bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital Contemplative Community in Pandemic Times
Authors: Torres Lisette E.
Published: July 2021

In this collage, I reflect on my Radical Dharma community gatherings and examine how they are helping me to (re)imagine community and connection during pandemic times. Using the theoretical frameworks of Critical Race Theory (CRT) (Delgado & Stefancic, 2001) and Dis/ability Critical Race Studies (DisCrit) (Annamma, Connor, & Ferri, 2013), I explore through my artwork the following questions: How is COVID-19 changing the way I, as a disabled Latina mother-scholar, relate to others in person and over digital space? Is physical distancing creating more social isolation and separation? Or is it paradoxically making me more attune to the pain, needs, and wants of my fellow beings on this planet? How does this ultimately impact my scholarship? Through the use of meditation, journaling, and reflecting on our virtual meetings, I tried to express within the collage our coming to terms with change and grief within the context of the pandemic and the current Black Lives Matter (BLM) protests on police brutality. I argue that we are in the midst of creating a virtual fugitive space (Stovall, 2015), where we can (re)imagine what community can look like post-pandemic through embodied contemplative practice and collective care (Piepzna-Samarasinha, 2018). We are using computer-mediated technology (e.g., Zoom, Slack, Teamwork Projects) to not only work on community mending (Ortiz, 2018) for communities of color, but also their (and our) liberation.
Deep Mediatization during COVID-19: An Interview with Professor Andreas Hepp, University of Bremen
Authors: Kumar Putta Santhosh , Anderson Bissie
Published: July 2021

An Interview with Professor Andreas Hepp, University of Bremen
jurnal HTN_Ismail_156
Authors: Ismail
Published: July 2021

Sebagai lembaga penafsir tunggal konstitusi, banyak hal dalam mengadili menimbulkan akibat terhadap kekuasaan lain dalam kedudukan berhadap-hadapan, terutama terhadap lembaga legislatif di mana produknya direview. Kedudukan Mahkamah Konstitusi dalam sistem ketatanegaraan Indonesia adalah sebagai lembaga negara yang menjalankan fungsi yudisial dengan kompetensi obyek perkara ketatanegaraan.
HUKUM TATANEGARA (KEWARGANEGARAAN GANDA DALAM KEWENANGAN MAHKAMA KONSTITUSI)
Authors: RUSLAN AHMAD RIFALDI
Published: July 2021

Di indonesa pengaturan mengenai kewarganegaraan indonesia selain terdapat dalam konstitusi juga diatur di peraturan perundang-undangan di bawahnya. Pada dasarnya UU No. 12 Tahun 2006 tidak mengenal kewarganegaraan ganda dengan dianutnya asas kewarganegaraan tunggal oleh undang-undang ini. Sedangkan penggandaan kewarganegaraan pada praktiknya selain status citizenship by blood seperti yang berlaku di Indonesia, Guru Besar FHUI, Jimly asshiddiqie menjelaskan, di dunia internasional setidaknya juga dikenal 3 jenis perolehan kewarganegaraan lainya, pertama status citizenship by brith (berdasarkan tempat kelahiran). Kedua by naturalization, yakni dengan mengajukan aplikasi permohonan kewarganegaraan, Indonesia juga memberlakukan hal ini (lihat pasal 9 uu kewarganegaraan). Ketiga, citizenship by registration atau melalui pendaftaran, seperti berlaku di paris.Tujuan dari penelitian ini ialah, mengenai kewarganegaraan Indonesia yang terdapat dalam konstitusi dan juga di atur di peraturan perundang undangan. Yang pada dasarnya UU No. 12 tahu 2006 tidak mengenal kewarganegaraan ganda dengan dianutnya asas kewarganegaraan tunggal oleh undang-undang. Metode penelitian di pakai yaitu; penelitian Deskriptif ialah jenis penelitian yang mendiskrisikan suatu gejala, peristiwa, atau kejadian yang menjadi pusat perhatia saat itu. Bersadarkan hasil penelitian dan pembahasan maka kasus yang menimpah bupati terpilih sabu raijua mengenai kewarganegaraan ganda. Apabila seorang wni memiliki kewarganegaraan lain, statusnya sebagai WNI akan gugur, karena dalam pasal 23 huruf h UU kewarganegaraan, salah satu hal yang membuat seorang WNI kehilangan kewarganegaraanya adalah karena mempunyai paspor atau surat bersifat paspor dari Negara asing atau surat sebagai tanda kewarganegaraan yang masih berlaku dari Negara lain atas namanya.
Jurnal HTN_A.M. Fauzi Rahmad_149
Authors: RAHMAD_149 A.M.FAUZI
Published: July 2021

Semua petunjuk teknis terkait, yang dikeluarkan oleh KPU sudah dijalankan oleh komisioner KPUSabu Raijua. "Pada saat verifikasi itu, kami kan wajib mengumumkan semua dokumen dan wajib meminta tanggapan masyarakat, tapi tanggapan dan masukan masyarakat itu tidak ada, "kataThomas. Yang ada, lanjut dia, hanya rekomendasi dari Bawa slu Sabu Raijua yang pada intinyamempertanyakan keabsahan KTP yang dimiliki Orient.
HUKUM TATANEGARA
Authors: ALAMSYAH
Published: July 2021

