<Emphasis Type="Italic">In situ</Emphasis> synthesis of TiC reinforced Cu<Subscript>47</Subscript>Ti<Subscript>34</Subscript>Zr<Subscript>11</Subscript>Ni<Subscript>8</Subscript> bulk metallic glass composites

In situ synthesized TiC particles and β-Ti dendrites reinforced Cu47Ti34Zr11Ni8 bulk metallic glass (BMG) composite ingots were prepared by the suction casting method.The ingots with diameters from 1 up to 4mm were successfully obtained. It was shown that introducing TiC micro-sized particles into the amorphous matrix did not disturb the glass forming ability (GFA) of the matrix,while the yield strength and ductility could be well improved.The phase constitution, microstructure and elements distribution in the composites were studied by OM, XRD, SEM and EDS.It was shown that the in situ synthesized TiC particles acting as heterogeneous nucleation sites promoted the precipitation of β-Ti dendrites, resulting in the formation of the TiC particles and β-Ti dendrites co-reinforced BMG composites. The compressive tests were employed to probe the yield strength and ductility of BMG composites.     

Room temperature plastic deformation behavior of ZrCuNiAl bulk metallic glasses

The Zr_62.55Cu_17.55Ni_9.9Al₁₀ bulk metallic glass (BMG) was prepared by using copper-mold suction-casting. X-ray diffraction and differential scanning calorimetry were utilized to determine its structure and thermal stability. Uniaxial compression and Rockwell indentation tests were adopted to study the plastic deformation behavior at room temperature. The results show that the glass transition temperature and the onset temperature of exothermic reaction of the BMG are 651.5 and 748 K, respectively. During the compression test, the BMGs undergo an engineering strain of about 2.5%, i.e., true strain of 2.8%, and then fracture. The BMGs deform via the formation and propagation of shear bands. Under indentation loading, the BMGs deform through the formation of radiation-like and circular shear bands. The circular shear bands form earlier than the radiation-like ones. The formation mechanism of shear bands in the BMGs was analyzed and discussed.     

Mg-Zn-Ce非晶合金力学与耐蚀性能的研究

镁合金作为生物可降解材料具有很多优势,但传统多晶镁合金腐蚀速率过快的问题限制了其更广泛的应用。与多晶镁合金相比,非晶态镁合金因具有独特的无定形结构,使其耐腐蚀能力比多晶镁合金的要好。采用铜辊甩带法制备得到了新型Mg_70−xZn₃₀Ce_x（x=2, 4, 6和8）非晶镁合金,并对其进行了力学性能和耐腐蚀性能的研究。结果表明：x为4和6时,Mg-Zn-Ce非晶合金的非晶形成能力最好;Ce的添加可以有效改善镁基非晶合金的脆性,使其弹性模量低于60 MPa,与人骨相似,从而能有效避免植入后因弹性模量过大导致的应力遮蔽效应的产生;同时,Ce的添加显著地提高了合金的耐腐蚀性,使其开路电位达到-0.2 V,腐蚀电流密度低至10^-6 A/cm²。     

Effect of trace Zn, P and Mg additions on microstructure and mechanical properties of Nb-Si-Ti alloys

The effects of Zn,P and Mg additions on the microstructure and mechanical properties of Nb-22Ti-3Si alloys were studied. The phases of Nbss and Nb_3Si presented in Nb-22Ti-3Si(AC1),Nb-22Ti-3Si-0.2Zn(AC2) and Nb-22Ti-3Si-0.2Mg alloys(AC3). The Nb-22Ti-3Si-0.2P(AC4) alloy consisted of Nbss,Nb_3Si network and eutectic cell of Nbss/α-Nb_5Si_3.By the addition of Zn,the Nb_3Si network was broken and the volume fraction of Nbss increased from 92%to 96%.The values of fracture toughness of the alloy AC2 at ambien...     

Microstructure and mechanical properties of a novel Zr-based bulk metallic glass composite

Zr48.5Cu46.5Al5 bulk metallic glass （BMG） composites with diameters of 3 and 4 mm were prepared through suction casting in an arc melting furnace by modulating the alloy composition around the monothetic BMG composition of the high glass forming ability. Microstructural characterization reveals that the composites contain micron-sized CuZr phase with martensite structure, as well as nano-sized Zr2Cu crystalline particles and Cu10Zr7 plate-like phase embedded in an amorphous matrix. Room temperature compression tests showed that the composites exhibited significant strain hardening and obvious plastic strain of 7.7% for 3 mm and 6.4% for 4 mm diameter samples, respectively.     

