The Photochemical Synthesis of Fine Chemicals with Sunlight

The light of the sun can be used directly for changing chemical structures photochemically. Any industrial application must conform to the limitations imposed by the spectral distribution of the photons from the sun, the interruptions to the radiation due to the day/night rhythm, and the weather. In this review, we describe the photochemical potential of the sun, give a fundamental treatment of the concept of photoreactors driven by sunlight (abbreviated to solar photoreactors), and give an account of the realization of this concept in the first pilot plant on the “Plataforma Solar de Almeria” in southern Spain and in other activities in this field. Based on experimental data from photochemical investigations on the pilot plant scale, possibilities, limitations, and the potential growth of solar photochemistry are described. Solar photochemistry, in our opinion, is a technique which could make a contribution to the chemistry of the future because of its photochemical synthesis potential, the avoidance of waste products, and the direct utilization of the sun, not only as a primary energy source, but also as a reaction partner.     

Precise measurement of hyperfine structure in the state of Rb

We demonstrate a technique to measure hyperfine structure using a frequency-stabilized diode laser and an acousto-optic modulator locked to the frequency difference between two hyperfine peaks. We use this technique to measure hyperfine intervals in the 5 P _3/2 state of ⁸⁵Rb and obtain a precision of 20 kHz. We extract values for the magnetic-dipole coupling constant A = 25.038(5) MHz and the electric-quadrupole coupling constant B = 26.011(22) MHz. These values are a significant improvement over previous results. Received 6 March 2003 Published online 15 April 2003     

Preparation of ultra fine nickel-copper bimetallic powder for BME-MLCC

The preparation of ultra fine nickel-copper bimetallic powder with two-stage chemical reduction method was investigated. Reductive sugar and hydrazine hydrate were employed as reducing agent in different reductive stage, respectively. Reaction of CuSO₄·5H₂O with reductive sugar at 70 °C gives cuprous oxide and copper particles, then as-prepared mixture and nickelous hydroxide were reduced by hydrazine hydrate, and nickel-copper powder having excellent dispersibility was prepared. Influences of nickel added on composition and dispersibility of powder were studied. TG/DTG/DTA of nickel-copper powder, which is stable in room temperature, were discussed with thermal analyzer. Relation of nickel content to oxidation temperature was investigated. Ni-Cu bimetallic powder particles have a fully coated structure when nickel content is up to 30%. As-prepared nickel-copper powder was applied in base metal electrode-multilayer ceramic capacitor (BME-MLCC). The end termination has high adhesion force, fairly good densification, low resistivity, excellent solderibility behavior and resistance behavior to soldering.     

Annealing effects on the magnetization of Co–Ni–B amorphous nanoparticles

Chemically prepared (Co_xNi_1−x)_1−yB_y (x=0.5, 0.75, 1; y≈0.4) amorphous fine particles were characterized by X-ray diffraction, DTA and TGA, and in situ magnetic measurement as a function of annealing temperature in an inert atmosphere. Magnetic measurement performed in as-prepared and 150°C annealed samples shows an increase of the saturation magnetization and magnetic moment after thermal treatment. Room temperature magnetization increases by factors of 3.5, 1.8, and 1.5, for x=0.5, 0.75, and 1, respectively. These measurements may indicate a local re-ordering of the amorphous phase at temperatures much lower than the full crystallization temperature.     

The utility of Bacillus subtilis as a bioflocculant for fine coal

The application of Bacillus subtilis as a flocculant for fine coal has been reported here. Zeta-potential measurements showed that both the coal and bacteria had similar surface charge as a function of pH. Surface free energy calculations showed that the coal was hydrophobic while the bacterium was hydrophilic. The adhesion of the bacteria to coal and subsequent settling was studied in detail. Adhesion of bacteria to coal surface and subsequent settling of coal was found to be quick. Both adhesion and settling were found to be independent of pH, which makes the process very attractive for field applications. The presence of an electrolyte along with the bacterium was found to not only enhance adhesion of bacteria, but also produce a clear supernatant. Further, the settled fraction was more compact than with bacteria alone. Interaction energy calculations using the extended DLVO theory showed that the electrical forces along with the acid–base interaction energy play a dominant role in the lower pH range. Above pH 7, the acid–base interaction energy is the predominant attractive force and is sufficient enough to overcome the repulsive forces due to electrical charges to bring about adhesion and thus settling of fine coal. With increase in electrolyte concentration, the change in total interaction energy with pH is minimal which probably leads to better adhesion and hence settling.     

Yet another way of calculating moments of the Kesten's distribution and its consequences for Catalan numbers and Catalan triangles

We calculate moments of the so-called Kesten distribution by means of the expansion of the denominator of the density of this distribution and then integrate all summands with respect to the semicircle distribution. By comparing this expression with the formulae for the moments of Kesten's distribution obtained by other means, we find identities involving polynomials whose power coefficients are closely related to Catalan numbers, Catalan triangles, binomial coefficients. Finally, as applications of these identities we obtain various interesting relations between the aforementioned numbers, also concerning Lucas, Fibonacci and Fine numbers.     

