导电填料对炭系电热涂料电热性能的影响

研究了石墨含量对炭系电热涂料电热性能的影响,并对以石墨为主要导电填料,配入一定质量的炭黑和碳化硅原料制备的炭系电热涂料电热性能进行了分析讨论。电热性能测试和SEM分析表明:石墨是炭系电热涂料优良的导电填料,当石墨含量为50%(粘结剂为50%)时,在220 V的电压下通电10 min,其涂层的发热功率为18.6 W,发热温度为43℃;配入炭黑和碳化硅原料时,在同等测试条件下,配比为m(粘结剂)∶m(石墨)∶m(炭黑)=5∶3∶2的涂层电热性能最好,发热温度稳定在53℃,可用于民用采暖;配比为m(粘结剂)∶m(石墨)∶m(碳化硅)=5∶4∶1的涂层发热温度可稳定在37℃。实验表明:炭黑比碳化硅对炭系电热涂料的电热性能影响大,能较好地提高炭系电热涂料的电热性能。     

添加剂对薄板坯连铸保护渣熔化温度及黏性特征的影响

以工业渣为原料,采用熔体物性综合测定仪等设备,研究了添加剂Li2CO3、NaF、Na2CO3、冰晶石及硼砂对薄板坯连铸保护渣熔化温度、黏度及流动性的影响。结果表明:加入Li2CO3能显著降低保护渣的熔化温度和黏度,增加流动长度。NaF加入质量分数为10%~20%时,保护渣的熔化温度下降较快,黏度下降缓慢,流动长度增加。加入Na2CO3对保护渣的熔化温度、黏度和流动长度影响不大。冰晶石加入质量分数为5%~15%时,保护渣的熔化温度和黏度降低,流动长度增加;冰晶石加入质量分数为15%~20%时,保护渣的熔化温度增加。硼砂加入质量分数在2%~6%时,保护渣的熔化温度降低,黏度平缓降低,流动长度增加;硼砂加入质量分数超过6%后,保护渣的黏度略有增加。     

反应烧结制备碳化硅陶瓷及其性能研究

以全细粉碳化硅(d50=3.6μm、w(SiC)≥98％)为主要原料,加入炭黑、石墨、减水剂和分散介质等混合均匀后注浆成型,80℃烘干并于1720℃反应烧结制备全细粉碳化硅陶瓷材料.考察了搅拌时间1～5 h、炭黑加入质量分数5.62％～6.93％对素坯性能的影响,并对素坯及烧后试样微观结构进行表征.结果表明:添加石墨所...     

低碳MgO-C材料的抗热震性研究

以电熔大结晶镁砂、天然鳞片石墨、纳米炭黑、酚醛树脂、铝粉等为主要原料制备w(C)=3%的低碳MgO-C材料,以其抗热震性为考核指标,选取颗粒级配、复合抗氧化剂、石墨粒度和复合结合剂4个因素,进行了四因素三水平正交试验。结果表明:在本试验范围内,颗粒级配是影响低碳MgO-C材料抗热震性的主要因素,复合抗氧化剂次之,石墨粒度和复合结合剂的影响基本相当;通过极差分析确定,镁砂颗粒级配(3～1、1～0.088和≤0.088mm的镁砂的质量比)采用50:23:27,复合抗氧化剂采用Al2.5+Mg-Al0.5+B4C0.5,石墨粒度采用10μm的,复合结合剂采用炭黑N220+沥青+酚醛树脂,可制备出抗热震性最佳的低碳MgO-C材料。     

碳的种类对铝锆碳滑板性能的影响

分别对单独加入4%(质量分数)鳞片石墨、炭黑、沥青碳3种碳材料和加入不同碳材料(总质量分数4%)复合的铝锆碳滑板进行了树脂加入量、耐压强度、高温抗折强度、显气孔率、体积密度等物理性能以及抗氧化、抗热震性能比较。试验结果表明添加石墨可以实现低的树脂加入量,试样的显气孔率低,抗氧化性好;添加炭黑可以提高试样的强度;添加沥青碳,则可提高试样的抗热震性,但抗氧化变差;复合添加这3种碳材料,可以得到强度高、抗热震好的铝锆碳滑板试样。     

浮法玻璃用复合澄清剂的HTMOS研究

针对钠钙硅平板玻璃,借助高温熔化原位观测和记录系统(HTMOS),探索了多元复合澄清剂对玻璃熔体中气泡的产生、长大和排除过程的影响,主要研究结果:借助HTMOS装置,我们原位观测到了Na2SO4与C、CeO2复合后的梯级澄清效果.通过高温熔化观测系统,可知单独加入Na2SO4和单独加入CeO2的玻璃中剩余气泡远少于不加入澄清剂的玻璃;而多元复合澄清剂C+Na2SO4+CeO2的使用在达到了梯级澄清的效果同时降低了澄清的起始温度,有利于玻璃熔制温度的降低和熔制时间的减少.     

