Biodegradable and flexible i-carrageenan based RRAM with ultralow power consumption

Transient memories,which can physically disappear without leaving traceable remains over a period of normal operation,are attracting increasing attention for potential applications in the fields of data security and green electronics.Resistive random access memory(RRAM)is a promising candidate for next-generation memory.In this context,biocompatible l-carrageenan(l-car),extracted from natural seaweed,is introduced for the fabrication of RRAM devices(Ag/l-car/Pt).Taking advantage of the complexation processes between the functional groups(C–O–C,C–O–H,et al.)and Ag metal ions,a lower migration barrier of Ag ions and a high-speed switching(22.2 ns for SET operation/26 ns for RESET operation)were achieved,resulting in an ultralow power consumption of 56 fJ.And the prepared Ag/l-car/Pt RRAM devices also revealed the capacities of multilevel storage and flexibility.In addition,thanks to the hydrophilic groups of l-car molecule,the RRAM devices can be rapidly dissolved in deionized(DI)water within 13 minutes,showing excellent transient characteristics.This work demonstrates that l-car based RRAM devices have great potential for applications in secure storage applications,flexible electronics and transient electronics.

Electrochemically Grown Ultrathin Platinum Nanosheet Electrodes with Ultralow Loadings for Energy-Saving and Industrial-Level Hydrogen Evolution

Nanostructured catalyst-integrated electrodes with remarkably reduced catalyst loadings,high catalyst utilization and facile fabrication are urgently needed to enable cost-effective,green hydrogen production via proton exchange membrane electrolyzer cells(PEMECs).Herein,benefitting from a thin seeding layer,bottom-up grown ultrathin Pt nanosheets(Pt-NSs)were first deposited on thin Ti substrates for PEMECs via a fast,template-and surfactant-free electrochemical growth process at room temperature,showing highly uniform Pt surface coverage with ultralow loadings and vertically well-aligned nanosheet morphologies.Combined with an anode-only Nafion 117 catalyst-coated membrane(CCM),the Pt-NS electrode with an ultralow loading of 0.015 mgPt cm−2 demonstrates superior cell performance to the commercial CCM(3.0 mgPt cm^(−2)),achieving 99.5%catalyst savings and more than 237-fold higher catalyst utilization.The remarkable performance with high catalyst utilization is mainly due to the vertically well-aligned ultrathin nanosheets with good surface coverage exposing abundant active sites for the electrochemical reaction.Overall,this study not only paves a new way for optimizing the catalyst uniformity and surface coverage with ultralow loadings but also provides new insights into nanostructured electrode design and facile fabrication for highly efficient and low-cost PEMECs and other energy storage/conversion devices.

A comprehensive review of ultralow‑weight proppant technology

Proppant plays a critical role in the exploitation of oil and gas,especially in the development of nonconventional oil and gas resources.Proppants are small spheres that have adequate strength to withstand high closure stresses to keep cracks open;therefore,hydrocarbon fows smoothly into the wellbore.However,traditional proppants are prone to settling in hydraulic fracturing operations,which seriously afects the operation efect.To this end,ultralow-weight proppants have been extensively employed in the petroleum industry.One of the widespread forms of ultralow-weight proppant application in the oil and gas industry is related to light density.Ultralow-weight proppants will provide substantial fow paths with a considerably high propped surface area and remarkably reduce fne generation and scaling.This paper presents a comprehensive review of over 50 papers published in the past several decades on ultralow-weight proppants.The purpose of this study is to provide an overview of the current ultralow-weight proppant development status in raw materials,manufacturing process,performance characteristics,hydrophobic and lipophilic capabilities,and feld application to promote the research of new ultralow-weight proppants.Lastly,this study analyzes the current challenges and emphasizes the development direction of fractured proppants.