Selective interfacial bonding and thermal conductivity of diamond/Cu-alloy composites prepared by HPHT technique

Cu-based and Cu-alloy-based diamond composites were made by high-pressure-high-temperature (HPHT) sintering with the aim of maximizing the thermal conductivity of the composites. Improvements in interfacial bonding strength and thermo-physical properties of the composites were achieved using an atomized copper alloy with minor additions of Co, Cr, B, and Ti. The thermal conductivity (TC) obtained exhibited as high as 688 W·m-1·K-1, but also as low as 325 W·m-1·K-1. A large variation in TC can be rationalized by the discrepancy of diamond-matrix interfacial bonding. It was found from fractography that preferential bonding between diamond and the Cu-alloy matrix occurred only on the diamond {100} faces. EDS analysis and Raman spectra suggested that selective interfacial bonding may be attributed to amorphous carbon increasing the wettability between diamond and the Cu-alloy matrix. Amorphous carbon was found to significantly affect the TC of the composite by interface modification.     

LiNiPO4前驱体固相反应合成动力学及电容性能

以氢氧化锂、磷酸二氢铵和醋酸镍为原料,以聚乙二醇PEG-400为表面活性剂,采用前驱体固相活化法制备LiNiPO4纳米晶材料.固相制备过程的活化能E=81.08 kJ·mol-1,过程动力学为二维相界面扩散反应机理.前驱体生成LiNiPO4的反应符合界面反应指数成核机理,活化能E1=11.82 kJ·mol-1,指前因子lnA=13.82;LiNiPO4晶体生长过程具有较小的活化能E2=17.73 kJ·mol-1;Li3PO4转化反应和反应体系物系晶化过程符合二维相界面扩散反应机理,其是制备过程可控制的重要步骤.材料复合电极LiNiPO4+Nafion/C在0.5 mol·L-1H2SO4中具有典型的电容性能,电极比电容为214 F·g-1,经1 000次循环,电极电容量不但没有衰减反而略有增加,是潜在的电容器材料.     

Fabrication of the 19-filament Fe/Cu clad MgB2 wire via in situ powder-in-tube method

Using commercial amorphous B powder (92% in purity) and Mg powder (99% in purity) as starting materials, 19-filament Fe/Cu clad MgB2 wires were fabricated by an in situ powder-in-tube method. Heat treatment was performed at 700℃ for 1 h under an argon gas atmosphere. The influence of Mg/B ratio on the microstructure and superconducting properties of the wires was investigated. It was found that the major phases of MgB2 wires were MgB2 accompanied with relatively small amounts of MgO and Fe2B impurities. With 5% excess Mg addition, the onset TC slightly decreased. However, the transport JC at 4.2 K and 4 T reached 1.07×104 A·cm-2, increasing by a factor of 1.4 compared to the stoichiometric sample. Moreover, the Mg1.05B2 sample showed an improved field dependence of JC, suggesting that less voids and smaller grain size of the Mg1.05B2 core lead to better grain connectivity and stronger flux pinning.     

Investigation of the microcrack evolution in a Ti-based bulk metallic glass matrix composite

The initiation and evolution behavior of the shear-bands and microcracks in a Ti-based metallic-glass–matrix composite(MGMC) were investigated by using an in-situ tensile test under transmission electron microscopy(TEM). It was found that the plastic deformation of the Ti-based MGMC related with the generation of the plastic deformation zone in crystalline and shear deformation zone in glass phase near the crack tip. The dendrites can suppress the propagation of the shear band effectively. Before the rapid propagation of cracks, the extending of plastic deformation zone and shear deformation zone ahead of crack tip is the main pattern in the composite.     

石墨相氮化碳表面包覆改善锂离子电池正极材料LiCoO2电化学性能的研究

通过简单的固相法和液相法,分别制备出石墨相氮化碳（g-C₃N₄）表面改性的商品化LiCoO₂复合材料,采用扫描电子显微镜观察改性后的材料,发现g-C₃N₄都均匀地包裹在LiCoO₂表面。两种g-C₃N₄-LiCoO₂复合材料被用作锂离子电池的正极材料,电化学测试结果显示,固相法制得的g-C₃N₄-LiCoO₂复合材料在0.2 C的倍率下充放电测试,首次比容量达167 mA·h·g^-1,循环80次后,比容量仍达132 mA·h·g^-1,高于未经g-C₃N₄包裹的纯LiCoO₂（98 mA·h·g^-1）;液相法制得的Y-C₃N₄-LiCoO₂复合材料循环稳定性明显优于同类材料,循环80次后容量保持率均在95%以上。试验证实,g-C₃N₄表面改性的策略具有一定的实用价值,改性后,材料优异的电化学性能归因于g-C₃N₄的包裹处理,这不仅增强了固体电解质界面（SEI）的稳定性,也抑制了锂离子嵌入/脱出电极材料时引起LiCoO₂体积的变化。     

