Microstructure and depositional mechanism of Ni-P coatings with nano-ceria particles by pulse electrodeposition

Nano-CeO2 （RE） particles were co-deposited into Ni-P binary composite coatings by applying pulse current （PC） under ultrasonic （U） field. Morphology, chemical content and crystal microstructure were characterized by environmental scanning electron microscopy （E-SEM） with energy dispersive X-ray analysis （EDXA）, XRD diffractometry and transmission electron microscopy （TEM）. Experimental results show that Ni-P coating reinforced with 15g/L nano-CeO2, in amorphous state and with compact structure, can be improved in the microhardness from HV0.2580 to HV0.2780 by annealing at 600 °C for 2 h. The highest content of codeposited Ce and deposition rate can reach 2.3% and 68 μm/h, respectively. Furthermore, the effect of RE adsorption and pulse overpotential on depositional mechanism was investigated. n-CeO2 particles or Ce4＋ ions with strong adsorption capacity acted as the catalytic nucleus to improve densification effectively. During annealing at 600 °C for 2 h, n-CeO2 particles will uniformly adsorb on crystal grain to preferentially pad and heal up gaps of cracking Ni boundaries, promoting dispersion strengthening with refiner-grained structure.

Spatial variation in grain-size population of surface sediments from northern Bering Sea and western Arctic Ocean: Implications for provenance and depositional mechanisms

In general,sediments in nature comprise populations of various diameters.Accurate information regarding the sources and depositional mechanisms of the populations can be obtained through their temporal and spatial comparisons.In this study,the grain size distribution of surface sediments from the Bering Sea and western Arctic Ocean were fitted and partitioned into populations using a log-normal distribution function.The spatial variations in the populations indicate differences in their sources and deposition mechanisms.The sediments on most of the Bering Sea Shelf originated from the Yukon River,and were transported westward by waves and currents.However,the presence of a coarser population outside Anadyr Bay was the result of Anadyr River transport.Additionally,a northward transport trend of fine suspended particles was observed on the west side of the Bering Sea Shelf.The sediments in Hope Valley in the south Chukchi Sea also originated from the Yukon River.The coarser population on the central Chukchi Sea Shelf originated from coast of Alaska to the east,not the Yukon River,and was transported by sea ice and bottom brine water.The populations of sediments from the Chukchi Basin and the base of the Chukchi Sea Slope are the result of sea ice and eddy action.Surface sediments from the western high Arctic Ocean predominantly comprised five populations,and two unique populations with mode diameters of 50–90μm and 200–400μm,respectively,were ubiquitous in the glacial and interglacial sediments.It was difficult to distinguish whether these two populations originated from sea ice or icebergs.Therefore,caution should be exercised when using either the>63μm or>250μm fractions in sediments as a proxy index for iceberg and ice sheet variation in the high Arctic Ocean.

Chemical Vapor Deposition Mechanism of Copper Films on Silicon Substrates

A versatile metal-organic chemical vapor deposition （MOCVD） system was designed and constructed. Copper films were deposited on silicon （100） substrates by chemical vapor deposition （CVD） using Cu（hfac）2 as a precursor. The growth of Cu nucleus on silicon substrates by H2 reduction of Cu（hfac）2 was studied by atomic force microscopy and scanning electron microscopy. The growth mode of Cu nucleus is initially Volmer-Weber mode （island）, and then transforms to Stranski-Rastanov mode （layer-by-layer plus island）. The mechanism of Cu nucleation on silicon （100） substrates was further investigated by X-ray photoelectron spectroscopy. From Cu2p, O1s, F1s, Si2p patterns, the observed C=O, OH and CF3/CF2 should belong to Cu（hfac） formed by the thermal dissociation of Cu（hfac）2. H2 reacts with hfac on the surface, producing OH. With its accumulation, OH reacts with hfac, forming HO-hfac, and desorbs, meanwhile, the copper oxide is reduced, and thus the redox reaction between Cu（hafc）2 and H2 occurs.

On Mineralize-halo-forming Mechanism of Sareke Glutenite-type Copper Deposit in Xinjiang

1 Introduction Sareke glutenite-type copper deposit is located in the Sarekebayi basin,a sub-basin of southwest margin of the Tuoyun Mesozoic hinterland basin in the northwestern part of the Tarim Basin.The Tuoyun Mesozoic hinterland

Ore-Forming Mechanism of the Asikaerte Granitic Pegmagtite Beryllium Deposit in Xinjiang, China

Objective Granitic pegmatite has great significance for studying magmatic-hydrothermal evolution, which is the main formation mechanism of rare metal deposits. Conventionally, granitic pegmatite rare metal deposits are regarded as crystallization from H20-saturated granite magma that formed in the late fractional crystallization of granitic magma. However, some scholars recently believed that the liquid immiscibility of granitic magma promoted the formation of pegmatite deposits. The Asikaerte beryllium deposit in Xinjiang, China, bearing metallogenic belts from lower granite belt to upper pegmatite belt, could benefit us to understand the formation of pegmatite through analyzing fluid and melt inclusions data.

