Gasket Material Research Articles

FLiNaK compatibility studies with Inconel 600 and silicon carbide

A small liquid fluoride salt test apparatus has been constructed and testing has been conducted to examine the compatibility of silicon carbide (SiC), Inconel 600 and a spiral wound gasket material in FLiNaK, the ternary eutectic alkaline metal fluoride salt mixture. These tests were conducted to evaluate materials and sealing systems that could be used in fluoride salt systems. Three months of testing at 700°C was conducted to assure that these materials and seals would be acceptable when operating under prototypic operating conditions. The SiC specimens showed little or no change over the test period, while the spiral wound gasket material did not show any degradation except that salt might have been seeping into the outermost spirals of the gasket. The Inconel 600 specimens showed regions of voiding which penetrated the specimen surface to about 250μm in depth. Analysis indicated that the salt had leached chrome from the Inconel surface, as was expected for this material.

Excellent electromagnetic interference shielding effectiveness of chemically reduced graphitic oxide paper at 101 GHz*

Graphitic oxide (GO) was synthesized by oxidation of graphite powder using Hummer’s method and the formed GO is solution processed into paper-like macroscopic form. Subsequently, chemically reduced graphitic oxide paper (CRGOP) is prepared by hydrazine vapours induced reduction of formed GO precursor based paper. The formation of GO and its successful reduction to RGO phase is confirmed by FTIR, Raman Spectroscopy and X-ray diffraction. It has been observed that due to high electrical conductivity ~200 micron thick CRGOP display excellent EMI shielding performance at very high frequency of 101 GHz frequency with total shielding effectiveness (SE) value of −35.49 dB (i.e. >99.97% blocking of incident EM radiation) which is much higher compared to pristine GO paper (−1.55 dB) or comparable to expanded graphite (EG) sheet (−35.61 dB). Due to their lightweight nature, these freestanding CRGOPs display average specific SE value of −221.8 dB cm3/g. Besides, their excellent flexibility and makes them potential candidate for lightweight EMI gasketing material compared to other forms of flexible carbons like EG.

Crevice Corrosion Study of Materials for Propulsion Applications in the Marine Environment

The present work addresses crevice and galvanic corrosion processes occurring at the cylinder head gasket/cylinder head interface and cylinder head gasket/cylinder liner interface of four-stroke medium-speed diesel engines for marine applications. The contact between these systems and the marine environment can promote formation of demanding corrosion conditions, therefore influencing the lifetime of the engine components. The electrochemical behavior of various metals and alloys used as head gasket materials (both ferrous alloys and copper alloys) was investigated. The efficacy of corrosion inhibitors was determined by comparing electrochemical behavior with and without inhibitors. In particular, crevice corrosion has been investigated by electrochemical tests using an experimental set-up developed starting from the requirements of the ASTM G-192-08, with adaptation of the test to the conditions peculiar to this application. In addition to the crevice corrosion resistance, the possible problems of galvanic coupling, as well as corrosive reactivity, were evaluated using electrochemical tests, such as potentiodynamic measurements. It was possible to quantify, in several cases, the corrosion resistance of the various coupled materials, and in particular the resistance to crevice corrosion, providing a basis for the selection of materials for this specific application.

Compatibility of transformer construction materials with natural ester-based insulating fluids

The main objective of this study was to evaluate the effect of transformer construction materials, such as kraft insulation paper, varnish, core steel and gasket materials (rubber), on the physicochemical properties of natural ester-based insulating oils (NEIs) and mineral insulating oil (MIO) under heating. We evaluated two NEIs, one formulated with soya oil (Envirotemp FR3) and other with corn oil (Biovolt A). The test specimens were placed in a 1-L jar with 800 mL of insulating oil and then the jar was placed in an oven at 100 °C for 716 h. The insulating fluids were analyzed before and after the heating tests by physicochemical analyses, such as kinematic viscosity, acid number (or neutralization number), dissipation factor and interfacial tension for MIO. Properties of the aged reference and the test specimen oils for a standard testing method for compatibility of construction materials with NEIs are proposed. The only parameter that showed variation after the NEI compatibility testing with different materials was the dissipation factor at 90 °C. The results show that besides compatibility and aging tests, mechanical tests for the gasket or seal materials should also be performed to conclude whether a material is suitable for construction of transformers insulated with NEIs.

