Effects of particle density on depositing properties of WC-17Co by HVOF process

The in-flight and deposition properties of three types of WC-17 Co powder with different particle densities during a high-velocity oxygen fuel （HVOF） thermal spray process were investigated. Three types of powder exhibited similar velocity upon impact on the substrate surface. The powder with the lower particle density exhibited a higher temperature upon impingement process, resulting in the generation of a higher flattening ratio. Thus, the coating derived from the powder with the lower particle density possessed superior micro-hardness, porosity and surface roughness. However, the coating with the lowest particle density showed the poorest fracture toughness because of the generation of the largest amount of amorphous phase.

Boosting Pseudocapacitive Behavior of Supercapattery Electrodes by Incorporating a Schottky Junction for Ultrahigh Energy Density

Pseudo-capacitive negative electrodes remain a major bottleneck in the development of supercapacitor devices with high energy density because the electric double-layer capacitance of the negative electrodes does not match the pseudocapacitance of the corresponding positive electrodes.In the present study,a strategically improved Ni-Co-Mo sulfide is demonstrated to be a promising candidate for high energy density supercapattery devices due to its sustained pseudocapacitive charge storage mechanism.The pseudocapacitive behavior is enhanced when operating under a high current through the addition of a classical Schottky junction next to the electrode-electrolyte interface using atomic layer deposition.The Schottky junction accelerates and decelerates the diffusion of OH-/K+ions during the charging and discharging processes,respectively,to improve the pseudocapacitive behavior.The resulting pseudocapacitive negative electrodes exhibits a specific capacity of 2,114 C g^(-1)at 2 A g^(-1)matches almost that of the positive electrode’s 2,795 C g^(-1)at 3 A g^(-1).As a result,with the equivalent contribution from the positive and negative electrodes,an energy density of 236.1 Wh kg^(-1)is achieved at a power density of 921.9 W kg^(-1)with a total active mass of 15 mg cm-2.This strategy demonstrates the possibility of producing supercapacitors that adapt well to the supercapattery zone of a Ragone plot and that are equal to batteries in terms of energy density,thus,offering a route for further advances in electrochemical energy storage and conversion processes.

Surface morphology and electrochemical characterization of electrodeposited Ni-Mo nanocomposites as cathodes for hydrogen evolution

In this work, we study the influences of current density on surface morphology and electrochemical characterization of electrodeposited Ni-Mo. The Ni-Mo composite coatings are deposited on pretreated copper substrates by electrolytic deposition. The Ni-Mo solution is taken from nickel sulfate fluid and ammonium heptamolybdate with 10 g/l. The Ni-Mo composite coatings are deposited at a temperature of 303 K with an applied current density of j dep= 10 A/dm2-30 A/dm2.We find that the corrosion resistance is improved by incorporating Mo particles into Ni matrix in 0.6-M Na Cl solution. From the potentiodynamic polarization curve of electrodeposited Ni-Mo it is confirmed that the corrosion resistance decreases with increasing applied current density. The x-ray diffraction（XRD） analyses of Ni-Mo coatings indicate three phases of Mo Ni4, Mo1.24Ni0.76, and Ni3 Mo phases crystallites of nickel and molybdenum. The scanning electronic microscopy（SEM） tests indicate that Ni-Mo coatings present cracks and pores.

Iodine Promoted Ultralow Zn Nucleation Overpotential and Zn-Rich Cathode for Low-Cost, Fast-Production and High-Energy Density Anode-Free Zn-Iodine Batteries

The anode-free design is a promising strategy to increase the energy density of aqueous Zn metal batteries(AZMBs).However,the scarcity of Zn-rich cathodes and the rapid loss of limited Zn greatly hinder their commercial applications.To address these issues,a novel anode-free Zniodine battery(AFZIB)was designed via a simple,low-cost and scalable approach.Iodine plays bifunctional roles in improving the AFZIB overall performance:enabling high-performance Zn-rich cathode and modulating Zn deposition behavior.On the cathode side,the ZnI_(2) serves as Zn-rich cathode material.The graphene/polyvinyl pyrrolidone heterostructure was employed as an efficient host for ZnI_(2) to enhance electron conductivity and suppress the shuttle effect of iodine species.On the anode side,trace I_(3)^(−) additive in the electrolyte creates surface reconstruction on the commercial Cu foil.The in situ formed zincophilic Cu nanocluster allows ultralow-overpotential and uniform Zn deposition and superior reversibility(average coulombic efficiency>99.91% over 7,000 cycles).Based on such a configuration,AFZIB exhibits significantly increased energy density(162 Wh kg^(−1)) and durable cycle stability(63.8% capacity retention after 200 cycles)under practical application conditions.Considering the low cost and simple preparation methods of the electrode materials,this work paves the way for the practical application of AZMBs.

