Smaller Surface Energy Research Articles

Polarization conversion and lateral shifts in multilayered structure with finitely-gapped topological surface states

Abstract The polarizatison conversion and the Goos–Hänchen (GH) shifts of the reflected electromagnetic wave for the multilayered structure made of topological insulator (TI) layers with finite surface energy gap are investigated. The transfer matrix formalism is adopted to analyze the reflection of electromagnetic wave through the multilayered structure, and the influences of surface energy gap, thickness and number of the TI layers are discussed. We find that maximum polarization conversion rate can be obtained with appropriate surface energy gap of TI, and within a certain range of finite energy gap, the polarization conversion effect is stronger than that for the case under the infinite surface energy gap limit. Greater polarization conversion rate for TI with small surface energy gap can be found than that for TI with larger energy gap in some range of layer numbers. At large incident angles the GH shifts vary considerably with the layer number for TI with relatively larger energy gap. Result of the combined influence of surface energy gap and layer number shows that, there exists both the positive and negative enhancement peaks of the GH shifts, and for smaller energy gap, fewer TI layers are required to obtain the transition between positive and negative GH shifts.

Understanding the dynamic rheological property of cement paste blended with steel slag powder: From interparticle force and physico-chemical parameters of view

The blending of steel slag powder with cement can mitigate the carbon footprint of cementitious composites. The rheological properties of cement pastes are well known to be related to interparticle forces. However, the magnitude of the interparticle force depends on many physico-chemical factors. The influence of various factors on interparticle forces is not yet clear, making it difficult to control the rheological properties. In this paper, the interparticle force of steel slag powder blended cement paste was quantified and its relationships with dynamic rheological properties and basic physico-chemical parameters were explored. By means of this, the interparticle force was confirmed to could explain the effect of steel slag powder on the dynamic rheological properties of cement paste within 1 h. Moreover, how physico-chemical parameters affect the interparticle forces was clarified. A cement paste with large particle size and apolar surface energy, as well as small potential square, Debye length and small polar surface energy, can exhibit large interparticle force and high dynamic yield stress and plastic viscosity. A simple formula calculating interparticle force from basic parameters was proposed, which is believed to effectively and practically regulate the interparticle force. The relationships between interparticle forces, physico-chemical parameters, and rheological properties provide an effective reference for regulating the dynamic rheological properties of cement paste through fundamental parameters.

Nano- and Microemulsions in Biomedicine: From Theory to Practice.

Nano- and microemulsions are colloidal systems that are widely used in various fields of biomedicine, including wound and burn healing, cosmetology, the development of antibacterial and antiviral drugs, oncology, etc. The stability of these systems is governed by the balance of molecular interactions between nanodomains. Microemulsions as a colloidal form play a special important role in stability. The microemulsion is the thermodynamically stable phase from oil, water, surfactant and co-surfactant which forms the surface of drops with very small surface energy. The last phenomena determines the shortage time of all fluid dispersions including nanoemulsions and emulgels. This review examines the theory and main methods of obtaining nano- and microemulsions, particularly focusing on the structure of microemulsions and methods for emulsion analysis. Additionally, we have analyzed the main preclinical and clinical studies in the field of wound healing and the use of emulsions in cancer therapy, emphasizing the prospects for further developments in this area.

Cs3Cu2I5 Nanocrystals with Near-Unity Photoluminescence Quantum Yield for Stable and High-Spatial-Resolution X-ray Imaging

With almost negligible self-absorption and high photoluminescence quantum yield (PLQY), zero-electronic-dimensional Cs3Cu2I5 emerges as an excellent scintillator. Ball-milling is a desired method to prepare Cs3Cu2I5 scintillators at a large scale; however, the defects generated during ball-milling and large particle size hinder its scintillation properties. Theoretical analysis suggests that utilizing a molecule with a small surface energy and a passivation group during ball-milling could be a two-birds-with-one-stone strategy, which can simultaneously improve the PLQY of particles by defect passivation and decrease the particle size by minimizing the surface energy of particles and inhibiting particle rewelding. Accordingly, we successfully prepared Cs3Cu2I5 nanoparticles with a near-unity PLQY and smaller size using a passivator (nonaethylene glycol monododecyl ether, C12E9)-assisted ball-milling method. The interaction of C12E9 with Cs3Cu2I5 has been verified and could enhance the luminescence performance of Cs3Cu2I5. Further, the Cs3Cu2I5 nanoparticle coating delivered a spatial resolution of 17.5 lp mm–1@MTF = 0.2 in X-ray imaging and excellent stability under prolonged X-ray irradiation with total dose of 10.9 Gyair, equal to the dose of 108,000 medical chest X-ray inspections. These results suggest that this in situ passivator-assisted ball-milling method is effective for large-scale production of high-quality Cs3Cu2I5 nanoparticles with excellent scintillation performance.

