Sufficient Durability Research Articles

Advantages of Production and Operation of Innovational Storage Systems in Multimodal LNG-Transportation

The world gas consumption, as well as the needs in its transportation are growing constantly nowadays. Gas transportation in a liquid form has become a strong competitor for traditional pipelines. LNG can be transported by different transport means by sea, rivers, roads, railway. Tank-containers allow to transport LNG without its reloading into other tanks due to universal container construction. Traditional tank-containers are heavy, have limited lifespan and not sufficient durability. The innovational membrane tank-containers made of aluminum alloy with low scandium content solve the majority of the aforementioned technical problems. They provide the highest level of safety for dangerous cargo transportation, longer operation period and lower weight of the construction. The last two parameters influence positively the economic efficiency of using innovational tank-containers in multimodal LNG-transportation. The research compared the traditional steel and innovational aluminum-scandium tank-containers used in automobile and railway LNG-transportation. The innovational ones are more perspective for investment due to lower operational costs and lower depreciation rates. As an option the manufacturing could be also organized at shipbuilding yards, which are familiar with the technology of LNG-tankers construction. It allows to start new production without significant initial investments, to broaden the market and to increase the level of capacity usage.

Metal and Metal Oxide Electrocatalysts for Redox Flow Batteries

AbstractRedox flow batteries (RFBs) are one of the promising technologies for large‐scale energy storage applications. For practical implementation of RFBs, it is of great interest to improve their efficiency and reduce their cost. One of the key components of RFBs that can greatly influence the efficiency and final cost is the electrode. The chemical and structural nature of electrodes can modify the kinetics of redox reactions and the accessibility of the electroactive species to available active sites. The ideal electrocatalyst for RFBs must have good activity for the desirable redox reaction, provide a high surface area, and exhibit sufficient conductivity and durability over repeated use. One strategy is to coat the electrode with metal and metal oxide electrocatalysts. Metal electrocatalysts have the advantage of high conductivity, while metal oxide catalysts are usually less expensive and so more economically attractive. In order to gain a better understanding of the performance of the electrocatalysts in RFBs, a comprehensive review of the progress in the development of metal and metal oxide electrocatalysts for RFBs is provided and a critical comparison of the latest developments is presented. Finally, practical recommendations for advancement of electrocatalysts and effective transfer of knowledge in this field are provided.

Study on formability, mechanical property and finite element modeling of 3D-printed composite for metal-bonded diamond grinding wheel application

Increasing porosity and generating expected internal structure for metal-bonded grinding wheel are the critical enabling technologies for high performance grinding wheel fabrication. Conventional hot pressing sintering (HPS) fabrication process has little capability in active formation of pore structure. In this paper, metal 3D printing technology is applied to fabricate the composite used for metal-bonded diamond grinding wheel. Through the measurement of morphological properties, mechanical properties and forming limits, the formability and performance of 3D-printed composite are evaluated. To predict the mechanical performance and understand the failure behavior, the representative volume element (RVE) model is developed for the 3D-printed metal matrix composite. And final grinding experiment indicates that 1) The 3D printing technology for composite and complicated internal structure exhibits promising potential for high performance grinding wheel fabrication with inter-connected lubrication channel and sufficient mechanical strength; 2) The 3D-printed porous wheel demonstrates sufficient durability in grinding process and superior performance in grinding capability.

Self-assembled RuO2@IrOx core-shell nanocomposite as high efficient anode catalyst for PEM water electrolyzer

Herein, a self-assembled RuO2@IrOx core-shell heterostructure nanocomposite is designed and constructed to mediate oxygen evolution activity and sufficient durability. Enhanced by synergistic interactions of heterojunction between RuO2 and IrOx, the RuO2@IrOx nanocomposite reveals lower overpotential (215 mV at 10 mA cm−2) than RuO2 (260 mV at 10 mA cm−2) and IrO2 (316 mV at 10 mA cm−2). After assembled into a homemade single-cell PEM water electrolyzer, a lower cell voltage of 1.683 V at 1 A cm−2 for RuO2@IrOx anode is obtained, compared with RuO2 (1.715 V at 1 A cm−2) and IrO2 (1.748 V at 1 A cm−2). Additionally, the RuO2@IrOx anode shows good stability at 1 A cm−2 over a 300 h stability test due to the effective protection of IrOx shell. This work offers an effective strategy to design and construct high efficient and long-term stable catalysts simultaneously.

Very long-term outcomes of twisted auto-pericardial mitral annuloplasty.

