聚酰亚胺PI/SiC复合薄膜材料的制备及特性

用化学合成法制备用于电子封装中的聚酰亚胺基复合介电材料,并通过透射电镜、红外光谱仪对复合薄膜材料组织观察、结构表征.结果表明,聚酰亚胺基复合材料实际是一种共聚物,属于分子杂化复合材料,是纳米碳化硅小分子均匀分散在大分子聚合物基体中的复合材料体系,介电常数较低,平均值为ε=2.3,最低达ε=2.0,吸水性也较低.     

介电性材料聚酰亚胺的改性研究

依据化学合成原理,采用原位一体工艺,合成聚酰胺酸(PAA),通过正硅酸乙酯的改性,制成聚酰亚胺复合材料;采用SME、UV、傅立叶红外变换表征性能.结果表明,无机小分子在PI基体中分散情况均匀、良好,复合材料对紫外光有优越的吸收性能,并具有低的的介电常数.     

微-纳米SiC/聚丙烯复合材料的制备与力学性能

SiC具有优异的力学与功能性能,作为增强相,在复合材料领域具有广阔的应用前景.采用双螺杆挤出、注塑成型方法制备了微-纳米SiC/聚丙烯(PP)复合材料.分别采用硅烷(KH-550)和钛酸酯(NDZ-201)两种偶联剂对微米(10 ìm)和纳米(50 nm) SiC复合粉体进行表面处理,研究了偶联剂、SiC粉体粒度及添加量对SiC/PP复合材料的弯曲强度、冲击强度、弯曲模量、弹性模量和热变形温度的影响.结果表明,经KH-550/NDZ-201混合偶联剂改性的微-纳米SiC粉体共同增强PP材料的综合力学性能最好,其弯曲强度、冲击强度、弯曲模量、弹性模量和热变形温度比纯PP材料分别提高了40%,8.7%,141%,142%和33%.经钛酸酯改性的SiC/PP复合材料的力学性能优于硅烷和混合偶联剂(KH-550/NDZ-201)改性的SiC/PP复合材料.     

Ni/ZrO_2复合材料力学及介电性能研究

采用热压烧结方法,以氧化钇部分稳定氧化锆(Y-PSZ)粉体及不同粒径的金属Ni为原料,制备了Ni/ZrO2复合材料,研究了其力学和介电性能,探讨了烧结过程中Ni形貌的变化对复合材料介电性能的影响.结果表明,随不同粒径Ni粉的掺入,复合材料的抗弯强度减小,且较大粒径的Ni使材料抗弯强度减小更快.随Ni含量增加,复合材料断裂韧性增强.复合材料的介电常数和损耗与Ni粉含量和粒径有关.Ni含量相同时,较大粒径Ni粉的掺入使复合材料具有较高的介电常数和损耗,这是由于在烧结过程中Ni粉形貌发生变化引起的.     

微电子层间绝缘材料的制作与介电常数测试

将纳米碳化硅粉体材料掺进PAA中,合成碳化硅SiC／PAA,经加热固化制成固体复合材料;利用不同型号的阻抗分析仪表征性能,分析测试,比较介电常数,其最低可达ε=2．0,平均值达ε=2．2,比基体聚酰亚胺（介电常数为3．4）及传统的的低介电材料二氧化硅（介电常数为4．0）显著降低。     

聚酰亚胺磁性复合材料的研制

将不同量的纳米三氧化二铁在分散剂等条件下与自制的聚酰亚胺复合,制成聚酰亚胺/纳米氧化铁复合材料,采用古埃法(Gouy's)、红外光谱(FTIR)、吸水性能测试、拉伸强度等手段表征了材料的结构及特有的超顺磁性。结果表明,这种复合材料具有纯聚酰亚胺所不具备的超顺磁性,且吸水率下降,拉伸强度好。     

固化工艺对聚酰亚胺复合材料影响研究

将纳米碳化硅掺入热固型聚酰亚胺前驱体聚酰胺酸中,采用溶胶凝胶法,经两种不同的固化工艺,制备了不同的聚酰亚胺基复合材料.红外吸收情况表明,固化工艺直接影响亚胺化脱水成环,不同的加热脱水方法导致材料的抗吸湿性能显然不同,微观组织均匀分布也受到一定程度的影响;并发现材料介电常数出现很大差异,常规单一温度固化工艺合成复合材料介电常数为ε=2.6,但采用多个不同温度依次加热固化材料,其介电常数低达ε=2.0,比前者下降了30%.     

