Composite Seal Research Articles

Influence of Endodontic Cavity Design on Interfacial Voids, Class II Resin Composites Sealing Ability and Tooth Fracture Resistance: An In Vitro Study.

Objective: The aim of this in vitro investigation is to study the effect of endodontic cavity design on interfacial voids, class II resin composite sealing ability, and fracture resistance in mandibular premolars. Methods: A total of 48 single-rooted mandibular premolars received compound class II preparations with either traditional flare access cavities (group A) or contracted endodontic cavity preparations (group B). Each study group was subdivided according to the coronal restoration into two sub-groups as α and β. In the α group, a microhybrid composite was used after etch-and-rinse bonding technique using an MDP-containing universal adhesive. In the β group, a self-adhesive composite was used as coronal restoration after endodontic treatment (n = 12) for each subgroup. A micro-CT analysis was performed to assess the obturation interfacial voids and tracing of class II cervical interfacial adaptation. The tooth fracture resistance testing was then performed adding an extra group of 12 sound non-prepared teeth, which were tested as the control for fracture strength testing. A one-way ANOVA and post-hoc testing were used together with descriptive statistics for an analysis of the mean values of obturation interfacial voids. A two-way ANOVA was used to assess the fracture resistance test results, and to find the influence of endodontic access design and the type of composite material on the fracture resistance testing. Chi-square testing was employed to analyze the cervical interfacial seal of the class II restorations. Results: A one-way ANOVA revealed that there were no statistically significant differences between test groups in the amount of obturation interfacial voids (p > 0.05). There were no statistically significant differences between test groups in terms of cervical interfacial sealing ability (p > 0.05). A two-way ANOVA revealed that no statistically significant differences between test groups including the control group existed in terms of the fracture resistance testing (p > 0.05). Conclusions: Although it does not improve tooth fracture resistance, the contracted endodontic access cavity does not deteriorate the quality of obturation in terms of the interfacial porosity. The self-adhesive composite does not improve the efficiency of cervical interfacial adaptation or tooth fracture resistance regardless of the endodontic access cavity shape, yet it revealed a substantial load-bearing capacity.

Failure analysis and structural improvement of helicopter landing gear seals based on experiments and three-dimensional numerical simulation

The utilization of O-ring seal structures in landing gears has historically been associated with high rates of failure. Therefore, this study analyzes helicopter landing gear friction failures based on experimental and numerical simulations. The model is designed to replicate the failure phenomena including “seal extrusion”, “seal leakage”, “seal wear”, and “seal distortion”, and to further investigate causes of failure. Corresponding failure criteria are also presented. Addressing the deficiencies inherent in the original O-ring structure, three composite seal structures—namely, the VL seal, double triangle seal, and T-seal—are introduced to enhance the respective seal structure of the buffer pillar. The findings exhibit that, following the transition to the composite seal structure, the strain peaks are optimized. Finally, this paper offers optimal contact pressure ranges for the optimized seals.

Study on expansion characteristics of Al–Al2O3 composite seals for intermediate‐temperature solid oxide fuel cell

AbstractAl2O3‐based composite seal with 10 wt% Al powder addition (A10) possesses excellent plastic and mechanical performance under wide temperature range of solid oxide fuel cell. The thickening phenomenon of A10 seal between 250°C–400°C and 600°C–750°C is caused by the thermal expansion of organic additives and the volume expansion when solid–liquid Al react with oxygen to form Al2O3. The thickness change rate reaches the maximum which is about 5% at 300°C and is about 4.46% at 650°C. The Gibbs free energy for reaction between Al and Al2O3 in the temperature range of 523–1 023 K is all less than 0, which is proved by the fact that A10 exhibits excellent self‐expansion and thermodynamic properties in the solid oxide fuel cell operating temperature.

Ni–Co spinel based oxide as new type of additive to glass seal for solid oxide fuel cells

