室温条件下乙腈为溶剂炭气凝胶的制备与机理分析

与传统炭气凝胶制备不同,在室温条件下以乙腈为溶剂,间苯二酚和甲醛为前驱体,盐酸为催化剂,采用溶胶-凝胶、超临界干燥结合高温炭化工艺制备炭气凝胶(密度低至约50 mg.cm-3)。红外光谱、比表面积和孔径分布、扫描电子显微镜(SEM)和X射线衍射等测试表明,所制炭气凝胶是一种类石墨结构的非晶态材料,具有纳米骨架网络结构,比表面积达1 300 m2.g-1。对比不同配比气凝胶的SEM发现,气凝胶的颗粒尺寸为40 nm～70 nm。分析溶胶-凝胶过程中的温度变化和乙腈在凝胶化中作用得知,由于盐酸的催化和反应放热共同作用,实现了室温下间苯二酚和甲醛的加成和缩聚反应,并最终形成凝胶;乙腈在反应中起着一种分散剂的作用。     

Influence of polarity on filling polymer molecules into carbon nanotubes

Using molecular dynamics (MD) simulation, we studied the influence of polarity of polymer chains and modified single-walled nanotubes (SWNTs) on filling polymer chains into SWNTs. The center of mass (COM) distance and the interaction energy between the polymer molecules and SWNTs, as well as non-bond energy (including van der Waals energy and electrostatics energy) differences (ΔE) between initial structure and final structure in the SWNTs–polymers systems were calculated. The simulations indicate that both the polarity of polymer molecules and the polarity of modified groups attached to SWNTs can obstruct filling polymer chains into SWNTs. The general conclusions may be of importance in the production of high-performance SWNTs–polymers nanocomposites and have important theoretical significance on the application of carbon nanotubes as drug carrier and transportation channels.     

High rate capability of ordered mesoporous carbon with platelet graphitic pore walls for lithium ion anodes

An ordered mesoporous carbon (OMC) with controllable molecule crystal and platelet graphitic pore walls, which is directionally grown on the internal pore walls of SBA-15 or anchors at liquid/silica interfaces by molecule engineering, has been investigated as lithium ion anodes. It is found that the OMC exhibits high kinetics, rate and cycling performance. The i₀ and D_Li are almost constant after 50 cycles. OMC shows a high reversible specific capacity of 153.9 mAh g^-1 at the current density as high as 3500 mA g^-1. The excellent electrochemical performance could be attributed to the presence of the porosity and platelet graphitic pore walls.     

The growth of amorphous and graphitic carbon layers under ion bombardment in an rf plasma

Methods of preparing C-films from energetic C-ions and from ion impact bombardment of hydrocarbon species are reviewed. It is shown that amorphous C-deposits resulting from impact damage can have dielectric properties and be exceptionally hard. The rf plasma technique used to grow a-C-films on a negatively biased target is described and the effects of temperature rise on structural change is followed using differential scanning calomimetry. The as-grown films contain absorbed hydrogen which produces compressive stress and is released to form gas bubbles at 400°C.     

Simple and efficient CVD synthesis of graphitic P-doped 3D cubic ordered mesoporous carbon at low temperature with excellent supercapacitor performance

Heteroatom doping is a promising strategy for improving the electrochemical performance of carbon materials. Herein, we spotlight an advantageous, simple, and efficient CVD synthesis of P-doped 3D cubic ordered mesoporous carbon (POMC) for the first time. The POMC was prepared by pyrolysis of acetylene/triphenylphosphine (C₂H₂/Ph₃P) mixture at relatively low temperature over Fe-KIT-6 as a sacrificial template. The ensuing P-doped OMC showed an enhanced porous texture than an undoped counterpart with a specific surface area of 403.5 m²/g, pore volume of 0.545 cm³/g, average pore size of 4.64 nm and suitable heteroatom functionalities with P and O contents of 0.13% and 9.83%, correspondingly. The obtained POMC exhibited a much higher specific capacitance of 288F/g at 0.2 A/g (175F/g for OMC), good cyclic stability of 97.6 %, and good rate capability than pristine OMC in 6 M KOH. It is equivalent to or improved than various stated mono doped and even dual doped porous carbon electrodes. Furthermore, a symmetric supercapacitor (POMC//POMC) was fabricated with 1 M Na₂SO₄ aqueous neutral electrolyte exhibits high cycling stability (89.3%) even with a wide potential window (2.0 V) and offers a relatively high energy density (10.01 Wh/kg) with a power density of 300 W/kg.     

