Determination of Ten Kinds of Alpha-2 Agonists Residues in Animal Derived Food by UHPLC-Triple Quadrupole/Composite Linear Ion Trap Mass Spectrometry

[Objectives]The paper was to establish an ultra high performance liquid chromatography-quadrupole/linear ion trap complex mass spectrometry for the determination of 10 kinds ofα2-receptor agonists in animal derived food.[Methods]The samples were extracted with sodium carbonate buffer solution and ethyl acetate,and analyzed by mass spectrometry after solid phase extraction and high performance liquid chromatography separation.[Results]Ten kinds ofα2-receptor agonists showed a good linear relationship in the range of 1-100μg/mL,with the average recovery of over 69%and the relative standard deviation less than 8.32%.The detection limit of 10 kinds of α_(2)-receptor agonists was up to 1μg/kg.[Conclusions]The method has good selectivity and strong anti-interference ability,and can meet the requirements of 10 kinds ofα2-receptor agonists residues in animal derived food.

THE INTERFACIAL BEHAVIORS OF ALUMINUM MATRIX COMPOSITE IN DIFFERENT WELDING METHODS

Non-interlayer liquid phase diffusion welding (China Patent) and laser welding methods for aluminum matrix composite are mainly described in this paper. In the non-interlayer liquid phase diffusion welding, the key processing parameters affecting the strength of joint is welding temperature. When temperature rises beyond solidus temperature, the bonded line vanishes. The strength of joint reaches the maximum and becomes constant when welding temperature is close to liquid phase temperature. Oxide film in the interface is no longer detected by SEM in the welded joint. With this kind of technique, particle reinforced aluminum matrix composite Al2 O3p/6061Al is welded successfully, and the joint strength is about 80% of the strength of composite (as-casted). In the laser welding, results indicate that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement is restrained intensively at certain laser power and pulsed laser beam. The laser pulse frequency directly affects the reinforcement segregation and the reinforcement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. The maximum strength of the weld can reach 70% of the strength of the parent.

Study on behavior of reinforcement in molten pool for submicron composite Al_2O_3p/6061 Al during laser welding

The behavior of the reinforcement of submicron composite Al_ 2 O_ 3 p/6061Al in molten pool during laser welding was studied. It was indicated that because there were the remarkable differences in thermal physical properties between matrix and reinforcement particulate, the reinforced particulate was pushed forward during molten pool solidification by the liquid-solid interface in matrix and the reinforced particulate segregated in the weld. It resulted in noticeable degradation in properties of the welded joint. The technology methods to improve the behavior of reinforcement were also investigated. It was pointed out that the laser pulse frequency is the main welding parameter affecting the distributive state of reinforcement, and the theory basis was established for welding the material by laser beam.

Role of friction stir welding parameters on tensile strength of AA6061-B_4C composite joints

Friction stir welding（FSW） is a solid state joining technique developed to join high strength aluminum alloys and various ceramic reinforced metal matrix composites（MMCs）.FSW produces sound welds in MMCs without any deleterious reaction between reinforcement and matrix.The present work focused on the effect of FSW parameters on the tensile strength of Al-B4C composite joints.The central composite design of four factors and five levels was used to control the number of experiments.A mathematical model was developed to analyze the influence of FSW parameters.The results indicated that the joint fabricated using rotational speed of 1000 r/min,welding speed of 1.3 mm/s,axial force of 10 kN and the reinforcement of 12% showed larger tensile strength compared with the other joints.The developed model was optimized to maximize the tensile strength using generalized reduced gradient method.The metallographic analysis of the joints showed the presence of various zones such as weld nugget（WN） zone,thermo mechanically affected zone（TMAZ） and heat affected zone（HAZ）.The substantial grain refinement of aluminum matrix as well as significant size reduction of B4C particles was observed in the weld nugget.TMAZ was plastically deformed,thermally affected and exhibited elongated aluminum grains.

