Cementite Decomposition in Spherical Graphite Iron by Electropulsing

The influence of electropulsing on cementite decomposition in the spherical graphite iron has been studied. The results indicated that the cementite was decomposed in a short time by high current density electropulsing. With increasing electropulsing time, the in situ nucleation of graphite in cementite was accompanied with the quick decomposition of cementite. The dislocation accumulation adjacent to the cementite and the quick diffusion of carbon atom by electropulsing were main reasons for the quick decomposition of cementite. The in situ nucleation of graphite in the cementite resulted from the dislocation climbing crossing the cementite lamellae.

Investigation on MoS_2 and Graphite Coatings and Their Effects on the Tribological Properties of the Radial Spherical Plain Bearings

With constant enlargement of the application areas of the spherical plain bearings,higher quality lubrication of the bearings is required.To solve the lubricating problems of spherical plain bearings under high temperature,high vacuum,high speed,heavy loads and strong oxidation conditions,it is urgent for us to develop more excellent self-lubricating technologies.In this paper,the bonded solid lubricant coatings,which use inorganic phosphate as the binder,the mixture of MoS2 and graphite with two different weight proportions as the solid lubricant,are prepared by spraying under three different spray gun pressures.The bonding strength tests on the coatings show that the best spraying pressure is 0.2 MPa and the better mixing proportion of MoS2 to Graphite is 3：1.Then for the radial spherical plain bearings with steel/steel friction pair,after the coatings are made on the inner ring outer surfaces,the friction coefficient,the wear loss and the friction temperature of the bearings under four oscillating frequencies are investigated by a self-made tribo-tester.The test results,SEM of the worn morphologies and EDS of worn areas show that tribological properties of the bearing are obviously improved by the bonded solid lubricant coatings.When sprayed under the spray gun pressure of 0.2 MPa,the bearings have better anti-friction and anti-wear properties than those sprayed under 0.1 MPa and 0.3 MPa.Further as proved from the XPS analysis,between the coating with 3：1 mixing ratio of MoS2 to Graphite and the coating with 1：1 ratio,the former has less oxidation occurred on the surface and therefore has better tribological characteristics than the latter.This paper provides a reference to developing a new product of the radial spherical plain bearings with high bonding strength,oxidation resistance and abrasion resistance.

Spectroscopic Analysis of Spherical Graphite from Xinjiang Altai

1 Introduction In recent years,the study has found that spherical graphite has a high charge and discharge capacity and electrochemical stability,is the ideal lithium battery anodematerial and important ultra-high capacitor material,with a high cost performance(Chuan et al,2012).Spherical

Influence of graphite particle size and its shape on performance of carbon composite bipolar plate

Bipolar plates for proton exchange membrane fuel cell (PEMFC) where polymer is used as binder and graphite is used as electric filler were prepared by means of compression molding technology. Study on the effects of graphite particle size and shape on the bipolar plate performance, such as electrical conductivity, strength, etc. showed that with decrease of graphite particle size, bulk electrical conductivity and thermometric conductivity decreased, but that flexural strength was enhanced. After spherical graphite occurrence in flake-like form, the flexural strength of the bipolar plate was enhanced, electrical conductivity increased but thermal conductivity decreased in direction paralleling pressure direction, and both electrical conductivity and thermometric conductivity reduced in direction perpendicular to pressure direction.

球墨铸铁电极气体开关特性研究

高功率容量的气体开关是国内外大型脉冲功率装置的首选,但因气体放电随机性导致的自击穿电压抖动一直以来是脉冲功率装置的瓶颈问题。电极是影响气体开关稳定性和寿命的关键,开关设计总要面临低抖动和长寿命之间的取舍,提出一种兼顾低抖动、长寿命特性的球墨铸铁气体开关。基于对球墨铸铁材料的特性分析,提出球墨均布于电极有利于提高气体开关击穿稳定性的机制,且球状石墨均布于整个电极体内,相比表面结构,具有长寿命的原生优势。设计开展了单级开关稳定性测试实验,结果表明球墨铸铁电极可将传统电极结构3%~4%的重频自击穿抖动有效降低至2.5%。最终利用低抖动球墨电极,设计了5级1 MV等自击穿概率型全密封气体开关,开关抖动进一步降低至2%以下。在测试电压范围960~980 kV,放电电流约9 kA,无维护条件下开展了开关30万脉冲寿命考核,自击穿抖动维持在2%以下,最优达1.7%。开关导通前沿小于5 ns,传输效率大于90%。此结果展现了球墨铸铁作为气体开关电极的应用潜力。