AlO_x prepared by atomic layer deposition for high efficiency-type crystalline silicon solar cell

The influence of atomic layer deposition parameters on the negative charge density in AlOx film is investigated by the corona-charge measurement. Results show that the charge density can reach up to -1.56×10^12 cm%-2 when the thickness of the film is 2.4 nm. The influence of charge density on cell conversion efficiency is further simulated using solar cell analyzing software （PC1D）. With AlOx passivating the rear surface of the silicon, the cell efficiency of 20.66% can be obtained.

Effect of Particle Density on the Aligned Growth of Carbon Nanotubes

Aligned carbon nanotubes (CNTs) were prepared on Ni-coated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550℃.The experimental results show a direct correlation between the alignment of CNTs and the density of the catalyst particles at low temperature.When the particle density is high enough,among CNTs there are strong interactions that can inhibit CNTs from growing randomly.The crowding effect among dense CNTs results in the aligned growth of CNTs at low temperature.

Concealed porphyry delineation based on nonlinear three-dimensional densitydifference inversion: An example in the Beiya mine area, Western Yunnan, China

Intermediate acid-complex rock masses with low-density characteristics are the most important prospecting sign in the Beiya area, of western Yunnan province, and provide a physical basis for good gravity exploration. It is usually difficult to obtaining solutions in connection with actual geological situations due to the ambiguity of the conventional gravity-processing results and lack of deep constraints. Thus, the three-dimensional (3D) inversion technology is considered as the main channel for reducing the number of solutions and improving the vertical resolution at the current stage. The current study starts from a model test and performs nonlinear 3D density-difference inversion called “model likelihood exploration”, which performs 3D inversion imaging and inversion of the known model while considering the topographic effects. The inversion results are highly consistent with those of the known models. Simultaneously, we consider the Beiya gold mine in Yunnan as an example. The nonlinear 3D densitydifference inversion technology, which is restricted by geological information, is explored to obtain the 3D density body structure below 5 km in the mine area, and the 3D structure of the deep and concealed rock masses are obtained using the density constraints of the intermediate-acid-complex rock masses. The results are well consistent with the surface geological masses and drilling-controlled deep geological masses. The model test and examples both show that the 3D density-difference nonlinear inversion technology can reduce inversion ambiguity, improve resolution, optimize the inversion results, and realize “transparency” in deeply concealed rock masses in ore-concentrated areas,which is useful in guiding the deep ore prospecting.

Deposition of Magnetic Carbon Nano Tubes with Chromium Seed

In this work, was obtained metallic decorated, single wall Carbon Nanotubes (SWCNTs) using High Density Chemical Vapor Deposition (HDPCVD) system on chromium thin films on a silicon wafers substrate. The characteristics of this deposition method are capacity of the segregation of metallic nanoparticlesas seed for the SWCNT growing. Use of magnetic particle decorated carbon nanotubes increases the applications in magnetic devices, magnetic memory, and magnetic oriented drug delivery. The CNTs’ spectra show a unique emission band, but due to the presence of the chromium, the spectra obtained in this work showed many bands that are related to the CNTs with different diameters. The CNTs obtained by the HDPCVD system are highly aligned and showed metallic features. Results of this work proved the possibility of obtaining the controlled deposition of aligned single-walled CNTs forest films decorated with chromium and suggested future studies in magnetic devices applications.

