锶铁氧体/尼龙12磁性复合材料的结构与性能

以锶铁氧体和尼龙12为原料,通过共混挤出制备了长链聚酰胺磁性复合材料,采用高压毛细管流变仪,动态热机械分析法等测试表征手段研究了锶铁氧体的添加量对锶铁氧体/尼龙12复合材料结构和性能的影响。结果表明,锶铁氧体添加量较高时复合材料可拥有较好的磁性能,力学性能和加工性能。     

磁性填料填充弹性材料的硫化特性和硫化胶性能

研究了天然橡胶和顺丁橡胶磁复合材料的制备及材料性能。同类锶铁氧体SrFe12O19的三种改性体用作磁性填料。所用铁氧体的粒径分布以及其他物理性能和磁特性不同。研究了磁性填料对复合材料硫化特性、物理性能以及磁性能的影响。     

改性碳纳米管与锶铁氧体复合材料的制备及性能研究

利用H2O2和浓H2SO4的混合溶液、浓硝酸分别对碳纳米管（CNTs）进行改性处理,并用改性CNTs与一定量的硝酸铁、硝酸锶反应．制备出了改性碳纳米管与锶铁氧体复合材料。利用IR、VSM、TEM等检测了材料的性能。结果表明,改性后的碳纳米管表面主要引入了羟基、羰基,其水溶性明显增强;复合材料的磁性能较好,但加入CNTs后,复合材料的矫顽力呈降低趋势,且随着CNTs含量的增加,矫顽力降低越大。空白实验表明,锶铁氧体的粒径在20nm左右,这也是复合材料磁性能较高的主要原因。     

预烧温度对锶铁氧体的微结构和磁性能的影响

采用传统陶瓷工艺法,在相同配方、相同实验条件情况下制备了不同温度预烧的锶铁氧体,分析了预烧温度(1180℃,1200℃,1210℃,1250℃,1270℃,1290℃,1300℃,1310℃)对锶铁氧体微结构和磁性能的影响.X射线衍射分析表明,随着预烧温度的上升,锶铁氧体主体仍为六角锶铁氧体结构.预烧温度较低时,反应不完全,有Fe2O3杂相存在.通过扫描电镜对样品的形貌结构进行分析,测试结果显示铁氧体晶粒呈六角锶铁氧体片状结构,随着预烧温度的上升出现熔融甚至出现全部熔融;磁性能测试显示,样品的Br随预烧温度的上升先增大后减小,当预烧温度达到1290℃时,Br和(BH)max达到最大值,Br为422.85 mT,(BH)max为34.99 kJ/m3.Hcj先下降,预烧温度到1250℃时上升;Hcb先上升至1290℃时达到最大值,之后下降.综合各方面的性能,最佳的预烧温度确定为1290℃.     

分散剂对水热法合成镍钴铁氧体结构和吸波性能的影响

在水热法合成镍钴铁氧体的过程中分别加入不同分散剂[柠檬酸、十六烷基三甲基溴化铵(CTMAB)、十二烷基苯磺酸钠(SDBS)、聚乙烯醇(PVA)、十二烷基磺酸钠(SDS)],借助于FTIR、XRD、SEM和网络矢量仪等现代测试技术研究分散剂对镍钴铁氧体结构和性能的影响。结果表明,柠檬酸不利于尖晶石镍钴铁氧体的生成。在水热合成过程中,分散剂的存在并未影响铁氧体的化学组成和物相结构。以SDS、PVA、CTMAB为分散剂时,粒径均匀且分散性良好,吸波性能皆有提高,尤以PVA为分散剂时吸收性能最佳(14.26 GHz处的最大反射损耗值为-17.33 dB)。     

吸波填料W型六角晶系锶铁氧体对甲基乙烯基硅橡胶吸波性能的影响

研究3种W型六角晶系锶铁氧体(BMA-PX,WPS,WPX)作吸波填料对甲基乙烯基硅橡胶(MVQ)吸波性能的影响。结果表明:3种W型六角晶系锶铁氧体均为无规的碎石状颗粒,元素组成不同,吸波性能差异较大。铁元素质量分数较大的BMA-PX吸波MVQ磁损耗较大,容易实现阻抗匹配,在中高频下的电磁波反射率低,吸波性能优异。     

