电子束端面熔炼法制备高纯钨的研究

采用250 kW的电子束熔炼炉对纯度为99.955%的钨棒进行提纯研究,利用扫描电镜、电感耦合等离子体光谱法(ICP-MS)和微米压痕仪分别对原料钨棒和熔炼后钨锭的形貌、纯度和显微硬度进行观察和测试.研究表明:在电子束轰击原料钨棒的过程中,钨棒端面的边缘最先熔化;经电子束熔炼后,钨棒的整体纯度显著提高,达到了99.975%,间隙杂质O和C的脱除率分别达到55.5%和45.8%;非间隙杂质的蒸汽压与脱除率密切相关,高蒸汽压的杂质元素Cd、As、K、Mg脱除较为完全,其脱除率分别为95%、90%、75%和71.4%,在钨棒中含量分别降至1、1、5和10μg/g.     

Semiconductor surface doping by electron beam melting of thin evaporated layers

We have studied the distribution profiles of Cu and Sb introduced into Si substrates, and Sb introduced into Ge substrates by electron beam melting of thin (～30nm) layers of the dopant evaporated onto the substrate. Surface evaporation of the dopant during melting was reduced by a cover layer of the substrate material evaporated on top. We propose a novel model which explains solute surface accumulation phenomena oberved in laser and electron beam surface melting experiments. It is based on a mechanism of solute immobilization at the very surface.     

The effect of a low-energy high-current pulsed electron beam on surface layers of porous zirconium ceramics

The effect of a high-current pulsed electron beam of low-energy electrons on surface layers of porous zirconium ceramics has been studied. It is established that electron treatment leads to melting of the surface layer and its subsequent crystallization accompanied by the formation of a microstructure differing from the initial state. It is established that porosity decreases in the treatment region, the size of grains increases, and their shape changes. Grains are found to arrange themselves in the direction to the sample surface. Their linear sizes in the transverse and longitudinal directions are, respectively, 1.4 and 7 μm on average, i.e., differ significantly. It is shown that the surface layer modified by an electron beam is characterized by elevated microhardness as compared with the initial state.     

Formation of interstitial atoms in surface layers of helium-implanted tungsten

Using a method of field ion microscopy, the atomic structure of surface and near-surface layers of a perfect dislocation-free tungsten irradiated by helium ions with energies below the threshold of displacement was studied. We have found the output of tungsten atoms from the bulk as a result of their displacement from regular lattice positions occupied by implanted helium atoms and the formation of interstitial tungsten atoms. It is shown that high concentrations of helium and the presence of image forces have a considerable effect on the development of these processes. Depleted zones consisting of helium-vacancy complexes are revealed within the irradiated near-surface layer.     

Effect of an electron beam surface treatment on the microstructure and mechanical properties of SAF 2205 joints produced with electron beam welding

The aim of present investigation is to study the effect of an electron beam surface treatment on 2205 duplex stainless steel joints produced by the same electron beam process. Heat treatment of the joints is necessary, to re-establish the ferrite/austenite balance, which is extremely disturbed during the electron beam welding process. For assessing the effectiveness of the electron beam surface treatment, similar weld joints were subjected to conventional furnace heat treatment at 1050 °C, and used as reference. Metallographic techniques and mechanical testing were used to assess the microstructure and corresponding mechanical properties of the as-welded and heat treated specimens. The metallographic results showed that an austenite/ferrite ratio approaching the one produced by a typical furnace post-weld heat treatment can also be achieved by heating locally the weld surface with an electron beam. At the same time the tensile properties show considerable improvement, approaching those obtained by means of a conventional furnace heat treatment, whereas the impact strength is also improved compared to the as welded specimen, but remains clearly lower than the one of the furnace heat treated weld.     

电子束熔炼制备块体钨的组织与显微硬度研究

钨材料具有极高的熔点,传统上采用粉末冶金方法制备,获得的钨材料具有晶粒细小、微观组织均匀等优点, 但致密性不足。为进一步提升钨材料的性能,本研究将98.3%的钨粉和1.7%的碳粉均匀混合,在1 800 ℃、26 MPa条件下热压成型,而后采用电子束熔炼技术对成型后的钨块进行熔炼,利用金相显微镜、SEM、显微硬度计等对其显微组织、致密度和显微硬度进行评价,并与传统粉末冶金法制备的块体钨的性能进行了对比。结果表明:电子束熔炼制备的钨锭冶金质量好,致密度可达99.8%;试样的显微硬度达到9.16 GPa,显著高于粉末冶金法制备的块体钨材料,突破了热压烧结工艺制备块体钨的致密度-显微硬度的关系;经1 300 ℃、6 h退火热处理后,显微硬度略有下降,但仍达到8.86 GPa,显示出电子束熔炼技术在制备块体钨硬度性能方面的优势。     

High speed scanning electron beam annealing of ion-implanted silicon layers

Sawtooth scanning with a 40 keV electron probe at frequencies of 10⁵–10⁶ Hz can be used for generating in a silicon surface a quasi-line-shaped temperature field. With a power of 70–80 W and a spot diameter of 50 μm this yields a surface temperature of about 1500 K. The procedure was tentatively used for solid state annealing of ⁷⁵As-ion-implanted silicon layers to a depth of 1000 Å. These beam parameters permit an areal throughput of 10 cm² s^-1 without back side cooling since the substrate temperatures at the back side can be kept below 800 K.     

