Rheological Properties and MR Polishing Characteristics of Core Shell-Structured Silica-Coated CI Particles

Recently,ultra-precision polishing processes using smart materials such as magnetorheological(MR)fluids have been used for optics parts such as aspheric lenses.The MR fluid applied in MR polishing is a phase controllable suspension comprising a mixture of CI particles and non-magnetic fluids such as mineral oil and water.The fluids are a kind of smart material that can be controlled according to their flow properties such as viscosity and stiffness.Water-based MR fluids are easily oxidized if the fluids are exposed and this oxidation can bring irregular polishing results.Also,this phenomenon is one of several factors that reduce the life time of MR fluids.In a previous work,CI particles were coated with a polymer or a composite for the improvement of dispersion stability and prevention of corrosion due to oxidation.From this study,the rheological properties such as viscosity and sedimentation of coated CI particles with silica were investigated with a rotational rheometer;MR polishing characteristics of BK7 glass were studied in order to investigate the surface roughness.The wheel speed and magnetic field intensity were chosen as variables.     

Time-resolved in-situ analysis of phase evolution for the directional solidification of carbon steel weld metal

Kinetic information about the phase transformation, during solidification process and solid-state transformation is essential to the material processing, such as welding. In our research group, in-situ phase identification system consisting of undulator beam and imaging plate have recently been used. The welding torch is driven by stepping-motor in the system. Those make possible that phase transformation can be identified in real-time under the condition of directional solidification and the spatial resolution of 100 × 500 μm. The time-resolution is 0.3125 seconds. In the present work, combination of analyzing method: the in-situ phase identification system, morphological observation by high-temperature laser scanning confocal microscopy and observation of microstructure at room temperature by OM, SEM and micro diffraction-system, is suggested to analyze the phase transformation during welding process. Phase transformation process of hypereutectoid carbon steel, during welding was analyzed as an example of combination observation.     

Combination Effect of Si and P on Tertiary Scale Characteristic of Hot Rolled Strip

For high strength interstitial free(IF)steel containing P element,the salt and pepper(SP)defects exist on the strip surface and could not be eliminated effectively by optimizing the hot rolling process,such as temperature and cooling water.The combination effect of Si and P on the characteristic of tertiary scale has been studied comprehensively by scanning electron microscopy(SEM)and electron probe microanalysis(EPMA),and the concept is proposed firstly that Si and P are of combination effect which can be utilized to eliminate the SP defect.The results show that the SP defects were induced by the rolled-in scale during finish rolling.P can be enriched at the interface between substrate and tertiary scale,which is easy to decrease the adhesion of tertiary scale.However,Si enrichment at the interface between substrate and tertiary scale can increase the adhesion.The SP defects can be eliminated completely,which is attributed to the accompanying enrichment of Si and P.     

Separation of Scandium and Rare Earths with the Method of PSO-Extraction Chromatography

Separation of scandium and rare earths was investigated by using a new extraction chromatography whichPSO was used as a stationary phase,while HCl-NH_4SCN solution as a mobile phase.The separation conditionswere studied.In this system, the separation factor(β_(Nd)~(Sc))can reach up to 1.3×10~4.The method can be applied tothe purposes of separation,purification and analysis of microquantity of Sc in the mixed rare earth.     

Observation of Insulin Exocytosis by a Pancreatic (3 Cell Line with Total Internal Reflection Fluorescence Microscopy

INSULIN secretion was traditionally measured with biochemical and immunological methods such as enzyme linked immunosorbant assay and radio-immunoassay.However,these methods can only tell the amount of insulin secreted; they give no information about the secretion process or mechanism of exocytosis.In recent years,an imaging technique known as total internal reflection fluorescence (TIRF) microscopy has been employed to study insulin secretion.1-4 This imaging technique can explore events taking place near or on live cell membrane,such as secretory granule movement,exocytosis,vesicle content release,and membrane fusion.5-10 In the present paper,we applied TIRF microscopy to the observation of insulin exocytosis by the pancreatic β cell line Ins-1.     

Studies on addition of inclusions to molten aluminum using a novel technique

Considerable initiatives have often been taken to introduce specific solid particles directly into molten metals in a desirable quantity, but little success has been achieved, particularly in the case of reactive particles. Therefore, alternative routes such as production of solid particles through chemical reactions within the melt are often used. While these methods are capable of producing solid particles within the melt, the chemistry of the melt changes and control of particle size and chemistry is difficult. In the present study, a direct addition technique has been used to introduce many types of inclusions into liquid aluminum and Al-Si alloys, irrespective of their wettability and chemical reactivity, while preserving the surface characteristics and melt chemistry. A uniform particle distribution can be obtained even at low volume fraction of addition and with particle sizes of the order of 2 to 5 μm. This technique allows valuable information regarding the behavior of many inclusions, such as TiB₂, TiC, SrO, and Sr(OH)₂, in liquid aluminum to be studied. Several such examples are presented.     