Kekuasaan kehakiman sesudah amandemen UUD Negara RepublikIndonesia Tahun 1945 mengalami perubahan signifikan. UUD NegaraRepublik Indonesia Tahun 1945 di satu sisi telah mampu memberikan jaminantentang kebebasan dan kemandirian kekuasaan kehakiman, namun di sisilain, telah memberikan peluang kepada lembaga lain untuk “mengganggukebebasan dan kemandirian kekuasaan kehakiman”.
Proof of the Goldbach's Conjecture
Authors: Wijesuriya K.H.K. Geerasee
Published: July 2021

Goldbach’s Conjecture states that every even number greater than 3, can be written as a summation of two prime numbers. This conjecture is roughly 300 years old and a very famous unsolved mathematics problem. To prove the Goldbach’s Conjecture, I use the contradiction method in mathematics as below.
Self-medication and experiential avoidance: Using network analysis to understand young adult cannabis use
Authors: Enkema Matthew , Piccirillo Marilyn , Schwebel Frank J , Larimer Mary , Canning Jessica
Published: July 2021

In the United States, cannabis is one of the two most commonly used substances, with the highest rates of use reported during young adulthood. The self-medication theory suggests that cannabis use may be a behavioral response to cope with unwanted mood and emotion. Additional theories under study were the dynamic model of addiction and the paradoxical effects of thought suppression and experiential avoidance. The current study used ecological momentary assessment to evaluate these three theories among young adult college student cannabis users by investigating contemporaneous and temporal links between positive and negative affect, craving, intoxication level, and coping style. Participants (N=86) were students at a large public university in the Pacific Northwest using cannabis two or more days per week, with problems related to cannabis use, and interest in changing their use. During a two-week ecological momentary assessment period, participants completed four daily self-reports. We constructed associative and temporal networks to test each of the three theories during cycles of cannabis use and cycles of cannabis non-use. Results provided evidence to support the dynamic model of addiction, as well as the paradoxical effects of thought suppression and experiential avoidance. However, there was mixed evidence related to the self-medication theory. The expected link between negative affect and level of intoxication was only observed in the contemporaneous model and not in the temporal model. Future research may investigate these theories among those using other substances, with more severe presentations, or greater readiness to change their use.
Combining statistics: The role of phonotactics on cross-situational word learning
Authors: Dal Ben Rodrigo , de Hollanda Souza Débora , Hay Jessica
Published: July 2021

Language learners can rely on phonological and semantic information to learn novel words. Using a cross-situational word learning paradigm, we explored the role of phonotactic probabilities on word learning in ambiguous contexts. Brazilian-Portuguese speaking adults (N = 30) were exposed to two sets of word-object pairs. Words from one set of labels had slightly higher phonotactic probabilities than words from the other set. By tracking co-occurrence of words and objects, participants were able to learn word-object mappings similarly across both sets. Our findings contrast with studies showing a facilitative effect of phonotactic probability on word learning in non-ambiguous contexts.
Psilocybin for Depression: The ACE Model Manual
Authors: Watts Rosalind
Published: July 2021

"The Psilocybin for Depression: The ACE Manual '' describes the structure, procedures, and scripts used in the two Imperial College London studies (Psilodep) researching psilocybin treatment for major depression.
Realistic motion avatars are the future for social interaction in virtual reality
Authors: Rogers Shane L. , Broadbent Rebecca , Brown Jemma , Fraser Alan , Speelman Craig
Published: July 2021

This study evaluated participant self-reported appraisal of social interactions with another person in virtual reality (VR) where their conversational partner was represented by a realistic motion avatar. We use the term realistic motion avatar because: 1. The avatar was modelled to look like the conversational partner it represented, and 2. Full face and body motion capture was utilised so that the avatar mimicked the facial and body language of the conversational partner in real-time. We compared social interaction in VR with face-to-face interaction across two communicative contexts: 1. Getting acquainted conversation, and 2. A structured interview where the participant engaged in self-disclosure about positive and negative experiences. Overall, participants largely indicated they preferred face-to-face over VR communication. However, some participants did indicate a preference for VR communication, and an analysis of post-conversation ratings indicated no significant difference for rated enjoyment, understanding, self-disclosure, comfort, and awkwardness between communication modes. The one rating where face-to-face was found to be superior was for perceived closeness. Most participants perceived frequent eye contact in both face-to-face and VR interaction, but typically more eye contact when face-to-face. Eye contact was positively associated with rated enjoyment, closeness, and comfort. Overall, our findings suggest that harnessing full face and body motion capture can make social interaction in VR very similar to face-to-face interaction. We anticipate that VR social interaction is poised to become the next major technological evolution for human computer mediated communication and suggest avenues for further research.
Dualband Microstrip Elliptic Patch 1x4 MIMO Antenna Design for 5G System Device
Authors: Rahayu Yusnita , Andika Mayo
Published: July 2021