EX SITU DEGRADATION OF SILICONE RUBBERS WITH DIFFERENT HARDNESS IN A CATHODE OUTLET SOLUTION OF PEMFC

ABSTRACT Polymer electrolyte membrane fuel cells (PEMFCs) require gaskets and seals in each cell to keep the reactant gas and liquid within their respective regions. The durability of sealing materials is crucial to the operating life as well as the electrochemical performance of fuel cell stacks. In this study, the aging process of silicone rubbers, often used as gasket materials for fuel cells, with hardnesses of 30, 40, and 50 (Shore A) in a solution collected from the cathode of PEMFC is investigated. Fourier transform infrared spectroscopy and an inductively coupled plasma atomic emission spectrometer are used to study the chemical composition of the samples before and after exposure to the test environment over time. It is suggested that the degradation of silicone rubbers is attributed to the chemical decomposition of silicon-based backbone and the leaching of fillers. Although the silicone rubber with higher hardness loses more weight due to its larger amount of fillers, it seems more stable and durable in mechanical properties and surface morphology.

Pressure-dependent structure of the null-scattering alloy Ti0.676 Zr0.324

The room temperature structure of the alloy was measured by X-ray diffraction under compression at pressures up to . This alloy is used as a construction material in high pressure neutron-scattering research and has a mean coherent neutron scattering length of zero, that is, it is a so-called null-scattering alloy. A broad phase transition was observed from a hexagonal close-packed α-phase to a hexagonal ω-phase, which started at a pressure of and was completed by . The data for the α-phase were fitted by using a third-order Birch–Murnaghan equation of state, giving an isothermal bulk modulus and pressure derivative . The results will help to ensure that accurate structural information can be gained from in situ high pressure neutron diffraction work on amorphous and liquid materials where the alloy is used as a gasket material.

Effects of bolt torque and contact resistance on the performance of the polymer electrolyte membrane electrolyzers

The effect of bolt torque and contact resistance on the performance of Proton Exchange Membrane (PEM) Electrolyzers are investigated by a 50 cm2 cell. The cell is designed and manufactured in house. The performance and contact resistance of the cell with three different gasket materials for demanding bolt torques are measured. The pressure distribution inside the cell is obtained by using pressure sensitive films. The pressure acting on the membrane electrode assembly (MEA) is calculated by analyzing and quantifying intensities of pressure film images. 3D plots of pressure distribution for predefined bolt torque values are obtained to understand the pressure distribution over the active area. The performance of the cell is enhanced when bolt torque is increased. However, beyond a value, relatively weak cell components such as diffusion layers are damaged and performance loss is observed due to the mass transfer limitations. The best efficiency is reached at 15Nm bolt torque for Polytetrafluoroethylene (PTFE) and Ethylene Propylene Diene Monomer (EPDM) gaskets. For silicon gasket best efficiency is reached at 15Nm at lower current densities and at 10Nm at higher current densities. Increasing clamping pressure is found to be developing more contact points between the interfaces and results in decrease in contact resistance inside the cell.

In-situ characterization of oxalic acid breakdown at elevated P and T: Implications for organic C-O-H fluid sources in petrologic experiments

Decomposition of oxalic acid in the presence of water was examined in a hydrothermal diamondanvil cell up to 800 °C and 970-1480 MPa as a function of oxygen fugacity to assess its usefulness as a C-O-H fluid source in petrologic experiments. Fluid, vapor, and solid species were identified in situ at elevated temperature and pressure with Raman spectroscopy and optical microscopy. Under oxidizing conditions (buffered by the reaction NiO ↔ Ni+½O2), oxalic acid decomposes to carbon dioxide and water. Under reducing conditions (buffered by the reaction Mo+O2 ↔ MoO2), oxalic acid decomposes to methane and hydrogen. Under unbuffered conditions, at intermediate oxygen fugacity (~0 to 1 log units below the fayalite-quartz-magnetite buffer), oxalic acid disproportionates to graphite and minor methane and carbon dioxide. The results from the Ni-NiO-buffered and Mo-MoO2-buffered experiments result in observed fluid species that are similar to those predicted by previous investigations. However, there are substantial differences between our results and previous studies of oxalic acid decomposition in the unbuffered experiment that was within a log unit of the fayalite-magnetite-quartz (FMQ) buffer. These include the detection of aqueous C-H species at temperatures as low as 400 °C and a solid graphite-like phase at 800 °C. These differences can be explained if we consider that aqueous H2 in our experiment reacted to form the C-H species, instead of being lost via diffusion through the H2-permeable capsules used in previous studies. Consequently, for experiments within about 1 log unit of the FMQ buffer curve, oxalic acid is likely a poor choice for a C-O-H fluid source because the formation of graphitic carbon would result in significant deviations from the expected C-O-H fluid composition and concentration (i.e., CO2+H2O). At oxygen fugacities outside a log unit of FMQ, the observed fluid species are similar to those predicted by previous investigations and the use of oxalic acid as a C-O-H fluid source is permissible from the perspective of oxygen fugacity, although other system parameters (e.g., sample geometries, capsule thickness, capsule materials, gasket materials, wall thickness) must still be considered.

