MPCVD设备样品台温控系统的设计

由于传统MPCVD设备样品台温度控制需要使用手动调节样品台距等离子源的距离,且调节精度差,为此设计一种样品台温控系统,同时设计了样品台温控系统硬件控制器。该控制器以STM32F407单片机为核心,步进电机、丝杠、金属波纹管为执行机构,通过控制样品台在腔体内距等离子源的距离,实现温度控制。并提出一种将改进鲸鱼算法(WOA)与神经网络PID控制算法结合的控制方法,实现PID参数的自适应调整。仿真和实验结果表明:相对于传统PID算法,使用该温控系统进行温度控制时,超调量更小,控制精度更高,控制效果有很大提升。

高稳定性圆柱形MPCVD设备的设计与金刚石单晶生长的研究

圆柱腔MPCVD设备结构简单,具有等离子体能量密度高、无电极污染等优点,但是使用过程中稳定性较差,火球容易变换位置。文章使用有限元仿真方法分析了传统圆柱形谐振腔的微波电场分布,通过改变谐振腔形状和尺寸,优化传统圆柱形谐振腔的微波电场分布,减弱了谐振腔石英下方次强场的电场强度,且沉积台上方的电场形状呈现椭球形状,有效地增加了沉积区域,改善电场强度的均匀性。文章中设计的高稳定性圆柱腔MPCVD,无色金刚石单晶沉积实验获得了11μm/h的高品质单晶金刚石生长,Raman散射光谱显示沉积的金刚石1332cm^(-1)附近本征峰半峰宽度为4.2cm^(-1),金刚石的晶体质量良好,表明优化后的MPCVD设备有效地提升了传统圆柱形谐振腔的稳定性和等离子体的能量密度。

Geochemistry and depositional environment of fuchsite quartzites from Sargur Group,western Dharwar Craton,India

Meso-Neoarchean fuchsite quartzites are present in different stratigraphic positions of Dharwar Craton including the oldest(~3.3 Ga)Sargur Group of western Dharwar Craton.The present study deals with the petro-graphic and geochemical characteristics of the fuchsite quartzites from the Ghattihosahalli belt to evaluate their genesis,depositional setting and the enigma involved in the ancient sedimentation history.Their major mineral assemblages include quartz,fuchsite,and feldspars along with accessory kyanite and rutile.The geochemical com-positions are characterized by high SiO_(2),Al_(2)O_(3),low MgO,CaO,strongly enriched Cr(1326–6899 ppm),Ba(1165–3653 ppm),Sr(46–210 ppm),V(107–868 ppm)and Zn(11–158 ppm)contents compared to the upper continental crust(UCC).The UCC normalized rare earth element(REE)patterns are characterized by depleted light REE[(La/Sm)UCC=0.33–0.95]compared to heavy REE[(Gd/Yb)_(UCC)=0.42–1.65]with conspicuous positive Eu-anomalies(Eu/Eu^(*)=1.35–18.27)characteristic of hydrothermal solutions evidenced through the interlayered barites.The overall major and trace element systematics reflect a combined mafic-felsic provenance and suggest their deposition at a passive continental margin environ-ment.The comprehensivefield,petrographic,and geo-chemical studies indicate that these quartzites are infiltrated by Cr-richfluids released during high-grade metamorphism of associated ultramafic rocks.The Sargur and the subse-quent Dharwar orogeny amalgamated diverse lithounits from different tectonic settings,possibly leading to the release of Cr-richfluids and the formation of fuchsite quartzite during or after the orogeny.Thesefindings sug-gest a pre-existing stable crust prior to the Sargur Group and the link between orogenic events and various mineral deposits in the Dharwar Craton.