天然鳞片石墨球形尾料制备柔性电热膜

随着球形石墨在锂离子电池负极材料的应用,天然鳞片石墨球化过程中产生了大量的球形尾料,其利用率及附加值较低。本文将球形石墨(SG8)、球形尾料与羧基化纳米纤维素按不同比例混合,制备了6种柔性电热膜。通过调控球形石墨和球形尾料添加量、电压等参数,研究电热膜的电阻、电阻率和升温速率的演变规律。研究表明,在10V电压下,球形尾料含量为15%的加热膜电阻率为8.57mΩ/mm,达到发热最高温度为59.3℃,前30s的升温速率为0.50℃/s,水洗后球形尾料含量为15%的加热膜电阻率为9.30mΩ/mm,达到发热最高温度为58.6℃,前30s的升温速率为0.46℃/s,表明球形尾料电热膜水洗后仍具备良好的柔性和发热性能,证明了利用天然石墨球形尾料可制备柔性电热膜。相比于球形石墨,球形尾料具有更好的电热性能,为天然石墨球形尾料的高质化利用提供了解决途径。

高速列车球墨铸铁齿轮箱铸造工艺模拟及实验

利用计算机数值模拟技术对高速列车球墨铸铁齿轮箱铸件的铸造充型过程和温度场分布进行了数值模拟。在综合考虑了球墨铸铁凝固过程中的石墨化膨胀、孕育处理、球化剂的衰退以及铸型刚度影响的基础上,设计了合理的无冒口铸件浇注工艺。通过现场浇注实验,生产的齿轮箱强度、塑性和低温冲击性能均满足验收标准,并且-40℃低温冲击性能达到-20℃低温冲击标准要求的数值,满足动车组齿轮箱国产化的要求。

沥青炭包覆对球形石墨电化学性能的影响

这是一篇矿物材料领域的论文。通过沥青包覆球形晶质石墨和炭化处理制备出锂离子电池负极材料,系统探究了沥青软化点对沥青炭化包覆球形晶质石墨负极材料结构和电化学性能的影响。结果表明,沥青炭化包覆后在石墨表面形成了一层无定形炭,改善了球形晶质石墨的表面形貌,但未改变其晶体结构;高沥青软化点包覆后的复合材料具有更好的电化学性能和循环稳定性,在温度为280℃条件下,经过30次循环充放电后容量没有明显的衰减,容量保持率为85.07%,比未处理的试样提高了4.74%。

High-thermally conductive AlN-based microwave attenuating composite ceramics with spherical graphite as attenuating agent

High-thermally conductive AlN-based microwave attenuating composite ceramics with spherical graphite(SG) as the attenuating agent were fabricated through hot-pressing sintering. The SG maintains its three-dimensional(3D) morphology within the sintered bodies, which considerably impedes the sintering of the composites to some extent but slightly influences on the growth of AlN grains. The addition of SG reduces the strength of the composites, but provides a moderate toughening effect at the optimal addition amount(3.8 MPa·m^(1/2) at 4 wt% SG). Benefiting from the low anisotropy, high thermal conductivity, and the 3D morphology of SG, the composites exhibit a relatively higher thermal conductivity(76.82 W·m^(–1)·K^(–1) at 10 wt% SG) compared with composites added with non-spherical attenuating agent. The dielectric constant and loss(8.2–12.4 GHz) increase remarkably as the amount of SG added increases up to 8 wt%, revealing that the incorporation of SG improves the dielectric property of the composite. The composite with 7 wt% SG exhibits the best absorption performance with a minimum reflection loss of –13.9 dB at 12.4 GHz and an effective absorbing bandwidth of 0.87 GHz. The excellent overall properties of the SG/AlN microwave attenuating composites render them as a promising material for various applications. Moreover, SG has a great potential as an attenuating agent for microwave attenuating composites due to its strong attenuation upon integration, high thermal conductivity, and low anisotropy.

Influence of Electropulsing Pretreatment on Solid-State Graphitization of Spherical Graphite Iron

The solid-state graphitization process of spherical graphite iron after electropulsing pretreatment was ob- served in-situ by using a high-temperature confocal scanning laser microscope （HTCSLM）. The influence of electro- pulsing pretreatment on the decomposition of cementite and the formation of graphite during the solid-state graphiti- zation was studied. The result indicates that the electropulsing pretreatment can accelerate the decomposition of ce mentite, and make more neonatal graphite in small size be formed near the cementite. The neonatal graphite nucle ates and grows chiefly at the temperature range of 800 to 850 ℃, and the average growth rate of neonatal graphite is 0. 034 μm2/s during the heating process. For the spherical graphite iron after normal and electropulsing pretreat- ment, the decomposition rate of cementite during the heating process is 0.16 and 0.24 μm2/s, respectively. Analy- sis shows that the electropulsing pretreatment promotes the dislocation accumulation near the cementite, conse- quently, the decomposition of cementite and the formation of neonatal graphite is accelerated during the solid-state graphitization.

