Highly mass activity electrocatalysts with ultralow Pt loading on carbon black for hydrogen evolution reaction

Pt-based nanocatalysts offer excellent prospects for various industries.However,the low loading of Pt with excellent performance for efficient and stable nanocatalysts still presents a considerable challenge.In this study,nanocatalysts with ultralow Pt content,excellent performance,and carbon black as support were prepared through in-situ synthesis.These~2-nm particles uniformly and stably dispersed on carbon black because of the strong s-p-d orbital hybridizations between carbon black and Pt,which suppressed the agglomeration of Pt ions.This unique structure is beneficial for the hydrogen evolution reaction.The catalysts exhibited remarkable catalytic activity for hydrogen evolution reaction,exhibiting a potential of 100 mV at 100 mA·cm^(-2),which is comparable to those of commercial Pt/C catalysts.Mass activity(1.61 A/mg)was four times that of a commercial Pt/C catalyst(0.37 A/mg).The ultralow Pt loading(6.84wt%)paves the way for the development of next-generation electrocatalysts.

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.

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.

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.

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 (CM) in ultralow anterior resection (ULAR) or intersphincteric resection. On the assumption that colonic J-pouch anal anastomosis is superior to straight CM 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 vsthe straight CM. 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 after ileostomy 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 for low-lying rectal cancer.

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.

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.

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.

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.

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

基于几何负刚度弹簧结构的超低频有源垂直隔振系统研制

绝对重力仪在地球物理、精密计量、资源勘探等科学研究和工程技术领域有广泛应用.地面振动噪声严重制约绝对重力测量精度.超低频垂直隔振系统可以显著提高绝对重力测量精度.本文研制的超低频有源垂直隔振系统,利用几何负刚度弹簧结构静刚度大、动刚度小的优点,以其替代经典垂直隔振系统中的负载支撑弹簧,通过精密位移检测和伺服反馈控制实现超长的谐振周期.本文详细介绍了该系统的等效物理模型和控制模型,推导了闭环系统的传递函数.所研制的样机闭环周期超过20 s,相关试验验证了系统可以支撑绝对重力仪实现微伽级高精度测量,并且可以在实验室环境下长期稳定工作.该系统的负载安装在结构顶部,适用于激光干涉和原子干涉两种体制的绝对重力仪.

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。

TaSe_(2)/MoS_(2)异质复合涂层的大气摩擦学性能研究

目的制备在大气环境中可以实现超低摩擦的TaSe_(2)/MoS_(2)异质复合涂层,并探讨大气环境中不同湿度对其摩擦学性能的影响。方法结合异质超润滑理论及价键结构稳定性设计思路,采用喷涂法制备TaSe_(2)/MoS_(2)异质复合涂层和MoS2涂层,考察它们在不同湿度的大气环境中的摩擦学性能。利用三维轮廓仪和光学显微镜对比研究2种涂层的磨损情况。通过能谱仪(EDS)和拉曼光谱(Raman)分析不同湿度下2种涂层的磨痕元素分布、润滑膜的氧化程度及差异,进一步研究不同涂层的磨痕及转移膜的化学组成和结构,并对异质复合涂层的摩擦学机理进行探讨。结果制备的TaSe_(2)/MoS_(2)异质复合涂层在相对湿度10%的大气环境中的摩擦因数低至0.013,表现出超低减摩性能。当大气相对湿度从30%逐渐增加到75%时,虽然TaSe_(2)/MoS_(2)异质复合涂层的摩擦因数增加,但是仍低于同等测试条件下MoS2涂层的摩擦因数。同时,TaSe_(2)/MoS_(2)异质复合涂层在不同湿度下的磨损程度也均低于MoS2涂层。通过摩擦界面的元素分布和化学结构分析,进一步证明了摩擦过程中异质复合结构润滑膜的形成及其抗氧化作用。结论在MoS2涂层中引入离子键强度更高的TaSe2可以延缓活性分子对MoS2结构的破坏作用,同时异质摩擦界面的形成有助于降低摩擦因数。

