bluuebunny/crossref_metadata_2025 huggingface dataset:
Resonance-driven dynamically bipolar organic semiconductors for high-performance optoelectronic applications
Authors: Jiang He , Tao Ye , Jin Jibiao , Dai Yizhong , Xian Lijie , Wang Jun , Wang Shuang , Chen Runfeng , Zheng Chao , Huang Wei
Published: October 2020

Resonance-driven dynamically bipolar organic semiconductors were designed by using N–C=O resonance variation to transform one carbazole into an electron acceptor in the D-r-D structure. The blue OLEDs hosted by D-r-D materials showed a maximum EQE up to 31.2%.
Core@shell Sb@Sb2O3 nanoparticles anchored on 3D nitrogen-doped carbon nanosheets as advanced anode materials for Li-ion batteries
Authors: Chen Xian , Wang Liang , Ma Feng , Wang Tanyuan , Han Jiantao , Huang Yunhui , Li Qing
Published: October 2020

A nanocomposite of core@shell Sb@Sb2O3 particles anchored on 3D porous nitrogen-doped carbon nanosheets is synthesized and employed as a anode for Li-ion battery, demonstrating excellent rate capability and cycle performance.
Determination of chemical shift anisotropy tensor and molecular correlation time of proton pump inhibitor omeprazole by solid state NMR measurements
Authors: Dey Krishna Kishor , Ghosh Manasi
Published: October 2020

The correlation between the structure and dynamics of omeprazole is portrayed by extracting CSA parameters through the 13C 2DPASS CP-MAS SSNMR experiment, site specific spin–lattice relaxation time by Torchia CP experiment, and calculation of the molecular correlation time.
A novel synthesis of MIL-53(Al)@SiO2: an integrated photocatalyst adsorbent to remove bisphenol a from wastewater
Authors: Chatterjee Aditi , Jana Amiya Kumar , Basu Jayanta Kumar
Published: October 2020

MIL-53(Al)@SiO2 is a modified version of MIL-53(Al), which significantly improves its surface properties and photocatalytic activity.
Preparation of high self-healing efficient crosslink HTPB adhesive for improving debonding of propellant interface
Authors: Tu Jing , Xu Heng , Liang Li , Li Pingyun , Guo Xiaode
Published: October 2020

A high self-healing efficient HTPB-based adhesive containing disulfide bonds, which can improve propellant interface debonding defects at a safe temperature.
Copper(i)-catalysed azide–alkyne cycloaddition and antiproliferative activity of mono- and bis-1,2,3-triazole derivatives
Authors: El Malah Tamer , Abdel Mageid Randa E. , Awad Hanem M. , Nour Hany F.
Published: October 2020

A series of mono- and bis-1,2,3-triazole derivatives were prepared via the copper(i)-catalysed azide–alkyne cycloaddition between substituted aromatic derivatives, comprising one or two terminal alkyne groups and a selection of aromatic azides.
Artificial co-enzyme based on carbamoyl-modified viologen derivative cation radical for formate dehydrogenase in the catalytic CO2 reduction to formate
Authors: Miyaji Akimitsu , Amao Yutaka
Published: October 2020

The interaction between the single-electron reduced carbamoyl-modified-4,4-bipyridinium salt and CbFDH in the CO2 reduction to formate is elucidated by enzymatic kinetic analysis, the docking simulation and density functional theory calculation.
Designed anchoring geometries determine lifetimes of biotin–streptavidin bonds under constant load and enable ultra-stable coupling
Authors: Gruber Sophia , Löf Achim , Sedlak Steffen M. , Benoit Martin , Gaub Hermann E. , Lipfert Jan
Published: October 2020

We engineer streptavidin to control the anchoring geometry and increase the lifetime of the biotin bond under constant force in magnetic tweezers 100-fold.
Plasmonic core–shell nano-heterostructures with temperature-dependent optical nonlinearity
Authors: Pang Chi , Li Rang , Dong Ningning , Li Ziqi , Wang Jun , Ren Feng , Chen Feng
Published: October 2020