Co-Al基三元系中B2相的溶解度间隙与稳定性

Information on phase equilibria in the Co-Al based systems which are related to some magnetic and heat resistance materials is important for their microstructural control. Recently, it was proposed with a theoretical calculation on electronic band structure that some Heusler-type alloys Co2 XAl (X: Cr and Mn) should be a new type of spinelectronic materials so-called half-metallic ferromagnet. In the case of the Co2CrAl, however, magnetic properties expected from the theoretical work can not been experimentally obtained and the reason has been still unknown. On the other hand, a tunne- ling magnetoresistance (TMR) effect due to the half-metallic properties was reported in Co2 (Cr0.6 Fe0.4 ) Al alloy, but not the Co2CrAl alloy. In the present paper, it is reported that this discrepancy with the theoretical work in the Co2CrAl alloy is bought about by phase separation between A2 and B2 phases, and that the substitution of Fe for Cr can suppress the precipitation of A2 phase in the B2 phase. Such a phase separation is originally due to the miscibility gap between CoAl and Cr formed in the Co-Al-Cr ternary system as well as that reported by Hao et al. in the Ni-Co-Al-Fe system.     

Flotation behavior and electronic simulations of rare earth minerals in the presence of dolomite supernatant using sodium oleate collector

Common rare earth (RE) minerals, such as bastnasite and monazite, may be formed in deposits associated with carbonate gangue, such as calcite and dolomite. Sodium oleate is a widely used collector for the flotation of both RE and gangue minerals, which might, therefore, be an inefficient process due to the lack of selectivity of this collector. Since these minerals are also sparingly soluble in solution, they could release their constituent ions into the solution, which could affect the floatability of other minerals. In this study, the interactions of sodium oleate with bastn(a|¨)site and monazite in the presence of dissolved dolomite species have been investigated. Micro flotation tests were carried out to explore the effects of these dissolved species on the floatability of the RE minerals. Zeta potential measurements and XPS characterization were carried out to understand how the species affect the collector adsorption. To complement these characterizations, density functional theory (DFT) simulations were conducted to investigate the collector-mineral and collector-adsorbed species (on the mineral surface) interactions.The results show that collector-dolomite interaction energy is greater than that of collector-adsorbed species, but lower than collector-monazite interaction energy, explaining the decrease in the minerals’recovery upon exposure to the dissolved mineral species. It is also shown that oleate ions (OI~-) have the strongest interaction with the minerals compared to other oleate species such as acid soap (HOI_2~-) and oleate dimer (Ol_2~(2-)). The behavior (strength and selectivity) of sodium oleate towards RE minerals and dolomite, as compared to other RE mineral collectors (such as aromatic hydroxamate), is attributed mainly to the collector's and the minerals'structure. The long hydrocarbon chain of sodium oleate which imparts hydrophobic characteristic to the minerals, makes it stronger collector than benzohydroxamate.Moreover, sodium oleate (with linear structure), unlike the aromatic hydroxamate, can approach the mineral easier due to lesser steric hindrance effect and higher reactivity of O involved in the interaction,making it less selective. In addition, it can interact easily with dolomite due to the presence of more exposed active sites than RE minerals.     

Effect of Sulfur Content and Sulfide Shape on Fracture Ductility in Case Hardening Steel

 The effects of sulfur content and calcium addition on smooth axisymmetric tensile fracture ductility of case hardening steel DIN 18CrNiMo7-6 have been investigated. The quantitative metallographic analysis of sulfide inclusions and the correlations between sulfide inclusions and fracture ductility were examined. Sulfide inclusions were found to have deleterious effect on fracture ductility, whereas the effect can be offset to some extent by calcium-treatment due to less easily deforming of sulfides during hot-working. The product (AA·λAW) of sulfide inclusion area fraction (AA) and its area-weighted aspect ratio (λAW) can be used as a parameter to describe the effect of sulfide inclusions on fracture true strain.     