Preparation and characterization of jet-electrodeposited nanocrystalline nickel coatings

Nanocrystalline nickel coatings were prepared by both direct current(DC) and pulse current(PC) jet-electrodeposition. The influences of current density and jet velocity on the surface morphology,microstructure and preferred orientation of the coatings obtained were investigated by SEM,TEM and XRD. It is found that the current density strongly affects the microstructure of the nickel coating. An increase of the DC current density results in a slight increase of the grain size and preferred orientation progressive evolution(i.e. from(111) to(200)),whereas an increase of the PC current density leads to a certain decrease of the grain size and preferred orientation change(i.e. from(111) to a strong(220)). Moreover,jet velocity shows no significant effect on the grain size and preferred orientation for the nanocrystalline coatings obtained in both DC and PC within the range of jet velocity studied.

Simulation of distribution of radiation energy density in water balls

The distribution of energy deposition density in radiate region and its surrounding areas from γ-rays wassimulated and analyzed for a water-ball model with Geant4 package(Geant4.7.0,2005) developed by CERN (theCenter of European Research of Nucleus). The results show that the distribution depends strongly on the collimatingcondition of radiation beam. A well-collimated beam would reduce radiation effects on surrounding areas.

Numerical Simulation of Particle Densities Distributions in Atmospheric Pressure Ar/SiH4/H2 Mixed Plasma Under Very High Frequency Excitation

To improve the microcrystalline silicon thin film deposition in quality and to increase its microcrystalline silicon content,we numerically investigated the characteristics of homogeneous discharges in hydrogen diluted silane and argon mixed gases at atmospheric pressure using a two-dimensional fluid model.The model takes into account the primary processes of excitation and ionization,sixteen reactions of radicals with radicals in silane/hydrogen/argon discharges,so this model can adequately describe the discharge plasma.The effects of very high frequency(VHF)excitation on the electron density in such discharges are analyzed.The simulation results show that the electron density does not linearly vary with the excitation frequency within from 90150 MHz.he maximum value occurs at an appropriate excitation frequency i.e.the transition frequency.Increasof the excitation frequency would effectively increase the electron density before the transition frequency,but decreases the density afterwards.is.Moreover,the densities of involved particle species,including H2+,H,Ar*,Ar+,SiH3+,SiH3,SiH3,SiH2are closely interrelated.

基于地质大数据的中国金矿时空分布规律定量研究

在大数据科学成为新的科学范式的背景下,基于地质大数据理念,将传统的定性地质研究方法推向定量研究的高度。文章通过对5300余处金矿产地资料的系统梳理,定量分析了中国省(自治区)、市、县级及Ⅲ级成矿区带金矿成矿密度、成矿强度和各成矿时代金矿的成矿强度问题。研究表明,中国金矿具有明显的时空集中分布趋势。中国金矿空间分布具有区域性集中的明显趋势,以胶东、小秦岭等区域为金矿高密度、高强度成矿区;新疆矿床数量最多;山东省金矿成矿密度最大,成矿强度最强;在地级市统计中,山东烟台市和河北承德市是全国仅有的两处矿产地数量过百的地级市,山东烟台市的金矿无论是矿产地数量、成矿密度,还是成矿强度均居全国首位;在县级行政区统计中,新疆塔城地区托里县金矿矿产地数量最多(52处),安徽铜陵市区金矿成矿密度最大,山东烟台市莱州市的金资源储量最大(2341 t),成矿强度最强(1.35 t/km^(2));在成矿区带统计中,华北陆块北缘东段成矿带(Ⅲ-57)金矿矿产地数量最多(345处),胶东成矿带(Ⅲ-65)金矿成矿密度最大,成矿强度最强。中国金矿时间分布不平衡,具有成矿强度老弱新强、东西南北成矿有别、叠加成矿时间跨度大和新生代金矿资源潜力大的特点;燕山期是中国金矿最重要的成矿时期,成矿强度大,达到10.5个矿区/Ma,金资源储量93 t/Ma。今后中国金矿地质工作的核心依然是加强金矿找矿工作、保障国家金融安全。