This paper presents a dual-band antenna for the 5G system communication device. The MIMO antenna can potentially boost the capacity and transmission rates to a new level in a communication system. The MIMO 1x4 elliptic circular patch is designed at 24 GHz and 27.8 GHz. From the simulated S11 results, a single patch antenna provides -16.364 dB at 24 GHz and -35.44 dB at 27.86 GHz. While for the MIMO 1x4 patch, the simulated S11 of -15.563 dB and -21.889 dB are achieved at both 24 GHz and 27.8 GHz, respectively. It has a gain value of 9.04 dBi at the 24 GHz and a gain value of 6.56 dBi at the 27.8 GHz. These gains are higher than the gain obtained with a single element.
Tourism, Employment Generation and Foreign Exchange Earnings in Nepal
Authors: Bhattarai Kumar , Upadhyaya Ghanshyam , Bohara Surendra Kumar
Published: July 2021

An activity of travelling has remained one of the leading contributors of global economic activities, particularly, in employment generation and foreign exchange earnings. With the 56-folds growth of international tourist arrivals from 1950 to 2018 globally, Nepalese tourism industry is widening its scope for employment generation and foreign exchange earnings. The aim of this study is to analyze role of tourism on employment generation and foreign exchange earnings in Nepal. For this, a descriptive study design was employed. Analysis was done by using secondary data of the period 2010-2019. Number of tourist arrival in 2019 (1,197,191) was found nearby double compared to the 2010 (602,867), however, the status of average length of stay remained almost same within this period. Data show, on average, that most of the tourists had visited Nepal for holiday celebration (58.6%), followed by trekking and mountaineering (11.2%) and pilgrimage (11.4%). Average annual share of tourism earnings on total export earnings in 2010-2018 was 21.7% whereas share of tourism earnings on total foreign exchange earnings was 6.2%. It is estimated that every 6 tourists visited create 1 employment opportunity in Nepal. Despite the situation of almost double in number of tourist arrival from 2010 to 2019, this study concludes that there was no significant increase in the share of tourism in total foreign exchange earnings and total employment in Nepal.
The Effects and Challenges of COVID-19 in the Hospitality and Tourism Sector in India
Authors: Gautam Prakash
Published: July 2021

The hospitality and tourism sector is considered the backbone for economicgrowth, especially in developing countries. However, this thriving sector is particularly vulnerable to naturaland human-made disasters. This study assesses the impact of the COVID-19 (coronavirus disease-2019) pandemic in India’s hospitality and tourism sector by addressing essential aspects such as current conditions and challenges as well as future perspectives. The secondary research methodology has been applied for the research. For data collection, the secondary data has been collected through literature, journal articles, government documents, etc. The research findings show that COVID-19 in India has significantly affected the hospitality and tourism sector. Global and domestic tourists have canceled their programs to visit the natural, historical, religious, and cultural sites. The flight tickets and the hotel reservations have been canceled. A significant number of workers in the sector have lost their jobs. This pandemic has affected the economy of the country as well as the well-being of the individuals to a large extent. As the intensification of the COVID-19 is being thought to cause a long-term impact, this study could be relevant to the decision-makers in regards to the crucial task of reviving the sector.
Body-mapping based on thermographic measurements under different influencing factors
Authors: Salopek ČUbrić Ivana , Čubrić Goran
Published: July 2021

The presented research focuses on the use of thermography to observe influences of different influencing factors on the changes of lower body temperatures. Based on the outcomes of the research fit of garment plays an important role for the retention of heat between the textile material and skin, especially in the zone of both upper and lower shin. Also only tight model of trousers is capable to preserve the temperature in zones of thigh and knees of male volunteer. The given body-maps present differences in values of average temperatures (ΔT) considering the garment fit. In the indoor environment, tight model of female trousers has significant influence on the average temperature in the zone of upper shin. This observation is even more pronounced in the outdoor environment. For the male volunteer, higher differences, between temperatures are seen in the outdoor environment only.
Anode Boundary Layer Effects in Plasma Spray Torches
Authors: Duan Z. , Heberlein J.
Published: July 2021

The control over coating quality in plasma spraying is partly dependent on the arc and jet instabilities of the plasma torch. Different forms of instabilities have been observed with different effects on the coating quality. We report on an investigation of these instabilities based on high-speed end-on observation of the arc. The framing rate of 40,500 frames per second has allowed the visualization of the anode attachment movement and the determination of the thickness of the cold gas boundary layer surrounding the arc. The images have been synchronized with voltage traces. Data have been obtained for a range of arc currents, mass flow rates, for different gas injectors and for anodes displaying different amounts of wear. The analysis of the data has led to quantitative correlations between the cold gas boundary layer thickness and the instability mode for the range of operating parameters. The arc instabilities can be seen to enhance the plasma jet instabilities and the cold gas entrainment. These results are particular useful for guiding plasma torch design and operation to minimize the influence of plasma jet instabilities on coating properties.
Diagnostics and Applications of an Innovative Plasma Torch Generating a Broad Plasma Jet
Authors: Hartmann R. , Landes K.D.
Published: July 2021

