A double toroidal analyzer for scanning probe electron energy spectrometer

An ultra-high vacuum （UHV） compatible electron spectrometer employing a double toroidal analyzer has been de- veloped. It is designed to be combined with a custom-made scanning tunneling microscope （STM） to study the spatially localized electron energy spectrum on a surface. A tip-sample system composed of a piezo-driven field-emission tungsten tip and a sample of highly ordered pyrolytic graphite （HOPG） is employed to test the performance of the spectrometer. Two-dimensional images of the energy-resolved and angle-dispersed electrons backscattered from the surface of HOPG are obtained, the performance is optimized and the spectrometer is calibrated. A complete electron energy loss spectrum covering the elastic peak to the secondary electron peaks for the HOPG surface, acquired at a tip voltage of -140 V and a sample current of 0.5 pA, is presented, demonstrating the viability of the spectrometer.

Detection of distribution of copper inside and outside of lysosomes in cultured hepatolenticular degeneration fibroblasts by electron probe X-ray microanalysis

OBJECTIVE: To observe the distribution of copper in the subcellular structure for the understanding of primary pathogenesis of hepatolenticular degeneration (HLD). METHODS: Skin fibroblasts taken from HLD patients were cultured as an in vitro model of HLD, and the control cells taken from healthy volunteers were clutured in the same way. The distribution of copper inside and outside of lysosomes in fibroblasts was detected by quantitative electron probe X-ray microanalysis. The relationship between the subcellular location of copper and the genotype of the patients, and relationship between the distribution of copper and the course of the disease were analyzed. RESULTS: The content of Cu^(2+) inside lysosomes of HLD cells (14.6±2.1 mmol/kg) and of heterozygote cells (11.6±0.6 mmol/kg) was higher than that of normal cells (4.5±1.2 mmol/kg) (P<0.01). The content of Cu^(2+) outside lysosomes of HLD cells (17.5±4.2 mmol/kg) and of heterozygote cells (12.0±0.9 mmol/kg) was higher than that of normal cells (4.7±1.2 mmol/kg) (P<0.01). The distribution of copper in the subcellular structure was correlated with disease courses of HLD patients. With the progression of the disease, more copper was deposited in lysosomes (r=0.85, P<0.01). The content of copper in the diffused cytoplasmic compartment in HLD cells was correlated with that of sulfur (r=0.86, P<0.05), but not in heterozygote and normal cells. CONCLUSIONS: In the early stage of HLD, copper is accumulated outside lysosome, which is paralleled with increase of metallothionein-like proteins (copper and sulfur-binding proteins). With the development of the disease, more copper is deposited inside lysosome than outside lysosome. We conclude that the up-regulation expression of copper and sulfur-binding proteins and copper accumulation in lysosomes may play an important role in lowering the ATP7B gene mutation-induced toxic effects of free copper on the cell.

Process mineralogy and characteristic associations of iron and phosphorus-based minerals on oolitic hematite

The chemical compositions,mineralogical characteristics,as well as dissemination of iron-and phosphorus-based minerals were studied for the E’xi oolitic hematite from western Hubei Province in China by using chemical analysis,optical microscope,electron probe micro-analyzer(EPMA)and energy dispersive spectroscopy(EDS).It is found that this kind of oolitic hematite ore contains 47.71%TFe,10.96%SiO_2,as well as 0.874%P,with hematite as the dominant Fe-bearing minerals,and quartz,chamosite,illite and cellophane as main gangue minerals.The microscope examination showed that the ore has an oolitic structure,with some ooids principally formed by a series of concentric layers of hematite collophanite around nucleus that is hematite in the association with collophanite.Based on the EPMA and EDS analysis,it can be known that some ooids are primarily composed of hematite and collophanite.The separation can be achieved through fine grinding for those collophanite laminae with a higher P content.However,the dissemination of two minerals at the interface will result in the difficulty in effective separation.Besides,some ooids are made of chamosite with some nucleus formed of quartz,which is principally finely disseminated with hematite.In view of the close association and dissemination of iron-and phosphorus-based minerals in the ooids,it is found that the process of stage-grindings and stage-separations can be adopted to effectively increase the iron recovery and decrease the P content in the concentrate to some extent.

