纳米Si3N4与玻璃纤维混杂增强PA6复合材料的摩擦学性能研究

以纳米Si3N4和玻璃纤维(GF)混杂增强尼龙6(PA6)复合材料,对PA6复合材料的摩擦学性能进行了实验研究。结果表明,纳米Si3N4和GF混杂可以显著改善PA6复合材料的摩擦学性能,以质量分数3%Si3N4和20%GF混杂填料的耐磨减摩性最好。扫描电子显微镜观察发现,纯PA6的磨损机理以粘着和犁削为主。在PA6/GF复合材料中纳米Si3N4含量较低时,复合材料的磨损机理主要表现为不同程度的粘着磨损,但当复合材料中纳米Si3N4含量较高时,复合材料的磨损机理主要表现为不同程度的粘着磨损和磨粒磨损。     

纳米粒子混合填充聚四氟乙烯复合材料的性能

采用模压成型法制备纳米Si3N4或SiC与纳米Al2O3混合填充的聚四氟乙烯(PTFE)复合材料,研究不同质量分数的纳米Si3N4或SiC与5%纳米Al2O3混合填充对PTFE复合材料力学与耐磨性能的影响,利用扫描电子显微镜(SEM)观察复合材料拉伸断面的微观结构,探讨其增强机理.结果表明:纳米SiN4或SiC与Al2O3混合填料均能使PTFE复合材料的硬度和耐磨性提高,且填充Si3N4/Al2O3的PTFE复合材料的硬度、拉伸性能、冲击强度和耐磨性均优于填充SiC/Al2O3的,其中5%Si3N4与Al2O3混合填充的PTFE复合材料有较好的综合性能.微观分析表明:Si3N4/Al2O3在PTFE基体中分散性较好,说明Si3N4与Al2O3具有较好的协同作用.     

用硅灰合成无碳Si3N4/SiC纳米粉末

用机械与同步热激活法首次从废硅灰中合成无碳Si3N4/SiC纳米粉末。通过这种新方法可在1 465℃形成晶粒尺寸小至45nm的Si3N4/SiC纳米粉末。为了合成无碳Si3N4/SiC纳米粉末,研究了两种不同方法移除纳米粉末中游离碳的有效性。这两种方法分别使用氢气和空气。研究发现,虽然使用氢气时Si3N4和SiC是稳定的,但是这种方法不是很有效。相比之下,使用空气移除游离碳是有效的。游离碳除去后立即停止使用空气,Si3N4/SiC纳米粉末也会有少量被氧化。本文提供了明确的途径将硅灰有效合成无碳Si3N4/SiC纳米粉末。     

Si3N4/SiC/环氧树脂纳米导热复合材料的制备

以硅烷偶联剂KH-560改性的微米氮化硅/纳米碳化硅晶须(Si3N4/SiCw)为导热填料,浇注制备Si3N4/SiC/环氧树脂纳米导热复合材料.研究了环氧树脂种类、Si3N4/SiCw用量、复配比及表面改性对环氧树脂导热、力学和介电性能的影响.结果表明,环氧树脂的热导率随Si3N4/SiCw用量的增加而增大,当改性Si3N4/SiCw用量为50％[m(Si3N4) /m(SiCw)]=3/1时,环氧树脂的热导率为0.98 W/(m· K);复合材料的介电常数随Si3N4/SiCw用量的增加而增大,而力学性能则先增加后降低.     

响应曲面法优化有机硅改性环氧树脂基耐磨涂料配方

研制了一种有机硅改性环氧树脂双组分耐磨涂料,其中A组分由自制的纳米TiO2/微米SiC复合颗粒(TiO2/SiC)、MoS2、γ-缩水甘油醚氧丙基硅烷(KH-560)和有机硅改性环氧树脂组成,固化剂聚酰胺作为B组分.以耐磨失质量比为指标,利用响应曲面法优化了涂料的制备工艺参数,结果表明:涂料优化的工艺参数中填料所占质量比例为70.60%,偶联剂0.80%,MoS21.40%,此时最低磨损失质量比可至0.42%.通过SEM观察涂料磨损形貌并初步探索其磨损机理,研究认为:添加复合粒子的耐磨涂料磨损机理呈粉状磨粒磨损特性.     