Cooperative Chloride Hydrogel Electrolytes Enabling Ultralow-Temperature Aqueous Zinc Ion Batteries by the Hofmeister Effect

Aqueous zinc ion batteries have high potential applicability for energy storage due to their reliable safety,environmental friendliness,and low cost.However,the freezing of aqueous electrolytes limits the normal operation of batteries at low temperatures.Herein,a series of high-performance and low-cost chloride hydrogel electrolytes with high concentrations and low freezing points are developed.The electrochemical windows of the chloride hydrogel electrolytes are enlarged by>1 V under cryogenic conditions due to the obvious evolution of hydrogen bonds,which highly facilitates the operation of electrolytes at ultralow temperatures,as evidenced by the low-temperature Raman spectroscopy and linear scanning voltammetry.Based on the Hofmeister effect,the hydrogen-bond network of the cooperative chloride hydrogel electrolyte comprising 3 M ZnCl_(2)and 6 M LiCl can be strongly interrupted,thus exhibiting a sufficient ionic conductivity of 1.14 mS cm;and a low activation energy of 0.21 e V at-50℃.This superior electrolyte endows a polyaniline/Zn battery with a remarkable discharge specific capacity of 96.5 mAh g;at-50℃,while the capacity retention remains~100%after 2000 cycles.These results will broaden the basic understanding of chloride hydrogel electrolytes and provide new insights into the development of ultralow-temperature aqueous batteries.

Changing characteristics of ultralow permeability reservoirs during waterflooding operations

The characteristics of ultralow permeability reservoirs changed after waterflooding. Thin- section analysis and scanning electron microscopy （SEM） of core samples from inspection wells indicated that calcite and barite were formed in ultralow permeability reservoirs during waterflooding operations. Some asphaltene precipitates on the surface of formation rock would influence the reservoir porosity, permeability, wettability, and electrical properties. In this paper, the changes of physical, electrical, and fluid properties of ultralow permeability reservoirs during waterflooding operations were analyzed. This provides important information to improve waterflooding performance in ultralow permeability reservoirs.

Photonic synapses with ultralow energy consumption for artificial visual perception and brain storage

The human visual system,dependent on retinal cells,can be regarded as a complex combination of optical system and nervous system.Artificial retinal system could mimic the sensing and processing function of human eyes.Optically stimulated synaptic devices could serve as the building blocks for artificial retinas and subsequent information transmission system to brain.Herein,photonic synaptic transistors based on polycrystalline MoS_(2),which could simulate human visual perception and brain storage,are presented.Moreover,the photodetection range from visible light to near-infrared light of MoS_(2) multilayer could extend human eyes’vision limitation to near-infrared light.Additionally,the photonic synaptic transistor shows an ultrafast speed within 5μs and ultralow power consumption under optical stimuli about 40 aJ,several orders of magnitude lower than biological synapses(50 ms and 10 fJ).Furthermore,the backgate control could act as emotional modulation of the artificial brain to enhance or suppress memory function,i.e.the intensity of photoresponse.The proposed carrier trapping/detrapping as the main working mechanism is presented for the device.In addition,synaptic functionalities including short synaptic plasticity,long synaptic plasticity and paired-pulse facilitation could be successfully simulated based on the prepared device.Furthermore,the large difference between short synaptic plasticity and long synaptic plasticity reveals the better image pre-processing function of the prepared photonic synapses.The classical Pavlovian conditioning associated with the associative learning is successfully implemented as well.Therefore,the efficient and rich functionalities demonstrate the potential of the MoS_(2) synaptic device that integrates sensing-memory-preprocessing capabilities for realizing artificial neural networks with different emotions that mimic human retina and brain.