低炭MgO-C质耐火材料的抗熔渣侵蚀行为

以碱度为 3.0和 1.0的钢渣对石墨含量(w)为 0、2 %、4 %、6 %和 12 %的MgO -C质试样进行了回转抗渣试验 ,并对侵蚀后试样进行了SEM、EDAX和EPMA分析。结果表明 :当石墨含量 (w)≤6 %时 ,试样在两种渣中的侵蚀深度都随石墨含量的增加而减小 ,而当石墨含量达到 12 %时 ,其侵蚀深度又都增加 ;碱度 1.0的渣对石墨含量 (w)≤ 6 %的MgO -C材料的侵蚀严重 ,而碱度 3.0的渣对石墨含量 (w)为 12 %的MgO -C材料的侵蚀严重 ;低碱度渣中Si、Fe对MgO致密层的熔损比高碱度渣中的严重。     

炭质材料对连铸保护渣烧结性能的影响

借鉴耐火材料烧结性能的研究方法 ,通过研究连铸保护渣的炭质材料种类 (中超炭黑、半补强炭黑、鳞片石墨、土状石墨和焦炭 )及含量对烧结性能的影响 ,提出了评价保护渣烧结特性的方法和影响渣圈形成的原因。结果发现 :致密化起始温度Tq和致密化速率U可作为衡量渣圈生成的主要指标 ,U高或Tq低的保护渣的烧结倾向大 ,在使用中易结渣圈 ;在保护渣中加入炭质材料 ,可以降低保护渣的U ,从而抑制保护渣的烧结 ;在试验所用的炭质材料中 ,炭黑降U的效果优于石墨 ,其中中超炭黑的效果最好 ,其次为半补强炭黑和鳞片石墨。     

纳米炭黑分散方法和含量对低碳镁碳材料力学性能的影响

采用加KH-550偶联剂和高速搅拌的方法,将不同量的纳米炭黑N220均匀分散在酚醛树脂中,制成纳米炭黑-酚醛树脂复合结合剂,研究了纳米炭黑含量对复合结合剂黏度及其经1500℃炭化后碳结构的影响,并采用这些复合结合剂制备了w(C)=3%的低碳镁碳试样。研究了纳米炭黑含量(相对于酚醛树脂的质量分别为0、2.5%、5%、10%和15%)对低碳镁碳试样力学性能的影响,同时还与将纳米炭黑以预混合粉方式加入的低碳镁碳试样的力学性能进行了对比。结果发现:1)随着纳米炭黑含量的增加,复合结合剂的黏度迅速增大;2)纳米炭黑-酚醛树脂复合物经1500℃炭化后的碳结构呈光学同向性,但其微气孔数量减少,微气孔尺寸减小,碳结构的石墨化程度提高;3)随着纳米炭黑加入量的增加,低碳镁碳试样的常温抗折强度、高温抗折强度和常温耐压强度逐渐增大;4)将纳米炭黑直接分散在细粉中加入时,试样的常温抗折强度、高温抗折强度和常温耐压强度均比以纳米炭黑-酚醛树脂方式加入时差。     

含钒渣对铝碳材料的侵蚀

为了探讨含矾渣对铝碳材料的侵蚀机制,用动态感应抗渣法研究了w(V2O5)=10%、碱度2.8,w(V2O5)=6%、碱度2.8,w(V2O5)=6%、碱度1.44的3种含钒渣对铝碳材料的侵蚀。结果表明:随着V2O5含量(w)由6%增加到10%,铝碳材料的熔损指数增加;随着碱度的增加,铝碳材料的熔损指数也增加;添加电熔镁砂有助于提高铝碳材料的抗侵蚀性能。显微分析表明:V、Ti元素渗透能力强,渗透深,而尖晶石可固溶少量V2O5、MnO及FeO。     

