Arc erosion behaviors of AgSnO_2 contact materials prepared with different SnO_2 particle sizes

To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallurgy. The microstructure of Ag?4%SnO2 contact materials was characterized, and the relative density, hardness and electrical conductivity were measured. The arc erosion of Ag?4%SnO2 contact materials was tested, the arc duration and mass loss before and after arc erosion were determined, the surface morphologies and compositions of Ag?4%SnO2 contact materials after arc erosion were characterized, and the arc erosion mechanism of AgSnO2 contact materials was discussed. The results show that fine SnO2 particle is beneficial for the improvement of the relative density and hardness, but decreases the electrical conductivity. With the decrease of SnO2 particle size, Ag?4%SnO2contact material presents shorter arc duration, less mass loss, larger erosion area and shallower arc erosion pits.

Characterization of carbon encapsulated Fe-nanoparticles prepared by confined arc plasma

Carbon encapsulated Fe nanoparticles were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area and particle size of the product were characterized via X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectrometry and Brunauer-Emmett-Teller N2 adsorption. The experiment results show that the carbon encapsulated Fe nanoparticles have clear core-shell structure. The core of the particles is body centered cubic Fe, and the shell is disorder carbons. The particles are in spherical or ellipsoidal shapes. The particle size of the nanocapsules ranges from 15 to 40 nm, with the average value of about 30 nm. The particle diameter of the core is 18 nm, the thickness of the shells is 6-8 nm, and the specific surface area is 24 m2/g.

AgNi15 composite particles prepared by ultrasonic arc spray atomization method

Ultrasonic arc spray atomization (UASA) method was used to prepare high-melting-point, immiscible AgNi15 (mass fraction, %) composite particles. Sieving was used to determine the size distribution of the AgNi15 particles. The morphology, rapidly solidified structure and metastable solution expansion of the AgNi15 particles were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The results show that the AgNi15 composite particles are spherical and well-dispersed, and the mass fractions of the particles with diameters <74μm and <55 μm are 99.5% and 98%, respectively. The rapidly solidified structure of the AgNi15 particles consists of spherical nickel-richβ(Ni)-phase particles dispersed throughout a silver-richα(Ag)-phase matrix andα(Ag)-phase nanoparticles dispersed throughout largerβ(Ni)-phase particles. The silver and nickel in the AgNi15 particles form a reciprocally extended metastable solution, and the solid solubility of nickel in the silver matrix at room temperature is in the range of 0.16%?0.36% (mole fraction).

高职院校学生ARCS学习动机模型的探索与实践

本研究利用发放调查问卷、查阅文献和现场访谈等方法,结合ARCS学习动机模型,对现阶段高职院校学生学习现状进行调查研究。结合调查分析结果,借助ARCS学习动机模型进行教学设计并实施教学,调动学生学习的积极性,激发学生的学习动机,提高了学生的学习兴趣和学习能力。

OBE-ARCS导向的化学工程专业学位研究生课程体系建设和课堂教学模式创新

立足学校理工交叉学科特色,化学工程专业以OBE理念为指导,融合产学研用多要素,对专业学位研究生的核心课程体系进行重构;基于ARCS动机模型,创新研究生课程教学模式;协同专业、课程和教材思政,构建一体化育人机制;依托工程实践基地建设,强化理论与工程实践的结合。基于以上举措构建的“四维一体”育人模式将研究生的知识学习、能力培养、意识强化、专业素养提升紧密融合,在培养高质量应用型人才方面取得了显著成效。

基于ARCS模型的翻转课堂教学设计

以“取样定理”为例,提出采用ARCS模型进行翻转课堂教学设计的案例。教学内容设计注重核心价值观的传播,从取样定理形成的历史脉络引出课程思政;运用多种教学手段,提升学生注意力;重视学习内容的关联设计,学生端倚重信息技术应用,及时反馈,提升学生自信度;学习评价注重应用性,提升学习满意度。教学实施结果表明,该教学设计能调动学生的课堂热情,师生满意度高。

ARCS模型视角下高职英语教学资源建设与应用研究

基于ARCS模型视角的高职英语教学资源平台建设和应用,坚持以学习者为中心,以整体化、系统化、标准化、科学化、合作性、共享性、循环性改进为原则,围绕高职学生岗位英语语言技能和职业素养目标,构建高职英语课程教学资源库和教学资源共享平台,完善学习成果考核评价体系,建立质量评估和诊改机制,多举措提升教改能力,促进数字化技术与教学改革实践深度融合与双向赋能。

ARCS动机模型混合学习造纸英语听力App设计与开发

ARCS动机模型是1987年美国学者研究并提出的。信息技术的迅速发展,促使该动机模型在多媒体产品开发、课件设计及教育App领域得以广泛应用,并以此来调动学习者的积极性。依托ARCS动机模型对造纸英语听力App进行设计的主要目的是提升学习者对时间的利用率和学习满意度。基于此,针对用户对造纸英语听力App的学习需求,与现有技术相结合,对当前只限于“速记”“跟读”的学习英语听力App进行创新,提供新的研发思路与方向。