Conduction Properties and Scattering Mechanisms in F-doped Textured Transparent Conducting SnO_2 Films Deposited by APCVD

Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2/(V/s) have been prepared by atmosphere pressure chemical vapour deposition (APCVD). These polycrystalline films possess a variable preferred orientation, the polycrystallite sizes and orientations vary with substrate temperature. The substrate temperature and fluorine flow rate dependence of conductivity, Hall mobility and carrier conentration fOr the resultingfilms have been obtained. The temperature dependence of the mobiity and carrier concentrationhave been measured over a temperature range 16～400 K. A systematically theoretical analysis on scattering mechanisms for the highly conductive SnO2 films has been given. Both theoretical analysis and experimental results indicate that for these degenerate, polycrystalline SnO2 ：F films in the low temperature range (below 100 K), ionized impurity scattering is main scattering mechanism. However, when the temperature is higher than 100 K, the lattice vibration scattering becomes dominant. The grain boundary scattering makes a small contribution to limit the mobility of the films.

The Geochemical Characteristics and Metallogenic Mechanism of the Daliangzi Pb-Zn Deposit in Sichuan Province

1 Introduction Daliangzi large-sized Pb-Zn deposit,located in the Western Margin of Yangtze Plate,is typical Pb-Zn deposit in the sichuan-yunnan-guizhou polymetallic metallogenic belt.Ore bodies are hosted in Sinian

Formation Mechanism of the Tongyu Gold Deposit,Shaanxi——A Discussion of a Model for the Formation of Syntectonic Gold Deposits

The formation of the Tongyu gold deposit, controlled by regional polyphase deformation-metamorphism.is closely related to the regional composite antiform-shear slip fracture zone. Late-stage reworking of theTaihua Group accounts for the enrichment of ore substances. It is a typical syntectonic gold deposit. The formation and evolution of the deposit involved four stages: (Ⅰ) the state of preparation of ore sub-stances, in which primary source beds originated: (Ⅱ) the stage of remobilization of ore substances, in whichregional progressive metamorphism and migmatization and thermodynamic-chemical differentiation led toremobilization of gold and its initial local concentration: (Ⅲ) the stage of gold deposit formation, in which re-gional folding produced concordant and cross shear-slip fractures and under the dynamic action gold was sepa-rated and migrated in a certain direction and concentrated to form a gold deposit: (Ⅳ) the stage ofsuperpositon, reworking and exposure of orebodies, in which the block uplifted and the deposit againunderwent reworking through faulting and mechanical differentiation.Thermodynamic mineralization played adominant role in the formation of the deposit.

The Occurrence Mechanism of Gold in Pyrite from the Qiucun Gold Deposit in Fujian Province, China

1 Introduction Precipitation and enrichment of gold is an important subject in the study of gold deposits.As the most common sulphide in gold deposits,pyrite is not only a good indicator of the evolution of mineralizing fluids,but also the important gold-bearing mineral.In this paper,

Rational design of carbon skeleton interfaces for highly reversible sodium metal battery anodes

Sodium metal batteries(SMBs)have attracted increasing attention over time due to their abundance of sodium resources and low cost.However,the widespread application of SMBs as a viable technology remains a great challenge,such as uneven metallic deposition and dendrite formation during cycling.Carbon skeletons as sodiophilic hosts can alleviate the dendrite formation during the plating/stripping.For the carbon skeleton,how to rationalize the design sodiophilic interfaces between the sodium metal and carbon species remains key to developing desirable Na anodes.Herein,we fabricated four kinds of structural features for carbon skeletons using conventional calcination and flash Joule heating.The roles of conductivity,defects,oxygen content,and the distribution of graphite for the deposition of metallic sodium were discussed in detail.Based on interface engineering,the J1600 electrode,which has abundant Na-C species on its surface,showed the highest sodiophilic.There are uniform and rich F-Na species distributed in the inner solid electrolyte interface layer.This study investigated the different Na-deposition behavior in carbon hosts with distinct graphitic arrangements to pave the way for designing and optimizing advanced electrode materials.

