Crystallization and dielectric properties of lead-free glass-ceramic composites with Gd_2O_3 addition

Lead-free glass-ceramic composites in barium sodium niobate silica system with Gd2O3 addition were synthesized through melt-casting fol-lowed by controlled crystallization technique. Crystallization and dielectric properties of the Gd2O3 adding glass-ceramic composites were investigated. With the increase in the concentration of Gd2O3, the glass transition temperature and the crystallization temperature of the pre-cursor glass shift towards the higher temperature. The crystallization behavior that occurred during the heat treatment procedure leads to the enhancement of dielectric constant. All the three compositions of glass-ceramic composites exhibit ferroelectricity when tested at room tem-perature. Both the values of the remanent polarization and coercive field are enhanced regularly with the gradual increase in the concentration of Gd2O3 additive under the same testing field.

Mechanical Properties and Dimensional Stability of Rigid PVC Foam Composites Filled with High Aspect Ratio Phlogopite Mica

High aspect ratio Phlogopite mica was used to enhance the dimensional stability and mechanical properties of extruded rigid Polyvinyl Chloride (PVC) foam. Mica was added to rigid PVC compound at different concentrations (0 - 20 wt%) and processed using a single screw profile extruder. PVC foam-Mica composites were characterized for their dimensional stability, and structural, thermal, and mechanical properties. Experimental results showed that the dimensional stability increased by 44% and heat resistance of the samples improved as the amount of mica increased in the composites. The storage modulus and tensile strength of the composites were also enhanced with the addition of mica. However, increasing the concentration of mica had no significant effect on the impact and flexural properties of the composites. SEM micrographs show good dispersion and orientation of the mica flakes along the cell walls of the PVC foam. Overall, the platy structure and physical properties of mica seemed to have played an important role in providing good interfacial bonding with the cell membranes of the foam, thus enhancing the dimensional stability of the PVC- Mica foam composites.

Recycling of Glass Fibers from Fiberglass Polyester Waste Composite for the Manufacture of Glass-Ceramic Materials

This work presents the feasibility of reusing a glass fiber resulting from the thermolysis and gasification of waste composites to obtain glass-ceramic tiles. Polyester fiberglass (PFG) waste was treated at 550℃ for 3 h in a 9.6 dm3 thermolytic reactor. This process yielded an oil (≈24 wt%), a gas (≈8 wt%) and a solid residue (≈68 wt%). After the polymer has been removed, the solid residue is heated in air to oxidize residual char and remove surface contamination. The cleaning fibers were converted into glass-ceramic tile. A mixture consisting of 95 wt% of this solid residue and 5% Na2O was melted at 1450℃ to obtain a glass frit. Powder glass samples (<63 μm) was then sintered and crystallized at 1013℃, leading to the formation of wollastonite-plagioclase glass-ceramic materials for architectural applications. Thermal stability and crystallization mechanism have been studied by Differential Thermal Analysis. Mineralogy analyses of the glass-ceramic materials were carried out using X-ray Diffraction.

Microstructure and Mechanical Properties of Mica Glass-Ceramics Prepared by Pressureless Sintering a Phlogopite and Various Additives

Mica glass-ceramics were prepared by pressureless sintering with a phlogopite and various additives as raw materials. The effects of CaF2 content, Li2O content, ZrO2 content, and sintering temperature on the microstructure and mechanical properties of the mica glass-ceramics were investigated by X-ray diffraction, scanning electron microscopy, and mechanical testing, respectively. The results show that the additive of ZrO2 has the best reinforcing effect on the flexural strength of the mica glass-ceramics. The smaller powder particles and the larger forming pressure result in the larger bulk density of the mica glass-ceramics samples. The main crystallite phases of samples with ZrO2 as additive were phlogopite and quartz with sintering temperature lower than 1120 ℃. The crystal phase of glass ceramics appeared fiberform and cross arranges with good lap. The highest value of flexural strength, 63.7 MPa, was shown on sample with 10wt% ZrO2 as additive and sintering temperature of 1120 ℃.