Simulation on scrap melting behavior and carbon diffusion under natural convection

A 3D model applying temperature-and carbon concentration-dependent material properties was developed to describe the scrap melting behavior and carbon diffusion under natural convection.Simulated results agreed reasonably well with experimental ones.Scrap melting was subdivided into four stages:formation of a solidified layer,rapid melting of the solidified layer,carburization,and carburization+normal melting.The carburization stage could not be ignored at low temperature because the carburization time for the sample investigated was 214 s at 1573 K compared to 12 s at 1723 K.The thickness of the boundary layer with significant concentration difference at 1573 K increased from 130μm at 5 s to 140μm at 60 s.The maximum velocity caused by natural convection decreased from 0.029 m·s^(−1)at 5 s to 0.009 m·s^(−1)at 634 s because the differences in temperature and density between the molten metal and scrap decreased with time.

Interdiffusion in the Fe_2O_3-TiO_2 system

Interdiffusion in the Fe203-TiO2 system was investigated by the diffusion couple method in the temperature range of 1323 to 1473 K. The diffusion concentration curves of Ti4＋ cations were obtained by electron probe microanalysis, according to which the Boltzmann-Matano method optimized by Broeder was used to calculate the interdiffusion coeffi- cients. The interdiffusion coefficients almost increased linearly with the mole fraction of Ti4＋ cations increasing, and they were in the range of 10-12-10-11cm2-s-1. The increase of temperature could also lead to the increase of the interdiffusion coefficients at a constant concentration of Ti4＋ cations. It was also found that the thickness growth of the diffusion layer obeyed the parabolic rate law.

EPMA Study of the Interface of β-Tricalcium Phosphate Ceramies in Vivo

Electron probe and X-ray energy spectrum were used to investigate the chemical composition of the interface between material and new bone after porous tricalcium phosphate ceramie implanted in tibia of rabbits. The element changes of the interface, the materials transformation and the situation of new bone formation at different implantation period were observed. The results showed that the carbon element content decreased gradually in new bone tissue, and the content of calcium and phosphor element increased by degrees with the implantation time. At the same time, calcium-phosphor ratio in the new bone kept a higher Ievel. New bone grew into the materials interior, material dispersed and degraded simultaneously. Both composition of materials and new bone tended to be consentient. Finally, the materials were substituted by new bone. After implantation, not only the materials itself dissolved and degraded partially, but also new bone formed on the outer and pore surface of β-TCP porous bioceramics, which shovved that the degradation products of lifeless calcium phosphate inorganic materials took part in constituting of new bone tissue.

Determination of phase diagrams using the diffusion couple technique

It has been demonstrated that the diffusion couple technique is a powerful and efficient approach in establishing phase relationships of ternary systems. Accurate data on the phase equilibria can be obtained if the appropriate alloys are employed as end members of the diffusion couple. It is desirable to combine the diffusion couple technique with an investigation of the afterwards selected equilibrated alloys so that the precision and reliability of the obtained information about a ternary isotherm could be guaranteed.

Effects of the precipitation of stabilizers on the mechanism of grain fracturing in a zirconia metering nozzle

The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.

Phase Equilibria in Zn-Al-Cu-Si System at 285℃

As a part of the systematic investigation on phase relationships of Zn-Al based alloys containing Cu and/or Si, the equilibrium phase transformations of the quaternary Zn-Al-Cu-Si system at 285℃ were investigated by using X-ray diffracti on, scanning electron microscopy and electron probe microanalysis techniques. A five-phase of (α+β+εT'+σ) and a four- phase of (β+ε+η+σ) were detected separately coexisting in the Zn-Al-Cu-Si system at 285℃. Then the 285℃ isothermal section of Zn-Al-Cu-Si system (with 0.1% -Si content) was established, and an equilibrium reaction was determined at 286℃ as the following pattern, β+T'=α+ε

Microstructural evaluation of Hastelloy-X transient liquid phase bonded joints:Effects of filler metal thickness and holding time