Study on laser welded heat-affected zone in new ultralow carbon bainitic steel

800 MPa grade ultralow carbon bainitic （NULCB） steel is the recently developed new generation steel, which was produced by thermo mechanical controlled processing ＆ relaxation-precipitation controlling transformation （TMCP＆RPC） tech- nique. The microstructure and the mechanical properties of the heat-affected zone （HAZ） in NULCB steel under laser welding conditions were investigated by using a Gleeble-1500 thermal simulator. The experimental results indicate that the simplex microstructure in the HAZ is granular bainite that consists of bainite-ferrite （BF） lath and M-A constituent when the cooling time from 800 to 500℃ （t8/5） is 0.3-30 s, and the M-A constituent consists of twinned martensite and residual austenite. As t8/5 increases, the hardness and tensile strength of HAZ decreases, but they are higher than that of the base metal, indicating the absence of softened zone after laser welding. The impact toughness of HAZ increases at first and then decreases when t8/5 increases. The impact energy of HAZ is much higher than that of the base metal when t8/5 is between 3 and 15 s. It indicates that excellent low temperature toughness can be obtained under appropriate laser welding conditions.

Ultralow Specific on-Resistance Trench MOSFET with a U-Shaped Extended Gate

An ultralow specific on-resistance （Ron,sp） trench metal-oxide-semiconductor field effect transistor （MOSFET） with an improved off-state breakdown voltage （BV） is proposed. It features a U-shaped gate around the drift region and an oxide trench inserted in the drift region （UG MOSFET）. In the on-state, the U-shaped gate induces a high density electron accumulation layer along its sidewall, which provides a low-resistance current path from the source to the drain, realizing an ultralow Ron,sp. The value of Ron,sp is almost independent of the drift doping concentration, and thus the UG MOSFET breaks through the contradiction relationship between R p and the off-state BV. Moreover, the oxide trench folds the drift region, enabling the UG MOSFET to support a high BV with a shortened cell pitch. The UG MOSFET achieves an Ron,sp of 2 mΩ·cm^2 and an improved BV of 216 V, superior to the best existing state-of-the-art transistors at the same BV level

Heck Reactions with Ultralow Concentration of Transition Metals under Microwave Irradiation

The Heck coupling reactions of aryl halides and olefins were performed under the microwave assistance. Interestingly, the ultralow concentration of transition metals (in ppb) coming from the reactants could catalyze the Heck coupling reactions under microwave irradiation, without addition of any catalysts, ligands and phase-transfer agents. The influences of bases, solvents and temperature were discussed, and the reaction rate was enhanced largely in the mixed solvents of NMP and water due to the solubility of base in water.

Colonic J-pouch anal anastomosis after ultralow anterior resection with upper sphincter excision for low-lying rectal cancer

AIM: There is some evidence of functional superiority of colonic J-pouch over straight coloanal anastomosis (CAA)in ultralow anterior resection (ULAR) or intersphincteric resection. On the assumption that colonic J-pouch anal anastomosis is superior to straight CAA in ULAR with upper sphincter excision (USE: excision of the upper part of the internal sphincter) for low-lying rectal cancer, we compare functional outcome of colonic J-pouch vs the straight CAA.METHODS: Fifty patients of one hundred and thirty-three rectal cancer patients in whom lower margin of the tumors were located between 3 and 5 cm from the anal verge received ULAR including USE from September 1998 to January 2002. Patients were randomized for reconstruction using either a straight (n = 26) or a colonic J-pouch anastomosis (n = 24) with a temporary diverting-loop ileostomy. All patients were followed-up prospectively by a standardized questionnaire [Fecal Inco-ntinence Severity Index (FISI) scores and Fecal Incontinence Quality of Life (FIQL) scales].RESULTS: We found that, compared to straight anastomosis patients, the frequency of defecation was significantly lower in J-pouch anastomosis patients for 10 mo afterileostomy takedown. The FISI scores and FIQL scales were significantly better in J-pouch patients than in straight patients at both 3 and 12 mo after ileostomy takedown.Furthermore, we found that FISI scores highly correlated with FIQL scales.CONCLUSION: This study indicates that colonic J-pouch anal anastomosis decreases the severity of fecal incontinence and improves the quality of life for 10 mo after ileostomy takedown in patients undergoing ULAR with USE forlow-lying rectal cancer.

