EPR and Magnetic Susceptibility Studies of Cr^(3+) Ions in the 70TeO_2·25B_2O_3·5PbO Glass Matrix

By using EPR and magnetic susceptibility measurements, the Cr ion distribution in the xCr2O3.(1-x)[70TeO2·25B2O3·5PbO] glasses with 0＜x≤20 mol% was studied. EPR investigation evidencedthe presence of Cr3+ ions in agreement with the experimentally obtained atomic magnetic moment values. For concentrations x≤3 mol%, the isolated Cr3+ ions coexist with those coupledby dipole-dipole interactions. For x＞3 mol%, the Cr3+ ions participate in superexchange interactions and are predominantly antiferromagnetically coupled.

Ballistic performance of tungsten particle/metallic glass matrix composite long rod

In the present manuscript numerical analysis on the ballistic performance of a tungsten particle/metallic glass matrix(WP/MG) composite rod is conducted by integrating with related experimental investigations. In the corresponding finite element method(FEM) simulations a modified coupled thermomechanical constitutive model is employed to describe the mechanical properties of metallic glass(MG)matrix, and geometrical models of the WP/MG composite rod are established based on its inner structure. The deformation and failure characteristics of the rod and target materials are analyzed in detail,and the influences of various factors on the ballistic performance of the WP/MG composite long rod are discussed. Related analysis demonstrates that the penetrating performance of the WP/MG rod is similar to that of the tungsten fiber/metallic glass matrix(WF/MG) composite long rod, i.e., a "self-sharpening" behavior also occurs during the penetration process, and correspondingly its penetrating capability is better than that of the tungsten heavy alloy(WHA) rod. However, the mass erosion manner of the WP/MG rod is different and the erosion is relatively severe, thus its penetrating capability is a little lower compared with that of the WF/MG one. Moreover, the impact velocity and the target strength have significant influences on the ballistic performance of the WP/MG composite rod, whereas the effect of initial nose shape is very little.

Probabilistic Modelling of Microstructural Evolution in Zr Based Bulk Metallic Glass Matrix Composites during Solidification in Additive Manufacturing

Bulk metallic glass and their composites (BMGMCs) are a new class of materials which possess superior mechanical properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure under applied force. Their behavior is dubious, unpredictable and requires extensive experimentation to arrive at conclusive results. In present study, an effort has been made to design bulk metallic glass matrix composites by the use of modeling and simulation. A probabilistic cellular automaton (CA) model is developed and described in present study by author which is used in conjunction with earlier developed deterministic model to predict microstructural evolution in Zr based BMGMCs in additive manufacturing liquid melt pool. It is elaborately described with an aim to arrive at quantitative relations which describe process and steps of operations. Results indicate that effect of incorporating all mass transfer and diffusion coefficients under transient conditions and precise determination of probability number play a vital role in refining the model and bringing it closer to a level that it could be compared to actual values. It is shown that proposed tailoring can account for microstructural evolution in metallic glasses.

Corrosion Behavior of Fe-based Bulk Metallic Glass and In-situ Dendrite-reinforced Metallic Glass Matrix Composites in Acid Solution

The corrosion behavior study was conducted on a novel Fe77 Mo5P9C7.5 B1.5 in-situ metallic glass matrix composite （MGMC）. This composite sample was developed by introduction of bcc a-Fe dendrites as reinforcing phase. The corrosion behavior of this composite was compared to its monolithic counterpart and other Fe-based alloys such as 304L and 2304L stainless steels. The corrosion resistance of MGMCs in H2SO4 solution shows inferior to that of other Fe-based alloys. Experiments suggest that Fe-BMGs samples possess better corrosion resistance property than that of Fe-MGMCs. The possible underlying reasons can be the inhomogeneity induced by the precipitation of a-Fe dendrites in the MGMCs.

CuZr-based bulk metallic glass and glass matrix composites fabricated by selective laser melting

Monolithic bulk metallic glass and glass matrix composites with a relative density above 98%were produced by processing Cu_(46)Zr_(46)Al_(8)(at.%)via selective laser melting(SLM).Their microstructures and mechanical properties were systematically examined.B2 CuZr nanocrystals(30-100 nm in diameter)are uniformly dispersed in the glassy matrix when SLM is conducted at an intermediate energy input.These B2 CuZr nanocrystals nucleate the oxygen-stabilized big cube phase during a remelting step.The presence of these nanocrystals increases the structural heterogeneity as indirectly revealed by mircrohardness and nanoindentation measurements.The corresponding maps in combination with calorimetric data indicate that the glassy phase is altered by the processing conditions.Despite the formation of crystals and a high overall free volume content,all additively manufactured samples fail at lower stress than the as-cast glass and without any plastic strain.The inherent brittleness is attributed to the presence of relatively large pores and the increased oxygen content after selective laser melting.