Glass seals utilized in Solid Oxide Fuel Cells (SOFCs) can be subject to modification through the incorporation of oxide additives to bolster their mechanical strength. This research focuses on a novel class of additives, specifically protective coating materials designed for alloy interconnects. It is crucial to emphasize that the glass seal interfaces directly with the protective coating, bypassing direct contact with the alloy itself. The efficacy of this approach is exemplified through the utilization of Ni–Co spinel-based oxide, established as an effective protective substance for stainless steel interconnects. The introduction of a minute quantity of Ni–Co oxides does not induce alterations in the glass seal properties, encompassing phase structure, microstructure, thermal expansion coefficient (CTE), and softening behavior. The Ni–Co oxide additive serves to mitigate the glass devitrification tendency, leading to a substantial augmentation in shear strength at the seal-interconnect interface and a marked enhancement in sealing properties. The composite seal, enriched with 3.0 wt% Ni–Co oxide, showcases superior sealing performance, demonstrating exceptional stability throughout a rigorous 1200-h test. The average leakage rate during this test period stands at 0.0024 sccm⋅cm−1. The incorporation of Ni–Co oxide triggers the formation of needle-shaped crystals, playing a pivotal role in averting channel void formation and augmenting the bonding strength between the seal and interconnect. Consequently, this fortifies gas tightness, ensuring the maintenance of outstanding sealing performance over an extended duration.

Wettability and thermal shock resistance of novel h-BN based ceramic seals for nitrogen oxide sensor

In this study, the novel h-BN based ceramic seals are investigated for nitrogen oxide sensor. The alkaline-free glass (H4) exhibited good wettability on the Fe-16Cr alloy and yttria stabilization zirconia (YSZ) chip and the wetting rate obviously accelerated when the temperature exceeds 940 ℃. The shape parament Ɛ and wetting area of the H4 glass on the substrate of Fe-16Cr alloy and YSZ chip reach the maximum value at 900 °C that Ɛ was 1.46 and wetting area was 146.58 mm2 for Fe-16Cr alloy while Ɛ was 0.89 and wetting area was 165.99 mm2 for YSZ chip. In addition, the addition of 20 wt% H4 glass to hexagonal boron nitride (h-BN) formed BN-20 composite seal that can be effectively reduce the formation of substrate pores, microcracks and exhibited excellent chemical compatibility and stability, which shows that BN-20 seal is can be considered as a promising seal for nitrogen oxide sensors.

Research on a Laboratory Technique to Prepare a Rejuvenating Composite Seal and Test Its Long-Term Water Stability

Research on a Laboratory Technique to Prepare a Rejuvenating Composite Seal and Test Its Long-Term Water Stability

Improvement of thermal cycle stability of YSZ-glass composite seals for intermediate temperature solid oxide fuel cell

Glass ceramic seals have been widely used in solid oxide fuel cell (SOFC). However, the sealing performance of seals is a big challenge for SOFC operating at high temperature. In this work, the gas tightness, chemical compatibility and thermal cycle stability of the glass-based seals with various proportions of YSZ and glass are evaluated and discussed. The study showed that when 20 wt% YSZ is added to H4 glass, the as-prepared glass ceramic seal (denoted as H4-20) exhibited extremely low leakage rate of 0.00171 sccm cm−1 under input pressure of 20.7 kPa and wide temperature range from 650°C to 800°C. In addition, the leakage rate of H4-20 glass ceramic seal below 0.004 sccm cm−1 was obtained after 10 thermal cycles at 750 °C. The SEM analysis indicated that the H4-20 glass ceramic seal could form well bonding interface between the interconnect/seal/cell. The above results prove the possibility of the H4-20 glass ceramic seals to be considered for intermediate temperature SOFC application.

Stability of the Structure and Properties of PKH13M2-BN Composite Seal Material for Steam Turbines Under Long-Term Thermal Exposure

Stability of the Structure and Properties of PKH13M2-BN Composite Seal Material for Steam Turbines Under Long-Term Thermal Exposure

Mechanical behavior of YSZ-glass composite seals for solid oxide fuel cell application

The long-term operation of solid oxide fuel cell stack critically depends on the joint strength between cells and interconnect alloy. In this work, 20 wt% YSZ (Y 2 O 3 stabilized ZrO 2 ) was added into different kinds of glass to form H1-20 and H4-20 composite seals. It was focused on the mechanical behavior between YSZ-glass composite seals and Fe–16Cr alloy under various thermal cycles by shear force testing and tensile force testing. The shear strength and the tensile strength between H4-20 seals and Fe–16Cr alloy were higher than that of H1-20. Two composite seals differed in characteristic temperature, viscosity, and crystalline phase with possible impacts on the joint strength. The interfacial composition between H1-20 and Fe–16Cr alloy was different from that of H4-20. Based on examination results, four possible fracture modes were proposed to illustrate the failure mechanism between composite seals and alloy.

