Distribution Properties of Internal Air Voids in Ultrathin Asphalt Friction Course

The distribution characteristics of air voids in ultrathin asphalt friction course(UAFC) samples with different gradations and compaction methods were statistically analyzed using X-ray computed tomography(CT) and image analysis techniques. Based on the results, compared with the AC-5 sample, the OGFC-5mixture has a higher air void ratio, a larger air void size and a greater number of air voids, with the distribution of internal air voids being more uniform and their shapes being more rounded. The two-parameter Weibull function was applied to fit the gradation of air voids. The fitting results is good, and the function parameters are sensitive to changes in both mineral gradation and compaction method. Moreover, two homogeneity indices were proposed to evaluate the compaction uniformity of UAFC samples. Compared with the Marshall method,the SGC method is more conducive to improve the compaction uniformity of UAFC samples. The compaction method significantly influences the air void distribution characteristics and compaction uniformity of AC-5sample, but has a less significant impact on OGFC-5 sample. The experimental results in the study provides a solid foundation for further explorations on the internal structure and mixture design of UAFC.

Back interface passivation for ultrathin Cu(In,Ga)Se_(2) solar cells with Schottky back contact: A trade-off of electrical effects

Back interface passivation reduces the back recombination of photogenerated electrons, whereas aggravates the blocking of hole transport towards back contact, which complicate the back interface engineering for ultrathin CIGSe solar cells with a Schottky back contact. In this work, theoretical explorations were conducted to study how the two contradictory electrical effects impact cell performance. For ultrathin CIGSe solar cells with a pronounced Schottky potential barrier(E_(h)> 0.2 eV), back interface passivation produces diverse performance evolution trends, which are highly dependent on cell structures and properties. Since a back Ga grading can screen the effect of reduced recombination of photogenerated electrons from back interface passivation, the hole blocking effect predominates and back interface passivation is not desirable. However, when the back Schottky diode merges with the main pn junction due to a reduced absorber thickness,the back potential barrier and the hole blocking effect is much reduced on this occasion. Consequently, cells exhibit the same efficiency evolution trend as ones with an Ohmic contact, where back interface passivation is always advantageous.The discoveries imply the complexity of back interface passivation and provide guidance to manipulate back interface for ultrathin CIGSe solar on TCOs with a pronounced Schottky back contact.

Ultrathin and Air-Stable Lithium Metal Anodes with Superlong Cycling Life in Ether/Ester-Based Electrolytes

Ultrathin and air-stable Li metal anodes hold great promise toward high-energy and high-safety Li metal batteries(LMBs).However,the application of LMBs is technically impeded by existing Li metal anodes with large thickness,high reactivity,and poor performance.Here,we developed a novel and scalable approach for the construction of a 10-μm-thick flexible and air-stable Li metal anode by conformally encapsulating Li within a multifunctional VN film.Specifically,the highly lithiophilic VN layer guides a uniform deposition of Li,while abundant and multilevel pores arising from assembly of ultrathin nanosheets enable a spatially confined immersion of metallic Li,thus ensuring an ultrathin and sandwiched Li anode.More impressively,the strong hydrophobicity of VN surface can effectively improve the stability of anode to humid air,whereas the highly conductive framework greatly boosts charge transfer dynamics and enhances Li utilization and high-rate capability.Benefiting from such fascinating features,the constructed Li-VN anode exhibits ultrastable cycling stability in both ether(2500 h)and carbonate(900 h)electrolytes,respectively.Moreover,even exposed to ambient air for 12 h,the anode still can retain~78%capacity,demonstrating excellent air-defendable capability.This work affords a promising strategy for fabricating high-performance,high-safety,and low-cost LMBs.

A 10-μm Ultrathin Lithium Metal Composite Anodes with Superior Electrochemical Kinetics and Cycling Stability

Lithium metal is a promising candidate for the promotion of the next generation high energy density batteries.The employment of ultrathin Li metal anode with controllable thickness could enable a higher efficiency of Li utilization.Herein,a simple method to fabricate free-standing 10μm ultrathin Li metal anode is developed in this work.A three-dimensional MnO_(x)-coated CNT framework is constructed through a facile hydrothermal process,utilizing as a host for molten Li infusion,which could not only put forward a simple strategy to modulate the thickness of Li metal film but also restricts the volume expansion.The abundant MnO_(x)nanoparticles acting as lithiophilic sites reduce the Li nucleation barrier and optimize the electrochemical kinetics at the anode/electrolyte interface.As a result,the ultrathin Li composite anode exhibits a superior lifespan expanded to 2000 cycles in a symmetric cell,as well as a better capacity and rate capability than that of bare Li anode in full cell,fulfilling the requirements of high energy density and stable cycling life.Furthermore,a wave-shaped Li metal pouch cell based on the ultrathin Li composite anode is assembled that exhibits remarkable mechanical bending toleration and cyclic stability,demonstrating large potential application in the field of flexible wearable devices.

