Materials In Harsh Environments Research Articles

Visualizing time-dependent microstructural and chemical evolution during molten salt corrosion of Ni-20Cr model alloy using correlative quasi in situ TEM and in situ synchrotron X-ray nano-tomography

In situ monitoring of corrosion processes is important to fundamentally understand the kinetics and evolution of materials in harsh environments. A quasi in situ transmission electron microscopy technique was utilized to study microstructural and chemical evolution of a Ni-20Cr disc sample exposed to molten KCl-MgCl2 salt for 60 s in consecutive 20 s iterations. In situ synchrotron X-ray nano-tomography was performed to characterize the morphological evolution of a Ni-20Cr microwire exposed to molten KCl-MgCl2. Both techniques captured key corrosion events and revealed mechanisms at different time and length scales, potentially bringing greater insights and deeper understanding beyond conventional analysis.

Ultralight and heat-insulating mesoporous polyimide aerogels cross-linked with aminated SiO2 nanoparticles

Ideally, excellent heat-insulating material should have low thermal conductivity, low density, excellent resistance to high and low temperatures and good mechanical properties. But few materials can meet all the above requirements at the same time. Take polyimide (PI) aerogel as an example. Although it has the advantages of lightweight, good mechanical properties and excellent temperature resistance, the value of its thermal conductivity is often unsatisfactory. To solve this problem, a series of mesoporous polyimide aerogels using aminated SiO2 nanoparticles as cross-linker have been prepared. By changing the content of SiO2 and the synthetic methods, the key properties of PI aerogels such as the density and thermal conductivity were effectively tuned. These aerogels have low density, high specific modulus, significantly low thermal conductivity (~20 mW m−1 K−1), and excellent high temperature resistance. Their general properties (shrinkage, density, compression performances, specific surface area, pore size distribution, high temperature resistance) and their application potential as lightweight, high-performance thermal insulation materials in harsh environments are discussed.

Lightweight and Hydrophobic Three-Dimensional Wood-Derived Anisotropic Magnetic Porous Carbon for Highly Efficient Electromagnetic Interference Shielding.

Constructing multifunctional characteristics toward advanced electromagnetic interference shielding materials in harsh environments has become a development trend. Herein, the wood-derived magnetic porous carbon composites with a highly ordered anisotropic porous architecture were successfully fabricated through a pyrolysis procedure. The three-dimensional porous skeleton inherited from the wood stock serves as an electrically conductive network and incorporates magnetic Ni nanoparticles homogeneously and firmly embedded within the carbon matrix that can further improve the electromagnetic attenuation capacity. The optimized Ni/porous carbon (PC) composite exhibits an exceptional electromagnetic interference (EMI) shielding effectiveness of 50.8 dB at the whole X band (8.2-12.4 GHz) with a low thickness (2 mm) and an ultralow density (0.288 g/cm3) and simultaneously possesses an extraordinary compressive strength (11.7 MPa) and a hydrophobic water contact angle (152.1°). Our study provides an alternative strategy to utilize green wood-based materials to design multifunctional EMI shielding composites.

Dual In-Situ Water Diffusion Monitoring of GFRPs based on Optical Fibres and CNTs

Glass Fibre Reinforced Polymer (GRFP) composites are increasingly being used as new materials for civil and petrochemical engineering infrastructures, owing to the combination of relatively high specific strength and stiffness and cost-competitiveness over traditional materials. However, practical concerns remain on the environmental stability of these materials in harsh environments. For instance, diffusion of salty water through the composites can trigger degradation and ageing. For this reason, a continuous monitoring of the integrity of GFRP composites is required. GRFPs health monitoring solutions, being non-destructive, in-situ, real-time, highly reliable and remotely controllable, are as desirable as challenging. Herein we develop and compare two methods for real-time monitoring of GRFP: one based on the electrical sensing signals of percolated carbon nanotubes (CNTs) networks and the other on optical fibre sensors (OFSs). As a proof-of-concept of dual sensory system, both sensors were used in combination to detect the diffusion of water through the composite. Measurements demonstrated that both CNTs and OFSs were able to detect water diffusion through the epoxy matrix successfully, with an on-off sensing behaviour. OFSs exhibit some advantages since they do not require electrical supply as required in hazardous environments and are more suitable for remote operation, which make them attractive for new developments in harsh-environment sensing. On the other hand, CNTs can be easily embedded in the composite without compromising its performance (e.g., mechanical properties) and are easily interrogated by measurement of electrical conductance, therefore could be used as spot sensors in the most failure-prone sections of GFRP components. This study opens up the possibility for an early detection of composites degradation, which could prevent failures in GFRP structures such as pipelines and storage tanks used in the oil and gas industry.