NDMA formation from gaskets used in water storage tanks

Elevated concentrations of N‐nitrosodimethylamine (NDMA) were detected in a distribution system during routine monitoring. The high concentrations were localized, and a temporary storage tank was suspected to be the source of the problem. Samples of the gaskets used in the construction of the temporary tank were gathered and subjected to bench‐scale tests. These tests demonstrated that the gaskets, when exposed to system water, did produce NDMA as well as other nitrosamines. Chloramine did not contribute to NDMA or N‐nitrosodi‐n‐butylamine (NDBA) leaching from gasket material.

Integrated-fin gasket for palm cubic-anvil high pressure apparatus.

We described an integrated-fin gasket technique for the palm cubic-anvil apparatus specialized for the high-pressure and low-temperature measurements. By using such a gasket made from the semi-sintered MgO ceramics and the tungsten-carbide anvils of 2.5 mm square top, we successfully generate pressures over 16 GPa at both room and cryogenic temperatures down to 0.5 K. We observed a pressure self-increment for this specific configuration and further characterized the thermally induced pressure variation by monitoring the antiferromagnetic transition temperature of chromium up to 12 GPa. In addition to enlarge the pressure capacity, such a modified gasket also improves greatly the surviving rate of electrical leads hanging the sample inside a Teflon capsule filled with the liquid pressure-transmitting medium. These improvements should be attributed to the reduced extrusion of gasket materials during the initial compression.

Two and Three Electrode Electrochemical Cells for Ambient and High Temperature Battery Materials Research

Introduction Coin cells and Swagelok cells are typically used for two and three electrode electrochemical testing of metal ion battery materials. Commercial three electrode laboratory cells are also available, but are typically expensive and often use elastomeric seals, which react with electrolyte and are not compatible with high temperatures. The use of traditional 2325 coin cell hardware at high temperature applications is limited by the 60°C softening temperature of the cell gasket. At 60°C, the pressure generated by highly volatile solvents can cause the cell to rupture. This is especially troublesome for Mg battery research where volatile solvents are generally used and high temperatures are needed for better intercalation kinetics. Two and three electrode Swagelok cells are more difficult to prepare than standard coin cells. They typically use PTFE ferrules, and care must be taken as PTFE is reactive with electrolyte at low potentials. Here we describe cell hardware based on Conflat vacuum fittings. Typically Conflat vacuum fittings use copper or Viton gaskets. These can either cause a short circuit between two Conflat fittings or react with electrolyte. We have found gasket materials made from stable polymers form effective insulating, electrolyte resistant and high temperature seals in laboratory test cells. Experimental Conflat cells were constructed using standard 2.125" Conflat blank and bored flanges. HDPE or PTFE gaskets were punched from 0.125" sheets using a circular die press. Two electrode cells used the same inner cell stack as a two electrode coin cell (spring, spacer, electrodes, separator). Three electrode cells included a Li or Mg ring reference electrode. 2325 coin cell hardware was used for comparative testing. Results and Discussion Figure 1 shows the cycling performance of a LiFePO4 (LFP) vs Li two electrode Conflat cell using 1M LiTFSI in PC at 30oC. It shows no capacity fade and identical performance as coin cells.Figure 2 shows the cycling of a two electrode Li4Ti5O12 (LTO)/Li Conflat cell tested at high temperatures. No capacity fade was detected below 110oC. As the temperature is increased, reactions with the electrolyte caused the capacity to fade due to increased impedance from electrolyte decomposition reactions.Figure 3 shows the cycling performance of a Mo6S8/Mg/Mg three electrode Conflat cell containing a highly volatile tetrahydrofuran (THF) based electrolyte at 60°C. We have found that three electrode cells using such volatile electrolytes at this temperature are extremely unreliable and difficult to make using coin cell hardware. The conflat cell, on the other hand cycled reversibly, during which time the voltages of the Mg counter and Mo6S8working electrode were accurately measured without electrolyte polarization using the third electrode.Conflat cells are excellent low cost cell hardware that use readily available parts. They are simple to assemble can be made into two and three electrode cell configurations and particularly useful for high temperature studies. We consider Conflat cells an excellent alternative to coin and Swagelok cell hardware especially in Mg battery research where the electrolyte is volatile and moderately high temperatures are used. Three electrode measurements at high temperature of Li and Mg battery materials and further details regarding Conflat cell design will be discussed.