Effect of Cu content on microstructure and mechanical properties of in-situ β phases reinforced Ti/Zr-based bulk metallic glass matrix composite by selective laser melting(SLM)

In this study,non-toxic in-situβphases of reinforced Ti/Zr-based bulk metallic glass matrix composites(BMGCs)of(Ti_(0.65)Zr_(0.35))100-xCux(x=5,10,15 at.%)are fabricated via selective laser melting.The effect of Cu content on phase formation,microstructure,and mechanical properties is investigated.The average volume fraction and width of theβphase decreases with increasing Cu content,while a more amorphous phase and the(Ti,Zr)_(2)Cu phase forms.In the center zone of the molten pool,theβphase grows in the direction of the temperature gradient,and the amorphous phase distributes among theβphases.This occurs using:sphere morphology(for x=5),a more continuous elongated sphere and network morphology(for x=10),and network morphology(for x=15),respectively.In the edge zone of the molten pool,due to the smaller cooling rate and the existence of a partially molten zone,theβphase becomes coarser,and an amorphous phase forms for more continuous networks.Furthermore,the hardness improves significantly with increasing Cu content.No crack is found for x=5.Although the average volume fraction of theβphase for x=5 is about 90%,the compression yield strength is 1386±64 MPa,reaching to an average level of conventionally fabricated counterparts,due to finer microstructure,and twinning and martensitic transformation of theβphase.

Achieving work hardening by forming boundaries on the nanoscale in a Ti-based metallic glass matrix composite

Achieving work hardening in metallic glass matrix composites(MGMCs) is the key to the extensive use of these attractive materials in structural and functional applications.In this study,we investigated the formation of nanoscale boundaries resulted from the interaction between matrix and dendrites,which favors the work-hardening deformation in an in-situ Ti41Zr32Ni6 Ta7 Be14 MGMC with β-Ti dendrites in a glassy matrix at room temperature.The microstructures of samples after tension were observed by highresolution transmission electron microscopy(HRTEM) and X-ray diffraction(XRD).The work-hardening mechanism of the present composites involves:(1) appearance of dense dislocation walls(DDWs),(2)proliferation of shear bands,(3) fo rmation of boundaries on the nanoscale,and(4) interactions between hard and soft phases.A theoretical model combined with experimental data reveals the deformation mechanisms in the present work,proving that the in-situ dendrites with outstanding hardening ability in the glass matrix can provide the homogeneous deformation under tensile loading at room temperature.

Elastic deformation behavior of CuZrAlNb metallic glass matrix composites with different crystallization degrees

The room temperature brittleness has been a long standing problem in bulk metallic glasses realm.This has seriously limited the application potential of metallic glasses and their composites.The elastic deformation behaviors of metallic glass matrix composites are closely related to their plastic deformation states.The elastic deformation behaviors of Cu48-xZr48Al4Nbx（x=0,3at.%）metallic glass matrix composites（MGMCs）with different crystallization degrees were investigated using an in-situ digital image correlation（DIC）technique during tensile process.With decreasing crystallization degree,MGMC exhibits obvious elastic deformation ability and an increased tensile fracture strength.The notable tensile elasticity is attributed to the larger shear strain heterogeneity emerging on the surface of the sample.This finding has implications for the development of MGMCs with excellent tensile properties.

Stable structure of Zr_(49)Cu_(44)Al_7 metallic glass matrix composite with CuZr phase under high pressure up to 40.8 GPa

Ternary Zr49Cu44Al7 metallic glass matrix composite rods with CuZr nano-phase,exhibiting an elastic strain of 1.6% and a high strength of 1.78 GPa,have been manufactured. The structural evaluation of the ternary metallic glass matrix composite under high pressure has been investigated using angle dispersive X-ray diffraction with a synchrotron radiation source. The investigation shows that the amorphous matrix structure is stable under pressures up to 40.8 GPa at room temperature. No pressure induced CuZr nano-phase disappearing or growing was detected. According to the Bridgeman equation of state,the bulk modulus B0 =115.2 GPa has been obtained.

JOINING MECHANISMS OF β"-Al_2O_3 CERAMIC AND PYREX GLASS TO Al MATRIX COMPOSITE

The bonding of β″-Al2O3 and pyrex glass to A1 matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope （SEM）, energy dispersive X-ray fluorescence spectrometer （EDX）. It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding.

