膨胀石墨压块的制备及其导热性能研究

为探索和优化微波法制备膨胀石墨及石墨压块成型工艺,利用激光粒度仪、扫描电镜对膨胀石墨及其压块的形貌、孔隙结构等微观结构进行表征,并进行正交试验分析研究了微波功率、微波时间、膨胀石墨粒径、压块成型压力、单次膨胀量等因素对压块导热性能的影响.结果 表明,微波功率和微波时间对压块导热性能有显著影响,功率过低和时间过短会导致石墨膨胀不充分,而功率过高和时间过长则会导致石墨蠕虫被过度灼烧而断裂,膨胀石墨粒径、压块成型压力、单次膨胀量对压块导热率无显著影响.依据实验和分析,以压块导热系数为目标确定了膨胀石墨压块最优制备条件:微波功率为700 W、微波时间为70 s、膨胀石墨粒径为80 ～ 100目、单次膨胀量为6.0g、压块成型压力为200 MPa,该条件下压块导热系数达到5.78 W/(m·K).     

膨胀石墨混杂填充聚丙烯复合材料导热性能研究

以不同粒径的膨胀石墨(EG)为填料,通过双辊混炼热压成型制备聚丙烯(PP)/EG导热复合材料,研究了EG填充量、粒径和不同粒径混杂填充对复合材料导热性能的影响。结果表明:随着EG填充量的增加,复合材料的热导率提高。当填充量超过30%时,热导率提升幅度增大,达到渗流阈值;当EG填充量为50%时,复合材料的热导率达到1.791W/(m.K);大粒径填料粒子提高复合材料热导率的能力优于小粒径粒子;大小粒径按合适比例混杂填充得到的复合材料热导率最高。     

碳纳米管-膨胀石墨/环氧树脂复合材料的导热性能

在环氧树脂中添加多壁碳纳米管和膨胀石墨作为填料,以提高环氧树脂的导热性能. 结果表明,添加0.5wt%多壁碳纳米管时,环氧树脂的最佳导热系数为0.3448 W/(m?K),比不添加时提高30%;添加0.75wt%羧基改性多壁碳纳米管时,环氧树脂的最佳导热系数为0.3813 W/(m?K),比添不加时提高40%;同时添加多壁碳纳米管和膨胀石墨后,环氧树脂导热系数可进一步提高到0.4039 W/(m?K),表明在环氧树脂中添加混合填料,二者可在环氧树脂中形成有效的导热网络,能进一步提高聚合物的导热性能.     

传热传质强化介质石墨的膨胀工艺及导热性能研究

对膨胀石墨在不同膨胀温度及不同膨胀时间下进行了膨胀工艺与导热系数测试的研究.研究中,分别用平面热源法和称重法测出不同膨胀条件下石墨的导热系数和密度.然后根据导热系数最优化的原则,结合未膨胀晶体的观测状态以及密度的变化,找出膨胀石墨的最佳膨胀工艺.结果发现膨胀石墨在各个膨胀温度下都存在着自己的最佳膨胀工艺.经过不同膨胀温...     

可膨胀石墨电化学法制备及其研究

采用电化学法取代传统氧化剂可以制备可膨胀石墨,本文在综合多次实验和参数的基础上,论述了电解液浓度,氧化时间,电流密度可对膨胀石墨的影响。     

膨胀石墨／二氧化钛复合材料的制备与性能研究

本文主要研究了膨胀石墨／二氧化钛复合材料的制备,采用直接膨化的膨胀石墨与钛酸丁酯的醇溶液混合法制备膨胀石墨／二氧化钛复合材料,并分析了膨胀石墨／二氧化钛复合材料的物理性能,以甲基橙溶液的光催化降解反应为探针反应,评价了该复合材料的催化性能。     

膨胀石墨制备及性能研究

采用化学氧化法合成了可膨胀石墨,分析了插层工艺参数对膨胀容积和残余硫含量的影响,初步探讨了可膨胀石墨的插层机理,确定了低硫膨胀石墨的合理工艺参数.最佳配比为石墨∶浓硫酸∶高锰酸钾∶三氯化铁=1.0∶0.33∶0.80∶0.15.其最佳工艺条件反应温度为50℃,反应时间为60min.制得膨胀石墨pH值5.2;水分0.62%;灰分2.8%;挥发分8.6%;硫含量0.48%;膨胀容积235ml/g.     

