Composite Gasket Research Articles

Feasibility of winter construction for prefabricated subway station: Waterproof performance analysis of composite cross-section gasket treated by low temperature

The construction of prefabricated subway stations in northeastern China necessitates a focused investigation into the behavior of composite cross-section gaskets with ethylene propylene diene monomer (EPDM) and water swelling rubber (WSR) under low-temperature conditions. This research conducted experimental and numerical studies to analyze the mechanical and waterproof properties of WSR-EPDM gaskets treated at low temperatures. The mechanical properties were evaluated through hardness and compression tests at various treatment temperatures. Additionally, the study examined the impact of treatment temperature and loading rate on the load-deformation relationship. Then, finite element (FE) models were developed and validated based on mechanical experimental results of the gasket-in-groove system under various low-temperature conditions. Subsequently, the nonlinear FE model was used to analyze the effects of joint offset and opening angle on assembly load and waterproof performance. The results demonstrated a direct correlation between the treatment temperature and the Shore hardness and assembly load of the WSR-EPDM gasket. Lower treatment temperatures led to higher hardness and assembly load. Notably, at temperatures below −10 °C, the loading rate had a more pronounced effect on the assembly load. Furthermore, the assembly load initially decreased and then increased with an increase in joint offset, while it consistently decreased with a larger opening angle. Additionally, as the treatment temperature decreased, the average contact pressure during operation also decreased. The influences of joint offset and opening angle were negligible when the treatment temperature was below −20 °C. However, the coupling influence of offset or opening angle and treatment temperature on the waterproofness is evident for a treatment temperature between 0 ∼ −15 °C. In summary, this study serves as a useful reference for evaluating the waterproof properties of these gaskets in low-temperature environments.

Sample heating above 1400 K in a diamond anvil cell

In high-pressure experimental methods, sample heating in the pressure chamber of a diamond anvil cell is an important topic, and numerous efforts have been made to improve and develop new technologies. In this paper, we propose a new type of internal resistance heating technique, the composite heating gasket, prepared by integrating an annular heater into the sample chamber for direct heating of the sample. As the effective heating area covers the entire pressure chamber wall, a relatively quasi-uniform temperature field is formed within the sample chamber. At the same time, the integration design reduces the risk of diamond oxidation and enables direct measurement of the spectroscopic properties of samples at high temperatures. The preparation of the composite heating gasket is simple and repeatable, and its heating performance is stable at temperatures above 1400 K. When the sample diameter is 210 μm and no thermal insulation is used, the diameter of the temperature zone in which the temperature difference is less than 10 and 20 K exceeds 120 and 170 μm, respectively. The composite heating gasket represents a significant advancement in providing a uniform temperature field for in situ measurements with diamond anvil cells at high pressure and temperature.

Pressure-Induced Intermetallic Charge Transfer and Semiconductor-Metal Transition in Two-Dimensional AgRuO 3

Pressure-Induced Intermetallic Charge Transfer and Semiconductor-Metal Transition in Two-Dimensional AgRuO ₃

Structure Optimization and Sealing Performance of Double Corrugated Self-Sealing Composite Gasket

A self-sealing nickel-titanium (NiTi) alloy double corrugated composite gasket was designed. The number of corrugation (5-7), the amplitude of corrugated (0.2-0.4 mm), the thickness of corrugated skeleton (0.5-1.0mm) and the seam width (0.2-0.4 mm) of the composite gasket were selected to design a four-factor and three-level experimental scheme by orthogonal experimental method. The ANSYS finite element software was used to study its compression resilience and sealing performance. The statistica software was used to process the data by multi-factor analysis of variance. The results showed that the corrugated number was the most significant factor affecting the resilience rate, and the slot width was the most significant factor affecting the compression rate. The optimal scheme for the resilience performance was obtained. The sealing performances of self-sealing composite gasket and common corrugated composite gasket were compared. The results showed that self-sealing composite gasket had better sealing performance.

Study on the Reinforcement Mechanism of Graphene Oxide for Non-asbestos Gasket Composites

To improve the quality of the gasket and reduce leakage, non-asbestos gasket composites reinforced by graphene oxide(GO) were prepared. The effect of GO on the microscopic physics and chemistry of slurry suspension and the macroscopic properties of gasket composites were investigated. The microstructure and morphology were analyzed by Fourier-transform infrared (FTIR) spectroscopy and Field emission scanning electron microscopy (FSEM). The results show that the addition of GO improves the microscopic interaction during the wet forming process, which improves the macro properties of the gasket material. The enhancement can be ascribe to the crumpled morphology of GO and the presence of many oxygen-containing functional groups, which enhance the microscopic mechanical interlocking and interfacial interactions of the composite gasket material.

