Determination of the Free Charge Carrier Concentration in Boron-Doped Silicon Nanowires Using Attenuated Total Reflection Infrared Spectroscopy

Semiconductors - Attenuated total reflection infrared spectroscopy is used to determine the free charge carrier concentration in arrays of silicon nanowires with characteristic transverse sizes of...     

Magnetic-field effect on the rheological properties of strontium ferrite suspensions

The effect of a magnetic field and surfactants on the rheological properties of strontium ferrite suspensions has been studied. An applied magnetic field is shown to raise the suspension viscosity, which is attributable to the formation of three-dimensional chain structures made up of ferrite particles. After the magnetic field is removed, these structures do not fully break down, which leads to hysteretic behavior of the suspension viscosity. The introduction of polyelectrolytes reduces the viscosity of the suspension both in a magnetic field and after the field is removed. This is due to the formation of an electrical double layer on the particle surface, which reduces interparticle friction and the strength of the three-dimensional structures. The results of this study may be useful in devising processes for enhancing the texture and density of highly anisotropic strontium ferrite materials produced by wet pressing.     

Fatigue life prediction of structural steel using acoustic birefringence and characteristics of persistent slip bands

Nondestructive evaluation methods provide additional information about the material fatigue behavior and enhance the comprehension of damage evolution thanks to relationship between microstructure and physical properties. This paper deals with optical and ultrasonic investigations of structural steel specimens tested for low-cycle fatigue. The development of persistent slip bands observed on the surface with an optical microscope was quantified using a previously trained neural network and fractal analysis. A surface damage parameter was defined as the ratio of total area of detected slip bands to the area of observed surface. Relationships between the rate of change and critical value of the damage parameter, the strain range, and the fatigue life were established. A single square relationship between relative number of cycles and ratio of the surface damage parameter to its critical value was obtained. Acoustic birefringence was measured by the echo method. The effect of the strain range on the rate of change in acoustic birefringence was investigated. A single linear relationship between relative number of cycles and change in acoustic birefringence was established. An algorithm for predicting the material remaining life, combining optical and ultrasonic data, was proposed.     

Efficiency of process methods for improving the surface quality and fatigue strength of gas-turbine engine disks of the KhN73MBTYu-VD alloy

The results of the present study suggest that a fatigue limit of the crown interslot projections of gas-turbine engine disks made of the KhN73MBTYu-VD alloy can be raised by subjecting the surface layer of the disk slots to ultrasonic hardening with balls. We attribute this to a removal of abrasive grits left by previous machining, to a decrease in depletion of the surface in alloying elements, and a simultaneous improvement in uniformity of the stress-strain state of various sections of the surface of a slot. Translated from Problemy Prochnosti, No. 5, pp. 126–133, September–October, 1998.     

Activation energy for the formation of oxygen vacancies in undoped nonstoichiometric indium oxide films

An analysis is made of the temperature dependence of the electrical conductivity of undoped nonstoichiometric indium oxide films. Activation energies are obtained for the formation of oxygen vacancies and for the mobility of quasifree carriers. Pis’ma Zh. Tekh. Fiz. 24, 1–5 (February 12, 1998)     

Optical properties of silicon nanowire arrays formed by metal-assisted chemical etching: evidences for light localization effect

We study the structure and optical properties of arrays of silicon nanowires (SiNWs) with a mean diameter of approximately 100 nm and length of about 1–25 μm formed on crystalline silicon (c-Si) substrates by using metal-assisted chemical etching in hydrofluoric acid solutions. In the middle infrared spectral region, the reflectance and transmittance of the formed SiNW arrays can be described in the framework of an effective medium with the effective refractive index of about 1.3 (porosity, approximately 75%), while a strong light scattering for wavelength of 0.3 ÷ 1 μm results in a decrease of the total reflectance of 1%-5%, which cannot be described in the effective medium approximation. The Raman scattering intensity under excitation at approximately 1 μm increases strongly in the sample with SiNWs in comparison with that in c-Si substrate. This effect is related to an increase of the light-matter interaction time due to the strong scattering of the excitation light in SiNW array. The prepared SiNWs are discussed as a kind of ‘black silicon’, which can be formed in a large scale and can be used for photonic applications as well as in molecular sensing.     

Ultrasonic and Eddy-Current Fatigue Monitoring of Austenitic Steel Welded Joints

Russian Journal of Nondestructive Testing - We investigated the process of fatigue damage in welded joints made of austenitic steel by ultrasonic and eddy current types of testing. The development...