Irradiation‐induced surface graft polymerization onto calcium carbonate nanoparticles and its toughening effects on polypropylene composites

Nano‐sized calcium carbonate was pretreated with silane coupling agent and then mixed with butyl acrylate that is of larger amount than the nanoparticles. Under γ‐irradiation, graft polymerization occurred on the nanoparticle surface, forming a nanocomposite structure consisting of grafted poly(butyl acrylate) (PBA), homopolymerized PBA, and the segregated nanoparticles. It was found that the silane pretreatment significantly promoted the graft reaction. When the grafted nano‐CaCO₃ particles were melt compounded with polypropylene (PP), an obvious synergistic effect, offered by (i) the chemical bonding between the elastomer type grafted PBA and nano‐CaCO₃ and (ii) the deliberately introduced thick interlayer mainly constructed by the homopolymerized PBA, led to a significant increase in notch impact strengths and elongation to break of PP at a rather low content of nano‐CaCO₃. Meanwhile, the tensile stiffness of the composites was also slightly increased and the yielding strength of the composites was almost unchanged. The results are different from those with conventional rubber‐toughened plastics, in which the improvement of ductility is acquired at high additive fraction and a great expense of strength performance. POLYM. ENG. SCI., 45:529–538, 2005. © 2005 Society of Plastics Engineers     

Large-scale production and quality assurance of hydrogen storage (battery) alloys

The new generation of high-capacity metal hydride rechargeable batteries is a cadmium-free energy alternative to current types of accumulators. While the first steps were made for consumer wireless applications, the newest developments aim toward traction systems (zero-emission cars). This article introduces the materials selection, quality control, and production principles of alloy systems suitable for storing hydrogen either electrochemically or by gas absorption. Examples of Zr-Ni, Ti-Mn₂, and rare earth-Ni₅ are demonstrated from the metallurgical standpoint. These alloys (currently produced in large scale— tons/day) are now used in industry after approximately 20 years of development.     

汽车变速器传动系统综合分析

介绍汽车变速器传动技术发展历程,分析MT,AT,CVT,AMT,DCT变速器各自优势与弱点以及未来发展趋势。     

Comparison of intensity distributions in tomograms from BF TEM, ADF STEM, HAADF STEM, and calculated tilt series

The three-dimensional (3D) morphology of a nanometer-sized object can be obtained using electron tomography. Variations in composition or density of the object cause variations in the reconstructed intensity. When imaging homogeneous objects, variations in reconstructed intensity are caused by the imaging technique, imaging conditions, and reconstruction. In this paper, we describe data acquisition, image processing, and 3D reconstruction to obtain and compare tomograms of magnetite crystals from bright field (BF) transmission electron microscopy (TEM), annular dark-field (ADF) scanning transmission electron microscopy (STEM), and high-angle annular dark field (HAADF) STEM tilt series. We use histograms, which plot the number of volume elements (voxels) at a given intensity vs. the intensity, to measure and quantitatively compare intensity distributions among different tomograms. In combination with numerical simulations, we determine the influence of maximum tilt angle, tilt increment, contrast changes with tilt (diffraction contrast), and the signal-to-noise ratio (SNR) as well as the choice of the reconstruction approach (weighted backprojection (WB) and sequential iterative reconstruction technique (SIRT)) on the histogram. We conclude that because ADF and HAADF STEM techniques are less affected by diffraction, and because they have a higher SNR than BF TEM, they are better suited for tomography of nanometer-sized crystals.     

Numerical and experimental analysis of the single droplet evaporation in a ultrasonic spray pyrolysis device

The present study deals with the numerical analysis of the water droplet evaporation in the carrier gas inside an ultrasonic spray pyrolysis (USP) device. Droplet evaporation is studied through numerical computational fluid dynamics simulation using Ansys Fluent version 16.1 software. The governing equations for mass, momentum, and energy contain source terms for the effects of droplet evaporation. The results are provided as time dependent evaporation rate, temperature and diameter of droplet. Additional experimental evaporation of HAuCl₄ solution droplets with temperatures of 80, 100 and 120°C was performed on a USP device. The obtained dried particles of gold chloride were characterized with TEM and analysed for their size and shapes to determine the effect of evaporation rate on the dried particle morphology. This provides insight into selecting optimal parameters for gold nanoparticle synthesis with HAuCl₄ in USP, for targeted sizes and shapes of the nanoparticles.     

