离子色谱-积分脉冲安培检测法同时测定酱油中20种氨基酸和6种糖

建立了梯度淋洗-离子色谱-积分脉冲安培检测法同时测定酱油中20种氨基酸和6种糖的方法,通过对色谱柱温度、pH值、放置时间等实验影响因素的考察,探索出了适合26种组分测定的多级梯度淋洗条件。结果表明,当流速为0.25 mL/min , pH值在5.2~6.7,柱温在35 ℃时,26种组分在各自的浓度范围内具有良好的线性关系( r 2≥0.995)。除了谷氨酰胺、亮氨酸、异亮氨酸、蛋氨酸外,其他22种组分的检出限均小于0.03 mg/L;在0.20、0.50、2.00 mg/L 3个添加水平下,回收率为84.2%~109%, RSD为2.7%~7.8%。该方法高效、简便、灵敏、准确,可用于酱油中多种氨基酸和糖的同时测定以及掺假辨别技术研究。

液相串联质谱仪检测水产品中相关抗生素残留的研究

通过液相串联质谱仪分析水产品的相关抗生素,借助相关水产品样品对样品定性、定量分析,本文将借助HLB固相萃柱在水产品富集、净化后,研究抗生素残留,液相串联质谱仪对水产品的抗生素残留分析中有着很广泛的应用。

Minor alloying behavior in bulk metallic glasses and high-entropy alloys

The effect of minor alloying on several bulk metallic glasses and high-entropy al-loys was studied. It was found that minor Nb addition can optimize the interface structure between the W fiber and the Zr-based bulk metallic glass in the compos-ites,and improve the mechanical properties. Minor Y addition can destabilize the crystalline phases by inducing lattice distortion as a result to improve the glass-forming ability,and the lattice distortion energy is closely related to the effi-ciency of space filling of the competing crystalline phases. A long-period ordered structure can precipitate in the Mg-based bulk metallic glass by yttrium alloying. For the high-entropy alloys,solid solution can be formed by alloying,and its me-chanical properties can be comparable to most of the bulk metallic glasses.

服役后的René N5镍基单晶高温合金燃机涡轮叶片定量表征与评估

对服役近26000 h的RenéN5单晶高温合金燃机高压一级涡轮叶片进行解剖分析,研究了叶片不同部位的组织演化和损伤程度。分析了γ′相的形貌和体积分数,拓扑反转程度,碳化物的形貌和成分。结果表明,γ′相的体积分数和拓扑反转程度可以作为服役叶片显微组织损伤的定量表征参数,γ′相的形貌和拓扑密排相(TCP)的析出可以作为半定量的表征参数。根据以上参数,服役后的燃机涡轮叶片的组织损伤程度可以分为3个等级:轻度损伤,中度损伤和重度损伤。本研究结果为燃机用单晶涡轮叶片的组织损伤评价奠定了基础,并对叶片服役安全具有重要意义。

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.

Atomic structures of Zr-based metallic glasses

The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission electron microscopy (HRTEM) techniques. We focused on the short-range order (SRO) and medium-range order (MRO) in the glassy structure. It is shown that there are icosahedral,FCC-and BCC-type SROs in the Zr-based metallic glasses. A structural model,characterized by imperfect ordered packing (IOP),was proposed based on the MD simulation and confirmed by the HRTEM observation. Furthermore,the evolution from IOP to nanocrystal during the crystallization of metallic glasses was also ex-plored. It is found that the growth from IOP to nanocrystal proceeds through three distinct stages: the formation of quasi-ordered structure with one-dimensional (1D) periodicity,then 2D periodicity,and finally the formation of 3D nanocrystals. It is also noted that these three growth steps are crosslinked.

A new many-body potential with the second-moment approximation of tight-binding scheme for Hafnium

In this work,we develop a new many-body potential for alpha-hafnium(α-Hf)based on the second moment approximation of tight-binding(TB-SMA)theory by introducing an additional Heaviside step function into the potential model and a new analytical scheme of density function.All the parameters of the new potential have been systematically evaluated by fitting to ground-state properties including cohesive energy,lattice constants,elastic constants,vacancy formation energy,structure stability and equation of state.By using the present model,the melting point,melt heat,thermal expansion coefficient,point defects,and low-index surface energies ofα-Hf were calculated through molecular dynamics simulations.Comparing with experiment observations from others,it is shown that these properties can be reproduced reasonably by the present model,some results being more consistent to the experimental data than those by previous suggested models.This indicates that this work is sutiable in TB-SMA potential for hexagonal close packed metals.

Structural rejuvenation and toughening of bulk metallic glass via ultrasound excitation technique

Bulk metallic glasses(BMGs)represent a class of solid materials which have randomly packed atomic structure in long range but exhibit unique properties.Nowadays,the macroscopic brittleness at ambient temperature is the fundamental and intriguing issue to impede the engineering application of BMGs.In this article,we report a breakthrough in solving the strength-ductility tradeoff dilemma of BMGs by introducing strong forced vibration of atoms named ultrasonic vibration(USV)technique.We find that not only the ambient temperature compressive plasticity is remarkably increased but also yield strength is augmented by kHZ level USV treatment.The toughening of BMGs has also been evidenced by the pronounced increase in the first pop-in event,which represents by the critical stress to stimulate the initial yield with the formation of shear band.It has also been confirmed that the free volume in USV treated BMGs is strikingly increased.Therefore,the intrinsic mechanism of USV induced toughening can be interpreted in the frame of structural heterogeneities and energy landscape theory,i.e.,the USV induced structural rejuvenation by increasing the loosely packed soft regions and decreasing the closely packed hard regions.The basins that possess larger potential energies are overwhelmingly increased after USV treatment.Our findings provide a new approach for surmounting strength-ductility trade-off dilemma of single atom glassy matter such as BMGs.