柠檬酸法制备Sr—铁氧体超细粉

本文采用柠檬酸作为络合剂，制备了超细锶铁氧体超细粉，经过Ｘ射线结构分析，电子透射电子显微镜，振动样品磁强计等技术对粉末的粒径，结构和磁学性能进行了分析测试结构表明，该方法合成的锶铁氧体具有粒径小，粒度均匀，性能高，工艺简单等特点。     

钡铁氧体粉体及其复合电纺纤维的制备

通过化学共沉淀法制备了磁铅石型钡铁氧体粉体,采用激光粒度仪、扫描电子显微镜（SEM）和X-射线衍射仪（XRD）等对其进行表征测试,并采用微波网络分析仪对该粉体的吸波性能进行了初步研究。分别将化学共沉淀法制备的钡铁氧体粉体以及粒径为纳米级的钡铁氧体粉体与聚乙烯吡咯烷酮（PVP）共混后静电纺丝,通过调节钡铁氧体粉体的加入方式及其分散状态等条件,探索最佳纺丝状态,制备出了负载钡铁氧体粒子的电纺纤维毡,采用扫描电子显微镜（SEM）观测了纤维形貌。     

不同分散剂、不同分散方法对纳米TiO2分散性能的影响

选取十六烷基三甲基溴化铵（CTAB）、六偏磷酸钠（SHMP）及聚丙烯酸钠（PAAS）作分散剂,并采用超声分散和机械分散方法制备纳米TiO2悬浮液,对纳米TiO2在水和无水乙醇中的分散性能进行了研究。通过测试不同分散体系中纳米TiO2粒子的粒径及分布宽度,探讨了不同分散剂对纳米TiO2分散性能的影响。结果表明：不同分散荆、分散方法和分散液对纳米TiO2的粒径都有明显影响,且粒径分布宽度差别较大。     

桐油改性苯乙烯 -马来酸酐共聚物的制备及其对水性炭黑色浆的分散性研究

通过对桐油进行二次酯交换获取桐油基醇（ TOBA）然后以桐油基醇（ TOBA）、苯乙烯 -马来酸酐共聚物（ SMA）和甲氧基聚乙二醇（ MPEG）为主要原料，，合成了不同桐油含量的梳型聚合物分散剂（TOBA-SMA-MPEG），并将 TOBA-SMA-MPEG作为分散剂制备了水性炭黑色浆。采用 FT-IR和 ¹H NMR对 TOBA-SMA-MPEG的化学结构进行了表征；通过对水性炭黑色浆的微观形貌、黏度、展色性、粒径、离心稳定性及贮存稳定性进行分析，考察了桐油含量及分散剂用量对炭黑分散性能的影响。结果表明：成功制备了 TOBA、SMA和 MPEG物质的量比为 1∶1∶3的 TOBA-SMA-MPEG聚合物分散剂；当其添加量为 6%时，对水性炭黑色浆的分散性最好，色浆平均粒径可降至 181. 8 nm；经桐油改性后的梳型聚合物分散剂可以提高水性炭黑色浆的分散稳定性。     

Effect of synthesis variables on viscoelastic properties of elastomers filled with carbonyl iron powder

This work studies the influence of synthesis variables on the lineal viscoelastic properties of elastomers filled with soft magnetic particles. Three matrices [natural rubber (NR), high-temperature vulcanising silicone rubber (HTV-SR), and room-temperature vulcanising (RTV-SR)] and three volumetric particle contents (0%, 15%, and 30%) were studied. Anisotropic samples were synthesised with a softer matrix to obtain a larger magnetorheological (MR) effect, and the variation of their properties under an external magnetic field was examined. All samples were characterised within the lineal viscoelastic (LVE) region using a rheometer, because the MR effect is larger within this region. The influence of the matrix, particle content, and pre-structure on the viscoelastic properties of the synthesised samples was studied. The storage and loss modulus increased with the frequency owing to the viscoelastic behaviour of an elastomer in the rubbery phase. Both moduli also increased with the filler content. The influence of the filler is dependent on the matrix, and the maximum variation was seen in the NR-based samples. However, the maximum MR effect was seen in the samples with a softer matrix, and the effect was enhanced in the anisotropic samples. In this work, the MR effect on the loss modulus was studied, and the tendencies were found to be similar to those of the storage modulus. The main contribution of this work is that all dynamic behaviour results were comparable because all synthesis variables and characterisation conditions were identical. Therefore, how the particle content, frequency, and magnetic field affects each matrix can be studied.     