Simulation of deuterium pellet ablation and deposition in the EAST tokamak with HPI2 code

Pellet injection is a primary method for fueling the plasma in magnetic confinement devices.For that goal the knowledges of pellet ablation and deposition profiles are critical.In the present study,the pellet fueling code HPI2 was used to predict the ablation and deposition profiles of deuterium pellets injected into a typical H-mode discharge on the EAST tokamak.Pellet ablation and deposition profiles were evaluated for various pellet injection locations,with the aim at optimizing the pellet injection to obtain a deep fueling depth.In this study,we investigate the effect of the injection angle on the deposition depth of the pellet at different velocities and sizes.The ablation and deposition of the injected pellet are mainly studied at each injection position for three different injection angles:0°,45°,and 60°.The pellet injection on the high field side(HFS)can achieve a more ideal deposition depth than on the low field side(LFS).Among these angles,horizontal injection on the middle plane is relatively better on either the HFS or the LFS.When the injection location is 0.468 m below the middle plane on the HFS or 0.40 m above the middle plane of the LFS,it can achieve a similar deposition depth to the one of its corresponding side.When the pre-cooling effect is taken into account,the deposition depth is predicted to increase only slightly when the pellet is launched from the HFS.The findings of this study will serve as a reference for the update of pellet injection systems for the EAST tokamak.

New insights into the deposition of natural gas hydrate on pipeline surfaces:A molecular dynamics simulation study

Natural gas hydrate(NGH)can cause pipeline blockages during the transportation of oil and gas under high pressures and low temperatures.Reducing hydrate adhesion on pipelines is viewed as an efficient way to prevent NGH blockages.Previous studies suggested the water film can greatly increase hydrate adhesion in gas-dominant system.Herein,by performing the molecular dynamics simulations,we find in water-dominant system,the water film plays different roles in hydrate deposition on Fe and its corrosion surfaces.Specifically,due to the strong affinity of water on Fe surface,the deposited hydrate cannot convert the adsorbed water into hydrate,thus,a water film exists.As water affinities decrease(Fe>Fe_(2)O_(3)>FeO>Fe_(3)O_(4)),adsorbed water would convert to amorphous hydrate on Fe_(2)O_(3)and form the ordered hydrate on FeO and Fe_(3)O_(4)after hydrate deposition.While absorbed water film converts to amorphous or to hydrate,the adhesion strength of hydrate continuously increases(Fe<Fe_(2)O_(3)<FeO<Fe_(3)O_(4)).This is because the detachment of deposited hydrate prefers to occur at soft region of liquid layer,the process of which becomes harder as liquid layer vanishes.As a result,contrary to gas-dominant system,the water film plays the weakening roles on hydrate adhesion in water-dominant system.Overall,our results can help to better understand the hydrate deposition mechanisms on Fe and its corrosion surfaces and suggest hydrate deposition can be adjusted by changing water affinities on pipeline surfaces.

Effect of phosphorus content on interfacial heat transfer and film deposition behavior during the high-temperature simulation of strip casting

The interfacial wettability and heat transfer behavior are crucial in the strip casting of high phosphorus-containing steel.A hightemperature simulation of strip casting was conducted using the droplet solidification technique with the aims to reveal the effects of phosphorus content on interfacial wettability,deposited film,and interfacial heat transfer behavior.Results showed that when the phosphorus content increased from 0.014wt%to 0.406wt%,the mushy zone enlarged,the complete solidification temperature delayed from1518.3 to 1459.4℃,the final contact angle decreased from 118.4°to 102.8°,indicating improved interfacial contact,and the maximum heat flux increased from 6.9 to 9.2 MW/m2.Increasing the phosphorus content from 0.081wt%to 0.406wt%also accelerated the film deposition rate from 1.57 to 1.73μm per test,resulting in a thickened naturally deposited film with increased thermal resistance that advanced the transition point of heat transfer from the fifth experiment to the third experiment.

Effect of hot isostatic pressure on the microstructure and tensile properties of γ'-strengthened superalloy fabricated through induction-assisted directed energy deposition

The microstructure characteristics and strengthening mechanism of Inconel738LC(IN-738LC) alloy prepared by using induction-assisted directed energy deposition(IDED) were elucidated through the investigation of samples subjected to IDED under 1050℃ preheating with and without hot isostatic pressing(HIP,1190℃,105 MPa,and 3 h).Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ’ phases in interdendritic and dendritic core regions.After HIP,grain morphology changed negligibly,whereas the size of the γ’ phase became increasingly even.After further heat treatment(HT,1070℃,2 h + 845℃,24 h),the γ’ phase in the as-deposited and HIPed samples presented a bimodal size distribution,whereas that in the as-deposited sample showed a size that remained uneven.The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%,respectively,due to the synergistic deformation of bimodal γ’phases,especially large cubic γ’ phases.Finally,the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.