Optical Characteristics of Porous Glasses Matrix and Its Light-conducted Mechanism

The optical properties of matrix of porous glasses and phase-separated glasses were investigated by visible spectroscopy and infrared spectroscopy. The experimental results show that, both the porous glasses and phase-separated glasses have very good light transmission in visible light region that wavelenth is longer than 560nm. The micropores of porous glasses and the boron-rich phase of phase-separated glasses have strong Rayleigh scatter effects on the visible light, the largest scatter occurrs at 360-370nm; the thicker the glasses, the larger the light scattering. Thus, the pore size distribution and the size of heterogeneous micro zone in boron-rich phase of phase-separated glasses can be measured. After coupled into porours glasses, the most intense absorption of hydrated ions of 〔Co(H 2O) 6〕 2+ shifts from 508nm to 515nm. The production of the most intense absorption and the red shift were owed to Jahn-Teller effect of octahedral field formed by six H 2O molecular and perturbation effect resulted by microporous of porous glasses for its physics-chemical circumstance. As a result, the porous glasses are perfect optical function materials in visible region, which can be assembled by chemical method.

基于混合FTMM-SEA法的高速列车真空玻璃车窗隔声特性预测与分析

真空玻璃在轻质高隔声方面的性能优势尤为突出,将其用于高速列车车窗是轻量化高速列车车内噪声控制的新型解决方案。将声波在真空玻璃中的传播分解为沿真空层和沿声桥结构的两条独立传播路径,分别使用有限传递矩阵法(FTMM)和统计能量分析法(SEA)计算两条路径的声功率传递系数,建立基于混合FTMM-SEA法的真空玻璃车窗结构隔声量预测模型,并通过实测真空玻璃混响隔声量验证模型的准确性。进一步调查分析声桥结构刚度对耦合板间能量传递、真空玻璃隔声特性的影响。结果表明:减小声桥结构刚度是提高真空玻璃车窗隔声性能的一种有效的方法。与刚性声桥相比,柔性声桥具备更好的能量吸收能力与隔振特性。

Mg-Cu-Zn-Y-Zr bulk metallic glassy composite with high strength and plasticity

Mg65Cu20Zn5Y9Zr1 bulk metallic glass matrix composite with a diameter of 2 mm was produced by copper mold casting. Upon cooling the Mg65Cu20Zn5Y9Zr1 melt, Mg2Cu acicular crystalline phase precipitates uniformly with a size of about 20 μm long and 1 μm thick while the remaining melt undergoes glass transition. Room temperature compression tests revealed that the high fracture strength up to 830 MPa and the plastic strain of 2.4% before failure are obtained for the Mg-based bulk metallic glass matrix composite. The formation of the Mg2Cu phase was proposed to contribute to high strength and plastic deformation of the material.

Preparation and properties of GAGG:Ce/glass composite scintillation material

The translucent GGAG:Ce/glass composites are prepared successfully by ball-milling,tableting,and pressureless sintering.The thickness of composites is about 400μm.The x-ray diffraction(XRD),differential scanning calorimetry(DSC),density of composite materials are measured and discussed systematically.The scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)elemental mapping are employed to analyze the particle size,the shape of powders,and the distribution of GGAG:Ce particles in the glass matrix,respectively.The decay time,ultraviolet,(UV),x-ray excitation luminescence spectra,and temperature spectra are studied.The results show that the composite materials have high light output,good thermostability,and short decay time.The method adopted in this work is an effective method to reduce the preparation time and cost of the sample.The ultralow afterglow indicates that the composite materials have an opportunity to be used for x-ray detection and imaging.

温度对高硅氧基体玻璃纤维性能的影响及其机理探索

针对经石蜡型浸润剂涂覆后的高硅氧基体玻璃纤维原丝,在高温环境下性能、生产利用率下降的问题,深入研究了温度对其性能的影响规律,并对机理进行了讨论。采用红外、热重、扫描电镜等分析手段,对不同形态的高硅氧基体玻璃纤维原丝在不同温度、不同存放时间下的性能进行了表征。结果表明,随着温度的升高,浸取液碱性增强,机械性能下降,同时纤维丝表面晶体析出越多,且存在碳酸根。因此,可以得出,温度影响高硅氧基体玻璃纤维性能的根本原因,可能在于高温促进了纤维中Na^(+)运动,加快了其与纤维表面水分子中H+的离子交换,从而加速了纤维结构的破坏,导致性能下降。

Effects of Yb^3＋ in Er^3＋/Yb^3＋ Codoped Fluorophosphate Glasses

For the Er^3＋ /Yb^3＋ codoped fluorophosphate glasses, Judd-Ofelt theory is used to analyse the influence of YbF3 as not a sensitizer but an average component on the spectroscopic properties around 1530nm emission. The double roles of Yb^3＋, as a sensitizer and as an average component, are discussed. It is found that Yb^3＋ as an average component contributes to the increase of fluorescence lifetime, and Yb^3＋ as a sensitizer has the best sensitization when its concentration is 2.4 mol%.

