Material Characterization Capabilities Research Articles

Tribological performance of carbon nanospheres as lubricant additives: insights from molecular dynamics simulation and experimental analysis

Abstract To investigate the lubrication mechanism of carbon nanospheres and compare their tribological performance with carbon powder, this study presented a comprehensive analysis of their potential as lubricant additives through both experimental testing and molecular dynamics simulations. Carbon nanospheres were synthesized using the hydrothermal method. Extensive comparisons were conducted between carbon powder and carbon nanospheres, focusing on material characterization, dispersion stability, antifriction performance, and antiwear capability. Findings revealed that carbon nanospheres outperformed carbon powder as lubricant additives in PAO 10 owing to their smaller particle size and spherical shape. Specifically, at a concentration of 1wt%, a load of 50 N, a disk speed of 10 rpm, and a temperature of 25 °C, the addition of carbon nanospheres reduced the friction coefficient by 34% and wear volume by 35%. The improved tribological performance was linked to the ability of carbon nanospheres to fill the pits, improving the interface smoothness. Molecular dynamics simulation of carbon nanospheres effectively reflected substrate roughness in the bulk region and further confirmed that this filling effects increased the lubricant's load-bearing capacity, which contributed to the reduction of friction and wear. This study provided significant insights into the development of innovative high-performance lubricant additives for oil-based lubrication in metal friction pairs.

SEEMS: A Single Event Effects and Muon Spectroscopy facility at the Spallation Neutron Source.

This study outlines a concept that would leverage the existing proton accelerator at the Spallation Neutron Source (SNS) of Oak Ridge National Laboratory to enable transformative science via one world-class facility serving two missions: Single Event Effects (SEE) and Muon Spectroscopy (μSR). The μSR portion would deliver the world's highest flux and highest resolution pulsed muon beams for material characterization purposes, with precision and capabilities well beyond comparable facilities. The SEE capabilities deliver neutron, proton, and muon beams for aerospace industries that are facing an impending challenge to certify equipment for safe and reliable behavior under bombardment from atmospheric radiation originating from cosmic and solar rays. With negligible impact on the primary neutron scattering mission of the SNS, the proposed facility will have enormous benefits for both science and industry. We have designated this facility "SEEMS."

The Texas A&M University Hypervelocity Impact Laboratory: A modern aeroballistic range facility.

Novel engineering materials and structures are increasingly designed for use in severe environments involving extreme transient variations in temperature and loading rates, chemically reactive flows, and other conditions. The Texas A&M University Hypervelocity Impact Laboratory (HVIL) enables unique ultrahigh-rate materials characterization, testing, and modeling capabilities by tightly integrating expertise in high-rate materials behavior, computational and polymer chemistry, and multi-physics multiscale numerical algorithm development, validation, and implementation. The HVIL provides a high-throughput test bed for development and tailoring of novel materials and structures to mitigate hypervelocity impacts (HVIs). A conventional, 12.7mm, smooth bore, two-stage light gas gun (2SLGG) is being used as the aeroballistic range launcher to accelerate single and simultaneously launched projectiles to velocities in the range 1.5-7.0 km/s. The aeroballistic range is combined with conventional and innovative experimental, diagnostic, and modeling capabilities to create a unique HVI and hypersonic test bed. Ultrahigh-speed imaging (10M fps), ultrahigh-speed schlieren imaging, multi-angle imaging, digital particle tracking, flash x-ray radiography, nondestructive/destructive inspection, optical and scanning electron microscopy, and other techniques are being used to characterize HVIs and study interactions between hypersonic projectiles and suspended aerosolized particles. Additionally, an overview of 65 2SLGG facilities operational worldwide since 1990 is provided, which is the most comprehensive survey published to date. The HVIL aims to (i) couple recent theoretical developments in shock physics with advances in numerical methods to perform HVI risk assessments of materials and structures, (ii) characterize environmental effects (water, ice, dust, etc.) on hypersonic vehicles, and (iii) address key high-rate materials and hypersonics research problems.

Computed tomography recent history and future perspectives.

.Purpose: We provide a review of the key computed tomography (CT) technologies developed since the late 1980s and offer an overview of one of the future technologies under development. The focus of this review is mainly on the hardware and system development. The topics on the historical event linked to the early days of CT development and other innovations that contributed to the CT development, such as advanced image reconstruction techniques, are covered by companion papers in this special issue.Approach: The review is divided into five major sections, each linked to a key innovation in CT: helical spiral data acquisition, multi-slice CT, wide-cone CT, dual-source CT, and spectral CT. Given the limited scope of this review, only one of the future technologies, photon-counting CT, is discussed in detail. Whenever possible, both theory of operation and clinical examples are provided.Results: Theoretical analyses, phantom results, and clinical examples clearly demonstrate the efficacy and clinical relevancy of five historical technology developments and one future technology in CT. These technologies have improved and will continue to improve CT performance in terms of isotropic volume coverage, improved temporal resolution, and material differentiation and characterization capabilities.Conclusions: Over the past 30 years, technological developments of CT have contributed to the success of CT in many clinical applications such as trauma, oncology, cardiac imaging, and stroke. Advanced clinical applications have and will continue to demand more advanced technology development.