Application of Raman spectroscopy and X-ray diffraction to study the erosion-corrosion of UNS S32205 in mine water

Corrosion products play a prominent role in reducing the degradation rate of materials in harsh environments. In this work, the erosion-corrosion behaviour of duplex stainless steel (UNS S32205) in mine water, was characterised using X-ray diffraction and Raman spectrometry. The tests include erosion-corrosion in mine water and erosion in cathodically protected distilled water. X-ray diffraction and Raman spectroscopy were employed to confirm the presence of hydrolysed iron sulphate, chromium oxide, and hydrated iron oxides. The corrosion products were able to explain the effects of pH and flow velocity on the duplex stainless steel performance in the mine water environment.

Mie resonator method for reliable permittivity measurement of loss-less ceramics in microwave frequency at high temperature

This paper describes a new approach, based on the Mie theory, to measure the dielectric properties of lossless materials at temperatures greater than 1500 °C. For the reliable operation of microwave transmitting materials in harsh environments, it is crucial to correctly characterize the permittivity under various temperature conditions. Heating and measurement systems using a propane torch and a single horn antenna were designed to estimate such dielectric properties. The reflection spectrum of Al2O3 ceramics at room temperature was determined using the Mie theory to derive the permittivity and validate the approach. High-temperature dielectric constants are derived from simulated values, which are reliable and have only a slight slope as a function of temperature. These results indicate that the permittivity measurement technique can provide powerful information for the optimal design and accurate evaluation of the dielectric properties of various lossless materials at high temperatures.

Flexible and recoverable SiC nanofiber aerogels for electromagnetic wave absorption

A novel flexible and recoverable SiC nanofiber aerogel (SiCnf aerogel) was synthesized by electrospinning and freeze-drying methods. The SiC fibers prepared by electrospinning technique, have a fine diameter (~600 nm) and excellent flexibility. On this basis, the fibers are stirred at a high-speed and then subjected to freeze-drying and high-temperature treatment to prepare a SiCnf aerogels. The fabricated SiCnf aerogels possess low density (0.039–0.041 g/cm3), excellent thermal insulation (0.025–0.031 W/(m∙K)), and mechanical properties of recoverable strain (~40%). Meanwhile, the SiCnf aerogels show excellent electromagnetic (EM) wave absorption characteristics, which have the effective absorption bandwidth of 9–11.5 GHz (reflection loss (RL) < −10 dB, more than 90% EM wave was absorbed) and minimum RL value attained −21.41 dB at 10.5 GHz with the thickness of 3 mm. The successful preparation of the novel multifunctional material can be used for high temperature insulation materials and electromagnetic wave absorbing materials in harsh environments.

Multi-scale fatigue, fracture and damage of materials in harsh environments at NUI Galway, Ireland

Multi-scale fatigue, fracture and damage of materials in harsh environments at NUI Galway, Ireland

Fabrication of novel hydrophobic SiC/SiO2 bead-string like core-shell nanochains via a facile catalyst/template-free thermal chemical vapor deposition process

Novel SiC/SiO2 bead-string like core-shell nanochains have been fabricated via a thermal chemical vapor deposition process without using any catalysts and templates. These SiC/SiO2 bead-string like core-shell nanochains are made up of SiO2 spheres as beads and SiC/SiO2 core-shell nanowires as strings, respectively. A Vapor–Solid growth mechanism is proposed to explain the formation of these SiC/SiO2 hetero-nanostructures in the absence of catalysts on the basis of the characterization results, the possible reactions among the solid phases, intermediate gas phases and surface energy minimization. Moreover, these SiO2-SiC bead-string like nanochains exhibit good hydrophobicity with a water contact angle over 140°, which is caused by the special surface composition. This hydrophobicity makes these SiO2-SiC bead-string like nanochains promising candidates as surface protective or self-cleaning materials in harsh environments.

