Cluster dynamics modeling of niobium and titanium carbide precipitates in α-Fe and γ-FeKorepanova, Nadezda; Gu, Long; Dima, Mihai; Xu, Hushan
doi: 10.1088/1674-1056/ac0cd0pmid: N/A
Kinetic behaviors of niobium and titanium carbide precipitates in iron are simulated with cluster dynamics. The simulations, carried out in austenite and ferrite for niobium carbides, and in austenite for titanium carbide, are analyzed for dependences on temperature, solute concentration, and initial cluster distribution. The results are presented for different temperatures and solute concentrations, compared to experimental data available. They show little impact of initial cluster distribution beyond a certain relaxation time and that highly dilute alloys with monomers only present a significantly different behavior from denser alloys or ones with different initial cluster distributions.
Enhancing the thermoelectric performance through the mutual interaction between conjugated polyelectrolytes and single-walled carbon nanotubesWan, Shuxun; Chen, Zhongming; Hao, Liping; Wang, Shichao; Li, Benzhang; Li, Xiao; Pan, Chengjun; Wang, Lei
doi: 10.1088/1674-1056/ac48f9pmid: N/A
We present a method of constructing composites composed of conjugated polyelectrolytes (CPEs) and single-walled carbon nanotubes (SWCNTs) to obtain a high-performing flexible thermoelectric generator. In this approach, three kinds of polymers, namely, poly[(1,4-(2,5-didodecyloxybenzene)-alt-2,5-thiophene] (P1), poly[(1,4-(2,5-bis-sodium butoxysulfonate-phenylene)-alt-2,5-thiophene] (P2), and poly[(1,4-(2,5-bis-acid butoxysulfonic-phenylene)-alt-2,5-thiophene] (P3) are designed, synthesized and complexed with SWCNTs as thermoelectric composites. The electrical conductivities of the CPEs/SWCNTs (P2/SWCNTs, and P3/SWCNTs) nanocomposites are much higher than those of non-CPEs/SWCNTs (P1/SWCNTs) nanocomposites. Among them, the electrical conductivity of P2/SWCNTs with a ratio of 1:4 reaches 3686 S⋅cm−1, which is 12.4 times that of P1/SWCNTs at the same SWCNT mass ratio. Moreover, CPEs/SWCNTs composites (P2/SWCNTs) display remarkably improved thermoelectric properties with the highest power factor (PF) of 163 μW⋅m−1 ⋅ K−2. In addition, a thermoelectric generator is fabricated with P2/SWCNTs composite films, and the output power and power density of this generator reach 1.37 μW and 1.4 W⋅m−2 (cross-section) at Δ T = 70 K. This result is over three times that of the thermoelectric generator composed of non-CPEs/SWCNTs composite films (P1/SWCNTs, 0.37 μW). The remarkably improved electrical conductivities and thermoelectric properties of the CPEs/SWCNTs composites (P2/SWCNTs) are attributed to the enhanced interaction. This method for constructing CPEs/SWCNTs composites can be applied to produce thermoelectric materials and devices.
Ultrafast proton transfer dynamics of 2-(2′-hydroxyphenyl)benzoxazole dye in different solventsSun, Simei; Zhang, Song; Song, Jiao; Guo, Xiaoshan; Jiang, Chao; Sun, Jingyu; Wang, Saiyu
doi: 10.1088/1674-1056/ac3734pmid: N/A
The excited-state intramolecular proton transfer of 2-(2′-hydroxyphenyl)benzoxazole dye in different solvents is investigated using ultrafast femtosecond transient absorption spectroscopy combined with quantum chemical calculations. Conformational conversion from the syn-enol configuration to the keto configuration is proposed as the mechanism of excited-state intramolecular proton transfer. The duration of excited-state intramolecular proton transfer is measured to range from 50 fs to 200 fs in different solvents. This time is strongly dependent on the calculated energy gap between the N-S0 and T-S1 structures in the S1 state. Along the proton transfer reaction coordinate, the vibrational relaxation process on the S1 state potential surface is observed. The duration of the vibrational relaxation process is determined to be from 8.7 ps to 35 ps dependent on the excess vibrational energy.
Quantum transport signatures of non-trivial topological edge states in a ring-shaped Su–Schrieffer–Heeger double-chain systemYe, Cheng-Zhi; Zhang, Lan-Yun; Xue, Hai-Bin
doi: 10.1088/1674-1056/ac34ffpmid: N/A
In the ring-shaped Su–Schrieffer–Heeger (SSH) double-chain, the quantum interference between the two different electron tunneling paths of the upper and lower chains has an important influence on the electron transport properties of non-trivial topological edge states. Here, we have studied the electron transport signatures of non-trivial topological edge states in a ring-shaped SSH double-chain system based on the wave-guide theory and transfer-matrix method. In the ring-shaped SSH double-chain with the upper chain being different from the lower one, it is demonstrated that the electron transmission probability displays the four and two resonance peaks associated with the non-trivial topological edge states in the weak and strong coupling regimes, respectively. Whereas in the case of the upper chain being the same as the lower one, the two transmission resonance peaks associated with the non-trivial topological edge states in the weak coupling regime are only found, and that in the strong coupling regime disappear that originated from the destructive interference between the two different electron tunneling paths of the upper and lower chains. Consequently, the variation of the number of transmission resonance peaks associated with the non-trivial topological edge states in the weak and strong coupling regimes suggests that an alternative scheme for detecting non-trivial topological edge states in the ring-shaped SSH double-chain system.