Effect of Carbon Containing Materials on Pure Carbon Reaction-bonded SiC

Petroleum coke, graphite, gas carbon and lower sulfur carbon black were used to prepare reaction-bonded silicon carbide. The influences of different carbon containing materials on properties of carbonaceous precursors, sintering process, and microstructure of the prepared SiC were researched. The results show that ： （ 1 ） With the density of carbon containing materials increasing, the porosity of carbonaceous precursors decreases and the infiltrating process of liquid silicon is more difficult. （2） The reaction between carbon containing materials and liquid silicon, the volume effect is more obvious with the density of carbon containing materials increasing. （3） As the carbon containing materials density decreasing, residual carbon in reaction bonded SiC also decreases.     

In situ reaction synthesis of Al2O3–SiC nanostructure using different carbon sources

Abstract

The formation of Al₂O₃–SiC nanostructure was studied using three different carbon sources (charcoal activated, graphite and carbon black) mixed with colloidal silica and aluminium nitrate. All mixtures were heated at 1500°C for duration of 30, 45 and 60 min. The results showed that Al₂O₃–SiC powders with an average diameter of ～220 nm and almost equiaxial geometry with aspect ratio of 1–1·2 could only be synthesised from the mixture containing carbon black (30 wt-%) at low heating time (30 min). It was found that the intensity of SiC peaks was the highest in samples containing graphite which was attributed to the higher initial density of this sample.     

疏松型纳米氢氧化镁阻燃聚丙烯

以聚丙烯(PP)为基体,疏松型纳米氢氧化镁(LN-MH)为主阻燃剂,红磷和炭黑为协同阻燃剂,制备了阻燃材料。实验结果表明:包覆剂A8使PP／LN-MH复合材料[(m(PP)／m(LN-MH)为100:40)]力学性能最佳;偶联剂KH550和接枝物又进一步提高了复合材料的力学性能,使PP／LN-MH复合材料和纯PP相当;LN-MH的加入提高了PP的熔融峰温度,降低了结晶度和热失重起始温度,接枝物的加入进一步提高了熔融峰温度,相对增加了结晶度;红磷和炭黑的加入表现出良好的协同作用,在低LN-MH填充量时,加入9 phr红磷或7 phr红磷和5 phr炭黑后阻燃级别达到UL 94 V-0级;通过偶联剂和接枝物进一步改性,能够使复合材料在达到阻燃要求的同时保持良好的力学性能。     

Synthesis of SiC Whiskers from Silicon Nitride in Argon Atmosphere

SiC whiskers were synthesized by carbothermal reduction of silicon nitride. α-Si3N4 and β-Si3N4 powders were used as silicon sources, and graphite, active carbon and black carbon as carbon sources, as well as boron oxide as catalyst. The synthesized SiC whiskers were characterized by XRD and SEM. The results showed that the synthesizing temperature should be above 1 716 K; the decomposition of Si3N4 was the limited step in the synthesis of SiC whiskers; and catalyst not only offered the liquid condition, bu...     

Synergistic effects of carbon fillers in electrically and thermally conductive liquid crystal polymer based resins

Adding conductive carbon fillers to insulating thermoplastic resins increases composite electrical and thermal conductivity. Often, as much of a single type of carbon filler is added to achieve the desired conductivity, while still allowing the material to be molded into a bipolar plate for a fuel cell. In this study, varying amounts of three different carbons (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX Liquid Crystal Polymer. The resulting single filler composites were tested for electrical resistivity (1/electrical conductivity) and thermal conductivity. In addition, the effects of single fillers and combinations of two different carbon fillers were studied via a factorial design. The results indicated that for the composites containing only single fillers, synthetic graphite, followed by carbon fiber, cause a statistically significant decrease in composite electrical resistivity. Composites containing only synthetic graphite, followed by carbon black, and then carbon fiber cause a statistically significant increase in thermal conductivity. For the combinations of two different fillers, the composites containing carbon black/synthetic graphite and synthetic graphite/carbon fiber had a statistically significant and positive effect on thermal conductivity. It is possible that thermally conductive pathways are formed that “link” these carbon fillers, which results in increased composite thermal conductivity. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Electrical conductivity of carbon‐filled polypropylene‐based resins