Selection of raw materials and control of trace elements for production of high-quality SG iron

During the production of SG iron, the selection of raw materials and control of chemical composition are most important. From the very early days of SG iron production, the effects of trace elements on graphite form and matrix structure have been studied, and the allowable concentration limits for their detrimental influence has been decreased year by year, during the last fifty years. This paper has reviewed some of the suggested SG iron trace elements in the literature and in several Chinese foundries. It was found that for most SG iron castings, rare earth elements are still required to neutralize the harmful effects of trace elements and improve SG iron quality. It also found that the use of high purity and ultra-high purity base iron melts enabled integrated, safety-critical and complicated SG iron castings of varying thickness, and heavy-section, to be produced successfully. These SG iron castings have surprisingly good structures, and their mechanical and dynamic properties are vastly superior to those specified in current international SG iron standards. Further study is required on the effects of using high purity and ultra-high purity base melts on the structure and properties of SG iron.

多源石墨固废制备电热板材配方试验研究

为了提高石墨固废利用率,本文以石墨开采废石为细骨料,添加球形石墨尾料以及不同质量分数的废石石粉进行电热板材配方试验,探究了石墨开采废石取代量、石粉掺量对电热板材性能的影响。结果表明:在100%(质量分数)使用石墨开采废石作为细骨料时,养护28 d的水泥板材抗折强度及抗压强度分别达到11.09 MPa和50.90 MPa,虽然略低于使用标准砂的水泥板材的强度指标,但是仍可满足相关要求,说明石墨开采废石可以作为细骨料使用;在废石石粉掺量为7%(质量分数)时,电热板材的抗折强度和抗压强度最高分别达到6.21 MPa和33.00 MPa,虽然强度有所降低,但是仍可满足低强度板材的要求;在球形石墨尾料掺量为9%(质量分数)时,电热板材体积电阻率为1.94Ω·m,发热温度为71℃,具有良好的电热效果。

SGformer:Boosting transformers for indoor lighting estimation from a single image

Estimating lighting from standard images can effectively circumvent the need for resourceintensive high-dynamic-range(HDR)lighting acquisition.However,this task is often ill-posed and challenging,particularly for indoor scenes,due to the intricacy and ambiguity inherent in various indoor illumination sources.We propose an innovative transformer-based method called SGformer for lighting estimation through modeling spherical Gaussian(SG)distributions—a compact yet expressive lighting representation.Diverging from previous approaches,we explore underlying local and global dependencies in lighting features,which are crucial for reliable lighting estimation.Additionally,we investigate the structural relationships spanning various resolutions of SG distributions,ranging from sparse to dense,aiming to enhance structural consistency and curtail potential stochastic noise stemming from independent SG component regressions.By harnessing the synergy of local–global lighting representation learning and incorporating consistency constraints from various SG resolutions,the proposed method yields more accurate lighting estimates,allowing for more realistic lighting effects in object relighting and composition.Our code and model implementing our work can be found at https://github.com/junhong-jennifer-zhao/SGformer.

改性球形微晶石墨用作锂离子电池负极材料的研究

为了改善用作锂离子电池负极材料的球形微晶石墨的电化学性能,采用液相浸渍工艺在石墨颗粒表面上包覆一层树脂炭.结果表明:经包覆后,石墨颗粒表面更为光滑,其首次充放电循环效率从包覆前的81.0%提高到了92.7%,且首次可逆比容量也有所增加.