Mica Filled PVC Composites: Performance Enhancement in Dielectric and Mechanical Properties with Treated/Untreated Mica of Different Particle Size and Different Concentration

Polyvinyl chloride (PVC) of different grades is the second most commonly used polymer for fabrication of electric cables and wires after polyethylene. Cables of domestic and industrial use of various capacities are fabricated using different compounds of PVC. Mica is useful particulate filler extensively used to enhance the performance of many polymeric materials. It surface resistance and arc resistance improving its mechanical properties. In the present research work mica filled PVC composites of different concentrations were prepared using untreated and surface treated water ground mica of different particle size. Mica filled PVC composites were compounded for various compositions and test samples were prepared using compression moulding process. These samples were tested for electrical insulation and mechanical properties. The results shows enhancement in dielectric properties with improvement in Young’s modulus, stiffness, reduction in elongation at break and slight increase in shore D hardness of composites. Scanning electron microscopy was used to test the morphology of the samples which has shown proper distributions and adhesion of the filler mica in PVC matrix. There was some effect of surface treatment of mica on its mechanical and dielectric properties of the composite.

ANF/mica复合绝缘纸的制备及性能分析

以芳纶纳米纤维(ANF)为基体,天然云母(mica)为填料,通过真空辅助抽滤和热压技术制备了ANF/mica复合绝缘纸,并系统研究了复合绝缘纸的微观形貌、拉伸特性、电绝缘性能以及耐温性能。结果表明:mica与ANF在真空抽滤过程中有序叠加,mica碎片有效填补了纸张中的空隙,形成致密的“砖泥结构”,显著提高了复合绝缘纸的电气强度和绝缘性能。此外,纯ANF绝缘纸和ANF/mica-10复合绝缘纸的玻璃化转变温度均高于300℃,展现出优异的热稳定性。虽然mica的加入稍微降低了纯ANF绝缘纸的拉伸性能,但其绝缘强度和拉伸性能仍明显优于传统云母纸。

Evaluation of mechanical and wear properties of hybrid aluminium matrix composites

Hybrid metal matrix composites are important class of engineering materials used in automotive, aerospace and other applications because of their lower density, higher specific strength, and better physical and mechanical properties compared to pure aluminium. The mechanical and wear properties of hybrid aluminium metal matrix composites were investigated. Mica and SiC ceramic particles were incorporated into A1 356 alloy by stir-casting route. Microstructures of the samples were studied using scanning electron microscope （SEM）. The chemical composition was investigated through energy dispersive X-ray （EDX） detector. The results indicate that the better strength and hardness are achieved with A1/10SiC-3mica composites. The increase in mass fraction of mica improves the wear loss of the composites.

Effects of ZrO_2 on the Microstructure of a Mica Glass-ceramic

The effects of ZrO2 on the crystallinity of mica and microstructure of a machina- ble glassceramic were studied. It was found that ZrO2 is an effective nucleation agent in mica glass- ceramics. Stabilized by Ca2+, a lot of t--ZrO2 particles precipitate from ZrO2-mica glass-ceramics. The ZrO2 particles can effectively limit the growth of mica crystal and benefit the mechanical properties of glass-ceramics.

POLYPHASE METAMORPHISM AND INVERTED THERMAL GRADIENT IN THE LESSER HIMALAYA OF CENTRAL NEPAL: CONSTRAINTS FROM WHITE MICA COMPOSITIONS

The Lesser Himalaya in central Nepal consists of greenschist\|facies metasedimentary rocks, which are overthrust by the amphibolite\|facies rocks of the Higher Himalaya along the Upper Main Central Thrust (UMCT). Despite a number of works on metamorphism of the MCT zone and the Higher Himalaya, the low\|grade metamorphic rocks to the south of the MCT zone have not been studied yet.In the present study, an attempt was made to constrain the metamorphic events and thermal structure of the whole Lesser Himalaya by means of white mica (Ms) compositions. About 600Ms grains in 48 metapelitic samples from the Lesser Himalaya were analysed by the EPMA. Compositional zoning in individual Ms grains was checked by means of X\|ray compositional mapping. There exist wide intersample, intrasample and within grain compositional variations in Ms in the samples from the Lesser Himalaya. Sheared Ms phenocrysts in pegmatites and gneisses have compositions very close to that of the ideal muscovite. Detrital Ms show wide variation in phengite content, most of which are poor in phengite content, and are most probably derived from older higher\|grade metamorphic rocks.

