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。     

碳化硅含量对炭/陶复合导电材料组织和性能的影响

以长石、透辉石、石英等为陶瓷基料掺杂石墨、碳化硅,经湿混、干燥、干压成型、快速烧结等工艺制备了复合导电材料。测定了试样的气孔率、吸水率、烧成收缩率、烧失率以及抗弯强度,并分别用XRD和SEM分析晶相组成和断面显微结构,研究了碳化硅含量对复合材料电阻率的影响。实验结果表明:碳化硅的含量由1%增大到3%时,炭/陶复合导电材料的显微结构无显著变化,气孔率增大,烧成线收缩率降低,弯曲强度下降,电阻率变大;碳化硅含量由3%增大到9%时,炭/陶复合导电材料的陶瓷颗粒界面上形成一层白色碳化硅颗粒层,气孔率减小,弯曲强度增大,电阻率急剧降低;与碳化硅含量为1%的炭/陶复合导电材料相比,碳化硅含量增大到9%时,炭/陶复合导电材料孔隙率减小,弯曲强度增大,电阻率降低。     

复合型无机炭系电热涂料的研究

针对传统电热涂料表面发热温度偏低、耐热性较差和温升启动慢等缺陷,研制出了在安全电压下具有优良电热性能的复合型无机炭系电热涂料。采用在耐热无机粘结剂中添加复合型炭系粉料,在耐热载体表面预埋电极后用涂覆法成型固化,再在其表面喷涂含铝高温涂料经二次固化制得复合型无机炭系电热涂层。用SEM电镜对涂层微观结构和粒子分布状态进行表征和分析;用伏安法体积电阻率测试仪和电参数测定仪对电热涂层进行电学、热学等性能的测试。研究结果表明:在相同条件下,采用无机粘结剂为基体的电热涂层比用改性树脂的涂层具有更优良的电热性能;在室温为(19±2)℃时,电压36V,通电18min,复合导电填料含量40%制得的无机炭系电热涂层表面温度可达到299.0℃;而以改性树脂为粘结剂制得的涂层的表面温度仅为79.1℃左右。     

碳纤维复合炭黑导电砂浆导电性能及其电热功能研究*

本研究介绍了碳纤维复合炭黑导电砂浆的制备方法、导电性能和电热功能研究。导电砂浆作为一种新型的功能性建筑材料，具有导电性能和电热功能，可以应用于感应加热、防冰除雪等多种场景。为了改善导电砂浆的性能，试验探究了采用碳纤维和炭黑复合的制备方法，并分析了碳纤维掺量对导电砂浆电阻率和电热功能的影响。实验结果表明，最佳的碳纤维掺量为胶凝材料质量分数的1%，炭黑掺量为胶凝材料质量分数的0.4%，在通入10 V交流电压下1 h后，试样温度升高13.3℃。电性能测试还证实了碳纤维复合炭黑导电砂浆具有低电阻率和高发热功率密度，具有较强的融雪或除冰能力。然而，为了将这一试验成果应用于更大的场景，还需要进一步研究导电砂浆试样。     

SiC电热陶瓷的组成与导电性能

通过铁系元素、稀土元素、铝元素和一些高价离子对碳化硅陶瓷导电性能的影响,研究了在还原气氛下碳化硅电热陶瓷的组成与导电性能的关系,从而获得了在小于１５００ ℃还原气氛下烧成,电阻率为０－０５ ～０－８５ 欧姆·米的碳化硅陶瓷电热材料。     

生石油焦制备的多孔炭材料吸附性能及电热性能研究

以挥发分含量较高的未煅烧生石油焦为原料,以KCl为主要活化剂,采用模压成型,化学活化的方法制备出块状多孔炭材料。考察了活化剂用量与成型压力对多孔炭材料吸附性能和电热性能的影响及多孔炭材料电热性能在解吸附中的应用。当活化剂与生石油焦用量比为5,成型压力为20MPa时制得的块状多孔炭材料的吸附性能和电热性能最理想,通电加热1min后该多孔炭材料解析吸附物的效果显著。     