高性能Al/PVDF复合材料制备及介电性能

以聚偏氟乙烯(PVDF)为基体,选用普通的铝粉为填充组分,采用一种简单的溶液共混的方法制备了两相复合厚膜材料,运用TEM、SEM 手段对复合物的微观形貌进行了表征,并研究了不同添加量的铝粉对复合材料的介电性能(介电常数、介电损耗和电导率)的影响.结果表明:铝粉的加入不仅提高了材料的介电常数,而且还具有很低的介电损耗,材料并未出现明显的渗流效应.     

TiO2/PLCL可降解聚合物纳米复合材料的制备及形状记忆性能

制备TiO2/聚(L-丙交酯-ε-己内酯)(PLCL)纳米复合材料并研究其性能.采用ε-己内酯开环聚合法对TiO2纳米粒子进行表面改性,通过傅立叶变换红外光谱(FTIR)、热重分析(TGA)和透射电子显微分析(TEM)对聚己内酯(PCL)接枝改性后的TiO2纳米粒子(g-TiO2)进行表征.g-TiO2纳米粒子能均匀地分散在三氯甲烷溶液中.采用溶液浇铸的方法成功地制备了TiO2/PLCL复合材料.研究g-TiO2纳米粒子的含量对材料力学性能和形状记忆性能的影响.结果表明,5％ g-TiO2/PLCL复合材料的力学性能有显著的提高,与纯PLCL相比,抗拉强度提高了113％,伸长率提高了11％.含有g-TiO2纳米粒子的复合材料的形状记忆性能优于纯PLCL.g-TiO2纳米粒子具有物理交联作用,有助于形状记忆效应的提高.     

金刚石磨具纳米Si3N4改性聚酰亚胺树脂结合剂研究

本文研究了纳米Si3N4改性的聚酰亚胺树脂及其在金刚石树脂磨具中的应用.采用傅立叶红外光谱、扫描电镜、热重分析(TG)等方法对改性树脂的结构与性能进行了表征.结果表明:纳米氮化硅可与聚酰亚胺形成化学键,并均匀地分散在聚酰亚胺中,没有明显的团聚现象.研究发现纳米Si3N4可以明显改善聚酰亚胺树脂的力学性能和耐热性,从而提高树脂磨具的强度和导热性.其中金刚石树脂磨具抗折强度和硬度在7%纳米Si3N4时同时达到最大,其中抗折强度提高21.4%,硬度提高12%.     

Effect of multi-walled carbon nanotubes on tribological properties of lubricant

After purified by mixture of sulfuric acid and nitric acid, the multi-walled carbon nanotubes(MWNTs) were modified with stearic acid(SA). The modified carbon nanotubes as lubricant additive were utilized to prepare lubricant, and the effects of carbon nanotubes on the tribological properties were investigated by using a pin-on-plate wear tester. The surface structure of MWNTs was examined by transmission electron microscopy, Raman spectroscopy and infrared spectroscopy. The results show that the surfaces of MWNTs are coated with a modified layer of SA. Furthermore, the modified MWNTs as lubricant additive can effectively improve the friction-reduction and antiwear ability of lubricant. The friction coefficient of base lubricant decreases by about 10% and the wear loss of base lubricant decreases by 30%-40% when the concentration of modified MWNTs in lubricant is 0.45 %. In addition,the mass ratio of SA to MWNTs influences the friction-reduction and anti-wear ability of the modified MWNTs as lubricant additive. The optimum mass ratio of MWNTs to stearic acid is about 3 : 8 - 1 : 2.     

The effect of different hard segments in polyurethane on the electrical conductivity of polyurethane grafted multi-walled carbon nanotube/polyurethane nanocomposites

Polyurethane (PU) grafted multi-walled carbon nanotubes (MWNTs) (PU-g-MWNTs) containing different hard segments (hexamethylene diisocyanate, HDI, and methylenediphnyl 4,4′-diisocyanate, MDI) were synthesized to fabricate an electro-conducting nanocomposite. The PU conducting nanocomposites were obtained using a simple blending method. PU-g-MWNTs can improve the interfacial compatibility between the MWNTs and PU matrix. The HDI-based PU nanocomposite showed enhanced dispersibility of the functionalized MWNTs than the MDI-based nanocomposite. The difference in dispersity was related to its electrical conductivity. The critical concentration of the MDI-based nanocomposite was lower than the HDI-based nanocomposite because less dispersed and more aggregated MWNTs partially formed a conducting path at a lower concentration. The critical exponent of the HDI-based nanocomposite revealed that the better dispersed MWNTs exhibited enhanced electrical conductivity, compared to the MDI-based nanocomposite, as the filler concentration was increased.     

