Nanostructured electrode materials for Ni-MH x batteries prepared by mechanical alloying

Nanocrystalline TiFe- and Mg₂Ni-type alloys were prepared by mechanical alloying followed by annealing. The structure and electrochemical properties of these materials were studied. The properties of hydrogen host materials can be modified substantially by alloying to obtain the desired storage characteristics. It was found that the respective replacement of Fe in TiFe by Ni and Mn improved not only the discharge capacity but also the cycle life of these electrodes. On the other hand, a partial substitution of Mg by Mn in Mg_2?x M _x Ni alloy leads to an increase in discharge capacity, at room temperature. Furthermore, the effect of the nickel and graphite coating on the structure of the nanocrystalline alloys and the electrodes characteristics were investigated. In Mg₂Ni-type alloy mechanical coating with graphite effectively reduced the degradation rate of the studied electrode materials.     

Microstructural Development of Ti-B Alloyed Layer for Hard Tissue Applications

Microstructural development was analyzed due to the effect of different sizes of precursor powders during surface plasma alloying modification on titanium surface.Ti-B nano and micropowders with 10 wt%B were deposited onto microcrystalline titanium substrate by plasma alloying.As a result,modified surface layer composed of Ti matrix and TiB borides was obtained.The type of the powder precursor influenced recasting process,possible occurrence of porosity and finally the obtained properties and microstructure of the surface layer.Different morphologies and sizes of TiB phase from micro,submicro to even nano increased the hardness and wear resistance of the obtained surface layers.Discussed results referred to a strong TiB precipitation dispersion provided by a fine elements homogenization during mechanical alloying process. Additionally,results of in vitro test with normal human osteoblast cells revealed proper cellular adhesion to modified surfaces.Scanning electron microscopy observation revealed the influence of gas pore size on culturing osteoblast colony.The proposed surface alloying was an effective method of producing TiB phase dispersed inα-Ti matrix with high hardness,good corrosion resistance and good cytocompatibility.Results confirmed that different types of the precursor powders influenced the properties of the surface layer.TiB phase dispersed inα-Ti matrix layer can offer new structural and biofunctional properties for innovative products in hard tissue applications.     

Synthesis and characterization of titanium-45S5 Bioglass nanocomposites

Titanium-45S5 Bioglass nanocomposites were synthesized by the combination of mechanical alloying and powder metallurgy process. The structure, mechanical and corrosion properties of these materials were investigated. Microhardness test showed that the obtained material exhibits Vicker’s microhardness as high as 770 HV_0.2 for Ti-20 wt.% 45S5 Bioglass, which is more than three times higher than that of a conventional microcrystalline titanium (225 HV_0.2). Additionally, titanium-10 wt.% of 45S5 Bioglass nanocomposites (i_c = 1.20 × 10⁻⁷ A/cm², E_c = −0.42 V vs. SCE) were more corrosion resistant than microcrystalline titanium (i_c = 2.27 × 10⁻⁶ A/cm², E_c = −0.36 V vs. SCE). In vitro biocompatibility of these materials was evaluated and compared with a conventional microcrystalline titanium, where normal human osteoblast (NHOst) cells from Cambrex (CC-2538) were cultured on the disks of the materials and cell growth was examined. The morphology of the cell cultures obtained on Ti-10 wt.% 45S5 Bioglass nanocomposite was similar to those obtained on the microcrystalline titanium. Mechanical alloying and powder metallurgy process for the fabrication of titanium-45S5 Bioglass nanocomposites with a unique microstructure, higher hardness, lower Young’s modulus and better corrosion resistance, in comparison to microcrystalline titanium, were developed. On the other hand, Ti-10 wt.% 45S5 Bioglass composites posses higher fracture toughness compared to 45S5 Bioglass. The proper modification of chemical composition and microstructure of Ti-bioceramic nanocomposites can expand the use of titanium in the biomedical fields.     