A new direct band gap silicon allotrope o-Si32Yang, Xin-Chao; Wei, Qun; Zhang, Mei-Guang; Hu, Ming-Wei; Li, Lin-Qian; Zhu, Xuan-Min
doi: 10.1088/1674-1056/ac11dbpmid: N/A
Silicon is a preferred material in solar cells, and most of silicon allotropes have an indirect band gap. Therefore, it is important to find new direct band gap silicon. In the present work, a new direct band gap silicon allotrope of o-Si32 is discovered. The elastic constants, elastic anisotropy, phonon spectra, and electronic structure of o-Si32 are obtained using first-principles calculations. The results show that o-Si32 is mechanically and dynamically stable and is a direct semiconductor material with a band gap of 1.261 eV.
Recent advances in organic, inorganic, and hybrid thermoelectric aerogelsLiang, Lirong; Wang, Xiaodong; Liu, Zhuoxin; Sun, Guoxing; Chen, Guangming
doi: 10.1088/1674-1056/ac2802pmid: N/A
The thermoelectric (TE) materials and corresponding TE devices can achieve direct heat-to-electricity conversion, thus have wide applications in heat energy harvesting (power generator), wearable electronics and local cooling. In recent years, aerogel-based TE materials have received considerable attention and have made remarkable progress because of their unique structural, electrical and thermal properties. In this review, the recent progress in both organic, inorganic, and composite/hybrid TE aerogels is systematically summarized, including the main constituents, preparation method, TE performance, as well as factors affecting the TE performance and the corresponding mechanism. Moreover, two typical aerogel-based TE devices/generators are compared and analyzed in terms of assembly modes and output performance. Finally, the present challenges and some tentative suggestions for future research prospects are provided in conclusion.
Facile fabrication of highly flexible, porous PEDOT:PSS/SWCNTs films for thermoelectric applicationsLiu, Fu-Wei; Zhong, Fei; Wang, Shi-Chao; Xie, Wen-He; Chen, Xue; Hu, Ya-Ge; Ge, Yu-Ying; Gao, Yuan; Wang, Lei; Liang, Zi-Qi
doi: 10.1088/1674-1056/ac3502pmid: N/A
High-performance organic composite thermoelectric (TE) materials are considered as a promising alternative for harvesting heat energy. Herein, composite films of poly (3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotubes (PEDOT:PSS/SWCNTs) were fabricated by utilizing a convenient solution mixing method. Thereafter, the as-prepared hybrid films were treated using sulfuric acid (H2SO4) to further optimize the TE performance. Film morphological studies revealed that the sulfuric acid treated PEDOT:PSS/SWCNTs composite samples all possessed porous structures. Due to the successful fabrication of highly conductive networks, the porous nano-architecture also exhibited much more excellent TE properties when compared with the dense structure of the pristine samples. For the post-treated sample, a high power factor of 156.43 μW⋅m−1⋅K–2 can be achieved by adjusting the content of CNTs, which is approximately 3 orders of magnitude higher than that of the corresponding untreated samples (0.23 μW⋅m−1⋅K–2). Besides, the obtained films also showed excellent mechanical flexibility, owing to the porous nanostructure and the strong π–π interactions between the two components. This work indicates that the H2SO4 treatment could be a promising strategy for fabricating highly-flexible and porous PEDOT:PSS/SWCNTs films with high TE performances.
Non-Rayleigh photon statistics of superbunching pseudothermal lightWei, Chao-Qi; Liu, Jian-Bin; Zhang, Xue-Xing; Zhuang, Rui; Zhou, Yu; Chen, Hui; He, Yu-Chen; Zheng, Huai-Bin; Xu, Zhuo
doi: 10.1088/1674-1056/ac0ba9pmid: N/A
Superbunching pseudothermal light has important applications in studying the second- and higher-order interference of light in quantum optics. Unlike the photon statistics of thermal or pseudothermal light is well understood, the photon statistics of superbunching pseudothermal light has not been studied yet. In this paper, we will employ single-photon detectors to measure the photon statistics of superbunching pseudothermal light and calculate the degree of second-order coherence. It is found that the larger the value of the degree of second-order coherence of superbunching pseudothermal light is, the more the measured photon distribution deviates from the one of thermal or pseudothermal light in the tail part. The results are helpful to understand the physics of two-photon superbunching with classical light. It is suggested that superbunching pseudothermal light can be employed to generate non-Rayleigh temporal speckles.