陶瓷颗粒增强Zr基非晶合金复合材料高温变形行为研究

在非晶合金中添加第二相制备非晶合金复合材料能够有效地解决非晶合金室温脆性的问题,但第二相的引入对非晶基体高温变形行为造成的影响尚不明确。本研究在Zr_(55)Cu_(30)Al_(10)Ni_(5)非晶合金中添加两种不同的陶瓷颗粒Al_(2)O_(3)和Si_(3)N_(4),通过放电等离子烧结法制备了一系列不同体积分数的陶瓷颗粒增强Zr基非晶合金复合材料。通过进行高温压缩试验,并建立多颗粒随机分布模型进行数值模拟,对其高温变形行为进行了系统性研究。结果表明,在421℃时,两种复合材料都表现为应力过冲后应变硬化;在441℃时,Al_(2)O_(3)增强的复合材料表现为屈服后应变硬化,对于Si_(3)N_(4)增强复合材料,当第二相体积分数小于25%时表现为屈服后应变硬化,当第二相体积分数大于25%时材料却表现为应力过冲后应变硬化。两种非晶合金复合材料的高温变形行为差异与增强相形貌以及增强相颗粒团聚行为导致的第二相分布不均匀有关。

Fabrication and Characterization of Glass Fiber with SiC Reinforced Polymer Composites

Glass Fiber Reinforced Polymeric (GFRP) Composites are most commonly used as bumpers for vehicles, electrical equipment panels, and medical devices enclosures. These materials are also widely used for structural applications in aerospace, automotive, and in providing alternatives to traditional metallic materials. The paper fabricated epoxy and polyester resin composites by using silicon carbide in various proportions along with GFRP. The hand lay-up technique was used to fabricate the laminates. To determine the properties of fabricated composites, the tensile, impact, and flexural tests were conducted. This method of fabrication was very simple and cost-effective. Their mechanical properties like yield strength, yield strain, Young’s modulus, flexural modulus, and impact energy were investigated. The mechanical properties of the GFRP composites were also compared with the fiber volume fraction. The fiber volume fraction plays a major role in the mechanical properties of GFRP composites. Young’s modulus and tensile strength of fabricated composites were modelled and compared with measured values. The results show that composites with epoxy resin demonstrate higher strength and modulus compared to composites with polyester resin.

环氧乙烯基酯树脂/玻璃鳞片复合材料冲击韧性的影响因素

研究了树脂性能及含量、玻璃鳞片形状、球形填料以及表面活性剂等因素对树脂基玻璃鳞片复合材料的冲击韧性影响。发现树脂增韧以及含量增加可显著提升复合材料的冲击韧性;减小玻璃鳞片片径虽可有效提升材料冲击韧性,但会导致材料水蒸气渗透量增加,因此鳞片片径不宜小于0.4 mm;白炭黑含量在1.5 wt%时冲击韧性达到峰值;偶联剂含量不高于1 wt%时,冲击韧性随偶联剂含量提高而增长。

X射线荧光光谱法测定工业氧化铝中的微量元素

采用工业氧化铝系列标准样品,加Li_(2)B_(4)O_(7)-LiBO_(2)混合熔剂熔铸成玻璃样片,建立测定氧化铝微量元素(Ga_(2)O_(3)、ZnO、CaO、SiO_(2)、Fe_(2)O_(3)、TiO_(2)、K_(2)O和Na_(2)O)的X射线荧光光谱分析曲线。通过谱线校正消除谱线干扰,按照经验α系数法进行基体校正,消除样品中各元素的吸收增强效应,校准曲线精密度品质因子低于0.07。使用建立的分析曲线对样品各微量组分进行检测,结果表明:各组分检测值相对标准偏差介于0.53%~9.09%之间,检测结果误差在GB/T 6609.30—2009标准要求的允许范围内。该检验方法的检验结果达到了精密度和准确度要求,为指导工业生产以及实验室质量控制奠定了基础。