稀土Dy~(3+)改性铁氧体磁流体磁性粒子的制备及性能测试

研究稀土铁氧体表面改性,采用化学共沉淀法制备了稀土铁氧体磁流体,并用古埃磁天平、透射电子显微镜、X射线衍射仪等对其进行了性能测试。同时探讨了稀土铁氧体磁性粒子的形成机理及表面活性剂对磁流体基本性质的影响;然后,系统地研究了当温度80℃,时间180 m in,表面活性剂用量比0.25,碱过量比0.6时稀土材料Dy3+的加入对铁氧体磁流体性能的影响,并对其进行了理论分析和探讨。     

A Comparison Study on the Magneto-Responsive Properties and Swelling Behaviors of a Polyacrylamide-Based Hydrogel Incorporating with Magnetic Particles

This work investigates the mechanical properties, microstructures, and water-swelling behavior of a novel hydrogel filled with magnetic particles. The nanoparticles of magnetite (Fe₃O₄) and the micro-particles of carbonyl iron (CI) were selected and filled into a polyacrylamide (PAAM) hydrogel matrix to create two types of magnetic hydrogels. The isotropy and anisotropy of magnetic hydrogels are also presented in this study. The isotropic samples were cured without applying a magnetic field (MF), and the anisotropic samples were cured by applying an MF in the direction perpendicular to the thickness of the samples. The effects of the size, content, and inner structures of magnetic particles on the magneto-responsive and swelling properties of magnetic hydrogels were investigated. It was found that the magnetorheological (MR) effect of anisotropic samples was apparently higher than that of isotropic samples, and the hydrogels with CI exhibited a noticeable MR effect than those with Fe₃O₄. The storage modulus can be enhanced by increasing the filler content and size, forming an anisotropic structure, and applying an external MF. In addition, the magnetic hydrogels also have a swelling ability that can be tuned by varying the content and size of the particle fillers.     

Improvement of flux pinning ability by tungsten oxide nanoparticles added in YBa2Cu3Oy superconductor

In this study, series of superconductor-tungsten oxide (WO₃) nanoparticles composites, YBa₂Cu₃O_7-δ/(WO₃)_x, were produced via the solid-state reaction process. The structural, morphological, chemical compositions, electrical and magnetic properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) along with EDX system and physical properties measurement system (PPMS), respectively. The XRD, SEM and EDX analyses showed the successful formation of the Y-123 orthorhombic phase. The electrical resistivity measurements proved the occurrence of superconductivity in different samples. The magnetic results showed an improvement of critical current density (J_c) and pinning ability in WO₃ nanoparticles added Y-123 products. The dominant pinning mechanisms and the strength of pinning centers in various sintered products were examined and discussed. The measurements of zero-field-cooled (ZFC) and field-cooled (FC) magnetization versus temperature (M-T) indicated an increase in the magnitude of diamagnetic signal with the addition of WO₃ nanoparticles in the Y-123 superconductor.     

Mechanical and thermal properties of UV cured mixtures of linear and hyperbranched urethane acrylates

The properties of urethane acrylate resin mixtures based on the linear and hyperbranched aliphatic polyesters were examined. Linear polyester was synthesized from neopentil glycol and adipic acid. Hyperbranched polyester of the third generation was synthesized from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylol propane. The modification of 60% of hyperbranched aliphatic polyester OH end groups was carried out with isononanoic acid or with soybean fatty acids. Two hyperbranched urethane acrylates, with the same degree of acrylation, and one linear urethane acrylate were obtained by reaction of appropriate polyester and isophorone diisocyanate and 2-hydroxyethyl acrylate. The influence of added amount of HUA and nature of non-acrylic end groups on the rheological, mechanical and thermal properties of the uncured and UV cured mixtures diluted with 20 wt.% hexanediol diacrylate was examined. The nature of non-acrylic end groups have great effect on the interaction between linear and hyperbranched urethane acrylates, which further has a crucial influence on the examined properties of uncured and UV cured mixture samples.     

Impact of the Zr-substitution on phase composition,structure, magnetic,and microwave properties of the BaM hexaferrite

Rapid developments in information technologies and a large rise in electrical and electronic equipment have generated different forms of electronic environmental contamination. Microwave absorption materials are important to avoid the damage that can be caused by electromagnetic radiation. A necessary condition for the absorption of the most incoming radiation is balanced wave impedance at the air/shield interface, which depends on the studied materials' magnetic and electrical properties. The paper introduces the preparation of BaFe_12-xZr_xO₁₉ (x = 0.1, 0.3, 0.6, 0.9, and 1.2) using a solid-state reaction technique. The studied samples were examined by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer, and a vector network analyzer. The studied samples showed that controlling the grain size and the prepared samples' magnetic properties play an important role in enhancing the microwave radiation absorption. The examined samples can be a promising absorption material in electromagnetic shielding applications.     