(Invited) Characterization of ALD in Semiconductor Device Fabrication

The CMOS industry continues to push the boundaries of what is possible. Indeed, today’s manufacturing can be described as atomic level engineering, with an example lying in the use of Atomic Layer Deposition (ALD). The development and fabrication (fundamental R&D through to manufacturing) of highly repeatable structures required by the semiconductor industry also necessitates the use of state-of-the-art materials characterization (“if you can’t see it, you can’t develop it”) and process control capabilities (“if you can’t see it, you can’t control it”). This talk will cover the more commonly used materials characterization capabilities used within the industry. This includes, but not limited to: Transmission Electron Microscopy, Atomic Force Microscopy, and X-ray Photoelectron Spectroscopy. Following this, the use of Secondary Ion Mass Spectrometry (SIMS) in the form of Self Focusing SIMS (SF-SIMS), in area selective ALD R&D will be demonstrated.

Broadband terahertz time-domain spectroscopy and fast FMCW imaging: Principle and applications**Project supported by the Royal Society and Natural Science Foundation of China (NSFC) International Exchanges Cost Share (IECnNSFCn181415).

We report a broadband terahertz time-domain spectroscopy (THz-TDS) which enables twenty vibrational modes of adenosine nucleoside to be resolved in a wide frequency range of 1–20 THz. The observed spectroscopic features of adenosine are in good agreement with the published spectra obtained using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. This much extended bandwidth leads to enhanced material characterization capability as it provides spectroscopic information on both intra- and inter-molecular vibrations. In addition, we also report a low-cost frequency modulation continuous wave (FMCW) imaging system which has a fast measurement speed of 40000 waveforms per second. Cross-sectional imaging capability through cardboard has also been demonstrated using its excellent penetration capability at a frequency range of 76–81 GHz. We anticipate that the integration of these two complementary imaging technologies would be highly desirable for many real-world applications because it provides both spectroscopic discrimination and penetration capabilities in a single instrument.

Improved waveform reconstruction and parameter accuracy retrieval for hyperspectral lidar data.

In this paper, we aim to provide a solution for choosing an optimized digitization frequency for full-waveform reconstruction of narrow FWHM laser pulses to improve the performance accuracy required for recognition and characterization of a wide range of materials with distinctive reflectance features. This type of analysis, for the first time, to the best of our knowledge, gives an assessment of the absolute accuracy with which waveform peak intensity and spatiotemporal peak location can be detected using multi- or hyperspectral lidar instrumentation. Different full-waveform reconstruction algorithms with varying characteristics are implemented on simulated Gaussian laser pulse data sets obtained with varying sampling frequencies ranging between 1 GHz and 5 GHz. The data sets are analyzed, and an optimized digitization frequency is found based on observation of algorithmic parameter retrieval accuracy. The accuracy of the full-waveform retrieval in relation to the type of algorithm used and its robustness related to the digitization frequency are also discussed. We find that optimizing the algorithmic processing of multi-wavelength sampled radiance data recorded by multispectral and hyperspectral lidar instruments significantly improves the accuracy of reflectance retrieval and target material characterization capabilities of the instrument.

Embroidered Rectangular Split-Ring Resonators for the Characterization of Dielectric Materials

In this paper, we report an embroidered rectangular split-ring resonator (SRR) operating at S band for material characterization based on the differences in dielectric parameters. We designed, fabricated and characterized SRR sensors on a conventional fabric that can be conformally attached over the surface of samples under investigation. The structures are made of conductive threads and can be embroidered on any dielectric fabric at low cost using conventional embroidery methods. We have demonstrated material characterization capability of the sensors using a specific design with a length of 60 mm and a width of 30 mm. We wrapped the sensors on low-density polyethylene (LDPE) bottles filled with deionized (DI) water and common solvents (ethanol, methanol, isopropanol and acetone) in our experiments. We measured the nominal resonant frequency of a specific sensor wrapped around an empty bottle as 2.07 GHz. The shifts in resonant frequencies when the bottle was filled with the solvents follow the dielectric constants of the solvents.

Update of Dual-Energy CT Applications in the Genitourinary Tract

Dual-energy CT (DECT) is being increasingly used for abdominal imaging because it provides incremental benefit of material characterization without significant increase in radiation dose. This article provides an overview of current DECT techniques and use of DECT in urinary tract imaging for assessment of renal masses and urinary calculi characterization and in CT urography. Incorporation of DECT into clinical practice and use of its material characterization capabilities in urinary tract imaging enable characterization of urinary calculi and incidental renal lesions and can reduce radiation dose by allowing generation of virtual unenhanced images.