电热涂料的研制与应用

研制了性能稳定的电热涂料，并列举了该涂料的性能指标。讨论了基料树脂、导电材料、固化温度、固化时间和涂层厚度对涂料性能的影响c以电暖器为例，介绍厂电热涂料作为发热元件的应用实例。     

PP/PCL/石墨/碳纳米管复合材料的制备及电性能分析

采用熔融共混法制备了石墨（G）、碳纳米管（CNTs）与聚丙烯（PP）、聚己内酯（PCL）导电复合材料,通过改变G的添加量制备了系列导电复合材料。主要测试了熔体流动速率、力学性能、导电性能、电热性能,并进行了电子显微镜观察结构、差示扫描量热法分析、热失重分析。结果表明,PCL与PP混合后,PP的拉伸强度提升了4.375 MPa,在加入G/CNTs之后,力学性能受影响较大下降了约73.5 %;G/CNTs的加入还能有效降低PP的电阻率,使其从绝缘体变为半导体材料电阻率为7.83×10⁶ Ω·m;PP与PCL共混后复合材料的热稳定性得到了显著提高,初始分解温度从368.88 ℃升高至398.95 ℃,在加入G/CNTs管后又进一步提高至408.78 ℃。     

C-B4C-SiC与Ti组分的原位反应及热压烧结

以炭黑、炭纤维、Ｂ４Ｃ、ＳｉＣ、Ｓｉ、ＴｉＯ２和ＴｉＣ为原料制备了不同ＴｉＯ２和ＴｉＣ含量的炭／陶复合材料,采用原位合成及热压技术研究了不同ＴｉＯ２和ＴｉＣ含量对多组分炭／陶复合材料的组成、结构和性能的影响。在烧结过程中ＴｉＯ２和ＴｉＣ与Ｂ４Ｃ反应原位生成ＴｉＢ２,Ｓｉ和ＴｉＯ２分别与Ｃ反应生成ＳｉＣ和ＴｉＣ,这些陶瓷相的生成对提高炭／陶复合材料的力学性能有显著作用。加入ＴｉＯ２能使炭／陶复合材料在较低的温度下实现致密化烧结,获得了抗弯强度达４３０ＭＰａ的炭／陶复合材料     

纤维体积含量对炭／炭复合材料性能的影响

通过对不同纤维体积含量的炭／炭复合材料进行力学性能、导热、导电性能试验,分析了纤维体积含量对炭／炭复合材料性能的影响。初始坯体的纤维体积含量对炭／炭复合材料力学性能影响较大,导热、导电性能则与材料内部结构关联较大而与纤维体积含量的关系不大。预制坯体的纤维体积含量选为25％至30％为最好。     

LiFePO4/C复合材料的制备和性能

采用高温固相合成法二次灼烧工艺制备锂离子电池正极复合材料LiFePO4/C。经300℃和650℃二次灼烧,得到了从纳米到亚微米尺寸的LiFePO4和LiFePO4/C复合材料。X射线衍射(XRD)结果表明,所得到的LiFePO4和LiFePO4/C样品具有单一的橄榄石型晶体结构,且具高纯度。在多种碳源(如乙炔黑、Vulcan XC-72碳黑、鳞状石墨、各向异性石墨和葡萄糖)制备的LiFePO4/C复合材料中,以葡萄糖为碳源合成的样品具有最好的电化学性能。在电池工作温度由室温提高到40℃时,由于复合材料的电子电导率增大和锂离子在材料中的扩散速度加快,电池的充放电循环性能明显提高。     

碳化锆陶瓷有机前驱体的热解过程

合成了碳化锆陶瓷有机前驱体,研究了其在热解过程中化学成分和物相组成变化,探讨了从有机高分子向无机陶瓷转化的机理,对碳热还原反应进行了热力学分析。结果表明,前驱体在600℃以下完成了有机结构的断裂、裂解碎片的重排与挥发,600℃以上裂解产物不再具备有机特征;随热解温度升高,无定型碳和单斜相ZrO2逐渐生成,大于1200℃时可检测到立方相ZrC,1400℃时单斜相ZrO2基本消失;1500℃时完成碳热还原反应,在远低于热力学反应温度的条件下生成了高度结晶的纳米尺寸的立方相碳化锆陶瓷。     