Improving Hydration Resistance of MgO-CaO Clinkers by Depositing MgO Coating

By carbothermal reduction of Mg O with black carbon as reduction agent at a high temperature,Mg O was deposited on the surface of Mg O- Ca O clinker（ as coating） to improve the clinker ＇s hydration resistance. In the paper,effect of deposition temperature and holding time on the hydration resistance of the treated Mg O-Ca O,the deposition mechanism and Mg O coating kinetics were investigated with hydration resistance test,X-ray diffractometry（ XRD） and scanning electronic microscope（ SEM）. Results showed Mg O coating grew in a2D mode on the surface of Mg O- Ca O particles; the Mg O coating improved the hydration resistance of the coated Mg O- Ca O clinker,and the coated clinker would become stronger when coated at higher deposition temperature and longer holding time. The measurements also found that Mg O deposition process varied with the deposition temperature： it was mainly a chemical-controlled process at temperatures between 1 400- 1 500 ℃,with an apparent activation energy（ AAE） of 97. 8kJ·mol^（-1）; it would change into a diffusion-controlled process when the temperature rising to 1 500- 1 600 ℃,with apparent activation energy of 19. 2kJ·mol^（-1）.

Effects of Carbon Nanotubes by Electrophoretic Deposition on Interlaminar Properties of Two Dimensional Carbon/carbon Composites

Carbon nanotubes（CNTs） were deposited uniformly on carbon cloth by electrophoretic deposition（EPD）. Thereafter, CNT-doped clothes were stacked and densified by pyrocarbon via chemical vapor infiltration to fabricate two-dimensional（2 D） carbon/carbon（C/C） composites. Effects of EPD CNTs on interlaminar shear performance and mode Ⅱ interlaminar fracture toughness（GⅡc） of 2 D C/C composites were investigated. Results showed that EPD CNTs were uniformly covered on carbon fibers, acting as a porous coating. Such a CNT coating can obviously enhance the interlaminar shear strength and GⅡc of 2 D C/C composites. With increaing EPD CNTs, the interlaminar shear strength and GⅡc of 2 D C/C composites increase greatly and then decrease, both of which run up to their maximum values, i e, 13.6 MPa and 436.0 J·m-2, when the content of EPD CNTs is 0.54 wt%, 2.27 and 1.45 times of the baseline. Such improvements in interlaminar performance of 2 D C/C composites are mainly beneficial from their increased cohesion of interlaminar matrix, which is caused not only by the direct reinforcing effect of EPD CNT network but also by the capacity of EPD CNTs to refine pyrocarbon matrix and induce multilayered microstructures that greatly increase the crack propagation resistance through ＂crack-blocking and-deflecting mechanisms＂.

Probe into deposition mechanism of double pulse electrodepositing Ni-W-P matrix composite coatings containing CeO_2 and SiO_2 nano-particles

Ni-W-P matrix composite coatings reinforced by CeO2 and SiO2 nano-particles were prepared on common carbon steel surface by double pulse electrodeposition and the deposition mechanism was discussed.The results showed that the composite coatings with amorphous structure were obtained as-deposited.The initial growth behavior had alternatives and the nucleation was inhomogeneous because of obvious composition fluctuation.With the pulse deposition time increasing,some pearlite microstructures of the substrate were covered by some deposits and the composition fluctuation disappeared.Forward pulse currents promoted to form a great number of atomic beams composed of Ni,W and P atoms or CeO2 and SiO2 nano-particles as the core,which inhabited the growth of atomic beams.Reverse pulse currents eliminated concentration polarization and dissolved some surface boss of atomic beams.The solution of W and P atoms within Ni grains and embedding of CeO2 and SiO2 nano-particles within Ni-W-P matrix metal made atomic arrangement disordered.Finally,the atomic beams grew to amorphous small particles.

Effect of Deposition Temperature on Dynamics and Mechanism of Deposition for Si-B-C Ceramic from BCl_3/SiCH_3Cl_3/H_2 Precursor

The deposition rate, phase, chemical composition and microstructure of deposits were determined from 950 to 1100 ℃. With increasing temperature, the deposition rate increases, and the morphology changes from smooth to coarse, meanwhile, the concentration of silicon increases while that of boron decreases. The deposition process is controlled by chemical reactions, and the activation energy is 271 kJ/mol. At relatively lower temperature （below 1000 ℃）, the deposition process is dominated by formation of BaC. While at higher temperature （above 1000 ℃）, it is governed by formation of SiC. BaC and SiC disperse uniformly in the Si-B-C co-deposition system and form a dense network structure.

