Spectroscopic, calorimetric, and catalytic evidences of hydrophobicity on Ti-MCM-41 silylated materials for olefin epoxidations

Hydrophobic Ti-MCM-41 samples prepared by post-synthesis silylation treatment demonstrate to be highly active and selective catalysts in olefins epoxidation by using organic hydroperoxides as oxidizing agents in liquid phase reaction systems. Epoxide yields show important enhancements with increased silylation degrees of the Ti-mesoporous samples. Catalytic studies are combined and correlated with spectroscopic techniques (e.g. XRD, XANES, UV-Visible, 29Si MAS-NMR) and calorimetric measurements to better understand the changes in the surface chemistry of Ti-MCM-41 samples due to the post-synthesis silylation treatment and to ascertain the role of these trimethylsilyl groups incorporated in olefin epoxidation. In such manner, the effect of the organic moieties on solids, and both water and glycol molecules contents on the catalytic activity and selectivity are analyzed in detail. Results show that the hydrophobicity level of the samples is responsible for the decrease in water adsorption and, consequently, the negligible formation of the non-desired glycol during the catalytic process. Thus, catalyst deactivation by glycol poisoning of Ti active sites is greatly diminished, this increasing catalyst stability and leading to practically quantitative production of the corresponding epoxide. The extended use of these hydrophobic Ti-MCM-41 catalysts together with organic hydroperoxides for the highly efficient and selective epoxidation of natural terpenes is also exemplified.

Life Cycle Assessment as a tool to promote sustainable Thermowood boards: a Portuguese case study

The present work aims to develop the Life Cycle Assessment study of thermo-modified Atlanticwood® pine boards based on real data provided by Santos & Santos Madeiras company. Atlanticwood® pine boards are used mainly for exterior decking and cladding facades of buildings. The LCA study is elaborated based on ISO 14040/44 standard and Product Category Rules for preparing an environmental product declaration for Construction Products and Construction Services. The inventory analysis and, subsequently, the impact analysis have been performed using the LCA software SimaPro8.0.4. The method chosen for impact assessment was EPD (2013) V1.01. The results show that more than ¾ of ‘Acidification’, ‘Eutrophication’, ‘Global warming’ and ‘Abiotic depletion’ caused by 1 m3 of Atlanticwood® pine boards production is due to energy consumption (electricity + gas + biomass). This was to be expected since the treatment is based on heat production and no chemicals are added during the heat treatment process.

Elicitors of induced disease resistance in postharvest horticultural crops: a brief review

Increasing loss of conventional fungicides due to pathogen resistance and general unacceptability in terms of public and environmental risk have favoured the introduction of integrated pest management (IPM) programmes. Induction of natural disease resistance (NDR) in harvested horticultural crops using physical, biological and/or chemical elicitors has received increasing attention over recent years, it being considered a preferred strategy for disease management. This article reviews the enhancement of constitutive and inducible antifungal compounds and suppression of postharvest diseases through using elicitors. The effect of timing of pre- and/or postharvest elicitor treatment and environment on the degree of elicitation and the potential for inducing local acquired resistance, systemic acquired resistance and/or induced systemic resistance to reduce postharvest disease is discussed. The review highlights that more applied and basic research is required to understand the role that induced NDR can play in achieving practical suppression of postharvest diseases as part of an IPM approach. (C) 2003 Elsevier B.V. All rights reserved.

Corrosion resistance of aged die cast magnesium alloy AZ91D

The corrosion behaviour of die cast magnesium alloy AZ91D aged at 160degreesC was investigated. The corrosion rate of the alloy decreases with ageing time in the initial stages and then increases again at ageing times greater than 45 h. The dependence of the corrosion rate on ageing time can be related to the changes in microstructure and local composition during ageing. Precipitation of the beta phase (Mg17Al12) occurs exclusively along the grain boundaries during ageing. The beta phase acts as a barrier, resulting in a decreasing corrosion rate in the initial stages of ageing. In the later stages, the decreasing aluminium content of alpha grains makes the alpha matrix more active, causing an increase in the corrosion rate. Electrochemical testing results also confirm the combined effects of the changes in alpha and beta phases on the corrosion resistance of the aged die cast AZ91D alloy. (C) 2003 Elsevier B.V. All rights reserved.