Testing and evaluation for long-term skid resistance of asphalt pavement composite seal using texture characteristics

As a common means to improve the skid resistance of asphalt pavement, chip seal is widely used for road surface treatment and preventive maintenance. As the aggregate is progressively dislodged under repeated wheel loads, continuous loss of the surface texture characteristics occurs, and its skid resistance increasingly declines. Therefore, it is necessary to further refine the process of chip seal. In addition, in order to scientifically evaluate its performance and accurately predict the deterioration, the relationship between the surface texture characteristics and the skid resistance needs to be quantitatively established. In this paper, a composite seal structure was proposed by applying sand-containing fog seal layer on top of chip seal. Firstly, four seal schemes (i.e., 3–5 mm chip seal, 5–9.5 mm chip seal, 3–5 mm composite seal and 5–9.5 mm composite seal) were designed and loaded by a four-wheel rotary accelerated abrader. Secondly, the skid resistance indexes of each scheme were investigated under different abrasion times using pendulum meter and sand patch method. In this process, the three-dimensional texture characteristic parameters (i.e., Ssk, Spd, Spc, Vmp and Vmc) of the specimen surface were also obtained by laser scanning. Finally, by analyzing the data, the relationship between the seal texture characteristic parameter and the skid resistance index was established, and the decay law prediction model of the skid resistance for four seal schemes was derived. It is found that the pendulum value and texture depth of the seal decreased with the increase of abrasion times, but the composite chip seal can reduce the decreasing rate of skid resistance index. Sq, Spd, Spc and Vmc showed good synergistic decay laws with the British pendulum number (BPN) and mean texture depth (MTD), among which Spc had the best correlation and can be used as an parameter to characterize the skid resistance of the seal. The relationship and decay prediction model established in this paper can be used to characterize the skid resistance of chip seal and predict the decay law of the skid resistance.

Thermal anti-cracking investigation of asphalt-based seal technology for airport base layer in frozen ground region

In frozen ground regions, the problems of subgrade frost damage and slab cavity were common distresses of cement concrete pavement in civil airports, causing the major safety hazard during the daily operation of airport. It was necessary to explore prevention technology of airport pavement subgrade due to frost damage. This research investigated the anti-cracking and thermal properties of asphalt-based composite seal as intermediately isolated airport base layer in cold regions. The stiffness and stress relaxation behaviors of binders were evaluated at low temperatures by bending beam rheometer test, in terms of various modifiers with styrene-butadiene rubber and liquid nitrile rubber. Based on the dissipation energy method, the viscoelastic characteristics of asphalt materials were analyzed with Burgers model. Additionally, the response regions of low-temperature rheology were expanded through the master curve establishment of flexural creep compliance. The thermal properties of binder were characterized by thermal gravity analysis and differential scanning calorimetry test. Finally, the relationships between various indices were conducted to release the polymer modification impacts on thermal cracking resistance of asphalt-based seal technology through statistical analysis. This study revealed that the cracking resistance and thermal properties of asphalt-based composite seal at low temperature was essential and efficient and should be recommended the consideration for airport pavement in cold regions.

Characterization of a barium–calcium–aluminosilicate glass/fiber glass composite seal for intermediate temperature solid oxide fuel cells

The properties of BaO–CaO–Al2O3–SiO2 (BCAS) glass seal materials reinforced with 5–30wt.% glass fiber are investigated. The seals are prepared by solid mixing process. The microstructure and phase content of the samples are studied. Mechanical properties are investigated by Vickers micro-hardness, nano-indentation and compression tests. The thermal properties of the samples are evaluated by conducting a dilatometry analysis. The electrical conductivity and leak resistance of the seal materials are measured at high temperatures. Increasing the amount of glass fiber in the composite samples decreases the magnitude of the thermal expansion coefficient. It is found the addition of just 5wt.% of glass fiber (GF5sample) increases the indentation fracture toughness of the seals by ∼280% without impairing other properties. It is also found that the GF5 sample has high electrical resistivity with the activation energy of 63.7kJ/mol and very low leak rate of 1.7×10−4sccm/cm at 750°C.

Experimental Study on the Optimization of Polymer-Modified Cement-Based Composite Sealing Materials and Mechanical Properties and Permeability of Cemented Coal Bodies

As a critical technical issue, gas extraction borehole sealing significantly restricts the effects of gas extraction. Polymer-modified cement-based composite (PMCC) sealing materials were developed to improve the sealing effect of gas extraction drilling. In this study, a self-built mechanical property and permeability test platform for grouting-based cemented coal bodies was used to test the viscosity, gelation time, and mechanical properties of PMCC sealing materials and the permeability of cemented coal bodies. Through the obtained relevant results, it was demonstrated that the material viscosity of PMCC sealing materials and the permeability and compressive strength of cemented bodies are under the influence of additive ratios. Moreover, the viscosity of sealing materials was found to be linearly related to the gelation time. In particular, the higher the viscosity, the shorter the gelation time. Additionally, on one hand, it was found that the viscosity of such sealing materials is positively correlated to the compressive strength of cemented coal bodies. On the other hand, it forms a negative correlation with their permeability. Based on relevant analysis outcomes, it was deemed that the sufficient hydration reaction and the interspace reticulate microstructure formed by the polymer of PMCC sealing materials allow the cemented coal body to achieve high compressive strength and low permeability.