Simulation of the Influence Mechanism of Hydrothermal Modification on Magnesium Hydroxide

AbstractTo overcome the drawbacks of strong polarity and easy agglomeration of ordinary magnesium hydroxide (MH), hydrothermal modification is customary applied to achieve its excellent dispersion as well as controllable morphology and particle size. In this paper, the influence mechanism of hydrothermal modification is elaborated from microstructure of MH. Structures and surface energy of crystal planes, affinity of water molecules for crystal planes, and crystal growth process are calculated by Materials Studio software. Furthermore, molecular dynamics simulations about solid–liquid interface model of MH and 1 mol L−1 NaOH solution at different temperatures are performed based on the theory of modified attachment energy model. The results indicate that (0 0 1) plane with the smallest surface energy has the strongest thermodynamic stability, equipping modified crystals with lamellar morphology and excellent dispersion. (0 0 1) plane cannot be dissolved easily because of the smallest affinity of water molecules. The magnesium atoms and hydroxyl groups on (1 0 1) plane dissolved are absorbed on (0 0 1) plane, resulting in the large value of I001/I101 in the X‐ray diffraction pattern. The relative growth rate of (1 0 1) plane R101 decreases with the increasing temperature, explaining why crystals become thicker with raising temperature.

A significantly improved hydrogen storage performance of nanocrystalline Ti–Fe–Mn–Pr alloy

Improving the activation performance and increasing the hydrogen storage capacity are the main problems faced by TiFe-based alloys. In this paper, alloys with chemical composition Ti1.1-xPrxFe0.8Mn0.2 (x = 0, 0.02, 0.04, 0.06, 0.08) are designed to achieve a reversible hydrogen storage capacity of 1.81 wt% in 15 min, which is close to the theoretical hydrogen storage capacity of TiFe alloy of 1.86 wt%. Alloys with Pr content x ≥ 0.04 can be directly activated without the incubation period. Transmission electron microscopy analysis found that doping Pr introduced TiFe (111) crystal plane with smaller surface energy, makes it easy for hydrogen atoms to diffuse from the surface to interior. Moreover, the addition of Pr significantly refines the grains and introduces a large number of grain boundaries and defects, improving the activation rate and kinetics. The physisorption results show that the specific surface area of the TiFe-based alloy after hydrogen absorption is significantly increased by doping Pr.

Adsorption characteristics of citric acid on Fe3O4 (001), (011), and (111) surfaces.

Magnetite (001), (011), and (111) surfaces were the focus of our study. Magnetite (001) surface has two different terminations, that is, Fetet and 2Feoct4O. Magnetite (011) surface has two different terminations, that is, 2Feoct4O and 2Fetet2Feoct4O. Magnetite (111) surface has six different terminations, that is, Fetet1, Feoct, Fetet2, 3Feoct, 4O1, and 4O2. Comparing surface energies of (001), (011), and (111) surfaces, (001) has the smallest surface energy, and (111) has the largest surface energy except for Feoct termination, which means that (001) surface is the easiest to be cleaved, followed by (011) and (111) surfaces. Comparing adsorption energies of citric acid onto (001), (011), and (111) surfaces, (111) has the largest adsorption energies except for Fetet2 termination, and (001) has the smallest adsorption energies, which means that (111) surface is the most active for citric acid adsorption, followed by (011) and (001) surfaces. PDOS (partial density of states) of citric acid adsorbed onto (001), (011), and (111) surfaces with different terminations shows that 3d orbital of Fe of magnetite surface does not contribute to the adsorption, and 4s orbital of Fe of magnetite surface and 2s and 2p orbitals of O of citric acid contribute to the adsorption.