Ultrathin NiO/Ni_(3)S_(2)Heterostructure as Electrocatalyst for Accelerated Polysulfide Conversion in Lithium-Sulfur Batteries

The practical application of Lithium-Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high-sulfur content and low electrolyte/sulfur ratio.Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium-sulfur batteries.Herein,ultrathin nonlayered NiO/Ni_(3)S_(2)heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)_(2)templates to improve the utilization of sulfur and facilitate stable cycling of batteries.As a multifunction catalyst,NiO/Ni_(3)S_(2)not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li_(2)S formation and transformation,which are verified by both in-situ Raman spectroscopy and electrochemical investigations.Thus,the cell with NiO/Ni_(3)S_(2)as electrocatalyst delivers an area capacity of 4.8 mAh cm^(-2)under the high sulfur loading(6 mg cm^(-2))and low electrolyte/sulfur ratio(4.3 pL mg^(-1)).The strategy can be extended to 2D Ni foil,demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities.The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium-sulfur batteries.

Molecular dynamics study on temperature and strain rate dependences of mechanical tensile properties of ultrathin nickel nanowires

Based on the EAM potential, a molecular dynamics study on the tensile properties of ultrathin nickel nanowires in the （100〉 orientation with diameters of 3.94, 4.95 and 5.99 nm was presented at different temperatures and strain rates. The temperature and strain rate dependences of tensile properties were investigated. The simulation results show that the elastic modulus and the yield strength are gradually decreasing with the increase of temperature, while with the increase of the strain rate, the stress--strain curves fluctuate more intensely and the ultrathin nickel nanowires rupture at one smaller and smaller strain. At an ideal temperature of 0.01 K, the yield strength of the nanowires drops rapidly with the increase of strain rate, and at other temperatures the strain rate has a little influence on the elastic modulus and the yield strength. Finally, the effects of size on the tensile properties of ultrathin nickel nanowires were briefly discussed.

GaN MOS-HEMT Using Ultrathin Al_2O_3 Dielectric with f_(max) of 30.8GHz

We report on a GaN metal-oxide-semiconductor high electron mobility transistor （MOS-HEMT） using atomic-layer deposited （ALD） A1203 as the gate dielectric. Through decreasing the thickness of the gate oxide to 3.5nm,a device with maximum transconductance of 130mS/mm is produced. The drain current of this 1/~m gate- length MOS-HEMT can reach 720mA/mm at ＋ 3.0V gate bias. The unity current gain cutoff frequency and maxi- mum frequency of oscillation are obtained as 10.1 and 30.8GHz,respectively.

Effectof Neutral Traps on Tunneling Current and SILC in Ultrathin Oxide Layer

The effect of neutral trap on tunneling currentin ultrathin MOSFETs is investigated by num erical analy- sis.The barrier variation arisen by neutral trap in oxide layer is described as a rectangular potential well in the con- duction band of Si O2 .The different barrier variation of an ultrathin metal- oxide- sem iconductor(MOS) structure with oxide thickness of4nm is numerically calculated.It is shown that the effect of neutral trap on tunneling cur- rent can not be neglected.The tunneling current is increased when the neutral trap exists in the oxide layer.This simple m odel can be used to understand the occurring mechanism of stress induced leakage current.

Stress Induced Leakage Current in Different Thickness Ultrathin Gate Oxide MOSFET

A study of the gate current variation is presented for various thickness ultrathin gate oxides ranging from 1.9 to 3.0nm under the constant voltage stress.The experimental results show the stress induced leakage current(SILC) includes two parts.One is due to the interface trap-assisted tunneling.The other is owing to the oxide trap-assisted tunneling.

