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.     

SUSPENSION PROPERTY OF ALUMINA IN LAPPING MEDIA

In order to understand the suspension properties of alumina grit in lapping liquids, with particular interest on their flocculation behavior both electro kinetic and sedimentation experiments were carried out on three different alumina powders, that were either wet or air classified in two commercial additives ( Mon - 60 and Rust Lick - 900 ). The results suggest that all three alumina powders have some acidic surface impurity and both Mon - 60 and Rust Lick - 900 are adsorbed on the alumina surface below pH 9. The sedimentation behavior of these alumina powders from their dispersions is independent of the classification of the alumina and nature of the additive but is dependent on the pH of the dispersion.     

液相色谱法测定动物源性食品中氯虫苯甲酰胺和氟虫酰胺残留量

采用高效液相色谱法测定动物源性食品中氯虫苯甲酰胺和氟虫酰胺的残留量。动物源性食品中的氯虫苯甲酰胺和氟虫酰胺,经乙酸乙酯和丙酮混合提取液提取后,过Al2O3柱净化,以乙腈:0.1mol/L的乙酸铵溶液(58:42)作为流动相,DAD检测器测定,外标法定量。测定结果表明:采用本方法检测氯虫苯甲酰胺和氟虫酰胺,检测限均可达到0.1mg/kg,在添加质量浓度0.1～2.0mg/L之间线性关系良好,相关系数(r)均>0.9990,对于0.1、0.2、0.5mg/kg水平添加回收率范围在72.3%～92.7%之间;相对标准偏差(RSDs)范围在3.0%～7.0%之间。     

Dynamic surface tension and surface rheology of biological liquids

The paper presents results of dynamic and equilibrium surface tension measurements (using a maximum bubble pressure instrument) of serum and urine samples that were obtained from 80 healthy human of various sexes and ages. These data were compared with surface tension measurements of biological liquids obtained from patients suffering from malignant neoplasm of corpus uteri (n=5) and cervix uteri (n=31). In addition, surface dilatational rheology was determined on 32 samples using a drop shape method. The dilatational rheology data were compared with the dynamic surface tension data. Although some trends were found, no significant correlations exist between surface tension and rheology data and any of the disease states or stages. It is difficult to explain these findings in the framework of known mechanisms. However, our studies demonstrate that dynamic interface tensiometry of human biological liquids provide new insight into the biophysical behavior of these liquids, most likely reflecting compositional changes of them during ageing, the course of cancer and as a consequence of therapeutical interventions.     

Wetting of CVD carbon films by polar and nonpolar liquids and implications for carbon nanopipes

The handling, dispersion, manipulation, and functionalization of carbon nanotubes and nanopipes often require the use of solvents. Therefore, a good understanding of the wetting properties of the carbon nanotubes is needed. Such knowledge is also essential for the design of nanotube-based nanofluidic devices, which hold the promise of revolutionizing chemical analysis, separation, drug delivery, filtration, and sensing. In this work, we investigated the wetting behavior of individual nanopipes produced by the chemical vapor deposition (CVD) of carbon in porous alumina templates and of thin carbon films produced by the same technique. The carbon pipes and films have the same chemistry and structure as determined by Raman and infrared spectroscopies and, when similarly treated, demonstrate the same qualitative wetting behavior, as determined by optical microscopy. Thus, measurements conducted on the carbon film surface are relevant to the nanopipes. In the case of the nanopipes, filling with various liquids was monitored. Contact angle experiments with both polar (water, glycerol, ethylene glycol, ethanol, tetra-hydro furan, and 2-propanol alcohol) and nonpolar liquids (cyclohexane, hexadecane, poly(dimethylsiloxane), and a fluoro-silicone) were conducted on films using the sessile drop method. The contact angles on the CVD carbon films ranged from 0 to 79 degrees. The exposure of the carbon films to a NaOH solution, typically used to dissolve the alumina template, led to a significant decrease of the contact angle, especially in the case of polar liquids.     