Optimizing micaceous soil stabilization using response surface method

Micaceous soil is a problematic soil due to its low strength and poor ductility.In this context,the performances of micaceous soils were improved by applying a combination of granulated blast furnace slag,fiber and polymer additive.The dosages examined included 0%e30%mica,3%e15%slag and 0.25%e1.25%fiber by weight,and 0.1e0.5 g/L polymer additive.Most of the combinations were found to increase the material strength and ductility,yet to be optimized.To refine the dosage,response surface method was used to conduct experimental design and develop predictive models for material strength.The developed models formulate the material strength as a nonlinear function of dosages and,by interrogating it,can optimize additive contents in terms of target requirements.The models were verified through trials and can be used to determine dosages to upscale micaceous soils to field conditions.

花岗伟晶岩分异演化与含矿性评价——从造岩矿物组构视角

高演化稀有金属伟晶岩的成矿过程是复杂和苛刻的,涉及到岩浆-热液过程热历史、岩浆迁移路径与成矿空间、侵位环境的过冷程度以及岩浆组分中稀有金属元素的初始富集等条件。而伟晶岩的分带特征是其形成过程的一种综合体现,不论是伟晶岩区域分带还是伟晶岩内部结构分带,都反映了伟晶岩岩浆结晶分异过程中岩浆的性质与形成环境,而这同时也赋予了造岩矿物在组构上的特殊性,形成遗传代码,对其进行解密,从而能够用于示踪与评估花岗伟晶岩的演化程度与成矿潜力。对于区域伟晶岩群的成矿潜力评估,由于含矿熔体在组分上的跨度较大,随着远离母体花岗岩体距离的增大,伟晶岩群演化程度增加,熔体中铁镁质组分以及Ca、Ba、Sr等碱土金属含量迅速降低,而挥发分、助熔剂组分、碱金属含量在残余熔体中逐渐增加,长石、云母与石英在类别和组构上产生显著变化;其中长石向钾-钠端元演化,且钠长石相对钾长石占据主导地位,云母由黑云母向白云母以及锂白云母转变,石英阴极发光特征与晶体结构及微量元素成分也表现出规律性的变化。受矿物晶格的限制,长石的K/Rb、K/Cs以及云母的K/Rb、K/Cs、Nb/Ta等比值特征能有效区分不同矿化潜力的伟晶岩群。石英的阴极发光特征能够揭示其生长环境与历史,石英的Li、Al、Ti、Ge等微量元素组成可以用来区分不同类型的伟晶岩矿床,并提供关于岩浆演化和成矿过程的重要线索。伟晶岩内部分带的形成主要受成矿熔体规模、过冷度以及成矿空间的封闭性等因素的控制,但在初始熔体成分上可以具有较大的变化。其中强分带型稀有金属伟晶岩记录了完整的岩浆-热液演化过程,不同阶段石英、长石和云母在晶体形态、微观结构以及微量元素组成上都具有显著变化。弱分带型稀有金属伟晶岩(钠长石-锂辉石伟晶岩)的造岩矿物组分在伟晶岩内部变化不大,其受构造控制明显,在空间上与贫矿伟晶岩之间可具有较大的矿物组成差异,表明二者之间存在流动分异过程。而长距离(以更厚的地壳或大型拆离断层为标志)的熔体迁移正是形成超大型伟晶岩稀有金属矿床的有利要素。