Formation and mechanical properties of Zr-based bulk metallic glass composites with high oxygen levels

Zr-based bulk metallic glass(BMG) composites with in situ formed Y 2 O 3 particle reinforcements were synthesized by proper additions of Y to ultrahigh-oxygen-containing glass-forming alloy precursors.Microstructures,thermal stabilities,and mechanical properties of the composites were investigated.Glass formation was greatly enhanced by Y additions in the alloys and the resultant particles were homogenously distributed in the glassy matrix,allowing for the fabrication of oxide dispersion strengthened BMG composites.The compressive strength and hardness increased by 10% and 20%,respectively,with the introduction of Y 2 O 3 particles.These results are significant for the design and production of Zr-based BMGs and BMG composites with improved properties using commercial high-oxygen content raw materials under industrial conditions.     

碳化对含花岗岩石粉硫氧镁水泥的抗压强度和耐水性的影响

以CO₂气氛作为养护条件,研究了不同掺量的花岗岩石粉（GP）对硫氧镁（MOS）水泥性能的影响,结合X射线衍射仪（XRD）、同步综合热分析仪（TG-DSC）、扫描电镜（SEM）和压汞仪（MIP）对MOS水泥水化产物及微观结构做了分析。结果表明,碳化28 d后的掺加40% GP的MOS水泥强度保留系数提高至1.12;碳化28 d后浸水120 d强度保留系数为0.94,较空白样提高了123.8%;MOS水泥碳化过程中基体内Mg(OH)₂转化为MgCO₃·zH₂O晶体,有利于改善MOS水泥的力学性能;GP改善了MOS水泥孔结构,提高了密实度,降低了CO₂吸收率,减弱了CO₂的侵蚀作用;GP和碳酸镁相的共同作用提升了MOS水泥碳化后的力学性能和耐水性。     

Stable structure of Zr49Cu44Al7 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 B ₀ =115.2 GPa has been obtained.     

Synthesis of amorphous SeP2/C composite by plasma assisted ball milling for high-performance anode materials of lithium and sodium-ion batteries

To promote substantially the performances of red phosphorous (P) anode for lithium and sodium-ion batteries, a simple plasma assisted milling (P-milling) method was used to in-situ synthesize SeP₂/C composite. The results showed that the amorphous SeP₂/C composite exhibits the excellent lithium and sodium storage performances duo to the small nano-granules size and complete combination of selenium (Se) and phosphorous (P) to generate Se–P alloy phase. It was observed that inside the granules of SeP₂/C composite the nanometer size of the SeP₂ particles ensured the fast kinetics for Li⁺ and Na⁺ ​transfer, and the amorphous carbon wrapping the SeP₂ particles relieved volume expansion during lithium/sodium storage processes and enhances electric conductivity. Therefore, the SeP₂/C electrode retained reversible capacities of 700 ​mA ​h ​g⁻¹ at 2 ​A ​g⁻¹ after 500 cycles and 400 ​mA ​h ​g⁻¹ at 0.5 ​A ​g⁻¹ after 400 cycles as anode for LIBs and SIBs, respectively. The result proves that the amorphous SeP₂/C composite can be a new type of anode material with great potential for lithium and sodium-ion batteries.     

超声波搅拌时间对原位自生Mg2Si/Al基复合材料凝固组织和力学性能的影响

为了研究铝基复合材料的凝固组织和力学性能,采用超声波搅拌的方法制备了原位自生Mg₂Si/Al基复合材料.利用X射线衍射仪(XRD)、金相显微镜(OM)和扫描电子显微镜(SEM)分析其微观形貌,并通过硬度检测和拉伸试验测试其力学性能.结果表明:超声波搅拌不但能够细化初生Mg₂Si颗粒,改变凝固组织形貌,而且具有除气除杂功能,二者共同提高了Mg₂Si/Al基复合材料的力学性能;经过超声波搅拌的Mg₂Si/Al基复合材料与未经过超声波搅拌的Mg₂Si/Al基复合材料相比,抗拉强度与伸长率总体呈上升趋势,其断口形貌均为准解理面.在超声时间为40 s时,抗拉强度和伸长率达到最大值,分别为201 MPa和5.63%,相比未超声处理的Mg₂Si/Al基复合材料的抗拉强度和伸长率,分别增长了139.29%和178.71%;复合材料的硬度先升高后降低,超声作用时间为30 s时硬度最佳,为116.96(HB).     