During mitral annuloplasty, we twisted the harvested auto-pericardium to enable adequate ring sizing and implanted it to prevent ring-related complications. Indication for twisted auto-pericardial band (APB) was limited to patients with less than severe annular dilation to ensure high reproducibility and durability. The aim of this study was to investigate the long-term outcomes of twisted APB annuloplasty. From 1999 to 2009, 107 patients (62 ± 12years, degenerative 92 and infective endocarditis 15) with isolated posterior mitral leaflet (PML) prolapse with inter-commissural distance of 32mm or smaller underwent twisted APB annuloplasty. Of these, 104 patients without early leaflet repair failure were studied. Leaflet repairs were predominantly performed by quadrangular resection. Median APB size was 28mm. Follow-up rate was 98.1% and duration was 10.9 ± 4.8years. There were two early and 34 late deaths. Survival and freedom from cardiac-related death at 15years were 61.7% ± 5.6% and 83.8% ± 4.7%, respectively. Age and male sex were independent predictors of mortality. There were four late reoperations for recurrent severe mitral regurgitation (MR), three of which were due to new chordal rupture. Freedom from reoperation and freedom from moderate or severe MR at 15years were 93.1% ± 3.5% and 81.3% ± 6.2%, respectively. No patients developed hemolysis, ring dehiscence, or infective endocarditis. The long-term outcomes of twisted APB for isolated PML prolapse without severe annular dilation are satisfactory. Twisted APB annuloplasty may be a preferable option to reduce ring-related complications with sufficient durability.

Future prospects of zirconia for oral implants -A review.

Zirconia have been applied to dental implants as well as fixed dental prostheses due to their mechanical, esthetic and biocompatible performance. Moreover, they offer an advantage over titanium (Ti) implants, in that there is no risk of discoloration or hypersensitive reaction with allergy. In this review, the durability and tissue-compatibility of zirconia for the oral implants was mainly discussed. Hot isostatic pressing of Y-TZP had higher cyclic fatigue strength than Cp-Ti (Grade-2), leading the sufficient durability. Tissue-compatibility of zirconia; 1) Blast and acid-etching was effective for bone formation with synergetic effect of micro- and nano-topography. 2) Super-hydrophilic treatment, cold plasma in particular, enhanced initial attachment of osteoblast-like cells and oral keratinocytes. 3) Adherence of the periodontopathic bacteria on zirconia was similar to that on Cp-Ti, leading the necessity of surface modification.

Influence of short term oven aging on volumetric properties of asphalt concrete mixture containing modified Buton asphalt and limestone powder filler

In an effort to develop the use of modified Buton asphalt (MBA), this study designed a concrete asphalt mixture using the MBA as the main binding material and modified it with limestone powder fillers to produce concrete asphalt that has good resistance to aging. Short-term aging test was simulated in the laboratory on a loose mixture. The volumetric void in mixture (VIM), void in mineral aggregate (VMA) and void filled asphalt (VFB) values were evaluated on compacted specimens and had experienced STOA. Based on VIM, VMA and VFB values, it can be noted that mixture that only used MBA or mixture that combined MBA and limestone powder can provide resistance to bleeding or cracking, sufficient durability and stable interface adhesion between asphalt films and aggregate surfaces.

High Machinability of Plasma-Nitrided HPM80 Dies at 673K by PCD-Tools for Hot Mold-Stamping

HPM80 had been utilized as one of the martensitic stainless steel mold and die substrates for stamping. In particular, HPM80 mold was often used as hot-stamping molds for oxide glasses and optical polymers to fabricate the optical elements and DOE (Diffractive Optical Elements) with the aid of NiP (Nickel Phosphate) and NiWP (Nickel-Tungsten Phosphate) coatings. These machinable amorphous coatings were indispensable to cut and finish the tailored micro textures for DOE since HPM80 was difficult or nearly impossible to be finished by using the PCD (Poly-Crystal Diamond)-chipped tools. However, those coatings were fragile above 473 K; the original HPM80 must be modified to be fine machinable even by the diamond-chipped and coated tools for fine finishing to mirror-polished die surfaces with far less damage to cutting tools. These HPM80 substrates were plasma nitrided at 673 K under the nitrogen and hydrogen mixed gas flow to form the high content nitrogen super-saturated layer. Precise machinability experiment was performed with the use of the PCD coated WC (Co) tools to investigate the machinability of these nitrogen supersaturated HPM80 substrates. Two-phase fine-grained layer with higher nitrogen solute content than 2 mass% was machined in the ductile mode with adaptively high quality to shaping and finishing the mold die surface for stamping. Through the hardness testing, this nitrogen super-saturated die surface had higher hardness than 1400 HV; it had sufficient durability for long-term stamping operations. Finally, the turning test was employed to demonstrate that this nitrogen supersaturated HPM80 layer with the thickness of 40μm was machined with high quality to form the mirror-polished surface.