Hysteresis effect in organic thin film transistors based on naphthalene tetracarboxylic diimide derivatives

Controlling the hysteresis effect in organic field-effect transistors (OFETs) is imperative to attain reliable devices that can be applied to complicated circuits for practical applications. In this Letter, we compare two naphthalene tetracarboxylic diimide (NDI) derivatives, namely, N,N′-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-BOCF3) and N,N′-bis(hexyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-C6), which are comprised of different side chains and exhibit significant variations in the hysteresis of electronic transfer potential caused by the electronic traps. Among them, NDI-BOCF3 manifests negligible hysteresis in OFETs, while the counterparts based on NDI-C6 show notable hysteresis. This work presents insight into the hysteresis phenomenon of NDIs in OFETs, which depends on various critical factors, including interfacial trap density, molecular structure, thin film growth mode, and surface energy. Particularly, NDI-C6 demonstrates two orders of magnitude higher interfacial trap density than that of NDI-BOCF3. Moreover, NDI-BOCF3 thin film displays small surface energy and higher surface coverage on the substrate, but the results are diametrically opposite in the case of NDI-C6. Considering these observations, we propose that the introduction of OCF3 group in NDI not only endues a well-matched surface energy that promotes uniform distribution of the thin film on n-Octyltrichlorosilane-modified SiO2 substrate but also provides a water-spelling feature which leads to fewer H2O/O2 absorption in the resulting thin films. Our findings offer a fundamental guideline to rationally design n-type organic semiconductors for the development of efficient OFETs with negligible hysteresis.

Improving the ordering and coercivity of L10-FePt nanoparticles by introducing PtAg metastable phase

Third element doping can accelerate ordering transformation and directly synthesize L10-FePt nanoparticles (NPs). However, this accelerating effect is limited due to the extremely low migration rate of Fe and Pt atoms. In this work, PtAg metastable phase is first introduced into chemical synthesis. Compared with the normal direct synthesis, the metastable phase method shows a much higher efficiency on promoting ordering transformation, and the FePt NPs present good dispersity, ultra-high ordering and coercivity up to 8600 Oe. The PtAg metastable phase is easy to be decomposed to Ag and Pt. The obtained Ag atoms migrate to surface area of the NPs because of their higher self-diffusion coefficients and the smaller surface energy. Simultaneously, the Fe atoms migrate into the NPs, and form the FePt phase. During the ordering diffusion of atoms, the mobility of Ag is much higher than that of Fe, which can generate a lot of vacancies in the lattice. These vacancies can obviously improve the migration rate of Fe and Pt atoms in the lattice, and powerfully promote ordering diffusion. Therefore, the introduced metastable phase can construct an optimal condition for the disorder-order transformation, and synthesize FePt NPs with highly ordering degree and good dispersity.

Effect of crystallographic orientation on structural response of silicon to femtosecond laser irradiation

Femtosecond laser has been widely utilized for modification of crystal structure to achieve desired functions. So far, however, the effect of crystallographic orientation on the induced structure by femtosecond laser processing has yet been comprehensively studied. The present work is undertaken in an attempt to fill this gap in our knowledge. To this end, commercial-purity Si is used as a target material and high-resolution transmission electron microscopy as well as electron backscatter diffraction are applied to examine the irradiation-induced microstructural changes. The structural response of the pulsed material is found to be principally influenced by the crystallographic orientation of the target surface. Specifically, at the surface orientation close to {111}, a pronounced amorphization effect is observed whereas no disordered material is detected at the orientations close to {100}. This phenomenon could be explained by the lowest crystallization speed required by the (111) surface due to its smallest surface energy. Compared with nanosecond laser, non-thermal melting induced by femtosecond laser induces mild thermal gradient and favors recrystallization.

