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.     

Mechanical Properties of Compression Molded Banana Pseudo-stem Filled Unplasticized Polyvinyl Chloride (UPVC) Composites

Mechanical strengths of a banana pseudo-stem (BPS) fiber and unplasticized polyvinyl chloride (UPVC) composite were evaluated to assess the possibility of using it as a new material in engineering applications. Samples were fabricated by the compression molding process with reference to the effect of filler loading. The samples were submitted to mechanical tests to measure tensile, flexural, and impact properties of the composites. The nature of adhesion between the matrix and the reinforcement and information relating the structure of mechanical properties can be obtained by scanning electron microscopy (SEM) assessment of the composite fracture surface. The mechanical properties show that the composites did not have good adhesion between filler and matrix; on the other hand, the filler insertion improved the flexural modulus and the material rigidity.     

单向玻璃纤维-铝合金层板的几种力学性能研究

本文用实验方法研究了单向玻璃纤维-铝合金层板的拉伸性能、疲劳性能和冲击性能。利用金属体积分数理论验证了这类层板的拉伸性能。通过对其疲劳性能的实验研究，发现裂纹扩展速率的大小及刚度的下降与加载的最大循环应力密切相关的规律。实验发现该层板具有比铝合金好得多的冲击性能。     

核壳型纳米粒子合成方法及其性能的研究进展

核壳纳米粒子作为复合纳米粒子一个重要的分支,由于其光、磁和催化等方面的优异性能,近年来引起了人们广泛的关注.本文主要介绍了核壳纳米粒子的制备方法及诸多性能,并对核壳纳米粒子的发展进行了展望.     

TMPTMA在硅橡胶中的应用研究

研究了助交联剂三羟甲基丙烷三甲基丙烯酸酯(TMPTMA)对硅橡胶硫化性能、力学性能、低温性能和粘接性能的影响。结果表明,加入少量TMPTMA能改善硅橡胶的硫化特性和工艺性,提高硫化胶的硬度,降低硅橡胶的结晶温度,并有效提高硅橡胶与金属的粘接强度;但TMPTMA用量超过一定数值后,由于TMPTMA部分自聚合,在硅橡胶内形成一定的交联网络,造成两相界面粘接力变差,致使硅橡胶的拉伸强度降低。当TMPTMA用量为1份时,硅橡胶具有最佳的综合性能。     

Effects of support and additive on oxidation state and activity of Pt catalyst in propane combustion

The effects of support and additive on the oxidation state and catalytic activity of Pt catalyst in the low temperature propane combustion were systematically investigated on Pt/MgO, Pt/Al₂O₃ and Pt/SiO₂–Al₂O₃. The catalytic activity varied much with both support materials and additives. The catalyst on the more acidic support showed higher activity, and the catalytic activity on every support materials increased as the electronegativity of additives increased, while some additives decreased the activity. The oxidation state of platinum, estimated by white line intensity of Pt L_III-edge XANES spectrum, also varied with the support and additives, and additives with higher electronegativity greatly prevented the platinum from its oxidation under oxidising atmosphere. Among almost all the catalysts with various supports and various additives, a clear relationship was observed between the oxidation state of platinum and the catalytic activity; the more metallic platinum showed higher activity. Thus, it was concluded that the total electrophilic/electrophobic property derived from those of the support and additive controls the oxidation state of platinum, which intensively affects the catalytic activity; i.e. higher electrophilic property provides less oxidised platinum, resulting in high catalytic activity. The mechanism of this effect was also discussed on the basis of thermochemical data, and it was proposed that the electrophobic materials promote the noble metal oxidation since the noble metal oxo-anion such as PtO^δ− is more stabilised with electrophobic cation.     

聚丙烯基抗菌塑料的制备与性能研究

利用熔融挤出共混技术制备了聚丙烯(PP)基抗菌塑料。研究了抗菌母料Antim-PP对PP的抗菌性能和力学性能的影响。结果表明,当抗菌母料与PP的质量比为4:100时,抗菌PP塑料对大肠杆菌的抗菌率大于99%,抗菌母料的加入使共混物的冲击性能有明显改善,其他力学性能基本不受影响。     

阻隔性PET/PEN共聚酯的性能研究

对共聚型阻隔聚酯PETNx(x为共聚酯中NDA占羧酸总质量的百分比)的热性能、流变性能和阻隔性能进行了研究。结果表明,PETNx体系属于假塑性流体。PETNx的CO2气体阻隔性优于常规PET;随着PETNx中NDA含量的增加,共聚物的玻璃化温度呈线性增高。     

丁腈橡胶的伏安特性与功率特性的研究

本文对乙炔碳黑填充丁腈橡胶（NBR）的伏安特性及其功率特性进行了研究,分析了丁腈橡胶在交、直流电场下的导电机理,并对环境温度变化时的丁腈橡胶的功率及功率与电压的变化规律提出了相应的关系式,同时对导电丁腈橡胶的物理机械性能进行了研究与测定。     

聚氨酯种类对机械性能以及阻尼性能影响研究

分别以聚四氢呋喃醚二醇(PTMEG)、聚氧化丙烯二醇(PPG-1000)为软段,以二苯基甲烷二异氰酸酯(MDI-50、MDI-100LL),以及扩链剂1,4-丁二醇(BDO)、三羟甲基丙烷(TMP)为硬段,采用预聚体法制备了聚氨酯弹性体。并系统研究了聚氨酯体系中各组分的种类对材料机械性能和阻尼性能的影响。     

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.     