Cryo-milling with spherical crystalline cellulose beads: A contamination-free and safety conscious technology

Crystalline cellulose is a common inactive pharmaceutical additive. If this material can also be used to construct beads for the wet milling of pharmaceutical compounds, it could possibly address issues related to wear and contamination associated with zirconia and polyethylene beads. In this study, the model drug phenytoin was milled with spherical crystalline cellulose (SCC) in liquid nitrogen. The particle size of the milled product was found to be comparable to that obtained using zirconia beads, verifying the feasibility of using SCC beads for this purpose. Using a design of experiment approach, the bead amount, agitation speed, and milling time were all determined to have a significant effect on the milled particle size, giving a D50 value as low as 0.3 μm. No breakage of the SCC beads was observed during the milling process in durability tests under conditions that will degrade spherical D-mannitol beads, showing that this material exhibits sufficient durability. In addition, the variation in elastic modulus between beads was minimal. Because SCC is commercially available and easy to handle, the present wet milling technique is considered to have potential applications to the manufacture of pharmaceuticals on an industrial scale, as it shows sufficient milling capability and durability

Reflowable optical connector with glass-ceramic ferrule for advanced pluggable transceiver packaging

Abstract We describe a new physical-contact optical fiber connector/receptacle that can withstand a solder-reflow process with a maximum temperature of 260 °C for advanced pluggable transceiver packaging such as the co-packaging of photonic and electronic chips using the reflow process. We experimentally clarify the problems that occur in the conventional simplex optical connector through the reflow process while discussing the glass-transition behavior of the adhesive used in the connector. We then present an improved receptacle structure with glass-based ferrules whose coefficients of thermal expansion are closer to that of the fiber compared to the conventional zirconia ferrule. We demonstrate through testing that our proposed receptacle results in a dramatic decrease of permanent fiber withdrawals after the reflow process. The proposed connector, which is composed of a glass-ceramic ferrule, a polyimide tube, and a mechanical clip, achieved physical-contact connection and maintained satisfactory connection and return losses of below 0.3 dB and over 45 dB, respectively, even after six reflow processes. We examined the withdrawal behaviors for both the zirconia and the glass-ceramic ferrules during reflow based on the online measurement of connection and return losses, and observed the multiple reflections caused by the change in the air-gap width between the mated connectors. We also confirmed that the developed simplex optical connectors based on the glass-ceramic ferrule yielded sufficient environmental durability even after multiple reflow processes.

Free Flap Reconstruction in Patients with Traumatic Injury of the Forefoot

Many techniques have been developed for reconstruction of the hand; however, less attention has been paid to foot reconstruction techniques. In particular, reconstruction of the forefoot and big toe has been considered a minor procedure despite the importance of these body parts for standing and walking. Most of the weight load on the foot is concentrated on the forefoot and big toe, whereas the other toes have a minor role in weight bearing. Moreover, the forefoot and big toe are important for maintaining balance and supporting the body when changing directions. Recently, attention has been focused on the aesthetic appearance and functional aspects of the body, which are important considerations in the field of reconstructive surgery. In patients for whom flap reconstruction in the forefoot and big toe is planned, clinicians should pay close attention to f lap survival as well as functional and cosmetic outcomes of surgery. In particular, it is important to assess the ability of the flap to withstand functional weight bearing and maintain sufficient durability under shearing force. Recovery of protective sensation in the forefoot area can reduce the risk of flap loss and promote rapid rehabilitation and functional recovery. Here, we report our experience with two cases of successful reconstruction of the forefoot and big toe with a sensate anterolateral thigh flap, with a review of the relevant literature.