Evolution of MoO3 nanobelts and nanoplatelets formation with flame synthesis

A co-flow premixed flat flame is applied to form MoO3 nanobelts and nanoplatelets in the gas phase. An experimental study is conducted with a thermophoretic sampling particle diagnostic (TSPD) technique to reconstruct the evolution of nanostructure formation. In order to investigate the growth mechanism of the nanobelts and nanoplatelets, samples were directly taken along the centerline at different positions in the flame to represent the essential morphological variations of material. Based on the sample information collected by TEM, a growth mechanism of nanobelts and nanoplatelets is proposed. The results indicate that nanobelts and nanoplatelets with well-defined structure are successfully synthesized in premixed flame. The precursor temperature has a significant impact on the morphology by affecting the vapor concentration in the flame. For synthetic nanobelts, the intermediate particles tend to grow along a specific direction with small surface energy, and the final morphology is determined by particle attachment. In contrast, the initial growth of the nanoplatelets is mainly characterized by vapor surface deposition/growth, and the formation of the final morphology relies on the coalescence of large particles and small particles.

Diurnal and Seasonal Variations of Surface Energy and CO2 Fluxes over a Site in Western Tibetan Plateau

Land surface process observations in the western Tibet Plateau (TP) are limited because of the abominable natural conditions. During the field campaign of the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX III), continuous measurements on the four radiation fluxes (downward/upward short/long-wave radiations), three heat fluxes (turbulent sensible/latent heat fluxes and soil heat flux) and also CO2 flux were collected from June 2015 through January 2017 at Shiquanhe (32.50° N, 80.08° E, 4279.3 m above sea level) in the western Tibetan Plateau. Diurnal and seasonal variation characteristics of these surface energy and CO2 fluxes were presented and analyzed in this study. Results show that (1) diurnal variations of the seven energy fluxes were found with different magnitudes, (2) seasonal variations appeared for the seven energy fluxes with their maxima in summer and minima in winter, (3) diurnal and seasonal variations of respiration caused by the biological and chemical processes within the soil were found, and absorption (release) of CO2 around 0.1 mg m−2 s−1 occurred at afternoon of summer (midnight of winter), but the absorption and release generally canceled out from a yearly perspective; and (4) the surface energy balance ratio went through both diurnal and seasonal cycles, and in summer months the slopes of the fitting curve were above 0.6, but in winter months they were around 0.5. Comparing the results of the Shiquanhe site with the central and eastern TP sites, it was found that (1) they all generally had similar seasonal and diurnal variations of the fluxes, (2) caused by the low rainfall quantity, latent heat flux at Shiquanhe (daily daytime mean always less than 90 W m−2) was distinctively smaller than at the central and eastern TP sites during the wet season (generally larger than 100 W m−2), and (3) affected by various factors, the residual energy was comparatively larger at Shiquanhe, which led to a small surface energy balance ratio.

Chataliytic activity of nano ZnO/Cu for degradation humic acid under ilumination outdoor light

One of the photocatalysts that is being developed for the degradation of humic acid is ZnO, because it is cheap, easy to obtain and the synthesis process is easy, large size ZnO has several disadvantages such as small surface area and energy band gap which are not suitable when applied to visible light. The research developed a method of making zno in nanometer size and composting to reduce bandgap. The maximum degradation of humic acid at nano ZnO doped Cu 7% which is equal to 54.12%. Nano characterization of nano ZnO doped Cu 7% doping using XRD and DRS UV-Vis spectra was found to be 27 nm and bandgap 5.27 eV.

Strong adhesion of polyvinylpyrrolidone-coated copper nanoparticles on various substrates fabricated from well-dispersed copper nanoparticle inks