Topical Problems in Elemental Analysis of Advanced Ceramic Materials

Selected prominent problems in the analysis of advanced ceramic materials are surveyed. The importance of reliability of results is discussed in the field of elemental trace- and microanalysis in view of its interaction with economy, power of detection, local resolution and speciation selectivity. Particular problems in the analysis of major constituents, trace components and microlocal distributions are based on the striking propertics of ceramics; they are exemplified. Analytical assistance must start from the beginning of the production processing, in the preparation of the powdered base materials. Determination of the stoichiometry requires high accuracy and differentiation of chemical species in bulk and surface analysis of ceramic base powders. Element trace determination by direct instrumental methods requires standard reference materials for calibration; these are currently inavailable in a sufficient variety. For optimum reliability and power of detection, element traces must be prepared in isolated form in a small excitation volume for analysis. A review on the state-of-the-art of wet-chemical combined procedures is presented. Decomposition position procedures are emphasized, due to their risk of contributing severe systematic error. Combustion in elementary fluorine is presented for decomposition of refractory materials. The performance of some direct procedures is discussed. Very efficient methods are available for element trace determinations in ceramic materials, offering high detection power. Several approaches for high-resolution local microanalysis in non-conductive ceramic materials are identified as the most promising development in the analysis of sintered compact ceramic products and devices.     

SiO2/α-FeOOH和SiO2/γ-Fe2O3微粒的界面研究

α－FeOOH微粒由于其表面高活性，在转变成γ－Fe2O3的热处理过程中容易烧结，一旦这种烧结现象发生，得到的γ－Fe2O3磁粉磁性能大大下降[1]．为了克服这一困难，目前采用在α-FeOOH微粒表面包敷有机物[2]和无机物[3]来隔离颗粒，阻止其聚集．其中SiO2表面包敷处理是最令人感兴趣的研究课题之一[4，5]．SiO2是一种难烙性的非磁性材料，它包敷在α-FeOOH微粒表面外，不仅可提高α－FeOOH转变成γ－Fe2O3的热处理温度，有利于得到外形完好、晶格完整的γ－Fe2O3磁粉，而且由包效层与内核之间的界面相互作用引起的表面各向异性常…     

Spin-orbit and spin-spin couplings in He2 and He2−

The spin-orbit and the spin-spin coupling constants of the ⁴Π_g state of the He₂ ⁻ ion, of the parent a³Σ_u ⁺, and of the b³Π_g states of He₂ have been evaluated by a multireference configuration interaction method. The theoretical spin-spin splittings of the a³Σ_u ⁺ state and the R-dependent spin-spin function are found to be in excellent agreement with experiment, with deviations in the range of a few MHz. The theoretical spin-orbit constants and splittings of the b³Π_g state are larger than the experimental values by about 370 MHz. The spin-orbit coupling constant of the ⁴Π_g state of He₂ ⁻ is␣estimated to be three times smaller than in the b³Π_g state, but one of the intramultiplet off-diagonal spin-spin interactions is predicted to give a large contribution to the fine structure of the metastable ion. The theoretical fine structure constants for the He₂ ⁻ ion are expected to␣aid future spectroscopic investigations of the fine structure splittings of the negative ion. Received: 14 April 1998 / Accepted: 27 July 1998 / Published online: 19 October 1998     

Characterisation of electroplated Sn/Ag solder bumps

Environmental concerns as well as legal constraints have been pushing research on flip chip technology towards the development of lead-free solders and also to new deposition techniques [Z.S. Karim, R. Schetty, Lead-free bump interconnections for flip-chip applications, in: IEEE/CPMT 1nternational Electronics Manufacturing Technology Symposium, 2000, pp. 274-278, P. Wölflick, K. Feldmann, Lead-free low-cost flip chip process chain: layout, process, reliability, in: IEEE International Electronics Manufacturing Technology (IEMT) Symposium, 2002, pp. 27-34, M. McCormack, S. Jin, The design and properties of new, pb-free solder alloys, in: IEEE/CPMT International Electronics Manufacturing Technology Symposium, 1994, pp. 7-14, T. Laine-Ylijoki, H. Steen, A. Forsten, Development and validation of a lead-free alloy for solder paste applications. IEEE Transactions on Components, Packaging, and Manufacturing technology, 20(3) (1997) 194-198, D. Frear, J. Jang, J. Lin, C. Zhang, Pb-free solders for flip-chip interconnects, JOM, 53(6) (2001) 28-32].Binary and ternary tin alloys are promising candidates to substitute lead-content components. In this paper, we describe an electroplating technique for high density FlipChip packaging [M. Bigas, E. Cabruja, Electrodeposited Sn/Ag for flip chip connection, CDE (2003)]. An analysis using Auger Electron Spectroscopy (AES) together with additional Energy Dispersive Xray analysis (EDS) tests and Scanning Electron Microscope (SEM) analysis have been performed to optimize the reflow process of the electrodeposited bumps.