Conventional Sample Holders Research Articles

X-ray computed tomography with seven degree of freedom robotic sample holder

We present an x-ray Computed Tomography setup that integrates a seven degrees of freedom robotic arm as a sample holder within an existing laboratory x-ray computed tomography setup. We aim to provide a flexible sample holder that is able to execute non-standard and task-specific trajectories for complex samples. The robotic arm is integrated with a unified software package that allows for path planning, collision detection, geometric calibration and reconstruction of the sample. The calibration is necessary to identify the accurate pose of the sample which deviates from the expected pose due to inaccurate placement of the robotic arm. With our software the user is able to command the robotic arm to execute arbitrary trajectories for a given sample in a safe manner and output its reconstruction to the user. We present experimental results with a circular trajectory where the robotic sample holder achieves identical visual quality compared to a conventional sample holder.

Stroboscopic ultrafast imaging using RF strip-lines in a commercial transmission electron microscope

The development of ultrafast electron microscopy (UEM), specifically stroboscopic imaging, has brought the study of structural dynamics to a new level by overcoming the spatial limitations of ultrafast spectroscopy and the temporal restrictions of traditional TEM simultaneously. Combining the concepts governing both techniques has enabled direct visualization of dynamics with spatiotemporal resolutions in the picosecond-nanometer regime. Here, we push the limits of imaging using a pulsed electron beam via RF induced transverse deflection based on the newly developed 200 keV frequency-tunable strip-line pulser. We demonstrate a 0.2 nm spatial resolution and elucidation of magnetic spin induction maps using the phase-microscopy method. We also present beam coherence measurements and expand our study using the breathing modes of a silicon interdigitated comb under RF excitation which achieves improved temporal synchronization between the electron pulse-train and electric field. A new RF holder has also been developed with impedance matching to the RF signal to minimize transmission power loss to samples and its performance is compared with a conventional sample holder.

A Simple Preparation Method for Full-Range Electron Tomography of Nanoparticles and Fine Powders.

Electron tomography has become a valuable and widely used tool for studying the three-dimensional nanostructure of materials and biological specimens. However, the incomplete tilt range provided by conventional sample holders limits the fidelity and quantitative interpretability of tomographic images by leaving a "missing wedge" of unknown information in Fourier space. Imaging over a complete range of angles eliminates missing wedge artifacts and dramatically improves tomogram quality. Full-range tomography is usually accomplished using needle-shaped samples milled from bulk material with focused ion beams, but versatile specimen preparation methods for nanoparticles and other fine powders are lacking. In this work, we present a new preparation technique in which powder specimens are supported on carbon nanofibers that extend beyond the end of a tungsten needle. Using this approach, we produced tomograms of platinum fuel cell catalysts and gold-decorated strontium titanate photocatalyst specimens. Without the missing wedge, these tomograms are free from elongation artifacts, supporting straightforward automatic segmentation and quantitative analysis of key materials properties such as void size and connectivity, and surface area and curvature. This approach may be generalized to other samples that can be dispersed in liquids, such as biological structures, creating new opportunities for high-quality electron tomography across disciplines.

Terahertz Bandpass Frequency Selective Surfaces on Glass Substrates Using a Wet Micromachining Process

This paper presents terahertz (THz) frequency selective surfaces (FSS) implemented on glass substrate using standard microfabrication techniques. These FSS structures are designed for frequencies around 0.8 THz. A fabrication process is proposed where a 100-μm-thick glass substrate is formed through the HF etching of a standard 500-μm-thick low cost glass wafer. Using this fabrication process, three separate robust designs consisting of single-layer FSS are investigated using high-frequency structural simulator (HFSS). Based on the simulation results, the first design consists of a circular ring slot in a square metallic structure on top of a 100-μm-thick Pyrex glass substrate with 70% transmission bandwidth of approximately 0.07 THz, which remains nearly constant till 30° angle of incidence. The second design consists of a tripole structure on top of a 100-μm-thick Pyrex glass substrate with 65% transmission bandwidth of 0.035 THz, which remains nearly constant till 30° angle of incidence. The third structure consists of a triangular ring slot in a square metal on top of a 100-μm-thick Pyrex glass substrate with 70% transmission bandwidth of 0.051 THz, which remains nearly constant up to 20° angle of incidence. These designs show that the reflections from samples can be reduced compared to the conventional sample holders used in THz spectroscopy applications, by using single layer FSS structures manufactured through a relatively simple fabrication process. Practically, these structures are achieved on a fabricated 285-μm-thick glass substrate. Taking into account the losses and discrepancies in the substrate thickness, the measured results are in good agreement with the electromagnetic simulations.

Wireless Josephson amplifier

Josephson junction parametric amplifiers are playing a crucial role in the readout chain in superconducting quantum information experiments. However, their integration with current 3D cavity implementations poses the problem of transitioning between waveguide, coax cables, and planar circuits. Moreover, Josephson amplifiers require auxiliary microwave components, like directional couplers and/or hybrids, that are sources of spurious losses and impedance mismatches that limit measurement efficiency and amplifier tunability. We have developed a wireless architecture for these parametric amplifiers that eliminates superfluous microwave components and interconnects. This greatly simplifies their assembly and integration into experiments. We present an experimental realization of such a device operating in the 9–11 GHz band with about 100 MHz of amplitude gain-bandwidth product, on par with devices mounted in conventional sample holders. The simpler impedance environment presented to the amplifier also results in increased amplifier tunability.

