环氧树脂/纳米SiO_2复合材料的制备

制备了环氧树脂(EP)/纳米SiO2复合材料,研究了纳米SiO2用量对复合材料结构和力学性能的影响,采用扫描电子显微镜观察了复合材料的断面形貌,分析了纳米SiO2的增韧机理。添加适量的纳米SiO2可显著提高EP的力学性能,添加6 phr纳米SiO2时,EP/纳米SiO2复合材料的力学性能最佳,拉伸剪切强度、弯曲强度、悬臂梁缺口冲击强度分别为13.8 MPa,86.1 MPa,11.6 kJ/m2;适量的纳米SiO2能改善EP的内部结构,具有明显的增韧补强作用。     

纳米SiO_2对聚丙烯/环氧树脂共混物性能的影响

采用熔融共混法制备了聚丙烯(PP)/环氧树脂(EP)共混物,研究了纳米SiO2对共混物性能的影响。结果表明:与纯PP相比,PP/EP共混物的冲击强度、断裂伸长率及黏度降低,弯曲模量增大;在PP/EP共混物中加入纳米SiO2后,共混物弯曲模量和冲击强度明显提高;将硅烷偶联剂KH550改性的纳米SiO2(SiO2-KH550)添加到共混物中,在EP为17%、SiO2-KH550为7%时,共混物的弯曲模量比纯PP提高了64%;EP降低了PP的结晶温度。     

碳纳米管/石墨烯杂化材料改性环氧树脂研究

采用物理法和化学多步法合成了碳纳米管/石墨烯杂化材料,通过红外光谱表征证明杂化材料的成功合成,通过沉淀实验表明化学多步法合成的碳杂化材料具有良好的分散性和分散稳定性。将碳纳米杂化材料按照质量分数0.3%添加到环氧树脂(EP)中制备复合材料,对复合材料的拉伸强度和断裂韧性进行表征,并通过扫描电子显微镜对复合材料的断面进行表征。结果表明,碳纳米管/石墨烯杂化材料对EP的增强增韧效果较好,尤其是化学多步法合成的杂化材料改性EP复合材料,其拉伸强度最大,曲线积分面积最大,弹性模量最小,韧性最好。这可能要归因于化学多步法合成的杂化材料具有更为稳定的三维结构,可以更好地承担和转移外部载荷。     

环氧树脂/POSS杂化材料力学性能和耐热性研究

以自行合成的环氧基倍半硅氧烷（POSS）为改性剂,分别对环氧树脂139S/六氢苯酐和环氧树脂BE 188EL/六氢苯酐进行改性,制备环氧树脂/POSS杂化材料。力学性能分析结果表明,两种杂化材料的冲击强度和弯曲强度都有明显的提高,冲击强度分别提高了57.45 %和32.26 %,弯曲强度分别提高了9.23 %和5.07 %。热性能分析结果表明,两种杂化材料在高温时的热残留量都有所提高,分别提高了50.19 %和20.16 %。两种杂化材料的热膨胀系数也得到了降低,即热稳定性得到了提高。     

纳米SiO_2/环氧树脂灌封材料的制备和力学性能研究

以经偶联剂处理的纳米SiO2作为增强材料,制备了纳米SiO2/环氧树脂(EP)灌封材料。研究了不同纳米SiO2含量对灌封材料力学性能的影响。结果表明:当纳米SiO2/EP灌封材料中w(纳米SiO2)=4%时,灌封材料的冲击强度和弯曲强度达到最大值,并且分别比纯EP固化物提高了117%和109%;经硅烷偶联剂处理的纳米SiO2,在EP中的分散性得到有效改善,从而对纳米SiO2/EP灌封材料具有较好的增强、增韧效果。     

EP/CF/纳米SiO2复合材料激光作用下的性能研究

在环氧树脂(EP)中添加纳米SiO2空心微球,制备添加不同比例纳米SiO2的EP浇注体和EP/碳纤维(CF)复合材料.经热重(TG)分析仪测试,发现添加纳米SiO2后EP的耐热性能明显提高,其中纳米SiO2质量分数为10%时其耐热性能最好;对有、无纳米SiO2的EP浇注体和EP/CF复合材料层板进行强功率激光辐照试验,结果表明,添加纳米SiO2空心微球能明显提高复合材料在激光作用下的抗烧蚀和隔热性能.     