Transient liquid phase(TLP)bonding was investigated in Hastelloy-X samples with different filler metal thicknesses(20,35,50,65,and 100μm)and holding time(5,20,80,320,and 640 min)to obtain optimum bonding parameters.Microstructural evaluations using electron probe microanalysis(EPMA)and electron backscattered diffraction(EBSD)show that the central eutectic phases present in the athermally solidified zone(ASZ)are Ni_(3)B,Ni_(2)Si,and CrB,and the precipitates formed in the diffusion-affected zone(DAZ)are MoB,CrB_(2),and Mo_(2)B_(5).According to the results,decreasing the filler thickness as well as increasing the holding time helps realize the completion of isothermal solidification and reduction in the density of precipitates in the DAZ,leading to a joint with more uniform properties.Diffusion of boron and silicon to longer distances with increasing holding time causes the removal of Cr-rich borides in the DAZ and the formation of Mo-rich silicide at the joint interface.Decrease in hardness of ASZ and DAZ due to the elimination of brittle phases in these zones during long holding time causes more uniform hardness distribution in the joint area.The best results are obtained for the sample joined with the 35μm-thick filler metal for 640 min holding time.

Phase equilibria in Ni-Ti-Ta ternary system

Phase diagrams of two isothermal sections of the Ni-Ti-Ta ternary system at 1000 and 1200℃in a full composition range were determined by X-ray diffraction and electron probe microanalysis.The experimental results indicated a ternary compoundτphase with low solid solubility and composition ranges of(16.3-22.4)at.%Ta,(15.9-24.1)at.%Ti and(58.5-60.0)at.%Ni at 1000℃.The two terminal solid solutions(bcc-(Ta)andβ-Ti)formed a continuous solid solution at 1000 and 1200℃.A certain amount of Ti can dissolve into Ni-Ta intermetallic compounds near the Ni-Ta side,with the highest value of 21.9 at.%observed in the Ni;Ta compound at 1000℃.

Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner

Phase equilibria of the Mg-Sn-Ag system in Mg-rich corner at 320 and 400℃ were experimentally investigated with nine ternary alloys subjected to electron probe microanalysis and X-ray diffraction techniques.No ternary compounds were observed at both isothermal sections.Two three-phase triangles,i.e.hcp(Mg)+Mg_(2)Sn+Mg_(3)Ag and Mg_(2)Sn+Mg_(3)Ag+MgAg(bcc_B2),were both observed at 320 and 400℃.A new three-phase region of Ag3Sn+Mg2Sn+MgAg(bcc_B2)was additionally observed at 320℃,which implied that the binary phase Ag3Sn has a considerable solubility of Mg in the ternary system at the temperature.And the maximal solubility of Mg in Ag3Sn was measured to be 27.2 at.%.This result is not consistent with the thermodynamic calculated isothermal section at 350℃ from Wang et al.[11]and put forward a new requirement or refinement for the optimization of the Mg-Sn-Ag ternary system.At 400℃,the maximal solubility of Sn in the Mg3Ag phase was determined to be about 3.0 at.%Sn,and the solubility of Ag in Mg2Sn was negligible.The temperature of ternary eutectic reaction at Mg-rich corner(L↔hcp(Mg)+Mg_(54)Ag_(17)+Mg_(2)Sn)was measured by differential scanning calorimetry.The partial isothermal sections in Mg-rich corner of the ternary system at 320 and 400℃ were then constructed based on the above experimental data.

Electron Energy Spectroscopic Mapping of Surface Plasmon by Parallel Scanning Method

In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning probe electron energy spectrometer,a multi-channel detection mode is developed.By scanning along one direction,the two-dimensional intensity distribution of Ag surface plasmon excitation due to the collision of electron emitted from the tip can be obtained in parallel.The spectroscopic spatial resolution is determined to be around 80 nm.

Correlation ofⅢ/Ⅴsemiconductor etch results with physical parameters of high-density reactive plasmas excited by electron cyclotron resonance

