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Processing and Thermomechanical Properties of PHA
Published in Martin Koller, The Handbook of Polyhydroxyalkanoates, 2020
Vito Gigante, Patrizia Cinelli, Maurizia Seggiani, Vera A. Alavarez, Andrea Lazzeri
Nucleating agents are used in polymers that are able to crystallize, with the aim of accelerating the crystallization and consequently the speed cycle times in processing. After the melting, the rate of solidification of the plastic into a useful shape controls the processing and cycle time. Pure PHB exhibits a high melting temperature (Tm, 177°C), a low crystallization temperature (Tc, 79°C), and few heterogeneous nuclei, which results in a slow crystallization process for PHB. These characteristics make it difficult to use PHB to make products via injection-molding. P(3HB-co-3HV) copolymers also exhibit similar slow nucleation behavior comparable to the homopolymer PHB. In general, the addition of a nucleating agent accelerates the crystallization of polymers and provides polymers with heterogeneous nuclei allowing a more rapid crystallization during the cool-down period after the polymer melts [101], since the nucleation density increases and the spherulite size decreases so that the crystallization rate is increased [102]. Various nucleating agents, such as orotic acid [103], α-cyclodextrin [104], boron nitride, talc, terbium oxide, lanthanum oxide [105], saccharin, and phthalimide [106] have been tested for enhancing the crystallization of PHA at elevated temperatures (see Figure 5.14).
Selected High-Energy Photon Applications
Published in Harry E. Martz, Clint M. Logan, Daniel J. Schneberk, Peter J. Shull, X-Ray Imaging, 2016
Harry E. Martz, Clint M. Logan, Daniel J. Schneberk, Peter J. Shull
The x-ray detector consists of an Industrial Quality, Inc. terbium oxide–doped scintillating glass plate that converts x-rays to visible light. The scintillator was optically coupled by a Nikon 60 mm Micro-Nikkor lens to a cooled 3072 × 2048 Quantix CCD camera. The camera has 14 bit dynamic range and a detector pitch of 9 μm. The distances between the source to the center of the single-shell target, and the shell to the scintillator, were chosen consistent with the phase-contrast imaging theory. The source-to-shell distance was 70 ± 5 mm. The shell-to-scintillator distance was 205 ± 5 mm, giving a geometric magnification of 3.9×. The pixel size at the shell is 2.3 μm. X-ray images of D-T in a Be(Cu) shell that have been processed with a band-pass filter are given in Figure 16.9 (Kozioziemski et al. 2005b). The left image shows the Be(Cu) shell partially filled with liquid D-T. The right image shows solid D-T after the Be(Cu) shell was cooled to 19.3 K (0.4 K below the triple-point temperature of D-T) and held at a constant temperature for 4 h. In both cases, a light-to-dark transition inside the single-shell target as shown in Figure 16.9 indicates the inner D-T surface. The projected image through the spherical, solid D-T shell is circular in shape, as expected based on previous experiments with optically transparent shells. The exposure time for these images was 30 min. The system has been optimized over the years. Recent work is given by Koch et al. (2009).