Biologisches Verfahren zum unspezifischen Nachweis g?rungshemmender Substanzen in Wein

Zusammenfassung Zum Nachweis von gärungshemmenden Steffen im Wein wurde eine neue biologische Methode entwickelt, die auf dem Prinzip er Keimzahlbestimmung durch stufenweise Verdünnung beruht. Für den Test wird die zu untersuchende Probe steril in eine Reihe von Reagensgläserm gefüllt und mit dem gleichen Volumen eines Nährmediums versetzt, das außer den Nährstoffen zusätzlich Brenztraubensäure zum Binden von schwefliger Säure enthält Diesem Testgemisch wird eine sehr verdünnte Suspension einer alkoholresistenten Hefe zugesetzt. Die Verdünnung wird so gewählt, daß in der höchsten Verdünnungsstufe nur noch einzelne Zellen je Einsaatvolumen vorhanden sind. Nach der Einsaat wird das Testgemisch 4–6 Tage bei 27° C gehalten. In allen Röhrchen, denen Hefezellen zugesetzt werden, wird eine deutliche Trübung und Gasbildung sichtbar werden. Enthält die Probe jedoch Hemmstoffe, so verringert sich die Anzahl der Röhrchen, in denen e in Hefewachstum erkennbar ist. Mit dieser Keimzahlmethode werden Hemmstoffe unspezifisch nachgewiesen; für folgende Substanzen wurde die Nachweisgrenze in Wein bestimmt: Kaliumsorbat 60 mg/l, Natriumazid 1 mg/l, Natriumfluorid 10 mg/l, p-Chlorbenzoesäure 3 mg/l, Actidion < 0,05 mg/l, Monobromessigsäure 2 mg/l. Da die Methode nicht spezifisch ist, können such Fungicide nachgewiesen werden, wenn sie in ausreichender Konzentration vorliegen. — Infolge der Verdünnung wird die Keimzahlmethode durch den Alkoholgehalt des Weines niche beeinträchtigt. Bei der Untersuchung einer Reihe von Weinen wurden natürlich vorkommende Hemmstoffe nicht gefunden.

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Biological method for unspecific detection of preservatives in wine

Summary Employing the method of the determination of the most probable number of single cell organisms by step-wise serial dilution, a new method for the detection of preservatives in wine has been developed. The sample to be investigated is distributed into a series of test tubes, to which the equal volume of a nutrient solution is added. This reduces the alcohol content of the sample sufficiently. The added solution contains sugar, yeast extract and pyruvie acid, which is needed to bind free SO₂ which might be present in the wine sample. To this mixture very dilute suspensions of cells of a yeast strain resistant to alcohol are added. The dilution of this suspension is such that the highest dilution used for inoculation contains no or only a single yeast cell. The same volume of this inoculum (1 ml) is used for each test tube with the mixture of wine sample and nutrient solution. After inoculation the tubes are kept for 4–6 days at 27° C. All tubes that have received an inoculum containing at least one viable yeast cell will show growth by becoming turbid. The most probable number of cells is calculated from these results. If however, the wine sample contains preservatives, the number of tubes showing yeast growth and thus the most probable number of cells will be reduced. This reduction in the most probable number can be used for the unspecific detection of preservatives. The detection limits of the following compounds were found to be potassium sorbate 60 mg/l, sodium azide 1 mg/l, sodium fluoride. 10 mg/l, p-chlorobenzoic acid 3 mg/l, actidione < 0.05 mg/l, monobromoacetic acid 2 mg/l. The proposed method is somewhat more sensitive than the usual fermentation test. Fungicides and detergents can also be detected, when they are present in inhibiting amounts. The disadvantage of the method is the need to sterilize the sample, but this can be done by simple means. In an investigation of white and red wines no natural inhibitors were found which interfer with the method for the unspecific detection of preservatives.

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Diese Arbeit wurde durch Gewährung einer Sachbeihilfe des Forschungsringes des Deutschen Weinbaues unterstützt.     

Epoxy resin modified with soybean oil containing cyclic carbonate groups

Carbonated soybean oil (CSO) containing five‐membered cyclic carbonate groups has been obtained in the reaction of epoxidized soybean oil with carbon dioxide in the presence of KI activated by 18‐crown‐6 under 6 MPa CO₂ pressure at 130°C. The CSO was used for modification of bisphenol‐A based epoxy resin. The composition epoxide‐cyclic carbonate was cured using polyamine hardeners by one‐step and two‐step procedures. All cured compositions were characterized for their thermal and mechanical properties and compared with the parent epoxy network. The optimal properties were obtained for compositions containing CSO and cured by one‐step method when phase separation takes place. The mechanical properties were discussed in terms of morphology observed by SEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2904‐2914, 2006     

Application of new oligomeric plasticizers based on waste poly(ethylene terephthalate) for poly(vinyl chloride) compositions