Conventional DC plasma torch designs lead to a circular cross-section of the emanating plasma jet. Consequently in surface treatment applications the plasma jet hits the substrate within a limited circular working area. Large scale workpieces therefore have to be scanned resulting in a time-consuming procedure. The innovative DC plasma torch system LARGE is characterized by the arrangement of the anode and the cathode opposite to each other on a common axis with a variable distance. The central body of the torch between the electrodes is divided into electrically insulated cascade plates. The plasma gas is injected perpendicular to the torch axis. Passing through the arc, the gas is transferred to the plasma state and leaves the torch laterally through a slit as a plasma jet with extended stripe width. The plasma torch LARGE is investigated by electrical, optical and enthalpy probe diagnostics. Shrouding the electrodes with an inert gas and feeding reactive gas mixtures as main plasma gas allow the torch to be used for plasma chemical reactions, too. Preliminary applications focus on preheating, surface modification of paper and plastic materials as well as on sterilization of nutrition packaging. The capability of plasma enhanced CVD is examined experimentally.
Influence of Plasma Spraying Parameters on Coating Damage
Authors: Bianchi L. , Baradel N. , Llorca-Isern N. , Bertran-Vidai G.
Published: July 2021

The influence of plasma spraying parameters on the mechanical properties of coatings has been studied. ZrO2-Y2O3 coatings were sprayed onto stainless steel and aluminium substrates at temperatures of about 75°C and 225°C. An original set of samples, facilitating the measurement of substrate deflection, was used to evaluate the effect of thermal cycling under different spraying conditions. In order to correlate thermal cycling values and mechanical properties to coating microstructure, the coatings were impregnated with low-viscosity resin and examined under a confocal microscope. The results reveal the influence of spraying temperature, substrate properties, and torch-substrate velocity on coating damage.
Study of the Air Entrainment Within dc Plasma Jets
Authors: Lagnoux O. , Coudert J.F. , Wittmann K. , Fauchais P.
Published: July 2021

Air entrainment in the first 30 mm of a dc Ar/ H2 plasma jet has been studied by emission spectroscopy. The tests were conducted using 6, 7 and 10-mm diameter nozzles and plasma arc currents of 400 and 600 A. Oxygen, nitrogen, and argon spectral lines were recorded 20 and 30 mm downstream of the nozzle exit during spraying, and the corresponding atom density ratios were estimated based on plasma population temperature and volumetric emission coefficients. The results indicate that at 20 mm air entrainment is mainly due to piston flow for the 10-mm nozzle and both piston flow and engulfment for the 7-mm nozzle. At 30 mm, the engulfment process is found to have 4 to 6 times the impact that it does at 20 mm and is directly linked to the jet velocity. At both locations, the atom density ratios differ from that observed in air due to the time required to dissociate N2.
The Capabilities and Limitations of Pulsed Plasma, Electrical, Chemical Thermal Spray
Authors: Factor M. , Roman I. , Wald S.
Published: July 2021

A new thermal spray technology has been proposed. Called Electrical Chemical Thermal Spray (ETCS), it combines plasma energy with the combustion gases of solid propellants to heat and accelerate particulate materials. The hybrid technology promises new degrees of freedom in materials processing over the conventional thermal spray processes by allowing thermal energy transfer to the particles and particle accelerations to be optimized separately. Experimental coatings were formed using a prototype system made from a converted ½” plasma gun fueled with double-base solid propellants to explore this novel concept. The prototype test-facility equipment was limited to single-shot mode. Examination of the coatings formed, and conceptual analysis by analogy to conventional technologies was used to assess the capabilities and limitations of the hybrid process. Impressive in-flight powder velocities of 1100 m/s were reached, with deposition yield efficiencies of 60 - 85% achieved for WC-Co coatings after first round of optimization. However despite the ability to deposit single-shot carbide and metallic coatings with thickness exceeding 200 µm. chemical degradation and extensive cracking combined to limit attractiveness of coatings as compared to those produced using commercial technologies. Unlike the oxidation effects with atmospheric plasma spray and the various low-velocity flame-spraying technologies, chemical degradation in the prototype ETCS was the result of interaction between the gases produced from the combustion of the propellant and the coating material. It is seen that the organic, nitrocellulose based solid propellants are inherently unsuitable for spraying reactive material. With suitable fuels however, it is believed that the inherent advantages of high throughput, versatility and low labour requirements are such that ETCS will have commercial advantages for the coating of large structures.
Numerical Modeling of Particle Laden Flow in HVOF Torch with Gas Shroud
Authors: Dolatabadi A. , Mostaghimi J. , Ivanovic M.
Published: July 2021

A particle laden flow in an HVOF torch is analyzed using Computational Fluid Dynamics (CFD). The torch is similar to the DJ Metco torch with a converging-diverging (de Laval) nozzle, where particles are injected through the center together with nitrogen as a carrier gas. The Eulerian formulation is used for the gas flow whereas the particle motion is described by using the Lagrangian formulation. The flow turbulence is modeled via k-e model with standard wall functions. For modeling the combustion process in the torch, a multi-reaction Eddy-Dissipation Model (EDM) is employed. The computational domain comprised the torch itself and the region outside the torch where our attention is mainly focused. The computations are performed for the torch with and without the gas shroud attachment. The results showed that the presence of the shroud affected to some degree the flow and temperature fields of the main gas and the particle stream, while at the same time, significantly reducing the entrainment of ambient air into the main stream as shown by the lower oxygen concentrations. The results of the numerical computations are compared with experimental results for the same operating conditions and the agreement is found to be good.
Process Maps for Plasma Spray Part II: Deposition and Properties
Authors: Jiang X. , Matejicek J. , Kulkarni A. , Herman H. , Sampath S. , Gilmore D.L. , Neiser R.A.
Published: July 2021