Flow field-flow fractionation-inductively coupled plasma mass spectrometry of chemical mechanical polishing slurries

Alumina- and silica-based chemical mechanical polishing slurries were analyzed to demonstrate the feasibility of field-flow fractionation-inductively coupled plasma mass spectrometry (FFF-ICP-MS). After FFF separation ²⁷Al and ²⁹Si were measured by ICP-MS to obtain size distributions, mean particle size, number average-, mass average-, Z average- diameters, minimum and maximum particle sizes, dominant particle size, and particle size ranges (breadth of size distribution, and polydispersity) characteristics. Five commercial alumina and 13 silica slurry samples were characterized. Broad distributions were detected and two polydispersity calculations were compared. Most silica samples and one alumina sample show monomodal normal distributions. Asymmetric distributions were observed for a few silica and most alumina slurries. The degree of deviation from normal distribution was assessed. Mean particle sizes of alumina slurries varied between 150 and 350 nm with the maximum detected particle of less than 680 nm. Silica slurries exhibited maximum particle sizes of less than approximately 400 nm with the mean particle sizes ranging from 110 to 220 nm. Trace metals (Fe, Ti and Zr) coeluted with Al, Si; whereas, Pb appeared to be present as colloidal fractions.     

Determination of arsenic in water samples by Total Reflection X-Ray Fluorescence using pre-concentration with alumina

The determination of arsenic in water samples requires techniques of high sensitivity. Total Reflection X-Ray Fluorescence (TXRF) allows the determination but a prior separation and pre-concentration procedure is necessary. Alumina is a suitable substrate for the selective separation of the analytes. A method for separation and pre-concentration in alumina, followed by direct analysis of the alumina is evaluated. Quantification was performed using the Al–Kα and Co–Kα lines as internal standard in samples prepared on an alumina matrix, and compared to a calibration with aqueous standards. Artificial water samples of As (III) and As (V) were analyzed after the treatment. Fifty milliliters of the sample at ppb concentration levels were mixed with 10 mg of alumina. The pH, time and temperature were controlled. The alumina was separated from the slurry by centrifugation, washed with de-ionized water and analyzed directly on the sample holder. A pre-concentration factor of 100 was found, with detection limit of 0.7 μgL⁻¹. The percentage of recovery was 98% for As (III) and 95% for As (V) demonstrating the suitability of the procedure.     

Interactions of L-alanine with alumina as studied by vibrational spectroscopy

The interactions of L-alanine with gamma- and alpha-alumina have been investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). L-alanine/alumina samples were dried from aqueous suspensions, at 36.5 degrees C, with two amino acid concentrations (0.4 and 0.8 mmol g-1) and at different pH values (1, 6, and 13). The vibrational spectra proved that the nature of L-alanine interactions with both aluminas is the same (hydrogen bonding), although the groups involved depend on the L-alanine form and on alumina surface groups, both controlled by the pH. For samples prepared at pH 1, cationic L-alanine [CH3CH(NH3+)COOH] displaces physisorbed water from alumina, and strong hydrogen bonds are established between the carbonyl groups of alanine, as electron donors, and the surface Al-OH2+ groups of alumina. This occurs at the expense of alanine dimer dissociation and breaking of intramolecular bonds. When samples are prepared at pH 6, the interacting groups are Al-OH2+ and the carboxylate groups of zwitterionic L-alanine [CH3CH(NH3+)COO-]. The affinity of L-alanine toward alumina decreases, as the strong NH3+...-OOC intermolecular hydrogen bonds prevail over the interactions with alumina. Thus, for a load of 0.8 mmol g-1, phase segregation is observed. On alpha-alumina, crystal deposition is even observed for a load of 0.4 mmol g-1. At pH 13, the carboxylate groups of anionic L-alanine [CH3CH(NH2)COO-] are not affected by alumina. Instead, hydrogen bond interactions occur between NH2 and the Al-OH surface groups of the substrate. Complementary N2 adsorption-desorption isotherms showed that adsorption of L-alanine occurs onto the alumina pore network for samples prepared at pH 1 and 13, whereas at pH 6 the amino acid/alumina interactions are not strong enough to promote adsorption. The mesoporous structure and the high specific surface area of gamma-alumina make it a more efficient substrate for adsorption of L-alanine. For each alumina, however, it is the nature of the specific interactions and not the porosity of the substrate that determines the adsorption process.     