Flume Tank Simulation on Depositional Mechanism and Controlling Factors of Beach-Bar Reservoirs

The beach-bar reservoir has become an important exploration target in China, but its depositional mechanism and controlling factors have not yet been fully modeled. They have become an inhibitory factor for the exploration and development of beach-bar reservoirs. The depositional mechanism of beach-bars and their controlling factors have been studied by means of a flume experiment including seven runs under controlled boundary conditions which were the water level（Run 1, Run 2 and Run 3）, wave parameters（Run 1, Run 4 and Run 5） and initial slope（Run 1, Run 6 and Run 7）. The experiment revealed that the development of beach-bar was controlled by water level, wave parameters and initial slope. The deposited locations of distal bar and nearshore bar were controlled by the water level. Two beach-bars were migrated downward when the water level falls（Run 1, Run 2 and Run 3）. The width and thickness of distal bar and nearshore bar were controlled by wave parameters, especially the wave height. They increased with the scale of wave. But, the maximum thickness is limited by the water level（Run 1, Run 4 and Run 5）. The distance between distal bar and nearshore bar was controlled by the initial slope. It became shorter with the steeper slope. Distal bar and nearshore bar changed into one bar when the initial gradient was greater than 1/20（Run 1, Run 6 and Run 7）. The results suggest formative mechanism and controlling factors related to beach-bars.

Deposition kinetics and mechanism of pyrocarbon for electromagnetic-coupling chemical vapor infiltration process

Although the electromagnetic-coupling chemical vapor infiltration(E-CVI)has been proven of a highefficiency technique for producing carbon fiber reinforced pyrocarbon(Py C)matrix(C/C)composites,a deep understanding of the deposition kinetics and mechanism of Py C matrix is still lack.In this work,a deposition model with uniform electric field but gradient magnetic field was set up by using unidirectional carbon fiber bundles as the substrates to investigate the deposition kinetics and mechanism.Meanwhile,the polarizability,and the chemical adsorption and dehydrogenation barriers of hydrocarbon were simulated based on the density functional theory(DFT)and the Climb-image nudged elastic band method,respectively.The E-CVI process exhibited extremely high Py C deposition rates of 8.7,11.5,16.5 and 22.7 nm/s at 700,750,800 and 850℃,respectively,together with a significantly low apparent activation energy of 57.9 k J/mol within the first 5 min.The Py C deposited at different temperatures with different time shows a smooth laminar structure with low coherent length and graphitization degree.The theoretical calculation and simulation results indicated that the electrons existing on the carbon fibers and the accelerated motion of radicals with preferred orientation forced by the derived magnetic field have reduced the energy barrier for the deposition process,thereby resulting in low apparent activation energy and high Py C deposition rate.The results of this work may shed a light on how to better direct the preparation of C/C composites by E-CVI process with high quality and efficiency.

The Influence of Deposition Parameters on the Microstructure and Deposition Mechanism of Low-temperature Isotropic Pyrocarbon on a Bed of Fluidized Particles

To investigate the microstructure and deposition mechanism of low-temperature isotropic pyrocarbon(LTIC),chemical vapour deposition was conducted in a steady-state fluidized bed using different propane concentrations and deposition temperatures.The microstructure of LTIC obtained at different deposition conditions was characterized using scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that LTIC is composed of both globular-like and laminar structures.Increasing the deposition temperature is propitious for decreasing the nucleation barrier-forming pyrocarbon in vapour,causing the quantity of spherical particles with a smaller diameter to increase and the texture of the outer layer around carbon blacks inside the spherical particles to decrease gradually.Increasing the propane concentration also made the globular-like fracture morphology more obvious and caused the laminar structure to gradually disappear.Pyrocarbon formation is dominated by a surficial growth mechanism at lower propane concentrations,while gaseous nucleation mechanism is more dominant at higher propane concentrations.

Deep-reinforcement-learning-based UAV autonomous navigation and collision avoidance in unknown environments

In some military application scenarios,Unmanned Aerial Vehicles(UAVs)need to perform missions with the assistance of on-board cameras when radar is not available and communication is interrupted,which brings challenges for UAV autonomous navigation and collision avoidance.In this paper,an improved deep-reinforcement-learning algorithm,Deep Q-Network with a Faster R-CNN model and a Data Deposit Mechanism(FRDDM-DQN),is proposed.A Faster R-CNN model(FR)is introduced and optimized to obtain the ability to extract obstacle information from images,and a new replay memory Data Deposit Mechanism(DDM)is designed to train an agent with a better performance.During training,a two-part training approach is used to reduce the time spent on training as well as retraining when the scenario changes.In order to verify the performance of the proposed method,a series of experiments,including training experiments,test experiments,and typical episodes experiments,is conducted in a 3D simulation environment.Experimental results show that the agent trained by the proposed FRDDM-DQN has the ability to navigate autonomously and avoid collisions,and performs better compared to the FRDQN,FR-DDQN,FR-Dueling DQN,YOLO-based YDDM-DQN,and original FR outputbased FR-ODQN.