The influence of MoS
2
–Al
2
O
3
nanofluid as a functional lubricant on the microstructure and corrosion resistance of hot-rolled steel surface was studied. Because of the excellent lubrication ...performance of the nanofluid, the rolled surface quality improved with a 18.2% and 69.5% reduction in surface roughness and oxide scale thickness, respectively, when compared with the base-fluid without nanoparticles. The further microstructure characterization determined that the grain size, local misorientation and deformed grain fraction of the steel decreased significantly. A diffusion layer of Al
2
O
3
, FeS and FeMo
4
S
6
was found in the outer oxide layer of rolled surface. Closely arranged Al
2
O
3
grains inhibited the oxidation of steel strips that the oxidation activation energy was increased by about 14.5%. Through density functional theory (DFT) calculation, the formation of FeS and FeMo
4
S
6
was attributed to the migration of Mo and S atoms from MoS
2
into the Fe lattice through substitutional and interstitial diffusion, respectively, with the energy barrier of 0.84 eV and 0.54 eV. Finally, the protection of diffusion layer, reduction in surface defects, and alleviation of residual stress and deformation resulted in the enhancement of corrosion resistance. This study provides a possible route to achieve surface enhancement during the hot rolling process.
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As a hot topic in recent years, molecular dynamics (MD) simulation has become an effective tool in tribochemistry and lubrication investigations, which provides unique insight on ...dealing with these issues from atomic scale. This review paper presents an overview of recent MD simulation studies on revealing the friction laws, wear mechanism and lubrication performance of materials and lubricants, which aims to provide guidance and reference for future theoretical investigations on revealing the essence of friction, wear and lubrication. MD simulation researches upon the tribology, tribochemistry and lubrication are summarized, focusing on the field of friction and wear mechanism, nano-tribology, liquid lubricants, lubricant additives, superlubricity phenomenon, etc. Besides, the challenges and problems remain to be considered, as well as future development directions of MD simulation are briefly discussed. With the help of MD method, the obstacle to tribology research caused by insufficient experimental methods can be reduced in the future.
Thermal-assisted and stress-induced triboreactions at friction interface.
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Tribology plays a crucial role in progress of industry and engineering. The dependence of interface ...conditions and interfacial reactions provides the strategies for friction reduction as well as anti-wear in industrial processes. That is to modify the surface structure of materials or tune the properties of lubricants. This review provides an overview on the important interface conditions and surface-induced tribological reactions with emphasis on the underlying of their formation and action mechanism. The tribological features of asperity, debris and surface texture are firstly dictated. Then the main surface-induced physicochemical reactions including wetting/dewetting, deposition/adsorption are discussed. In particular, the thermal, mechanical and electrical effects that trigger tribochemical reactions are also addressed. Finally, some deficiencies in related investigations are summarized, with perspectives for the development of tribology in both science research and industrial application.
Stainless steel has attracted significant attention in industrial and engineering applications. To improve its corrosion resistance, there are two major approaches that are to optimize the elemental ...composition and tune the microstructure. A comprehensive review of the main findings on the corrosion of stainless steel is presented, and some controversial issues are highlighted. First, the functional roles of alloying elements are discussed, including nonmetallic (B, C, and N) and metallic (Cr, Ni, Cu, and Mo) elements. Additionally, their detrimental and positive effects, as well as the corresponding mechanisms, are highlighted. Second, the microstructure‐induced corrosion of stainless steel is discussed, including the crystallographic‐orientation‐dependent corrosion, the dual influence of grain size and grain boundary distribution, texture, and defects in the matrix. In addition, nanostructured materials are mentioned herein. Third, challenges as well as research trends in the future are proposed with perspectives for the development of novel stainless steel in research and industrial applications.
The positive and negative effects of nonmetallic and metallic alloying elements on the corrosion resistance of stainless steel are shown. Their positive effects involve promoting the passive film formation, stabilizing passive film, as well as the unique intensifying effects of B, C, N. In particular, nonmetallic elements can suppress the anodic dissolution of metal by releasing oxyanions and stabilizing the electronic structure of Fe.
Abstract Harvesting electricity from ubiquitous water vapor represents a promising route to alleviate the energy crisis. However, existing studies rarely comprehensively consider the impact of ...natural environmental fluctuations on electrical output. Here, we demonstrate a bilayer polymer enabling self-sustaining and highly efficient moisture-electric generation from the hydrological cycle by establishing a stable internal directed water/ion flow through thermal exchange with the ambient environment. Specifically, the radiative cooling effect of the hydrophobic top layer prevents the excessive daytime evaporation from solar absorption while accelerating nighttime moisture sorption. The introduction of LiCl into the bottom hygroscopic ionic hydrogel enhances moisture sorption capacity and facilitates ion transport, thus ensuring efficient energy conversion. A single device unit (1 cm 2 ) can continuously generate a voltage of ~0.88 V and a current of ~306 μA, delivering a maximum power density of ~51 μW cm −2 at 25 °C and 70% relative humidity (RH). The device has been demonstrated to operate steadily outdoors for continuous 6 days.
