PTFE/陶瓷复合介质结构与性能

选择SrTiO3系、TiO2系陶瓷料与PTFE树脂进行复合,探讨了PTFE/陶瓷在不同的配比时对复合介质抗拉强度的影响规律,借助SEM、IR对材料的微观结构进行了观察与分析,基于建立的结构模型和抗拉强度数学表达式,较好地解释了陶瓷类型、含量、粒径等因素对复合材料抗拉强度影响的实验结果。     

改性钛酸锶/PVDF复合材料介电性能研究

采用具有强络合能力的酒石酸在碱性溶液中对SrTiO3陶瓷颗粒进行表面改性,将改性后的SrTiO3颗粒与聚偏二氟乙烯(PVDF)经热压共混成型,制备出系列陶瓷/聚合物基复合材料,对改性SrTiO3/PVDF复合材料进行了介电性能分析。结果表明:添加了改性SrTiO3的复合材料比未改性SrTiO3复合材料的介电常数增加值达34%以上,同时,改性复合材料的介电损耗仍保持较低水平;随着改性SrTiO3在复合材料中含量的增加,介电常数也随之增加,介电损耗仍保持不变,改性后的陶瓷/聚合物复合材料表现出优异的综合介电性能。     

PTFE/Al2O3纳米复合材料的摩擦磨损性能研究

利用MM—200型摩擦磨损试验机研究了PTFE／Al2O3纳米复合材料的摩擦磨损性能，并采用扫描电子显微镜观察、分析了试样磨屑形状及磨损机理。结果表明，经表面处理的纳米Al2O3能明显提高PTFE的耐磨损性并改变其磨屑形成机理；当表面处理纳米Al2O3含量为3％时，PTFE纳米复合材料的磨损量最小，但在试验范围内，表面处理纳米Al2O3含量变化对PTFE纳米复合材料的耐磨损性影响不大，而PTFE纳米复合材料的摩擦系数则随表面处理纳米Al2O3含量增加而略有增大，导致PTFE磨损的机理主要是粘着磨损。     

贫铁锰锌铁氧体材料电磁特性

用传统陶瓷工艺制备MnZn和NiZn铁氧体材料.在富铁MnZn铁氧体材料Curie温度经验公式的基础上,提出了贫铁MnZn铁氧体材料Curie温度的经验计算公式.比较研究了贫铁MnZn铁氧体、富铁MnZn铁氧体和NiZn铁氧体材料的起始磁导率和电阻率的频率特性.在低频区域,贫铁MnZn铁氧体的高起始磁导率与富铁MnZn铁氧体相当;在高频区域,贫铁MnZn铁氧体的高起始磁导率与NiZn铁氧体相当;贫铁MnZn铁氧体的电阻率高达103 Ω·m.贫铁MnZn铁氧体几乎兼具了富铁MnZn铁氧体的低频特性和NiZn铁氧体的高频特性,且Curie温度也不低,是一种很有应用潜力的软磁铁氧体材料.     

Al2O3/PTFE复合材料的磨损性能研究

用机械共混、冷压成型烧结的方法制备了Al2O3／PTFE复合材料试样。用MM-200型磨损试验机测试了在干摩擦定载荷条件下各试样的磨损性能；用扫描电子显微镜(SEM)对磨损试样的表面形貌和磨屑的形貌进行了观察和分析；用光学显微镜对磨损后偶件环的表面形貌作了观察分析。结果表明：在实验条件下，Al2O3／PTFE复合材料的抗磨损性能，随Al2O3用量的增大逐渐增强，当Al2O3用量大于35％后，抗磨损性能增强的趋势明显减缓；在干摩擦条件下Al2O3／PTFE复合材料主要发生粘着磨损和磨粒磨损，且随Al2O3用量的增加，磨粒磨损所起的作用也增大。     