Aerosol deposition technology and its applications in batteries

Aerosol deposition(AD)method is a kind of additive manufacturing technology for fabricating dense films such as metals and ceramics at room temperature.It resolves the challenge of integrating ceramic films onto temperaturesensitive substrates,including metals,glasses,and polymers.It should be emphasized that the AD is a spray coating technology that uses powder without thermal assistance to generate films with high density.Compared to the traditional sputter-based approach,the AD shows several advantages in efficiency,convenience,better interfacial bonding and so on.Therefore,it opens some possibilities to the field of batteries,especially all-solidstate batteries(ASSBs)and draws much attention not only for research but also for large scale applications.The purpose of this work is to provide a critical review on the science and technology of AD as well as its applications in the field of batteries.The process,mechanism and effective parameters of AD,and recent developments in AD applications in the field of batteries will be systematically reviewed so that a trend for AD will be finally provided.

Numerical Simulation of Asphaltene Precipitation and Deposition during Natural Gas and CO_(2) Injection

Asphaltene deposition is a significant problem during gas injection processes,as it can block the porous medium,the wellbore,and the involved facilities,significantly impacting reservoir productivity and ultimate oil recovery.Only a few studies have investigated the numerical modeling of this potential effect in porous media.This study focuses on asphaltene deposition due to natural gas and CO_(2) injection.Predictions of the effect of gas injection on asphaltene deposition behavior have been made using a 3D numerical simulation model.The results indicate that the injection of natural gas exacerbates asphaltene deposition,leading to a significant reduction in permeability near the injection well and throughout the reservoir.This reduction in permeability strongly affects the ability of gas toflow through the reservoir,resulting in an improvement of the displacement front.The displacement effi-ciency of the injection gas process increases by up to 1.40%when gas is injected at 5500 psi,compared to the scenario where the asphaltene model is not considered.CO_(2) injection leads to a miscible process with crude oil,extracting light and intermediate components,which intensifies asphaltene precipitation and increases the viscosity of the remaining crude oil,ultimately reducing the recovery rate.

Thin polymer electrolyte with MXene functional layer for uniform Li^(+) deposition in all-solid-state lithium battery

Solid polymer electrolyte(SPE) shows great potential for all-solid-state batteries because of the inherent safety and flexibility;however, the unfavourable Li+deposition and large thickness hamper its development and application. Herein, a laminar MXene functional layer-thin SPE layer-cathode integration(MXene-PEO-LFP) is designed and fabricated. The MXene functional layer formed by stacking rigid MXene nanosheets imparts higher compressive strength relative to PEO electrolyte layer. And the abundant negatively-charged groups on MXene functional layer effectively repel anions and attract cations to adjust the charge distribution behavior at electrolyte–anode interface. Furthermore,the functional layer with rich lithiophilic groups and outstanding electronic conductivity results in low Li nucleation overpotential and nucleation energy barrier. In consequence, the cell assembled with MXene-PEO-LFP, where the PEO electrolyte layer is only 12 μm, much thinner than most solid electrolytes, exhibits uniform, dendrite-free Li+deposition and excellent cycling stability. High capacity(142.8 mAh g-1), stable operation of 140 cycles(capacity decay per cycle, 0.065%), and low polarization potential(0.5 C) are obtained in this Li|MXene-PEO-LFP cell,which is superior to most PEO-based electrolytes under identical condition. This integrated design may provide a strategy for the large-scale application of thin polymer electrolytes in all-solid-state battery.