Early gastric cancer diagnostic ability of ultrathin endoscope loaded with laser light source

BACKGROUND Conventionally, the low luminous intensity, low image resolution, and difficulty in operation have been reported with the ultrathin endoscope. However, it has markedly advanced recently. The improvement of the diagnostic ability is expected.AIM To compare the early gastric cancer diagnostic ability of an ultrathin endoscope loaded with a laser light source and that of the conventional endoscope.METHODS The target subjects were 375 consecutive patients who underwent endoscopy at our hospital for post-endoscopic submucosal dissection follow-up of gastric cancer from January to August 2018. During endoscopy, the ultrathin endoscope was used in 140 patients(37.3%), and the conventional endoscope was used in235 patients(62.7%). Patient background was adjusted using the propensity score matching method, and gastric cancer detection ability was evaluated in the two groups.RESULTS The gastric cancer detection rate was 7.8% in the ultrathin endoscope group and7.0% in the conventional endoscope group, and the mean intragastric observation time was 4.1 ± 1.7 min in the ultrathin endoscope group and 4.1 ± 1.9 min in the conventional endoscope group, showing no significant differences between the groups. Moreover, the biopsy implementation rate was 31.8% in the ultrathin endoscope group and 41.1% in the conventional endoscope group, and the biopsy prediction rate was 17.9% and 13.2%, respectively, showing no significant differences between the groups.CONCLUSION The gastric cancer diagnostic ability of the ultrathin endoscope loaded with a laser light source was comparable to that of the conventional endoscope. The observation time was also comparable. Thus, endoscopy using the ultrathin endoscope loaded with the laser light source would be the first option in screening examinations of gastric cancer due to its low invasion.

Fabrication of Ultrathin SiO_2 Gate Dielectric by Direct Nitrogen Implantation into Silicon Substrate

Nitrogen implantation in silicon substrate at fixed energy of 35keV and split dose of 10 14～5×10 14cm -2 is performed before gate oxidation.The experiment results indicate that with the increasing of implantation dose of nitrogen,oxidation rate of gate decreases.The retardation in oxide growth is weakened due to thermal annealing after nitrogen implantation.After nitrogen is implanted at the dose of 2×10 14cm -2,initial O 2 injection method which is composed of an O 2 injection/N 2 annealing/main oxidation,is applied for preparation of 3 4nm gate oxide.Compared with the control process,which is composed of N 2 annealing/main oxidation,initial O 2 injection process suppresses leakage current of the gate oxide.But Q bd and HF C-V characteristics are almost identical for the samples fabricated by two different oxidation processes.

2D mesoporous ultrathin Cd0.5Zn0.5S nanosheet:Fabrication mechanism and application potential for photocatalytic H2 evolution

Two-dimensional mesoporous ultrathin Cd0.5Zn0.5S nanosheets with a thickness of~1.5 nm were fabricated using a multistep chemical transformation strategy involving inorganic–organic hybrid ZnS-ethylenediamine(denoted as ZnS(en)0.5)as a hard template.Inorganic–organic hybrid ZnS(en)0.5,Cd0.5Zn0.5S(en)x,and Cd0.5Zn0.5S nanosheets were sequentially fabricated,and their transformation processes were analyzed in detail.The fabricated Cd0.5Zn0.5S nanosheets exhibited high photocatalytic hydrogen evolution reaction activity in the presence of a sacrificial agent.The Cd0.5Zn0.5S nanosheets exhibited remarkably high H2 production activity of~1395μmol∙h^−1∙g^−1 in pure water with no co-catalyst,which is the highest value reported thus far for bare photocatalysts,to the best of our knowledge.The high activity of these nanosheets is attributed to their distinct nanostructure(e.g.,short transfer distance of photoinduced charge carriers,large number of unsaturated surface atoms,and large surface area).Moreover,ternary NiCo2S4 nanoparticles were employed to facilitate the charge separation and enhance the surface kinetics of H2 evolution.The H2 production rate reached~62.2 and~2436μmol∙h^−1∙g^−1 in triethanolamine and pure water,respectively,over the NiCo2S4/Cd0.5Zn0.5S heterojunctions.The result indicated that the Schottky junction was critical to the enhanced activity.The proposed method can be used for fabricating other highly efficient CdZnS-based photocatalysts for solar-energy conversion or other applications.

