纳米SiO2改性BOZ/BMI/BADCy共聚物的制备及性能研究

研究了纳米SiO2含量对苯并恶嗪树脂(BOZ)/双马来酰亚胺(BMI)/双酚A型氰酸酯(BADCy)/纳米SiO2复合材料力学性能、热性能和吸水性能的影响。结果表明,当纳米SiO2质量分数为3%时,BOZ/BMI/BADCy/纳米SiO2复合材料具有较高的强度和良好的韧性,其缺口冲击强度和弯曲强度比BOZ/BMI/BADCy共聚物分别提高了11.6%和8.5%;同时,纳米SiO2质量分数为3%时BOZ/BMI/BADCy/纳米SiO2复合材料具有优异的耐热性,其初始热分解温度和最大热分解温度分别为343.2℃和430.3℃。     

双马来酰亚胺/苯并噁嗪/石墨烯共聚物固化动力学及力学性能的研究

通过差示扫描量热法对双马来酰亚胺/苯并噁嗪/石墨烯（BMI /BOZ/GNS）共聚物进行了动力学研究。通过Kissinger法和Ozawa法求得了BMI /BOZ/GNS共聚物的固化动力学参数,进而研究了GNS对BMI /BOZ共聚物力学性能的影响。结果表明,随着GNS含量的增加,BMI /BOZ/GNS树脂体系的拉伸性能先增加后减小;当GNS含量为0.15 %（质量分数,下同）时,BMI /BOZ/GNS树脂体系的力学性能最优。     

环氧树脂/石墨烯复合材料的制备及其性能

采用改进的氧化、超声剥离法制备了氧化石墨烯(GO),采用水合肼对GO进行化学还原,制得石墨烯(GNS),利用溶剂混合法制备了环氧树脂(EP)/GNS复合材料,对天然石墨,GO,GNS的微观形貌与结构进行了表征,并研究了EP/GNS复合材料的力学性能、电学性能和热性能。结果表明:GNS呈片层多孔结构,有少量含氧基团;当w(GNS)为1.0%时,EP/GNS复合材料力学性能最佳(拉伸强度为79.5 MPa,断裂拉伸应变为3.02%,邵氏硬度达97.2);当w(GNS)为1.5%时,EP/GNS复合材料电导率达4.17×10~(-2) S/m,较EP提高了8个数量级,玻璃化转变温度较EP提高了8.3℃。     

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 ℃。     

改性EP/S–GF单向复合材料缠绕成型工艺及性能

以4,4’-二氨基二苯甲烷、苯酚和甲醛为原料合成二胺型苯并恶嗪(MDA–BOZ),并用其改性环氧树脂(EP)。采用湿法缠绕成型方法制备单向高强玻璃纤维(S–GF)增强改性EP基复合材料。用T–β外推法和凝胶化时间法确定了复合材料的成型工艺,并测试了其在室温和高温下的拉伸强度、弯曲强度、层间剪切强度等力学性能。与EP/4,4’–二氨基二苯砜(DDS)/S–GF复合材料相比,EP/MDA–BOZ/DDS/S–GF复合材料综合力学性能有较大提高。EP/MDA–BOZ/DDS/S–GF复合材料室温弯曲强度达1 428.3 MPa,层间剪切强度达79.92 MPa,纵向拉伸强度1 134.1 MPa,拉伸弹性模量为40.15 GPa。复合材料在100℃时,弯曲强度保持率为78.95%,层间剪切强度保持率为81.06%。扫描电子显微镜分析发现,改性树脂与玻璃纤维界面粘结性较好。     