燃料包壳表面沉积层对汽化核心密度影响的实验研究

燃料包壳表面沉积层在压水堆常规运行中形成,其对包壳沸腾传热的影响尚不清楚。为了探索包壳表面沉积层对汽化核心密度的影响规律,本文基于常压下的流动沸腾可视化实验台架,以锆-4合金为基板,采用逐层沉积的方法形成不同厚度的SiO_(2)沉积层,通过开展流动沸腾实验对比不同沉积层厚度下的汽化核心密度差异。研究发现,SiO_(2)沉积表面与未沉积表面相比汽化核心密度增大,Koncar模型可较好地预测本实验工况条件下的汽化核心密度。

磁共振IDEAL-IQ序列对非酒精性脂肪性肝病患者肝脏脂肪及铁沉积的诊断价值

目的探讨磁共振IDEAL-IQ序列在非酒精性脂肪性肝病(NAFLD)定量评估中的价值。方法回顾性分析50例临床诊断为NAFLD患者的临床资料,收集年龄、性别、血糖、血脂、尿酸、肝功能等临床及实验室指标。所有患者均接受肝脏磁共振IDEAL-IQ序列扫描并通过测量获得肝脏脂肪分数(PDFF)及铁沉积(R2^(*))值,其中22例患者行肝脏活检并获得肝脏脂肪变性的病理学分级(S0~3级)。采用相关性分析评价PDFF及R2^(*)值与临床、实验室指标的相关性。采用ROC曲线分析PDFF值对不同程度脂肪肝的诊断效能,采用约登指数确定最佳截断值。结果PDFF值与UA、AST、ALT、HDL-C相关(r=0.425,P<0.01;r=0.584,P<0.01;r=0.505,P<0.01;r=-0.296,P<0.05);R2^(*)值与各临床及实验室指标无明显相关性(P>0.05);PDFF评估轻度(S1)、中度(S2)及重度(S3)脂肪肝的AUC值0.972(95%CI:0.905~1.000)、0.902(95%CI:0.765~1.000)、0.825(95%CI:0.528~1.000),P<0.05。结论PDFF值与多项生化指标相关,可作为补充指标定量评价NAFLD;与金标准比较,PDFF值对不同程度脂肪肝展现出良好的诊断效能。

红石岩堰塞坝新堆积体动三轴试验研究

牛栏江上的红石岩堰塞坝新堆积体以石灰岩和白云岩为主,级配和密度离散性较大。同时,已有研究结果表明,红石岩新堆积体具有黏性粗粒土性质,静力参数具有明显的离散性,需开展其岩土料的动力参数研究,以为将其利用改建为水利枢纽提供基础材料数据。采用GDS动三轴仪,对红石岩新堆积体进行了动剪切模量比与阻尼比试验,研究新堆积体动应力应变特性及其影响因素。试验结果表明:随着剪应变的不断增大,新堆积体动剪切模量比不断减小,阻尼比随之增大。新堆积体动力特性受围压影响较为明显,最大动剪切模量随着围压的增大而增大。在相同剪应变条件下,随着围压、干密度、粗颗粒含量的增大,动剪切模量比逐渐增大,阻尼比逐渐减小。另一方面,新堆积体细粒含量较多,颗粒岩性复杂,风化程度差异明显,导致其动力特性具有一定的离散性,与人工筑坝堆石料存在明显差异。

植保无人机烟草大田施药作业参数优选

为探究当前主流植保无人机作业参数对烟草大田不同时期雾滴沉积分布规律的影响,获得雾滴最佳分布效果,以电动多旋翼植保无人机为对象,采用三因素三水平的正交试验对植保无人机飞行高度、飞行速度、施药量3个作业参数优化组合,同时对植保无人机的田间有效喷幅进行检验。结果表明:(1)在烟草伸根期最佳作业参数为飞行高度3 m、飞行速度4 m/s、施药量15 L/hm^(2);(2)在烟草旺长期最佳作业参数为飞行高度3 m、飞行速度5 m/s、施药量15 L/hm^(2);(3)在烟草成熟期最佳作业参数为飞行高度5 m、飞行速度4 m/s、施药量30 L/hm^(2);(4)植保无人机在烟草上的作业喷幅宜设为3~4 m。该试验结果可为后续植保无人机在烟草不同生长期的病虫害防治提供理论基础。