This is the second paper of a two part series based on an integrated study carried out at the State University of New York at Stony Brook and Sandia National Laboratories. The goal of the study is the fundamental understanding of the plasma-particle interaction, droplet/substrate interaction, deposit formation dynamics and microstructure development as well as the deposit properties. The outcome is science-based relationships, which can be used to link processing to performance. Molybdenum splats and coatings produced at three plasma conditions and three substrate temperatures were characterized. It was found that there is a strong mechanical /thermal interaction between droplet and substrate, which builds up the coating/substrate adhesion. Hardness, thermal conductivity increase, oxygen content and porosity decreases with increase of particle velocity. Increasing deposition temperature resulted in dramatic improvement in coating thermal conductivity and hardness as well as increase in coating oxygen content. Indentation reveals improved fracture resistance for the coatings prepared at higher deposition temperature. Residual stress was significantly affected by deposition temperature, although not to a great extent by particle conditions within the investigated parameter range. Coatings prepared at high deposition temperature with high-energy particles suffered considerably less damage in a wear test. The mechanism behind these changes is discussed within the context relational maps which is under development.
Thermal Shock Testing and Finite Element Modeling of Pre-Oxidized Thermal Barrier Coatings
Authors: Liu Y. , Persson C. , Bengtsson P. , Leger A.C. , Wigren J.
Published: July 2021

To determine the effect of bond coat oxidation on the coating life, thermal shock testing were performed, using three different thermal cycles. The failure mode and crack paths were investigated in scanning electron microscope. A finite element model was developed to simulate the thermal shock tests. First, transient temperature fields during the thermal cycling were calculated. Second, stresses and strains evolving in the coatings due to thermal expansion mismatches and temperature gradients during the cycling were computed. The stress concentration at the interface due to the roughness of the bond coat was accounted for by using an ideal sinusoidal interface in the model. By adding an oxide layer with and without residual stresses to the model, the influence of the bond coat oxidation was determined. Both the experimental and numerical results revealed that the TBC failed by crack initiating in the ceramic top coat very close to the grown oxide layer at the interface followed by coating fatigue failure. Numerical simulation indicated that bond coat oxidation led to stress concentration at the peak of the asperity of the interface proceeding crack growth. It also showed that bond coat inelasticity and ceramic creep might further enhance the crack growth. There was little effect on coating behavior due to the residual stresses in the oxide layer.
Mathematical Model of In-Flight Oxidation of Metallic Particles in Thermal Spraying
Authors: Ahmed A.M. , Rangel R.H. , Sobolev V.V. , Guilemany J.M.
Published: July 2021

This paper presents a mathematical model of the in-flight oxidation of spherical particles during thermal spray deposition process. The model includes analysis of the mechanical and thermal behavior of the powder particles. The former accounts for acceleration and deceleration of the particles at the spray distance under different fluid velocities. The thermal behavior takes into account heating, melting, cooling and possible solidification as the particle travel towards the substrate. A finite-difference method is used to solve the thermal energy conservation equation of the particles. The model includes nonequilibrium calculations of the phase change phenomena in the liquid-solid (mushy) zone. The growth of the oxide layer at the particle surface is represented by a modified boundary condition, which includes finite-rate oxidation. The results obtained give the interrelations between various process parameters and the oxidation phenomenon and agree with experimental observation.
Computer Aided Coating Design
Authors: Wilden J. , Frank H. , Müller T.
Published: July 2021

The crystal structure of the coating depends on the splashing and solidification of the sprayed particles. The splashing of the particles is simulated by commercial software taking temperature dependent parameters like melt viscosity and surface tension into account. This article provides the theoretical background and the experimental verification. The steps of simulation solidification, splashing, and heat and momentum transfer help to develop novel coating systems with defined microstructure and shorten the time to market. Experimental investigations were carried out using Ni and Ni/Cr 80/20 spray powders with a mean particle diameter of about 15 μm. The theoretical investigations to describe the flattening process of a droplet show the influence of particle velocity and temperature. It was shown that different material parameters, as latent heat or surface energy, have a significant influence on the simulation results.
Structure and Adhesion of Ni and Ni-WC Plasma Spray Coatings
Authors: Coyle T.W. , Bahrami A.
Published: July 2021

There is typically a large scatter in the observed failure stress, particularly for ceramic coatings. Failure can thus occur not only at the coating-substrate interface where it is desired but also through the coating, the bonding epoxy, or the epoxy/coating interface. A large number of alternative test configurations have been proposed in an attempt avoid such drawbacks, each with their advantages and disadvantages. A test method developed recently by Troczynski and co-workers, known as the Peel Adhesion Test, is of particular interest for this article. The first specimens examined were Ni-WC coatings applied to 150 micrometer thick 1010 stainless steel foils which were grit blasted in the same manner as a bulk substrate would have been. It was observed that the technique appears to offer the capability of providing a sensitive and reproducible measure of the effects of surface treatments and other deposition parameters on coating adhesion.
Study of Photo-Catalytic Character of Plasma Sprayed TiO2 Coatings
Authors: Ohmori A. , Shoyama H. , Matsusaka S. , Ohashi K. , Moriya K. , Moriya K. , Li C.J.
Published: July 2021