Overview of Factors Affecting Dust Deposition on Photovoltaic Cells and Cleaning Methods

Dust deposition on the surface of photovoltaic (PV) cells poses a significant challenge to their efficiency, especially in arid regions characterized by desert and semi-desert conditions. Despite the pronounced impact of dust accumulation, these regions offer optimal solar radiation and minimal cloud cover, making them ideal candidates for widespread PV cell deployment. Various surface cleaning methods exist, each employing distinct approaches. Choosing an appropriate cleaning method requires a comprehensive understanding of the mechanisms involved in both dust deposition on module surfaces and dust adhesion to PV cell surfaces. The mechanisms governing dust deposition and adhesion are complex and multifaceted, influenced by factors such as the nature and properties of the dust particles, environmental climatic conditions, characteristics of protective coatings, and the specific location of the PV installation. These factors exhibit regional variations, necessitating the implementation of diverse cleaning approaches tailored to the unique conditions of each location. The first part of this article explores the factors influencing dust deposition on PV cell surfaces, delving into the intricate interplay of environmental variables and particle characteristics. Subsequently, the second part addresses various cleaning methods, offering an analysis of their respective advantages and disadvantages. By comprehensively examining the factors influencing dust accumulation and evaluating the effectiveness of different cleaning strategies, this article aims to contribute valuable insights to the ongoing efforts to optimize the performance and longevity of photovoltaic systems in diverse geographical contexts.

Prediction Model of Wax Deposition Rate in Waxy Crude Oil Pipelines by Elman Neural Network Based on Improved Reptile Search Algorithm

A hard problem that hinders the movement of waxy crude oil is wax deposition in oil pipelines.To ensure the safe operation of crude oil pipelines,an accurate model must be developed to predict the rate of wax deposition in crude oil pipelines.Aiming at the shortcomings of the ENN prediction model,which easily falls into the local minimum value and weak generalization ability in the implementation process,an optimized ENN prediction model based on the IRSA is proposed.The validity of the new model was confirmed by the accurate prediction of two sets of experimental data on wax deposition in crude oil pipelines.The two groups of crude oil wax deposition rate case prediction results showed that the average absolute percentage errors of IRSA-ENN prediction models is 0.5476% and 0.7831%,respectively.Additionally,it shows a higher prediction accuracy compared to the ENN prediction model.In fact,the new model established by using the IRSA to optimize ENN can optimize the initial weights and thresholds in the prediction process,which can overcome the shortcomings of the ENN prediction model,such as weak generalization ability and tendency to fall into the local minimum value,so that it has the advantages of strong implementation and high prediction accuracy.

Electroacupuncture improves myocardial fibrosis in heart failure rats by attenuating ECM collagen deposition through modulation of TGF-β1/Smads signaling pathway

Background: To explore the effects of electroacupuncture on cardiac function and myocardial fibrosis in rat models of heart failure, and to elucidate the underlying mechanism of electroacupuncture in heart failure treatment. Methods: Healthy male Sprague-Dawley rats were allocated into three groups: Sham group, Model group, and electroacupuncture (Model + EA) group, with each group comprising 8 rats. The model underwent a procedure involving the ligation of the left anterior descending coronary artery to induce a model of heart failure. The Model + EA group was used for 7 consecutive days for electroacupuncture of bilateral Shenmen (HT7) and Tongli (HT5), once a day for 30 min each time. Left ventricular parameters in rats were assessed using a small-animal ultrasound machine to analyze changes in left ventricular end-diastolic volume, left ventricular end-systolic volume, left ventricular ejection fraction, and left ventricular fractional shortening. Serum interleukin-1β (IL-1β), cardiac troponin (cTn), and N-terminal brain natriuretic peptide precursor levels were measured using ELISA. Histopathological changes in rat myocardium were observed through HE staining, while collagen deposition in rat myocardial tissue was assessed using the Masson staining method. Picro sirius red staining, immunohistochemical staining, and RT-qPCR were utilized to distinguish between the various types of collagen deposition. The expression level of TGF-β1 and SMAD2/3/4/7 mRNA in rat myocardial tissues was determined using RT-qPCR. Additionally, western blot analysis was conducted to assess the protein expression levels of TGF-β1, SMAD3/7, and p-SMAD3 in rat myocardial tissues. Results: Compared with the Sham group, the left ventricular ejection fraction and left ventricular fractional shortening values of the Model group were significantly decreased (P < 0.01);the left ventricular end-diastolic volume and left ventricular end-systolic volume values were remarkably increased (P < 0.01);serum N-terminal brain natriuretic peptide precursor content was increased (P < 0.01);serum IL-1β and cTn levels were increased (P < 0.01);myocardial collagen volume fraction were increased (P < 0.01);and those of the expression of TGF-β1 and SMAD2/3/4 mRNA was increased (P < 0.01);the expression of SMAD7 mRNA was decreased (P < 0.01);the protein expression levels of TGF-β1, SMAD3, and p-Smad3 were increased (P < 0.01);the protein expression level of SMAD7 was decreased (P < 0.01) in the Model group. Compared to the Model group, the expression levels of the proteins TGF-β1, SMAD3, and p-Smad3 in myocardial tissue were found to be decreased (P < 0.01), and the expression level of the protein SMAD7 was found to be increased (P < 0.01) in the Model + EA group;the collagen volume fraction and deposition of type Ⅰ /Ⅲ collagen were decreased (P < 0.01) in the Model + EA group. Conclusion: Electroacupuncture alleviates myocardial fibrosis in rats with heart failure, and this effect is likely due to attributed to the modulation of the TGF-β1/Smads signaling pathway, which helps reduce collagen deposition in the extracellular matrix.