甲基丙烯酸锌补强氢化丁腈橡胶耐老化性能的研究

试验研究甲基丙烯酸锌（ZDMA）补强氢化丁腈橡胶（HNBR）热空气老化前后的物理性能和动态力学性能。结果表明:随着ZDMA用量的增大,HNBR胶料的t₁₀和t₉₀缩短,M_L和M_H增大,硫化胶的邵尔A型硬度和100%定伸应力增大,拉伸强度和拉断伸长率先增大后减小;经热空气老化后,随着老化时间的延长,HNBR硫化胶的邵尔A型硬度和100%定伸应力增大,拉伸强度和拉断伸长率减小;延长老化时间或增大ZDMA用量,HNBR硫化胶的储能模量和损耗模量增大,损耗因子峰值逐渐减小,损耗模量峰值和玻璃化温度逐渐向高温方向移动。     

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.     

对苯二甲酸乙二酯/聚乙二醇共聚醚酯的热性能研究

将含有磺酸盐基团化合物及不同添加量的聚乙二醇(PEG)与对苯二甲酸乙二酯共聚合成共聚醚酯(COPEET),利用差示扫描量热分析法(DSC)研究了一系列COPEET的玻璃化转变温度、结晶温度以及熔融温度等的变化规律。结果表明:随PEG添加量的增加,COPEET的玻璃化转变温度有规律地下降;PEG质量分数小于30%时,有利于冷结晶、结晶度下降;继续增加PEG则COPEET变得难于结晶;PEG质量分数小于40%时,热结晶容易,但结晶度下降;PEG添加量更高时,熔融结晶变得困难了;添加PEG会降低COPEET的熔点。     

BLQ-343丙纶强力丝油剂的研制

介绍了丙纶强力丝对油剂的特殊要求,论述了BLQ-343油剂的研制、性能及应用。研究表明,该油剂原油在-4-40℃下贮存一年无变化,乳液在10-35℃下放置三周无变化,平滑性、抗静电性、润湿性、耐热性优于国内同类产品,且可纺性好,能满足丙纶强力丝工艺要求,可以推广应用。     

Phase stability,mechanical and thermodynamic properties of (Hf,Zr, Ta,M)B2 (M= Nb,Ti, Cr,W) quaternary high-entropy diboride ceramics via first-principles calculations

As the high-entropy design concept applied to the diboride ceramic system, high-entropy diboride ceramics with a wide range of composition control, is expected to become a new high-performance material for extreme high-temperature environments. Herein, the effects of four transition metal elements (Nb, Ti, Cr, W) on the phase stability and properties of (Hf, Zr, Ta)B₂-based high-entropy diboride ceramics are systematically investigated via the first-principles calculations. All components were identified as thermodynamically, mechanically and dynamically stable from enthalpy of formation, elastic and phonon spectrum calculations. Among these, compared with the (Hf, Zr, Ta)B₂ ceramics, the addition of Nb and Ti on the metal sublattice is beneficial to improve the mechanical properties of ceramics, including Young's modulus, hardness and fracture toughness, while the introduction of Cr and W weakens the strength of covalently and ionic bonds inside the material, reducing its mechanical properties. The predicted thermophysical properties show that the high-entropy diboride ceramics containing Nb and Ti have better high-temperature comprehensive performance, including higher Debye temperature, thermal conductivity and lower thermal expansion characteristics, which is conducive to the application in extreme high-temperature environments. This research will provide important guidance for the design and development of new high-performance high-entropy diboride ceramics.     

聚丙烯/石墨烯复合材料性能研究进展

利用石墨烯优异的导电率、断裂强度等物理性质,可使聚丙烯(PP)/石墨烯复合材料表现出更好的力学性能以及导电性能。主要概述了PP/石墨烯复合材料的合成方法及其性能改进研究进展,并对PP/石墨烯复合材料的未来发展做了展望。     

锦纶POY存放时间对纤维性能的影响

研究了存放时间对锦纶POY纤维含水率、含油率、抱合性、摩擦特性、油膜状态以及抗静电性等性能的影响。发现随着时间的延长,纤维表面油剂浓度增高,油膜状态变差,纤维摩擦性能、抱合性能以及抗静电性能下降。     

Study of the Mechanical,Thermal Properties and Morphology of Polypropylene Nanocomposites in the Presence of Compatibilizer

In this work, the mechanical, rheological, and thermal properties and morphology of a polypropylene matrix reinforced with single-walled nanotubes (SWNTs) were investigated. Polypropylene-grafted-maleic acid was used as a compatibilizer to promote SWNTs dispersion. Compared to uncompatibilized nanocomposites, the tensile modulus of the material increased considerably when nanotubes and compatibilizer were employed. The rheological characterization results revealed that addition of SWNTs increased the storage modulus and complex viscosity at low frequencies. SEM revealed that the SWNTs were uniformly distributed when low concentrations of SWNTs were employed. The results of DSC indicated that the addition of SWNTs increased the crystallinity of nanocomposites.