Adding conductive carbon fillers to insulating thermoplastic resins increases composite electrical conductivity. Often, as much of a single type of carbon filler is added to achieve the desired conductivity and still allow the material to be molded into a bipolar plate for a fuel cell. In this study, various amounts of three different carbons (carbon black, synthetic graphite particles, and carbon nanotubes) were added to polypropylene resin. The resulting single‐filler composites were tested for electrical resistivity (1/electrical conductivity). The effects of single fillers and combinations of the different carbon fillers were studied via a factorial design. The percolation threshold was 1.4 vol % for the composites containing only carbon black, 2.1 vol % for those containing only carbon nanotubes, and 13 vol % for those containing only synthetic graphite particles. The factorial results indicate that the composites containing only single fillers (synthetic graphite followed closely by carbon nanotubes and then carbon black) caused a statistically significant decrease in composite electrical resistivity. All of the composites containing combinations of different fillers had a statistically significant effect that increased the electrical resistivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The influence of carbon‐based fillers on the flammability of polypropylene‐based co‐extruded wood‐plastic composite

Comparative analysis of the effect of carbon‐based fillers with different particle sizes and morphologies on the flammable properties of a co‐extruded wood‐plastic composite is performed. Five carbon‐based fillers, namely carbon black, carbon nanotubes, graphite, expandable graphite, and carbon fibers were loaded into the shell layer of the composite. The flammability was characterized by using the cone calorimeter technique. The nanosized fillers, carbon black and carbon nanotubes, had a larger impact on the peak of the heat release rate, decreasing it by 16% and 17%, respectively. The samples with graphite, expandable graphite, and carbon fibers, decreased the peak of the heat release rate by 10%, 6%, and 11%, respectively. The total heat release decreased slightly for all the samples, except for the carbon fibers–wood‐plastic composite. The effective heat of combustion decreased also slightly, and carbon monoxide production increased for all the studied composites. Copyright © 2015 John Wiley & Sons, Ltd.     

Superheating of the melting kinetics in polymer crystals: a possible nucleation mechanism

Melting kinetics of polymer crystals has been examined experimentally by calorimetric methods utilizing the combination of a conventional differential scanning calorimetry of heat flux type (CDSC-HF) and a temperature-modulated DSC (TMDSC). The superheating effect in the kinetics has been discussed based on a modeling of the melting kinetics. For low-density polyethylene and linear polyethylene, the melting rate showed nearly linear dependence on the degree of superheating, which indicates the kinetics controlled by heat diffusion or by surface kinetics on rough interface. For isotactic polypropylene, poly(ethylene terephthalate) and poly(?-caprolactone), the dependence is non-linear and close to the limiting case of exponential dependence, which indicates nucleation-controlled kinetics of melting. A possible mechanism of the activation process in the melting kinetics has been discussed in consideration of the specific feature of polymer crystals far from its most stable state. The consistency of the results of CDSC-HF and TMDSC has been confirmed by this analysis with a calibration of peak temperature for the instrumental thermal delay in CDSC-HF.     

High rate capability of carbonaceous composites as anode electrodes for lithium-ion secondary battery

Anode materials with high rate capability for Li-ion secondary batteries were investigated by using the mixture of graphite, cokes, and petroleum pitch. Since obvious potential plateaus were obtained at graphite contents above 40 wt.%, which would cause difficulties in perceiving the capacity variations as a function of electrical potential, the graphite content were determined at 20–30 wt.%. The composites with a given content of graphite and remaining content of petroleum pitch/cokes mixtures at 1:4, 1:1, and 4:1 mass ratios were heated at a temperature range of 800–1200 °C. For a given composition of carbonaceous composite, the discharge rate capability improved but the reversible capacity decreased with increasing the heat treatment temperature. Although the reversible capacity increased with increasing content of the petroleum pitch for given graphite content and heat treatment temperature, the discharge rate capability decreased. The carbonaceous composites prepared by the mixture of 30 wt.% graphite and 70 wt.% petroleum pitch/cokes mixture at 1:4 mass ratio with the heat treatment at 800 °C showed relatively high electrochemical properties, of which reversible capacity, initial efficiency, discharge rate capability (retention of discharge capacity in 5 C/0.2 C) and charge capacity at 5 C were 312 mAh/g, 79%, 89% and 78 mAh/g, respectively.