基于ARCS激励模型的老年健步走运动产品设计研究

为提高老年群体参与健步走运动锻炼的积极性,文章从运动激励的角度出发开展老年健步走运动相关的产品设计研究,并利用计算机化行为研究的E-Prime软件,建立SAM情绪测试实验程序。同时,通过对实验所得的情感体验数据进行单因素方差分析,证实引入ARCS模型的健步走运动对于激发老年人积极情绪价值的有效性,并得出ARCS模型激励要素的优先性,基于此提出老年健步走产品设计的策略,以期为老年运动相关产品设计提供新的思路。

基于ARCS模型设计的VR实训课程教学效果分析

以基站运行与维护实训课程为例,基于ARCS模型进行教学设计,关注学生学习感受的四个方面:注意、关联、信心、满足感。同时结合情境认知理论和建构主义理论,通过VR实训课程教学,激发学生学习的兴趣和动机,分析实训课程教学设计,增强课程教学效果。

Experimental Verification of the Physical Model for Droplet-Particles Cleaning in Pulsed Bias Arc Ion Plating

It has been reported that application of pulsed biases in arc ion plating could effectively eliminate droplet particles. The present paper aims at experimental verification of a physical model proposed previously by us which is based on particle charging and repulsion in the pulsed plasma sheath. An orthogonal experiment was designed for this purpose, using the electrical parameters of the pulsed bias for the deposition of TiN films on stainless steel substrates. The effect of these parameters on the amount and the size distribution of the particles were analyzed, and the results provided sufficient evidence for the physical model.

Preparation and particle size characterization of Cu nanoparticles prepared by anodic arc plasma

Copper nanoparticles were successfully prepared in large scale by means of anodic arc discharging plasma method in inert atmosphere. The particle size, specific surface area, crystal structure, and morphology of the samples were characterized by X-ray diffraction （XRD）, BET equation, transmission electron microscopy （TEM）, and the corresponding selected area electron diffraction （SAED）. The experimental results indicate that the crystal structure of the samples is fcc structure the same as that of the bulk materials. The specific surface area is 11 m^2/g, the particle size distribution is 30 to 90 nm, and the average particle size is about 67 nm obtained from TEM and confirmed from XRD and BET results. The nanoparticles with uniform size, high purity, narrow size distribution and spherical shape can be prepared by this convenient and effective method.

Research of precise pulse plasma arc powder welding technology of thin-walled inner hole parts

The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion. The precise pulse plasma arc powder welding method is used for surface damage repairing of inner hole parts in this paper. The working principle and process of the technology are illustrated,and the microstructure and property of repairing layer by precise pulse plasma powder welding and CO2 gas shielded welding are tested and observed by microscope,micro hardness tester and X-ray residual stress tester etc. Results showed that the substrate deformation of thin-walled inner hole parts samples by precise pulse plasma powder welding is relatively small. The repair layer and substrate is metallurgical bonding,the transition zones( including fusion zone and heat affected zone) are relatively narrow and the welding quality is good. It showed that the thin-walled inner hole parts can be repaired by this technology and equipment.

THE EFFECTS OF PULSE BIAS VOLTAGE AND N_2 PARTIAL PRESSURE ON TiAlN FILMS OF ARC ION PLATING (AIP)

Owing to the characteristics of arc ion plating(AIP) technique, the structure and composition of TiAlN films can be tailored by controlling of various parameters such as compositions of target materials, N2 partial pressure, substrate bias and so on. In this study, several titanium aluminum nitride films were deposited on 1Cr11Ni2W2MoV steel for compressor blade of areo-engine under different d.c pulse bias voltage and nitrogen partial pressure. The effects of substrate pulse bias and nitrogen partial pressure on the deposition rate, droplet formation, microstruture and elemental component of the films were investigated.

Wear Properties of Plasma Transferred Arc Fe-based Coatings Reinforced by Spherical WC Particles

Fe-based coatings reinforced by spherical WC particles were produced on the 304 stainless steel by plasma transferred arc(PTA) to enhance the surface wear properties. Three different Fe/WC composite powder mixtures containing 0 wt%, 30 wt%, and 60 wt% of WC were investigated. The microstructure and phase composition of the Fe/WC composite PTA coatings were evaluated systemically by using scanning electron microscope(SEM) and X-ray diffraction(XRD). The wear properties of the three fabricated PTA coatings were investigated on a BRUKER UMT TriboLab. The morphologies of the worn tracks and wear debris were characterized by using SEM and 3 D non-contract profiler. The experimental results reveal that the microhardness on the cross-section and the wear resistance of the fabricated coatings increase dramatically with the increasing adding WC contents. The coating containing 60 wt% of WC possesses excellent wear resistance validated by the lower coefficients of friction(COF), narrower and shallower wear tracks and smaller wear rate. In the pure Fe-based coating, the main wear mechanism is the combination of adhesion and oxidative wear. Adhesive and two-body abrasive wear are predominated in the coating containing 30 wt% of WC, whereas threebody abrasion wear mechanism is predominated in the coating containing 60 wt% of WC.