聚硫橡胶改性环氧/环硫树脂复合防腐蚀涂料的制备

以环氧/环硫树脂为基料,聚硫橡胶为增韧剂,聚苯胺(PANI)为防腐蚀成分,改性纳米Ca CO3和纳米Si O2作为无机填料,制备了聚硫橡胶改性环氧/环硫树脂复合防腐蚀涂料。研究了不同聚硫橡胶和无机填料用量对涂层机械性能和防腐蚀性能的影响,并通过热失质量(TGA)对产物热稳定性能进行分析。结果表明:添加环硫树脂(50%,相对于成膜物质的质量百分比,下同)提高了漆膜附着力,聚硫橡胶(10%)提高了漆膜柔韧性,而加入PANI(5%)后提高了漆膜防腐蚀性能,改性纳米Ca CO3(3%)或纳米Si O2(3%)对漆膜的力学性能和热稳定性均有所提升。     

SiC/h-BN复合涂层的制备及其性能

将碳化硅Si C和六方氮化硼(h-BN)、成膜剂环氧树脂E-44和107胶与固化剂混合后涂覆于Q 235基体表面制备了SiC/h-BN复合涂层,并通过附着力、力学测试、中性盐雾试验、抗老化实验等手段研究了SiC和h-BN质量比对涂层性能的影响。结果表明:Si C和h-BN填料能提高环氧树脂涂层的性能,当填料为环氧树脂质量的2%且SiC和h-BN的质量比为3∶1时,复合涂层的性能最佳,附着力为0级,耐中性盐雾和耐老化性能较好。     

CE/EP/纳米SiC复合材料研究

采用纳米SiC和环氧树脂(EP)对双酚A型氰酸酯树脂(CE)进行改性。研究了不同含量的纳米SiC对CE/EP/纳米SiC复合体系反应性及CE/EP/纳米SiC复合材料力学性能的影响,采用透射电子显微镜表征了材料的微观形貌,利用差示扫描量热法研究了固化树脂的热性能。结果表明,纳米SiC对CE/EP/纳米SiC复合体系具有明显的催化作用,并且能使复合材料的冲击强度提高123.62%,弯曲强度提高140.29%,有效发挥其增强增韧作用,还能很好地保持复合材料的耐热性能。     

纳米耐高温绝热涂料的研制

以改性六钛酸钾晶须(PTW)、纳米Si O2气凝胶、超细空心陶瓷微珠、纳米Ti O2和Al2O3为主要隔热填料,以耐高温有机硅树脂乳液和丙烯酸乳液为基料,在多种功能助剂的配合下制备成纳米耐高温绝热涂料。涂层具有薄层、绝热、防水、抗裂、防腐、隔音、耐高温、耐候等特性。     

耐高温PAI/EP涂层的制备及摩擦学性能研究

通过溶剂法对环氧树脂(EP)和聚酰胺酰亚胺(PAI)进行共混,加入增韧剂、润滑剂、固化剂及其他助剂,制备出性能优异的耐高温耐磨涂层材料。采用热失重分析仪(TGA)、环块型摩擦磨损试验机(MRH-3G)测试了复合涂层材料的耐高温性能、摩擦磨损性能。结果表明,当PAI含量为10%时,涂层材料的降解温度可达到273℃;润滑剂总量为25%,石墨与二硫化钼(MoS_2)配比为3∶2时,其摩擦磨损性能最佳。采用扫描电子显微镜(SEM)表征了涂层磨损表面的微观形貌。结果表明,润滑剂添加过少,复合涂层表面磨损严重,出现犁沟且变形;添加过多会产生轻微裂纹,润滑膜翘起甚至脱落。采用能谱(EDS)分析了涂层表面磨损前后的元素成分,结果表明润滑剂均匀分散在基体树脂中,形成自润滑膜。     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.