溶剂尺度对MOF-808结构及性能影响

以不同溶剂尺度的酰胺类溶剂与甲酸混合溶液为溶剂模板,利用溶剂热法制备MOF-808。利用傅里叶变换红外光谱仪、扫描电镜、X-射线衍射仪和比表面积分析仪对样品进行性能表征。结果表明,溶剂尺度越小,MOF-808孔径越小,比表面积越大,N_2吸附性能越强。当甲酰胺/甲酸混合溶液作为溶剂模板时,MOF-808孔径最小,为1.19nm;比表面积最大,达到1625m²/g。     

温度对磁流变液流变性能的影响研究

为了保证磁流变液的可靠应用,采用实验方法,系统研究了温度对磁流变液流变性能的影响,分析了磁流变液的热沉降稳定性、热磁化强度、热表观粘度、热膨胀性以及热屈服应力,研究表明,温度对磁流变液流变特性均存在一定影响,在120℃时,其稳定沉降率较室温增加11%;在100℃以内,热磁化强度变化较小,而在300℃时热磁化强度降低16%;其表观粘度变化规律与基载液的粘温特性密切相关;在220℃时磁流变液热膨胀率达到18%,热膨胀率较高;温度升高,其剪切屈服应力变化显著,220℃时较室温剪切屈服应力降低了15%。     

Fe3O4纳米粒子作为催化剂和致孔剂制备高比表面积块体石墨化炭

报道了一种以Fe3O4纳米晶粒为催化剂和致孔剂制备具有高比表面积块体石墨化炭的方法.首先采用共沉淀法合成粒径＜10nm的Fe3O4纳米颗粒,然后将其均匀分散到以2,4-二羟基苯甲酸(D)、甲醛(F)为原料,无水Na2 CO3为催化剂形成的聚合物(DF)中,通过溶胶-凝胶过程和炭化过程得到掺杂Fe的石墨化炭.最后经过酸洗,得到纯的高比表面积块体石墨化炭.随炭化温度的升高(700℃～900℃),样品的石墨化程度增加.在800℃炭化,样品已具有明显的石墨化结构,且比表面积较大.     

Laser-induced dissociation/high-energy collision-induced dissociation fragmentation using MALDI-TOF/TOF-MS instrumentation for the analysis of neutral and acidic oligosaccharides

Producing detailed mass spectrometric fragmentation data of native oligosaccharides for the purpose of basic structure elucidation has become a readily accessible tool since the availability of enhanced technical equipment. In this report, high-energy collision-induced dissociation (heCID) in combination with MALDI-TOF/TOF technology for analysis of native neutral and acidic oligosaccharides is described. By providing complementary data, heCID-MALDI-TOF/TOF adds a variety of valuable cross-ring fragmentation information to the information of glycosidic fragmentation obtained preferably by laser-induced dissociation (LID). We examined parameters influencing fragmentation behavior of both-acidic and neutral-compounds. Results show a dependency of the fragmentation pattern for the employed matrix as well as the laser intensity provided for the ionization of the analytes and the complexity of the analytes. Due to instrument-specific settings, protonated glycosidic ion series within spectra of sodiated compounds could also be identified. Furthermore, acquired spectra could be readily used to identify compounds by comparison to existing glycan databases such as GlycoSuiteDB and GlycosciencesDB. The results show a better scoring of heCID data sets in comparison to LID-derived data. heCID-MALDI-TOF/TOF analysis in combination with database search algorithms is demonstrated to be suitable for an initial identification/classification of carbohydrates.     