Comparative study of hydrogen storage in Li- and K-doped carbon materials - theoretically revisited

Hydrogen adsorption in alkali-doped carbon materials is investigated theoretically. Our calculations show that hydrogen molecules can be physically adsorbed on alkali-doped graphite at 0 K but such an adsorption is thermodynamically unfavourable. The binding energy of hydrogen adsorption decreases significantly with the increase in temperature and becomes nearly zero at ambient temperature. We suggest that it may be unlikely to observe any hydrogen uptake in alkali-doped carbon materials at or above ambient temperature in the TGA (thermogravimetric) system, the previously reported hydrogen uptake in alkali-doped carbon materials was caused by either uncyclable chemisorbed hydrogen on the defects of carbon (defects were produced by repeated heat treatment) and/or moisture adsorption. (C) 2004 Elsevier Ltd. All rights reserved.

Structure and thermal stability of Langmuir-Blodgett films of barium arachidate

The structures of multilayer Langmuir-Blodgett films of barium arachidate before and after heat treatment have been investigated using both atomic force microscopy (AFM) and grazing incidence synchrotron X-ray diffraction (GIXD). AFM gave information on surface morphology at molecular resolution while GIXD provided quantitative details of the lattice structures of the films with their crystal symmetries and lattice constants. As-prepared films contained three coexisting structures: two triclinic structures with the molecularchains tilted by about 20degrees from the film normal and with 3 x 1 or 2 x 2 super-lattice features arising from height modulation of the molecules in the films; a rectangular structure with molecules perpendicular to the film surface. Of these, the 3 x 1 structure is dominant with a loose correlation between the bilayers. In the film plane both superstructures are commensurate with the local structures, having different oblique symmetries. The lattice constants for the 3 x 1 structure are a(s) = 3a = 13.86 Angstrom, b(s) = b = 4.31 Angstrom and gamma(s) = gamma = 82.7degrees; for the 2 x 2 structure a(s) = 2a = 16.54 Angstrom, b(s) = 2b = 9.67 Angstrom, gamma(s) = gamma = 88degrees. For the rectangular structure the lattice constants are a = 7.39 Angstrom, b = 4.96 Angstrom and gamma = 90degrees. After annealing, the 2 x 2 and rectangular structures were not observed, while the 3 x 1 structure had developed over the entire film. For the annealed films the correlation length in the film plane is about twice that in the unheated films, and in the out-of-plane direction covers two bilayers. The above lattice parameters, determined by GIXD, differed significantly from the values obtained by AFM, due possibly to distortion of the films by the scanning action of the AFM tip. (C) 2004 Published by Elsevier B.V.

Significance of frictional heating for effects of high pressure homogenisation on milk

High pressure homogenisation (HPH) is a novel dairy processing tool, which has many effects on enzymes, microbes, fat globules and proteins in milk. The effects of HPH on milk are due to a combination of shear forces and frictional heating of the milk during processing; the relative importance of these different factors is unclear, and was the focus of this study. The effect of milk inlet temperature (in the range 10-50 degrees C) on residual plasmin, alkaline phosphatase, lactoperoxidase and lipase activities in raw whole bovine milk homogenised at 200 MPa was investigated. HPH caused significant heating of the milk; outlet temperature increased in a linear fashion (0(.)5887 degrees C/degrees C, R-2 =0-9994) with increasing inlet temperature. As milk was held for 20 s at the final temperature before cooling, samples of the same milk were heated isothermally in glass capillary tubes for the same time/temperature combinations. Inactivation profiles of alkaline phosphatase in milk were similar for isothermal heating or HPH, indicating that loss of enzyme activity was due to heating alone. Loss of plasmin and lactoperoxidase activity in HPH milk, however, was greater than that in heated milk. Large differences in residual lipase activities in milks subjected to heating or HPH were observed due to the significant increase in lipase activity in homogenised milk. Denaturation of beta-lactoglobulin was more extensive following HPH than the equivalent heat treatment. Inactivation of plasmin was correlated with increasing fat/serum interfacial area but was not correlated with denaturation of beta-lactoglobulin. Thus, while some effects of HPH on milk are due to thermal effects alone, many are induced by the combination of forces and heating to which the milk is exposed during HPH.