Ultralow friction PTFE/PEEK heterolayer:A new solid lubrication approach toward simplicity

Tribological applications of polytetrafluoroethylene(PTFE)are often limited by technological complexity to overcome its poor wear resistance.Here,a PTFE/polyetheretherketone(PEEK)heterolayer(HL)was proposed and evaluated as a new solid lubrication solution.Pin-on-disk tribometry found the lowest friction coefficient(μ)of 0.031 and ultralow wear for the PEEK/HL under typical conditions.The friction coefficient of the HL surpasses those of the state-of-the-art polymeric coatings/composites by at least 200%,and approaches that of highly lubricated interfaces.Mechanistic investigations revealed multi-length physical and chemical heterogeneity of the HL that best facilitates a tribofilm with high subsurface stability and surface instability.The technological simplicity and robustness of the HL’s high lubricity make it a promising new type of solid lubrication toward greater reliability and longevity.

New thermoelectric semiconductors Pb_(5)Sb_(12+x)Bi_(6-x)Se_(32) with ultralow thermal conductivity

Five new semiconductors Pb_(5)Sb_(12+x)Bi_(6-x)Se_(32)(x=0,1,2,3,and 4)have been synthesized for the first time,which adopt pavonite-type structure and crystallize in monoclinic C2/m space group.The crystal structure is composed of two different types of polyhedral slabs.Slab-I is a galena-like structure motif that forms with[MSe_(6)](M=Pb,Sb,and Bi)octahedra and slab-Ⅱcontains one octahedral[MSe_(6)]block and paired squared pyramids[MSe_(5)].Pb_(5)Sb_(12+x)Bi_(6-x)Se_(32)exhibits n-type semiconductor behaviors and the remarkable Seebeck coefficient from-64.1μV K^(-1)for x=0 sample to-242μV K^(-1)forx=4 sample at 300 K.Moreover,the Pb_(5)Sb_(12)Bi_(6)Se_(32)has the highest carrier concentration of 1.35×10^(20)cm^(-3)in pavonite-type materials.The complex compositions,mixed occupancies of the cations,and quasi-two-dimensional structure lead to the low lattice thermal conduc-tivity(κ_(lat))less than 0.48 W m^(-1)K^(-1)from 300 to 723 K,at which Pb_(5)Sb_(16)Bi_(2)Se_(32)especially shows the ultralow value of 0.25 W m^(-1)K^(-1).As a result,the thermoelectric figure of merit,ZT~0.34 at 723 K,is obtained for the intrinsic Pb_(5)Sb_(12)Bi_(6)Se_(32).

Charge-balanced codoping enables exceeding doping limit and ultralow thermal conductivity

Materials with low thermal conductivity are applied extensively in energy management,and breaking the amorphous limits of thermal conductivity to solids has attracted widespread attention from scientists.Doping is a common strategy for achieving low thermal conductivity that can offer abundant scattering centers in which heavier dopants always result in lower phonon group velocities and lower thermal conductivities.However,the amount of equivalent heavyatom single dopant available is limited.Unfortunately,nonequivalent heavy dopants have finite solubility because of charge imbalance.Here,we propose a charge balance strategy for SnS by substituting Sn2+with Ag^(+)and heavy Bi^(3+),improving the doping limit of Ag from 2%to 3%.Ag and Bi codoping increases the point defect concentration and introduces abundant boundaries simultaneously,scattering the phonons at both the atomic scale and nanoscale.The thermal conductivity of Ag0.03Bi0.03Sn0.94S decreased to 0.535 W·m^(−1)·K^(−1)at room temperature and 0.388 W·m^(−1)·K^(−1)at 275°C,which is below the amorphous limit of 0.450 W·m^(−1)·K^(−1)for SnS.This strategy offers a simple way to enhance the doping limit and achieve ultralow thermal conductivity in solids below the amorphous limit without precise structural modification.

