Effect of overheating-induced minor addition on Zr-based metallic glasses

Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin responsible for the variation of properties remains poorly understood.In the present work,we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins.Specifically,we quenched the melt at different temperatures ranging from 1.1Tl to 1.5Tl(Tl is the liquidus temperature)to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating.We found that glass transition temperature,Tg,increases by as much as 36 K,and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5Tl.The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys.The incorporated oxygen and silicon can both enhance the interactions between atoms,which renders the cooperative rearrangements of atoms difficult,and thus enhances the kinetic stability of the MGs.

Corrosion and in vitro cytocompatibility investigation on the designed Mg-Zn-Ag metallic glasses for biomedical application

In the present work,seven Mg-Zn-Ag alloys with the nominal composition of Mg_(96-x)Zn_(x)Ag_(4)(x=17,20,23,26,29,32,35 in at.%)were prepared by induction melting and single-roller melt-spinning.The X-ray diffraction(XRD)analyses indicate the metallic glasses with three composition of Mg_(73)Zn_(23)Ag_(4),Mg_(70)Zn_(26)Ag_(4),and Mg_(67)Zn_(29)Ag_(4)were obtained successfully.The differential scanning calorimetry(DSC)measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis.The maximum glass transition temperature(Trg)was found to be 0.525 with a composition close to Mg_(67)Zn_(29)Ag_(4),which results in the best glass-forming ability.Moreover,the immersion test in simulated body fluid(SBF)demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses.The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content.The sample Mg_(67)Zn_(29)Ag_(4)has the lowest corrosion rate of 0.19mm/yr,which could meet the clinical application requirement well.The in vitro cell experiments show that the Madin-Darby canine kidney(MDCK)cells cultured in sample Mg_(67)Zn_(29)Ag_(4)and its extraction medium have higher activity.However,the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma(RD)tumor cells.The present investigations on the glass-forming ability,corrosion behavior,cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.

Unveiling the early stage evolution of local atomic structures in the crystallization process of a metallic glass

The early stage evolution of local atomic structures in a multicomponent metallic glass during its crystallization process has been investigated via molecular dynamics simulation.It is found that the initial thermal stability and earliest stage evolution of the local atomic clusters show no strong correlation with their initial short-range orders,and this leads to an observation of a novel symmetry convergence phenomenon,which can be understood as an atomic structure manifestation of the ergodicity.Furthermore,in our system we have quantitatively proved that the crucial factor for the thermal stability against crystallization exhibited by the metallic glass is not the total amount of icosahedral clusters,but the degree of global connectivity among them.

Coupling of quasi-localized and phonon modes in glasses at low frequency

Boson peak of glasses,a THz vibrational excess compared to Debye squared-frequency law,remains mysterious in condensed-matter physics and material science.It appears in many different kinds of glassy matters and is also argued to exist in damped crystals.A consensus is that boson peak originates from the coupling of the(quasi)-localized non-phonon modes and the plane-wave-like phonon modes,but the coupling behavior is still not fully understood.In this paper,by modulating the content of localized modes and the frequencies of phonon modes,the coupling is clearly reflected in the localization and anharmonicity of low-frequency vibrational modes.The coupling enhances with increasing cooling rate and sample size.For finite sample size,phonon modes do not fully intrude into the low frequency to form a dense spectrum and they are not sufficiently coupled to the localized modes,thus there is no Debye level and boson peak is ill-defined.This suggestion remains valid in the presence of thermal motions induced by temperature,even though the anharmonicity comes into play.Our results point to the coupling of quasi-localized and phonon modes and its relation to the boson peak.

Magnetic and magnetocaloric effect of Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass

Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass exhibited excellent magnetic refrigeration material with a wide temperature range and high refrigeration capacity(RC)was reported.Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass was observed with typical spin glass behavior around 15.5 K.In addition,we find that the magnetic entropy change(-△S_(M))originates from the sample undergoing a ferromagnetic(FM)to paramagnetic(PM)transition around 20 K.Under a field change from 0 T to 7 T,the value of maximum magnetic entropy change(-△S_(M)^(max))reaches 12.5 J/kg·K,and the corresponding value of RC reaches 487.7 J/kg in the temperature range from 6 K to 60 K.The large RC and wide temperature range make the Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass be a promising material for application in magnetic refrigerators.