Effects of reinforcements on the hardness of composite seal rings

Composite seal rings are alternate high-performance materials for supplying to engines and compressors in several industries. Polytetrafluoroethylene (PTFE) and Polyetheretherketone (PEEK) seals reinforced by carbon powder and glass fibers were investigated. The seal specimens were heated at 150–200 °C for a duration of 24 h. The hardness and microstructure of specimens were observed after the test. Taguchi technique was used for design of experiment to analyzed the parameters that affected to the seal hardness. The hardness of all samples decreased when increasing temperature, and the hardness of PTFE and PEEK with carbon powder slightly increased after heating at higher temperature. The PEEK with 30% carbon showed the highest hardness compared to the others at temperature of 150 and 200 °C. The carbon reinforcements promoted increasing hardness of the composite seal rings. Besides, the reinforcements showed a good distribution in the composite matrix which was nearly the same as the microstructure of the compressor seal ring used in industrial parts.

Barium-calcium aluminosilicate glass/mica composite seals for intermediate solid oxide fuel cells

In this paper, the effects of phlogopite mica addition on the properties of barium-calcium-aluminosilicate (BCAS) glass seals are studied. Accordingly, BCAS glass powder is mixed with up to 30 wt% of phlogopite mica; the resulting mixture is formed and sintered at different temperatures. The microstructure and phase content of the samples are then analyzed by scanning electron microscope (SEM) and X-ray diffraction method. Mechanical properties including, hardness, compression strength, fracture toughness and Young's modulus are investigated. The coefficient of thermal expansion (CTE) and softening temperature of the seals are measured. The electrical conductivity of the selected specimens is studied by applying the electrochemical impedance spectroscopy method. The performance of the composite seals is analyzed under fuel cell working conditions by the leak test. It is found that the samples with the mica content of more than 10 wt% cannot be sintered to near full relative density. The sintering temperature above 750°C raises the risk of unfavorable reactions between mica and the BCAS glass matrix. It is also revealed that the addition of 5 wt% phlogopite increases Young's modulus and fracture toughness of the BCAS glass seals by 13% and ~633%, respectively, without impairing other mechanical and thermal properties. The composites seals with more than 10 wt% of mica content don't meet the required mechanical properties demands for SOFC seals. It is found that the composite seal with 5 wt% of phlogopite mica has very low electrical conductivity and leak rate of less than 1.2×10−4sccm/cm. This composite seal shows high thermal stability with ~5% reduction in CTE after 10 cycles under SOFC working conditions and consequently can be considered as a promising seal for SOFCs.

Comprehensive Life Cycle Environmental Assessment of Preventive Maintenance Techniques for Asphalt Pavement

Preventive maintenance (PM) is regarded as the most economical maintenance strategy for asphalt pavement, but the life cycle environmental impacts (LCEI) of different PM techniques have not yet been comprehensively assessed and compared, thus hindering sustainable PM planning. This study aims to comprehensively estimate and compared the LCEI of five PM techniques then propose measures to reduce environmental impacts in PM design by using life cycle assessment (LCA), including fog seal with sand, micro-surfacing, composite seal, ultra-thin asphalt overlay, and thin asphalt overlay. Afterwards, ten kinds of LCEI categories and energy consumption of PM techniques were compared from the LCA phases, and inventory inputs perspectives, respectively. Results show that fog seal with sand and micro-surfacing can lower all LCEI scores by more than 50%. The environmental performance of five PM techniques provided by sensitivity analysis indicated that service life may not create significant impact on LCA results to some extent. Moreover, four PM combination plans were developed and compared for environmental performance, and results show that the PM plan only includes seal coat techniques that can reduce the total LCEI by 7–29% in pavement life. Increasing the frequency of seal coat techniques can make the PM plans more sustainable.