锂渣物化特性及其碱激发制备人造集料实验

这是一篇陶瓷及复合材料领域的论文。伴随着我国锂矿冶炼规模增长,锂渣产量逐年增加,其资源化利用的必要性日趋凸显。为探明锂渣的物化性能及其作为胶凝材料制备人造集料的潜力,首先通过实验表征了宜春市锂云母锂渣和澳大利亚锂辉石锂渣的组成和性能,并分析其对碱激发性能的影响。其次,以氢氧化钠为碱激发剂,采用圆盘冷造粒法制备了两种锂渣人造集料,并测试了其抗压强度。最后,通过玻璃电极法、电感耦合等离子体质谱法、离子色谱法和分光光度法等实验论证了人造集料的环境风险。结果表明:锂云母锂渣的物化性质较锂辉石锂渣更适合用于碱激发制备人造集料,所制得的人造集料强度更高,液体浸出物也不具有环境危害性。

EFFECTS OF MATRIX MOLECULAR WEIGHT ON STRUCTURE AND REINFORCEMENT OF HIGH DENSITY POLYETHYLENE/MICA COMPOSITES

Three types of high-density polyethylene （HDPE） with different molecular weights （high, medium and low） were adopted to evaluate the influence of matrix molecular weight on the structure-property relation of injection-molded HDPE/mica composites through a combination of SEM, 2d-WAXS, DSC, DMA and tensile testing. Various structural factors including orientation, filler dispersion, interfacial interaction between HDPE and mica, etc., which can impact the macroscopic mechanics, were compared in detail among the three HDPE/mica composites. The transcrystallization of HDPE on the mica surface was observed and it exhibited strong matrix molecular weight dependence. Obvious transcrystalline structure was found in the composite with low molecular weight HDPE, whereas it was hard to be detected in the composites with increased HDPE molecular weight. The best reinforcement effect in the composite with low molecular weight HDPE can be understood as mainly due to substantially improved interfacial adhesion between matrix and mica filler, which arises from the transcrystallization mechanism.

PP/云母复合材料力学性能研究

研究了不同粒径云母、第三组份对PP材料力学性能影响,并用偏光显微镜观察了PP球晶。结果表明:用马来酸酐接技聚丙烯与WD 52偶联剂处理过的填充体系综合性能最优,并使PP球晶细化。

阿尔泰可可托海3号脉伟晶岩型稀有金属矿床云母和长石的矿物学研究及意义

可可托海3号脉伟晶岩型稀有金属矿床是阿尔泰造山带产出的规模最大的伟晶岩脉,其完美的同心环状结构分带举世闻名。云母和长石作为3号脉9个结构带的贯通性矿物,由外向内表现不同的结构和成分特征。其中,云母由白云母系列向锂云母系列演化,白云母呈黄-绿色中细粒→白色或绿色中粗粒-巨晶→白色或绿色书状集合体→白色或绿色中粗粒-巨晶,锂云母呈玫瑰紫中细粒鳞片状或楔状集合体,BSE图像下云母表现出成分分带及不平衡和交代结构;长石主要为钾长石和钠长石,及少量斜长石,钾长石主要呈块体产出,钠长石呈细粒→叶片状→薄片状产出。本次研究通过电子探针（EMPA）和激光剥蚀等离子质谱（LA-ICP-MS）获得3号脉各结构带云母和长石的主微量成分。3号脉云母具有高Li（249×10-6~35932×10-6）、Rb（1240×10-6~22825×10-6）、Cs（35.9×10-6~13980×10-6）、Ta（13.3×10-6~447×10-6）含量、低K/Rb值（4.23~59.4）和K/Cs值（6.53~2368）,钾长石具有低K/Rb值（35.4~1865）,且由外向内,随K/Rb值降低,云母的Li、Rb、Cs、F、Ta含量升高,表明3号脉是一个由外向内结晶的分异演化程度较高的伟晶岩脉。另外,连续相邻结构带中云母和长石的主微量成分呈振荡变化,该现象主要受熔体不混溶过程的控制,也受矿物结晶不平衡影响,而熔体不混溶过程也是控制3号脉结构分带的机制之一。外部带（I-IV带）和内部带（V-VIII带）的云母和碱性长石在成分（FeO、Li、Rb、Cs、F、Ta含量和K/Rb值及K/Cs值）和结构（不平衡和交代结构）上具有明显差异,内部带演化程度明显加大,流体组分比例升高,表明体系由以熔体为主的阶段（外部带）进入以熔流体为主相对不稳定的阶段（外部带）。结合野外观察的证据,促使体系在IV带和V带间发生突然转变而进入熔流体阶段的是一个泄压事件。