Effect of high-energy Ne ions irradiation on mechanical properties difference between Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5)metallic glass and crystalline W

In this paper,high-energy Ne ions were used to irradiate Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) metallic glass(MG)and crystalline W to investigate their difference in mechanical response after irradiation.The results showed that with the irradiation dose increased,the tensile micro-strain increased,nano-hardness increased from 7.11 GPa to 7.90 GPa and 8.62 GPa,Young’s modulus increased,and H3/E2 increased which indicating that the plastic deformability decreased in crystalline W.Under the same irradiation conditions,the Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG still maintained the amorphous structure and became more disordered despite the longer range and stronger displacement damage of Ne ions in Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG than in crystalline W.Unlike the irradiation hardening and embrittlement behavior of crystalline W,Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG showed the gradual decrease in hardness from 6.02 GPa to 5.89 GPa and 5.50 GPa,the decrease in modulus and the increase in plastic deformability with the increasing dose.Possibly,the irradiation softening and toughening phenomenon of Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG could provide new ideas for the design of nuclear materials.

Novel sandwich structured glass fiber Cloth/Poly(ethylene oxide)-MXene composite electrolyte

Recently,poly(ethylene oxide)(PEO)-based solid polymer electrolytes have been attracting great attention,and efforts are currently underway to develop PEO-based composite electrolytes for next generation high performance all-solid-state lithium metal batteries.In this article,a novel sandwich structured solid-state PEO composite electrolyte is developed for high performance all-solid-state lithium metal batteries.The PEO-based composite electrolyte is fabricated by hot-pressing PEO,LiTFSI and Ti_(3)C_(2)T_(x) MXene nanosheets into glass fiber cloth(GFC).The as-prepared GFC@PEO-MXene electrolyte shows high mechanical properties,good electrochemical stability,and high lithium-ion migration number,which indicates an obvious synergistic effect from the microscale GFC and the nanoscale MXene.Such as,the GFC@PEO-1 wt%MXene electrolyte shows a high tensile strength of 43.43 MPa and an impressive Young's modulus of 496 MPa,which are increased by 1205%and 6048%over those of PEO.Meanwhile,the ionic conductivity of GFC@PEO-1 wt%MXene at 60℃ reaches 5.01×10^(-2) S m^(-1),which is increased by around 200%compared with that of GFC@PEO electrolyte.In addition,the Li/Li symmetric battery based on GFC@PEO-1 wt%MXene electrolyte shows an excellent cycling stability over 800 h(0.3 mA cm^(-2),0.3 mAh cm^(-2)),which is obviously longer than that based on PEO and GFC@PEO electrolytes due to the better compatibility of GFC@PEO-1 wt%MXene electrolyte with Li anode.Furthermore,the solid-state Li/LiFePO_(4) battery with GFC@PEO-1 wt%MXene as electrolyte demonstrates a high capacity of 110.2–166.1 mAh g^(-1) in a wide temperature range of 25–60C,and an excellent capacity retention rate.The developed sandwich structured GFC@PEO-1 wt%MXene electrolyte with the excellent overall performance is promising for next generation high performance all-solid-state lithium metal batteries.

A group of ductile metallic glasses prepared by modifying local structure of icosahedral quasicrystals

Inspired by research into the association between icosahedral local orders and the plasticity of metallic glasses(MGs),beryllium(Be) is added to the icosahedral quasi-crystal forming alloy Zr40Ti40Ni20. In this way, bulk metallic glasses(BMGs) with favorable compressive plasticity are fabricated. Therein, the icosahedral quasi-crystalline phase is the main competing phase of amorphous phases and icosahedral local orders are the main local atomic motifs in amorphous phases.The alloys of(Zr40Ti40Ni20)76Be24and (Zr40Ti40Ni20)72Be28with their greater plastic strain capacity show similar characteristics to highly plastic amorphous systems: The serrated flow of compression curves always follows a near-exponential distribution. The primary and secondary shear bands intersect each other, bifurcate, and bend. Typical vein patterns are densely distributed on the fracture surfaces. The relaxation enthalpy of four MGs is linearly correlated with the plastic strain, that is, the greater the relaxation enthalpy, the larger the plastic strain.

Structural origin for composition-dependent nearest atomic distance in Cu–Zr metallic glass

We systematically investigate the structures of Cu–Zr metallic glass(MG) by varying the Cu concentration in classic molecular-dynamics simulation. From the pair distribution functions(PDFs), it is found that the nearest atomic distance between Zr atom and Zr atom increases significantly after adding Cu, which is related to the composition-dependent coordination behavior between Cu atom and Zr atom in the nearest neighbors. The portion of PDF related to the nearest connection is decomposed into the contributions from quadrilateral structure, pentagonal structure, hexagonal structure,and heptagonal bipyramid structure. Although the population of denser structures, i.e. 5-, 6-, and 7-number sharing ones,increases with Cu addition increasing, the connection distances between the central atoms in all these bipyramids increase for Zr–Zr pairs, leading to the expansion of Zr–Zr nearest atomic distance. These results unveil the effect of the interplay between chemical interaction and geometric packing on the atomic-level structure in Cu–Zr metallic glasses.