In this study, we obtained copper nanoparticle (Cu NP) films exhibiting low resistivity and strong adhesion with respect to various substrates by drop-casting the Cu NP ink with polyvinylpyrrolidone (PVP) after being sintered at 250 °C. PVP functioned as a dispersant in the ink and as an adhesive at the interfaces between the Cu NPs and the substrates. Aggregation of the Cu NPs in the ink resulted in the creation of a porous NP film after drop-casting, and the contact area between the PVP-coated Cu NPs and the substrates was small, resulting in poor adhesion. The nuclear magnetic resonance (NMR) relaxation measurement of the Cu NP ink, which can determine the dispersibility of the undiluted Cu NPs, revealed that long dispersion time and optimal PVP concentration were required to produce a well-dispersed Cu NP ink with PVP. The well-dispersed ink resulted in dense Cu NP films and a large contact area, demonstrating strong adhesion. The ink was applied to various substrates, including glass, polyimide, polyphthalamide, liquid crystal polymer, and polytetrafluoroethylene, and these substrates, except polytetrafluoroethylene, showed strong adhesion. The weak adhesion of polytetrafluoroethylene can be attributed to the small surface energy change between the PVP-coated Cu NPs and the polytetrafluoroethylene substrate owing to the low surface energy of polytetrafluoroethylene. The well-dispersed Cu NP ink with PVP is expected to be applied to the production of adhesive Cu wiring on various substrates for printed electronics, except substrates exhibiting low surface energy such as polytetrafluoroethylene.

Direct Synthesis of L10-FePt Nanoparticles with High Coercivity via Pb Addition for Applications in Permanent Magnets and Catalysts

We report a promising strategy to directly synthesize L10-FePt nanoparticles for applications in permanent magnets and catalysts. The element Pb with lower melting point, smaller surface energy, an...

Self-ejections of multiple isolated slushes on disorderly grooved superhydrophobic surfaces

In this Letter, we developed a sprayable superhydrophobic coating with micro-sized disorder indentations to survey the self-ejections of isolated slushes on it during the defrosting process. The microstructures, chemical composition, hydrophobic characteristics, and self-ejection phenomenon of melting slushes on grooved superhydrophobic surfaces are presented. The grooved superhydrophobic surface demonstrates that multiple self-ejections of isolated melting slush off the original locations with no ice bridges or great surface energy release. In addition, the self-ejection of multiple isolated slushes observed generates enough kinetic energy and removes the residual melting slushes in ways of sweeping off. It is also found that the irregular melting slush with a greater deformation energy and surface contact area demonstrates shorter jumping distances compared to that with a spherical shape and low surface contact area. The observed short-distance self-ejection results from the defects of micro-pores on the indentations, leading to great dissipation in vapor pressures and reduced impact from volume fluctuations. Both the volume fluctuation of slush and the evaporation of intermediate liquid generate the pressure gradient in the upward direction and contribute to the self-ejection behavior of isolated melting slush. The results demonstrate the necessity of fabricating grooved superhydrophobic surfaces without micro-pores and conceptual feasibility of employing volume fluctuation of slush for the self-ejection of isolated single melting slush in the case of slushes with no ice bridges, small surface energy, and low inner vapor pressures.

A multi-layered composite assembly of Bi nanospheres anchored on nitrogen-doped carbon nanosheets for ultrastable sodium storage.

Bismuth (Bi) is a promising anode candidate for sodium ion batteries (SIBs) with a high volumetric capacity (3765 mA h cm-3) and moderate working potential but suffers from large volume change (ca. 250%) during the sodiation/desodiation process, resulting in pulverization of the electrode, electrical contact loss, excessive accumulation of solid electrolyte interfaces, etc., devastating the cycling stability of the electrode seriously. Addressing this issue significantly relies on rational micro- and nano-structuring. Herein, we prepared a 3D multi-layered composite assembly of Bi/carbon heterojunctions with 0D bismuth nanospheres distributed and anchored on 2D nitrogen-doped carbon nanosheets (NCSs), using a preorganization strategy by taking full advantage of the strong complexation ability of Bi3+. The multi-layered composite assembly is periodic and close-packed, with Bi nanospheres <25 nm, carbon nanosheets ∼30 nm, and an average interlayer space of ∼75 nm. Such a specific architecture provides abundant electrochemically active surfaces and ion migration channels as the Bi nanospheres are attached to the 2D nitrogen-doped carbon nanosheets via a point-to-surface pattern. Moreover, the mono-layer Bi nanospheres oriented along the 2D-surface of NCSs are kinetically favorable for the recognition of Na+ by the active sites of Bi nanospheres as well as for avoiding the long distance migration of Na+ (external diffusion of Na+). Furthermore, thermodynamically, the small size and high surface energy of ultrasmall Bi nanospheres could contribute to high ion mobility (internal diffusion of Na+) and promote electrochemical reactions as well. The multi-layered composite assembly of Bi@NCSs (ML-Bi@NCSs) not only provides a robust 3D framework guaranteeing the whole structural stability but also ensures direct and full contact of each active nano-building block with electrolyte, thereby forming a high-throughput electron/ion transport system. When evaluated as the anode for SIBs, ML-Bi@NCSs deliver superior high-rate capability up to 30 A g-1 (specific capacity: 288 mA h g-1) and long-term cycling stability (capacity retention: 95.8% after 5000 cycles at 10 A g-1 and 90.6% after 10 000 cycles at 20 A g-1, respectively).