Sulfurized hematite for photo-Fenton catalysis

A hematite/amorphous sulfur composite was prepared via simple heating hematite and α-sulfur in Teflon-lined autoclave at low temperature. The composite was characterized by X-ray diffraction(XRD), Raman spectrum,Thermal Gravity Analysis(TGA), Transmission Electron Microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). The results revealed that an allotrope sulfur at 5-37% weight percent was found in the composite.After sulfuration, S_n~(2-) or S_2~(2-) was doped in the lattice of hematite, large amounts of OH and SO_4 were adsorbed on the surface of hematite. Hematite/amorphous sulfur composite had superior photo-Fenton activities than pure hematite. This work also demonstrated that amorphous sulfur also had the activity of photo-Fenton catalysis. OH~-and SO_4 radicals facilitated dye adsorption and acted as a bridge to link H_2 O_2. Moreover, SO_4 radicals on hematite served as electron trapping center that can receive photo-induced electron from conduction band of hematite and transfer it to the adsorbed H_2 O_2, increasing the rate of photo-Fenton reaction eventually.     

Work toughening effect in Zr_（41）Ti_（14）Cu_（12.5）Ni_（10）Be_（22.5） bulk metallic glass

Work hardening is a well-known phenomenon occurring in crystalline metals during deformation,which has been widely used to increase the strength of metals although their ductility is usually reduced simultaneously. Here we report that the plastic strain of Zr41Ti14Cu12.5Ni10Be22.5 (at.%) bulk metallic glasses has been increased from 0.3% for the as-cast sample to 2.5%-8.0% for samples that have experienced pre-deformation under constrained conditions. The pre-deformed glassy alloys possess more free volume and abundant introduced shear bands,which are believed to promote the activation of shear bands in post-deformation and result in an increase in plasticity. The orientation of the pre-introduced shear bands relative to the loading direction will affect the deformation behavior of pre-deformed samples. The present results show that pre-deformation of this glassy alloy will result in work toughening. This work toughening effect can be removed by isothermal annealing at a sub-Tg (glass transition) temperature,which causes annihilation of free volume and healing of shear bands.     

Al/Pb-WC-ZrO2复合电极材料的电化学性能研究

 研究了电镀液中固体微粒质量浓度及工艺条件对Al/Pb-WC-ZrO₂复合电极材料的表面化学组成及稳态析氧极化曲线的影响规律,对上述工艺条件进行了优化,优化后的工艺条件如下:WC:50 g/L,ZrO₂:40g/L,温度:20℃,电流密度:1.5 A/dm²,电沉积时间:2 h.所获得Al/Pb-WC-ZrO₂复合电极材料的析氧动力学参数为:a=771 mV,b=140 mV,i⁰=3.11×10^-6A·cm^-2,并且电极的析氧过电位为η=1 009 mV,复合镀层中WC和ZrO₂质量分数分别为10.02%和3.55%.     

Mechanical, deformation and fracture behaviors of bulk metallic glass composites reinforced by spherical B2 particles

Ti_(45)Cu_(40)Ni_7Zr_5Sn_(2.5)Si_(0.5) alloys were prepared under various cooling rate conditions during solidification.The alloys exhibited different volume fractions of B2 particles with 0～40 vol%in an amorphous matrix.Monolithic bulk metallic glass of 1 mm diameter showed no macroscopic plasticity and exhibited the typical vein patterns in a maximum shear stress plane on the fracture surface.However,a bulk metallic glass composite containing the B2 particles revealed obvious plasticity(～5.6%)with a remarkable work-hardening behavior that resulted from a stress-induced martensitic transformation of the B2 particles.Moreover,the composite displayed the complicated fracture morphologies containing of three types of fracture features.Through detailed investigations on the microstructural evolution,mechanical,deformation and fracture characteristics,the influence of B2 particle on overall behavior of the TiCu-based bulk metallic glass composites was elucidated.     

Relationship between composite structures and compressive properties in CuZr-based bulk metallic glass system

Bulk metallic glass (BMG) composites with the austenite B2 phase as reinforcement macroscopically showed strain hardening behavior due to the plasticity induced by martensitic transformation during deformation. Relationship between characteristics of the B2-CuZr reinforcing phase and uniaxial compressive properties of CuZr-based BMG composites was studied. Mechanical properties of these BMG composites were found to depend on not only the reinforced phases but also the amorphous matrix,and the yield and fracture strength can be roughly estimated by the rule of mixture principle. Distribution of the reinforced B2-CuZr phase has an important impact on the compressive plasticity even for the composites with a similar volume fraction of the crystalline phase.