Two types of rutile and anatase powders are used for the deposition of TiO2 coatings. The effects of plasma spraying conditions on the structure of TiO2 coatings are investigated in order to clarify controlling factors of the phase formation and to aim at the development of effective photo-catalyst TiO2. It is found that the amount of anatase TiO2 in the coating is influenced by spray parameters. The decrease of the heat input to spray droplet and an increase in the cooling speed during droplet deposition will increase the amount of the anatase TiO2 in the coating. As a photo-catalyst, the coating deposited under limited plasma power and by HVOF spraying using anatase powder is effective for the decomposition of acetaldehyde gas.
Investigating High Temperature Damping Behavior of Plasma Sprayed Ni-Alloy Coatings
Authors: Khor K.A. , Chia C.T. , Gu Y.W.
Published: July 2021

In recent year, there has been an increasing trend to design the turbine coating together with the substrate. In this harsh environment, a failure in one quickly leads to a failure in the other. Materials that are used in structural applications are prone to mechanical vibration which when not attenuated, will lead to fatigue of components and shortening of life cycle. Therefore, it is not uncommon to find that it is important to understand the thermal stability and dynamic mechanical properties of coatings as well, which will be used in the dynamic conditions. In addition to these essentially noise reduction and vibration amplitude control motivated objectives, however, mechanical energy dissipation processes also find intrinsic applications in cases where a thorough understanding of the mechanisms responsible for the damping response of the material are required. This article describes the damping behavior and mechanisms that exist in plasma sprayed NiCoCrAlY coatings.
Structure and Properties of Plasma-Sprayed Zircon Coating
Authors: Suzuki M. , Sodeoka S. , Inoue T. , Shimosaka K. , Oki S.
Published: July 2021

Effects of spray parameters, such as spray distance, SD, and substrate temperature, Ts, and post heat treatment on the structure and properties of plasma-sprayed zircon coatings were investigated. Zircon was totally decomposed by plasma spray; the coatings were composed of tetragonal zirconia (t-ZrO2) and amorphous silica (a-SiO2), because of the rapid cooling of molten particle right after the impingement to the substrate. Porosity of the as-sprayed coatings was highly affected by both of substrate temperature and spray distance. In all range of the spray distance which had been tried in this study, higher substrate temperature resulted in lower porosity of the coatings; the coating with porosity of 2% was obtained at Ts = 1573K with SD = 95mm. Porosity also decreased with decrease of spray distance. By the heat treatment at 1473K, t-ZrO2 transformed to monoclinic zirconia (m-ZrO2) and a-SiO2 crystallized to cristobalite, respectively. Cracks in the coating disappeared, and open porosity decreased. This can be attributed to sintering of SiO2 and phase transformation of ZrO2. After the heat treatment at 1673K, the coating was composed of ZrSiO4 with dispersed fine m-ZrO2 particle. Open porosity of all the coatings increased up to 10% at this temperature. This is because of volume shrinkage during the formation of zircon.
Characterization of Thermal Spray Coatings Used for Dimensional Restoration
Authors: McGrann R.T.R. , Kim J. , Shadley J.R. , Rybicki E.F. , Ingesten N.-G.
Published: July 2021

Thick thermal spray coatings are used to repair worn parts during aircraft overhaul. The thermal spray coating is used to restore a part to its original dimensions. Characteristics of the as-applied coating that affect the performance of thermal sprayed parts are the residual stress in the coating, the tensile bond strength, the amount of porosity, oxides and impurities near the coating/substrate interface, and the hardness of the coating. An understanding of the relation of these coating characteristics to process variables such as the material used for the coating, spray process, spray angle, and thickness of the applied material is needed. In this paper, four thermal spray coatings, Ni5Al, Ni5Al-atomized, (NiCr)6Al, and Inco 718, on a substrate of Hastelloy X are investigated. These materials are applied using two different thermal spray application processes: plasma spray and High Velocity Oxy-Fuel (HVOF). Spray angles of 90° and 45° are used during spraying. The nominal thickness of the applied coatings ranges from 0.4 mm to 1.8 mm. The thermal spray coatings are evaluated in four types of tests. Residual stresses in the coatings and substrate are evaluated using the modified layer removal method. A tensile bond strength test is performed. Metallographic examination is used to determine the porosity and content of oxides and bond zone impurities (percent) of the applied materials. In addition, the hardness of the coating is measured. For the materials and conditions investigated, it is found that residual stress varies with each of the four process parameters. The bond strength for plasma sprayed coatings is related to the type of material and possibly to the coating thickness. The percent porosity varies with coating material, but, for Ni5Al, it does not depend on application process. Oxide content, as a percentage, varies with material and process, but not with spray angle and thickness. The percentage of impurities near the coating/substrate interface varies with process and, for the specimens that were coated using the HVOF process, with thickness. The hardness of the coating was found to vary with material and spray process. For three of the four coatings, hardness increases with thickness but, for Inco 718, hardness decreases as thickness increases.
Processing Effects on Residual Stress in Ni+5%AI Coatings–Comparison of Different Spraying Methods
Authors: Matejicek J. , Sampath S. , Gnaeupel-Herold T. , Prask H.J.
Published: July 2021