Long-lasting chemiluminescence by aggregation-induced emission surfactant with ultralow critical micelle concentration

The development of green and simple chemiluminescence(CL)systems with intensive and long-lasting emission is highly desirable in lighting and extension of their applications.In this study,it is found that the involvement of aggregation-induced emission(AIE)surfactant could greatly enhance the CL of luminol–H2O2–Co2+system.The inserted hydrophobic tetraphenylethylene fluorophore in AIE is able to increase the hydrophobicity of alkyl chain and decrease the critical micelle concentration(CMC)of surfactant.The synergistic effect of micelle-improved enrichment and CL resonance energy transfer endows luminol–H2O2–Co2+system intensive and long-lasting emission under neutral pH conditions(pH 7.4).The visible emission is still observed even after 60 min.Our study has opened a new avenue for exploring green and simple effective CL systems through AIE surfactant with unltralow CMC toward various applications in lighting,optical sensing,and photocatalysis,etc.

Ultralow friction of ion-containing water nanodroplets

We reveal the ultralow friction or superlubricity of water nanodroplets containing cations and anions on graphene substrates at high ion concentration by molecular dynamics simulations.When the ion concentration is higher than 7 wt.%and the nanodroplet diameter is larger than 10 nm,the friction coefficients of water nanodroplets are lower than 10−2,and can decrease to the order of 10−3 with increasing the ion concentration further.At a certain ion concentration,the optimal nanodroplet diameter of 17–20 nm exists at which the friction coefficient is the lowest.The ultralow friction behaviors of water nanodroplets containing cations and anions are mainly attributed to the opposite variation trends between the interfacial adhesion energy and surface energy of water nanodroplet with ion concentration,and the interfacial hydrophobicity sustained by high ion concentration.These results unveil the essential role of ions in achieving the superlubricity of water nanodroplets.

MXene-enhanced environmentally stable organohydrogel ionic diode toward harvesting ultralow-frequency mechanical energy and moisture energy

With the accelerating advancement of distributed sensors and portable electronic devices in the era of big data,harvesting energy from the surrounding environment to power electrical devices has become increasingly attractive.However,most mechanical energy harvesters often require high operating frequencies to function properly.Moreover,for practical applications,the survivability of devices in harsh operating environments is a vital issuewhich must be addressed.Besides,the single-stimulus responsiveness limits their further applications in complex external environments.Here,a pressure and moisture dual-responsive ionic diode consisting of two organohydrogels with opposite charges as an energy harvester is proposed.The organohydrogel ionic diode utilizes the migration of cations and anions to form the depletion zone and followed by an enhancement of the built-in potential along the depletion zone as a result of mechanical stress or humidity,converting ultralow-frequency mechanical energy or moisture energy into electrical energy.Meanwhile,this mechanism is further confirmed by the finite element analysis.With the increased rectification ratio due to the introduction of MXene,the ionic diode exhibits a relatively large output current(∼10.10μA cm^(−2))and power density(∼0.10μW cm^(−2))at a mechanical pressure of 0.01 Hz,outperforming most currently available mechanical energy harvesters.More impressively,the incorporation of ethylene glycol provides the hydrogel ionic diode with excellent temperature tolerance and long-term environmental stability.The organohydrogel ionic diode can also be applied as a moisture-driven power generator and self-powered humidity sensor.This study presents promising prospects for the efficient collection of renewable and sustainable energy and the practical application of hydrogel-based energy harvesters in extreme environments.

