Effect of TIG welding parameters in joining grade 2 pure titanium

Grade 2, the most widely used pure titanium in the industry, has high corrosion resistance, excellent ductility, good weldability and is easily machinable. If titanium is exposed to temperatures above 500 °C due to moisture or hydrocarbons in the air, it is susceptible to taking up oxygen, nitrogen, carbon and hydrogen. This can cause cracks, especially after welding. Therefore, protection of the welding zone from external factors is of great importance during welding. For these reasons, TIG welding is the most widely used method for titanium welding. In this study, Grade 2 pure titanium plates are joined by TIG welding at three (40 A, 60 A and 80 A) current values under the same conditions. For the welding process, 2 wt.-% cerium addition Tungsten tip and high purity (99.99 vol.-%) argon was used as a shielding gas. After a visual inspection of the welded samples, microstructure inspections, macrostructure inspections, hardness measurements, bending tests and tensile tests were performed in accordance with the standards. As a result of the investigations, it was determined that the most suitable current value for the joining of Grade 2 titanium by TIG welding was 60 A.

Numerical analysis of vibration modes of a qPlus sensor with a long tip

We study the oscillatory behavior of qPlus sensors with a long tilted tip by means of finite element simulations. The vibration modes of a qPlus sensor with a long tip are quite different from those of a cantilever with a short tip. Flexural vibration of the tungsten tip will occur. The tip can no longer be considered as a rigid body that moves with the prong of the tuning fork. Instead, it oscillates both horizontally and vertically. The vibration characteristics of qPlus sensors with different tip sizes were studied. An optimized tip size was derived from obtained values of tip amplitude, ratio between vertical and lateral amplitude components, output current, and quality factor. For high spatial resolution the optimal diameter was found to be 0.1 mm.

Manipulation Technique for Precise Transfer of Single Perovskite Nanoparticles

In this article, we present the pick-and-place technique for the manipulation of single nanoparticles on non-conductive substrates using a tungsten tip irradiated by a focused electron beam from a scanning electron microscope. The developed technique allowed us to perform the precise transfer of single BaTiO3 nanoparticles from one substrate to another in order to carry out measurements of elastic light scattering as well as second harmonic generation. Also, we demonstrate a fabricated structure made by finely tuning the position of a BaTiO3 nanoparticle on top of a dielectric nanowaveguide deposited on a glass substrate. The presented technique is based on the electrostatic interaction between the sharp tungsten tip charged by the electron beam and the nanoscale object. A mechanism for nanoparticle transfer to a non-conductive substrate is proposed and the forces involved in the manipulation process are evaluated. The presented technique can be widely utilized for the fabrication of nanoscale structures on optically transparent non-conductive substrates, which presents a wide range of applications for nanophotonics.

Field Emission Characterization of MoS2 Nanoflowers

Nanostructured materials have wide potential applicability as field emitters due to their high aspect ratio. We hydrothermally synthesized MoS2 nanoflowers on copper foil and characterized their field emission properties, by applying a tip-anode configuration in which a tungsten tip with curvature radius down to 30–100 nm has been used as the anode to measure local properties from small areas down to 1–100 µm2. We demonstrate that MoS2 nanoflowers can be competitive with other well-established field emitters. Indeed, we show that a stable field emission current can be measured with a turn-on field as low as 12 V/μm and a field enhancement factor up to 880 at 0.6 μm cathode–anode separation distance.

A Measurement Method of Microsphere with Dual Scanning Probes

The probe tip of a micro-coordinate Measuring Machine (micro-CMM) is a microsphere with a diameter of hundreds of microns, and its sphericity is generally controlled within tens to hundreds of nanometers. However, the accurate measurement of the microsphere morphology is difficult because of the small size and high precision requirement. In this study, a measurement method with two scanning probes is proposed to obtain dimensions including the diameter and sphericity of microsphere. A series of maximum cross-sectional profiles of the microsphere in different angular directions are scanned simultaneously and differently by the scanning probes. By integrating the data of these maximum profiles, the dimensions of the microsphere can be calculated. The scanning probe is fabricated by combining a quartz tuning fork and a tungsten tip, which have a fine vertical resolution at a sub-nano scale. A commercial ruby microsphere is measured with the proposed method. Experiments that involve the scanning of six section profiles are carried out to estimate the dimensions of the ruby microsphere. The repeatability error of one section profile is 15.1 nm, which indicates that the measurement system has favorable repeatability. The mainly errors in the measurement are eliminated. The measured diameter and roundness are all consistent with the size standard of the commercial microsphere. The measurement uncertainty is evaluated, and the measurement results show that the method can be used to measure the dimensions of microspheres effectively.

First-Principle Prediction on STM Tip Manipulation of Ti Adatom on Two-Dimensional Monolayer YBr3

Scanning tunneling microscopy (STM) is an important tool in surface science on atomic scale characterization and manipulation. In this work, Ti adatom manipulation is theoretically simulated by using a tungsten tip (W-tip) in STM based on first-principle calculations. The results demonstrate the possibility of inserting Ti adatoms into the atomic pores of monolayer YBr3, which is thermodynamically stable at room temperature. In this process, the energy barriers of vertical and lateral movements of Ti are 0.38 eV and 0.64 eV, respectively, and the Ti atoms are stably placed within YBr3 by >1.2 eV binding energy. These theoretical predictions provide an insight that it is experimentally promising to manipulate Ti adatom and form artificially designed 2D magnetic materials.

Nano-Scale Movement Induced In Graphene Ripples by Multi-Probe Microscopy

Abstract— An Omicron low temperature multi-probe technique is used for manipulation of mechanically exfoliated suspended and attached graphene sheets on SiO2 substrates. Scanning electron microscopy (SEM) and Raman spectroscopy are used to detect the graphene sheets and determine their thicknesses and quality, respectively. The interaction of the etched tungsten tip with the graphene is used to lift and release the sheet and induce artificial ripples. Both suspended and attached sheets onto the substrates show different behaviour in response to bias voltage. IndexTerms: graphene,multi-probe microscopy, ripples.