Influence of high temperature and high acidic conditions on geopolymeric composite material for steel pickling tanks

Traditionally, most equipment that was used for containing corrosive solutions and fumes for the steel industry was fabricated from steel with a rubber-lined interior. An additional acid-resistant brick lining was used to protect the rubber lining and also to act as thermal insulation. This investigation focussed on a geopolymer material that would simultaneously solve the two issues, recurrent acid leakage from the brick-lined structure and minimal thermal stress during operation. The scope of this project was limited to identify the extent of weight loss in a strong HCl acidic environment for a standard geopolymeric composite at 90 °C. Accelerated tests on geopolymer samples were conducted over 110 days and the weight loss results were extrapolated over a time period of 300 days. Visual inspection showed that OPC had a reduced diameter after 40 days of acid exposure, and therefore, the overall acid penetration for OPC was significantly higher than GPC. The mechanism of weight loss or material degradation was not the key aim in this investigation, rather we aimed to obtain a new composition to withstand highly acidic condition (which are not encountered with ordinary Portland cement (OPC) concrete, e.g. in sewage conditions). The average weight loss of a theoretical slab of geopolymer sample in accelerated test conditions (90 °C and 22% HCl) is found to be 1.8 wt% in 60 days for single-face exposure and the average thickness loss predicted for a 40 mm thick slab is about 3.5% after 300 days of exposure in operating conditions of 18% HCl and 80 °C after reaching steady-state weight loss. This is significantly better compared to a standard concrete and brick slab or steel-lined rubber slab. This initial investigation indicated that with further scientific investigation and understanding of the material, the application could be broadened to further minimise acid corrosion over longer time periods (10 years).     

Influence of solvent composition on the performance of carbodiimide cross-linked gelatin carriers for retinal sheet delivery

Gelatin is a protein molecule that displays bioaffinity and provides a template to guide retinal pigment epithelial (RPE) cell organization and growth. We have recently demonstrated that the carbodiimide cross-linked gelatin membranes can be used as retinal sheet carriers. The purpose of this work was to further determine the role of solvent composition in the tissue delivery performance of chemically modified biopolymer matrices. The gelatin molecules were treated with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) in the presence of binary ethanol/water mixtures with varying ethanol concentrations (70–95 vol%) to obtain the carriers with different cross-linking efficiencies and mechanical properties. Results of melting point measurements and in vitro degradation tests showed that when the cross-linking index reached a high level of around 45 %, the EDC cross-linked gelatin materials have sufficient thermal stability and resistance to enzymatic degradation, indicating their suitability for the development of carriers for retinal sheet delivery. Irrespective of the solvent composition, the chemically modified gelatin samples are compatible toward human RPE cells without causing toxicity and inflammation. In particular, the membrane carriers prepared by the cross-linking in the presence of solvent mixtures containing 80–90 vol% of ethanol have no impact on the proliferative capacity of ARPE-19 cultures and possess good efficiency in transferring and encapsulating the retinal tissues. It is concluded that, except for cell viability and pro-inflammatory cytokine expression, the retinal sheet delivery performance strongly depends on the solvent composition for EDC cross-linking of gelatin molecules.     

Enhancement of the quality of MALDI mass spectra of highly acidic oligosaccharides by using a nafion-coated probe

Spectra of highly acidic oligosaccharides obtained by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) can be greatly enhanced in quality by coating the MALDI probe surface with a film consisting of a perfluorosulfonated ionomer (Nafion) prior to the addition of the sample-matrix mixture. For comparison, three mixtures containing highly acidic oligo- and polysaccharides derived from partial acidic hydrolysis of alginate, pectin, or carboxymethyl cellulose (CMC) were analyzed by employing probes with an uncoated gold surface or a surface coated with a Nafion or nitrocellulose film. The negative ion-mode MALDI spectra of the oligouronates (oligomers containing mannuronic/guluronic and galacturonic acid residues) obtained using uncoated or nitrocellulose-coated probes consisted of a series of broad, multiple peaks. These multiple peaks were assigned to the molecular ions of the nondissociated [M - H]- and partially sodiated [MnNa - H]-, where n = 1, 2, or 3, oligomers. In contrast, the corresponding spectra obtained with Nafion-coated probes contained only a single series of sharp peaks originating from the molecular ions ([M - H]-) of nondissociated oligomers exhibiting chain lengths of as many as approximately 15 uronic acid residues. The Nafion coating was apparently capable of removing the sodium counterions remaining in the deposit of the sample-matrix mixture on the probe, thereby greatly enhancing the signal-to-noise ratios of the peaks in the spectra. In a similar manner, higher quality spectra could also be obtained by using Nafion-coated probes for analysis of the oligouronates and CMC oligomers by positive ion-mode MALDI-MS.     

