| 1. |
- Bellippady, Madhura, et al.
(författare)
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Characteristics and performance of suspension plasma sprayed thermal barrier coatings on additively manufactured superalloy substrates
- 2023
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Ingår i: Surface and Coatings Technology. - : Elsevier. - 0257-8972. ; 472
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Tidskriftsartikel (refereegranskat)abstract
- The complex-shaped hot-section parts of new-generation turbine engines demand unique design solutions. Additive Manufacturing (AM) is an emergent production method that can produce metallic parts with complex geometries and minimal material wastage. In this work, the characteristics and performance behavior of Thermal Barrier Coatings (TBCs) deposited on forged and AM-built HAYNES®282® superalloy substrates were studied and compared. The bond coats were produced by High-Velocity Air-Fuel (HVAF) spraying using NiCoCrAlY powder feedstock and TBC top-coats by Suspension Plasma Spraying (SPS) using water- and ethanol-based suspensions of Yttria-Stabilized Zirconia (YSZ). The microstructural features, adhesion, Thermal Cycling Fatigue (TCF) lifetime, and thermal shock lifetimes of the TBCs were comprehensively investigated. The results showed that the deposition of bond coats reduced the roughness and asperities of the AM-built substrates. Depending on the type of suspension used and the spray parameters employed, the TBCs exhibited vertically cracked and columnar microstructures. However, no significant differences in TCF and thermal shock lifetimes of TBCs on AM and forged substrates were observed. It is demonstrated that TBC systems can be produced on AM-built metallic substrates, and the resulting TBCs can have similar microstructures and properties as TBCs deposited on conventional substrates.
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| 2. |
- Bellippady, Madhura, et al.
(författare)
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Performance of Atmospheric Plasma-Sprayed Thermal Barrier Coatings on Additively Manufactured Super Alloy Substrates
- 2024
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Ingår i: Coatings. - : MDPI. - 2079-6412. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- This work represents a preliminary study of atmospheric plasma-sprayed (APS) YttriaStabilized Zirconia (YSZ)-based thermal barrier coatings (TBCs) deposited on forged and additivemanufactured (AM) HAYNES®282® (H282) superalloy substrates. The effect of different feedstockmorphologies and spray gun designs with radial and axial injection on APS-deposited YSZ layercharacteristics such as microstructure, porosity content, roughness, etc., has been investigated. Theperformance of TBCs in terms of thermal cycling fatigue (TCF) lifetime and erosion behaviour werealso comprehensively investigated. In view of the high surface roughness of as-built AM surfacescompared to forged substrates, two different types of NiCoCrAlY bond coats were examined: oneinvolved high-velocity air fuel (HVAF) spraying of a finer powder, and the other involved APSdeposition of a coarser feedstock. Despite the process and feedstock differences, the above two routesyielded comparable bond coat surface roughness on both types of substrates. Variation in porositylevel in the APS topcoat was observed when deposited using different YSZ feedstock powdersemploying axial or radial injection. However, the resultant TBCs on AM-derived substrates wereobserved to possess similar microstructures and functional properties as TBCs deposited on reference(forged) substrates for any given YSZ deposition process and feedstock.
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| 3. |
- Frykholm, Peter, 1961-, et al.
(författare)
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Pre-operative fasting in children : A guideline from the European Society of Anaesthesiology and Intensive Care
- 2022
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Ingår i: European Journal of Anaesthesiology. - : European Society of Anaesthesiology and Intensive Care. - 0265-0215 .- 1365-2346. ; 39:1, s. 4-25
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Tidskriftsartikel (refereegranskat)abstract
- Current paediatric anaesthetic fasting guidelines have recommended conservative fasting regimes for many years and have not altered much in the last decades. Recent publications have employed more liberal fasting regimes with no evidence of increased aspiration or regurgitation rates. In this first solely paediatric European Society of Anaesthesiology and Intensive Care (ESAIC) pre-operative fasting guideline, we aim to present aggregated and evidence-based summary recommendations to assist clinicians, healthcare providers, patients and parents.We identified six main topics for the literature search: studies comparing liberal with conservative regimens; impact of food composition; impact of comorbidity; the use of gastric ultrasound as a clinical tool; validation of gastric ultrasound for gastric content and gastric emptying studies; and early postoperative feeding. The literature search was performed by a professional librarian in collaboration with the ESAIC task force.Recommendations for reducing clear fluid fasting to 1 h, reducing breast milk fasting to 3 h, and allowing early postoperative feeding were the main results, with GRADE 1C or 1B evidence. The available evidence suggests that gastric ultrasound may be useful for clinical decision-making, and that allowing a ‘light breakfast’ may be well tolerated if the intake is well controlled. More research is needed in these areas as well as evaluation of how specific patient or treatment-related factors influence gastric emptying.