STUDY ON DIFFUSION WELDING OF ALUMINIUN MATRIX COMPOSITE

Effects of diffusion welding parameters on strength of welded joint based on particle reinforced alumini- um matrix composite Al2O3p/6061Al were studied by comparing with aluminium matrix alloy,Mecha- nism for the loss of joint strength was analyzed.It was pointed out that the key processing parameters affecting the strength of joint was the welding temperature.The high quality joint can be successfully obtained with appropriate diffusion welding parameters.

PULSED Nd-YAG LASER WELDING OF AN AI-SiC_p METAL MATRIX COMPOSITE

A study is presented of the laser welding behaviour of an SiC particulate re-inforced Al-alloy comPOsite using a pulsed Nd-YAG laser. The influences of laser weldingparameters of laser intensity, pulse duration and the beamjs focus position on the depth ofweld penetration as well as the size of weld bead width were investigated. A typical mi-crostructure of a weld section reveals that the three distinct zones are present. Cracks andporosity were fOund to be two major defects in laser welded metal matrix composites(MMC). These investigations have led to an optimum welding condition proposed forlaser welding of SiC partiulate reinforced aluminium alloy comPosites with minimum de-fects.

Mechanism of laser welding of SiC reinforced LD2 aluminum metal matrix composite

In this paper the mechanism of SiC_P/LD2 aluminum matrix composites during laser welding was investigated. The emphasis was laid on the study of the distribution of aluminum carbides in whole welds. The joint can be divided into three regions both in depth and in width. The depth is divided into severe reaction region, partial reaction region, and no reaction region. In these regions, the extent of interfacial reaction varies gradually, the shape of reactants varies from long to fine. In width it can also be divided into severe reaction region, partial reaction region, and initial reaction region from the center of the weld to about the welding junction. In the initial reaction region, nucleation and growth of the reaction products on the surface of SiC particles can be observed by using TEM. The investigation showed that the quantity and size of SiC are relative to the temperature gradient in the molten pool.

Resistance welding of carbon fibre reinforced polyetheretherketone composites using metal mesh and PEI film

Weldability of polyetheretherketone(PEEK) with polyetherimide(PEI) is tested. And carbon fiber reinforced PEEK laminates are resistance welded using stainless steel mesh heating element. The effects of the welding time and welding pressure on the lap shear strength of joints are investigated. Results show that PEEK can heal with PEI well in welding condition and the lap shear strength of PEEK/CF(carbon fibre) joint increases linearly with welding time, but reaches a maximum value when welding pressure ranging from 0.3 MPa to 0.5 MPa with constant welding time. The fracture characteristics of surface are analyzed by SEM techniques, and four types of fracture modes of lap shear joints are suggested.

Multi-objective optimization of friction stir welding parameters using desirability approach to join Al/SiC_p metal matrix composites

Silicon carbide particulate （SiCp） reinforced cast aluminium （A1） based metal matrix composites （MMCs） have gained wide acceptance in the fabrication of light weight structures requiring high specific strength, high temperature capability and good wear resistance. Friction stir welding （FSW） process parameters play major role in deciding the performance of welded joints. The ultimate tensile strength, notch tensile strength and weld nugget hardness of friction stir butt welded joints of cast A1/SiCp MMCs （AA6061 with 20% （volume fraction） of SiCp） were investigated. The relationships between the FSW process parameters （rotational speed, welding speed and axial force） and the responses （ultimate tensile strength, notch tensile strength and weld nugget hardness） were established. The optimal welding parameters to maximize the mechanical properties were identified by using desirability approach. From this investigation, it is found that the joints fabricated with the tool rotational speed of 1370 r/min, welding speed of 88.9 mm/min, and axial force of 9.6 kN yield the maximum ultimate tensile strength, notch tensile strength and hardness of 265 MPa, 201 MPa and HV 114, respectively.

Effect of Welding Paramenter on Joint Property of Aluminum Matrix Composite in Liquid-Phase-Impacting Diffusion Welding

In this paper, a new method for welding SiCp/101A was put forward. It is LPI (liquid-phase-impacting) diffusionwelding. Through LPI diffusion welding SiCp/101A aluminum, the effect of welding parameters on the weldedjoint property was investigated, and the optimal welding parameters were brought forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to studythe relationship between the macro-properties of joint and the microstructure. The results show that LPI diffusionwelding could be used for welding aluminum matrix composites SiCp/101A successfully.