Effects of twin methyl groups insertion on the structure of templated mesoporous silica materials

In this paper, the effects of dimethyldiethoxysilane (DMDES) addition on the sol-gel process in preparation of mesoporous hybrid silicates containing twin methyl groups, were investigated. The materials were synthesized using tetraethoxysilane (TEOS) as silica source and DMDES as methyl groups precursor. All samples were prepared at low temperature in alkaline conditions using cetyltrimethylammonium bromide (CTAB) as a template. Obtained materials were characterized applying nitrogen adsorption/desorption, X-ray diffraction, HR TEM, FTIR, ²⁹Si MAS NMR and Raman spectroscopy methods. The influence of aging time (from 5?min to 24?h) on the structure of samples containing 12% (mol/mol) of organic modifier was examined. Duration of synthesis significantly affected the material structure. The effect of added organosilicate amount (12%, 25% and 38%) on morphology and structure properties of prepared samples was also studied. The dimethylsilyl groups were successfully incorporated in wide range in the silica surface using presented short time sol-gel method.     

Influence of humidity and of the electric and magnetic microwave radiation fields on the remediation of TCE-contaminated natural sandy soils

The influence of moisture content (15% w/w) on the remediation (vaporization) of trichloroethylene (TCE) present in natural sands, chosen as a TCE-polluted model system for soils, was investigated with regard to applied microwave power levels, the depth of the sand sample, and the dielectric factors. The heating process occurring in the sand samples arises through the microwave conduction loss heating and dielectric loss heating mechanisms. The characteristic relevance of the electric and magnetic microwave radiation fields to the heating mechanisms was also examined. Heating by the magnetic microwave radiation field was considerable when magnetite was added to the dry and wet sand samples as the microwave absorber. Optimal microwave conditions are reported for a single-mode microwave applicator. Near-quantitative elimination of the TCE contaminant was achieved for sandy soils within a very short time.     

Effects of Recycling on the Mechanical Behavior of Polypropylene at Room Temperature Through Statistical Analysis Method

This article reports the effects of recycled material percentage, annealing conditions, and glass fiber percentage on the mechanical behavior of injection molded polypropylene samples. Specimens were prepared with different percentages of recycled material ranging from 0 to 100%. Two groups of samples, i.e., non‐annealed and annealed at 150°C, were tested to investigate annealing effects. The effects of adding fiber (0–7.5%) to specimens was also investigated. It was found that increasing the amount of recycled material improves the material properties in a non‐linear trend. Annealing had a significant positive effect on both non‐fiber‐added and fiber‐added samples: it improved the yield stress of non‐reinforced polypropylene samples by more than 10% and their Young's modulus by about 50%. Fiber‐added materials showed more variability, and adding fiber also improved the Young's modulus and the yield stress of the samples by about 50%. The results indicate that the three factors investigated improved toughness of the injected polypropylene samples; however the effects are not significant. The study findings reveal that using recycled polypropylene has no significant effect on the material properties of polypropylene. POLYM. ENG. SCI., 56:1283–1290, 2016 © 2016 Society of Plastics Engineers     

Preparation and characterization of micron‐sized magnetic microspheres by one‐step suspension polymerization

Micron‐sized magnetic microspheres with different functional groups were prepared by one‐step suspension copolymerization of styrene, divinyl benzene, and methyl methacrylate in the presence of oleic acid‐coated magnetic nanoparticles. In the present work, we used benzoyl peroxide as an initiator and poly(vinyl alcohol) (PVA‐1788; degree of polymerization: 1,700; degree of hydrolysis: 88%) as a stabilizer. We also added acrylamide (AM) monomer in the aqueous phase and methacrylic acid (MAA) in the oil phase. The morphology and properties of the resulting magnetic microspheres were examined by optical micrographs (OMs), vibrating‐sample magnetometer (VSM), and Fourier transform infrared spectrometer (FT IR). The results showed the three products have uniform and spherical form with superparamagnetism and well dispersion. Moreover, we found that monomer AM had a little contribution to the copolymerization, and MAA could strikingly decrease the diameter of the final microspheres. The magnetic microspheres with functional groups could be linked well with the IgG‐FITC. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007