Colossal permittivity and ultralow dielectric loss in Nb-doped SrTiO_(3) ceramics

Defect engineering has been applied to prepare materials with modifiable dielectric properties.SrTiNbxO3(x=0,0.003,0.006,0.009,0.012)ceramics were synthesized using the traditional solid-state reaction method and sintered in a reducing atmosphere.All samples show excellent dielectric properties with giant permittivity(>3.5×10^(4))and low dielectric loss(<0.01).SrTiNb0.003O3 ceramic exhibits a colossal permittivity of 4.6×10^(4)and an ultralow dielectric loss of 0.005(1 kHz,room temperature)as well as great temperature stability in the range of(−60)–160℃.The mechanism of the presented colossal permittivity(CP)properties is investigated by conducting X-ray photoelectron spectroscopy(XPS)and analyzing activation energies.The results indicate that the introduction of Nb5+and the reducing sintering atmosphere together generated the formation of Ti^(3+)and V_(O)^(**).These defects further form Ti-V_(O)^(**)-Ti'_(Ti)defect dipoles,contributing to the coexisting giant permittivity and low dielectric loss in Nb-doped SrTiO_(3)(STN)ceramics.

基于CALPUFF模型的山东省独立焦化行业大气污染物分析与预测

基于已建立的2018年山东省高分辨率独立焦化行业排放清单,结合焦化行业制定的相关政策,本研究设置了基准情景(BAU-2018、BAU-2025、BAU-2035)和减排优化情景(ERO-2025、ERO-2035),使用CALPUFF模型模拟了各情景下山东省独立焦化行业SO_(2)、NO_x、PM_(10)及PM_(2.5)的污染情况及各污染物的减排潜力.研究结果表明,在BAU-2018情景中,山东省各市SO_(2)、NO_x、PM_(10)和PM_(2.5)的年均贡献比例的范围分别为0.06%~0.84%、0.01%~0.63%、0.04%~0.19%和0.07%~0.21%;在各阶段中,ERO-2025情景较于现状(BAU-2018)的各污染物排放与贡献浓度降低幅度最大;最优情景ERO-2035较于BAU-2018,SO_(2)、NO_x、PM_(10)、PM_(2.5)和CO_(2)的排放量分别为减少了60.12%、78.24%、75.07%、74.20%和37.47%,SO_(2)、NO_x、PM_(10)和PM_(2.5)年均贡献浓度降幅分别为60.74%、78.56%、75.00%和74.53%.全面执行超低排放标准对污染物减排具有显著效果,同时显示出巨大的污染物与CO_(2)的协同减排潜力.

TiO_(2)直接还原制备超低氧钛

提出在MgCl_(2)−KCl−YCl_(3)熔盐中,通过熔盐电解产生Mg直接还原TiO_(2)制备低氧钛。绘制Mg−Ti−O三元相图和电位−氧势(φ−pO^(2)−)图,表明镁还原TiO_(2)制备低氧钛是可行的。在MgCl_(2)−YCl_(3)和MgCl_(2)−YCl_(3)−KCl熔盐中,不同温度和施加电压条件下,开展熔盐电解−镁热还原TiO_(2)实验研究,结果表明:借助YOCl沉淀及CO_(x)同步生成,将还原和脱氧产物O^(2)−快速脱除,在1073~1173 K、施加电压2.5~3.1 V的条件下,通过电化学还原可以将TiO_(2)还原为高氧钛(Ti6O)。在温度为1173 K的MgCl_(2)−YCl_(3)熔盐中,开展不同施加电压下的高氧钛电化学脱氧实验。此外,还观察到有可能将高氧钛的氧含量可从1200×10^(−6)降至100×10^(−6)以下。

独立测距通道超低空无线电引信

针对多通道功能复用脉冲或脉冲多普勒(PD)引信测距误差较大,严重制约引信超低空性能的问题,提出基于独立测距通道的超低空无线电引信。该超低空无线电引信由目标探测通道和独立测距通道组成,其中目标探测通道采用PD体制,独立测距通道采用线性调频连续波(LFMCW)体制。仿真分析结果表明,基于独立测距通道的超低空无线电引信安全距离仅需0.7 m,在目标探测通道距离波门调整过程中引信目标探测区得到最大程度的保留,同时具备3 m高度飞行目标的近距探测能力。