Waterproofing behavior of sealing gaskets for circumferential joints in shield tunnels: A full-scale experimental investigation

This work was performed to investigate the waterproofing and mechanical behavior of sealing gaskets for circumferential joints in Tianjin metro line Z2 tunnel by a full-scale experiment. A newly developed device was introduced in detail, with test procedures, essential treatment methods, and the adopted specimens for gaskets and reinforced concrete segments. Four types of EPDM and composite cross-section gasket profiles were tested under different combinations of joint openings and offsets. The gasket mechanical performance was examined through the load versus deformation relationship, while the water pressure versus joint opening relationship was applied for identifying the gasket sealant performance. The effect of gasket opening area was then discussed, based on a comparison of the test results from two similar gasket profiles. The ratio of waterproof capacity to average contact pressure was proposed to analyze the correlation between the gasket mechanical and sealant behavior. The results showed that both of the joint opening and offset had a great influence on the gasket waterproof behavior, which generally exhibited a reduction with larger joint opening and offset. A relatively small change in gasket opening area may lead to a greater degree of variation in the gasket mechanical and waterproof performance. The leakage failure analysis indicated that bolt holes, circumferential joints and concrete cracks were the common leakage points during the tunneling construction and operation. The full-scale experimental methodology in this paper had the potential in detecting detailed leakage process of gaskets.

Additive manufactured graphene composite Sierpinski gasket tetrahedral antenna for wideband multi-frequency applications

Here we report a pre-fractal antenna design based on the Sierpinski tetrahedron that has been developed with additive manufacturing. The Sierpinski tetrahedron-based antenna was simulated with finite element method (FEM) modeling and experimentally tested to highlight its potential for wideband communications. The Sierpinski tetrahedron-based antennas were fabricated by two methods, the first involves printing the antenna out of acrylonitrile butadiene styrene (ABS), followed by spin casting a coating of an ABS solution containing graphene flakes produced through electrochemical exfoliation, the second method involves 3D printing the antenna from graphene-impregnated polylactic acid (PLA) filament directly without any coating. Both fabrication methods yield a conductive medium to enable receiving EM signals in the low GHz frequency range with measured input return losses higher than 35 dB at resonance. These antennas incorporate the advantages of 3D printing which allows for rapid prototyping and the development of devices with complex geometries. Due to these manufacturing advantages, self-similar antennas like the Sierpinski tetrahedron can be realized which provide increased gain and multi-band performance.

Sealing performance analysis of composite gaskets made of silicone rubber filled with ramie natural fibers

Silicon rubber gaskets are commonly used in many industries for low pressure sealing conditions only. The research studies about the sealing performance improvement of a novel composite gasket made of the silicone rubber filled with ramie natural fibers in a bolted joint connection. In this research the sample of gasket consists of 4 different types of gasket i.e. a pure silicone rubber gasket and the silicone rubber composite gasket with 1, 2 and 3 layers of ramie fiber woven. The gaskets are tested using a water pressure testing equipment with a variation of internal fluid pressure and difference torques at 8 N.m, 12 N.m, 16 N.m and 20 N.m. The sealing performance is measured based on the maximum fluid pressure that can be hold by the gaskets before the fluid leaking occurred. The results show that the silicone rubber composite gaskets have better sealing performance comparing with the pure silicone rubber gaskets where the silicon rubber gaskets capable to hold the internal fluid pressure until around 5 times rather than pure silicon rubber gaskets (0.17 MPa comparing with 0.90 MPa). On the other hand the sealing performance of the composite gasket with 3 layers is almost 2 times better than the composite gasket with 1 layer and around 1.5 times better than the composite gasket with 2 layer of fiber woven.

Electrical Resistance Prediction for Functionalized Multi-Walled Carbon Nanotubes/Epoxy Resin Composite Gasket under Thermal Creep Conditions

Carbon nanotube-based conductive polymer composites (CPC) showed great potentials for self-sensing and in situ structural health monitoring systems. Prediction of the long-term performance for such materials would be a meaningful topic for engineering design. In this work, the changing behavior of the long-term resistance of a multi-walled carbon nanotubes/epoxy resin composite gasket was studied under different temperature and loading conditions. Glass transition strongly influenced the resistance behavior of the composite during the thermal creep process. Similar to classical Kelvin–Voigt creep model, a model considering both the destruction and recovery processes of the conductive network inside the CPC was established. The long-term resistance variation can be predicted based on the model, and the results provided here may serve as a useful guide for further design of smart engineering structural health monitoring systems.

Neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells**Supported by the National Key Research and Development Program of China under Grant No 2016YFA0401503, the Science Challenge Project under Grant No TZ2016001, and the National Natural Science Foundation of China under Grant No 11427810.

Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China’s Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi (I–II 2.55GPa, III–V 7.7GPa) are observed at 100 and 300 kN, respectively, by resistance measurements. The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth. As a result, pressures up to about 7.7GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9mm3.

Boron-doped diamond as a new heating element for internal-resistive heated diamond-anvil cell

ABSTRACTWe have developed an internal-resistive heated diamond-anvil cell (IHDAC) with a new resistance heater – boron-doped diamond (BDD) – along with an optimized design of the cell assembly, including a composite gasket. Our proposed technique is capable of heating a silicate/oxide material with (1) long-term stability (>1 h at 2500 K) and (2) uniform radial temperature distribution (±35 K at 2500 K across a 40-µm area), which are clear advantages over the conventional laser-heated and internal-heated DACs. In addition, the achieved temperature in this study was greater than 3500 K, which mostly covers the possible geotherm of the entire lower mantle. In situ X-ray diffraction (XRD) measurement and ex situ chemical analyses confirmed that weak XRD intensity from the BDD heater and chemical inertness (no boron diffusion into silicate samples). This newly developed IHDAC with a BDD heater can be used to determine the phase diagrams of mantle materials with high precision and be used in lower-mantle petrology.

Patient and Organ Specific Quality Assurance Phantom Insert for Stereotactic Body Radiation Therapy of Prostate Cancer1

Patient and Organ Specific Quality Assurance Phantom Insert for Stereotactic Body Radiation Therapy of Prostate Cancer1

Tightness Assessment of Bolted Flange Connections Considering the Creep Effect of Gasket

The tightness of bolted flange connections is the important guarantee to meet the safety operation for a long period, the creep effect of gasket may affect the tightness of bolted flange connections under high temperature conditions due to its creep deformation. Considering the creep effect of metal flexible graphite composite gasket under high temperature, the deformation compatibility equation of bolted flange connection system was deduced. The time-dependence of flange rotation, the gasket deformation and the gasket contact stress were studied systematically. Moreover, the influencing factors of leakage rate were analyzed in detail. Finally, based on the theory of tightness, the safety assessment method due to leakage rate was constructed under high temperature. Results presented the gasket stress increases linearly from inside to outside and the gasket stress became lower and lower with the creep time extended. The time-dependent leakage rate of bolted flange connections was deduced, and the tightness assessment can be made conveniently according to the proposed method.

Four-probe electrical measurements with a liquid pressure medium in a diamond anvil cell

We describe a technique for making electrical transport measurements in a diamond anvil cell using an alcohol pressure medium, permitting acute sensitivity while preserving sample fidelity. The sample is suspended in the liquid medium by four gold leads that are electrically isolated by a composite gasket made of stainless steel and an alumina-loaded epoxy. We demonstrate the technique with four-probe resistivity measurements of chromium single crystals at temperatures down to 4 K and pressures above 10 GPa. Our assembly is optimized for making high precision measurements of the magnetic phase diagram and quantum critical regime of chromium, which require repeated temperature sweeps and fine pressure steps while maintaining high sample quality. The high sample quality enabled by the quasi-hydrostatic pressure medium is evidenced by the residual resistivity below 0.1 μΩ cm and the relative resistivity ratio ρ(120 K)/ρ(5 K) = 15.9 at 11.4 GPa. By studying the quality of Cr's antiferromagnetic transition over a range of pressures, we show that the pressure inhomogeneity experienced by the sample is always below 5%. Finally, we solve for the Debye temperature of Cr up to 11.4 GPa using the Bloch-Gruneisen formula and find it to be independent of pressure.

A design of backing seat and gasket assembly in diamond anvil cell for accurate single crystal x-ray diffraction to 5 GPa

We designed a new cell assembly of diamond anvil cells for single crystal x-ray diffraction under pressure and demonstrate the application of the cell to the crystallographic studies for ice VI and ethanol high-pressure (HP) phase at 0.95(5) GPa and 1.95(2) GPa, respectively. The features of the assembly are: (1) the platy anvil and unique-shaped backing seat (called as "Wing seat") allowing the extremely wide opening angle up to ±65°, (2) the PFA-bulk metallic glass composite gasket allowing the easy attenuation correction and less background. Thanks to the designed assembly, the R(int) values after attenuation corrections are fairly good (0.0125 and 0.0460 for ice VI and ethanol HP phase, respectively), and the errors of the refined parameters are satisfactory small even for hydrogen positions, those are comparable to the results which obtained at ambient conditions. The result for ice VI is in excellent agreement with the previous study, and that for ethanol HP phase has remarkable contributions to the revision to its structure; the H12 site, which makes gauche molecules with O1, C2, and C3 sites, may not exist so that only trans conformers are present at least at 1.95(2) GPa. The accurate intensities using the cell assembly allow us to extract the electron density for ethanol HP phase by the maximum entropy method.