Reactive ion etching is the interaction of reactive plasmas with surfaces. To obtain a detailed understanding of this process, significant properties of reactive composite low-pressure plasmas driven by electron cyclotron resonance（ECR） were investigated and compared with the radial uniformity of the etch rate. The determination of the electronic properties of chlorine-and hydrogen-containing plasmas enabled the understanding of the pressure-dependent behavior of the plasma density and provided better insights into the electronic parameters of reactive etch gases. From the electrical evaluation of I（V） characteristics obtained using a Langmuir probe,plasmas of different compositions were investigated. The standard method of Druyvesteyn to derive the electron energy distribution functions by the second derivative of the I（V）characteristics was replaced by a mathematical model which has been evolved to be more robust against noise, mainly, because the first derivative of the I（V） characteristics is used. Special attention was given to the power of the energy dependence in the exponent. In particular, for plasmas that are generated by ECR with EM modes, the existence of Maxwellian distribution functions is not to be taken as a self-evident fact, but the bi-Maxwellian distribution was proven for Ar-and Kr-stabilized plasmas. In addition to the electron temperature, the global uniform discharge model has been shown to be useful for calculating the neutral gas temperature. To what extent the invasive method of using a Langmuir probe could be replaced with the noninvasive optical method of emission spectroscopy, particularly actinometry, was investigated,and the resulting data exhibited the same relative behavior as the Langmuir data. The correlation with etchrate data reveals the large chemical part of the removal process—most striking when the data is compared with etching in pure argon. Although the relative amount of the radial variation of plasma density and etch rate is approximately ？5%, the etch rate shows a slightly concave shape in contrast to the plasma density.

Geochronology,petrogenesis,and geological significance of the quartz vein-type copper deposits in Longwei area,north-west Dayaoshan,Guangxi

Quartz-vein-type copper deposits were discovered in SN-trend ore-bearing structures in north-west Dayaoshan,Guangxi.Lack of reports on the precise metallogenic age of these deposit has become a bottleneck in metallogenic research in this area.In this study,the quartz vein-type copper mine in Longwei area of Jinxiu was selected as the research object.Fresh illite samples in the fault gouges and ore samples were collected for testing and analysis.Based on the Re-Os isotope dating study,the age of pyrite isochron,belonging to the Caledonian period,was determined to be 417±25 Ma,whereas that of chalcopyrite isochron belonging to the Indosinian period,was found to be 243±18 Ma.Pyrite crystallized considerably earlier than chalcopyrite.The obtained EPMA data were combined with rock mineralogical analysis data,Metasomatous mineral pyrite and metasomatic mineral chalcopyrite were identified to have originated from different hydrothermal systems.In the Indosinian period,copper deposits in the Longwei area underwent pyrite crystallization,pyrite fragmentation,copper-bearing hydrothermal filling,and metasomatism,consolidating and forming minerals.The study determined the mineralisation time and ore sources of copper deposits in the Longwei area.The study provides evidence for the existence of Indosinian hydrothermal activities in the north-western Dayaoshan area.

Electron probe microanalysis for revealing occurrence mode of scandium in Bayer red mud

Red mud is a bauxite residue generated during the process of alumina production. In this research, the occur- rence mode of scandium in the Bayer red mud was investi- gated mainly by electron probe microanalysis （EPMA）. The Bayer red mud used in this work is composed of 21.47 wt% hematite, 12.13 wt% goethite, 8.86 wt% gibbsite, 5.02 wt% perovskite, 9.70 wt% quartz, 3.23 wt% anhydrite, 29.92 wt% Na_2Al_2Si_5O_14 and 9.67 wt% Al_3Fe_5O_12. Besides, the scandium content in the Bayer red mud is 84.32 × 10-6, indicating that this Bayer red mud is an important scandium resource deserving exploitation. The EPMA results show that the scandium within the Bayer red mud is mainly occurring in the iron minerals of hematite and goethite with the isomorphism form, but its distribution is not homogeneous in these iron minerals with the Sc_2O_3 content between 330 × 10-6 and 2040 × 10-6. This study provides a theoretical base for the further experimental work on the scandium extraction from this Bayer red mud.

Beam distribution reconstruction simulation for electron beam probe

An electron beam probe（EBP） is a detector which makes use of a low-intensity and low-energy electron beam to measure the transverse profile, bunch shape, beam neutralization and beam wake field of an intense beam with small dimensions. While it can be applied to many aspects, we limit our analysis to beam distribution reconstruction.This kind of detector is almost non-interceptive for all of the beam and does not disturb the machine environment.In this paper, we present the theoretical aspects behind this technique for beam distribution measurement and some simulation results of the detector involved. First, a method to obtain a parallel electron beam is introduced and a simulation code is developed. An EBP as a profile monitor for dense beams is then simulated using the fast scan method for various target beam profiles, including KV distribution, waterbag distribution, parabolic distribution,Gaussian distribution and halo distribution. Profile reconstruction from the deflected electron beam trajectory is implemented and compared with the actual profile, and the expected agreement is achieved. Furthermore, as well as fast scan, a slow scan, i.e. step-by-step scan, is considered, which lowers the requirement for hardware, i.e. Radio Frequency deflector. We calculate the three-dimensional electric field of a Gaussian distribution and simulate the electron motion in this field. In addition, a fast scan along the target beam direction and slow scan across the beam are also presented, and can provide a measurement of longitudinal distribution as well as transverse profile simultaneously. As an example, simulation results for the China Accelerator Driven Sub-critical System（CADS） and High Intensity Heavy Ion Accelerator Facility（HIAF） are given. Finally, a potential system design for an EBP is described.