Corrosion resistance of anodised single-phase Mg alloys

This work studied the effect of the impurity iron and the alloying elements aluminium and zinc in single-phase substrate magnesium alloys on the corrosion resistance of the alloys after anodisation. It was found that increasing zinc content (0-2%) led to increased corrosion resistance of an anodised single-phase Mg-Zn alloy. The addition of Al lowered the corrosion resistance of an anodised commercial purity Mg-Al single-phase alloy, whereas the same addition was found to be beneficial to the corrosion resistance of an anodised high purity Mg-Al single-phase alloy. Heat-treatment made the substrate Mg-Al and Mg-Zn alloys more uniform and hence improved the corrosion resistance of the alloys after anodisation. The detrimental effect of iron impurity on corrosion performance of the unanodised substrate single-phase magnesium alloys was inherited by the anodised alloys. The corrosion resistance of the anodised Mg alloys was found to be closely correlated with the corrosion performance of the unanodised as-cast Mg alloys. (c) 2005 Elsevier B.V. All rights reserved.

Coal ash conversion into effective adsorbents for removal of heavy metals and dyes from wastewater

Fly ash was modified by hydrothermal treatment using NaOH solutions under various conditions for zeolite synthesis. The XRD patterns are presented. The results indicated that the samples obtained after treatment are much different. The XRD profiles revealed a number of new reflexes, suggesting a phase transformation probably occurred. Both heat treatment and chemical treatment increased the surface area and pore volume. It was found that zeolite P would be formed at the conditions of higher NaOH concentration and temperature. The treated fly ash was tested for adsorption of heavy metal ions and dyes in aqueous solution. It was shown that fly ash and the modified forms could effectively absorb heavy metals and methylene blue but not effectively adsorb rhodamine B. Modifying fly ash with NaOH solution would significantly enhance the adsorption capacity depending on the treatment temperature, time, and base concentration. The adsorption capacity of methylene blue would increases with pH of the dye solution and the sorption capacity of FA-NaOH could reach 5 x 10(-5) mol/g. The adsorption isotherm could be described by the Langmuir and Freundlich isotherm equations. Removal of copper and nickel ions could also be achieved on those treated fly ash. The removal efficiency for copper and nickel ions could be from 30% to 90% depending on the initial concentrations. The increase in adsorption temperature will enhance the adsorption efficiency for both heavy metals. The pseudo second-order kinetics would be better for fitting the dynamic adsorption of Cu and Ni ions. (c) 2005 Elsevier B.V. All rights reserved.

Toxinology in Australia's colonial era: A chronology and perspective of human envenomation in 19th century Australia

The medical management of those envenomed by snakes, spiders and poisonous fish in Australia featured extensively in the writings 19th century doctors, expeditioners and anthropologists. Against the background of this introduced medical doctrine there already existed an extensive tradition of Aboriginal medical lore; techniques of heat treatment, suction, incision and the application of plant-derived pharmacological substances featured extensively in the management of envenomed victims. The application of a hair-string or grass-string ligature, suctioning of the bite-site and incision were practised in a variety of combinations. Such evolved independently of and pre-dated such practices, which were promoted extensively by immigrant European doctors in the late 19th century. Pacific scientific toxinology began in the 17th century with Don Diego de Prado y Tovar's 1606 account of ciguatera. By the end of the 19th century more than 30 papers and books had defined the natural history of Australian elapid poisoning. The medical management of snakebite in Australia was the focus of great controversy from 1860 to 1900. Dogmatic claims of the supposed antidote efficacy of intravenous ammonia by Professor G.B. Halford, and that of strychnine by Dr. Augustus Mueller, claimed mainstream medical attention. This era of potential iatrogenic disaster and dogma was brought to a conclusion by the objective experiments of Joseph Lauterer and Thomas Lane Bancroft in 1890 in Brisbane; and by those of C.J. Martin (from 1893) and Frank Tidswell (from 1898), both of Sydney. The modern era of Australian toxinology developed as a direct consequence of Calmette's discovery, in Paris in 1894, of immune serum, which was protective against snakebite. We review the key contributors and discoveries of toxinology in colonial Australia.