Polypyrrole coated carbon nanotubes: Synthesis,characterization, and enhanced electrical properties

We describe a simple approach to the synthesis of MWNT/polypyrrole nanotubes by the in situ chemical polymerization of pyrrole on the carbon nanotubes using ferric chloride as an oxidant. The effects of pyrrole concentration on the coating and properties of the resulting complex nanotubes were studied by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and thermal gravimetric analysis. The coated PPy layers could be controlled easily by adjusting a feed ratio of pyrrole to MWNTs. FT-IR results suggested an existence of interaction between the –COOH groups of chemically modified MWNTs and NH groups of the PPy. SEM and TEM studies indicated that each individual MWNT could be coated with PPy. The resultant nanotubes enhanced electrical conductivity compared to PPy and MWNT which was strongly influenced by the feed ratio of pyrrole to MWNTs.     

Synthesis and properties of multi-walled carbon nanotubes coated with inorganic nanoparticles

Rare earth fluoride EuF3 and TbF3 were coated on the multi-walled carbon nanotubes (MWNTs) via the intermediate of noncovalent hydrophobic interactions of the MWNTs surface with sodium dodecyl sulfate (SDS).They were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The nanoparticle sizes of metal fluorides and sulfides on MWNTs are less than 20 nm. The photo physical properties of the composites were investigated, which indicated the composites exhibited the optical transitions within the 4f shell of the rare earth ions.     

The electrochemical hydrogen storage of CNTs synthesized by CVD using LaNi5 alloy particles as catalyst and treated with different temperature in nitrogen

The multi-wall carbon nanotubes (MWNTs) were synthesized by chemical vapor deposition (CVD) using LaNi₅ alloy particles as catalyst. The effect of 40–60 nm MWNTs treated with different temperature in nitrogen on the electrochemical properties of CNTs–Ni electrode were investigated. Three-electrode system was introduced for testing electrochemical hydrogen storage of the electrode. The CNTs–Ni electrodes were used as the working electrode, which were prepared by mixing MWNTs and Ni powder in a weight ratio of 1:10 (MWNTs:Ni). Ni(OH)₂/NiOOH worked as the counter electrode and Hg/HgO as the reference electrode. A 6 mol/L KOH solution acted as the electrolyte. MWNTs treated with different temperature in nitrogen ambient represented a great discrepancy in the electrochemical hydrogen storage capability under the same testing condition. The CNTs–Ni electrodes with 40–60 nm diameter CNTs which were treated in a temperature of 800 °C in nitrogen has the best electrochemical hydrogen storage capacity of 588.1 mAh/g and a corresponding discharging plateau voltage of 1.18 V. From 500 to 800 °C, the higher temperature the MWNTs treated, the better the electrochemical hydrogen storage property of them is. This shows that the temperature of treatment is an important factor that influences electrochemical hydrogen storage performance of MWNTs.     

多壁碳纳米管载镍对镁基合金储氢性能影响

采用化学法制备多壁碳纳米管载镍催化剂(Ni/MWNTs),并将其加入到镁粉中,结合氢化燃烧合成(HydridingCombustionSynthesis,HCS)和机械球磨(MechanicalMilling,MM),即HCS+MM复合技术制备Mg85-Nix/MWNTs15-x(x代表质量百分数,x=3,6,9,12)合金。通过X射线衍射仪、透射电子显微镜、扫描电镜以及气体反应控制器研究了材料的晶体结构、微观形貌和吸放氢性能。结果表明:Mg85-Ni9/MWNTs6合金具有最佳综合吸放氢性能,其在373K,吸氢量达到5.68%(质量分数,下同),且在100s内就基本达到饱和吸氢量;在523K,1800s内的放氢量达到4.31%。Ni/MWNTs催化剂的添加,不但起到催化的作用,而且MWNTs具有优异的纳米限制作用,使得催化剂的粒径限制在纳米级,有利于限制产物中Mg2NiH4颗粒的长大。另外Ni与MWNTs存在协同催化作用,当它们达到一定比例时,对合金的吸放氢促进作用达到最优化,明显改善了合金的吸放氢性能。     