About the Necessity to Consider Membrane Electrolyte Degradation Statistically

One key factor for the commercialization of fuel cell vehicles is a sufficient membrane durability. In this context, car manufactures work on reliability accelerated stress test procedures (AST) to measure membrane lifetime. There have been many lifetime investigations for polymer electrolyte membrane fuel cells (PEMFCs) especially for the perfluorinated sulfonic acid (PFSA) membrane [1-3]. For comparison of membrane lifetimes, it is necessary to ensure reproducibility of the experimental lifetime data. However, in part of the literature lifetime of membranes was derived from few repetitions – if not none – of single cell experiments only [e.g. 3-5]. Random failures due to membrane production variations, cell assembly inaccuracies and statistical defects cannot be quantified without statistical analysis. Accordingly, some conclusions in literature might have been blurred due to insufficient repetition of measurements. In this work, we stress the necessity to generate statistically relevant membrane degradation data. The development of the open circuit voltage (OCV) and the H2-crossover current (iH2) is shown in Figs. 1-2 for one specific AST and nine cells. It can be seen, that in the range of reproducibility lifetime can be 1000 or 20000 cycles. At the conference more evidence for the wide nature of the lifetime distribution will be presented. Accordingly, the distribution in voltage loss and hydrogen crossover development cannot be neglected if clear conclusions about membrane life shall be derived. Without a high number of repetitions the statistical significance is not assured. Some of the recent conclusions in literature about impact on membrane lifetime will be considered critically from this point of view.

(Invited) Recent Advances in Electrocatalysts for the Oxygen Reduction Reaction Comprising a Hierarchical Graphene-Based “Core” and a Carbon Nitride “Shell” with a Low Loading of Platinum

The paradigm shift in today’s energy harnessing, distribution and utilization is leading to massive investments in innovative technologies, that include electrochemical energy conversion and storage systems (EECS) [1, 2]. The latter exhibit a number of very attractive features, that include negligible emissions of greenhouse gases at the point of operation, a facile scalability and the independence from geographical constrains. Furthermore, EECS are typically characterized by a very high efficiency, as they are not constrained by the limits associated to Carnot’s engines [3]. A broad range of EECS are available, each well-suited for a particular family of applications. In this panorama, the incidence and relevance of proton-exchange membrane fuel cells (PEMFCs) is progressively rising. State-of-the-art PEMFCs have exited the research laboratories and are currently implemented in early products, that include both stationary systems (e.g., power plants for “zero-emission” houses) and light-duty vehicles. Despite these successes, PEMFCs still suffer from several drawbacks. In particular: (i) the performance and the durability of the functional materials involved in PEMFC operation must be increased to match the requirements set by the applications; and (ii) at the same time, the costs must be curtailed to warrant a large-scale market penetration of PEMFCs and leverage the latter’s advantages over competing traditional technologies. One key issue affecting both development areas is the electrocatalyst (EC) that promotes the oxygen reduction reaction (ORR) at the PEMFC cathode. Indeed, to bestow the PEMFC a sufficient performance and durability, state-of-the-art ECs for the ORR must include a very high loading of platinum. Thus, to mitigate the risk to incur in supply bottlenecks [4], new and improved ECs with a low-loading of Pt (“low-Pt”) must be developed. An innovative approach to obtain advanced low-Pt ECs for the ORR exhibiting a performance and durability beyond the state of the art is to devise systems where the active sites are located on the surface of PtMx sub-nanometric clusters (SNCs). PtMx are alloys between Pt and a first-row transition metal (e.g., Ni, Cu), that acts as a “co-catalyst” and promotes the intrinsic ORR kinetics reaching levels that are well beyond the Pt baseline [5]. SNCs offer important advantages over the Pt nanoparticles (NPs) used in conventional ECs for the ORR. In particular, with respect to Pt NPs, in SNCs the utilization of Pt atoms is raised by up to ca. one order of magnitude. This allows for the maximization of the Pt availability for electrocatalytic purposes. Hence, the PEMFCs mounting the low-Pt ECs comprising the SNCs can achieve a specific power that is significantly larger than the 8 kW/gPt target set by the DoE for 2020 [6]. In the proposed ECs the SNCs are located on the surface of a support that exhibits unique features. In detail, the support is based on a “core” consisting of a combination of highly defected graphene nanoplatelets and carbon black NPs [7]. Such hierarchical graphene-based (H-GR) “core” is covered by a carbon nitride (CN) “shell”, that is able to stabilize effectively the SNCs by means of “coordination nests” consisting of C- and N- ligands. The present contribution compares the proposed low-Pt ECs with the state of the art and overviews the complex correlations that are established between: the physicochemical properties of the low-Pt ECs (e.g., chemical composition, morphology and structure of both the active sites and of the support); the electrochemical performance, the reaction mechanism and the durability in the ORR; and finally the characteristic curve of the PEMFC mounting the proposed ECs as tested in operating conditions. The information thus obtained is then used to identify the most promising research approaches to pursue in order to devise next-generation low-Pt ORR ECs able to comply with the stringent requirements of tomorrow’s PEMFCs. Acknowledgement This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 785219, and from the BIRD 2018 program of UNIPD. Figure 1