Self-assembled tungsten oxide nanowires by electron beam assisted rapid thermal annealing

We report on the fabrication of WO₃ nanowires on Si (100) substrate using nickel catalyzed electron beam assisted rapid thermal annealing process. A 7 nm thick W layer deposited on the nickel coated substrate was annealed under high vacuum using electron beam (3 keV) for 30, 60 and 90 s. The nickel activates the growth of tungsten nanowires with a high aspect ratio and subsequently is oxidized due to the high refractory nature of tungsten under exposure to oxygen gas. The resulting changes in surface morphology, oxidization state and elemental composition of WO₃ nanowires were investigated systematically. The oxidization of metallic tungsten nanowire was found to depend on the annealing time.     

Doping of silicon by pulsed electron beam annealing of deposited layers

Pulsed electron beam annealing was applied to p-type silicon wafers coated with vacuum-deposited antimony layers to obtain p-n junctions. Antimony atoms were found to migrate into the substrate to a distance fo 2000–3000 Å. The antimony-doped layer shows two different regions. The top surface layer is highly conductive and has a textured structure. The deeper region contains highly substitutional antimony with a concentration exceeding the solid solubility limit. However, only 4% of the antimony is electrically active. The penetration depth of the antimony atoms and the formation of the supersaturated solution indicate that melting is induced by the irradiation. Electrically the samples exhibit diode characteristics.     

Relativistic electron beam induced amplification of surface wave propagating over a corrugated metal surface

An impedance model is constructed in the framework of a quasi-optical approach, which describes the propagation of radiation over a corrugated metal surface and its amplification by a rectilinear relativistic electron beam. It is shown that this scheme can provide effective amplification of radiation in a submillimeter wavelength range.     

Exchange-induced self-polarization of an electron beam

A mechanism leading to self-polarization of a beam of free electrons injected from a light-emitting cathode is considered. It is shows that the exchange interaction may lead to self-polarization of an electron beam in vacuum and maintain the polarization of a beam in a substance.     

Luminescence of some oxygen-octahedric ferroelectrics exposed to an electron beam

Spectral and temperature dependence of cathodo luminescence (CL) was studied in oxygen-octahedric ferroelectrics Ba_XSr_1-XNb₂O₆, $\text{PbMg}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{O}{}_3$, LiNbO₃, SrTiO₃, Ba₂NaNb₅O₁₅, and PLZT-ceramics. CL in these materials is of admixture type. In the region of ferroelectric phase transition (PT) of Ba_XSr_1-XNb₂O₆ and $\text{PbMg}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{O}{}_3$ an anomaly in CL is observed. Redistribution of recombination flows between the centers of radiative and non-radiative recombinations in PT region due to variation of dielectric constant is proposed to account for this phenomenon.     

Generation of bremsstrahlung by an electron beam

The problem of generation of x- and y-radiations in interaction of an electron beam with a layer of a substance having a large Z is considered theoretically. Energy and angular spectra of bremsstrahlung are obtained for various energies of the electron beam. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 5, pp. 887–890, September–October, 1998.     

Thermoelasticity analysis of functionally graded beam with integrated surface piezoelectric layers

This paper presents analytical solution for functionally graded material (FGM) beams integrated with piezoelectric actuator and sensor under an applied electric field and thermo-mechanical load. In FGM host properties is assumed to vary exponentially in thickness direction and the Poisson’s ratio is held constant. The hybrid beam is in a state of plane stress and the piezoelectric is composed of orthotropic materials. The beam is simply supported with the bottom surface traction free and zero temperature. By using of state-space method in thickness direction and Fourier series in longitudinal direction, the solution can be made. To verify the accuracy of the present formulation, numerical results for the simple case is compared with results obtained in the published literature. Finally, effects of FGM index, electromechanical coupling, thickness ratio and thermo-mechanical surface boundary condition on the bending behaviour of beam are investigated.     

Carbon clusters in an electron beam evaporator

A time-of-flight mass spectrometer was used to study carbon clusters produced by electron beam evaporation. The studies concentrated on clusters already ionized in the evaporator. It was established that the mass distribution changed as a function of the time of evaporation. In the initial stage a broad distribution consisting of clusters of 1–10 atoms was observed, with the maximum of the distribution at the trimers. After repeated heating and cooling procedures, the initiallybroad distribution changed, showing clear-cut peaks at one-, two- and three-atom clusters respectively. Simultaneously, the concentrations of ions with masses 2 a.m.u.(H₂⁺) and 28 a.m.u.(Co⁺) increased together with that of H₂O⁺, the last increase probably resulting from a water-gas reaction. Likewise, the proportion of ions with mass 44 a.m.u.(Co₂⁺) increased. Owing to the temperature rise during longer evaporation times, the higher masses of carbon disappeared and only the 12 a.m.u. mass was observed.     

Application of accelerated electron beam and microwave irradiation to biological waste treatment

The comparative results obtained by applying separate electron beam (EB) irradiation, separate microwave (MW) heating and combined (successive and simultaneous) electron beam irradiation and microwave heating to reduction of viable cells of Escherichia coli, Salmonella typhi, Staphylococcus intermedius, Pseudomonas aeruginosa, and Trichinella spiralis are presented. The results of studies concerning the disinfection by separate and combined EB and MW irradiation of sewage sludge performed from a food industry wastewater treatment station (vegetable oil plant) are also presented. The research results demonstrated that the simultaneous EB and MW irradiation produces the biggest reduction of microorganisms.