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Thermal Energy Production in Nuclear Power Plants
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
where M is the number of photons, h is Planck’s constant (a fundamental constant of nature), and f is their frequency of vibration (in cycles per second). The value of Planck’s constant is approximately 6.6 × 10−34 kg m2/s or 6.6260695 × 10−34 J s = 4.1356675 × 10−15 eV s. Thus, a photon such as a 1 MeV gamma ray has a vibrational frequency of f = E/h = 1 × 106eV/4.1356675 × 10−15 eV s ≅ 2.42 × 1020 Hz. In other words, the kinetic energy is directly proportional to its frequency.
Neutrons and Other Important Nuclear Particles
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
One of the strangest and most important conclusions that came out of Einstein’s explanation of the photoelectric effect was that photons carried energy away from atoms and to other atoms in discrete packets that were integral multiples of a very small unit of “energy time” called Planck’s constant. Max Planck first discovered Planck’s constant in 1900. It is a “fundamental constant of nature,” which has the units of energy–time. It is usually represented by the symbol h, where h = 6.626 × 10−34 J · s. In eVs, its value is 4.135 × 10−15 eV · s.
Absorptiometric measurement
Published in C M Langton, C F Njeh, The Physical Measurement of Bone, 2016
Christopher F Njeh, John A Shepherd
That is, the energy of a photon is related to its frequency by h, a universal constant named Planck’s constant. Plank’s constant is in units of eV s and is equal to h = 4.14 × 10−15 eV s. We can relate photon energy to wavelength by substituting in equation (8.1) to equation (8.2) such that () E=hc/λeV.
Bismuth-doped g-C3N4/ZIF-8 heterojunction photocatalysts with enhanced photocatalytic performance under visible light illumination
Published in Environmental Technology, 2023
Qian Yang, Wensong Lin, Zhichang Duan, Sen Xu, Junnan Chen, Xin Mai
where , , , and represent bandgap energy, proportionality constant, absorption coefficient, Planck constant, optical frequency, respectively. From Figure 6(c,d), the band gap energies of g-C3N4, ZIF-8 are 2.70, 5.07 eV, respectively. This is similar to the results reported earlier [7,38]. We evaluated the flat band energy levels and semiconductor types of g-C3N4, CNZ-1.5 and CNZ-1.5(Bi)-12 by Mott–Schottky plots, as shown in Figure S2. According to the positive slopes in the figure, all samples can be identified as n-type semiconductors. So, the flat band energy positions of g-C3N4, CNZ-1.5 and CNZ-1.5(Bi)-12 are measured to be −0.89 eV, −0.83 eV and −0.81 eV versus Ag/AgCl (−0.53 eV vs. normal hydrogen electrode (NHE)), respectively. The conduction band potential () of n-type semiconductors is generally approximately equal to the flat band potential. Thus, the valence band potential VB position () of the samples was calculated from the empirical formula:
Realizing p-type NbCoSn half-Heusler compounds with enhanced thermoelectric performance via Sc substitution
Published in Science and Technology of Advanced Materials, 2020
Ruijuan Yan, Wenjie Xie, Benjamin Balke, Guoxing Chen, Anke Weidenkaff
where e is the elementary charge and h is the Planck constant [47]. For the NbCoSn compound, we assume that acoustic phonon scattering is the predominant scattering mechanism, thus λ = 0. According to the measured S and pH, the m* = 0.11me is obtained. With the m* = 0.11me and the Equation (2), we can plot S at 300 K as a function of pH, a plot well-known as a ‘Pisarenko relation’. As shown in Figure 6(b), the red line is the calculated Pisarenko plot, and the blue dots represent measured data of Nb1-zSczCoSn compounds. Most of the data lie on the calculated line, except for that of Nb0.93Sc0.07CoSn compound. The reason for such an exception is not clear yet. It is suspected that the second phase or/and the deviation of the composition may be responsible for such an exception.
The synthesis and enhanced photocatalytic activity of heterostructure BiOCl/TiO2 nanofibers composite for tetracycline degradation in visible light
Published in Journal of Dispersion Science and Technology, 2021
Sarenqiqige Bao, Haiou Liang, Chunping Li, Jie Bai
To investigate the light absorption properties of BiOCl/TiO2 nanofibers heterostructure, UV-visible absorption experiments are conducted, which is shown in Figure 4. Fibers, pure TiO2, and BiOCl only show the light absorption in the ultraviolet region, whereas the BTPF exhibits a red shift and the strong absorption in the visible region. Importantly, the band gap energy (Eg) values of the as-synthesized samples are calculated by the Equation (1):[44] where α, h, ν, and A is absorption coefficient, Planck constant, the light frequency, and proportionality constant, respectively. And n is 4 for the indirect transition, and n is 1 for direct transition. BiOCl is the indirect band gap semiconductor material, so its n value is 4.[45] Based on the Equation (1), the Eg of the samples can be deduced from the extrapolated tangent [11] and their values are 3.16, 3.24, and 2.55 eV for TiO2, BiOCl, and BTPF (Figure 4a), and 2.46 eV for BTCF (Figure 4b), respectively. Apparently, the BTCF composite exhibits the strongest visible-light adsorption ability compared with other samples, and possesses the narrowest band gap (Eg), it can be attributed to the following phenomena that the highly conductive CNFs provide more adsorption sites and electron transport space for the p-n heterostructure formed by BiOCl and TiO2.[37]