Results from Laboratory Tests of New Electric Brake Prototype

Abstract The main idea of this article was to compare the results of new design electric brake to the older version of hydraulic brake in laboratory tests. The energy of braking should be very similar due to the same mass of the airplane. That is why the laboratory tests of both brakes were took place in the same stand. Of course, the parameters were similar but not at all. The main idea was to create the solution, which could be used in vehicle like airplane. The electric brakes could replace traditional hydraulic brake solution. The results could be interesting for every researcher who is interested in brakes. Other important idea of this article was to describe the tests of new electric brake prototype. The purpose of the tests was to check designing of electric brakes. The electric brake prototype should ensure sufficient efficiency, safety, reliability and durability during braking, which is required in certification processes and is particularly important when researching innovative solutions. It was really important to verify the design and check the parameters. Of course, there is really important to remember that in every new type of the prototype solutions there are many pros and cons, which are typical only for considered design. Nowadays every electric brake design is different because there is a lot of new concept.

A measurement and evaluation method for wheel-rail contact forces and axle stresses of high-speed train

A high-speed wheelset was instrumented on axle and on wheels with strain gauges and that signals were acquired by radio telemetry systems. The instrumented wheelset being developed went through a special calibration procedure that utilized a wheelset roller rig on which known load time histories were applied generating running conditions similar those encountered in service and providing a more real condition to perform the calibration process. The calibration of the measuring system was improved by following a minimization approach to estimate the optimal transfer function between the strain measurements and the wheel/rail contact forces. A field test was performed on high speed lines and the measurements integrated contact loads and stresses results with GPS information. A specific program was prepared for data processing to obtain load spectra. The developed system has been verified to assure sufficient durability for continuous measurement on in-service trains and sufficient accuracy after various stand tests.

Washing Durability and Photo-Stability of NanoTiO2-SiO2 Coatings Exhausted onto Cotton and Cotton/Polyester Fabrics

The purpose of this study was to assess and compare the durability of TiO2-SiO2 coatings applied in three concentrations onto two lightweight cellulose-based fabrics diverse in the composition against two external factors, repeated washings and prolonged intensive UV irradiation, by observing the changes in surface morphology, investigation of optical properties, and identification of specific molecular vibrations. The scanning electron microscopy (SEM) micrographs, diffuse reflectance spectroscopy (DRS) profiles and fourier transform-infrared (FT-IR) spectra implied equal distribution of TiO2-SiO2 nanoparticles over the surfaces of both fabrics after exhaustion procedures, regarding the concentration of colloidal paste and the type of material used, followed by a slight reduction of nanoparticles after twenty washing cycles. Moreover, the newly gained, good to very good UV protective functionality proved the suitability of the employed procedure and the sufficient durability of the selected coatings. Additionally, UV irradiation mainly caused damages to the cotton. Cotton/polyester became yellower under UV, although the application of TiO2-SiO2 protected the material against yellowness.

Material characterization to assess effectiveness of surface treatment to prevent joint deterioration from oxychloride formation mechanism

Joints in a rigid pavement can act as local reservoirs trapping deicing salts and moisture. Such a harsh micro-environment can impact the durability of sawn joint surfaces, resulting in premature distress even in cases where the bulk of pavement exhibits sufficient durability against frost action and chemical attack by deicing salts. A comprehensive experimental program was undertaken in this study to elucidate the mechanisms of deterioration of concrete exposed to de-icing salts. Plain cement paste samples cast with water-to-cement ratio of 0.40 were exposed to salt solutions prepared with 4% and 20% concentrations of CaCl2 and MgCl2 at 4 °C. A second series of paste specimens, treated with a wide range of sealers representing various generic types, were also exposed to the aforementioned salt solutions. Mechanisms of deterioration and formation of chemical compositions and phases were monitored at different exposure periods using X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Moreover, concrete specimens were cast and treated with the same sealers to expand the fundamental observations from paste to concrete phase.Data obtained from plain cement paste specimens indicated no sign of calcium or magnesium oxychloride formation when exposed to 4% concentration of salt solutions, while oxychloride formation was detected at 20% concentrations. Potential for calcium oxychloride formation in sealed samples correlated well with paste expansion and visual concrete deterioration rates. Results indicated that an expansion threshold of 0.20 mm corresponded to the recommended threshold of oxychloride formation potential of 15 g per 100 g of paste (gOXY/gPaste).