熔体过热度对Zr基非晶合金力学性能和热稳定性的影响

采用吸铸法制备Zr_(70)Cu_(13.5)Ni_(8.5)Al_(8)非晶合金,采用同步差示扫描量热仪(DSC)和万能试验机对非晶合金显微结构进行表征和力学性能测试,并利用XRD和SEM对试样的相组成和剪切带观察。研究发现:随着吸铸功率增加,热稳定性、玻璃形成能力不断提高;Zr_(70)Cu_(13.5)Ni_(8.5)Al_(8)非晶合金的锯齿流变现象越明显,综合力学性能越好,其中吸铸功率8 kW时,试样的屈服强度、抗压强度和塑性达到最值,室温综合力学性能最好,且剪切带分布情况最好,但是继续提高吸铸功率,力学性能反而变差。

铋酸盐封接玻璃的研究及其连接应用现状

无铅低温封接玻璃由于具有绿色安全、成本低、封接温度低等优势,被广泛应用于航空航天、电真空、集成电路等领域。在磷酸盐、钒酸盐、硼酸盐和铋酸盐等多种封接玻璃体系中,因铋与铅具有相似的性质特点,使得铋酸盐玻璃成为最有可能替代铅酸盐玻璃的绿色玻璃钎料。综述了铋酸盐玻璃的成分和性能调控、网络结构的研究现状,介绍了目前使用铋酸盐封接玻璃进行金属、陶瓷同质/异质材料连接的研究进展,最后对未来的发展趋势进行了展望。

Li_(2)O/Na_(2)O对YAS微晶玻璃结构、析晶与力学性能的影响

透明微晶玻璃由于优异的力学性能被广泛应用于电子领域。本文采用熔融法制备了不同质量分数Li_(2)O和Na_(2)O的Y_(2)O_(3)-Al_(2)O_(3)-SiO_(2)(YAS)微晶玻璃,通过Raman、DSC、XRD、FESEM、UV-VIS-NIR等测试方法研究了其结构特征、析晶与力学性能。结果表明:当碱金属氧化物R_(2)O(R=Li,Na)总量保持不变,随着Li_(2)O取代Na_(2)O含量的增加,YAS微晶玻璃的转变温度、软化温度和结晶峰温度逐渐降低,Q^(4)基团对应的含量逐渐减少,说明Li_(2)O作为网络外体使YAS微晶玻璃结构逐步解聚,玻璃的析晶能力逐渐增强。在同一热处理制度下,随着Li_(2)O取代量的增加,YAS微晶玻璃维氏硬度显著提升,而透过率明显下降。在680℃/10 h+750℃/1 h热处理制度下,可以制备出晶体大小一致且分布均匀的以钇稳定氧化锆为主晶相的透明YAS微晶玻璃,此时2%(质量分数,下同)Na_(2)O+4%Li_(2)O YAS微晶玻璃具有良好的综合性能,如维氏硬度为646 HV,断裂韧性为1.07 MPa·m^(1/2),透过率为85.7%,在诸多领域具有巨大的应用潜力。

中轻度重金属污染农田土壤的时空特征及改良

为研究农田土壤重金属与速效养分的时空特征以及氮磷增效剂对农田土壤重金属的影响,本试验以受中、轻度污染的酸性棕壤和典型潮土为研究对象,采用田间试验、盆栽试验与室内分析相结合的方法进行研究。结果表明:农田土壤中Cd、Cu、Pb、Zn 4种重金属元素含量在0~20 cm土层显著高于深层土壤;棕壤0~20 cm土层Cd含量超标204%,潮土0~20 cm土层Cd、Zn含量分别超标104%、419%;农田土壤0~20 cm土层重金属有效态含量占比高于深层土壤,棕壤中重金属有效态含量占比高于潮土。棕壤0~20 cm土层全氮、碱解氮、铵态氮、硝态氮、有效磷和速效钾含量均显著高于深层土壤,且随土壤深度增加呈逐渐减小趋势,而潮土中仅全氮、碱解氮和有效磷含量显著高于深层土壤;农田土壤速效养分随时间波动变化,其中硝态氮和铵态氮波动幅度最大,最大变异系数分别为44.1%和47.3%。受污染农田土壤的小麦植株体内Cd、Pb、Cu主要积累在叶片,Zn主要积累在籽粒;不同重金属元素从小麦茎、叶向籽粒的迁移程度差异较大,其中Cd迁移率最小,Zn迁移率最大。氮磷增效剂能显著减少棕壤中重金属有效态含量,底肥+氢醌+双氰胺+生物炭处理的有效态Cd、Cu、Pb、Zn含量较对照(仅加底肥,不加氮磷增效剂)处理分别显著降低24.7%、19.5%、23.7%、18.1%,而在潮土中施用效果不明显。研究表明,农田土壤重金属与土壤养分之间存在一定的相关性,且在土壤垂直分布上大体一致,土壤类型是氮磷增效剂对重金属有效态产生不同影响的重要因素。