裂解碳包覆对SiC纳米纤维增强SiC陶瓷基复合材料性能的影响

以SiC纳米纤维(SiC_nf)为增强体,通过化学气相沉积在SiC纳米纤维表面沉积裂解碳(PyC)包覆层,并与SiC粉体、Al₂O₃-Y₂O₃烧结助剂共混制备陶瓷素坯,采用热压烧结工艺制备质量分数为10%的SiC纳米纤维增强SiC陶瓷基(SiC_nf/SiC)复合材料。研究了PyC包覆层沉积时间对SiC_nf/SiC陶瓷基复合材料的致密度、断裂面微观形貌和力学性能的影响。结果表明:在1 100 ℃下沉积60 min制备的PyC包覆层厚度为10 nm,且为结晶度较好的层状石墨结构;相比于纤维表面无包覆层的复合材料,复合材料的断裂韧性提高了35%,达到最大值(19.35±1.17) MPa·m^1/2,抗弯强度为(375.5±8.5) MPa,致密度为96.68%。复合材料的断裂截面可见部分纳米纤维拔出现象,但SiC_nf/SiC陶瓷基复合材料界面结合仍较强,纳米纤维拔出短,表现为脆性断裂。     

多孔SiC陶瓷/石蜡复合相变材料定型封装及热性能研究

以微米级SiC粉为原料,采用冷冻干燥工艺制备具有连贯层状孔结构的SiC陶瓷。以多孔SiC陶瓷为基体,石蜡为相变芯材,通过真空浸渍法制备多孔SiC陶瓷/石蜡复合相变材料,研究了石蜡在层状多孔SiC陶瓷内的浸渗行为及复合材料的储热性能。结果表明,层片状多孔SiC陶瓷的显微形貌对石蜡的浸渗过程及储热性能有明显影响。当石蜡负载量为21.7%(质量分数)时,复合相变材料熔融温度为59.6 ℃,凝固温度为53.9 ℃,相变潜热为28.4 J/g,室温下的热导率为2.4 W·(m·K)^-1。复合相变材料吸热峰和放热峰强度随着石蜡负载量减少而降低,当温度为200 ℃时,多孔SiC陶瓷/石蜡复合相变材料失重为5%(质量分数),表明材料具有良好的热稳定性。复合相变材料在100 ℃热处理30 min后陶瓷基体未发生形变,经100次热循环后具有稳定的相变潜热和良好的定型能力。     

Performance optimization of complicated structural SiC/Si composite ceramics prepared by selective laser sintering

Combining reaction-bonded (RB) process and selective laser sintering (SLS) method is an effective approach to prepare ceramic components with complex shapes. The purpose of this paper is to find efficient ways to improve the performance of SiC/Si composites prepared by SLS/RB technologies. Effects of epoxy resin binder on the performance and microstructure of preforms and sintered bodies were studied first. Then, based on the above results, graphite with low reactivity was used as an alternative slow-release carbon source to promote sintering densification process and improve the carbon density of preforms. When the added amount of graphite increased, clusters of nanometer-sized SiC grains formed and the silicon phase transformed into pieces, which reduced the content and dimension of silicon phase. Furthermore, by applying a two-step sintering method, the residual silicon content of SiC/Si composites decreased further and the flexural strength at high temperatures increased.     