Vibration energy harvesting technology for smart tire monitoring

A smart tire monitoring system uses tire information, such as temperature, pressure, acceleration, force, tire-road friction coefficient, in real time to monitor the driving safety of cars. A vibration energy harvester for a smart tire monitoring system converts the tire dynamic strain energy into electrical energy which is the power source of the wireless sensor module. The self-powered wireless sensor module consists of an electro-magnetic type energy harvester, a power conversion circuit, an acceleration sensor and a radio communication circuit. This research is focused on achieving high energy conversion efficiency, lightweight design, and long durability of the harvester because it is located at the inner surface of tire where extremely high pressure and acceleration exist. The energy harvester was made in a cylindrical shape with a length of 35 mm. The manufactured harvester was 9.4 g, the casing 10.8 g, the battery 2.6 g, the wireless acceleration sensor module 1.1 g, and the power conversion circuit module 1.2 g. So, the total weight of the wireless sensor module was less than 27 g. The monitoring system receives an acceleration signal from the wireless sensor module which is attached to the inner surface of a tire. An operating test of the monitoring system was carried out by using the tire driving test equipment. The average output power of the energy harvester was measured as about 5.7 mW at 60 km/h. The wireless sensor module was operated during about 11700 km (60 km / h * 6.5 h / day * 30 day). The test results showed that the energy harvester has sufficient power to maintain the operation of the wireless sensor module, and the sensor module has a sufficient durability.

Modified PDMS packaging of sensory e-textile circuit microsystems for improved robustness with washing

Electronic Textiles (e-textiles) should ideally be handled and cleaned like traditional textiles. Therefore, we can expect e-textiles to be machine washed or hand washed. As e-textiles enhance traditional fabrics with electronic functionality, any embedded microsystem i.e., flexible electronic circuits, will be expected to survive and show functionality after the e-textile has been washed multiple times to ensure the garment is practical. Therefore, the choice of encapsulation material for microsystems in a textile must be hydrophobic and offer minimal expansion when washed and ensure the electronics are undetectable when the textile is handled or cleaned. This paper evaluates five different base/curing agent mixing ratios—5:1, 7:1, 10:1, 15:1, and 20:1—of commercial polydimethylsiloxane (PDMS) as an electronic packaging encapsulation. Contact angle and aqueous permeability experiments were conducted to tailor the PDMS mixture specifically for washable e-textile applications. The experimental results show that 20:1 PDMS is the most suitable as it is sufficiently hydrophobic with minimal swelling in commercial washing machine trials. Following this, a 40.3 µm-thick 20:1 conformal encapsulation of PDMS upon an touch and proximity flexible circuit that can be integrated into textiles via knitting and/or weaving, was examined. Results show the washing spin speed is a crucial factor with washing cycle duration having minimal impact when determining circuit functionality survival. Overall, the e-textiles in this work survived between 10 and 15 washes with microscopic inspection of the circuits revealing failure of the external wires but not the PDMS encapsulation—suggesting its sufficient robustness and durability as a suitable encapsulation material for washable electronic textiles.

Oxide Layer Rumpling Control Technology for High Efficiency of Eco-Friendly Combined-Cycle Power Generation System

Combined-cycle power generation is a high-efficiency power generation method using natural gas that can reduce the emissions of carbon dioxide and other harmful substances by increasing the power generation efficiency. Therefore, the turbine inlet temperature should be increased to improve the power generation efficiency. However, given that the operating environment becomes extreme as the turbine inlet temperature increases, ensuring the sufficient durability of the gas turbine components is a necessity. Thermal barrier coatings (TBCs) applied to ensure the durability of the gas turbine components in a high temperature environment can peel off by stress generated through the difference in the thermal expansion coefficient of each layer. Because internal gas turbine components are damaged if peeling occurs, it is essential to ensure sufficient durability of the TBC. In particular, to enhance the efficiency of the combined-cycle power plant, and to withstand higher operating temperatures, it is essential to develop a TBC with an improved durability performance, when compared with currently commercialized TBCs. In this study, we attempted to improve the durability of the TBCs by mitigating the stress concentration phenomenon by gently controlling the rumpling of the oxide layer. For this purpose, the vertical crack design conditions required to reduce the buckling stress were derived through a finite element analysis. Isothermal degradation and thermal fatigue tests were conducted on the fabricated specimens to verify whether the oxide layer rumpling of the designed TBC was controlled gently and whether the durability was improved. Base on the results, a TBC structure with improved durability using oxide layer rumpling control technology is proposed.