Properties of thermally sprayed coatings, including residual stress, are controlled by various parameters of the spraying process. This study is focused on three thermal spraying techniques with significantly different particle temperatures and velocities. These are plasma spraying, twin wire arc spraying and high velocity oxy-fuel spraying. For each method, in-flight particle diagnostics was performed. Through-thickness residual stress profiles in Ni+5%A1 coatings on steel substrates were determined nondestructively by neutron diffraction. The stresses range from high tensile in the plasma sprayed coating to compressive in the HVOF one. Various stress generation mechanisms, including splat quenching, peening, and thermal mismatch, are discussed with respect to process parameters and material properties.
Analytical Predictions of Thermal Stress in Plasma Spray Coating and in Substrate at Low Temperature Compared with Strains Measurements
Authors: Gassot H.
Published: July 2021

An analytical thermal stress calculation and an in situ thermal stress measurement are developed at low temperatures (from room temperature to liquid helium temperature) on a cylindrical specimen made from an inner bulk niobium wall and a copper alloy VPS coating. This kind of structure is proposed for superconducting cavities in order to reduce the cavity frequency shift due to Lorentz forces. Since the superconducting cavity works at liquid helium temperature (below 4 K) and the niobium thermal expansion ratio is very different from the thermal expansion ratio of copper, thermal stress evaluations during the cool down are necessaries. The experimental approach consists in two series of measurements, the first series of measurements is performed at bulk niobium, bulk copper and thermal sprayed copper since the use of strain gage at liquid helium temperature is unknown from the manufacturer and the behaviour of the strain gage on the copper alloy coating is also unknown, the thermal compensation of strain gage from helium temperature to room temperature is imperative. Then the strain measurements are realized at inner surface (bulk niobium substrate) and outside (copper alloy VPS coating) of the cylindrical specimen. The analytical calculation takes into account non linear thermal expansivities of the materials, the calculated prediction of thermal stress is verified by measurement, a first observation on the copper alloy coating thermal expansion behaviour at low temperatures is established. Key words: thermal spray coating, thermal stress calculation and measurement, liquid helium temperature, superconducting radiofrequency cavities stiffening
Influence of Coating Removal Processes on Residual Stresses of Base Ni Sheet
Authors: Goubot N. , David T. , Baudoin J. , Dhers J. , Ducos M. , Michaud H.
Published: July 2021

Substrates protected by thermal spray coatings are usually found intact after use, making them viable candidates for recycling and reuse. The key is to remove the coating without damaging the component. This requires a process that minimizes the development of residual stresses and the associated distortion. The purpose of this work is to determine the optimal descaling technique for Ni-base sheets with a thermal barrier coating. Test specimens were produced following industry procedures. Thin sheets (<3 mm) of Ni-base superalloy were plasma sprayed with a NiCrAlY bond coat and a Y203-stabilized ZrO2 topcoat. The coating layers were then removed using different methods, including pickling, shot blasting, and water jet descaling, and the substrates were assessed based on X-ray diffraction and chord width measurements. The findings of the study show that water jetting removes all surface materials, particularly the bond coat, without damaging the underlying surface. It also produces the least amount of stress and deformation and is relatively easy to automate.
Variation in Residual Stress Field During Fatigue Failure of Thermal Spray Coatings
Authors: Ahmed R. , Hadfield M. , Tobe S.
Published: July 2021

A non-destructive experimental approach was adapted to investigate the variations in residual stress fields within thermal spray coatings. WC-Co coatings produced by a HVOF technique were considered for concentrated rolling sliding contacts in this study. These coatings were produced in various thicknesses on various substrates. Residual stress measurements were made using an x-ray diffraction technique, along and across the rolling direction. A modified four-ball machine was used to conduct rolling contact fatigue tests under various tribological conditions of contact stress, lubrication and contact configuration. Residual stress measurements were made before and after the tribological tests. Failed rolling elements were analyzed using scanning electron microscopy, electron probe microscopy and surface interferometry. Results indicate that the magnitude of compressive residual stress attenuates during fatigue failure. The magnitude of attenuated residual stress was dependent upon the type of tribological failure. This attenuation of residual stress was attributed to the microcracking of coating under the influence of contact stress.
Properties of TiC-Ni Based Coatings Deposited by Different HVOF Spraying
Authors: Vuoristo P. , Väisänen M. , Mäntylä T. , Berger L.-M.
Published: July 2021

Hardmetal-like coatings of the TiC-Ni system are potential for use as wear, corrosion and heat resistant coatings in various operation conditions. Our previous works [1-12] have shown that these materials are well sprayable using different thermal spray processes such as plasma, D-Gun and HVOF spraying. Since HVOF spraying is today the most important process used to apply carbide based coatings, this study was carried out in order to evaluate more systematically the sprayability of these novel spray powders and the influence of HVOF spray parameters on some coating properties. Coating samples were prepared by using DJ Hybrid gun with propane as a fuel gas, and a CDS gun with hydrogen fuel gas. Oxygen flow rate was varied in both cases for changing the flame temperature. Microstructure, phase composition, hardness, and abrasion wear resistance of the coated samples were investigated. The results showed that both HVOF processes used give satisfactory coating properties and that the use of high oxygen flow rates is beneficial for improving the wear resistance of the coatings. Powders with fine particle size are beneficial in the DJ Hybrid process; the use of coarse powders results in coatings with somewhat higher wear rates. The optimum spray condition for the TiC-Ni system powders differs from that typically used for conventional WC-Co and Cr3C2-NiCr powders by a higher flame temperature.
Effect of Increase in Entrance Convergent Section Length of Gun Nozzle on HVOF Thermal Spray Process and its Application to Nozzle Design for Cold Gas-Dynamic Spray Method
Authors: Sakaki K. , Shimizu Y.
Published: July 2021