可膨胀石墨的制备

探讨了分别用过二硫酸铵及过氧化氢作氧化剂制取可膨胀石墨时,氧化剂的浓度、硫酸的浓度、浓硫酸与石墨的重量比、反应温度、反应时间诸因素对可膨胀石墨膨胀容积的影响,并得出最佳反应条件。     

细鳞片膨胀石墨／聚苯胺导电复合材料的制备研究

以十二烷基苯磺酸钠为乳化剂,过硫酸铵为聚合引发剂,盐酸和细鳞片膨胀石墨为掺杂剂,利用乳液聚合法制备了细鳞片膨胀石墨／聚苯胺导电复合材料。通过正交实验,找到了膨胀石墨的掺杂量、盐酸用量、乳化剂及引发剂对电导率影响规律。最佳实验条件为：石墨掺杂6％,盐酸6mL,乳化剂5g,引发剂3．25g。该条件下的电导率为0．75S／cm。证明石墨的加入能有效提高聚苯胺的电导率。     

影响膨胀石墨体积的制备工艺研究

采用HClO4/H3 PO4/CrO3氧化插层体系制备低温可膨胀石墨,通过对反应物用量、反应温度及反应时间、水洗温度及水洗程度、干燥温度、膨胀温度进行研究,确定了膨胀石墨体积的影响因素.结果表明:反应物m(C)∶m(HClO4)∶m(H3PO4)∶m(CrO3)=1∶3.0∶1.5∶0.8,反应温度45℃,反应时间70...     

微波法制备膨胀石墨及其膨胀特性

以鱼鳞片石墨为原料, 浓硫酸作为插层剂, 高锰酸钾作为氧化剂, 采用化学氧化法制备石墨插层物, 再利用微波辐射石墨插层物快速制备膨胀石墨。膨胀后的石墨颗粒呈"蠕虫"状, 蓬松粗大。随着鳞片石墨尺寸的减小, 膨胀石墨颗粒变得更加纤细, 达到最大膨胀体积时高锰酸钾的用量也随之减少。最佳微波时间为30～60 s, 此时间段内石墨膨胀完全并且无烧蚀。对于3种不同尺寸的鳞片石墨, 颗粒度大于0.42 mm的鳞片石墨在混合质量比m(石墨):m(H₂SO₄):m(KMnO₄)=5:10:4时, 达到最大膨胀体积为285 ml·g^-1。     

膨胀石墨基相变储能材料的研究

利用膨胀石墨孔隙结构的吸附性能,制备了石蜡/膨胀石墨、聚乙二醇/膨胀石墨、十四醇/膨胀石墨相变储能复合材料,用差示扫描热量法研究了材料的热性能.结果表明,复合材料的相变潜热随着石蜡、聚乙二醇、十四醇含量的增加而增加.复合材料的导热性能随着石蜡、聚乙二醇、十四醇含量的增加而小.膨胀石墨的多孔结构对石蜡、聚乙二醇、十四醇有很好的吸附性能,石蜡、聚乙二醇、十四醇在固一液相变时,未见有液态石蜡、聚乙二醇、十四醇的渗出.     

高性能定形复合相变储能材料的制备及热性能

对现有定形复合相变材料的制备方法进行改进,采用“熔融吸附-模压成型”的方法,以硬脂酸(stearic acid,SA)为相变材料,膨胀石墨(expanded graphite,EG)为多孔基体,制备了16种不同参数的样品,并对其进行了微观形貌表征、热物性测试、热稳定性研究及热性能分析。相关研究表明:SEM微观形貌显示样品内部出现致密的石墨片层结构,SA均匀分布在石墨片层中,且压块密度越大,片层结构形态越规则;DSC测试结果显示样品几乎没有过冷度,EG的加入与压块处理对SA本身的相变潜热和相变温度几乎没有影响;Hot Disk测试结果显示EG的加入显著提高了样品的轴向和径向热导率,随着EG含量的增加,径向热导率高达23.77 W·m^-1·K^-1,发现两个方向上热导率的差异随压块密度的增加而增大,最大相差5.4倍;储/放热循环实验发现压块密度越大、EG含量越低的样品,SA越容易发生泄漏;通过成型密度及质量配比的优化可实现对复合材料的热稳定性调控,发现EG质量分数为25%、密度为950 kg·m^-3的样品具有较好的综合性能。与传统定形复合相变材料的成型方法相比,该方法可进一步提高复合相变材料的综合热性能,与纯相变材料相比其热导率可提高130倍以上,且具有简单易操作的特点。     

高导热膨胀石墨/棕榈酸定形复合相变材料的制备及储热性能研究

采用棕榈酸(palmitic acid, PA)作为相变材料,膨胀石墨(expanded graphite, EG)作为添加基质,通过“熔融共混-凝固定形”工艺制备了PA/EG定形复合相变材料以提高相变材料的综合性能。预测并制备了21种不同配比的定形复合相变材料,对其形貌结构和孔隙率进行了微观表征与理论分析,并在此基础上对样品进行了传热性能分析、热物性测试、热稳定性研究和储热性能分析。SEM形貌分析显示所使用工艺可使棕榈酸能较好地被吸附于膨胀石墨的孔隙结构并使之均匀分布;DSC测试结果表明定形复合相变材料[70%(质量) PA]的焓值为193.01 J/g,纯PA的焓值为275.35 J/g,对应于熔点分别为61.08℃和59.53℃。EG的添加,可有效提高相变材料的热导率。当样品密度为900 kg/m³,EG含量为30%(质量)时,定形复合相变材料的热导率为14.09 W/(m·K),相比于纯PA[0.162 W/(m·K)]提高约87倍;对制备的样品进行50次循环稳定性实验,EG含量为24%(质量)和30%(质量)的样品形态均未出现明显变化,表现出良好的充放热循环稳定性。     