顶空-气相色谱-质谱法检测易燃液体及其分类

建立了一种利用顶空-气相色谱-质谱进行易燃液体的检测和分类的有效方法。以凹版油墨为模型样品体系，利用顶空-气相色谱-质谱鉴定了样品中的易挥发组分。考察了平衡温度、平衡时间和组分含量等特性参数。利用外标法测定了组分含量，结果显示该方法的相对标准偏差为0.88%~2.88%，加标回收率为92.8%~103.1%。采用该方法对多种实际样品进行了定性和定量分析，并用混合溶剂闪点预测模型计算了样品的闪点，与闪点实测值进行了比较。结果表明，该方法可用于易燃液体实际样品闪点的预测，实现化学品的分类，闪点预测值与实测值最大偏差仅为3.2℃。该方法为易燃液体实际样品的分类提供了一种新颖、高效和便捷的技术。     

Synthesis and characterization of Fe doped mesoporous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> by sol–gel method and its use in trichloroethylene combustion

Two mesoporous alumina samples were synthesized using the sol–gel method, and these samples were tested as catalysts in trichloroethylene combustion reaction. One alumina sample was doped with Fe to study the influence of a small amount of this agent on the characteristics and properties of alumina as a catalyst. Both catalysts (pure alumina and alumina doped with Fe) were thoroughly characterized by different techniques, such as DTA/TGA, FT-IR, XRD, SEM and TEM, and the porous characterization was conducted using a N₂ physisorption technique. The doping agent presented a particular influence on the morphology and textural porosity in the alumina catalyst and therefore, it exhibited different catalytic behavior than the pure alumina catalyst. For both catalysts, the crystalline phase of γ-alumina was reported using XRD technique, and the crystallite size ranged from 7.8 to 12.8 nm. Using TEM images, the alumina catalyst doped with Fe revealed to contain a mixture of three types of iron oxide (maghemite, magnetite and hematite), mainly as roughly spherical nanoparticles. For both alumina catalysts, trichloroethylene catalytic combustion was conducted on a packed bed reactor in air at a temperature range of 50 to 600 °C. The alumina catalyst doped with Fe showed a higher catalytic activity than pure alumina, mainly due to the presence of micropores and grain morphology of flat faces.     

Morphology-controlled electrochemical sensing amaranth at nanomolar levels using alumina

Different-shaped aluminas were readily prepared via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6 h to 24 h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200 nm, as confirmed by scanning electron microscopy. Transmission electron microscopy observation revealed that longer reaction time was beneficial for the formation of porous and uniform fiber-like structures. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. On the surface of alumina microfibers, the oxidation peak currents of amaranth increased remarkably. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150 nM, and the detection limit was 0.75 nM after 1-min accumulation. The analytical application in drink samples was investigated, and the results consisted with the values that obtained by high-performance liquid chromatography.     

