天体等离子体中铝发射谱线的研究

结合天体等离子体中铝发射谱和某些能级寿命的测量 。

二氧化硅吸附铝离子的X射线光电子能谱(XPS)表征

用X射线光电子能谱技术研究了不同pH条件下二氧化硅对铝离子的吸附作用。在pH分别为3.74、4.25和4.88条件下,吸附在二氧化硅表面的铝离子的Al2p电子结合能依次为74.30、74.90、75.10eV。根据Al3+在水溶液中的一级水解常数pK1=4.99,认为在pH=3.74条件下,吸附在二氧化硅表面的铝离子的形态为Al3+,而在其余两种pH条件下表面铝离子的形态为Al(OH)2+。

叠氮二乙基铝三聚体和单体的缔合-解离平衡的研究

尽管叠氮二乙基铝Et2AlN3(DEAA)是一个重要的化合物,但人们对它研究还是很少的。本文通过温度-蒸气压关系研究了纯态DEAA的三聚体和单量体之间的缔合-解离平衡;通过相对分子质量测定、核磁共振氢谱和核磁共振铝谱的测定,研究了在苯和甲苯溶液中DEAA的三聚体和单量体之间的缔合-解离平衡。借助温度-蒸气压曲线分别计算了DEAA三聚体和单量体的气化焓和解离焓;通过相对分子质量测定、核磁共振铝谱测定等方法计算得到了溶液中DEAA三聚体和单量体的解离平衡常数、解离焓和解离熵等热力学数据。

叠氮二乙基铝合成及其相关反应的研究

在芳烃溶剂中用氯化二乙基铝和叠氮化钠反应合成了叠氮化二乙基铝(DEAA),其产率高达87%,比文献值高出17%。在正己烷中没有合成出DEAA,在含30%四氢呋喃(THF)的正己烷中合成出DEAA·THF配合物。在芳烃溶剂中,随着苯环上甲基数目的增加,DEAA的收率增加。测定了氯化二乙基铝、氯化二乙基铝的正己烷溶液、氯化二乙基铝的甲苯溶液的27AlNMR谱。由27AlNMR谱数据确定了氯化二乙基铝在甲苯中解离平衡式,计算了氯化二乙基铝在甲苯中解离平衡的热力学数据。用DEAA与苯甲酸甲酯直接合成了苯甲酰叠氮,并表征了其结构。这是一个新反应,至今无文献报导。用实验证明了在正己烷溶液中,用氯化二乙基铝、叠氮化钠与苯甲酸甲酯合成苯甲酰叠氮,没有经过氯化二乙基铝和叠氮化钠反应生成中间体DEAA的这一步。依据实验事实建立了上述三种反应的反应机理。

叠氮二异丁基铝的构造及其缔合-解离平衡研究

叠氮二异丁基铝DBAA是一个新合成的化合物。通过相对分子质量的测定、氢核磁共振谱和铝核磁共振谱的测定确定了DBAA三聚体的分子构造在溶液中研究了DBAA的三聚体和单量体之间的缔合解离平衡。这个平衡受溶剂性质、温度的影响。借助铝核磁共振谱和相对分子质量的测定计算了DBAA三聚体的解离平衡常数、解离焓和解离熵等热力学数据。

Al原子特征辐射谱的实验研究

使用带Q开关的Nd ,YAG脉冲激光器发出的脉冲激光束烧蚀金属Al靶产生Al等离子体 .以Al等离子体为光源 ,利用时空分辨技术 ,采集Al等离子体发光信息 ,获得Al原子特征辐射谱 .基于Al原子特征辐射谱 ,简要分析了Al原子共振双线辐射规律 ,并与L -S耦合理论计算作了比较 ,结果发现实验结果与理论分析相符合 .

焙烧对HL沸石结构的影响

运用MASNMR研究了焙烧对HL沸石结构的影响 .结果表明 ,高温焙烧将引起HL沸石骨架的脱铝 ,当焙烧温度高于 65 0℃后 ,沸石骨架脱铝明显 ;2 7Al MASNMR谱表明 ,从沸石上脱下来的铝 ,部分形成了NMR不可测的无定形态 ,且随焙烧温度的升高 。

Synthesis of aluminum tri-polyphosphate anticorrosion pigment from bauxite tailings

Aluminum tri-polyphosphate was synthesized from bauxite tailings and phosphoric acid with a P/A1 molar ratio of 3. This is highly advantageous from a waste recycling perspective as bauxite railings are generally regarded as unusable waste. The acidity, whiteness and mean particle size of prepared aluminum tri-polyphosphate are all improved after modification. The possibility of using modified aluminum tri-polyphosphate as an anticorrosive pigment was also investigated by electrochemical impedance spectroscopy. The resistance of the coatings with modified aluminum tri-polyphosphate is 7×10^7Ω for 40 d of immersion, which is superior or at least comparable to that of coatings containing APW-2, which exhibits a resistance of 5.7×10^7Ω.

