Experimental Research on Key Factors Influencing the Expansion Performance of New Type Sealing Materials

To improve the borehole sealing effect, especially that of coal seam with low permeability and micro fissures, this paper takes the expansion rate of the sealing material as the response value and establishes the quadratic model embracing the expansion rate and various experimental factors by designing orthogonal experiments. The response surface is used to further determine the significance order of each key factor according to the expansion rate and adjust the admixture content to obtain the optimal ratio of the sealing material. For the research investigating a sealing material, the optimal ratio of the sealing material is obtained: the content of water reducing agent of 0.5%, the content of retarder of 0.04%, water-cement ratio of 0.8, and the content of expansion agent of 10%. At this time, the expansion rate reaches 3.136%. Besides, a scanning electron microscope is used to observe the microscopic morphology of the material. According to the scanning electron microscopy analysis of new borehole sealing materials, the surface of the new borehole sealing material shows no holes and possesses compactness; and a large amount of ettringite is formed on the surface of the hydration product of hardened cement slurry. The ettringite improves the expansibility of the material. The new sealing material provides a new idea for gas sealing, which is of great significance to improve the efficiency of borehole extraction, improve the utilization rate of resources, and prevent gas accidents.

Investigation of wear mechanics and behaviour of NiCr metallic foam abradables

Current aero-engine sealing materials are reaching their operating limit, as manufacturers seek more efficient engines with longer service lives. Even when utilised in optimum conditions, current materials have inconsistencies in performance due to variabilities in their microstructure, which lead to undesirable responses and events. As such, a new generation of sealing materials is required. Metallic foams are one such material, given the opportunities that exist to both engineer material properties, and achieve relatively consistent microstructures when compared to the current class of thermally sprayed abradable materials. In this study, the abradability of a nickel (70%)–chromium (30%) (NiCr) alloy foam is investigated, with the role of cell size and filler material considered. Tests are performed on a representative high-speed test rig, where a flat blade is used to simulate an aero-engine incursion event. A series of in situ measurement techniques, such as force, temperature and stroboscopic wear measurements are used to characterise the incursion, with DIC (Digital Image Correlation) techniques also employed to investigate breakdown of the foam. Unfilled foams were shown to lead to high blade wear, with the inclusion of filler materials leading to load transfer and collapse of the foam away from the incursion site, along with improved fracture. Both load transfer and ligament collapse mechanisms were found to promote more favourable rub mechanics at all incursion rates tested.

Soft tissue dimensional changes after alveolar ridge preservation using different sealing materials: a systematic review and network meta-analysis

Background Alveolar ridge preservation (ARP) is a proactive treatment option aiming at attenuating post-extraction hard and soft tissue dimensional changes. A high number of different types of biomaterials have been utilized during ARP to seal the socket, but their effectiveness in terms of soft tissue outcomes has rarely been investigated and compared in the literature. Objective To evaluate the efficacy of different types of membranes and graft materials in terms of soft tissue outcomes (keratinized tissue width changes, vertical buccal height, and horizontal changes) after ARP, and to assign relative rankings based on their performance. Materials and methods The manuscript represents the proceedings of a consensus conference of the Italian Society of Osseointegration (IAO). PUBMED (Medline), SCOPUS, Embase, and Cochrane Oral Health’s Information Specialist were utilized to conduct the search up to 06 April 2021. English language restrictions were placed and no limitations were set on publication date. Randomized controlled trials that report ARP procedures using different sealing materials, assessing soft tissue as a primary or secondary outcome, with at least 6-week follow‐up were included. Network meta-analysis (NMA) was performed using mean, standard deviation, sample size, bias, and follow-up duration for all included studies. Network geometry, contribution plots, inconsistency plots, predictive and confidence interval plots, SUCRA (surface under the cumulative ranking curve) rankings, and multidimensional (MDS) ranking plots were constructed. Results A total of 11 studies were included for NMA. Overall, the level of bias for included studies was moderate. Crosslinked collagen membranes (SUCRA rank 81.8%) performed best in vertical buccal height (VBH), autogenous soft tissue grafts (SUCRA rank 89.1%) in horizontal width change (HWch), and control (SUCRA rank 85.8%) in keratinized mucosa thickness (KMT). Conclusions NMA confirmed that the use of crosslinked collagen membranes and autogenous soft tissue grafts represented the best choices for sealing sockets during ARP in terms of minimizing post-extraction soft tissue dimensional shrinkage. Clinical relevance Grafting materials demonstrated statistically significantly better performances in terms of soft tissue thickness and vertical buccal height changes, when covered with crosslinked collagen membranes. Instead, soft tissue grafts performed better in horizontal width changes. Non-crosslinked membranes and other materials or combinations presented slightly inferior outcomes.