Application of a new composite cubic-boron nitride gasket assembly for high pressure inelastic x-ray scattering studies of carbon related materials

We have developed a new composite cubic-boron nitride (c-BN) gasket assembly for high pressure diamond anvil cell studies, and applied it to inelastic x-ray scattering (IXS) studies of carbon related materials in order to maintain a larger sample thickness and avoid the interference from the diamond anvils. The gap size between the two diamond anvils remained ~80 μm at 48.0 GPa with this new composite c-BN gasket assembly. The sample can be located at the center of the gap, ~20 μm away from the surface of both diamond anvils, which provides ample distance to separate the sample signal from the diamond anvils. The high pressure IXS of a solvated C(60) sample was studied up to 48 GPa, and a pressure induced bonding transition from sp(2) to sp(3) was observed at 27 GPa.

Elastic anisotropy of ferromagnesian post-perovskite in Earth's D” layer

We report experimental observation of a sizable elastic anisotropy in a polycrystalline sample of ferromagnesian silicate in post-perovskite (ppv) structure. Using a novel composite X-ray transparent gasket to contain and synthesize ppv in a panoramic diamond-anvil cell along with oblique X-ray diffraction geometry, we observed the anisotropic lattice strain and {1 0 0} or {1 1 0} slip-plane texture in the sample at 140 GPa. We deduced the elasticity tensor ( c ij ), orientation-dependent compressional wave velocities, polarization-dependent shear-wave velocities, and the velocity anisotropy of the silicate ppv. Our results are consistent with calculations and indicate that with sufficient preferred orientation, the elastic anisotropy of this phase can produce large shear-wave splitting.

An internally heated composite gasket for diamond-anvil cells using the pressure-chamber wall as the heating element

The implementation of a heating element to a composite gasket for high-temperature applications in the diamond-anvil cell was developed based on a double-gasket assemblage. The heating element is a thin platinum wall that covers the central borehole of the metal–ceramic–metal composite gasket and interconnects the two metal component parts of the gasket. Applying electric powers up to 35 W to the two gasket metal components result in ring-like heating around the sample inside the pressure chamber with temperatures exceeding ∼2000 K in individual cases. The ring-like distribution of the maximum temperature located at the pressure-chamber wall facilitates a homogeneous temperature distribution at the sample position. As a consequence of the concentration of the heating power to the pressure chamber region, gradients of surface temperatures, both at the gasket and the diamond anvil, appear to be more pronounced compared with those known for classical external electrical heating. Apart from the tests of the mechanical stability on high-pressure operation in the diamond anvil cell at room temperature, the influence of the anvils in contact with the gasket on the characteristic power–temperature curves, temperature gradients and thermal equilibration resulting from changes in electrical power settings have been evaluated within the scope of a series of experimental investigations.

Interfacial tension measurement of Ni-S liquid using high-pressure X-ray micro-tomography

High-pressure, high-temperature X-ray tomography experiments have been carried out using a large volume toroidal cell, which is optimized for interfacial tension measurements. A wide anvil gap, which corresponds to a field of view in the radiography imaging, was successively maintained to high pressures and temperatures using a composite plastic gasket. Obtained interfacial tensions of Ni-S liquid against Na, K-disilicate melt, were 414 and 336 mN/m at 1253 and 1293 K, respectively. Three-dimensional tomo-graphy images revealed that the sample had an irregular shape at the early stage of melting, suggesting either non-equilibrium in sample texture and force balance or partial melting of surrounding silicate. This information cannot always be obtained from two-dimensional radiographic imaging techniques. Therefore, a three-dimensional tomography measurement is appropriate for the precise interfacial measurements.

Finite-element modeling of stresses and strains in a diamond anvil cell device: case of a diamond-coated rhenium gasket

The stresses and strains in a diamond anvil cell device were investigated using a finite-element code NIKE2D for the case of an ultra-hard composite gasket material. The pressure distribution in a diamond-coated rhenium gasket was measured by the energy dispersive diffraction technique to 213 GPa and compared with the finite-element modeling results. We examine various models for the mechanical properties of diamond-coated rhenium gasket as well as for diamond failure for shear stresses exceeding 100 GPa. The elastic and plastic properties of gasket were varied such that a good agreement between the experimentally measured pressure distribution and the computational pressure profiles were obtained. As a result, we obtained the effective Young’s modulus, Poisson’s ratio, yield stress for indented gasket, linear hardening modulus, and hardening parameter value for this layered ultra-hard composite gasket material. Future diamond design strategies for attainment of extreme high pressures using ultra-hard gasket materials are also discussed.