Development and evaluation of a non-destructive adhesion test

The object of this work was to further develop the idea introduced by Muaddi et al (1981) which enables some of the disadvantages of earlier destructive adhesion test methods to be overcome. The test is non-destructive in nature but it does need to be calibrated against a destructive method. Adhesion is determined by measuring the effect of plating on internal friction. This is achieved by determining the damping of vibrations of a resonating specimen before and after plating. The level of adhesion was considered by the above authors to influence the degree of damping. In the major portion of the research work the electrodeposited metal was Watt's nickel, which is ductile in nature and is therefore suitable for peel adhesion testing. The base metals chosen were aluminium alloys S1C and HE9 as it is relatively easy to produce varying levels of adhesion between the substrate and electrodeposited coating by choosing the appropriate process sequence. S1C alloy is the commercially pure aluminium and was used to produce good adhesion. HE9 aluminium alloy is a more difficult to plate alloy and was chosen to produce poorer adhesion. The "Modal Testing" method used for studying vibrations was investigated as a possible means of evaluating adhesion but was not successful and so research was concentrated on the "Q" meter. The method based on the use of a "Q" meter involves the principle of exciting vibrations in a sample, interrupting the driving signal and counting the number of oscillations of the freely decaying vibrations between two known preselected amplitudes of oscillations. It was not possible to reconstruct a working instrument using Muaddi's thesis (1982) as it had either a serious error or the information was incomplete. Hence a modified "Q" meter had to be designed and constructed but it was then difficult to resonate non-magnetic materials, such as aluminium, therefore, a comparison before and after plating could not be made. A new "Q" meter was then developed based on an Impulse Technique. A regulated miniature hammer was used to excite the test piece at the fundamental mode instead of an electronic hammer and test pieces were supported at the two predetermined nodal points using nylon threads. This instrument developed was not very successful at detecting changes due to good and poor pretreatments given before plating, however, it was more sensitive to changes at the surface such as room temperature oxidation. Statistical analysis of test results from untreated aluminium alloys show that the instrument is not always consistent, the variation was even bigger when readings were taken on different days. Although aluminium is said to form protective oxides at room temperature there was evidence that the aluminium surface changes continuously due to film formation, growth and breakdown. Nickel plated and zinc alloy immersion coated samples also showed variation in Q with time. In order to prove that the variations in Q were mainly due to surface oxidation, aluminium samples were lacquered and anodised Such treatments enveloped the active surfaces reacting with the environment and the Q variation with time was almost eliminated especially after hard anodising. This instrument detected major differences between different untreated aluminium substrates.Also Q values decreased progressively as coating thicknesses were increased. This instrument was also able to detect changes in Q due to heat-treatment of aluminium alloys.

Valence-tautomeric RbMnFe Prussian blue analogues:composition and time stability investigation

Three different stoichiometric forms of RbMn[Fe(CN) ]y·zHO [x = 0.96, y = 0.98, z = 0.75 (1); x = 0.94, y = 0.88, z = 2.17 (2); x = 0.61, y = 0.86, z = 2.71 (3)] Prussian blue analogues were synthesized and investigated by magnetic, calorimetric, Raman spectroscopic, X-ray diffraction, and Fe Mössbauer spectroscopic methods. Compounds 1 and 2 show a hysteresis loop between the high-temperature (HT) Fe(S = 1/2)-CN-Mn(S = 5/2) and the low-temperature (LT) Fe(S = 0)-CN-Mn(S = 2) forms of 61 and 135 K width centered at 273 and 215 K, respectively, whereas the third compound remains in the HT phase down to 5 K. The splitting of the quadrupolar doublets in the Fe Mössbauer spectra reveal the electron-transfer-active centers. Refinement of the X-ray powder diffraction profiles shows that electron-transfer-active materials have the majority of the Rb ions on only one of the two possible interstitial sites, whereas nonelectron-transfer-active materials have the Rb ions equally distributed. Moreover, the stability of the compounds with time and following heat treatment is also discussed. © Wiley-VCH Verlag GmbH & Co. KGaA, 2009.