负载型氨基功能化离子液体吸附CO2性能差异研究

以Al₂O₃、SiO₂和活性炭为载体,采用浸渍法制备了负载型离子液体（[NH₂p-mim]X:X= Br-,PF₆-,BF₄-,NTf₂-）CO₂吸附剂,利用红外光谱（FT-IR）、元素分析(EA)、热重差热分析（TG-DTA）等技术对负载型离子     

Valence state of Mo and surface coverage of alumina by molybdenum-oxygen species in MoOx/Al2O3

CO₂ chemisorption, BET surface area and the degree of reduction of Mo(VI) (e/Mo) have been determined in MoO_x/Al₂O₃ samples, reduced with hydrogen at temperatures between 673 and 1173 K. The free alumina surface figures calculated from the surface area and e/Mo values were identical with those obtained from direct CO₂ chemisorption measurements. This identity indicates that all of the oxygen ions of the surface molybdenum-oxygen species block the alumina surface.     

Nanoporous surface wetting behavior: the line tension influence

The aim of this work is to develop a physical model to describe the evolution of the apparent contact angle for four different liquids on nanotextured alumina surfaces with different pore radius. The nanoporous alumina templates were fabricated by anodization of Al foil in a 0.3 M oxalic acid solution. Scanning electron microscopy was used to characterize the morphology of the surfaces. The templates are approximately 400 nm in thickness and consist of a well-ordered hexagonal array of uniform radius pores spaced 105 nm apart with pore radii from 12 to 42 nm. The wettability of nanoporous alumina templates was investigated using contact-angle measurements. We measured the contact angles using four liquids: water, ethylene glycol, aniline, and a mixture of ethylene glycol and aniline. We developed a new theoretical model for the contact angle on nanoporous surfaces as a function of the pore radius. This model is based on energy considerations and involves liquid penetration into the nanopores driven by the capillarity (Laplace's law). Because the air is compressed inside the pores, this model also includes the effect of the line tension. This is important because the three-phase line length is greatly enhanced in our nanoporous structures. For example: for a millimeter-sized droplet, the three-phase line around the perimeter of the droplet is a few millimeters long, whereas the total three-phase line within the pores can reach several tens of meters. Using our model, the line-tension value for our nanopore samples is positive and ranges from 4 to 13 × 10(-9) N, which falls within the wide interval from 10(-11) to 10(-5) N quoted in the literature. Nanoporous surfaces may allow the effect of line tension to be visible for micro- to macrodroplets.     

Analysis of polycyclic aromatic hydrocarbons in pine needles by gas chromatography-mass spectrometry: comparison of different extraction and clean-up procedures

Three extraction methodologies (Soxhlet, ultrasonic and pressurized liquid extraction) and several clean-up procedures (Florisil, silica and alumina in cartridges or glass column format) were tested and compared to extract 16 US Environmental Protection Agency (EPA) polycyclic aromatic hydrocarbons (PAHs) from Pinus pinea L. needles. Quantification was done by gas chromatography with mass spectrometry, by internal standard method using five deuterated PAH surrogate standards. Among the several extraction and clean-up procedures tested, ultrasonic extraction followed by alumina cartridge clean-up was the preferred method, yielding recoveries between 72 and 100% and limits of detection between 0.22 and 0.71 ng/g dry weight. The performance of the method was tested to determine PAHs in naturally contaminated samples.     

Surface properties and catalytic activity of pure and silica-coated aluminas

The surface properties of predominantly microporous, mesoporous, and nonporous alumina samples were studied and compared with samples modified by coating with a fixed amount of silica on their surfaces. The samples were characterized in terms of their specific surface areas, pore structure, and the chemistry of the surface, namely, surface acidity and surface OHs. An attempt was made to relate the activity toward cumene cracking with the chemistry as well as the predominant pore size. This study will hopefully reveal the role of the pore structure of alumina in determining its adsorption and catalytic activity and also the effect of doping with silica in modifying the surface properties of alumina.     

Ultrafiltration and alumina adsorption of micelles for the preconcentration of copper(II) in water.