高磁导率MnZn铁氧体的配方和烧结工艺

高磁导率MnZn铁氧体作为现代电子行业和信息产业中的一项基础性材料,在现代信息技术的不断发展中,高磁导率MnZn铁氧体正在向着高频率、低损耗的方向发展,促进着人们对高磁导率MnZn铁氧体配方和烧结工艺研究力度的不断加深。在提高MnZn铁氧体磁导率上,其主要是通过优化配方和改善烧结工艺来实现的,基于此,文章以综述的方法,对高磁导率MnZn铁氧体的配方和烧结工艺进行了阐述。     

MnZn铁氧体的制备及其吸波性能研究

采用氧化物陶瓷工艺制备高磁导率MnZn铁氧体,以Mn_3O_4、Fe_2O_3和ZnO为原料,对ZnO过量对铁氧体的磁性能的影响进行了深入研究,确定了最佳配方,并测试了该铁氧体在微波频率下的电磁参数,模拟分析了该粉体的吸波性能。结果表明,当三种氧化物的摩尔比n(Fe_2O_3)∶n(Mn_3O_4)∶n(ZnO)为52.8∶24.2∶24时制得的MnZn铁氧体磁性能最佳,频率为200 KHz时,磁导率为19.5;模拟厚度4 mm时,有两个吸收峰分别为(3.38 GHz,-7.96 d B)和(18 GHz,-5.53d B),在(2~8.48)GHz和(16.98~18)GHz频率范围内,反射率R小于-2 dB,说明MnZn铁氧体在整个微波频段(2-18)GHz有一定的吸波性能。     

低损耗MnZn铁氧体材料的研究现状及发展趋势

介绍了低损耗MnZn铁氧体的研究现状及TDK,SIMENS等公司最新产品情况,通过对原材料的性质、掺杂和烧结工艺分析,说明它们决定了低损耗MnZn铁氧体的微观结构,同时也表明原材料的匹配对提高材料的性能有重要作用.探讨了低损耗MnZn铁氧体材料的工艺发展方向.     

不同填料对PTFE复合材料硬度的影响

使用超细及纳米SiO2颗粒和Al2O3颗粒填充改性聚四氟乙烯（PTFE）塑料，测量其硬度（HB），并使用扫描电镜对其表面形貌进行了分析。结果表明，SiO2纳米粒子填充较SiO2微米粒子填充的PTFE复合材料的硬度高34％～60％。Al2O3纳米粒子填充较Al2O3微米粒子填充的PTFE复合材料的硬度高。用溶胶凝胶法制得的纳米SiO2／PTFE复合材料比用机械混合法制备的高。     

碳纤维和纳米氮化硼增强聚醚醚酮/聚四氟乙烯复合材料的摩擦学性能研究

以碳纤维（CF）为增强相，添加不同含量的纳米氮化硼（h-BN），通过注塑成型的方式，制备了聚醚醚酮/聚四氟乙烯（PEEK/PTFE）复合材料样条，使用力学试验机进行拉伸试验，利用摩擦试验机进行表面摩擦试验，并利用白光仪对磨痕数据和三维形貌进行观测，使用SEM对磨痕进行观测与分析。结果表明：随着h-BN含量的增加，PEEK/PTFE复合材料样条最大应力先增加后减小；当h-BN含量分别为3%、6%时，PEEK/PTFE复合材料样条的最大应力分别为174 MPa、165 MPa。与PEEK/PTFE相比，单独添加CF的样品摩擦系数降至0.23。同时添加CF、h-BN时，复合材料样条的摩擦系数均降低；h-BN含量分别为3%、6%时，复合材料样条的摩擦系数分别为0.06、0.09。随着h-BN含量的升高，PEEK/PTFE/CF/h-BN复合材料的磨损率先降低后升高。h-BN含量为3%时，复合材料样条的磨损率最低。     

Effect of a YIG nanoparticle additive on the magnetic properties of MnZn ferrites for MHz frequency applications