Nozzle geometry has a profound effect on HVOF spraying, influencing combustion gas dynamics as well as particle behavior. Nozzle dimensions are also important in cold gas-dynamic spraying (CGDS), particularly the length of the nozzle which affects gas flow temperature and speed. In this study, numerical simulations and experiments were conducted to determine how the length of the entrance convergent section of gun nozzles affects HVOF spraying. Process changes that occur inside the nozzle (as predicted by simulation) were correlated with coating properties. An Al2O3-TiO2 powder was used for the experimental studies. Changes in nozzle length had a significant impact on deposition efficiency, microstructure, hardness, and particle velocity. These relationships (as measured and calculated) were then applied to the nozzle design for the CGDS method.
Characterizaton of Plasma Sprayed Aluminum-Beryllium for Aerospace and Space Application
Authors: Castro R.G. , Thoma D.J. , Vaidya R.U. , Field R.D.
Published: July 2021

There is a continued need within the aerospace and space communities to increase the structural efficiency of launch vehicles in order to increase the payload and/or lower fuel usage. Many of these structures have critical stiffness demands because of deflection, buckling, or acoustic/vibration damping. Aluminum-beryllium (Al-Be) is a candidate material for many such structural components because it has a very high stiffness to weight ratio (second only to pure beryllium) and has superior formability and weldability as compared to beryllium. The strength to weight ratio of commercial Al-Be is superior to aluminum alloys (7050 and 6061-T6) that are currently used for aerospace and space applications. Plasma spray forming of Al-Be alloys is being investigated at Los Alamos National Laboratory for producing axial symmetric components for aerospace and space applications. Plasma spray forming of beryllium and beryllium alloys was investigated during the 1960's and 70's by Union Carbide Speedway Laboratories and the Atomic Weapons Establishment for producing axial symmetric launch vehicle components for defense related applications. Information is presented on the thermal and mechanical properties of plasma sprayed AlBeMet which is a commercial Al-Be alloy produced by Brush Wellman Inc.
Self-Bonding, Exothermically Reactive MCrAlY Composites for Abradable-Clearance Control Coatings
Authors: Hermanek F.J.
Published: July 2021

Ni+Al, Ti+Al, NiCr+AI, and Cr+Al powders react exothermically in the heat zone of thermal spraying systems. Whether such reactions occur between aluminum and superalloy powders is the underlying question of this study. This paper describes composites of this nature and their sprayability to form adherent, metallurgically bonded deposits. Through parametric manipulation, coatings can be produced with a range of properties from dense to open (porous/abradable) structures. The paper also shows how seed particles can be clad with aluminum and sprayed to predictable property limits.
Plasma-Spray-Forming of Alumina Matrix Composite Reinforced with Metal Thin Wire
Authors: Sodeoka S. , Inoue T. , Suzuki M.
Published: July 2021

Alumina matrix composites reinforced with metal thin wire (Inconel-600) were successfully fabricated by plasma spray forming. The atmospheric plasma sprayed matrix layers and wire layers arranged by filament-winding technique were piled up alternately. Though the matrix and the wire were partially bonded only on the side which sprayed particles came flying to, a solid structure was obtained by this technique. Spraying in one direction perpendicular to the substrate made peculiar V-shape pores around the wires, but tilting the torch was effective to reduce the pores. The flexural strength of composite did not increase in spite of some crack deflections on the fracture surface. Owing to the wire pullout, however, the composite exhibited a remarkably higher apparent fracture energy than that of monolithic alumina ceramics.
Novel Bioactive Composites by Thermal Spray Process
Authors: Khor K.A. , Gu Y.W. , Li Y. , Quek C.H. , Lim V.J.P. , Cheang P.
Published: July 2021

This paper compares two types of hydroxyapatite (HA) composite coatings, HA/Ti-6Al-4V and HA/Y-ZrO2. The powders used in the study were prepared using a slurry process then deposited by plasma spraying. The resulting coatings were characterized based on their microstructure, mechanical properties, and biocompatibility. Both composite coatings performed better than pure HA coatings in tensile adhesion and indentation tests. Testing also revealed that the HA/Y-ZrO2 coatings had favorable strength and fracture toughness and that the HA/Ti-6Al-4V coatings had good affinity to living tissue and sufficient mechanical strength.
Evaluation of Adhesive Strength of Coating Film on Ni-Base Superalloy for Gas Turbine
Authors: Okazaki M. , Okamoto M. , Harada Y.
Published: July 2021

Methodology to evaluate the adhesive strength between the MCrAlY alloy coating film and the Ni-base superalloy substrate was studied and proposed. By employing the double cantilever beam specimens which were taken from the CoNiCrAlY alloy coated Ni-base superalloy, the fatigue crack propagation tests along the interface were carried out. Through the work particular attention was given to the threshold level to the fatigue crack propagation along the interface as a measure to represent the adhesive strength, based on fracture mechanics approach. The effects of temperature, the surface finishing of the substrate and the long term thermal aging on the adhesive strength were also investigated.