Micellar-enhanced ultrafiltration was considered from the viewpoint of trace analysis, by taking copper(II) as an example. Copper(II) cations were collected electrostatically on micelles of sodium dodecyl sulfate, and separated from the mother liquor by ultrafiltration. However, the final solution contained a large amount of surfactant, which caused serious interference in the determination. This problem was overcome by using alumina adsorption, where negatively charged micelles were adsorbed on positively charged alumina particles and then recovered by conventional filtration. The copper was leached from the micelles with 4 mol l(-1) nitric acid, leaving the surfactant on the alumina. The proposed method was successfully applied to an analysis of certified reference water samples.     

Effect of a novel green modification of alumina nanoparticles on the curing kinetics and electrical insulation properties of epoxy composites

A novel green surface modification was successfully implemented on alumina nanoparticles using chitosan (CS) to prevent nanoparticles' aggregation. To evaluate the surface changes of nanoparticles, FTIR, TGA, TEM, and SEM analyses were used. The cure kinetics of the uncured samples was analyzed by DSC. Different methods such as KAS, Friedman, Starink, and FWO were applied to measure the activation energy. The activation energy of epoxy reinforced with chitosan-functionalized alumina (epoxy/[CS-EPO-alumina]) was less than that of epoxy reinforced with alumina (epoxy/alumina), which was a confirmation of the positive effect of CS on curing reaction kinetics. Using the Malek method, the Sestak-Berggren autocatalytic equation was chosen to investigate the cure kinetics of the epoxy. It was found that the Sestak-Berggren equation is well matched with the experimental data and the model was suitable to predict the epoxy curing reaction reliably. Moreover, the glass transition temperatures of all samples were approximately the same. The effect of surface modification of alumina on the electrical insulating behavior of epoxy was also studied. It was found that CS functionalized alumina (CS-EPO-alumina) increased volume resistivity of epoxy at a temperature range of 30 to 80°C more than that of alumina. Electric stability and breakdown strength of epoxy/alumina and epoxy/(CS-EPO-alumina) also enhanced, where epoxy/(CS-EPO-alumina) experienced a further increase compared to epoxy.     

Structural Characterization by SIMS of Alumina Coatings on Stainless Steel

Al₂O₃ coatings were obtained by the alkoxide route and deposited on stainless steel using the dip coating technique. The starting precursor was aluminum sec-butoxide modified by acrylic acid in order to prevent its precipitation in the presence of water.Useful information for the structural organization of alumina coatings on stainless steel is deduced from SIMS analysis. SIMS data reveal that the coating structure brings into play two different layers: an outer alumina layer that is more or less doped, mainly by iron, and an internal layer corresponding to the alumina/steel interphase. Beneath the interphase, the presence of an oxidized steel layer on the substrate surface is detected.Whatever the coating, the alumina/steel interphase exhibits a nearly constant thickness. On the other hand, a thickness variation of the oxidized steel layer is observed between samples under study: this thickness increases with the curing time of the coating.     

Hemimicelle-based solid-phase extraction of estrogens from environmental water samples

Hemimicelles and admicelles of sodium dodecyl sulfate (SDS) on alumina and cetyltrimethyl ammonium bromide (CTAB) on silica were evaluated for the concentration and purification of the priority estrogens estrone (E(1)), 17beta-estradiol (E(2)) and ethynylestradiol (EE(2)) from sewage and river samples. Retention was based on analyte-sorbent hydrophobic and cation-pi interactions. Parameters affecting the SPE of estrogens on both types of sorbents were comparatively investigated. Adsolubilization was quantitative for SDS hemimicelles/admicelles and CTAB admicelles. SDS hemimicelle-coated alumina was the sorbent selected on the basis of the lower elution volume required and the higher sample flow rate allowed. Combination of estrogen adsolubilization-based SPE with liquid chromatography-diode array/fluorescence detection permitted the quantification of the target compounds with detection limits ranging from 20 to 100 ng l(-1). The relative standard deviation ranged from 3 to 8%. The approach developed was applied to the determination of estrogens in raw and treated sewage and river samples. The recovery found for estrogens in these environmental matrices was between 85 and 105%.