分叉血管边支斑块及继生斑块发生发展趋势的动态模拟

目的考虑血管重构和低密度脂蛋白(low-density lipoproteins,LDL)沉积,探讨分叉血管边支斑块的生长发展趋势,以及因斑块存在而可能引发继生斑块的生长位置。方法建立分叉血管理想化模型,用计算流体力学方法获取边支斑块生长前后壁面切应力分布。在低切应力区域截取7个截面:截面1~3为斑块生成前边支的低切应力区域;截面4、5为斑块上、下游边缘;截面6、7为斑块下游低切应力区域。模拟截面内血管重构和LDL沉积,讨论斑块的生长和发展趋势。结果截面1~3中,截面2产生了明显的负性重构和最高浓度LDL沉积(102.266 mmol/L),说明此处是动脉粥样硬化斑块的起始位置。当斑块产生后,相比于截面4,截面5产生了更明显的血管重构,并造成管腔的狭窄和最高的沉积浓度(110.17 mmol/L),说明斑块有向下游偏心生长的趋势。相比于截面6,截面7(血液流动分离再附着点)产生了更明显的负性重构和最高的沉积浓度(93.851 mmol/L),说明血液流动分离再附着点附近有生成新斑块的可能。结论边支低切应力处产生明显血管重构导致管腔狭窄,并引发LDL的高浓度沉积,形成动脉粥样硬化斑块。其中,分叉血管的外侧壁为动脉粥样硬化斑块生长的起始位置。在斑块生长后斑块有向下游发展的趋势,在流动分离再附着点有形成继生斑块可能。

BDD电极对苯酚降解氧化的试验研究

基于掺硼金刚石(BDD)电极的电化学高级氧化技术是解决难降解有机污染物的有效方法之一。通过热丝化学气相沉积法(Hot Filament CVD,HFCVD)结合动态掺硼工艺,在WC-Co衬底上成功合成了BDD薄膜。在此基础上,利用已制备的WC-Co/BDD电极,以苯酚为目标污染物,探究了不同电流密度、电解质浓度、pH值、苯酚初始浓度对其降解效率的影响。试验结果显示,在电流密度为0.03 A/cm^(2),电解质为1.5 g/L Na_(2)SO_(4)的条件下,无论是在酸性还是碱性环境中,对于质量浓度为1000 mg/L的苯酚溶液,3 h内COD的去除率均达到95%;对于质量浓度低于500 mg/L的苯酚溶液,其COD去除率在相同时间内均接近100%。基于WC-Co/BDD电极的电化学高级氧化技术对苯酚的矿化效果极为显著。

清净分散剂对高密度燃料热氧化安定性的影响

高密度燃料的热氧化安定性对其换热安全性乃至高超音速飞行器的飞行安全至关重要。在燃料中加入清净分散剂可减少热氧化沉积前驱体及沉积物的生成,有助于提高燃料的热氧化安定性。采用快速小型热氧化安定仪研究了不同清净分散剂结构对高密度燃料JP-10热氧化安定性的影响规律,结果表明:在140℃,700 kPa氧气压力下氧化5 h后,当高分子量聚异丁烯基丁二酰亚胺T161(分子量>1000)在JP-10(5 mL)中添加量为100 mg/L时,氧化沉积物的质量减少了56%(94.5 mg),且适当增加分散剂中非极性基团的链长和极性基团的体积,有利于提高JP-10的热氧化安定性;此外,当清净分散剂中极性基团位于分子中部时,对沉积物的抑制效果则更加显著。

基于泥沙异重流稳定性与衰减过程的床面淤积特性研究

泥沙异重流在稳定分层和不断衰减的过程中,伴随着床面淤积特征的变化。通过水槽试验观测异重流“稳定-衰减”过程,结合异重分层流运动理论模型,探究该过程对床面淤积特征的影响。研究结果表明,增加异重流层密度或厚度,形成稳定分层形态的时间明显缩短,同时延长了分层形态的维持时间;计算得到的临界雷诺数与扰动波数虚部相应增加,分层形态稳定性得以增强。异重流的稳定行进对于减小床面淤积具有重要作用,试验中临界雷诺数增加568~820,平均淤积厚度降低了42%~46%。因此,提高异重流稳定性并延缓衰减速率,有助于提高输沙率,可以达到减淤的目的。