Fabrication of Graphene/Cu Composite by Chemical Vapor Deposition and Effects of Graphene Layers on Resultant Electrical Conductivity

Graphene(Gr)has unique properties including high electrical conductivity;Thus,graphene/copper(Gr/Cu)composites have attracted increasing attention to replace traditional Cu for electrical applications. However,the problem of how to control graphene to form desired Gr/Cu composite is not well solved. This paper aims at exploring the best parameters for preparing graphene with different layers on Cu foil by chemical vapor deposition(CVD)method and studying the effects of different layers graphene on Gr/Cu composite’s electrical conductivity. Graphene grown on single-sided and double-sided copper was prepared for Gr/Cu and Gr/Cu/Gr composites. The resultant electrical conductivity of Gr/Cu composites increased with decreasing graphene layers and increasing graphene volume fraction. The Gr/Cu/Gr composite with monolayer graphene owns volume fraction of less than 0.002%,producing the best electrical conductivity up to59.8 ×10^(6)S/m,equivalent to 104.5% IACS and 105.3% pure Cu foil.

MPCVD金刚石薄膜设备冷却水温控系统的设计

为了解决MPCVD设备运行时冷却水手动调节方式存在的弊端,实现冷却水温的自动调节,设计了一种冷却水温度控制系统。该系统以STM32单片机为控制器的核心,步进电机为执行机构,采用BP神经网络PID控制算法。对系统进行了仿真和试验验证,结果表明:该系统能够实现MPCVD设备生产制备金刚石薄膜过程中冷却水温度的自动控制,与传统的PID控制相比,系统采用BP神经网络PID控制算法时超调量更小,控制精度更高,均方根误差和平均绝对误差更小,具有更好的温度控制效果。

MPCVD同质外延单晶金刚石研究进展

微波等离子体化学气相沉积法(Microwave plasma chemical vapor deposition,MPCVD)外延单晶金刚石被认为是制备大尺寸、高质量的单晶金刚石极具前景的技术手段之一。本文首先对MPCVD同质外延单晶金刚石生长机理及最新进展做了简要介绍,然后着重阐述了MPCVD法制备大尺寸、高质量单晶金刚石在籽晶筛选与预处理、基台结构设计及生长工艺探索等方面的工作,并对MPCVD高品质单晶金刚石在力学、热学、光学及电子学等领域的应用进行了介绍,对未来单晶金刚石的应用前景进行了展望。