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| 4. |
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| 5. |
- Frykholm, Robert, 1970
(författare)
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Development of Composition Gradients in Cemented Carbides
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the formation of tough surface zones, depleted of cubic carbo-nitrides, in cemented carbides. Several materials with varied phase compositions, binder phase volume fraction, and carbon content have been investigated. The main experimental techniques that have been used are scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and atom probe field ion microscopy (APFIM). Some of the experimental results have been compared to computer simulations based on thermodynamics and diffusion. Good agreement between computer simulations and experimental results of the distribution of elements and phases was found. It was therefore concluded that the formation of surface zones is a process controlled by thermodynamics and diffusion. It was investigated how the gradient surface zone formation depends on cubic phase composition. Addition of Ta to the cubic phase was found to decrease the elemental variations in the gradient profile and to give a thinner surface zone. Addition of Nb gave the opposite effect, with larger elemental variations and a wider surface zone. The effect of the binder phase volume fraction on gradient zone formation was studied. It was found that the zone width is directly proportional to the binder content. It was also found that the diffusivity is reduced with a factor equal to the binder volume fraction due to the presence of dispersed phases, i.e. carbides and carbo-nitrides. Study of materials with varied carbon content showed that with a high C content the driving force for gradient formation becomes stronger, and wider surface zones are formed. The effect of high C content was found to be reduced if Ta or Nb was added to the cubic phase. Methods to prepare APFIM specimens of near surface regions were developed. The methods are based on dimple grinding, electropolishing, and focused ion beam milling (FIB). The methods allow for positioning of APFIM specimens with high accuracy in the material, and to re-sharpen analysed specimens. Analysis was performed of the cubic phase just inside the zone border and the results could be related to the sintering process.
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| 6. |
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| 7. |
- Leiter, Robert, et al.
(författare)
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Comparison of superimposed high-frequency jet ventilation with conventional jet ventilation for laryngeal surgery
- 2012
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Ingår i: British Journal of Anaesthesia. - : Elsevier BV. - 0007-0912 .- 1471-6771. ; 108:4, s. 690-697
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundNew ventilators have simplified the use of supraglottic superimposed high-frequency jet ventilation (SHFJVSG), but it has not been systematically compared with other modes of jet ventilation (JV) in humans. We sought to investigate whether SHFJVSG would provide more effective ventilation compared with single-frequency JV techniques.MethodsA total of 16 patients undergoing minor laryngeal surgery under general anaesthesia were included. In each patient, four different JV techniques were applied in random order for 10-min periods: SHFJVSG, supraglottic normal frequency (NFJVSG), supraglottic high frequency (HFJVSG), and infraglottic high-frequency jet ventilation (HFJVIG).Chest wall volume variations were continuously measured with opto-electronic plethysmography (OEP), intratracheal pressure was recorded and blood gases were measured.ResultsChest wall volumes were normalized to NFJVSG end-expiratory level. The increase in end-expiratory chest wall volume (EEVCW) was 239 (196) ml during SHFJVSG (P<0.05 compared with NFJVSG). EEVCW was 148 (145) and 44 (106) ml during HFJVSG and HFJVIG, respectively (P<0.05 compared with SHFJVSG). Tidal volume (VT) during SHFJVSG was 269 (149) ml. VT was 229 (169) ml (P=1.00 compared with SHFJVSG), 145 (50) ml (P<0.05), and 110 (33) ml (P<0.01) during NFJVSG, HFJVSG, and HFJVIG, respectively.Intratracheal pressures corresponded well to changes in both EEVCW and VT. All JV modes resulted in adequate oxygenation. However, PACO2was lowest during HFJVSG [4.3 (1.3) kPa; P<0.01 compared with SHFJVSG].ConclusionSHFJVSG was associated with increased EEVCW and VT compared with the three other investigated JV modes. All four modes provided adequate ventilation and oxygenation, and thus can be used for uncomplicated laryngeal surgery in healthy patients with limited airway obstruction.