硅酸盐填充ABS复合材料的性能研究

以固相ABS三单体接枝物 (ABS g VM)作为相容剂 ,分别采用云母和高岭土对ABS进行填充改性。研究了填料用量对ABS复合材料的力学性能和动态力学性能的影响。结果表明 ,云母以片层状结构分布于ABS中 ,可有效提高ABS的强度和刚度 ,具有较好的综合力学性能 ;

云母基复合绝缘材料研究进展

云母基复合绝缘材料性能优异,是电气行业应用广泛的绝缘材料之一。综述了传统云母基复合绝缘材料云母纸、云母板、云母带的研究现状及存在的主要问题,提出了我国云母基复合绝缘材料的发展趋势。以芳纶纤维增强云母基复合绝缘材料为例,综述了新型云母基复合绝缘材料的研究进展,并对我国新型云母基复合绝缘材料的发展提出了建议。

云母/交联聚苯乙烯复合材料制备及沿面闪络性能

交联聚苯乙烯具有优异的电气性能、力学性能和可加工性能，已作为高压绝缘材料得到了重要应用。随着脉冲功率技术向小型化方向发展，对交联聚苯乙烯真空沿面闲络性能提出了更高要求。以苯乙烯为单体，二乙烯基苯为交联剂，偶氨二异丁腈为引发剂，采用超声波分散技术将不同质量分数的云母均匀分散于溶液体系中，通过原位自由基聚合制备出云母／交联聚苯乙烯复合材料。采用红外光谱、电子扫描显微镜等对材料组成和形貌进行了表征，采用短脉冲高压测试平台研究了云母对交联聚苯乙烯真空沿面闲络性能的影响。结果表明，当云母质量分数低于5％时，复合材料中云母为均匀分散状态，随着掺杂量进一步提升，出现了明显的团聚现象；当云母质量分数为35％～5％之间时，真空沿面闲络击穿电压和耐电寿命较交联聚苯乙烯得到了明显提升。

环氧-云母复合绝缘固化过程介电响应特性

为研究环氧-云母复合绝缘固化工艺条件对大型发电机绝缘质量影响的机理,采用频域谱法对电机线棒试品进行宽频介电谱测试。根据介电响应理论推导出介质损耗因数随频率和温度变化的关系式,同时实验研究了不同固化温度、固化时间下的介电参数频域特性。结果表明,170℃完全固化后的绝缘体系的介电响应特性要优于150℃和160℃时未达到完全固化的绝缘体系,固化后绝缘体系中小分子交联聚合成大分子,使能发生固化的极性分子大大减少,整体损耗也小于150℃和160℃下的损耗,且完全固化后的试样中各频率对应的损耗散点图也明显有一个收敛的趋势。研究表明,随着固化程度的增加,介质中容易发生转向极化的小分子逐渐减少,使同等频率下的松弛损耗相对于未固化时的损耗大幅度减小,固化后环氧-云母复合绝缘体系的介电性能有大幅度提高。

PA-6/云母复合材料性能研究

采用熔融共混法制备出了尼龙-6/云母复合材料,研究了云母的加入量对复合材料力学性能的影响。结果表明:随着云母量的增加,尼龙-6/云母复合材料的冲击强度和拉伸强度均呈现出先增加后降低的趋势,而弯曲模量呈增加趋势;云母的加入有助于提高PA-6基体的热稳定性。