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71.
The reaction between Pb and HNO3 has been investigated using the thermometric technique. Weight-loss measurements on the reaction were also obtained. As the HNO3 concentration is increased from 5×10–2 to 4mol l–1, the corrosion rate increases. This is shown thermometrically by a substantial increase in the maximum temperature attained, T
m, as well as a decrease in the time, t, required for reaching T
m. Dissolution of Pb in HNO3 is proposed to take place according to an autocatalytic mechanism. Passivation sets were detected in solutions 11 mol l–1 HNO3. A parallel indication between the thermometric technique and weight-loss measurements was obtained. The rate-determining step of the autocatalytic process involves HNO2 in dissolution of Pb in HNO3. This is supported by the results of addition of hydrazine to the solution. This additive raises the maximum measured temperature, without affecting the corresponding time necessary to reach it. The effect of addition of NaNO2, NaNO3, NaCl, Na2SO4, NaH2PO4 and NaClO4 on the reaction number, RN, of Pb in 4 mol l–1 HNO3 was examined. Only NaNO2 accelerates the dissolution reaction while the other salts show as inhibition effect. It was found that these additives inhibit dissolution due to the displacement of some cathodic depolarizing components, as NO2, from the active sites on the metal surface. The effect of addition of HCl, H2SO4, HClO4 and H3PO4 on the reaction number, RN, of Pb in 4 mol l–1 HNO3 was also investigated. The observed acceleration and retardation of the dissolution of Pb was found to be dependent on both the concentration and nature of anions of the extra acids added. 相似文献
72.
Silicon - An inexpensive spray pyrolysis technique was effectively used to form a p-type SnSb2S4 thin film on n-type Si wafer for the first time to produce SnSb2S4/n-Si heterojunction. The... 相似文献
73.
Abouelnaga Amal M. Meaz Talaat M. Othman Abdelmageed M. Ghazy Riyad A. El Nahrawy Amany M. 《SILICON》2021,13(3):623-631
Silicon - The nature of the opening silicate- based surface affects the chemical interaction, spectroscopic and antimicrobial efficiency. The aim of this approach was to evaluate the spectroscopic... 相似文献
74.
Haddaji Younesse Hamdane Hasna Majdoubi Hicham Mansouri Said Allaoui Driss El bouchti Mehdi Tamraoui Youssef Manoun Bouchaib Oumam Mina Hannache Hassan 《SILICON》2021,13(7):2389-2400
Silicon - Geopolymers produced with metakaolin (MK) and thermally untreated phosphate sludge (PS) are beneficial and environmentally advantageous materials, but their fragility limits its... 相似文献
75.
El Nahrawy Amany M. Hemdan Bahaa A. Abou Hammad Ali B. Othman Abdelmageed M. Abouelnaga Amal M. Mansour A. M. 《SILICON》2021,13(9):2979-2991
Silicon - Magnesium calcium silicate nanostructures (MCSNS) loaded with (0.0, 0.6, 0.9, and 1.2 wt%) of Cephradine-drug consisting of mesoporous particles were functionally prepared by sol-gel... 相似文献
76.
77.
Mansour N. Ben Djeridi W. Mir L. El 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(11):4360-4371
Journal of Inorganic and Organometallic Polymers and Materials - Nanoporous carbon matrix was prepared by the sol–gel process from pyrogallol-formaldehyde (PF) mixtures in water using picric... 相似文献
78.
Smith Robert El. Wekstein David R. Sullivan Robert H. 《IEEE transactions on bio-medical engineering》1970,(2):151-156
A multiplexing, demodulating, and recording telemetry system designed to process multiple pulse-coded temperature channels is described. The system provides complete control of recording and multiplexing sequences and timing, and gives a single analog signal in response to each sample of pulse-coded data. It identifies all channels and indicates to a computer when a new data sample is to be processed. The system is self-calibrating to maintain accuracy over extended data collection periods, and is inexpensive. 相似文献
79.
The properties of styrene/butadiene copolymers obtained by conventional emulsion and miniemulsion polymerizations were studied. Thin layer chromatography with flame ionization detection was used to determine the gel fraction of the copolymer in the latex particles as a function of conversion. It was found that the gel formation began at a higher conversion in the miniemulsion polymerization when compared with that in the conventional process. Also, a lower glass transition temperature was noted at the lowest conversion sampled (~25%), implying a higher initial butadiene monomer concentration within the nucleated miniemulsion monomer droplets when compared with particles formed conventionally. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4616–4622, 2006 相似文献
80.
Styrene/hexadecane miniemulsions were polymerized at 50°C using a redox initiator. The miniemulsions and their corresponding latexes were characterized in terms of size, polymerization rate, and surface properties. The resulting data were analyzed to elucidate the miniemulsion stabilization and polymerization mechanisms. It was found that the free surfactant concentration exceeded the critical micelle concentration when large amounts of surfactant (60 mM sodium lauryl sulfate) were used, resulting in simultaneous micellar and droplet nucleation. Most surfactant was on the surface of the droplets (85%) or particles (95%). The fractional surface coverage was proportional to the surfactant concentration to the 0.55 power. Using a particle diameter equation, the number of particles was calculated to be proportional to the surfactant concentration to the 1.35 power. Through direct particle size measurements, a power of 1.38 was confirmed. The rate of polymerization was determined by reaction calorimetry to be proportional to the number of particles to the 0.59 power, in contrast to classical Smith–Ewart kinetics for conventional emulsions (1.0 power). The average number of radicals per particle was estimated from the rate and number data, and varied with the particle diameter to the 0.97 power. The observed kinetic dependencies were validated through an extension of Smith–Ewart theory. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3987–3993, 2003 相似文献