Non-Asbestos Gasket Materials for Formula Design

Introduce the component of non-asbestos gasket material, and the raw materials which selected after a comparative study. Reasonable arrange the experiment through the design of orthogonal experiment method, reduce test times, shorten the cycle, avoid the blindness of when the experiment under the premise of the ideal results are obtained, and eventually won the basic formula composition of non-asbestos gasket materials.

Characteristic parameters’ optimization based on contact pressure of sealing gasket for segmental joints

The aim of this study is to optimize the characteristic parameters of the segmental joints based on the contact pressure of sealing gasket. The design status of shield tunnel segment joint sealing gasket material, cross-section type, and holes arrangement through statistical data are first analyzed using the numerical simulation method. The result of this study indicates that the linear regression analysis of the outer contour parameters of the gasket was carried out using the bottom edge length of the gasket as the control variable in accordance with the statistical samples, and the influence of geometric parameters on the waterproofing design of sealing gasket is analyzed by numerical simulation from the aspects of the number of closed holes, the shape of closed holes, and the change of the opening rate in different parts. Characteristic parameters optimization of rubber hardness parameters on waterproof design of sealing gaskets have been completed on the contact pressure of sealing gasket for segmental joints. It provided some references for the design, production, processing, and quality inspection of shield tunnel gasket in the future.

Airborne asbestos exposures associated with gasket and packing replacement: A simulation study and meta-analysis

Exposures to airborne asbestos during the removal and installation of internal gaskets and packing associated with a valve overhaul were characterized and compared to published data according to different variables (e.g., product, equipment, task, tool, setting, duration). Personal breathing zone and area samples were collected during twelve events simulating gasket and packing replacement, clean-up and clothing handling. These samples were analyzed using PCM and TEM methods and PCM-equivalent (PCME) airborne asbestos concentrations were calculated. A meta-analysis was performed to compare these data with airborne asbestos concentrations measured in other studies involving gaskets and packing. Short-term mechanic and assistant airborne asbestos concentrations during valve work averaged 0.013f/cc and 0.008f/cc (PCME), respectively. Area samples averaged 0.008f/cc, 0.005f/cc, and 0.003f/cc (PCME) for center, bystander, and remote background, respectively. Assuming a tradesman conservatively performs 1–3 gasket and/or packing replacements daily, an average 8-h TWA was estimated to be 0.002–0.010f/cc (PCME). Combining these results in a meta-analysis of the published exposure data showed that the majority of airborne asbestos exposures during work with gaskets and packing fall within a consistent and low range. Significant differences in airborne concentrations were observed between power versus manual tools and removal versus installation tasks. Airborne asbestos concentrations resulting from gasket and packing work during a valve overhaul are consistent with historical exposure data on replacement of asbestos-containing gasket and packing materials involving multiple variables and, in nearly all plausible scenarios, result in average airborne asbestos concentrations below contemporaneous occupational exposure limits for asbestos.

A green procedure using ozone for Cleaning-in-Place in the beverage industry

Cleaning-in-Place (CIP) in the beverage industry is typically carried out in production lines with alkaline and acidic solutions with detergents. This cleaning not only produces alkaline and acidic wastewater with detergents but also takes significant time. One of the important targets for CIP is adsorbed odorous compounds on gaskets, hence, we have tried to establish a rapid and green CIP process to remove traces of such compounds, especially d-limonene, an odorous component of orange juice, using two approaches; an ozone cleaning method and a change of gasket material from ethylene propylene diene monomer (EPDM) rubber to silicone rubber. By changing the gasket material from EPDM rubber to silicone rubber, the removability of d-limonene by typical alkaline and acidic cleanings with detergents was improved. However, complete removal of 4mgg−1 of d-limonene on both EPDM and silicone gaskets could not be achieved even using a series of conventional cleaning procedures that included alkaline and acidic cleaning for 220min. Ozone treatment dramatically improved the removability of d-limonene, removing 87% from the EPDM gasket at 60min and 100% from the silicone gasket at 30min. The combination of the silicone gasket and ozone treatment resulted in the most effective cleaning. The main removal mechanism for ozone treatment was confirmed to be oxidation by molecular ozone. Effectiveness of changing the gasket material from EPDM rubber to silicone rubber in reducing residual amounts of odorous compounds adsorbed on the gaskets was also confirmed for furfural and 4-vinylguaiacol.