Easy-Magnetization-Axis Arrangements of Sm2Co17 and RE2Fe14B

In order to prepare the bulk samples with high residual magnetization of magnetic compounds, such as (Sm,La)2(Co,Cu,Fe,Zr)17, (Sm,La)1(Co,Cu,Fe)5, Nd2Fe14B, and Pr2Fe14B, directly prepared by solidification, or hot-deformation, it is the first thing to explore the possibilities of the easy magnetization axis of the whole bulk samples to be arranged in one designed direction. α is defined as the angle between the axis and the direction. In Sm-La-Co-Fe-Cu-Zr system, whether α is equal to 0° or 90° depends upon not only alloy compositions but also the ratio of the temperature gradient at the solid/liquid interface and the crystal growth rate. To some alloys, α can be changed from 90° to 0° if the ratio is increased to be higher than a critical value, so the c-axis texture orientation can be obtained. In Nd-Fe-B system, the easy magnetization axis of Nd2Fe14B is always perpendicular to the preferential growth direction [100], and the easy magnetization axes of Nd2Fe14B grains are randomly distributed in the plane normal to the growth direction even if the growth rate is decreased from 250 to 12 μm·s-1. But if the magnetization axis of the anisotropic magnet substrate is perpendicular to the heat flux direction of the laser melting solidification layer, c-axis texture of the columnar Nd2Fe14B grains in the layer can be obtained, which is the same as that of the substrate, if the laser scanning rate is not less than 25 μm·s-1. Also the c-axis texture [006] can be achieved through hot-deformation of PrxFe93.5-xB5Cu1.5 (x=15～19) under the conditions of hot-pressing temperature 973～1273 K, strain rate 10-3 S-1, and strain 50%～80%.     

623K温度下SnxZn1-x/Ni扩散偶的界面反应

为研究Sn-Zn合金(无铅焊料的候选者)和Ni基体(Cu基上的扩散阻挡层)的界面反应,制备一系列原子分数x分别为14.8％、22％和31％的液固扩散偶Sn1-xZnx/Ni;在623 K温度下恒温退火后,用扫描电镜和电子探针检测与分析扩散偶的界面结构,研究退火时间和合金中的Zn含量对扩散层结构和形貌的影响.结果表明,S...     

基于相图和组织控制的先进材料开发

Recent progress on research activities of phase diagrams in our laboratory has been presented. Experimental studies and thermodynamic calculations based on CALPHAD (Calculation of Phase Diagrams) method have been conducted in the following alloy systems. 1. Database on microalloying steels including carbide, nitride and sulfide is now being constructed. 2. ADAMIS (Alloy Database for Micro-Solders) containing 8 elements of Ag, Bi, Cu, In, Sb, Sn, Zn and Pb hasbeen constructed, which can handle all combinations of these elements and all composition ranges. 3. A thermodynamic database of Cu-base alloys including Cu-X binary system and Cu-Fe, Cu-Ni, Cu-Cr base ternarysystems has been constructed. 4. Experimental and thermodynamic calculations on Fe, Ni, Co and Ti aluminides have been conducted. 5. Experimental and thermodynamic calculations on Co base magnetic recording media have been conducted. 6. Thermodynamic analysis of interaction between magnetic and chemical orderings has been performed. By utilizing the information on phase diagrams, the following advanced materials have been developed. (A) New type of high speed steel with high hardness about Hv≈1000 by carbide dispersion carburizing method, (B) New Pb-free machinable stainless steel using titanium carbosulphide. (C) New Pb-free solder for Die-attaching use. (D) Shape memory alloys; Cu-base, Ferromagnetic Ni-base and Fe-base. (E) Invar alloys. (F) Egg-type powder. Typical examples of phase diagrams, phase stability, database and its application for the development of advanced materials will be presented.     

Sn—Ag基无铅焊料的研究与进展

研究开发无铅焊料是我国电子材料行业面临的新课题,Sn-Ag系是一种有希望替代铅焊料的无铅焊料。本文综述了该合金系研究的主要成果,包括微观组织、焊料与基体的相互作用、拉伸和剪切性能、疲劳性能及蠕变性能,指出了此合金系作为软钎焊材料尚待解决的问题。采用合金化、基体涂层、发展新焊剂等手段可使该合金系发展为较理想的无铅焊料。     

（Ag—Cu28）80-Inx—Sn20-x合金焊粉的制备及熔化特性研究

用机械合金化法来制备(Ag-Cu28)80-Inx-Sn20-x合金焊粉。利用差示扫描量热仪(DSC)、X-射线衍射仪(XRD)及扫描电子显微镜(SEM)和Simple-PCI软件对制备合金粒子的熔化特性、物相、微观结构和粒度分布等进行表征分析。研究结果表明:机械合金化法可以有效的制备(Ag-Cu28)80-Inx-Sn20-x合金焊粉。组分为(Ag-Cu28)80-In10.5-Sn9.5合金焊粉的熔化温度最低为490.9℃,其物相组成主要为富Ag相和-βCu81Sn22相。球磨30 h,(Ag-Cu28)80-Inx-Sn20-x体系合金化完全。球磨至80 h,合金粉体的平均尺寸约为47.64μm,铺展率为110.76 cm2/g。     

Interfacial Reactions,Microstructure, and Strength of Sn-8Zn-3Bi and Sn-9Zn-Al Solder on Cu and Au/Ni (P) Pads