改性膨胀石墨在POE中的分散及其对性能的影响

将膨胀石墨分别经过超声波、酸化和表面活性剂处理,得到的改性产物添加到聚烯烃热塑性弹性体(POE)中,采用扫描电子显微镜(SEM)对改性膨胀石墨在POE中的分散状况进行了分析,并对复合材料的力学性能和电学性能进行了评价,研究结果表明,膨胀石墨在POE中呈现出团聚状态,团聚的膨胀石墨仍具有孔状结构,膨胀片层分散不均匀,改性...     

Preparation and characterization of high‐density polyethylene/expanded graphite conducting masterbatch

High level of expanded graphite (EG) was melt‐blended with high‐density polyethylene to prepare electrical conducting masterbatch. Some factors such as processing temperature, EG contents, treating time were discussed for the effect on electrical and mechanical properties of composites. Results showed that EG tends to reunite while the content of EG is higher than 60% because of the large aspect ratio and surface area of EG nanosheets. In addition, increasing processing temperature and mixing time appropriately could enhance the dispersion of EG, leading to improvement in electrical and mechanical properties. Scanning electron microscopy (SEM) measurements were used as an assistant analysis to study the microstructure of composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Fabrication of polyethylene/graphite nanocomposite from modified expanded graphite

A novel process was employed to fabricate a polymer/expanded graphite nanocomposite by modifying the conducting filler expanded graphite (EG) with unsaturated polyester resin (UPR). The modified expanded graphite (MEG) was prepared from EG in which the graphite nanosheets, already present in EG, were wrapped and isolated by the UPR during processing. The as‐prepared MEG was reduced to powder form to improve its dispersion in the matrix. MEG powders were embedded into a high‐density polyethylene (HDPE) matrix via melt‐extrusion in a single‐screw extruder to prepare the conducting composite. The as‐prepared HDPE/EG conducting composite exhibited a low percolation threshold of ～5.7 wt% due to the high aspect ratio of graphite nanosheets. Mechanical properties such as the tensile and impact strength were also studied. Scanning electron microscopy was used to characterize the microstructure of EG, MEG powder and the resulting nanocomposites. Copyright © 2006 Society of Chemical Industry     

膨胀石墨的工艺优化及性能研究

利用混酸法与单酸法制备膨胀石墨,通过XRD、FESEM对2种制备方法进行比较并优化工艺条件,对吸附性能进行表征。实验得出,混酸法制备膨胀石墨的最佳工艺为:原料质量配比m(H2SO4)∶m(HNO3)∶m(石墨)=3∶1∶1,m(石墨)∶m(高锰酸钾)=1.00∶0.15,膨化温度为900℃;与单酸法相比,混酸法制备的膨胀石墨膨胀效果明显,吸附性能好,产物结构较规整。     

Synthesis of boron and nitrogen-doped expanded graphite as efficient reinforcement for Al2O3-C refractories

Boron and nitrogen doped expanded graphite (B-doped EG & N-doped EG) were synthesized for the first time by annealing the mixtures, obtained from the suspensions of expanded graphite (EG) with boric acid and urea, respectively. Afterwards, the doped EG were introduced into Al₂O₃-C refractories by partially replacing the graphite flake. Synthesized materials were characterized using SEM-EDS, XPS, XRD, TG-DSC and Raman Spectroscopy. Also, evaluation of various mechanical properties and oxidation resistance tests were conducted. Boron (B) and Nitrogen (N) were successfully introduced into the C skeleton via different C-B bonds (B4C, B-sub-C and BC2O) and C-N bonds (pyridine-N, amino-N and graphitic-N) respectively, maintaining the hexagonal graphitic lattice and lower reactivity. Compared to as-received EG, the B-doped EG and N-doped EG remained relatively intact structure in Al₂O₃-C refractories at high temperature due to their less defects and lower reactivity. Addition of B-doped EG and N-doped EG into Al₂O₃-C refractories showed improved mechanical properties such as modulus of rupture (CMOR), force, displacement and thermal shock resistance. Besides, the Al₂O₃-C specimens containing B-doped EG and N-doped EG exhibited significantly better oxidation resistance, which further promote the reinforcement effect of doped EG in Al₂O₃-C refractories during actual service condition.