Effect of tool rotational speed on the particle distribution in friction stir welding of AA6092/17.5 SiCp-T6 composite plates and its consequences on the mechanical property of the joint

This study investigates the effect of tool rotational speed(TRS)on particle distribution in nugget zone(NZ)through quantitative approach and its consequences on the mechanical property of friction stir welded joints of AA6092/17.5 SiCp-T6 composite.6 mm thick plates are welded at a constant tool tilt angle of 2°and tool traverse speed of 1 mm/s by varying the TRS at 1000 rpm,1500 rpm and 2000 rpm with a taper pin profiled tool.Microstructure analysis shows large quantity of uniformly shaped smaller size SiC particle with lower average particle area which are homogeneously distributed in the NZ.The fragmentation of bigger size particles has been observed because of abrading action of the hard tool and resulting shearing effect and severe stress generation due to the rotation of tool.The particles occupy maximum area in the matrix compared to that of the base material(BM)due to the redistribution of broken particles as an effect of TRS.The migration of particles towards the TMAZ-NZ transition zone has been also encountered at higher TRS(2000 rpm).The microhardness analysis depicts variation in average hardness from top to bottom of the NZ,minimum for 1500 rpm and maximum for 2000 rpm.The impact strength at 1000 rpm and 1500 rpm remains close to that of BM(21.6 J)while 2000 rpm shows the accountable reduction.The maximum joint efficiency has been achieved at 1500 rpm(84%)and minimum at 1000 rpm(68%)under tensile loading.Fractographic analysis shows mixed mode of failure for BM,1000 rpm and 1500 rpm,whereas 2000 rpm shows the brittle mode of failure.

Fabrication of SiC_p/AA5083 composite via friction stir welding

Microstructure and mechanical properties of SiCp /AA5083 composite fabricated by friction stir welding (FSW) were investigated.The influence of the number of FSW passes on the distribution of SiC particles and mechanical properties in the joint was studied.After one pass,the SiC particles were entangled in the upper side of the stir zone (SZ).However,the particle distribution became more uniform after two passes due to the repeated stirring of the joint.As the SiC particles facilitate the grain refinement in the SZ by the pinning effect,the particle including region has much smaller grain size than the SZ without SiC particles.The SiCp /AA5083 composite region exhibits a Vickers hardness of HV90,which is much higher than the value of HV80 in the SZ produced by FSW without SiC particles.

Diffusion welding process and joint's microstructure behavior of SiC_w/6061Al composite

The rules such as process parameters affecting joint properties and theevolution principle of weld's microstructure have been researched by adopting diffusion weldingprocess to connect SiC_w/6061Al composite. Experimental results show that there exists a criticaltemperature region between solid and liquid phase line of SiC_w/6061Al composite, and the regionwill shrink with the increasing of welding pressure. When diffusion welding occurred under thecritical temperature region, welding joint exhibits bad property of bonding, and the matrix and thereinforcement can't bond effectively. When diffusion welding occurred in the critical temperatureregion, the strength of welding joint changes widely with the variation of welding temperature. Whenwelding temperature varies in 10 deg C, the strength of welding joint will change obviously. Onlywhen welding temperature is higher than the critical temperature region, stable joint properties canbe obtained. Simultaneously the matrix and the reinforcement has better interfacial bonded indiffusion welding interface, and no obvious interface reaction occurred, and thus diffusion weldingof SiC_w/6061 Al composite can be successfully realized.

Diffusion welding of SiCp/2014Al composites using Ni as interlayer

SiCp/2014Al composites were bonded with the vacuum diffusion welding technique using Ni as the interlayer metal. Ni and Al were interdiffused and there were intermetallic compounds formed in the inter transition layer, which was composed of Ni3Al//NiAl//NiAl3. The relation between the diffusion distance and the element concentration was calculated according to Fick＇s second law. The relations of the diffusion concentration and the diffusion welding technique parameters were calculated.

