IRANIAN JOURNAL OF LABORATORY KNOWLEDGE
Year:2019 | Volume:7 | Issue:3 (27) |Papers Count:5

Just as for any other analytical technique, good sample preparation is essential for performing high-quality chemical analysis using X-ray fluorescence (XRF). There are 5 most common ways to prepare samples for XRF analysis. Whichever samples are being assessed – loose or pressed powders, fused beads, solid samples or liquids – finding the right approach to sample preparation is the first, and one of the most important steps in achieving accurate and reproducible results. We need to provide the requested information, as accurately, as repeatably, by different operators, as easily, as economically cost, as precisely and fast. At first must optimize grinding time to ensure that sample fineness is reached Sieve, granulometric determination or flour feel that Keeps sample homogeneous. Pellets prepare from the sample, which are two types: fused Pellets and pressed Pellets. In Fused pellets type, sample is melted by fuses, which are mostly compounds of boron (especially lithium borate). In pressed Pellets type, the powder of sample blend with an inert sticky material and then under pressure convert to Pellets, that can be put into the device. The other samples can be solid, liquid or Loose Powders.

Beam Deceleration is a relatively simple method to reduce electron beam energy and improve imaging parameters such as resolution and contrast. The scanning electron microscope (SEM) uses a sharply focused electron beam to probe the specimen surface. The energy of the electrons forming such a probe is determined by the electrical potential of the electron source, referred to as accelerating voltage or high voltage (HV). No matter how many times the electrons are accelerated or decelerated inside the column, they leave the column with an energy corresponding to the high voltage. The high voltage is usually controllable within a range of 200 V to 30 kV for most commercially available SEMs, allowing the operator to select the electron beam energy suitable for the application. Imaging with very low electron beam energy has great importance, which is illustrated by SEM instrumentation development over the last few decades. Low voltage microscopy is a topic discussed at most microscopyrelated conferences these days, but generally, it is approached with an immersion lens and field emission gun (FEG) SEM system because of the better beam current densities. However, beam deceleration is also a means to bring low kV improvement to SEMs with thermionic electron sources.

One of the current major driving forces behind instrument development in transmission electron microscopy (TEM) is the ability to observe materials processes as they occur in situ within the microscope. For many processes, such as nucleation and growth, phase transformations and mechanical response under extreme conditions, the beam current in even the most advanced field emission TEM is insufficient to acquire images with the temporal resolution (∼ 1 μ s to 1 ns) needed to observe the fundamental interactions taking place. The dynamic transmission electron microscope (DTEM) avoids this problem by using a short pulse laser to create an electron pulse of the required duration through photoemission which contains enough electrons to form a complete high resolution image. The current state-of-the-art in high time resolution electron microscopy in this paper describes the development of the electron optics and detection schemes necessary to fully utilize these electron pulses for materials science. In addition, developments for future instrumentation and the experiments that are expected to be realized shortly will also be discussed [53].

Fluidic force microscope (FluidFM) is a type of scanning probe microscope, and is typically used on a standard inverted light microscope. The unique characteristic of FluidFM is that it introduces microscopic channels into AFM probes. These channels can have an aperture of less than 300 nm. This nanometric features enables the handling of liquid volumes at the femtoliter (fL) scale. The universality and versatility of the FluidFM will stimulate original experiments at the sub micrometer scale not only in biology but also in physics, chemistry, and material science.