PIEZOSPECTROSCOPIC STUDY OF RESIDUAL STRESSES AROUND INDENTATIONS IN SiC/Al_O_3 NANOCOMPOSITE

A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. <

Time-resolved laser-induced breakdown spectroscopy of aluminum

We develop a system to measure the elemental composition of unprepared samples using laser-induced breakdown spec-troscopy (LIBS) in our laboratory,which can be used for the determination of elements in solids,liquids and aerosols. A description of the instrumentation,including laser,sample chamber and detection,is followed by a brief discussion. The time-resolved LIBS of aluminum at atmospheric pressure is presented. At the end,the possibilities and later uses of this technique are briefly discussed.

Influence of silicate anions structure on desilication in silicate-bearing sodium aluminate solution

The structural changes of silicate anions in the desilication process with the addition of calcium hydrate alumino-carbonate were studied by measuring Raman spectra, infrared spectra and corresponding second derivative spectra. The results show that the desilication ratio in the solution prepared by the addition of sodium silicate(solution-SS) is much greater than that in the solution by the addition of green liquor(solution-GL), and low alumina concentration in the sodium aluminate solutions facilitates the desilication process. It is also shown that alumino-silicate anions in the solution-GL, and Q^3 polymeric silicate anions in solution-SS are predominant, respectively. In addition, increasing the concentration of silica favors respectively the formation of the alumino-silicate or the Q^3 silicate anions in the solution-GL or the solution-SS. Therefore, it can be inferred that the low desilication ratio in the silicate-bearing aluminate solution is mainly attributed to the existence of alumino-silicate anions.

Organic acids and inorganic anions in Bayer liquors by ion chromatography after solid-phase extraction

A method for the simultaneous separation and determination of organic acids and inorganic anions in Bayer liquors was developed by gradient ion chromatography with suppressed conductivity detection. Formate, acetate, propionate, oxalate, succinate, glutarate, fluoride, chloride and sulfate were separated and determined in 33 min. The samples were pretreated with solid-phase extraction, which has high selectivity for removing a large number of metallic ions in the Bayer liquors, and filtered with a 0.45 μm filter membrane before being injected into the ion chromatographic system. The separation of six organic acids and three inorganic anions was achieved on an IonPac AS11-HC column with KOH as the eluent, and the detection was performed by a conductivity detection mode. No interference is found in the presence of fluorate, chlorate and sulphate when organic acids are determined. The calibration graphs of peak area for all the analytes are linear over a wide range. The relative standard derivation of the peak area of analytes is less than 2.14%. Under optimum conditions the detection ranges from 0.2 to 100.0 mg/L. The average recoveries of the added standards are between 94.3% and 102.8%.

Laser-induced breakdown spectroscopy characterization of Al in different matrix

Some experimental investigations were carried out with the samples of metal Al and AlCl3 solutions. It is found that the spectrum varies with the change of experimental setup parameters both in Al bulk material and AlCl3 solutions. The temporal evolution properties and the affection of incident laser energy on the laser-induced breakdown spectroscopy (LIBS) signals were also discussed. The lifetime of laser induced plasma in AlCl3 solutions is found to be about 30 ns which is much shorter than in solid materials. Compared with the solid samples, the Al LIBS signals in AlCl3 solutions require higher laser energy. Under the optimized conditions, the detection limit of Al in AlCl3 solution was determined to be around 1000 ppm for the system we used.

Effect of micro arc oxidation treatment on localized corrosion behaviour of AA7075 aluminum alloy in 3.5% NaCl solution

Alumina coating was formed on AA7075 aluminum alloy by micro arc oxidation（MAO） method and its corrosion and stress corrosion cracking（SCC） behaviors were examined in 3.5%（mass fraction） NaCl solution.Electrochemical impedance spectroscopy（EIS） was used to evaluate the degradation of the coating as a function of immersion time and was modeled with appropriate equivalent circuits.Constant load stress corrosion cracking（SCC） results followed by post-test metallographic observations demonstrated the usefulness of MAO coating to avoid the premature failure of the alloy due to severe localized corrosion initiated by Cu-and Fe-rich intermetallic phases.

Effect of modified starches on depression of diaspore

Four modified starches with selected charge characteristics including cationic starch(CAS),carboxymethyl starch(CMS),amphoteric starch(AMS) and soluble starch(SS) were investigated as depressants for diaspore in reverse flotation test using cationic collector(dodecylamine).Adsorption examination,Zeta potential measurement and Fourier transform infrared(FTIR) spectroscopy were used to clarify the role of the surface charge characteristics of starches in determining the adsorption behavior and depression performance as well as the mineral-starch interaction.Results show that the positively charged starches(CAS and AMS) display higher adsorption amounts and also better depression performance compared with the non-ionic(SS) and anionic starch(CMS),benefiting from the favorable electrostatic attraction with diaspore and also electrostatic repulsion with collector.FTIR spectroscopy proves the presence of hydrogen bonds and chemical complexation between mineral and starches in an integrated manner.