Techniques and Materials for Optical Fiber Sensors Sealing in Dynamic Environments with High Pressure and High Temperature

We detail a study of the techniques and sealing materials for optical fiber sensors used in dynamic environments with high pressure (>300 bar) and high temperature (>300 °C). The sealing techniques and materials are the key for the robustness of sensors in harsh dynamic environments, such as large combustion engines. The sealing materials and techniques studied in this work are high-temperature epoxies, metallic polymer, metallic solders, glass solder, cement, brazing and electroless nickel plating. Because obtaining high temperature simultaneously with high pressure is very difficult in the same chamber in the laboratory, we developed a new and simple method to test sealed fibers in these conditions in the laboratory. In addition, some sensors using the materials tested in the laboratory were also field tested in real thermoelectric combustion engines. The study also discusses the methods of fabrication and the cost−benefit ratio of each method.

Hydrophobic Dielectric Sealing Material Enabled Highly Reliable Electrical Connectors for Downhole Data and Power Transmission Application

A high-strength dielectric sealing material has been developed for sealing electrical connectors, feedthroughs, bulkheads, and interconnectors. X-ray diffraction analyses have identified that the microstructures of the sealing material could be of amorphous and α-phase mixed morphology, α+β mixed phase, and β-phase dominated tetrahedral microstructure, which primarily depend upon the material processing temperature. The electrical insulation resistance of the β-phase dominated sealing material have nearly two times higher than that of α+β mixed phase sealing material. Both β-phase dominated and α+β mixed phase sealing materials have shown water repelling properties, while amorphous glass phase has shown hydrophilic properties. If a 5,000MΩ insulation resistance is also regarded as baseline for a downhole electrical connector, the maximum operation temperature of α+β mixed phase sealing materials is around 240°C while that of the β-phase dominated sealing material can be up to 300°C. Furthermore, a thermo-mechanical modeling has been developed to quantify if a designed electrical connector has sufficient reliability in the hostile wellbore or downhole environments. The temperature- and pressure-dependent seal compression have suggested that the temperature-related safety factor should be chosen in the range from 2.0 to 5.0 while the pressure-related safety factor should be chosen in the range from 1.5 to 2.0 to ensure 10-20 years electrical connector downhole operating reliability. The qualification tests from prototyped electrical connectors, under 260°C/32,000PSI simulated water-fluid based conditions, have demonstrated that such high-strength sealing material sealed electrical connector could be integrated with logging while drilling (LWD) or/and measurement while drilling (MWD) tools for providing long-term reliable signal, data, and electrical power transmission services, regardless of a water-based or moisture-rich wellbore or/and downhole environment.

Investigation of local hot spots in sealing rings with different sealing materials

The local high temperature in the sealing pair is prone to cause local wear, which easily leads to seal failure. In this paper, a numerical method based on the finite element method is proposed to investigate the local high-temperature hot spot in a sealing ring with different sealing materials. The distribution of hot spots on the sealing surface is visualized by numerical computations. The critical speeds of the hot spot for the metal, composite, and powder metallurgical sealing materials are obtained under different friction coefficients. Based on the obtained results, the quantitative correlation between the critical speed of the hot spot and elastic modulus, thermal conductivity, specific heat capacity, thermal expansion coefficient, and seal sizes is determined. Then, a test method is designed to evaluate the thermal instability of the sealing ring. Scanning electron microscopy is utilized to examine the surface morphology of the sealing rings after the hot spots appear. The results of the present study demonstrate that the proposed method is consistent with the experiment. It indicates the effectiveness of the simulation method for investigating local hot spots in the sealing ring.

Preparation of Room Temperature Vulcanized Silicone Rubber Foam with Excellent Flame Retardancy

To retard the spread of fire in many cases with sealing materials is significant. A series of silicone rubber foam materials were prepared with room temperature vulcanization and foaming reactions. The morphology, chemical structure, cell structure, and thermal stability were investigated and results proved that the synthesis of silicone rubber was successful in a wide range of feed ratios. The fire-retardant tests were carried out to study the fire-proof property of the composite materials, and the excellent performance showed a promising prospect for wide application in sealing materials.