土壤侵蚀对重金属迁移的作用规律与机制研究进展

[目的]揭示土壤侵蚀作用下重金属的迁移规律,阐明重金属在土壤侵蚀作用下的迁移机制,为重金属的污染防治提供科学指导。[方法]基于国内外有关土壤侵蚀作用下重金属迁移的文章,从土壤性质、重金属性质、环境因子3方面就土壤侵蚀对重金属迁移的作用规律与机制进行系统研究。[结果](1)侵蚀作用下土壤重金属主要以颗粒态形式进行横向/纵向迁移,溶解态重金属迁移占比小但活性强,侵蚀造成沉积区的泥沙特性与侵蚀区土壤存在差异,可能影响重金属富集特征的空间分布格局;(2)土壤pH、有机质和黏粒含量越高,吸附重金属的能力越强,重金属被释放迁移的能力越弱;(3)土壤重金属的赋存形态对其迁移方式有影响,一般溶解态重金属主要来源于有效态,而相对稳定的残渣态通常以颗粒态形式迁移;(4)降雨、地形、植被等环境因子影响泥沙颗粒的迁移过程,并优先迁移细颗粒,使泥沙粒径分布随迁移路径呈一定的变化规律。[结论]侵蚀作用下重金属迁移受土壤—重金属性质及环境因子等多种因素影响,未来研究可重点关注不同地质背景与污染成因条件下土壤侵蚀对重金属迁移过程的影响;不同粒径土壤颗粒的重金属赋存形态异质性研究;喀斯特地下漏失对重金属迁移的作用机理,探究不同侵蚀条件下重金属地表流失与地下漏失的分配机制。

施苯菌灵抑制丛枝菌根真菌对污染土壤-玉米系统镉迁移的影响

为探讨土壤丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)对污染土壤–作物系统Cd迁移行为的影响,采用云南兰坪铅锌矿周边重金属污染的土壤,开展室内试验,施杀真菌剂(苯菌灵)特异性抑制土壤土著AMF,研究抑制AMF对玉米生长、Cd含量与累积量、土壤Cd淋溶流失的影响。结果表明:(1)施苯菌灵显著抑制土壤AMF生长,导致AMF侵染率、孢子数、土壤球囊霉素相关蛋白(Glomalin related soil protein,GRSP)含量显著降低;并显著影响玉米生长与矿质营养,玉米地上部生物量、叶绿素与磷含量增加,而地上部氮钾含量降低。(2)施苯菌灵促进Cd向玉米根部和地上部迁移,主要富集在玉米地上部,导致玉米地上部的Cd含量和累积量显著增加。(3)施苯菌灵导致10cm和20cm壤中流的Cd浓度显著增加。此外,土壤GRSP含量与玉米地上部Cd累积量和壤中流的Cd流失浓度均呈极显著负相关。研究结果表明,土壤土著AMF有助于抑制土壤Cd向植株地上部迁移,减少壤中流Cd的流失浓度,降低污染土壤–作物系统Cd的环境迁移。

深冷循环热处理下锆基金属玻璃的回春行为调控

研究Zr_(55)Cu_(30)Ni_(5)Al_(10)(摩尔分数,%)金属玻璃在深冷循环处理过程中的回春行为。实验发现,随着循环次数的增加,样品的回春程度更高,表现为更高的弛豫焓与更低的密度。回春程度经200次循环后逐渐饱和,这可能与非晶结构中有限的自由体积含量有关。同时,高循环次数下的样品硬度更低,塑性更好,这与其剪切转变区体积增大有关。此时,更低的剪切面形成能有利于多重剪切带的形成。此外,还发现自由体积含量与样品塑性应变及剪切转变区体积呈线性关系。分子动力学模拟结果还表明,在高冷速下回春程度高的样品会发生原子体积的饱和。