Interface reaction in aluminium matrix composite at laser welding

Interface reaction of SiC w/6061Al aluminium matrix composite subjected to laser welding was studied. It is pointed out that the main reason for bad weldability of the material is concerned with the interface reaction during the welding. Effects of welding parameters on interface reaction were also investigated. The results show that the interface bonding state can be improved by laser beam, and the main welding parameter affecting the strength of weld is laser output power. The smaller the output power, the lower the extent of interface reaction and the better the mechanical properties.

EFFECTS OF DIFFUSION WELDING PARAMETERS ON JOINT STRENGTH OF SiCw/6061AI COMPOSITE

Diffusion welding was used to join SiCw/6061AI composites. The effects of welding pammeters on strength Of welded joint were investigated. JOint Of high quality for SiCw/6061Al composites can be obtained with aPPropriate diffesion welding parameters.

Liquid-Phase-Impacting Diffusion Welding Mechanism and Microstructure of Welded Joint of Al Matrix Composite SiCp/101A

The liquid-phase-impacting (LPI) diffusion welding mechanism and microstructure of welded joint of aluminum matrixcomposite SiCp/101A have been studied. It shows that by LPl diffusion welding, the interface state between SiCparticle and matrix is prominent, the harmful microstructure or brittle phase can be restrained from the welded joint.Moreover, the density of dislocation in the matrix near the interface and in the matrix are all so higher than that ofparent composite, the dislocation entwists each other intensively resulted in welding the composite successfully.

Structural considerations in friction welding of hybrid Al_2O_3-reinforced aluminum composites

Comparative studies on the relationship between the welding parameters and joining efficiency in the friction welding of hybrid Al203-reinforced aluminum composites were conducted. Metal matrix composites （MMCs） with 37% （volume fraction） aluminum particle were joined by friction welding. The results show that the effects of the rotation speed on the reduction rate of particle size are greater than those of the upset pressure, and the area of the MMC weld zone decreases as the joining efficiency increases, while it is considered that the joining efficiency does not increase as the reduction rate of particle size decreases. During the macro-examination of the bonding interlace, a gray discolored region was observed on the bonding interface, and the center of the region was dark gray. After the micro-examination of the bonding interface, base metal made some second particulate formed by condensed alumina particulate but discoloration part distributed minute alumina particulate without second particulate. Consequently, it was also observed that rotational speed of 3 000 r/min and upset pressure of 63.6 MPa showed a very good.joint.

Microstructures of electron beam welding joint of CNTs/Al composites

Carbon nauotube（ CNT） reinforced aluminum metal matrix composites were welded by electron beam welding and the microstructures of welded joints were investigated. The result showed that the interracial reaction happened between the CNTs and Al matrix, which resulted in producing brittle Al4 C3 compounds in electron beam welds. The extent of interfacial reaction varies gradually in the depth and width direction. The length of the reactants Al4C3 became short duo to the temperature gradient in the molten pool. The quantity and size of Al4 C3 compounds increased with the increase of beam current and the decrease of welding speed in the middle zone of weld. However, no needle-like phase Al4C3 was observed in HAZ.

Effect of silicon content on microstructure of Al-Si/SiC_p composite layer cladded on A380 Al alloy by TIG welding process

Tungsten inert gas（TIG） welding was applied to creating a composite layer on the surface of cast aluminum alloy A380. Different mixtures of Al, Si and SiC powders mixed with sodium silicate solution were pasted on substrates. Surface melting was conducted by TIG welding to produce Al-SiC layer on the surface. Microstructural evolution was investigated by X-ray diffractometry（XRD）, optical and scanning electron microscopy（SEM） and elemental microanalysis（EDS）. Properties of clad layers were studied by microhardness and sliding wear testing. The results showed a uniform distribution of SiC particles in dendritic aluminum matrix. Addition of excess silicon caused the formation of eutectic crystals and coarse silicon particles in the clad layer which resulted in higher hardness and wear resistance of clad layers.