Spectroscopic ellipsometry characterization of amorphous carbon and amorphous, graphitic and fullerene-like carbon nitride thin films

Carbon nitride (CN_x) and amorphous carbon (a-C) thin films are deposited by reactive magnetron sputtering onto silicon (001) wafers under controlled conditions to achieve amorphous, graphitic and fullerene-like microstructures. As-deposited films are analyzed by Spectroscopic Ellipsometry in the UV-VIS-NIR and IR spectral ranges in order to get further insight into the bonding structure of the material. Additional characterization is performed by High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Between eight and eleven resonances are observed and modeled in the ellipsometrically determined optical spectra of the films. The largest or the second largest resonance for all films is a feature associated with C-N or C-C modes. This feature is generally associated with sp³ C-N or sp³ C-C bonds, which for the nitrogen-containing films instead should be identified as a three-fold or two-fold sp² hybridization of N, either substituted in a graphite site or in a pyridine-like configuration, respectively. The π→π? electronic transition associated with sp² C bonds in carbon films and with sp² N bonds (as N bonded in pyridine-like manner) in CN_x films is also present, but not as strong. Another feature present in all CN_x films is a resonance associated with nitrile often observed in carbon nitrides. Additional resonances are identified and discussed and moreover, several new, unidentified resonances are observed in the ellipsometric spectra.     

Preparation of 2D graphitic carbon nitride nanosheets by a green exfoliation approach and the enhanced photocatalytic performance

In this paper, we reported a new and environment-friendly strategy to exfoliate graphitic carbon nitride (CN) in hot water to obtain ultrathin CN nanosheets (CNNS). By thermal treating, water molecules were intercalated into the interlayer space of bulky CN and further hydrolyzed the bridge-linked N groups between tri-s-triazine units, thereby cutting the CN layers into CNNS. Due to the negative charges on surface (Zeta potential was ?13 mV at pH 7), the CNNS colloids were extremely stable. The physicochemical characterization indicated that the as-prepared CNNS had a typical 2D morphology with a ~1.2 nm thickness and numerous –OH groups on surface. Moreover, the high charge separation and transport ability were achieved in CNNS because of the retaining of conjugated CN system. Compared to the bulk CN, the as-prepared ultrathin CNNS exhibited an enhanced photocatalytic performance (four times higher than that of the bulk CN) for degradation of organic dye under visible light irradiation. Additionally, the superior reusability and the excellent generality of CNNS for decomposing other pollutants were also demonstrated. Finally, we proposed a possible mechanism of CNNS based on the examined band structure and the main active species determined by quenching of various active species.     

锂离子电池碳纳米管负极材料储锂性能研究

将碳纳米管用于锂离子电池负极材料,用循环伏安及充放电实验研究了电极的性能.结果表明,碳纳米管用作锂离子电池负极,具有较高的储锂容量,首次放电容量达560mAh/g,但首次不可逆容量损失也大,高达430mAh/g.经过第1次充放电的容量损失后,随后各次的容量损失很小,碳纳米管的循环性能趋于稳定.     

Effects of carbon readsorption on tungsten under high-flux, low-energy Ar ion irradiation at elevated temperature

The erosion kinetics under irradiation by Ar ions extracted from plasma by 300 V negative bias voltage of 2 μm-thick W film contaminated by redeposited carbon atoms was investigated in dependence on the Ar-working gas pressure in the range 0.2-10 Pa at 410 K. The erosion and deposition parameters were deduced from the dependence of the sample's weight change on irradiation time. Two regimes were distinguished which contributed differently to the carbon transport efficiency from the surface towards the bulk, namely, the weight-decrease regime, when sputtering prevailed redeposition, and the weight-increase regime, when redeposition prevailed sputtering. Carbon distribution profiles measured by the SIMS technique showed that carbon was efficiently transported into the W film when its surface was not covered by a continuous amorphous C layer. The C transport efficiency decreased when W was covered by a continuous amorphous C film.These results were qualitatively explained by dynamic mixing of atoms on the surface. It was assumed that surface chemical potential increased under irradiation and that C adatoms were driven into grain boundaries of nanocrystalline W film. The continuous amorphous C film on tungsten blocked the access of activated C atoms to the grain boundaries.