基于融合策略的块体金属玻璃形成能力预测

提出一种融合策略来提高随机森林(RF)、k近邻(KNN)、梯度提升决策树(GBDT)和极端梯度提升(XGBoost)模型预测块体金属玻璃(BMGs)形成能力(GFA)的准确性。该策略使用训练好的卷积神经网络(CNN)模型提取来特征向量,且合金的成分信息是唯一的输入变量,不需要通过实验获得其他物理和化学特性。此外,通过网格搜索方法和k折交叉验证对RF、KNN、GBDT和XGBoost模型的超参数进行了优化。结果表明,本文作者提出的4种融合模型CNN-RF、CNN-KNN、CNN-GBDT和CNN-XGBoost比上述4种机器学习模型(即RF、KNN、GBDT和XGBoost模型)预测精度更高,这表明训练好的CNN模型比人工特征提取更为高效。此外,与已报道的机器学习模型和GFA判据相比,本文作者提出的融合模型可以更精准地预测金属玻璃的形成能力。

掺银硫系玻璃光电探测器响应波长特性研究

由于硫系玻璃具有良好的光学性质,在非线性光学等方面研究广泛,但基于硫系玻璃光电探测器的相关研究却很少。本文利用真空共热蒸发技术制备了不同掺银比例的硫系玻璃薄膜作为半导体膜层结构,并设计构建了金属-绝缘体-半导体结构的自供电光电探测器,探究了该光电探测器的响应光谱范围。结果表明,该探测器对可见光到近红外区域的光均有响应。针对掺银硫系玻璃光电探测器在635 nm波长激光下,研究了探测器响应电压与激发功率之间的关系。当激光功率小于10 mW时,探测器响应电压与激发功率线性相关;当激光功率大于10 mW时,探测器响应电压逐渐饱和。探测器的上升和衰减时间分别为3.932 s和1.522 s。本研究为硫系玻璃材料在自供电光电探测器领域的应用提供了证明。

腾冲火成岩分布地区流域重金属元素迁移富集规律

环境中的重金属污染一般与人类活动有关,但流域内自然来源的重金属影响也不容忽视。火成岩分布地区的地质高背景往往含有较高的过渡金属元素,其中以Cr、Ni、Cu含量较高,主要赋存在流域内的土壤和沉积物中,其对流域生态环境会造成持续性危害。为了解火成岩地区土壤和沉积物的重金属元素的迁移富集规律,为治理环境污染,保护人类生活环境提供一定意义的科学认识和参考依据。本研究以云南腾冲火成岩分布地区的龙川江和沙河两个流域为研究对象,系统采集基岩、土壤和沉积物样品进行研究。结果表明:两个流域内沉积物和土壤的矿物组成主要有石英、长石、黏土矿物及少量碳酸盐,风化过程中随长石的减少,黏土类矿物显著增加,重金属元素也随黏土矿物的增加而富集,Cr、Ni在土壤中富集,与总黏土矿物含量呈线性关系(Cr:R^(2)=0.3817;Ni:R^(2)=0.5797),沉积物中Cr、Ni、Zn、Pb含量与高岭石、云母和伊利石混层的含量呈线性关系(R^(2)=0.43~0.72)。重金属Cu、Zn、Pb在沉积物中富集,其传质系数在龙川江沉积物中与高岭石、云母和伊利石混层的含量呈线性关系(R^(2)=0.58~0.79)。黏土类矿物对重金属元素的富集和迁移具有重要作用。

钆含量对Fe-B-Nb-Gd非晶合金磁学性能和氧化机制的影响规律

研究了Gd含量对(Fe_(73)B_(22)Nb_(5))_(100–x)Gd_(x)(x=0,0.5,1.0,1.5,2.0)合金非晶形成能力、热稳定性和磁学性能的影响规律,并对比分析了非晶氧化机制.通过添加Gd元素,合金的原子尺寸差超过13%,构型熵增大了30%,提升了合金的非晶形成能力.随着Gd含量的增大,过冷液相区范围达到73 K,热稳定性得到明显增强.Gd元素导致合金局部各向异性受到限制,准位错偶极子型缺陷密度降低.这有效减少了阻碍磁畴壁旋转的钉扎位点,提高合金软磁性能.此外,Gd元素使得非晶在氧化过程中对温度的变化更为敏感,达到最大氧化速率的温度降低了15 K,但是并未恶化其抗氧化性能.Gd原子受结合能影响向表层迁移,形成的富Gd氧化物填充了表层缺陷,占据了大量顶部空间,合金表面附近的结构更加致密.这种结构减少了氧原子通过微观组织界面进行扩散的通道,有助于增强抗氧化性能.