Investigation of good dopant (Sm, Cu, Tb, Mn, Sb) for radiation dosimetry in the γ-excited GdCa4O(BO3)3phosphor: mechanoluminescence study
Published in Radiation Effects and Defects in Solids, 2022
G. C. Mishra, Upendra K. Verma, S. J. Dhoble
The GdCa4O(BO3)3 with completely different dopants (Sm, Cu, Tb, Mn, Sb) were ready by a solid-state reaction method at high temperatures. Raw materials were Gadolinium oxide, Calcium Carbonate, Boric Acid, Antimony trioxide (all are A.R., Himedia), Cupric Oxide, Samarium Oxide, Manganese Dioxide (all are Extra Pure, LOBA), Terbium Oxide (99.9% purity, Sigma Aldrich). A stoichiometric ratio of all the raw materials was beached systematically followed by heat at around 750°C intended for 10 h and after that frozen gradually Again these samples were grounded and fired at 850℃ for another 10 h then cooled. The same process was repeated with different concentrations (0.05 to 1 mol%) of dopants (CuO, Sb2O3, Sm2O3, MnO2, Tb2O3). The chemical reaction is:
A series of new pyridine carboxamide complexes and self-assemblies with Tb(III), Eu(III), Zn(II), Cu(II) ions and their luminescent and magnetic properties
Published in Journal of Coordination Chemistry, 2019
Dorota Kwiatek, Maciej Kubicki, Tomasz Toliński, Wiesława Ferenc, Stefan Lis, Zbigniew Hnatejko
Compound 1 was found to decompose in two steps. The first step is related to the release of three BTC molecules, three water molecules and four methyl ester groups from L1 per formula unit in the range of 175–476 °C (Calcd: 40.81% and Found: 38.93%). After that the four remaining amide molecules without ester groups decomposed until 675 °C (Calcd: 37.83%, Found: 35.17%). The molecule of terbium oxide remained after the complex decomposition.
Morphological and photoluminescence study of NaSrB5O9: Tb3+ nanocrystalline phosphor
Published in Journal of Asian Ceramic Societies, 2018
Vaishali Raikwar, Vinod Bhatkar, Shreeniwas Omanwar
NaSr1-xB5O9:xTb3+ phosphors doped with various molar concentrations of Tb3+ (x = 0.005, 0.01, 0.02, 0.03, 0.05) were prepared by a modified combustion technique. The synthesis is based on an exothermic reaction between the fuel and oxidizer. Urea was used as the fuel and metal nitrates as the oxidizer. For complete combustion the oxidizer-to-fuel ratio should be one-to-one. All the precursors viz. sodium nitrate, strontium nitrate, urea and boric acid (as the boron source) were procured as analytical reagents (AR), weighed in stoichiometric proportions and dissolved in a minimum amount of distilled water. Terbium nitrate was prepared by adding dilute HNO3 to terbium oxide followed by continuous stirring. The precursor paste was mixed well to assure homogenization of the mass. A quartz container containing this paste was placed in a furnace maintained at around 550°C. After about 2–3 min a reaction with bright yellow flames started. The reaction continued for only a few seconds. As soon as the reaction was over, the quartz container was removed from the furnace and allowed to cool. The prepared phosphor was crushed to a fine powder using a mortar and pestle. The same process flow was followed for the different concentrations of Tb3+. The samples were subjected to X-ray diffraction (XRD) analysis using a Rigaku Miniflex diffractometer with Cu Kα radiation (λ = 1.54059 A°) operating at 40 kV and 30 mA. The XRD data was collected in the 2θ range from 10° to 70° at room temperature. Fourier transform infrared (FTIR) spectroscopy was conducted on a Shimatzu IR Prestige −21 analyser. The measurements concerning particle size were done with a nanoparticle tracking analysis (NTA) system that uses a laser to track the Brownian motion of particles in samples. The measurements of photoluminescence emission (PL) over the range of 450 to 650 nm and photoluminescence excitation spectra (PLE) over a 200 to 400 nm excitation range were conducted with a Hitachi F 7000 fluorescence spectrophotometer at room temperature. The spectral resolution of both the excitation and emission spectra widths of the monochromatic slits (1 nm) as well as of measurement conditions such as the photomultiplier tube detector’s sensitivity and scanning speed were kept constant for all the samples. Electron diffraction X-ray spectroscopy (EDX) for elemental analysis and field emission scanning electron microscopy (FESEM) for detecting the morphology of the samples was conducted on a Hitachi S-4800 FESEM with a maximum resolution of 1.0 nm and a variable acceleration voltage of 0.5–30 kV. All the samples were coated with a thin layer of gold in the FESEM analysis to avoid charging. The color chromaticity coordinates were obtained following the standards of the Commission International de I’Eclairage (CIE) using Radiant Imaging Color Calculator 2.0 software.