In this study, chemical recycling products of waste poly(ethylene terephthalate) with oligoesters were used as new plasticizers for poly(vinyl chloride) (PVC). The preparation conditions of the dry blend mixtures of the suspension PVC containing synthesised plasticizers were similar to the conditions of the preparing mixtures with commercial plasticizers. The plasticization efficiency of PVC plasticizers was then examined by analysis of the mechanical, physical and chemical properties, as well as the thermal resistance and migration of plasticizer molecules from polymer matrix. Test results proved that compositions with synthesised oligomeric plasticizers possessed similar or better properties than those containing commercial oligomeric plasticizers and much better properties than those having monomeric plasticizers. Thermal stabilities of the proposed plasticizers were higher than those of the commercial plasticizers either monomeric (bis(2-ethylhexyl)phthalate) or oligomeric, despite the fact that the synthesised oligoesters did not contain any antioxidant. The best properties, especially low volatility, very good mechanical properties, low migration were resulted of the transesterification of the waste PET with oligoesters based on adipic acid, triethylene glycol and 2-ethylhexanol which were selected as plasticizers synthesised on the technical scale. The tested plasticized PVC compositions possessed very good tear resistance, tensile strength, decrease of weight loss after 168 h at 80 °C and low migration. Processing properties of PVC compositions containing these synthesised plasticizers confirmed their effectiveness in these compositions for extrusion process.     

Structural characterization and electrochemical hydrogen storage properties of Ti2−xZrxNi (x = 0, 0.1, 0.2) alloys prepared by mechanical alloying

Nominal Ti₂Ni was synthesized under argon atmosphere at room temperature using a planetary high-energy ball mill. The effect of milling time and Zr substitution for Ti on the microstructure was characterized by XRD, SEM and TEM, and the discharge capacities of Ti_2−xZr_xNi (x = 0, 0.1, 0.2) were examined by electrochemical measurements at galvanostatic conditions. XRD analysis shows that amorphous phase of Ti₂Ni can be elaborated by 60 h of milling, whereas Zr substitution hinders amorphization process of the system. The products of ball milling nominal Ti_2−xZr_xNi (x = 0.1, 0.2) were austenitic (Ti, Zr)Ni and partly TiO, despite the fact that the operation was carried out under argon atmosphere. By comparing the SEM micrographs, it is found that the amorphous phase of Ti₂Ni was formed in the stage of cold-welding during milling, while with Zr substitution particles were flaky and finer, inhomogeneous in size distribution with massive agglomeration. TEM analysis was carried out and confirmed the observations via XRD. In the electrochemical tests, amorphous Ti₂Ni shows the best discharge capacity at 102 mAh/g at a current density of 40 mA/g. Without need of activation, it exhibits extraordinary cycling stability under room temperature. On the other hand, the effect of Zr substitution on the electrochemical property of Ti₂Ni is tricky, as superficially the discharge capacity drops drastically with Zr substitution, but with increase of Zr content (from x = 0.1 to x = 0.2), the discharge capacity increases generally, which credits to larger unit-cell-volume provided by ZrNi compared to TiNi. It is also found that the Ti–Ni system becomes significantly susceptible to oxidation when Zr is introduced to the initial powders as mechanical alloying is deployed as a synthesis method.     

Nanocrystalline LaNi4−xMn0.75Al0.25Cox electrode materials prepared by mechanical alloying (0≤x≤1.0)

Polycrystalline hydrogen storage alloys based on lanthanum (La) are commercially used as negative electrode materials for the nickel–metal hydride (Ni–MH_x) batteries. In this paper, mechanical alloying (MA) was used to synthesize nanocrystalline LaNi_4−xMn_0.75Al_0.25Co_x (x=0, 0.25, 0.5, 0.75 and 1.0) hydrogen storage materials. XRD analysis showed that, after 30 h milling, the starting mixture of the elements decomposed into an amorphous phase. Following the annealing in high purity argon at 700 °C for 0.5 h, XRD confirmed the formation of the CaCu₅-type structures with a crystallite sizes of about 25 nm. The nanocrystalline materials were used as negative electrodes for a Ni–MH_x battery. Cobalt substituting nickel in LaNi₄Mn_0.75Al_0.25 greatly improved the discharge capacity and cycle life of the LaNi₅ material. For example, in the nanocrystalline LaNi_3.75Mn_0.75Al_0.25Co_0.25 powder, discharge capacities up to 258 mA h g⁻¹ (at 40 mA g⁻¹ discharge current) were measured. Mechanical alloying is a suitable procedure to obtain LaNi₅-type alloy powders for electrochemical energy storage.