偶联剂Si69改性白炭黑对NR/SSBR并用胶性能的影响

试验研究偶联剂Si69用量和白炭黑改性方法对白炭黑填充NR/SSBR并用胶性能的影响.结果表明,当采用直接加入法改性白炭黑时,随着偶联剂Si69用量的增大,Payne效应减弱,NR/SSBR并用胶的t10延长,t90缩短,硫化胶的物理性能提高,偶联剂Si69用量以4 5份为宜.与直接加入法改性白炭黑填充并用胶相比,预处理法改性白炭黑填充并用胶的Payne效应减弱,拉伸强度和撕裂强度增大;高温静置处理法改性白炭黑填充并用胶的定伸应力、拉伸强度和损耗模量增大.     

混炼工艺对偶联剂Si69改性白炭黑填充丁苯橡胶/稀土顺丁橡胶并用胶性能的影响

研究混炼工艺对偶联剂Si69改性白炭黑填充溶聚丁苯橡胶/稀土顺丁橡胶并用胶性能的影响。结果表明,当混炼工艺中有150℃的保温平台且白炭黑为一次投料时,白炭黑在橡胶基体中的分散性较好,白炭黑形成的填料网络得到了抑制,相应硫化胶具有较好的物理性能和耐磨性能。     

改性白炭黑补强NR/TPI的性能研究

本文选用双-(γ-三乙氧基硅基丙基)四硫化物(Si-69)为改性剂,利用球磨法制备了接枝改性白炭黑。利用热失重法(TG)分析了改性剂用量和改性时间等因素对接枝率的影响。将改性白炭黑用于天然橡胶(NR)/ 反式聚异戊二烯(TPI)的补强中,比较了未改性白炭黑和改性白炭黑对胶料的硫化性能、物理机械性能和动态性能等的影响。结果表明,在0~12份范围内,改性剂用量越大,白炭黑接枝率越高,但综合物理机械性能最佳值则出现在改性剂用量为10份时。在15~45 min范围内,改性时间对白炭黑接枝率影响不明显,但当改性时间为45 min时,综合物理机械性能最佳。白炭黑经接枝改性后改善了其在橡胶基体中的分散性和与橡胶基体的相容性,添加改性白炭黑胶料的抗湿滑性能、滚动阻力和动态生热性能均有改善。     

排胶温度和时间对炭黑/白炭黑/偶联剂Si69补强体系硅烷化反应程度和胶料性能的影响

研究排胶温度和时间对炭黑/白炭黑/偶联剂Si69补强体系中白炭黑硅烷化反应程度和胶料性能的影响。结果表明,当排胶温度为155 ℃、排胶时间为280～320 s时,炭黑/白炭黑/偶联剂Si69补强体系混炼胶中白炭黑的硅烷化反应程度最高,填料分散性较好,胶料的综合性能最佳。     

白炭黑改性剂对溶聚丁苯橡胶性能的影响

将偶联剂Si69和KH550、活性剂PEG4000和DPG用作白炭黑改性剂,研究其对白炭黑填充溶聚丁苯橡胶(SSBR)性能的影响。结果表明:改性剂种类和用量对硫化胶性能有较大影响,Si69,KH550,PEG4000和DPG的最佳用量分别为4,8,4和6份;在最佳改性剂用量下,与未改性白炭黑胶料相比,改性白炭黑胶料的加工安全性好,硫化速率快,物理性能、耐磨性能和抗湿滑性能提高;在4种改性剂中,Si69和KH550改性白炭黑在橡胶中的分散性较好,胶料具有较高的物理性能、耐磨性能、抗湿滑性能及较低的滚动阻力。     

改性白炭黑-橡胶相互作用和非线性粘弹性研究

选用Si-69利用原位接枝法对白炭黑进行了表面改性并用于天然橡胶的补强,重点考察了不同填料用量下改性白炭黑-天然橡胶的相互作用和非线性粘弹性。结果表明,与未改性白炭黑相比,添加改性白炭黑的胶料结合胶量上升,填料-橡胶相互作用增强,填料在橡胶基体中的分散性更好。胶料应变软化和Payne效应随填料用量的上升而增强。当填料用量小于26份时,天然橡胶/改性白炭黑的应变软化大于天然橡胶/白炭黑的。超过26份后,情况反转。     

补强NBR硫化胶的性能预测

建立数学模型研究高耐磨炭黑/白炭黑和偶联剂用量对NBR胶料性能的影响.结果表明,白炭黑等量替代高耐磨炭黑时,随白炭黑用量增加,胶料的物理性能呈现出劣化趋势,偶联剂Si69对白炭黑的改性效果非常明显;建立的数学模型能较好地拟合高耐磨炭黑/白炭黑和偶联剂用量与胶料各项性能之间的关系.     