Desenvolvimento e avaliação de um porta-amostra de baixo custo para caracterização elétrica de materiais cerâmicos

Conventional sample holder cells used to the electric characterization of ceramics at high temperature consists of an alumina tube and platinum wires and plates using a complex design. The high cost materials used in the conventional sampler holder cell were replaced by stainless steel and conventional ceramics. The sample holder was validated by characterizing yttria-stabilized-zirconia in a temperature range of 25 to 700 oC. The results do not present variations, discontinuity or unusual noise in the electric signals. Several samples were characterized without maintenance, which demonstrates that the sample holder is electric and mechanic adequate to be used to electrical characterization of ceramics up to 700 oC.

Measuring sorption coefficients and BET surface areas on intact drillcore and crushed granite samples

Abstract In general sorption coefficients, K d, cat ion exchange capacity, CEC, and BET surface areas are measured on crushed rock samples because it is very time consuming to measure K d and CEC on larger rock pieces as it takes a long time for the sorbing species to penetrate into and equilibrate a large sample. Also conventional sample holders for BET measurements are too small to hold a large sample. We have manufactured large sample holders for BET measurements and modified the equipment so that it is possible to measure BET surface areas on samples with 50 mm diameter and up to 100 mm length. Results are presented for intact pieces and compared to results on crushed material from the same drillcore. For K d and CEC measurements we have developed a technique and equipment by which ions can be made to rapidly intrude into and equilibrate the internal surfaces of the same size samples as mentioned above. The method is based on electro-migration where the sample is placed between two vessels one with an anode and other with a cathode. The electric potential gradient drives the ions into and through the sample very much faster than molecular diffusion does. With Cs as the sorbing ion a few weeks were sufficient to equilibrate the 50 mm long sample. In previous diffusion experiments it took more than a year to equilibrate a 15 mm thick sample. A special mixing technique eliminates the development of low and high pH in the electrode compartments. K d results from measurements on an intact drillcore are presented and comparison is made with results obtained on crushed material from the same bore core. The results from the sorption experiments are compared with the results from the BET surface area determinations in an attempt to evaluate the use of the BET surface area as a proxy for sorption behaviour.

Development of a modified test cell for AC impedance testing of coated Al fins

An innovative test-cell arrangement is proposed and examined for electrochemical impedance spectroscopy (EIS) testing of coated thin sheet or foil samples. This arrangement uses a thin layer of medical cotton fabric as a medium containing and transporting 5% sodium chloride solution. This new EIS cell avoids the intervention of edge effect into EIS measurements of painted material. It also avoids the formation of crevice attack experienced at the edges of conventional sample holders or normally under the edge of the masking material. This arrangement is simple and flexible to suit different sizes and shapes of flat panel and foil samples. It can also be used effectively as specimen holders for other than thin sheets. The test cell is also suitable for any electrochemical tests other than impedance measurements. The accelerated results of the EIS present the viability of the EIS test cell to be used as an accelerated nondestructive, repetitive measurement of coated thin metal substrate.

An Optimized Freeze-Fracture Replication Procedure for Human Skin

This in vitro study aimed at substantial modification of the freeze-fracture replication technique (FFRT) which should result in an optimal visualization of the ultrastructure of human skin. The technique was modified in two ways: firstly, the conventional sample holders such as gold cups and copper plates were replaced by silver cylinders (83.5% silver, 16.5% copper) resulting in almost perpendicular cross fractures through the skin. Secondly, the replica cleaning procedure was optimized through the following sequence of treatments. Firstly, a mild tissue destruction was obtained by simultaneous lipid solvation and water extraction with absolute methanol (20 h), followed by protein denaturation with dimethyl sulfoxide (DMSO, 24 h). Subsequently, a final treatment was given using an alkaline sodium hypochlorite solution (20% KOH/13% NaClO; 1:3 v/v, 4 d). After rinsing the replicas for 45 min in aqua bidest, they were mounted on copper grids and examined in the transmission electron microscope (TEM). The combination of the unorthodox fracturing method and the optimized cleaning procedure yielded large, practically undamaged and very clean replicas of near perpendicular cross fractures through human skin. Common handicaps related to current freeze-fracture procedures when applied to skin, such as incomplete cleaning and fragmentation of replicas and oblique or irregular fracturing planes, can largely be avoided in this way. In this paper a complete description of the method is given, and a number of advantages are illustrated with the aid of TEM micrographs.

螢光X線分析における試料重量について

X-ray fluorescence analysis requires comparatively large amounts of samples when conventional sample holders are used. However, in the laboratory, rapid and completely non-destructive quantitative analysis by using the X-ray fluorescence technique permits the use of small samples and results are as accurate and precise as those obtained when using the large amounts of samples.For testing the use of small samples in the laboratory, samples were prepared by brequetting pure magnesium borate, cadmium sulfide and barium oxide. Two methods of exposing the surface areas to primary X-ray beams were then used. In the first method, the minimum amounts required for analysis of the pure chemical briquettes were 0.3g for magnesium borate, 1g for cadmium sulfide and 0.5g for barium oxide by exposing the entire surface to primary X-ray beams. It was found that a minimum sample of 1 g was needed, if the three chemicals were mixed with varying amounts of each in any one sample. Minimum weight of samples was inversely related to the total mass-absorption coefficient, rather than to the density or the thickness of the samples. The lower the total mass-absorption coefficient, the greater the amout of samples required.In the second method, when various portions of the center surface area were masked before exposure to primary X-ray beams, it was found that the decreases in the fluorescent intensity ratio were less than 10% if the exposed area was greater than 60% of the standard surface area (11.3cm2).