G0310202 押込み試験による予ひずみを考慮したガスケットの長期・高温粘弾性特性評価(材料力学部門一般セッション:変形・ひずみ(2))

Gasket stresses in flanged joints decrease due to creep deformation of gaskets. Prediction of long-term viscoelastic properties of a gasket is important to ensure the tightness of flange joint for a long-term use, especially in elevated temperature applications. Nanoindentation creep test was carried out using TMA with Berkovich indenter to evaluate the viscoelastic characteristics of a PTFE based sheet gasket. The time-temperature superposition principle using W.L.F equation was applied to obtain the master curve of the creep compliance of gasket material at elevated temperature. The elastic-viscoelastic correspondence principle waz also applied to estimate the gasket creep strain in the flanges from the master curve of the creep compliance. It was able to obtain equally prediction equation with results of HPIS Z 105 test by taking into account the pre-strain. In order to obtain a creep strain predictive expression, it is necessary to consider the prestrain. Creep strain predictive expression is useful for estimating the long-term creep modification in a flange with a high temperature.

Valence Crossover of Ce Ions in CeCu2Si2 under High Pressure –Pressure Dependence of the Unit Cell Volume and the NQR Frequency–

The pressure dependence of the valence of Ce ions in CeCu2Si2 has been investigated by means of X-ray powder diffraction (XRPD) and nuclear quadrupole resonance (NQR) measurements. The high-pressure XRPD measurements were carried out at 12 K for CeCu2Si2 and CeCu2Ge2. Precise measurements under smoothly-applied pressure were achieved through the selection of the gasket material of a diamond anvil cell. The jump of the unit cell volume, which was reported previously in CeCu2Ge2, was not observed within the experimental accuracy, indicating the absence of a first-order valance transition. The pressure dependence of 63Cu-NQR frequency νQ measured in CeCu2Si2 was compared with that calculated from the measured lattice parameters. The νQ's were calculated for the two cases of LaCu2Si2 and CeCu2Si2, corresponding to localized and itinerant cases for \(4f\) electrons, respectively. The measured and calculated slopes dνQ/dP show good agreement. A small but significant deviation from the pressure-linear dependence in νQ was observed in the narrow pressure range of 3.9–4.5 GPa, indicating a valence crossover adjacent to the critical end point.

Deformation Characteristic of Thin Stainless Gasket Material

Previous studies on corrugated metal gaskets have established that the contact width, contact stress, and surface roughness are important design parameters for optimizing gasket performance. However, the metal gaskets studied previously required a high axial force for the tightening process; in addition that metal gaskets tend to corrode easily. In this study, we examined the deformation mode of a thin stainless gasket using a finite element method (FEM) analysis. A final evaluation was made using a compression examination. The analysis based on the dimension of flat and convex portion. The load, deformation mode, and contact stress were obtained through a simulation. Based on the deformation of the flat and convex portions, the deformation modes were divided into three types. The deformation mode of the thin stainless gasket material has a higher probability of deformation in mode I when the aspect ratio of the length of the flat portion to the length of the convex portion, L/D, increases.

Hingeless negative linear compression in the mechanochromic gold complex [(C6F5Au)2(μ-1,4-diisocyanobenzene)

The compression of a crystalline material under hydrostatic pressure always results in a reduction in volume of the solid, with the observed reduction typically occurring in all crystallographic cell parameters.1 However, there are a number of exceptional materials that have been shown to expand in a specific direction upon hydrostatic compression while maintaining a positive volume compression. The phenomenon of uni-or biaxial expansion under compression is known as negative linear compressibility (NLC).1 Rare examples of NLC have attracted attention recently owing to the potential applications in a range of materials, including body armor, artificial muscle actuators, and pressure sensors.2

Thermal stress development of liquid silicone rubber seal under temperature cycling

Liquid Silicone Rubber (LSR) is commonly used as gasket or seal material in many industrial applications. The temperature dependent material property of polymeric rubbers will result in stress relaxation/creep. The development of compressive stress in LSR between two clamping metal plates under temperature cycling is discussed in this paper. It is found that (a) in addition to stress relaxation, thermal expansion or contraction of the material contributes the most in the observed stress variation during temperature change, and (b) the stiffness of LSR appears to change according to temperature history.