High‐Throughput Investigation of the Oxidation and Phase Constitution of Thin‐Film Ni–Al–Cr Materials Libraries

Thin‐film materials libraries of the intermetallic model system Ni–Al–Cr were fabricated and their oxidation behavior was studied by compositional, optical, electrical, and structural high‐throughput characterization methods. The study reveals the compositional regions of the binary and ternary compositions which withstand longest to annealing in air (up to 700 °C), and are, therefore, resistant to oxidation and delamination under these conditions. A complete ternary thin‐film phase diagram for the Ni–Al–Cr system in its state after 9 h annealing in air at 500 °C was determined. Optical high‐throughput characterization is shown to be valid for rapid identification of oxidizing phases. Generally, the initially metallic phases show different oxidation behavior in air. We find that the ternary compositions are more resistant to oxidation than the binary phases. Compositions around Ni25Al12.5Cr62.5 were found to show very good oxidation resistance. These results were supported by additional information from corresponding electrical and optical property investigations. The presented high‐throughput approach is generic for the efficient study of multinary thin‐film materials in harsh environments.

Protective coatings of electronics under harsh thermal shock

Industrial electronics devices commonly encounter harsh environmental conditions during their operational lifetime. To protect the electronics from conditions like humidity and contaminants, protective moulding and coating materials can be used. However, the behaviour of materials in harsh environments and their effect on the reliability of electronics in industrial products has been studied only very little. Moreover, the changes in the parameters of several commonly used materials under various conditions remain largely unknown. In this paper the effect of the protective coating and moulding materials on product level reliability of an electronics device was studied under thermal shock test. In addition, the change in the mechanical properties of the materials under test conditions was studied. The conditions of the test used were relatively harsh with extreme temperatures of −40°C and +125°C. The samples used in the study were commercial electronics devices designed for use in harsh conditions. The protective materials studied included silicone based conformal coating, polyurethane based moulding material, and silicone based moulding material. Moreover, a comparison test with no protective materials was conducted. The results showed that conformal coating and polyurethane based moulding material markedly decreased the times to failures of the devices. On the other hand, silicone based moulding seemed to slightly improve the reliability of the devices.

Element analysis of complex materials by calibration-free laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a promising method for fast and quantitative element analysis of complex materials. We report on LIBS measurements of multi-component oxide materials and the compositional analysis of materials by a calibration-free (CF) method. This CF-LIBS method relies on modeling of the optical emission of laser-induced plasma assuming local thermodynamic equilibrium. Various materials are investigated and the calculated concentration values (CCF) of oxides CaO, Al2O3, MgO, SiO2, FeO, and MnO are in agreement with nominal concentration values (CN) from reference analysis. The relative error in oxide concentration er=|CCF−CN|/CN decreases with increasing concentration. The quantification is limited to major oxides (CN≥1 wt%). Slag samples from industrial steel production are analyzed on site by means of a mobile measurement system. LIBS measurements are performed at different sample temperatures. The results obtained show that CF-LIBS is applicable to fast compositional analysis of complex materials in harsh environments.

Technical Advancements in Submersible-Pump Power Cable for Harsh Environments

Summary In artificial-lift systems, such as electrical submersible pumps, the power cable provides the link between the surface equipment and the pumping unit. New cable designs are constantly being introduced. This paper discusses these designs and their materials. Information on a new approach to cable manufacturing and on use of downhole materials in harsh environments is also provided. This paper includes work on cable designs that incorporate a new, unique, elastomeric composition that resists rupture of jacketing materials used on downhole cables, eliminating the need for tape and braid. Cable history is also reviewed, classifying the cables by use temperatures and relative cost. Criteria for selecting materials suitable for the entire range of downhole environments are included.