-caprolactone) nanofibres maintained for 6 months without exposure to air did not show any significant change. Consequently, these nanofibres would be well suited for biomedical applications that require long-term sample stability.     

勃姆石纤维增强二氧化硅气凝胶的制备及性能

以六水合氯化铝为铝源, 通过水热法制备勃姆石纤维; 以甲基三甲氧基硅烷和正硅酸乙酯为硅源共前驱体, 采用溶胶-凝胶法进而常压干燥制备了勃姆石纤维掺杂的二氧化硅复合气凝胶; 探究了勃姆石纤维的掺杂量对复合气凝胶性能的影响. 当勃姆石纤维的掺杂量(质量分数)为1%时, 气凝胶的机械性能最好, 能够承受17.1%的压缩应变, 最大压缩强度为1.12 MPa, 压缩模量高达2.57 MPa, 复合气凝胶在150 ℃仍然具有较低的导热系数(0.0670 W·m^?1·K^?1). 勃姆石纤维能够一定程度地抑制二氧化硅颗粒在高温下的烧结和相转变, 对二氧化硅气凝胶的耐高温性能有显著的提升作用, 复合气凝胶在1100 ℃高温热处理后, 仍能保持良好的隔热性能和较高的机械强度.     

Fabrication and vibrational energy harvesting characterization of flexible piezoelectric nanogenerator (PEN) based on PVDF/PZT

In this study, polyvinylidene difluoride (PVDF) is doped with different volume levels (10, 20, 30 vol %) of lead zirconate titanate (PZT), and neat PVDF (undoped) electrospun nanofibres are prepared by aligning them through the electrospinning process with a rotating drum collector. All of the produced nanofibres are characterized by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopy (FTIR). The piezoelectric nanogenerator (PEN) devices are fabricated by placing the PVDF/PZT electrospun nanofibres as the dielectric material between two conductive plates. The vibrational energy harvesting analyses of the PEN are defined by taking measurements under various resistive loads. At 15 Hz excitation frequency, the maximum output power of PEN with PVDF+10 vol %PZT reaches 6.35 μW by increasing the power to 85% under a resistive load of 1MΩ, while the PEN with β-PVDF has the electrical power of 3.44 μW at the same load. The PEN based energy generation is a promising source of clean energy generation from mechanical vibrations for powering portable microelectronic applications without an external power supply.