NR/改性气相法白炭黑复合材料的性能研究

在改性气相法自炭黑填充NR胶料中加入粘合剂RH，研究粘合剂RH用量对胶料性能的影响，并与偶联剂Si69／气相法白炭黑胶料进行对比。结果表明，粘合剂RH的加入明显改善了硫化胶的物理性能，拉伸强度提高10％以上；粘合剂RH用量为4份时，硫化胶的综合物理性能最佳；有机改性剂M2改性气相法白炭黑参与了橡胶的共硫化，使硫化胶的交联密度增大；偶联剂Si69对硫化胶物理性能的改善效果不及粘合剂RH。     

偶联剂Si69用量对白炭黑胶料性能的影响

研究偶联剂Si69用量对白炭黑胶料各项性能的影响。结果表明：随着偶联剂Si69用量的增大,混炼胶的门尼粘度减小,Payne效应降低,t90缩短;结合胶含量先迅速增大后略有下降,填料分散性提高;毛细管挤出胀大比增大,挤出表面变差;硫化胶的定伸应力增大,补强指数先增大后减小,偶联剂Si69用量为白炭黑用量的8%时补强指数最大;回弹值逐渐增大、压缩生热逐渐减小;磨耗指数先迅速增大后趋于稳定;60 ℃损耗因子最大值先迅速下降后上升,最终趋于稳定;偶联剂Si69用量为白炭黑用量的6%～8%时,胶料的综合性能最优。     

有机湿法改性白炭黑对天然橡胶复合材料性能的影响

分别采用双-[3-（三乙氧基硅）丙基]-四硫化物（偶联剂Si69）、离子液体1-丁基-3-甲基咪唑六氟磷酸盐（BMI）、离子液体1-烯丙基-3-甲基氯化咪唑（AMI）对白炭黑进行改性,制备改性白炭黑/天然橡胶（NR）复合材料。研究改性剂对改性白炭黑/NR复合材料的微观结构、硫化特性、物理性能和动态力学性能的影响。结果表明：改性白炭黑的粒径明显减小,其在橡胶基体中的分散性改善,与橡胶基体之间的相互作用增强;改性白炭黑/NR复合材料的硫化速率加快,物理性能明显提高;与偶联剂Si69相比,两种离子液体明显提高改性白炭黑/NR复合材料的硫化效率和物理性能;随着应变和频率的增大,白炭黑/NR复合材料的储能模量从大到小的填料顺序为AMI改性白炭黑、BMI改性白炭黑、偶联剂Si69改性白炭黑、未改性白炭黑;AMI改性白炭黑/NR复合材料的综合性能最好。     

Synthesis of dysprosium/Mn–Cu ferrite binary nanocomposite: Analysis of structural,morphological, dielectric,and optomagnetic properties

Manganese–copper ferrite (MCFO) and dysprosium (Dy)-doped manganese–copper ferrite nanocomposites (Mn_0.5Cu_0.5Dy_xFe_2−xO₄) (x = 0, 0.05, 0.10, and 0.15) were synthesized by sonochemical method. Crystal structure and the structural parameters of the MCFO were analyzed based on the doping concentration of Dy ion. It was observed that the average crystalline size of the synthesized nanocomposite decreases when the concentration of Dy increases. The existing spherical surface morphology of the MCFO and Dy-doped MCFO nanocomposites were obtained through scanning electron microscopy. In the UV spectrum, the pristine MCFO sample showed an absorbance peak at 743 nm whereas the absorbance values of Dy-doped ferrite nanocomposite considerably shifted (blue) toward a lower wavelength (231–222 nm). The dielectric parameters of all ferrite nanocomposites were studied in the frequency range of 100 Hz to 5 MHz. The dielectric spectrum revealed that dielectric constant and loss tangent decreased with increased doping concentration of Dy ion. The saturation magnetization also changed with Dy doping in MCFO. The impact of Dy on manganese–copper ferrite changed the optical, dielectric and magnetic properties of the prepared binary ferrite nanocomposite, which can be used for microwave-absorbing material applications.     