In this study, MnZn ferrites with added YIG nanoparticles were developed for MHz frequency applications. The effect of the magnetic YIG additive on the power loss, initial permeability, and cutoff frequency of MnZn ferrites was investigated. A small quantity of added YIG effectively reduces the power loss and concurrently increases the initial permeability. Compared to the results for the MnZn ferrite with no added YIG, the optimal MnZn ferrite with 600 ppm added YIG exhibits a reduction in the power loss at 25°C of 56.4% and 36.6% at 1 MHz/50 mT and 3 MHz/10 mT, respectively, and a 13.9% increase in the initial permeability. This sample also exhibits a good stability of the power loss against temperature. The power loss remains below 205 kW/m³ over temperatures ranging from 25 to 140°C. The effect mechanism of YIG addition on the magnetic properties of MnZn ferrites was studied. An analysis based on the equivalent circuit model showed that the reduction in the eddy current loss and power loss mainly results from the increase in the grain boundary resistance caused by the addition of highly resistive YIG.     

Li2MoO4‐based composite ceramics fabricated from temperature‐ and atmosphere‐sensitive MnZn ferrite at room temperature

The first magnetic ceramic composites manufactured, using the room‐temperature densification method are reported. The samples were prepared at room temperature using Li₂MoO₄ as a matrix and MnZn ferrite with loading levels of 10‐30 vol‐% followed by postprocessing at 120°C. The method utilizes the water solubility of the dielectric Li₂MoO₄ and compression pressure instead of high temperatures typical of conventional solid‐state sintering. Hence, composite manufacturing using temperature‐ and atmosphere‐sensitive materials is possible without special conditions. This was demonstrated with MnZn ferrite, which is prone to oxidation when heat treated in air. Samples manufactured with room‐temperature densification showed no signs of reactivity during processing, whereas reference samples sintered at 685°C suffered from oxidation and formation of an additional reaction phase. The densities achieved with different loading levels of MnZn ferrite with both methods were very similar. Measurements up to 1 GHz showed relatively high values of relative permittivity (21.7 at 1 GHz) and permeability (2.6 at 1 GHz) with 30 vol‐% loading of MnZn ferrite in the samples manufactured by room‐temperature densification. In addition, pre‐granulation is proposed to improve the processability of the composite powders in room‐temperature densification.     

羰基铁粉/锶铁氧体/MVQ吸波复合材料的制备与性能研究

以羰基铁粉与锶铁氧体为吸波填料制备羰基铁粉/锶铁氧体/甲基乙烯基硅橡胶(MVQ)吸波复合材料,研究羰基铁粉/锶铁氧体并用比对羰基铁粉/锶铁氧体/MVQ吸波复合材料性能的影响。结果表明,羰基铁粉/锶铁氧体/MVQ复合材料吸波峰处于羰基铁粉/MVQ和锶铁氧体/MVQ复合材料之间,在填料总体积分数不变的前提下,随着羰基铁粉用量的减小,复合材料吸波峰小于-10 dB的带宽先增大后减小、吸波峰向高频方向移动、拉伸强度和拉断伸长率变化不大、压缩永久变形减小、动态性能提高。     

Two-step doping of SiO2 and CaO for high-frequency MnZn power ferrites

SiO₂ and CaO are empirical but effective co-doping oxides for low-loss MnZn soft ferrites. However, the underlying mechanism of the synergistic effect remains unclear. Herein, we systematically investigate the effect of SiO₂ and CaO, and propose a two-step doping strategy for high-frequency MnZn ferrites. It is found that SiO₂ facilitates the formation of mono-domain grains, thereby reducing the residual loss at high frequency. Meantime, CaO may dissolve into ferrite matrix with improved resistivity but abnormal growth of grains. By preliminarily coating MnZn particles with SiO₂, the reaction between CaO and ferrite matrix could be effectively suppressed, leading to the formation of continuous calcium silicate grain boundary (GB) phase. Consequently, superior high-frequency performance than traditional one-step doping strategy including initial permeability of 498, cut-off frequency of 12.6 MHz, power loss of 326 kW/m³ (5 MHz, 10 mT) can be obtained, which is desired by miniaturized electronic devices.     