基于等离子体诊断的MPCVD单晶金刚石生长优化设计

微波等离子体化学气相沉积(Microwave plasma chemical vapor deposition,MPCVD)技术是制备大尺寸、高品质单晶金刚石的理想途径,然而MPCVD单晶金刚石生长过程的复杂性与晶体生长需求的多样性难以对生长过程进行优化设计。针对此问题,本研究提出了一种基于等离子体诊断技术的MPCVD单晶金刚石生长的系统性设计方法,采用等离子体成像和光谱分析对微波等离子体进行量化诊断。并利用自主研发的MPCVD设备,研究了腔室压力-微波功率-等离子体性状-衬底温度间的物理耦合特性和量化关系,得到了不同参数下的等离子体有效长轴尺寸、基团浓度和分布、能量密度等数据,以实验观测数据为基础拟合得到了单晶金刚石生长工艺图谱。根据此工艺图谱,可以通过选择生长温度和所需生长面积来选取工艺参数,且通过实验验证,表明此图谱具有较强的指导意义,预测参数误差小于5%。同时根据该图谱的预测,研究了不同等离子体能量密度下的单晶金刚石生长情况,在较低功率下(2600 W)也得到了较高的能量密度(148.5 W/cm3),含碳前驱体的浓度也高于其他工艺条件,因而获得了较高的生长速率(8.9μm/h)。此套方法体系可以针对不同单晶金刚石生长需求进行有效的等离子体调控和工艺优化。

微波功率和反应腔室压强对MPCVD生长AlN薄膜质量的影响

研究了微波功率和反应腔室压强对微波等离子体化学气相沉积(MPCVD)法生长AlN薄膜质量的影响。采用高温MPCVD法,以N2为氮源,三甲基铝(TMAl)为铝源,在6H-SiC衬底上进行AlN薄膜的外延生长。在不同微波功率和不同反应腔室压强下,外延生长了AlN薄膜样品。生长样品的测试结果表明,在微波功率为4500 W时,样品(002)面X射线摇摆曲线(XRC)半高全宽(FWHM)为217 arcsec。在反应腔室压强为130 Torr(1 Torr=133.3 Pa)时,样品(002)面XRC的FWHM为216 arcsec。该研究将为以后AlN材料的MPCVD生长提供一些参考。

915 MHz高功率MPCVD设备生长8-inch金刚石外延膜

金刚石外延膜具有良好的热学、光学和化学稳定性,同时能够满足大尺寸的制备需求,是红外窗口和散热应用中理想的材料。受限于目前金刚石应用中尺寸较小等问题,制备大尺寸高质量的金刚石一直是人们追求的目标。本文采用自行研制的915 MHz/75 kW的微波等离子体化学气相沉积(MPCVD)设备,研究了不同沉积温度对直径8 inch(1 inch=25.4 mm)的金刚石膜沉积的影响,并通过SEM和Raman对其进行表征分析。结果表明,沉积温度会影响金刚石膜的晶体取向和结晶质量,过低的温度不利于金刚石膜规则地取向生长;而过高的温度会产生sp2石墨相,降低金刚石膜的结晶质量和取向生长。本文最终在1000°C的沉积温度和1.0%的甲烷浓度(甲烷与氢气流量之比为0.01)下成功制备了具有良好的结晶质量和厚度均匀的8 inch(111)取向的金刚石外延膜,该外延膜具有较低的氮杂质含量,生长表面均匀,无生长裂纹产生,晶粒尺寸在3~5 mm。红外透过测试结果表明12μm处的透过率达到了67.8%,8~12μm之间的平均透过率为67.3%。

In-situ deposition of apatite layer to protect Mg-based composite fabricated via laser additive manufacturing

Biodegradable magnesium(Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degradation. In this work, mesoporous bioglass(MBG)with high pore volume(0.59 cc/g) and huge specific surface area(110.78 m^(2)/g) was synthesized using improved sol-gel method, and introduced into Mg-based composite via laser additive manufacturing. Immersion tests showed that the incorporated MBG served as powerful adsorption sites, which promoted the in-situ deposition of apatite by successively adsorbing Ca2+and HPO42-. Such dense apatite film acted as an efficient protection layer and enhanced the corrosion resistance of Mg matrix, which was proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg based composite showed a significantly decreased degradation rate of 0.31 mm/year. Furthermore,MBG also improved the mechanical properties as well as cell behavior. This work highlighted the advantages of MBG in the fabrication of Mg-based implant with enhanced overall performance for orthopedic application.