A sensitive charge scanning probe based on silicon single electron transistor

Single electron transistors（SETs） are known to be extremely sensitive electrometers owing to their high charge sensitivity. In this work, we report the design, fabrication, and characterization of a silicon-on-insulatorbased SET scanning probe. The fabricated SET is located about 10 m away from the probe tip. The SET with a quantum dot of about 70 nm in diameter exhibits an obvious Coulomb blockade effect measured at 4.1 K. The Coulomb blockade energy is about 18 me V, and the charge sensitivity is in the order of 10^-（5）–10（^-3）e/Hz^（1/2）. This SET scanning probe can be used to map charge distribution and sense dynamic charge fluctuation in nanodevices or circuits under test, realizing high sensitivity and high spatial resolution charge detection.

Depositional Environments of the Upper Permian Quartzose Sandstone(Shandong Province, North China): Insight from Trace Element Geochemistry

The depositional environment of the Upper Permian quartzose sandstone （Kuishan sandstone in Shihezi Formation of Upper Permian） in the North China epicontinental basin is controversial. In order to test the previous hypotheses, we analyzed sedimentological characteristics of the Kuishan sandstones in outcrops and boreholes, and carried out trace element geochemical analysis by electron probe microanalyzer. Three lithofacies were recognized, including normal-graded conglomerate （Cng）, trough and planar cross-bedded coarse sandstone （CStpc）, and planar cross-bedded medium sandstone （MSpc）. Normal-graded conglomerate （Cng） formed in the meandering river or deltaic distributary channels. Trough and planar cross-bedded coarse sandstone （CStpc） formed in meandering river or distributary channels of near-source deltaic plain. Planar cross-bedded medium sandstone （MSpc） formed in the siliciclastic beach with highto moderate-energy conditions. By the petrology and trace elements analysis, three relatively large-scale transgressions were revealed. Each transgression was reflected by the lower content of Ba and ratios of Fe/Mn, and the high content of B and ratios of B/Ga. The ratios of Ni/Co of all samples are all lower than 2, suggesting oxygen-enriched shallower water en- vironment during deposition of the Kuishan sandstones.

Effect of Ce on solute redistribution in liquid ahead of solid–liquid interface during solidification of Fe–4 wt.%Si alloy

The high efficiency of Ce addition in grain refinement ofδ-ferrite in a cast Fe–4 wt.%Si alloy was verified.In order to further understand the solute effect of Ce on the grain refinement of δ-ferrite,the conventional directional solidification technique,which enabled to freeze the solid–liquid interface to room temperature,was used to investigate the interfacial morphology and solute redistribution in the liquid at the front of the interface,together with thermodynamic calculation of the equilibrium partition coefficients of Ce and Si in Fe–4 wt.%Si–Ce system using the Equilib module and the FsStel database in FactSage software system.Metallographic examination using a laser scanning confocal microscope showed a transition of the solid–liquid interface from planar to cellular in the Fe–4 wt.%Si alloy after adding 0.0260 wt.%Ce during the directional solidification experiment.Further,electron probe microanalysis revealed an enhanced segregation of Si solute in the liquid at the front of the solid–liquid interface due to the Ce addition.This solute segregation is considered as the cause of planar to cellular interface transition,which resulted from the creation of constitutional supercooling zone.Thermodynamic calculation indicated that Ce also segregated at the solid–liquid interface and the Ce addition had negligible effect on the equilibrium partition coefficient of Si.It is reasonable to consider that the contribution of Ce to the grain refinement ofδ-ferrite in the cast Fe–4 wt.%Si alloy as a solute was marginal.