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。

具有超低工作电压的银纳米线阻变器件研究

具有高密度和自适应特性的随机银纳米线网络能够模拟神经元的复杂网络拓扑,在信息存储、选择器和神经形态计算领域中应用广泛。文章采用旋涂工艺在图像化电极衬底上制备了银纳米线器件,研究了不同银纳米线浓度和直径对其电学性能的影响,并最终实现了具有超低工作电压(0.01 V)的神经形态器件。实验结果表明,采用直径为30 nm的银纳米线和浓度为5 wt%的复合溶液所制备的随机网络能够实现可控的大开关比阻变行为。进一步,将该大开关比阻变行为作为器件的初始化过程,实现了银纳米线阻变器件在外加超低脉冲电压刺激作用下的可控突触可塑性行为。最后,通过对单个纳米结点中银纳米细丝的形成与断裂过程进行研究,进一步提出随机银纳米线网络在不同电刺激条件下的工作机理。本工作为新型神经形态器件中随机网络的物理实现和应用提供了新思路。

LISA技术治疗超低出生体质量儿呼吸窘迫综合征28例

目的探讨经鼻持续气道正压通气(nasal continuous positive airway pressure,nCPAP)下经微管气管内注入肺表面活性物质(less invasive surfactant administration,LISA)技术在超低出生体质量儿呼吸窘迫综合征(respiratory distress syndrome,RDS)治疗中的应用与疗效。方法采取前瞻性研究方法,选取潍坊市妇幼保健院新生儿科重症监护病房(neonatalintensive careunit,NICU)2019年7月至2021年4月收治的超低出生体质量儿(58例)为研究对象。应用随机数字表法分为LISA组(28例)和气管插管-注入PS-拔管给予经鼻持续气道正压通气(intubation-surfactant-extubation,INSURE)组(30例)。LISA组采用LISA技术,在nCPAP下,气管内置入微管并注入肺表面活性物质(pulmonarysurfactant,PS);INSURE组采用INSURE技术,拔管后给予nCPAP辅助通气。观察并比较两组病儿给药过程、给药前后呼吸机参数、动脉血气、用氧时间及并发症的发生率。结果LISA组病儿72 h内机械通气率低于INSURE组,差异有统计学意义(21.4%比46.7%,P=0.043);LISA组病儿住院期间无创正压通气时间(404.50 h比483.50 h,P=0.033)及总用氧时间(520.00 h比612.50 h,P=0.040)低于INSURE组;LISA组给药1 h后动脉血氧分压(arterial partialpressureof O_(2),PaO_(2))变化高于INSURE组[(54.29±5.69)mmHg比(52.87±3.27)mmHg,P=0.038],差异有统计学意义;LISA组支气管肺发育不良(25.0%比53.3%,P=0.028)及有血流动力学意义的动脉导管未闭发生率(28.6%比56.7%,P=0.031)低于INSURE组,均差异有统计学意义。结论在超低出生体质量儿RDS治疗中,LISA技术在减少72 h内机械通气率、住院期间用氧时间、近期并发症等方面具有优势,是一种安全有效的治疗超低出生体质量儿RDS的方法。

亚纳米孔石墨烯复合薄膜新型标准漏孔制备及其渗氦性能研究

标准漏孔是氦质谱检漏仪的校准装置,为了提高氦质谱仪检漏灵敏度,必须降低标准漏孔漏率下限。针对目前传统材料加工制作的标准漏孔难以通过改进加工工艺降低漏率下限的情况,利用CVD法制作了一种亚纳米孔石墨烯复合薄膜新型标准漏孔,研究了其渗氦性能和制备工艺稳定性。结果表明:单层石墨烯/PMMA复合薄膜单位面积漏率为4.17×10^(-12)~1.09×10^(-11) Pa·m^(3)/(cm^(2)·s·Pa),通过调节新型材料渗透面积,可制作漏率下限达10-12 Pa·m^(3)/s量级的标准漏孔。