Fabrication of superhydrophobic TiO2 quadrangular nanorod film with self-cleaning,anti-icing properties

Superhydrophobic TiO₂ quadrangular nanorod film was fabricated by hydrothermal reaction and stearic acid modification. X-ray diffractometer and Fourier transform infrared spectrometer were employed to characterize the surface crystal structures and chemical compositions of the superhydrophobic TiO₂ film, respectively. The effects of the titanium source (titanium tetraisopropoxide (TTIP)) amount and reaction time on the morphology and wettability of the TiO₂ film were studied by scanning electron microscope and contact angle meter. The results show that the diameter of the TiO₂ quadrangular nanorods increases and then the water contact angle on modified TiO₂ film decreases with the increase of the reaction time and TTIP amount. Moreover, when the TTIP amount is 0.3?mL and solvent is 30?mL, the wetted state of the superhydrophobic TiO₂ film surface conforms to an improved Cassie model. Besides, the superhydrophobic TiO₂ film shows good low adhesion, self-cleaning and anti-icing properties. Particularly, the anti-icing property decreases with the increase of the reaction time and TTIP amount.     

A new precursor to lightweight porous Si–Al–O–B ceramics with enhanced microwave transmissivity

Nowadays, complicated preparation processes and harsh sintering conditions wave transparent ceramics limit its further development. To solve this problem, we explore a promising precursor by adopting a polymerization-pyrolysis method to prepare porous Si–Al–O–B ceramics at a mild sintering condition (1000 °C). The porous Si–Al–O–B ceramics exhibits enhanced wave transparency at 10–16 GHz with a low dielectric constant (<3), a low loss angle tangent value (<0.01), and simultaneously, a relative high flexible strength of 82 MPa. According to the results of the XRD and FTIR analysis, porous Al₄B₂O₉ crystallization dispersed in the amorphous SiO₂ matrix constructs the main phases of the products. The changes of Al and B elements are confirmed to have an effect on the phase compositions and micro structure of the composite ceramics, which obviously affect the mechanical and dielectric properties of the derived ceramics. The as-prepared porous Si–Al–O–B ceramics could be a potential candidate for next generation electronic window materials due to its low dielectric constant and loss angle tangent value, as well as high flexible strength.     

Structural,dielectric, and piezoelectric properties of Ce-doped Bi7Ti4.2Ta0.3W0.5O21 intergrowth ferroelectric ceramics

The Bi_7-xCe_xTi_4.2Ta_0.3W_0.5O₂₁ (BTTW-BITT-xCe, x = 0.05, 0.10, 0.15, 0.20) ceramics were studied as potential materials for high-temperature applications. The microstructure, dielectric, piezoelectric and ferroelectric properties of Ce doped BTTW-BITT samples were analyzed in detail. The results indicated that an appropriate amount of Ce ion doping could inhibit the growth of grains, suppress the relaxation peak, reduce high-temperature dielectric losses, and greatly improve the piezoelectric activities. The optimal ceramics was obtained at x = 0.15, which possessed a maximum piezoelectric constant of d₃₃ = 23.4 pC/N, a high Curie temperature of 713 °C, a loss value of 6% at 500 °C, and a favorable thermal stability of d₃₃ = 21.1 pC/N (90% of the initial value) at 500 °C. This result indicates that BTTW-BITT-0.15Ce has great potential for applications in the high temperature fields. In addition, XPS results showed that there were two Ce valences states, Ce³⁺ and Ce⁴⁺present in the BTTW-BITT-xCe ceramics.     

Enhanced dielectric and energy-storage properties in ZnO-doped 0.9(0.94Na0.5Bi0.5TiO3−0.06BaTiO3)−0.1NaNbO3 ceramics

[0.9(0.94Na_0.5Bi_0.5TiO₃?0.06BaTiO₃)?0.1NaNbO₃]-xZnO (NBT-BT-NN-xZnO, x=0, 0.5 wt%, 1.0 wt%, 1.5 wt%, and 2.0 wt%) ferroelectric ceramics were fabricated using a conventional solid-state reaction method. The effects of ZnO content on dielectric, energy-storage and discharge properties were systematically investigated. Dielectric constant and difference between maximum and remanent polarization were significantly improved by ZnO doping. Dielectric constant of NBT-BT-NN-1.0-wt% ZnO was 3218 at 1 kHz and room temperature, i.e. one time bigger than that of pure NBT-BT-NN ceramic. As a consequence, a maximum energy-storage density of 1.27 J/cm³ with a corresponding efficiency of 67% was obtained in NBT-BT-NN-1.0-wt% ZnO ceramic. Moreover, its pulsed discharge energy density was 1.17 J/cm³, and 90% of which could be released in less than 300 ns. Therefore, ZnO doped NBT-BT-NN ceramic with a large energy-storage density and short release time could be a potential candidate for applications in high energy-storage capacitors.     

