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Two different porcelain compositions were studied: a soft and a hard
one. DTA, optical non-contact dilatometry and DSC were used to evaluate the
thermal behaviour of the porcelain compositions with the aim to master the
suitable thermal cycle for each. Results were interpreted on the basis of
mineralogy and microstructure: the amorphous phase, abundant in soft porcelain,
plays an important role on thermal expansion (8·10–6
K–1 for soft and 6·10–6
K–1 for hard at 1000°C). Thermal expansion
behaviour as function of firing time was also studied. Non-contact dilatometry
characterisation of porcelain bodies enable to master the suitable thermal
cycle for the sintering. 相似文献
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Nouemsi Soubgui Epiphanie Tene Fongang Rufin Theophile Kamseu Elie Oum Lissouck Rene Andreola Fernanda Boubakar Likiby Rossignol Sylvie Leonelli Cristina 《Journal of Thermal Analysis and Calorimetry》2021,145(6):3003-3018
Journal of Thermal Analysis and Calorimetry - The influence of drying on the microstructure, physical and chemical properties of some tropical wood species has been investigated using... 相似文献
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Sara Guizzo Cristina Tortolini Federico Pepi Francesca Leonelli Franco Mazzei Francesca Di Turo 《Natural product research》2019,33(7):1015-1025
AbstractTraditional cleaning methods with organic solvents often are not suitable for removal of aged resin so researchers have to find new formulations. In this work, a case study is reported in which new microemulsions were applied on the surface of a painting covered by some aged resin layers used during a previous restoration. Based on the quality of the intervention and the analysis of a sample of the varnish carried out with both MALDI-TOF and ATR-IR spectrometers, it was conjectured that this undesired material could be an acrylic polymer. So it was chosen to use xylene, ethyl acetate and propylene carbonate (XYL and EAPC) microemulsions (O/W oil in water). The first is able to solubilise only acrylic polymers, the second may solve both acrylic and vinyl resins. The first has had the greatest effect allowing complete varnish removal and original artwork restoration. 相似文献
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Leonelli F Blesi F Dirito P Trombetta A Ceccacci F La Bella A Migneco LM Marini Bettolo R 《The Journal of organic chemistry》2011,76(16):6871-6876
The problem of constructing diastereoselectively the C/D ring system of stemarane diterpenes from a bicyclo[2.2.2]octane intermediate was solved resulting in very simple synthesis of (+)-13-stemarene 1. The obtaining of the latter represents also a formal synthesis of (+)-18-deoxystemarin 2. In the key step, the epimeric mixture 10, dissolved in toluene, was converted by the action of TsOH into (+)-stemar-13-en-15-one 28. 相似文献
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Angela LaBella Francesca Leonelli Ilse DeSalve LuisaM. Migneco Rinaldo MariniBettolo 《Helvetica chimica acta》2004,87(8):2120-2124
A new preparation and the isolation and spectroscopic characterization of 1,3,3‐trimethylbicyclo[2.2.2]octan‐2,6‐dione ( 3 ), a so far elusive key intermediate in the Liu–Ralitsch total synthesis of (+)‐norpatchoulenol ((+)‐ 1a ), is described. The preparation of 3 constitutes also a formal total synthesis of (±)‐iso‐norpatchoulenol ((±)‐ 1b ), since 3 is correlated to an intermediate in the Monti and co‐workers synthesis of (±)‐ 1b . 相似文献
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Francesca Leonelli Luisa Maria Migneco Alessio Valletta Rinaldo Marini Bettolo 《Molecules (Basel, Switzerland)》2021,26(9)
The scientific activity carried out over forty-five years on stemodane diterpenes and diterpenoids structure elucidation, biogenesis, biosynthesis, biological activity and biotransformations was reviewed. 相似文献
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Hervé K. Tchakouté Elie Kamseu Charles Banenzoué Claus H. Rüscher Fernanda Andreola Claudia C. L. Tchamo Cristina Leonelli 《Journal of Sol-Gel Science and Technology》2018,86(2):305-315
The main target of this work is to investigate the influence of ?-Al2O3 on the properties of metakaolin-based geopolymer cements. The kaolin used as starting material for producing geopolymer cements contains approximately 28 and 64% of gibbsite and kaolinite, respectively. This kaolin was transformed to metakaolins by calcination at 500, 550, 600, 650, and 700?°C for 1?h. Gibbsite contained in kaolin was transformed to γ-Al2O3 during the calcination process. The hardener was obtained by mixing commercial sodium silicate and sodium hydroxide solution (10?M) with a mass ratio sodium silicate/sodium hydroxide equal to 1.6:1. Geopolymer cements, GMK-500, GMK-550, GMK-600, GMK-650, and GMK-700, were obtained using the prepared hardener with a mass ratio hardener/metakaolin equal to 0.87:1. It could be seen that the specific surface area of metakaolins decreases with increasing the calcination temperature of kaolin owing to the formation of the particles of γ-Al2O3. The compressive strengths 18.21/29.14/36.61/36.51 increase in the course GMK-550/GMK-600/GMK-650/GMK-700. The X-ray patterns and micrograph images of geopolymer cements, GMK-600, GMK-650, and GMK-700, indicate the presence of γ-Al2O3 in their structure. It was typically found that γ-Al2O3 remains largely unaffected during the geopolymerisation, and therefore could act as an inert filler and reinforce the structure of geopolymer cements. 相似文献
10.
Elie Kamseu Antonino Rizzuti Paola Miselli Paolo Veronesi Cristina Leonelli 《Journal of Thermal Analysis and Calorimetry》2009,98(3):757-763
Noncontact dilatometry, compared to differential scanning calorimetry (DSC), was used together with scanning electron microscopy
and densification behavior studies to investigate the parameters that govern the kinetics of transformation of kaolin to mullite
during sintering. Three kaolinitc clays from Cameroon, with different SiO2/Al2O3 molar ratio, were examined. The temperatures of mullite nucleation were 973, 979, and 984 °C at 5 °C/min heating rate, respectively,
for values of SiO2/Al2O3 molar ratio equal to 4.22, 2.22, and 2.08. At 20 °C/min heating rate, the temperatures are shifted to higher values, 992,
997, and 1,001 °C. The mullitization phenomenon, which includes a first step of nucleation and a second one of crystal growth,
presented activation energy in the range of 650–730 kJ/mol, depending on the nature of the sample investigated. These values,
obtained by noncontact dilatometer measurements, were comparable to those obtained by means of DSC and are in agreement with
literature values. The difference in sintering kinetics for the three kaolinitic clays could explain the different morphologies
obtained for the mullite grains. 相似文献