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.

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

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.

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.

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.