Ultrathin 2D Metal–Organic Framework Nanosheets In situ Interpenetrated by Functional CNTs for Hybrid Energy Storage Device

The controllable construction of two-dimensional(2D)metal–organic framework(MOF)nanosheets with favorable electrochemical performances is greatly challenging for energy storage.Here,we design an in situ induced growth strategy to construct the ultrathin carboxylated carbon nanotubes(C-CNTs)interpenetrated nickel MOF(Ni-MOF/C-CNTs)nanosheets.The deliberate thickness and specific surface area of novel 2D hybrid nanosheets can be effectively tuned via finely controlling C-CNTs involvement.Due to the unique microstructure,the integrated 2D hybrid nanosheets are endowed with plentiful electroactive sites to promote the electrochemical performances greatly.The prepared Ni-MOF/C-CNTs nanosheets exhibit superior specific capacity of 680 C g^−1 at 1 A g^−1 and good capacity retention.The assembled hybrid device demonstrated the maximum energy density of 44.4 Wh kg^−1 at a power density of 440 W kg^−1.Our novel strategy to construct ultrathin 2D MOF with unique properties can be extended to synthesize various MOF-based functional materials for diverse applications.

Engineering an ultrathin amorphous TiO2 layer for boosting the weatherability of TiO2 pigment with high lightening power

TiO2 pigments are typically coated with inert layers to suppress the photocatalytic activity and improve the weatherability. However, the traditional inert layers have a lower refractive index compared to TiO2, and therefore reduce the lightening power of TiO2. In the present work, a uniform, amorphous, 2.9-nm-thick TiO2 protective layer was deposited onto the surface of anatase TiO2 pigments according to pulsed chemical vapor deposition at room temperature, with Ti Cl4 as titanium precursor. Amorphous TiO2 coating layers exhibited poor photocatalytic activity, leading to a boosted weatherability. Similarly, this coating method is also effective for TiO2 coating with amorphous SiO2 and SnO2 layers. However, the lightening power of amorphous TiO2 layer is higher than those of amorphous SiO2 and SnO2 layers. According to the measurements of photoluminescence lifetime, surface photocurrent density, charge-transfer resistance, and electron spin resonance spectroscopy, it is revealed that the amorphous layer can prevent the migration of photogenerated electrons and holes onto the surface, decreasing the densities of surface electron and hole, and thereby suppress the photocatalytic activity.

The origin of sulfuryl-containing components in SEI from sulfate additives for stable cycling of ultrathin lithium metal anodes

In the light of wireless and non-fossil society based on portable electronics, electric vehicles, and smart grids, secondary batteries with higher energy density, faster charge, and safer operation are pursued persistently [1]. Nowadays, commercial lithium(Li)-ion batteries have been practically applied in our daily life. However,the energy density of Li-ion batteries based on intercalation chemistry is approaching to the theoretical value due to the limited specific capacity of graphite anode(372 mA h g-1) [2].

Ultrathin nanosheets of cobalt-nickel hydroxides hetero-structure via electrodeposition and precursor adjustment with excellent performance for supercapacitor

A homogeneous better-dispersed ultrathin nanosheets（ca. 5 nm） of cobalt-nickel layered double hydroxides（LDH） supported on nickel foam scaffold was synthesized using controllable electrodeposition approach for high efficiency electrode materials of new supercapacitor. The morphology and electrochemical performances of the samples can be controlled by adjusting the precursor ratio, i.e., Ni（OAc）2/Co（NO3）2 molar ratio in the electrodeposition approach. With the increase of this molar ratio, the electrochemical performances give a volcano trend. When the optimized molar ratio is 0.64/0.36, the hybrid delivered a high specific capacitance of 1587.5 F g-1 at a current density of 0.5 A g-1, with good rate capability（1155 F g-1 was retained even at 10 A g-1） and a robust recycle stability（remaining 91.5% after 1000 cycles at 5 A g-1）. The good performance could be attributed to the enlarged interlayer spacing, ultrathin nanosheets and synergistic effects between Co（OH）2 and Ni（OH）2. Furthermore, an asymmetric supercapacitor with a high energy density of 34.5 Wh kg-1 at 425 W kg-1 and excellent cycling stability of 85.4% after 5000 charge-discharge cycles at 2 A g-1 was fabricated. We believe that this fantabulous new electrode material would have encouraging applications in electrochemical energy storage and a wide readership.

