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71.
Internal residual stresses arise in glass-ceramics upon cooling down from the crystallization temperature. These stresses are due to the thermal expansion and the elastic mismatch between the crystalline and glassy phases. Therefore, the mechanical properties of glass-ceramics are likely to depend not only on their composition and microstructure but also on the type (tension or compression) and magnitude of these residual stresses. In this work, we critically review the most commonly used theoretical models concerning residual stresses in glass-ceramics and glass-matrix composites, taking into consideration the effects of crystallized volume fraction, crystal shape and thermal expansion anisotropy. We also discuss most of the reported measurements of residual stresses in these dual-phase materials using different techniques, such as X-ray diffraction, nuclear magnetic resonance, Raman and fluorescence spectroscopy, and indentation. The available models and experimental results regarding spontaneous microcracking due to residual stresses are also discussed. Finally, guidelines for future work are suggested. 相似文献
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74.
Johisner Penagos‐Llanos Olimpo García‐Beltrn J. A. Caldern Edgar Nagles J. J. Hurtado 《Electroanalysis》2019,31(4):695-703
The detection of Allura red (AR) by electrochemical reduction using a different electrode from the conventional mercury electrode is presented. A carbon paste with cobalt (II, III) oxide composite electrode (CoOx/CPE) is reported for the first time for the detection of AR. Moreover, others dyes such as tartrazine (TZ), sunset yellow (SY), amaranth (AM), Ponceaut 4‐R (P‐4R), and Sudan (SD) as well as pharmaceutical agents such as paracetamol (PMC) that are present in samples that contained AR did not show a reduced signal between 0.0 and ?0.3 V, which is the potential range where AR reduction was observed. The surface electroactivity was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The presence of CoOX increased the cathodic peak current for AR by more than 50 % and 65 % via CV and square wave voltammetry (SWV), respectively, compared with an unmodified carbon paste electrode. Under the optimal parameters, (pH=3.0, accumulation time (tACC)=60 s and accumulation potential (EACC)=0.50 V), the detection limit for AR was 0.05 μmol L?1. The new sensor was sensitive and stable for the detection of AR. Moreover, it was easily manufactured and very convenient for food samples such as soft and isotonic drinks as well as chili sauce. 相似文献
75.
Xiao-Ying Yu Jennifer Yao Edgar C. Buck Zihua Zhu 《Surface and interface analysis : SIA》2020,52(7):454-459
Trace analysis of nuclear materials in solid particles collected in the environment or particles in liquid slurry generated in nuclear material manufacturing processes can pinpoint elemental, organic, and isotopic signatures of nuclear fuel cycle activities and processes. Such information can support nuclear safeguards programs by increasing our ability to detect undeclared nuclear materials, routine activities for safeguarding at declared facilities, and illicit activities. However, trace radioactive material analysis in liquids and slurries is challenging using bulk approaches. For example, one drawback of sensitive analysis such as inductively coupled plasma mass spectrometry (ICP-MS) is that sample is consumed or destroyed as a result of the technical approach. We developed a vacuum compatible microfluidic interface to enable surface analysis of liquids and solid–liquid interactions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). In this work, we illustrate the initial results from the analysis of liquid uranium oxide standard solutions using in situ liquid SIMS. Because the liquid SIMS analysis is almost nondestructive, the same sample can then be analyzed by other analytical techniques or saved for future reference. Consequently, multimodal analysis is possible. Our results demonstrate that in situ liquid SIMS can be used as a new approach to analyze radioactive materials in liquid and slurry forms of relevance to diverse applications. 相似文献
76.
Nicholas L. Stokes Jonathan A. Edgar Andrew M. McDonagh Michael B. Cortie 《Journal of nanoparticle research》2010,12(8):2821-2830
Infrared-blocking coatings on window glass can be produced by dispersing gold nanorods into a polymer coating. The spectral selectivity of the coating is controlled by the shape and aspect ratio of the nanoparticles, which are in turn determined by the conditions applied during their synthesis. Coatings of nanorods in polyvinyl alcohol were deposited onto glass and characterized in both laboratory and sun-lit conditions. Selective attenuation of the near-infrared was demonstrated with the test panels transmitting approximately one-third of the incident solar radiation and absorbing nearly two-thirds. The high absorptive cross sections of the gold nanorods suggest that they can be applied in efficacious coatings at relatively low volume fractions. 相似文献
77.
Irina Krasnochtanova Andreas Rauh Marco Kletting Harald Aschemann Eberhard P. Hofer Karl-Michael Schoop 《Applied Mathematical Modelling》2010
This paper presents sophisticated interval algorithms for the simulation of discrete-time dynamical systems with bounded uncertainties of both initial conditions and system parameters. Since naive implementations of interval algorithms might lead to guaranteed enclosures of all system states which are too conservative to be practically useful, we present algorithmic extensions of classical approaches which are applicable to the simulation of non-cooperative systems with time-varying uncertain parameters. Overestimation arising in the interval evaluation of dynamical system models due to the wrapping effect is reduced by an exact pseudo-linear transformation of nonlinear state equations and by new heuristics for the subdivision of interval enclosures which especially prefer splitting of unstable intervals. To highlight the typical procedure for parameterization of interval-based simulation routines and to demonstrate their efficiency, a nonlinear model of biological wastewater treatment processes is discussed. For this application, we consider the maximum specific growth rate of substrate consuming bacteria as a time-varying uncertain parameter. Only worst-case bounds are assumed to be available for the range of this parameter while no information is provided about its actual variation rate. 相似文献
78.