EP/GNs/MWCNTs复合材料的导热性能

以多壁碳纳米管(MWCNTs)和石墨烯纳米微片(GNs)为导热填料,环氧树脂(EP)为基体采用溶剂和超声分散法,制备了EP/GNs/MWCNTs导热复合材料,并与EP/MWCNTs及EP/GNs复合材料的导热性能进行了对比。采用透射电子显微镜观察其微观结构,采用Hot Disk热导率测试仪测试其导热性能,采用差示扫描量热法和热重分析仪测试其耐热性及热稳定性。结果表明,MWCNTs和GNs共同作为EP导热填料时,相比于单组分填料(MWCNTs或GNs)更易形成导热网络;EP的热导率、玻璃化转变温度(Tg)和热分解温度均随着MWCNTs或GNs含量的增加而提高,其中,GNs更有利于提高EP的热导率和热分解温度,MWCNTs更有利于提高EP的Tg。在相同的导热填料含量下,相对于其中的任一单一填料,MWCNTs/GNs共同作用时,对热导率的提高有更显著的效果,且随着其中GNs比例的增加,热导率逐渐增大。当GNs和MWCNTs的体积分数分别为0.6%和0.4%时,EP/GNs/MWCNTs复合材料的热导率、Tg和起始分解温度分别为0.565 W/(m·K),152℃和316℃,分别比纯EP提高了132.5%,34.5%和8.2%。     

三乙烯四胺固化有机蒙脱土/环氧树脂复合体系的研究

以三乙烯四胺作为EP(环氧树脂)的常温固化剂制备EP/OMMT(有机蒙脱土)/三乙烯四胺纳米复合材料。采用X射线衍射(XRD)法,差示扫描量热(DSC)法等手段研究了不同配方对EP/OMMT/三乙烯四胺固化体系的凝胶时间、力学性能、热性能及OMMT的插层剥离行为等影响。结果表明:对EP/OMMT/三乙烯四胺复合材料而言,90~120℃固化体系的OMMT剥离与插层效果优于室温固化体系;当固化温度为120℃时,EP/OMMT/三乙烯四胺复合材料的耐湿热性能和弯曲强度均优于常温固化体系;EP/OMMT/三乙烯四胺复合材料经常温固化24 h后,其冲击强度比纯EP体系提高了7%~12%。     

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。     

不同酸酐对环氧树脂固化体系的影响

以Amicure HAPI(改性咪唑)为促进剂、T-80(改性酸酐)和TM-80(酸酐)为固化剂,探讨了不同酸酐固化剂对EP(环氧树脂)体系力学性能和耐热性的影响;然后以最佳性能的EP为基体树脂、玻璃纤维为增强材料,采用手糊法制备了复合材料层压板。研究结果表明:两种酸酐固化体系均具有良好的力学性能,并且T-80/EP固化体系的拉伸强度、弯曲强度和冲击强度均得到提升,但拉伸模量和弯曲模量基本不变;两种酸酐固化体系均具有良好的耐热性,并且T-80/EP固化体系的耐热性基本不受影响;以EP/T-80体系制得的层压板具有相对最好的综合力学性能和耐热性。     

DDS固化EP/MMT纳米复合材料性能研究

以4,4′-二氨基二苯砜(DDS)为固化剂,制备出一种剥离型MMT/EP(蒙脱土/环氧树脂)纳米复合材料。采用红外光谱(FT-IR)法、X射线衍射(XRD)法和动态力学分析(DMA)法等对复合材料的微观结构、插层剥离行为、热性能和力学性能等进行了研究。结果表明:MMT对EP分子结构无影响,有利于EP结构和性能的设计,也便于确定其固化工艺。在无促进剂的情况下,当体系中引入5%MMT(相对于EP质量而言)时,复合材料的干态热变形温度、玻璃化转变温度(Tg)、冲击强度和拉伸强度分别提高了39℃、21℃、27.30%和10.50%;适量的MMT能有效提高纳米复合材料的耐湿热性能。     

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.     

Compact Swelling in Bi1.4Pb0.6Sr2Ca2Cu3.6Oy During the Formation of High-Tc Superconducting Phase

Compact swelling in Pb-doped Bi-Sr-Ca-Cu-O superconductor has been studied by observing the effects of the size of calcined powders, volatilization of materials, and sintering of high- T _c (2223) powders. The bulk density increases at the early stage of sintering, for about 20 h, and then decreases. Densification occurs when the low- T _c (2212) phase and a liquid phase exist, whereas dedensification occurs with the formation of the 2223 phase regardless of the presence of the liquid. Gas evolution from specimens does not appear to be responsible for compact swelling. Compact swelling is explained by anisotropic growth of thin, platelike 2223 grains in random orientation. When 2223 grains grow in a preferred direction, compact swelling is suppressed.