High performance perovskite solar cells using TiO2 nanospindles as ultrathin mesoporous layer

Single crystal anatase TiO2 nanospindles （NSs） with highly exposed {101} facets were synthesized and employed as electron transport materials （ETMs） in perovskite solar cells （PSCs）. Time-resolved photoluminescence （TRPL） spectra revealed that the TiO2 NSs are more effective than TiO2 nanoparticles in accepting electrons from perovskite. Moreover. the TiO2 nanospindles further endowed the PSCs with good reproducibility and suppressed hysteresis. The best device with TiO2 NSs as ETMs yielded power conversion efficiency （PCE） of 19.6%, demonstrating that the home-made TiO2 NSs is a good ETM for PSCs.

An accurate design of graphene oxide ultrathin flat lens based on Rayleigh-Sommerfeld theory

Graphene oxide （GO） ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are designed based on the Fresnel diffraction model, which uses a paraxial approximation for low numerical aperture （NA） focusing process. Herein we develop a lens design method based on the Rayleigh-Sommerfeld （RS） diffraction theory that is able to unambiguously determine the radii of each ring without the optimization process for the first time. More importantly, the RS design method is able to accurately design GO lenses with arbitrary NA and focal length. Our design is experimentally confirmed by fabricating high NA GO lenses with both short and long focal lengths. Compared with the conventional Fresnel design methods, the differences in ring positions and the resulted focal length are up to 13.9% and 9.1%, respectively. Our method can be further applied to design high performance flat lenses of arbitrary materials given the NA and focal length requirements, including metasurfaces or other two-dimensional materials.

A facile path from fast synthesis of Li-argyrodite conductor to dry forming ultrathin electrolyte membrane for high-energy-density allsolid-state lithium batteries

All-solid-state lithium batteries(ASSLBs),utilizing sulfide solid electrolyte,are considered as the promising design on account of their superior safety and high energy density,whereas the time-consuming preparation process of sulfide electrolyte powders and the thickness of electrolyte layer hinder their practical application.Herein,an innovative ultimate-energy mechanical alloying plus rapid thermal processing approach is employed to rapidly synthesize the crystalline Argyrodite-type conductor Li_(5.3)PS_(4.3)ClBr_(0.7)(LPSCIBr)with superior ionic conductivity(11.7 mS cm^(-1)).Furthermore,to realize the higher energy density of the battery,an ultrathin LPSCIBr sulfide electrolyte membrane with superior ionic conductivity of 6.5 mS cm^(-1)is fabricated with the aid of polytetrafluoroethylene(PTFE)binder and the reinforced cellulose mesh.Moreover,a simple solid electrolyte interphase(SEI)is constructed on the surface of lithium metal to enhance anodic stability.Benefiting from the joint efforts of these merits,the modified ASSLBs with a high cell-level energy density of 311 Wh kg^(-1) show an excellent cyclic stability.The assembled all-solid-state Li_(2) S/Li pouch cell can operate even under the severe conditions of bending and cutting,demonstrating the enormous potential of the sulfide electrolyte membrane for ASSLBs application.

Construction of Ultrathin Layered MXene-TiN Heterostructure Enabling Favorable Catalytic Ability for High-Areal-Capacity Lithium-Sulfur Batteries

Catalysis has been regarded as an effective strategy to mitigate sluggish reaction kinetics and serious shuttle effect of Li-S batteries.Herein,a spherical structure consists of ultrathin layered Ti_(3)C_(2)T_(x)-TiN heterostructures(MX-TiN)through in-situ nitridation method is reported.Through controllable nitridation,highly conductive TiN layer grew on the surface and close coupled with interior MXene to form unique 2D heterostructures.The ultrathin heterostructure with only several nanometers in thickness enables outstanding ability to shorten electrons diffusion distance during electrochemical reactions and enlarge active surface with abundant adsorptive and catalytic sites.Moreover,the(001)surface of TiN is dominated by metallic Ti-3d states,which ensures fast transmitting electrons from high conductive MX-TiN matrix and thus guarantees efficient catalytic performance.Calculations and experiments demonstrate that polysulfides are strongly immobilized on MX-TiN,meanwhile the bidirectional reaction kinetics are catalytically enhanced by reducing the conversion barrier between liquid LiPSs and solid Li_(2)S_(2)/Li_(2)S.As a result,the S/MX-TiN cathode achieves excellent long-term cyclability with extremely low-capacity fading rate of 0.022%over 1000 cycles and remarkable areal capacity of 8.27 mAh cm^(−2) at high sulfur loading and lean electrolytes.