Isaías Juárez-Ramírez Edgar Moctezuma Leticia M. Torres-Martínez Christian Gómez-Solís 《Research on Chemical Intermediates》2013,39(4):1523-1531
The deposition of TiO2 nanoparticles on SiC was carried out by mechanical milling under different conditions. SiC–TiO2 samples were used as photocatalysts for the degradation of organic dyes such as methylene blue and rhodamine B. A short time deposition of TiO2 nanoparticles was observed during mechanical milling (2 min at 200 rpm) to cover the SiC particles. The presence of SiC and TiO2 (anatase and rutile) was confirmed by means of X-ray diffraction after thermal treatment at 450 °C. The deposition of TiO2 on SiC was corroborated by scanning electron microscopy analysis; the thickness of the thin layer of TiO2 deposited on SiC increases as the proportion of TiO2 increases. The energy band gap values obtained for these compounds were around 3.0 eV. SiC–TiO2 photocatalysts prepared by mechanical milling exhibited better activity under UV-light irradiation for the degradation of methylene blue and rhodamine B than commercial TiO2 powder (titania P25). 相似文献
79.
Bin Li Haoyu Liu Muhammad Amin Lindsay A. Wegiel Lynne S. Taylor Kevin J. Edgar 《Cellulose (London, England)》2013,20(4):2137-2149
Naringenin (Nar) is an important bioactive flavonoid with poor organic solubility and oral bioavailability. It is highly promising for treatment of conditions including diabetes, hyperlipidemia, and hepatitis C infection. Amorphous solid dispersion (ASD) of Nar is an appealing way to enhance its solubility, and carboxylated cellulose esters are attractive polymers for this purpose because of their ability to stabilize drugs against crystallization in both solid and solution phases, while restricting drug release to the pH of the small intestine (ca. 6.8). We demonstrate that ASDs of Nar can be formed using such carboxylated cellulose derivatives as cellulose acetate adipate propionate (CAAdP), carboxymethylcellulose acetate butyrate (CMCAB) and hydroxypropylmethylcellulose acetate succinate (HPMCAS). We compare Nar solution concentrations and release profiles from these cellulosic ASDs to those from pure crystalline Nar, and to Nar ASD in poly(vinylpyrrolidinone) (PVP). We show that all polymers in this study form ASDs with Nar, that the PVP ASDs release Nar at both gastric (1.2) and small intestine (6.8) pH, and that the cellulosic polymers release Nar selectively at neutral pH. Solution concentrations of Nar are significantly enhanced from these ASDs. These preliminary studies indicate that HPMCAS, CAAdP, and CMCAB are practical ASD polymers for Nar due to their ability to generate and stabilize high solution concentrations, and their pH-triggered drug release. 相似文献
80.
Iván Escalona Edgar Del Carpio Lino Hernández Vito Lubes 《Journal of solution chemistry》2014,43(6):1001-1010
In this work, the ternary complex formation among copper(II), 6-methylpicolinic acid (H6Mepic) as primary ligand, and the amino acids aspartic acid (H2Asp), glutamic acid (H2Glu) and histidine (HHis) as secondary ligands, were studied in aqueous solution at 25 °C using 1.0 mol·dm?3 KNO3 as the ionic medium. Analysis of the potentiometric data using the least squares computational program LETAGROP indicates formation of the species [Cu(6Mepic)]+, Cu(6Mepic)(OH), [Cu(6Mepic)(OH)2]?, Cu(6Mepic)2 and [Cu(6Mepic)3]? in the binary Cu(II)–H6Mepic system. In the ternary Cu(II)–H6Mepic–H2Asp system the complexes [Cu(6Mepic)(H2Asp)]+, Cu(6Mepic)(HAsp), [Cu(6Mepic)(Asp)]? and [Cu(6Mepic)(Asp)(OH)]2? were observed. In the case of the Cu(II)–H6Mepic–H2Glu system the complexes Cu(6Mepic)(HGlu), [Cu(6Mepic)(Glu)]?, [Cu(6Mepic)(Glu)(OH)]2? and [Cu(6Mepic)(glu)(OH)2]3? were detected. Finally, in the Cu(II)–H6Mepic–HHis system the complexes [Cu(6Mepic)(HHis)]+, Cu(6Mepic)(His) and [Cu(6Mepic)(His)(OH)]? were observed. The species distribution diagrams as a function of pH are briefly discussed. 相似文献