Hydrogel-based evaporative cooling with a low carbon footprint is regarded as a promising technology for thermal regulation. Yet, the efficiency of hydrogel regeneration at night generally mismatches ...with vapor evaporation during the day, resulting in a limited cooling time span, especially in arid regions. In this work, we propose an efficient approach to improve hydrogel cooling performance, especially the cooling time span, with a bilayer structure, which comprises a bottom hydrogel layer and an upper aerogel layer. The microporous aerogel layer can reduce the saturation vapor density at the hydrogel surface by employing daytime radiative cooling, together with increased convective heat transfer resistance by thermal insulation, thus boosting the duration of evaporative cooling. Specifically, the microstructure of porous aerogel for efficient radiative cooling and vapor transfer is synergistically optimized with a cooling performance model. Results reveal that the proposed structure with a 2-mm-thick SiO
aerogel can reduce the temperature by 1.4 °C, meanwhile extending the evaporative cooling time span by 11 times compared to a single hydrogel layer.
The synthetic jet piezoelectric air pump is a potential miniature device for electronic cooling. In order to improve the performance of the device, a small-sized synthetic jet piezoelectric air pump ...is proposed in this work, which is mainly characterized by petal-shaped inlet channels. First, the structure and working principle of the piezoelectric vibrator and the proposed pump are analyzed. Then, three synthetic jet piezoelectric air pumps with different inlet channels are compared. These inlets are the direct channels, the diffuser/nozzle channels, and the petal-shaped channels, respectively. Furthermore, the performance of the synthetic jet piezoelectric air pump with the petal-shaped inlet channels is optimized by orthogonal tests. Finally, the simulation was used to investigate the heat dissipation capability of the synthetic jet piezoelectric pump. The experimental results show that among the three inlet channels, the petal-shaped channel can greatly improve the performance of the pump. The unoptimized pump with petal-shaped channels has a maximum flow rate of 1.8929 L/min at 100 V, 3.9 kHz. Additionally, the optimized pump with petal-shaped channels reaches a maximum flow rate of 3.0088 L/min at 100 V, 3.7 kHz, which is 58.95% higher than the unoptimized one. The proposed synthetic jet piezoelectric air pump greatly improves the output performance and has the advantages of simple structure, low cost, and easy integration. The convective heat transfer coefficient of the synthetic jet piezoelectric pump is 28.8 W/(m2·°C), which can prove that the device has a better heat dissipation capability.
Staying stably cool in the sunlight Zhao, Dongliang; Tang, Huajie
Science (American Association for the Advancement of Science),
11/2023, Volume:
382, Issue:
6671
Journal Article
Peer reviewed
Microporous ceramics passively cool buildings and reduce the need for air conditioners
Terrestrial surfaces exposed to sunlight absorb solar heat and shed heat back to outer space as infrared ...radiation. If the radiated heat is greater than the solar energy absorbed, then daytime radiative cooling is achieved passively, without any energy input. However, this approach requires materials that strongly reflect sunlight and simultaneously emit long-wavelength infrared light—the wavelength needed to escape Earth’s atmosphere and not be reflected back. Ceramics composed mainly of silica (SiO
2
) and alumina (Al
2
O
3
), and that permit long-wavelength infrared emission, can meet these requirements. Moreover, they are durable, thermostable, and water-resistant. On page 684 and 691 of this issue, Zhao
et al.
(
1
) and Lin
et al.
(
2
), respectively, describe microporous materials— a glass-based ceramic coating and a ceramic composite—that exhibit passive daytime radiative cooling and resistance to harsh environments. These advances may lead to more environmentally friendly ways for keeping buildings cool.
Abstract The reformation and characterisation of the passive film formed on ultra-thin 316 L after hydrogen charging is investigated by combining EBSD, TMDS, XRD, Synchrotron-based XPS, and ...electrochemical experiments. The results show that ultra-thin foil reforms a passive film after 12 h of hydrogen release in NaCl solution. The reformed passive film is half the thickness of the as-received passive film and is dominated by Cr oxides/hydroxides. The lattice extension caused by residual hydrogen accelerates Cr migration to form Cr 2 O 3 ; while the diffusible hydrogen occupies the cation vacancies and results in high defect density for the reformed passive film within 12 h.
Electrochemical and localized corrosion behavior of a 316 L SS/copper/316 L SS composite in 0.5 wt. % NaCl solution was investigated from cross-sectional and plane directions by electrochemical ...measurements and high-resolution microscopic examination. The galvanic coupling accelerated the dissolution at the internal surface and pitting attack at the external surface of the 316 L layer. Polarization up to 1 V/SCE resulted in formation of a corrosion product layer (ca. 992 nm) composed of metal oxides/hydroxides on top of the passive film, which consisted of a Fe2O3-rich outer layer (3.3 nm) and a Cr2O3-rich inner layer (4.1 nm). The copper corrosion was quite uniform.
The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.
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•Corrosion behavior of SCS composite was profoundly revealed.•316 L Corrosion occurs via galvanic corrosion and pitting.•Copper corrosion only occurs at higher polarization potential, in a uniform manner.•The corroded surface comprised corrosion product layer and bilayer passive film.