The Sn-8Zn-3Bi and Sn-9Zn-Al Pb-free solders were used to mount passive components onto printed circuit boards (PCBs) with electroless Ni immersed Au (ENIG) finishing layers using a reflow soldering process. The component mounted boards were aged at 150 °C for 200 to 1100 hours. The interfacial reactions and microstructure of the interfaces between the solders and the pads were observed using scanning electron microscopy and energy-dispersive spectrometry (EDS). Both solder joints on the two pads had similar interfacial microstructures; i.e., a very thin γ ₂-AuZn₃ layer was formed at the interface of the solder and Ni-P layer. The γ ₂-AuZn₃ layer transformed to an ε-AuZn₈ intermetallic compounds (IMC) with a consistent thickness during aging. Zinc atoms redeposited onto the IMC layer increased with increasing aging time. After aging at 150 °C for various times, the shear strengths of the ENIG and organic solderability preservative (OSP) joints were evaluated. The shear strength of the Sn-8Zn-3Bi solder joint was better than that of the Sn-9Zn-Al solder joint. All of the solder joints deteriorated after aging; however, the degradations of the OSP solder joints were more evident than those of the ENIG solder joints.     

不锈钢厂电弧炉粉尘中含铬相的形成

采用SEM-EDS和XPS对粉尘的微观结构和表面元素分布分别进行了检测,然后用FACTSage5.2软件通过热力学平衡计算研究了Cr-Fe-Zn-Mn-Mg-Al-Ca-Ni-O-Cl体系在尾气管中的演变行为,以及温度、氧气含量和粉尘中碱金属元素等对Cr-O2系统的影响.结果表明,计算结果和实验结果基本吻合.在Cr-O2体系中,Cr元素主要以Cr2O3形式稳定存在.在高温区均有少量的CrO3或CrO2生成,并且随着温度的升高,含量不断增加.在尾气系统中,氧势越高或者含氧量越多,越容易在高温区生成CrO3.在氧化性气氛中,碱金属的存在易于与Cr结合形成含Cr(Ⅵ)物相,如K2CrO4和Na2CrO4.     

Investigation of the effect of structural factors and surface composition on the properties of eutectic silver-copper solders used in vacuum technology

Structural changes that occur in silver-copper solders during their production with the use of new technological processes are considered. Metallography, electron microanalysis (EMA), and Auger electron analysis (AES) have been used to study changes at the contact surface of the material and their effect on the processes of solder flowing. The contents of alloying elements in phase constituents of the alloy have been determined. The composition of films formed on the surface of the material has been found. The data obtained allowed the optimization of the technological process of fabricating solders and increasing the quality of soldering.     

Determination of the melting and solidification characteristics of solders using differential scanning calorimetry

Differential scanning calorimetry (DSC) is used in the present study to determine the onset temperature of phase transformation and the enthalpy of fusion of various solder alloys. The solders studied are Sn-Pb, Sn-Bi, Ag-Sn, In-Ag, and Sn-Pb-Bi alloys. Very notable undercooling, such as 35 °C, is observed in the solidification process; however, a superheating effect is not as significant in the heating process. Besides the direct measurements of reaction temperature and heat of fusion, the fraction solid vs temperature has also been determined using a DSC coupled with a mathematical-model method. The heating and cooling curves of the solders are first determined using DSC. By mathematically modeling the heat transfer of the DSC cells, the heat evolution and absorption can be calculated, and then the melting and solidification curves of the solder alloys are determined. The three ternary alloys, Sn-35 wt pct Pb-10 wt pct Bi, Sn-45 wt pct Pb-10 wt pct Bi, and Sn-55 wt pct Pb-10 wt pct Bi, displayed similar DSC cooling curves, which had three reaction peaks. However, the solid fractions of the three alloys at the same temperature in the semisolid state, which had been determined quantitatively using the DSC coupled with a mathematical method, were different, and their primary solidification phases were also different.     

Effects of hospital downsizing on surviving staff

BACKGROUND/OBJECTIVE: Current albumin solders for tissue-welding are soluble in physiological fluids, prior to laser irradiation. These solders are therefore subjected to mechanical alterations, which can weaken the solder-tissue repair. In this study, an albumin solder (laser activated) was developed with low solubility and with the ability to retain (partially) its mechanical characteristics in saline solution. STUDY DESIGN/MATERIALS AND METHODS: Gauged protein samples of solder were immersed into 0.5 ml saline solution for fixed intervals of time. The solder samples contained four bovine serum albumin (BSA) concentrations: 56%, 66%, 70%, and 75% (by weight). A Bradford protein assay measured the BSA solubility of the solders. The 70% and 75% BSA solders were also used to weld in vitro Wistar rat intestine sections with a diode laser (lambda = 810 nm, power = 270 mW). RESULTS: The solubility of the 75% BSA solder was significantly decreased with respect to the other solders (Anova, P < 0.05). This solder also showed comparable weld strength (13 gm) to the 70% BSA solder. CONCLUSION: The 75% BSA solder strongly reduced the albumin solubility in saline solution, without affecting its tissue-welding properties.