Novel self-reinforcing ZrO2–SiO2 aerogels with high mechanical strength and ultralow thermal conductivity

Novel self-reinforcing ZrO₂–SiO₂ aerogels with high mechanical strength and ultralow thermal conductivity are fabricated by impregnating hydrolyzed ZrO₂–SiO₂ sol into wet gel matrix and drying. The ZrO₂–SiO₂ sol fills the macropores and defects of ZrO₂–SiO₂ aerogel matrix generating during the gelation process, which contributes to the improvement of the mechanical properties of the ZrO₂–SiO₂ aerogel matrix. The mechanical and thermal properties of the as-prepared ZrO₂–SiO₂ aerogel are investigated and discussed. The results show that the mechanical strength of the self-reinforcing aerogels obviously increases from 0.51 to 3.11?MPa with the increase of impregnation times, while the thermal conductivity of the aerogels slightly increases from 0.0235 to 0.0306?W?m^?1 K^?1. The novel self-reinforcing ZrO₂–SiO₂ aerogel could have interesting applications in aerospace and energy because of its outstanding mechanical and thermal properties.     

Preparation,dielectric property and microwave absorption property of Cu doped SiC nanopowder by combustion synthesis

Abstract

Cu doped SiC nanopowders have been prepared via combustion synthesis, using silicon powder and carbon black as the raw materials, copper powder as the doping source and polytetrafluoroethylene as the chemical activator respectively. The microstructure of prepared nanopowders has been characterised by X-ray diffraction and scanning electronic microscope. The electric permittivities of prepared SiC nanopowders in the frequency range of 8·2–12·4 GHz have been determined. Results show that prepared β-SiC nanopowders have fine spherical particles and narrow particle size distribution, and a quantity of SiC whisker increases with increasing Cu doping content. The Cu₃Si impurity has been generated when Cu content is up to 10%. The β-SiC doped with 10% Cu has the highest real part ?′ and dielectric loss tanδ values. The 5% Cu doped SiC nanopowder with matching thickness of 2 or 2·5 mm exhibits the best microwave absorption properties in the frequency range of 8·2–12·4 GHz.     

Structural,morphological and optomagnetic properties of GO/Nd/Cu-Mn ferrite ternary nanocomposite

Graphene oxide (GO)/neodymium (Nd)/Cu_0·5Mn_0·5Fe₂O₄ ternary nanocomposite was prepared by sonochemical method and modified Hummer's method. The crystal structure and structural parameter of Cu_0·5Mn_0·5Fe₂O₄ (CMF) nanoferrites were changed with the addition of Nd³⁺ and GO. Raman active modes of the GO and ferrite system were observed from Raman spectra. The surface oxidation state (C 1s, O 1s, Cu 2p, Mn 2p, Fe 2p, and Nd 3 d) and their respective binding energies of the prepared nanocomposite were discussed. Different surface morphologies were acquired for CMF, Cu_0·5Mn_0·5Fe_1.85Nd_0.15O₄ (CMNF), GO, and GO/Cu_0·5Mn_0·5Fe_1.85Nd_0.15O₄ (GCMNF) ferrite nanocomposites. The absorption of the Cu-Mn nanoferrite (red region) shifted into the blue region with the addition of Nd³⁺ and GO. The magnetic parameters were changed with doping of Nd into CMF and GO in CMNF nanoferrite. It was found that the high anisotropy energy values of the CMNF and GCMNF ferrite nanocomposites could be used for electromagnetic wave-absorbing application.     

Effects of high-temperature annealing on the microstructure and properties of C/SiC–ZrC composites

C/SiC–ZrC composites were prepared by a combining slurry process with precursor infiltration and pyrolysis, and then annealed from 1200 °C to 1800 °C. With rising annealing temperature, their mass loss rate increased, and the flexural strength and modulus decreased from 227.9 MPa to 41.3 MPa and from 35.3 GPa to 22.7 GPa, respectively. High-temperature annealing, which elevated thermal stress and strengthened interface bonding, was harmful to the flexural properties. However, it improved the ablation properties by increasing the crystallization degree of SiC matrix. The mass loss rate and linear recession rate decreased with increasing annealing temperature and those of the samples annealed at 1800 °C were 0.0074 g/s and 0.0011 mm/s respectively. Taking mechanical and ablation properties into consideration simultaneously, the optimum annealing temperature was 1600 °C.