Thermal behavior of B_4 Cparticles under plasma arc powder surfacing condition

The effect of plasma arc powder surfacing process on the amount of B4C particles in the coating and the thermal behavior of B4C particles in different surfacing stages has been investigated.The results showed that the feeding rate of B4C partiles is the most important factor affecting the amount of B4C particles in the surfacing coating among all the surfacing parameters,and the most part of B4C Particles in the coating is nto the remainders of original solid B4C particles,but the consolidation products of the unmelted liquid B4C globules in the pool.The results also showed that the B4C particles would not be melted in the plasma arc column, their melting process mainly takes place in the anode spot region on the surface of the pool when surfacing current is less than 200A.

Partial and Full Arc Volumetric Modulated Arc Therapy in Lung Cancer Stereotactic Body Radiotherapy with Different Definitions of Internal Target Volume Based on 4D CT

Purpose: To investigate the feasibility of partial arc volumetric modulated arc therapy (VMAT) in lung cancer stereotactic body radiotherapy (SBRT), as well the volumetric and dosimetric effects of different internal target volume (ITV) definitions with 4D CT. Methods: Fourteen patients with primary and metastatic lung cancer underwent SBRT were enrolled. Full and partial arc VMAT plans were generated with four different ITVs: ITVall, ITVMIP, ITVAIP and ITV2phases, representing ITVs generated from all 10 respiratory phases, maximum intensity projection (MIP), average intensity projection (AIP), and 2 extreme respiratory phases. Volumetric and dosimetric differences, as well as MU and delivery time were investigated. Results: Partial arc VMAT irradiated more dose at 2 cm away from planning target volume (PTV) (P = 0.002), however, it achieved better protection on mean lung dose , lung V5, spinal cord, heart and esophagus compared with full arc VMAT. The average MU and delivery time of partial arc VMAT were 240 and 1.6 min less than those of full arc VMAT. There were no significant differences on target coverage and organ at risks (OARs) sparing among four ITVs. The average percent volume differences of ITVMIP, ITVAIP and ITV2phases to ITVall were 8.6%, 13.4%, and 25.2%, respectively. Conclusions: Although partial arc VMAT delivered more dose 2 cm out of PTV, it decreases the dose to lung, spinal cord, and esophagus, as well decreased the total MU and delivery time compared with full arc VMAT without sacrificing target coverage. Partial arc VMAT was feasible and more efficient for lung SBRT.

PARTICLE SIZE AND MICROSTRUCTURE OF Ni NANOPOWDERS PREPARED BY ANODIC ARC PLASMA

Pure Ni nanopowders were successfully prepared by the method of anodic arc disch arged plasma with homemade experimental apparatus. The particle size, mircostruc ture and morphology of the particles by this process were characterized via X-ra y powder diffraction (XRD), transmission electron microscopy (TEM) and the corre sponding selected area electron diffraction (SAED); The specific surface area an d pore parameters were investigated by multi-point full analysis of nitrogen ads orption-desorption isotherms at 77K by Brunauer- Emmett-Teller (BET) surface are a analyzer; The chemical composition were determined by X-ray energy dispersive spectrometry (XEDS) equipped in SEM and element analyze instrument. The experime nt results indicate that the samples by this method with high purity,the crystal structure of the particles is as same as the bulk material, is fcc structure, w ith average particle sizes about 47nm, ranging from 20 to 70nm, and distributed uniformly in spherical chain shapes, the specific surface areavis 14.23m2/g, po re volume of pore is 0.09cm3/g and average pore diameter is 23nm.

Nano-composite Particles Synthesized by a Hydrogen Arc Plasma

Nano-composite particles can be synthesized by a hydrogen arc plasma method, which possesses the advantages of high productivity, controllable size distribution and low electric energy consumption comparing with conventional gas condensation method. With this method, not only the nanoparticles of metals and alloys, but also the nano-composite particles with shell structure can be synthesized. The microstructures, compositions and the formation mechanism of the nano composite particles were studied

TiCN particle reinforce composite coating in-situ synthesized by nitrogen arc cladding technique

An in-situ synthesized TiCN particle reinforce composite coating was fabricated on Q235 steel substrate by nitrogen arc cladding technique, wherein the titanium powder and the graphite powder as original material were intensively mixed by ball-miU and glued with starch binder, then preplaced onto the Q235 steel substrate. The microstructures and interfacial behavior were investigated by scanning electron microscopy. The phase of the coatings was investigated by X-ray diffractometer. The microhardness was tested by microhardness tester. The anti-abrasive pe^Cormance was tested by abrasion machine. The results show that an excellent bonding between the coatings and carbon steel substrate is ensured by the strong metallurgical inteoCace and phases of the coatings are mainly composed of TiCN. The highest microhardness of the coatings reaches 810HV0. 5, which is about 3 times more than that of the Q235 substrate. The anti-abrasive test results indicate that the coating is more anti-abrasive than the Q235 substrate.