掺杂对共沉淀法制备的锰锌铁氧体性能的影响

通过加入添加剂,制备了晶相单一、结晶度完好、具有较好磁性能的锰锌铁氧体纳米晶,然后研究添加剂对铁氧体晶相、磁性能和居里温度的影响.研究结果表明:添加剂可以使晶体生长更完善,晶粒变大;同时可以改善样品的磁性能,降低居里温度.     

机械泵旋片基材表面化学镀Ni-P/PTFE复合镀层

在机械泵旋片用45Mn钢板表面制备了化学镀Ni-P/PTFE复合镀层,并研究了PTFE的质量浓度对化学镀Ni-P/PTFE复合镀层的沉积速率、耐磨性、耐蚀性及表面形貌的影响。结果表明:适当增加PTFE的质量浓度,有利于加快沉积速率,提高化学镀Ni-P/PTFE复合镀层的耐磨性和耐蚀性。化学镀Ni-P/PTFE复合镀层表面呈胞状形貌,PTFE均匀分布在表面。当PTFE的质量浓度为8 g/L时,化学镀Ni-P/PTFE复合镀层具有最佳的耐磨性和耐蚀性。     

Sintering of Nanosized MnZn Ferrite Powders

The sintering and microstructural evolution of nanosized MnZn ferrite powders prepared by a hydrothermal method were investigated. The microstructure of sintered ferrite compacts depends strongly on the strength of the agglomerates formed during the compacting of nanosized ferrite powders. It was found that at 700°C the theoretical density of sintered compacts can almost be reached, while above 900°C an increase of porosity was identified. The formation of extra porosity at higher sintering temperatures is caused mainly by the oxygen release which accompanies the dissolution of relatively large grains of residual alpha-Fe₂O₃ in the spinel lattice.     

The effects of Barium Strontium Titanate (BST) on the soft magnetic properties and loss performance of MnZn ferrites

With the increasing power density of the switched mode power supply (SMPS) developed nowadays, higher efficiency is required from the magnetic core, where the MnZn ferrites are often adopted. However, the relatively high operating temperature of the SMPS often results in reduced resistivity of the MnZn, which increases the eddy current loss. To enhance the resistivity of MnZn ferrite at high temperature range (>100 °C), donor-doped barium strontium titanate (BST) with a positive temperature coefficient of resistivity (PTCR) is prepared and dopped in the MnZn ferrite. The influence of BST addition from 0.000 wt% to 0.020 wt% on the MnZn ferrite is investigated over a wide temperature range from 25 °C to 140 °C. The XRD result suggests ionic exchange between the spinel phase and perovskite phase. The SEM result shows a refined and more uniform microstructure of MnZn ferrite brought about by the BST addition. At the maximum of 0.020 wt%, the BST addition shows almost no influence on density and the saturation magnetic induction. However, the initial permeability is slightly reduced by the BST addition, due to the microstructural change. Moreover, the BST concentrating at the grain boundaries improves the DC-resistivity across the temperature range from 25 °C to 140 °C. Due to the addition of BST, the reduction in eddy current loss at 300kHz/100 mT is around 35% at 25 °C, and ∼20% reduction at 140 °C.     

Magnetic properties of MnZn ferrite nanoparticles obtained by SHS and sol-gel autocombustion techniques

MnZn ferrite nanoparticles have been synthesized by self-propagating high temperature synthesis (SHS) and sol-gel autocombustion techniques. The crystallite size, microstructure and magnetic properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. The results showed that single phase manganese ferrite could be achieved directly without any post calcination. However, the crystallite size of the sol-gel autocombusted sample (44 nm) was finer than that of the SHS (57 nm). The SHS synthesized MnZn ferrite with the larger crystallite size exhibited the larger magnetization of 50.6 emu/g than that of 20.9 emu/g for the sol gel autocombusted nanoparticles, despite of its more structure inversity.