Performance of Al2O3 particle reinforced glass-based seals in planar solid oxide fuel cells

Glass-based materials are usually considered as excellent seals for jointing adjacent components in planar solid oxide fuel cells, but the uncontrollable crystallization in the glass may cause delamination and micro-cracks in such seals. To solve this problem, Al2O3 ceramic particles were added to a BaO–CaO–Al2O3–B2O3–SiO2 glass system to reduce negative effects caused by crystalline phase on the gas tightness and the joint strength in the seals. At an operating temperature of 750 °C, the glass-based seals with 20 wt% Al2O3 addition (GA80) exhibited extremely low leakage rates (~0.002 sccm/cm under an input gas pressure of 13.6 kPa) and higher shear strength (3.31 MPa). The Al2O3 ceramic addition and the crystalline phase BaAl2Si2O8 reinforced the glass matrix. Further thermal cycle analyses indicated that leakage rates for the GA80 seals remained at around 0.0025 sccm/cm after 10 thermal cycles, which was consistent with minor microstructural change and good interface bonding. Single cell testing with of GA80 seals was performed and the results demonstrated stable electrochemical performance through 6 thermal cycles at an open circuit voltage of 1.16–1.18 V, as well as a power density above 546 mW/cm2 at a current density of 925 mA/cm2. These results showed the high thermal cycle stability of the glass/Al2O3 composite seals in intermediate temperature planar solid oxide fuel cells.

Finite-element analysis and structure optimization of X-O composite seal of cone bit

The seal is the key part of the cone bit. To reduce the failure probability, a new seal was designed and studied. The sealing performance and structure optimization of the X-O composite seal was analyzed and compared by finite-element analysis. The stress and contact pressure were analyzed to establish the main structural parameters that affect sealing performance and the direction of the structural optimization. By optimizing these structural parameters, including the height, and the radial and axial arc radii, an optimized structure is obtained. The results show that (1) the X-O composite seal can meet the seal requirement, the excessive height of the X seal ring is the root cause of the uneven distribution of stress, pressure, and distortion. (2) A new seal structure is obtained, the distribution of pressure and stress is reasonable and even, and the values of stress and pressure are reduced to avoid distortion and reduce the wear. Finally, the field test results of the X-O composite seal of cone bit showed that the service life of the bit bearing increased by 16% on average and the drilling efficiency increased by 11% on average compared with the original cone bit with the O seal ring.

Investigating the performance of Glass/Al2O3 composite seals in planar solid oxide fuel cells

Al2O3 ceramic was added to a CaO–B2O3–Al2O3–SiO2 glass system to improve mechanical properties and thermal cycle stability in solid oxide fuel cell composite seals. The performance of glass-based seals with different Al2O3 content was evaluated, including the shear strength and leakage rate of the composite seals. The results showed that HA80 composite seal, with 20 wt% Al2O3, had excellent joint strength and gas tightness. HA80 had the highest shear strength among specimens, reaching 3.83 MPa after heat treatment at 750 °C. Gas tightness was greatly improved by using HA80 composite seals, with leakage rates from 0.0007 sccm/cm to 0.0011 sccm/cm corresponding to gas input pressures varying from 13.6 to 68 kPa. The leakage rates remained stable about 0.0022 sccm/cm at the highest gas input pressure (68 kPa) during twenty thermal cycles because of improved interfacial bonding between the composite seals and adjacent components. The 5-cell stack was assembled and achieved an open circuit voltage of 5.78 V and maximum power output of 354 W at 750 °C, demonstrating that HA80 composite seal was suitable for SOFC application.

Waterproof and Antiscour Properties of Asphalt-Based Composite Seals for Airfield Base Layer

A new type of three-layer waterproof structure was developed to reduce the scour problem of concrete slabs by paving an asphalt-based composite seal layer between the cement-stabilized base and the cement concrete pavement. The asphalt-based composite seal layer consists of an upper layer (microsurfacing), a transition layer (microsurfacing), and a bottom layer (synchronous chip seal). A new construction method was proposed to guide the construction of the asphalt-based composite seal layer. The waterproof and antiscouring properties of the asphalt-based composite seal layer were evaluated by a permeability test, a high-resolution industrial computed tomography (CT) scanner, a scouring test, and a direct shear test. The permeability test showed that the three-layer structure possessed good waterproofing properties. The CT scans results showed that the asphalt-based composite seal layer was very dense due to effective compaction during the construction process. The scouring test indicated that the scouring resistance of the asphalt-based composite seal layer was much better than that of the cement-stabilized base. The results showed that the asphalt-based composite seal possessed decent resistance to scour and could effectively protect the base from the threat of scour. The cost analysis results showed that the proposed asphalt-based composite seal layer has a more competitive unit price compared with an asphalt concrete layer.