A piezomicrobalance system for high‐temperature mass relaxation characterization of metal oxides: A case study of Pr‐doped ceria

AbstractA system for mass relaxation studies based on a gallium phosphate piezocrystal microbalance has been developed, built, and successfully used to characterize a representative mixed ionic and electronic conducting material. The apparatus is constructed to achieve reactor gas exchange times as short as 2 seconds and temporal resolution in mass measurement of 0.1 seconds. These characteristics enabled evaluation of mass relaxations that occurred on the 6 seconds time scale. Proof of concept for materials characterization capabilities of the system was carried out using 10% praseodymium‐doped cerium oxide (PCO), a material that undergoes, at selected temperatures and oxygen partial pressures, changes in mass but not in conductivity. Thin films were deposited on the piezocrystals via pulsed laser deposition (PLD). Mass relaxation curves were collected at 700°C upon application of a small step change in oxygen partial pressure, . Using two different films, the surface reaction constant, kS, was obtained over the range from 10−4 to 0.1 atm. Its value is found to vary between 9.7 × 10−6 and 1.7 × 10−4 cm/s, displaying a power law dependence on , with a law exponent of 0.67 ± 0.02, as averaged over the two sets of results. This steep dependence of kS on is surprisingly independent of a change in dominant defect type within the range of measurement.

Design and development of a new magnetic sensor for stress measurements

This paper describes the design and the development of a new magnetic sensor for stress measurements using the magnetic Barkhausen noise and the magnetic permeability techniques in ferromagnetic steels. Both techniques together, become an important nondestructive technique, due to its exceptional material and stress characterization capabilities. The correlation of the two methods was investigated. Conclusions were derived based on the experimental results.

Angular-resolution and material-characterization measurements for a dual-particle imaging system with mixed-oxide fuel

A dual-particle imaging (DPI) system, capable of simultaneously imaging fast neutrons and gamma rays, has been operated in the presence of mixed-oxide (MOX) fuel to assess the system׳s angular resolution and material-characterization capabilities. The detection principle is based on the scattering physics of neutrons (elastic scattering) and gamma rays (Compton scattering) in organic and inorganic scintillators. The detection system is designed as a combination of a two-plane Compton camera and a neutron-scatter camera. The front plane consists of EJ-309 liquid scintillators and the back plane consists of interleaved EJ-309 and NaI(Tl) scintillators. MCNPX-PoliMi was used to optimize the geometry of the system and the resulting prototype was built and tested using a Cf-252 source as an SNM surrogate. A software package was developed to acquire and process data in real time. The software was used for a measurement campaign to assess the angular resolution of the imaging system with MOX samples. Measurements of two MOX canisters of similar isotopics and intensity were performed for 6 different canister separations (from 5° to 30°, corresponding to distances of 21cm and 131cm, respectively). The measurements yielded a minimum separation of 20° at 2.5m (86-cm separation) required to see 2 separate hot spots. Additionally, the results displayed good agreement with MCNPX-PoliMi simulations. These results indicate an angular resolution between 15° and 20°, given the 5° step. Coupled with its large field of view, and its capability to differentiate between spontaneous fission and (α,n) sources, the DPI system shows its potential for nuclear-nonproliferation applications.

Stress measurement using magnetic Barkhausen noise and metal magnetic memory testing

This paper introduces a comparison of the magnetic Barkhausen noise (BN) and metal magnetic memory (MMM) testing techniques for stress measurement. BN has become an important non-destructive technique due to its exceptional material and stress characterization capabilities. MMM is a recently developed technique with special ability for stress detection and stress history. In the applied tensile experiment, BN and MMM signals were acquired via a BN measurement system and EMS-2003 MMM instrument. Relationships between magnetic signals and applied tensile stresses were derived from experiment results. The difference and correlation of the two methods are investigated. Conclusions were derived based on the experiment results.

The US Department of Energy's Working Group on Photoelectrochemical Hydrogen Production: Promoting Technology-Enabling Breakthroughs in Semiconductor Materials Research

AbstractPhotoelectrochemical (PEC) hydrogen production, using sunlight to split water, is an important enabling technology for a future “Green” economy which will rely, in part, on hydrogen as an energy currency. The traditional semiconductor-based PEC material systems studied to date, however, have been unable to meet all the performance, durability and cost requirements for practical hydrogen production. Technology-enabling breakthroughs are needed in the development of new, advanced materials systems, and toward this end, the U.S. Department of Energy’s Working Group on PEC Hydrogen Production is bringing together experts in analysis, theory, synthesis and characterization from the academic, industry and national-laboratory research sectors. Key Working Group activities, as described in this paper, include performing techno-economic analyses of large-scale PEC production systems and establishing standardized testing and screening protocols for candidate PEC materials systems. In addition, a number of Working Group “Task Forces” are focused on advancing critical PEC materials theory, synthesis and characterization capabilities for application in the research and development of broad-ranging materials systems of promise, including complex metal-oxide and -nitride compounds, amorphous silicon alloys, III-V semiconductors and the copper chalcopyrites. The current status of Working Group activities and progress is summarized.

The LLNL Multi-user Tandem Laboratory PIXE microprobe

We have recently completed the construction of a new ion beamline primarily for particle-induced X-ray emission (PIXE) analysis. This will supplement our current ion microtomography (IMT) material characterization capabilities using accelerator microanalysis. In this paper we describe the PIXE beamline and give some results that characterize the system. We also report the results of some initial experiments.