Simulations of piezoelectric Lamb wave delay lines using a finite element method

The method of piezoelectric finite elements was applied to the simulation of piezoelectric Lamb-wave delay lines with and without acoustical absorbers. In this finite-element analysis, free as well as electrically driven vibrations were computed. The shapes of the symmetric Lamb modes were determined by the solution of eigenproblems, and the transient mechanical build-up process was studied for a switched electrical sine wave excitation. The transfer function, the group delay time, and the impedance matrix of devices of different designs are calculated. The good agreement between simulation and experimental results indicates the suitability of the finite-element method for optimizing acoustic delay-line devices.     

The flavour of cape gooseberry (Physalis peruviana L.)

Summary The volatile constituents of cape gooseberry (Physalis peruviana L.) were characterized using liquid/liquid extraction and fractionation of the flavour concentrates on silica gel, followed by high resolution gas chromatography and coupled gas chromatography — mass spectrometry. Sniffing gas chromatography of serially diluted flavour extracts showed methyl 2-methylbutyrate, 2,5-dimethyl-4-hydroxy-(2H)-furanone and its 4-methoxy derivative, 4- and 5-octanolide, -ionone, and -damascenone to be impact components. The non-volatile flavour fraction contained glucose, fructose, sucrose, citric acid, and smaller amounts of organic aliphatic and benzoic acids. The bound forms of volatiles were dominated by benzyl alcohol, 2-methylpropanol, and 2-methyl-butanol. The presence of significant amounts of activated acyl moieties in the fruit was indirectly concluded from various data.

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Das Aroma der Kapstachelbeere (Physalis peruviana L.)

Zusammenfassung Die flüchtigen Inhaltsstoffe der Kapstachelbeere (Physalis peruviana L.) sind nach Flüssig/Flüssig-Extraktion und Kieselgelfraktionierung der Aromakonzentrate mittels hochauflösender Gaschromatographie und Kopplung Gaschromatographie-Massenspektrometrie charakterisiert worden. Durch gaschromatographische Sniffing-Analyse von sukzessive verdünnten Aromaextrakten sind 2-Methylbuttersäuremethylester, 2,5-Dimethyl-4-hydroxy-3(2H)-furanon und dessen Methoxyderivat, 4- und 5-Octanolid sowie -Jonon and -Damascenon als sensorische Schlüsselsubstanzen erkannt worden. Die nichtflüchtige Aromafraktion enthält Glucose, Fructose, Saccharose, Citronensäure und kleinere Mengen an organischen, aliphatischen und benzoiden Säuren. Bei den gebunden vorliegenden flüchtigen Komponenten dominieren Benzylalkohol, 2-Methylpropanol und 2-Methylbutanol. Die Frucht enthält, wie verschiedene Befunde indirekt belegen, größere Mengen an aktivierten Acylresten.

     

Sliding wear performance of different polyimide formulations

Sliding wear studies on different polyimide (PI) formulations against hardened, smooth steel were conducted using a pin-on-ring testing facility. Contact pressure p was varied in such a way that for three different sliding velocities v (0.6, 1.5 and 3.0 m s⁻¹) two pv levels could be maintained (1.7 and 5.0 MPa m s⁻¹). The best results were achieved with a PI formulation containing 15 wt% graphite filler and 10 wt% fluorocarbon resin having a wear factor

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. This material was also superior to newly developed high performance thermoplastics, in particular polyetheretherketone (PEEK) and thermotropic liquid crystal polymers (LCP), even when the latter contained about 20 vol.% of short glass or carbon fibre reinforcement.