我国石墨资源开发利用现状及供需分析

石墨是我国重要的战略性矿产资源,由于其优异的性能在钢铁、冶金、航空航天、信息技术等行业广泛应用。对我国石墨资源、消费现状、进出口贸易等进行了分析,结果表明:我国鳞片石墨资源量稳中有升,隐晶质石墨资源量相比2012年稳中有升,石墨资源勘查工作和资源开发需求趋于合理。全球和我国石墨产量近10年相对平稳,现有资源满足需求。我国石墨传统应用下降,新兴产业领域应用增长较快。进出口方面无论初级加工品(如鳞片石墨)还是高级加工品(如球形石墨)加工技术提高很快,价格跟外国发达国家同类产品差距近几年大幅缩小,一些高端产品如阴极电池世界市场占有率已达到第一。石墨价格过高过低都不利于石墨相关产业的发展,对石墨进行有序开发,保障石墨价格处于合理区间十分重要。

核心形状对石墨球化的影响

研究了低碳球铁中球状石墨的内部结构及核心形状 ,探讨了核心形状对石墨球化的影响规律。研究表明 ,核心的存在是石墨形核长大的基础 ,而核心形状对石墨的最终形状起着至关重要的影响 ;球形或接近球形的石墨核心长大后大多都能保持原来的球状 ,形状不规则的核心 ,则很难长大成为圆整的球状石墨。但是 ,铁水中如果只有气泡或球形核心存在 ,而没有足够的粘度、压力、过冷度和较高的表面能以及吸附等其它充分条件的配合 ,这些核心仍然很难长大成为球状石墨。也就是说 ,凡是有利于铁水中形成球形核心 ,并有利于这种核心在各个方向均匀生长的因素 ,都可看作是促进石墨球化的因素 ,反之亦然。研究还表明 ,表面活性元素的球化和反球化作用不是绝对的 ,在一定条件下它们可能会相互转化。传统理论中认定的球化和反球化元素 ,实际上并非在各种不同条件下都能促进或破坏球化 ,因此 。

微氧化处理对球形石墨结构及电化学行为的影响

研究了微氧化处理对球形石墨的晶体结构、表面形貌和电化学行为的影响.采用XRD、Raman光谱和SEM等手段分析了样品的结构和形貌,并采用恒电流充放电测试、粉末微电极技术和慢速扫描循环伏安法(SSCV)研究了微氧化前后石墨负极的电化学行为.结果表明,微氧化后石墨颗粒中的结构缺陷增多,近表面区域的无序度增大,面内平均晶粒尺寸La减小,且菱形相含量降低,石墨呈不规则的鳞片状,部分层面的边缘有卷曲与刻蚀现象.微氧化后石墨负极的第三次脱锂容量从345.5 mAh/g增加至381.4 mAh/g,且其循环性能得到有效改善.同时,微氧化后锂离子较容易从石墨中脱出,脱锂过程中一阶Li-GICs(lithium-graphite intercalation compounds,简称Li-GICs)向二阶Li-GICs的阶转变可在较低的电位下发生.

基于MAGMAsoft的夹钳铸件工艺及性能分析

分析了制动器夹钳的结构特点及工艺要求。通过MAGMAsoft软件对铸造工艺、充型、凝固过程进行了模拟，优化了浇注系统，使铸件缩孔、缩松等缺陷减少．球化石墨的大小和数量均匀。这能提高铸件质量，取得明显的经济效益。

球状石墨的粉压成型及以其为原料的金刚石生长

本文研究了球状石墨的粉压成型特性。在国产SPD6×1 200型六面顶高温高压设备上,分别以鳞片石墨和球状石墨(均为400目)为碳源,以铁基粉末触媒为原料,在压力5.5 GPa,温度1 400℃左右,合成时间300 s的条件下合成出了优质金刚石单晶。通过球状石墨与鳞片状石墨生长的金刚石的对比,说明了球状石墨—铁基触媒体系生长金刚石的特点。结果表明球状石墨也可以用来合成优质磨料级金刚石单晶,但合成温度要比用片状石墨时高100℃左右,合成的金刚石粒度较鳞片石墨合成的金刚石粒度稍粗。

四川攀枝花晶质石墨矿电性特征及找矿评价

【研究目的】石墨具有高的电子导电性,电性呈现形式为低阻(<10^(-5)Ω·m)高极化(>40%)特征,正是由于石墨的超低阻特性,在石墨矿地球物理勘查中经常遇到“低阻屏蔽”作用,因此,优选有效的电法勘探组合在石墨矿勘查中非常重要。【研究方法】本文选择四川攀枝花中坝晶质石墨矿开展正演模拟,同时对典型矿床开展自然电位法和宽频电磁法的有效性和适用性分析。【研究结果】遵循“从已知到未知的原则”,利用该方法组合在中坝外围唐家坪石墨矿勘查中取得了较好的应用效果,为该区矿产地评价提供了重要支撑。【结论】自然电位法+宽频大地电磁测深法的组合地球物理方法能够有效圈定石墨矿地表范围及深部延展,为相似地质条件下的石墨矿勘查提供了应用示范。