Autocatalytic deposition of composite coatings

The deposition and properties of electroless nickel composite coatings containing graphite, PTFE and chromium were investigated. Solutions were developed for the codeposition of graphite and chromium with electroless nickel. Solutions for the deposition of graphite contained heavy metal ions for stability, with non-ionic and anionic surfactants to provide wetting and dispersion of the particles. Stability for the codeposition of chromium particles was achieved by oxidation of the chromium. Thin oxide layers of 200 nm thick prevented initiation of the electroless reaction onto the chromium. A mechanism for the formation of electroless composite coatings was considered based on the physical adsorption of particles and as a function of the adsorption of charged surfactants and metal cations from solution. The influence of variables such as particle concentration in solution, particle size, temperature, pH, and agitation on the volume percentage of particles codeposited was studied. The volume percentage of graphite codeposited was found to increase with concentration in solution and playing rate. An increase in particle size and agitation reduced the volume percentage codeposited. The hardness of nickel-graphite deposits was found to decrease with graphite content in the as-deposited and heat treated condition. The frictional and wear properties of electroless nickel-graphite were studied and compared to those of electroless nickel-PTFE. The self-lubricating nature of both coatings was found to be dependent on the ratio of coated area to uncoated area, the size and content of lubricating material in the deposit, and the load between contacting surfaces. The mechanism of self-lubrication was considered, concluding that graphite only produced an initial lubricating surface due to the orientation of flakes, unlike PTFE, which produced true self-lubrication throughout the coating life. Heat treatment of electroless nickel chromium deposits at 850oC for 8 and 16 hours produced nickel-iron-chromium alloy deposits with a phosphorus rich surface of high hardness. Coefficients of friction and wear rates were intially moderate for the phosphorus rich layer but increased for the nickel-iron-chromium region of the coating.

The behaviour of antioxidants in polyolefins under conditions of U.V. exposure

The effects of antioxidants and stabilizers on the oxidative degradation of polyolefins (low density polyethylene [LDPE] and polypropylene [PPJ have been studied after subjecting to prior high temperature processing treatments. The changes in the both chemical and physical properties of unstabilized polymers occurring during processing were found to be strongly dependent on the amount of oxygen present in the mixer. Subsequent thermal and photo-oxidation showed very similar characteristics and the chromophore primarily responsible for:both thermo and photooxidative degradation of unstabilized polymers was found to be hydroperoxide formed during processing. Removal of hydroperoxide by heat treatment in an inert atmosphere although increasing ketonic carbonyl concentration, markedly decreased the rate of photo-oxidation, introducing an induction period similar to that of an unprocessed sample. It was concluded that hydroperoxides are the most important initiators in normally processed polymers during the early stages of photo-oxidation. Antioxidants such as metal dithiocarbamates which act by destroying peroxides into non-radica1 products were found to be efficient melt stabilizers for polyolefins and effective UV stabilizers during the initial photo-oxidation stage, whilst a phenolic antioxidant, n-octadecyl-3-(3',5'-di-terbutyl 4'hydroxypheny1) propionate (Irganox 1076) retarded photo-oxidation rate in the later stages. A typical 'UV absorber' 2-hydroxy-4-octyloxy-benzophenone (HOBP) has a minor thermal antioxidant action but retarded photo-oxidation at all stages. A substituated piperidine derivative, Bis [2.2.6.6-tetramethylpiperidlnyl-4] sebacate (Tinuvin 770) behaved as an pro-oxidant during thermal oxidation of polyolefins but was an effective stabilizer against UV light. The UV absorber, HOBP synergised effectively with both peroxide decomposing antioxidants (metal dithiocarbamates) and a chain-breaking antioxidant (Irganox 1076) during photo-oxidation of the poymers studed whereas the combined effect was additive during thermal oxidation. By contrast, the peroxide decornposers and chain-breaking antioxidant (Irganox 1076) which were effective synergists during thermal oxidation of LDPE· were antagonistic during photo-oxidation. The mechanisms of these processes are discussed.