Self‐Regulated Super‐Hydrophobic Cu/CuO Electrode Film Deposited by One‐Step High‐Power Sputtering

AbstractIn spite of advances in integrated circuit technology, dust and corrosion continue to play detrimental roles in electronic and device components such as electrodes and wires, causing possible short circuits and arcing, consequently undermining the long‐time durability of devices. Super‐hydrophobic Cu/CuO films with easy cleaning characteristics and excellent corrosion resistance are prepared by one‐step high‐power magnetron sputtering and tested under high salinity conditions. Self‐regulation of the preferred orientations from Cu (200) to Cu (111) and formation of micro/nano‐rod surface features can be tuned by changing the power density. After exposure for 96 h in air, CuO (111), which has a small surface energy, is produced in situ on the surface of the Cu (111) micro/nano‐rods. Such a super‐hydrophobic surface with a contact angle of 152.5° has attractive properties such as excellent protection against dust particles, easy cleaning, as well as long‐term corrosion resistance compared to conventional Cu metallization films. These results reveal that the Cu/CuO micro/nano‐rod electrode film has great potential in microelectronics, in particular in metal/ceramic circuit boards requiring high power densities and operated in environments with high salinity.

Novel and cutting-edge applications for a solvent-responsive superoleophobic–superhydrophilic surface: Water-infused omniphobic surface and separating organic liquid mixtures

Superoleophobic–superhydrophilic surface has arousing massive research interests owing to its remarkable advantages in applications including liquid-liquid separation, anti-fogging and liquid transportation. But such superwetting surface has been considered counterintuitive since a given superoleophobic surface tends to repel water based on the classical surface free energy theory. Although significant progresses have been achieved for fabricating such superwetting surfaces, the existing attempts for searching the most cutting-edge and state-of-the-art functions are still extremely rare. In this work, we have successfully fabricated a stable superoleophobic–superhydrophilic surface by spraying an all-in-one suspension containing silica nanoparticles, aluminium phosphate, and Capstone FS-50 in ethanol-water cosolvent. The stable coating on various substrates displayed clever solvent-responsive behavior that highly polar liquid droplets can quickly wet surface while nonpolar liquid droplet can bead up, even after suffering from mechanical and chemical attacks. Thanks to the superhydrophilic porous surface hierarchy, a novel water-infused slippery surface can be achieved without using any costly low-surface energy lubricants. Based on the selective wettability caused by polarity interaction difference, the coated mesh can successfully achieve repeatable separation of immiscible polar liquid-nonpolar liquid mixtures in a high-efficiency mode, even for the liquid pair with a small surface energy difference of 3.1 mJ m−2.

Effect of Nanoparticles Addition on the Microstructure and Properties of Lead-Free Solders: A Review

With the development of microelectronic packaging and increasingly specific service environment of solder joints, much stricter requirements have been placed on the properties of lead-free solders. On account of small size effect and high surface energy, nanoparticles have been widely used to improve the microstructure and properties of lead-free solders. Therefore, the composite solders bearing nanoparticles have recently attracted wide attention. This article reviewed the recent research on SnAgCu, SnBi, and SnZn composite solder alloys and introduced the effect of nanoparticles on their microstructure, mechanical properties, wettability, and reliability. The mechanism of nanoparticles strengthening was analyzed and summarized. In addition, the shortcomings and future development trends of nanoparticle-reinforced lead-free solders were discussed, which is expected to provide some theoretical reference for the application of these composite solder in 3D IC package.