纳米ZnO、Vinyl–POSS改性环氧树脂的抗紫外和增韧性能

将纳米氧化锌(ZnO)、八乙烯基八硅倍半氧烷(Vinyl–POSS)作为添加材料对环氧树脂(EP)进行改性,提高其抗紫外能力和力学强度。讨论了纳米ZnO和Vinyl–POSS对EP复合材料性能的影响,使用紫外可见分光光度计(UV–vis)、场发射扫描电子显微镜(FESEM)、热重分析(TGA)和四点弯曲测试等对其进行表征。结果表明:当m(纳米ZnO):m(EP)=2.0%时,EP复合材料的紫外吸收效果最佳;当m(Vinyl–POSS):m(EP)=1.0%时,EP复合材料的弯曲强度和冲击强度分别提升了26.8%和32.2%;加入热稳定性相对较弱的Vinyl–POSS对EP复合材料进行改善力学性能的同时,并未对其整体的热稳定性造成影响。     

纳米SiO_2/聚氨酯弹性体协同增韧增强环氧树脂的研究

采用力学性能测试,扫描电子显微镜(SEM),透射电子显微(TEM)及动态力学性能分析(DMA)研究了纳米SiO2以及聚氨酯弹性体(PUR)对环氧树脂(EP)的改性效果。结果表明,纳米SiO2质量分数0.3%时可同时增韧、增强EP。纳米SiO2与PUR有协同增韧增强EP的作用,纳米SiO2质量分数0.3%,PUR质量分数20%时,纳米SiO2/PUR/EP三元复合材料的冲击强度比纯EP,纳米SiO2/EP及PUR/EP体系分别提高110%,11%和7%;弯曲强度分别相应提高21%,5%和15%。改性体系的断口形貌呈现明显的韧性断裂,表明纳米SiO2颗粒较均匀分布在基体中。三元复合材料的储能模量和玻璃化转变温度(T g)高于PUR/EP二元体系,损耗峰明显宽化。     

双马来酰亚胺/环氧树脂/纳米SiO2复合材料的制备与性能研究

研究了纳米二氧化硅（SiO2）的含量对双马来酰亚胺（BMI）/环氧树脂(EP)/2,2′二烯丙基双酚A(DBA)/纳米SiO2复合材料的耐热性能、力学性能和吸水性能的影响。结果表明,当纳米SiO2的含量为2.0 %(质量分数,下同)时,BMI/EP/DBA/纳米SiO2复合材料具有较高的强度和良好的韧性,其拉伸强度、弯曲强度和缺口冲击强度比BMI/EP/DBA复合材料分别提高了22.8 %、39.0 %和37.8 %;同时,纳米SiO2含量为 2.0 %时,BMI/EP/DBA/纳米SiO2复合材料具有优异的耐热性,其玻璃化转变温度、初始热分解温度和最大热分解温度分别为204、 410、451 ℃。     

八环氧基笼型倍半硅氧烷/EP杂化材料的制备及性能研究

以三乙烯四胺(TETA)为固化剂,采用共混法制备八环氧基笼型倍半硅氧烷(G-POSS)/环氧树脂(EP)杂化材料。研究了环氧基POSS含量对杂化材料的固化反应、介电性能、力学性能及热性能等影响,并对杂化材料的微观相态结构进行了表征和分析。结果表明,G-POSS的引入提高了EP的反应活性,制备的杂化材料透明性良好,力学性能、介电性等都有所提高;且当m(G-POSS)m∶(EP)=20 1∶00时,杂化材料的介电性能、力学强度和刚性提高较为明显,且其断面形貌呈韧性断裂。其拉伸强度为67.8 MPa、断裂伸长率为3.44%、弯曲强度为116.7 MPa,与纯EP相比,分别提高了83.20%、320.13%、49.17%。     

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.     

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.     

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.     

The System Si3N4-SiO2-Y2O3

Subsolidus phase relations were established in the system Si₃N₄-SiO₂-Y₂O₃. Four ternary compounds were confirmed, with compositions of Y₄Si₂O₇N₂, Y₂Si₃O₃N₄, YSiO₂N, and Y₁₀(SiO₄)₆N₂. The eutectic in the triangle Si₃N₄-Y₂Si₂O₇-Y₁₀(SiO₄)₆N₂ melts at 1500°C and that in the triangle Si₂N₂O-SiO₂-Y₂Si₂O₇ at 1550°C. The eutectic temperature of the Si₃N₄-Y₂Si₂O₇ join was ∼ 1520°C.     

Phase Relations in the Pseudobinary System Na2TiSi4O11-Na2Ti2Si2O9

The quenching technique was used to study subliquidus and subsolidus phase relations in the pseudobinary system Na₂ Ti₂Si₂ O₁₁-Na₂ Ti₂ Si₂ O₉. Both narsarukite (Na₂TiSi₄O₁₁) and lorenzenite (Na₂Ti₂Si₂O₉) melt incongruently. Narsarsukite melts at 911°±°C to SiO₂+liquid, with the liquidus at 1016°C. Lorenzenite melts at 910°±5°C to Na₂ Ti₆ O₁₃+liquid; Na₂ Ti₆ O₁₃ reacts with liquid to form TiO₂ and is thus consumed by 985°±5°C. The liquidus occurs at 1252°C.