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| 8. |
- Lo Mauro, Antonella, et al.
(författare)
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Comparison of different methods for lung immobilization in an animal model
- 2020
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 150, s. 151-158
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Respiratory-induced motion introduces uncertainties in the delivery of dose in radiotherapy treatments. Various methods are used clinically, e.g. breath-holding, while there is limited experience with other methods such as apneic oxygenation and high frequency jet ventilation (HFJV). This study aims to compare the latter approaches for lung immobilization and their clinical impact on gas exchange in an animal model.MATERIALS AND METHODS: Two radiopaque tumor surrogate markers (TSM) were placed in the central (cTSM) and peripheral (dTSM) regions of the lungs in 9 anesthetized and muscle relaxed pigs undergoing 3 ventilatory interventions (1) HFJV at rates of 200 (JV200), 300 (JV300) and 400 (JV400) min-1; (2) apnea at continuous positive airway pressure (CPAP) levels of 0, 8 and 16 cmH2O; (3) conventional mechanical ventilation (CMV) as reference mode. cTSM and dTSM were visualized using fluoroscopy and their coordinates were computed. The ventilatory pattern was registered, and oxygen and carbon dioxide (pCO2) partial pressures were measured.RESULTS: The highest range of TSM motion, and ventilation was found during CMV, the lowest during apnea. During HFJV the amount of motion varied inversely with increasing frequency. The reduction of TSM motion at JV300, JV400 and all CPAP levels came at the cost of increased pCO2, however the relatively low frequency of 200 min-1 for HFJV was the only ventilatory setting that enabled adequate CO2 removal.CONCLUSION: In this model, HFJV at 200 min-1 was the best compromise between immobilization and gas exchange for sessions of 10-min duration.
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| 9. |
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| 10. |
- Sütterlin, Robert, et al.
(författare)
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Efficacy of Superimposed High Frequency Jet Ventilation and High Frequency Jet Ventilation in an Animal Model of Tracheal Obstruction
- 2014
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Ingår i: Anesthesiology. - 0003-3022 .- 1528-1175.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundSuperimposed high frequency jet ventilation (SHFJV) and high-frequency jet ventilation (HJFV) are widely used for airway interventions using rigid bronchoscopy. SHFJV was found to provide higher lung volume and better gas exchange than HFJV in unobstructed airways.We hypothesized that, also in the presence of airway obstruction, SHFJV would provide higher lung volumes, better oxygenation and more effective CO2 removal than HFJV.MethodsIn a porcine model, we used a stent with ID 4 mm to create tracheal obstruction. The anesthetized animals (25-31.5kg) were alternately ventilated with SHFJV (low frequency 16min-1, combined with a high frequency fHF) and HFJV (solely fHF) at a set of different fHF from 50-600min-1. Chest wall volume changes were measured with opto-electronic plethysmography, airway pressures were registered continuously and arterial blood gases were obtained repeatedly.ResultsSHFJV provided higher ∆EEVCW than HFJV with a difference between both modes of 129 ml (fHF=50min-1) to 62 ml (fHF=400min-1). Tidal volume (VT) was always greater than 213 ml with SHFJV, but with HFJV, increasing fHF reduced VT from 112 (97-130) ml at fHF=50 min-1 to negligible values at fHF>150 min-1.In analogy, SHFJV provided paO2 of >30 kPa and acceptable CO2 removal for all fHF, whereas fHF>150 min-1 resulted in severe hypoxia and hypercarbia during HFJV.ConclusionSHFJV effectively increased lung volumes and maintained gas exchange compared with HFJV. SHFJV may be a safer option than HFJV in laser surgery, where low FiO2 is required. HFJV with frequencies >100-150 min-1 should not be used in severe airway obstruction.
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