Effect of oxalate on seed precipitation of gibbsite from sodium aluminate solution

The precipitation performance and kinetics of gibbsite from sodium aluminate solution with different sodium oxalate concentrations as well as the corresponding influence mechanism of oxalate during the seed precipitation process were systematically investigated by physicochemical properties test,using SEM and Raman spectra.As the concentration of sodium oxalate increases,both the precipitation rate and particle size of gibbsite decrease.The presence of sodium oxalate not only increases the viscosity of sodium aluminate solution,but also promotes the transformation of Al(OH)4^? to Al2O(OH)6^2?.The overall reaction rate constant decreases and the apparent activation energy of gibbsite increases with the increasing sodium oxalate concentration,the rate controlling step of which is chemical reaction.The needle-like sodium oxalate precipitates on the gibbsite crystals and covers the active Al(OH)3 seed sites,which leads to the lower precipitation rate and the finer particle size of gibbsite during the seed precipitation process.

Surface nanostructure modification of Al substrates by N^+ ion implantation and their corrosion inhibition

The influence of implantation of N+ions of different energies on the nanostructure of7049Al substrates and the corrosioninhibition of produced Al samples in a3.5%NaCl solution was studied.The X-ray diffraction(XRD)results confirmed the formationof AlN as a result of N+ion implantation.The atomic force microscope(AFM)results showed that grains of larger scale are formedby increasing N+energy which can be due to heat accumulation in the sample during implantation causing higher rate of diffusion inthe sample,hence decreasing the number of defects.Corrosion resistance of the samples was studied by the electrochemicalimpedance spectroscopy(EIS)measurements.Results showed that corrosion resistance of implanted Al increases with increasing N+ion energy.The equivalent circuits for the N+implanted Al samples with different energies were obtained,using the EIS data whichshowed strong dependence of the equivalent circuit elements on the surface morphology of the samples.Finally,the relationshipbetween corrosion inhibition and equivalent circuit elements was investigated.

Raman Spectra of AlP/GaP Short-period Superlattice ①②

The samples of (AlP) n /(GaP) n short-period superlattice (period number n =4,6) grown by MOVPE and the sample of n-GaP (100) single crystal substrate are measured and analyzed by Raman spectrum.In the three kinds of samples,the double-phonon modes of first-order Raman scattering peaks are all existent.Moreover,the second-order Raman scattering peaks are observed to exist.

ZnO Nanobelts and Hollow Microspheres Grown on Cu Foil

ZnO nanobelts, hollow microspheres, and urchins have been prepared on copper foil via a simply low temperature evaporation route. The microstructure, morphologies, and photolu-minescence of the ZnO nanostructures were studied with X-ray diffraction, Raman spectra, scanning electron microscopy and photoluminescence spectra. The width of the nanobelts was about 500 nm and the length was longer than 10μm. The diameter of the hollow microspheres was between 5 and 10μm. A possible growth mechanism of the nanobelts, microspheres and urchins was proposed. The photoluminescence spectrum exhibited strong deep level energy emissions and a weak near band edge emission. These ZnO nanostructures on a copper substrate have the advantages of naturally good adhesion and electrical connection between the ZnO nanostructures and the conductive substrate.

Visible light-enhanced photothermal CO2 hydrogenation over Pt/Al2O3 catalyst

Light illumination has been widely used to promote activity and selectivity of traditional thermal catalysts. Nevertheless, the role of light irradiation during catalytic reactions is not well understood. In this work, Pt/Al2 O3 prepared by wet impregnation was used for photothermal CO2 hydrogenation, and it showed a photothermal effect. Hence, operando diffuse reflectance infrared Fourier-transform spectroscopy and density functional theory calculations were conducted on Pt/Al2 O3 to gain insights into the reaction mechanism. The results indicated that CO desorption from Pt sites including step sites(Ptstep) or/and terrace site(Ptterrace) is an important step during CO2 hydrogenation to free the active Pt sites. Notably, visible light illumination and temperature affected the CO desorption in different ways. The calculated adsorption energy of CO on Ptstep and Ptterrace sites was-1.24 and-1.43 e V, respectively. Hence, CO is more strongly bound to the Ptstep sites. During heating in the dark, CO preferentially desorbs from the Ptterrace site. However, the additional light irradiation facilitates transfer of CO from the Ptstep to Ptterrace sites and its subsequent desorption from the Ptterrace sites, thus promoting the CO2 hydrogenation.