氧化石墨烯改性磺酸型水性聚氨酯的制备与性能研究

首先对石墨进行氧化处理制备氧化石墨(GO),然后对GO进行超声处理得到氧化石墨烯(GOs),并通过共混法制备了水性聚氨酯(WPU)/GOs复合材料。讨论了超声分散以及GOs加入量对WPU/GOs复合材料力学性能和热稳定性的影响。结果表明,经过超声分散的复合材料的力学性能比未超声分散的好;随着GOs含量的增加,复合材料的拉伸强度先增大后减小,断裂伸长率逐渐减小;加入质量分数0.50%的GOs,其WPU/GOs复合材料的热分解温度可提高44.7℃,明显提高WPU的热稳定性。     

Enhanced microwave‐absorbing property of precursor infiltration and pyrolysis derived SiCf/SiC composites at X band: Role of carbon‐rich interphase

Ceramic matrix composites (CMCs) can be microwave‐absorbent when endowing the composite constituents with proper dielectric properties. In this work, we report a new method to enhance the microwave‐absorbing property of CMCs by in situ fabrication of a carbon‐rich interphase at the fiber/matrix interface. This was achieved in a SiC fiber reinforced SiC matrix (SiCf/SiC) composite fabricated by precursor infiltration and pyrolysis (PIP). We found that as the PIP temperature increased from 800 to 1000°C, the microwave‐absorbing property of the SiCf/SiC composite was significantly enhanced at X band, which also surpassed those of the SiC fiber and monolithic SiC ceramic fabricated at the same temperature. The dominant mechanism was studied by decoupling the effect of individual SiC fibers, SiC matrix, and fiber/matrix interface. The results showed that the SiC fiber and SiC matrix were barely microwave‐absorbent, due to their low dielectric losses. The microwave‐absorbing mechanism was finally ascribed to the fiber/matrix interface, which was carbon‐rich, containing Si and O elements. The interphase showed a conductivity that was superior to that of the fiber and the matrix, and mainly dominated the dielectric property of the overall composite. The results highlight the role of carbon‐rich interphase on the microwave‐absorbing property of CMCs.     

添加剂对炭/石墨复合材料性能的影响

以酚醛树脂为黏结剂,石油焦、石墨为原料,分别添加磷酸氢二钠、硼酸、碳化硅,在1 100℃下热处理,制备出炭/石墨复合材料,并考察了其机械性能、微观结构和热性能。研究表明:经过焙烧后,炭/石墨复合材料中的添加剂起到增强颗粒间键合能力,提高炭/石墨复合材料机械强度的作用。同时,硼酸、碳化硅可以在炭/石墨复合材料表面形成抗氧化物质,使其具有更好的抗氧化能力,起始氧化温度提高180℃,终了氧化温度提高了200℃。     

Thermal conductivity studies on Si/SiC ceramic composites

Ceramic heat exchangers are increasingly used in many nuclear power plants. Silicon carbide has been treated as a promising material for heat exchanger application since it has good thermal conductivity and corrosion resistance. In this work, four different types of Si/SiC ceramic composites were prepared by liquid silicon infiltration technique. Thermal conductivities of these ceramic composites at different temperatures are measured by the laser flash thermal conductivity method. Results show that the presence of free carbon and voids are notably affecting the thermal conductivity of these materials.     

Optimized ablation resistance behavior and mechanism of C/SiC composites with high thermal conductive channels

Aimed to enhance the high-temperature service performance of C/SiC composites in high-speed aircraft thermal protection system, in this article, pitch-based carbon fibers were used to construct high thermal conductive channels to improve the heat transfer capability of C/SiC composites. The results revealed that the as-prepared composites equipped with 4.7 times higher thermal conductivity than that of conventional C/SiC composites. The oxyacetylene flame ablation test confirmed that the constructed high thermal conductive channels, which quickly conducted the heat flow from the ablation center area to other areas is the main reason of as-prepared composites exhibiting a very impressive ablation resistance property. Briefly, the ablation temperature of the as-prepared composite surfaces considerably dropped by about 300°C compared with conventional C/SiC composites, while the linear ablation rate and mass ablation rate of the composites are 1.27 μm/s and 0.61 mg/s respectively, which is superior to many recent reports, demonstrating that this article provides a simple but highly effective measure to improve the ablation resistance property of C/SiC composites.