Fabrication of Pt nanoparticles decorated PPy–MWNTs composites and their electrocatalytic activity for methanol oxidation

Here we report the synthesis and characterization of a catalyst material constituted of Pt, polypyrrole (PPy) and multi-walled carbon nanotubes (MWNTs). The catalyst supports (PPy–MWNTs nanocomposites) were synthesized via in situ chemical polymerization in advance, in which MWNTs were regarded as the matrix material. The supports were characterized by SEM & TEM, elemental analysis, XRD, FTIR and conductivity measurements. Then the catalysts were synthesized by a chemical reduction using sodium borohydride (NaBH₄) as reducing agent and acetic acid buffer (pH = 4) containing trace K₂C₂O₄ as reaction media. FTIR spectra showed that there existed relations between PPy and MWNTs during in situ polymerization. SEM and TEM micrographs of the catalyst samples exhibited that the existence of PPy layer which was evenly wrapped on the surface of MWNTs resulted in significant improvement in helping Pt particles well dispersed. XRD results showed that higher Pt(1 1 1) content in the catalyst deposited on PPy–MWNTs supports than that on MWNTs. The cyclic voltammetry (CV) tests of methanol electrocatalytic oxidation demonstrated that the electrode modified by Pt/PPy–MWNTs ternary composite catalyst showed higher catalytic stability than Pt/MWNTs binary catalyst, due to the synergic interaction between Pt and the carrier.     

Preparation and magnetic property of multi-walled carbon nanotube/a-Fe2O3 composites

In order to attain new functional nanomaterials with good magnetic property, multi-walled carbon nanotubes/hematite (MWNTs/α-Fe₂O₃) composites were synthesized using the co-deposition method. MWNTs/α-Fe₂O₃ composites were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM), Raman spectroscopy and vibrating sample magnetometry (VSM). The experimental results show that the structure and magnetic properties of the MWNTs/α-Fe₂O₃ composites are related to the heat treatment temperature. MWNTs are modified by α-Fe₂O₃ nano-particles and α-Fe₂O₃ nanorods with a diameter of 10?50 nm after being treated at 450 °C. When the heat treatment temperature exceeds 600 °C, MWNTs are only modified by Fe₃O₄ particles. Furthermore, the MWNTs composites treated at 450 °C and 600 °C have good magnetic behaviour.     

Mechanical properties of hard Cr-MWNT composite coatings

Chromium-multiwalled carbon nanotubes (Cr-MWNT) composite coatings are electrodeposited from “environmentally acceptable” trivalent Cr electrolytes containing MWNTs under ultrasonic agitation. The structures, hardness and tribological behaviors are investigated using the transmission electron microscope (TEM), field-emission scanning electron microscope (FE-SEM), Vickers hardness indenter, tribology tester and three-dimensional profile tester, respectively. Results show that MWNTs are dispersed evenly in Cr matrix. The introduction of MWNTs obviously improved the hardness, toughness and tribological performance of Cr coatings.     

核壳型碳微球和碳纳米管的制备及其阻燃性能

为改善碳微球(CMSs)/碳纳米管(MWNTs)与聚对苯二甲酸乙二醇酯(PET)基体相容性,采用原位聚合法对CMSs和MWNTs分别进行表面修饰,制成核壳型结构的PET@CMSs(PCMSs)和PET@MWNTs(PMWNTs),并通过熔融共混法制备了PCMSs/PMWNTs/PET复合材料,对其阻燃性能进行探讨。使用TEM、SEM、FTIR、TGA、CONE等测试手段,表征了PCMSs与PMWNTs的结构及与PET基体的相容性,并测试了PCMSs/PMWNTs/PET的力学性能、阻燃性能、热稳定性和燃烧行为等。结果表明,与修饰前的CMSs/MWNTs相比,PCMSs/PMWNTs与PET基体具有更好的分散相容性,在PCMSs\PMWNTs添加的质量分数为1%,PCMSs与PMWNTs的质量比为1∶2时,PCMSs/PMWNTs/PET比CMSs/MWNTs/PET的抗拉强度提高的最大,可达26.1%;与纯PET、CMSs/MWNTs/PET相比,PCMSs/PMWNTs作为阻燃材料添加到PET中,具有较好的热稳定性、且有效延长了PET的点燃时间、增大FPI指数,从而降低火灾危险性,阻燃效果较好,其LOI值为28.1%,熔滴数为3 d/min,UL-94阻燃级别可达到V-0级。