Plasmonics in bimetallic heterostructures have emerged as powerful tools for tunable ultrafast dynamics in nonlinear optical responses.
Direct electron-beam patterning of monolayer MoS2 with ice
Authors: Yao Guangnan , Zhao Ding , Hong Yu , Wu Shan , Liu Dongli , Qiu Min
Published: October 2020

Direct electron-beam patterning of monolayer MoS2 that is covered on top by an ice thin-film was achieved.
Improving thermal and mechanical properties of biomass-based polymers using structurally ordered polyesters from ricinoleic acid and 4-hydroxycinnamic acids
Authors: Yamamoto Atsushi , Nemoto Koji , Yoshida Masaru , Tominaga Yuichi , Imai Yusuke , Ata Seisuke , Takenaka Yasumasa , Abe Hideki , Sato Kazuhiko
Published: October 2020

The synthesis of structurally ordered polyesters derived from ricinoleic acid and 4-hydroxycinnamic acids improves the thermal and mechanical properties.
Systematic investigation of CO2 : NH3 ice mixtures using mid-IR and VUV spectroscopy – part 1: thermal processing
Authors: James Rachel L. , Ioppolo Sergio , Hoffmann Søren V. , Jones Nykola C. , Mason Nigel J. , Dawes Anita
Published: October 2020

The stoichiometric mixing ratio of CO2 : NH3 ices determines both the initial chemical and physical properties of the ices and their evolution through thermal processing including CO2 bonding environment, NH3 crystallite size and amount of residue.
A molten salt-based nitridation approach for synthesizing nanostructured InN electrode materials
Authors: Purwiandono Gani , Manseki Kazuhiro , Sugiura Takashi
Published: October 2020

Single-phase InN nanocrystals were synthesized for the first time by a molten salt-based nitridation approach using InCl3 and LiNH2 as indium and nitrogen sources, respectively.
Needle-like CoO nanowire composites with NiO nanosheets on carbon cloth for hybrid flexible supercapacitors and overall water splitting electrodes
Authors: Li Sa , Feng Ruichao , Li Mai , Zhao Xuan , Zhang Beihe , Liang Yuan , Ning Huanpo , Wang Jiale , Wang Chunrui , Chu Paul K.
Published: October 2020

A nanoscale core–shell NiO@CoO composite is prepared on flexible carbon cloth for electrodes in supercapacitors and overall water splitting.
Optical and dielectric characteristics of polyethylene oxide/sodium alginate-modified gold nanocomposites
Authors: Farea M. O. , Abdelghany A. M. , Oraby A. H.
Published: October 2020

Films of polyethylene oxide and sodium alginate polymer blend (50/50 wt%) embedded with different quantities of Au nanoparticles with size 3–32 nm were made using the casting process.
Synthesis and modification of ZIF-8 and its application in drug delivery and tumor therapy
Authors: Wang Qiuxiang , Sun Yue , Li Shangfei , Zhang Pingping , Yao Qingqiang
Published: October 2020

Synthesis and modification of ZIF-8 and its application in drug delivery, stimulus response-controlled drug release and tumor therapy.
Highly active and durable WO3/Al2O3catalysts for gas-phase dehydration of polyols
Authors: Aihara Takeshi , Asazuma Katsuya , Miura Hiroki , Shishido Tetsuya
Published: October 2020

Gas-phase glycerol dehydration over WO3/Al2O3catalysts was investigated.
Multimerized self-assembled cagedtwo-in-onesiRNA nanoparticles for photomodulation of RNAi-induced gene silencing
Authors: Chen Changmai , Jing Nannan , Wang Zhongyu , Zhang Yu , Chen Wei , Tang Xinjing
Published: October 2020

Upon light irradiation, multimerized self-assembled caged Two-in-One siRNA nanoparticles (Multi-Chol-siRNA) were collapsed to release trapped siRNAs for multiple RNAi-induced gene silencing activity.
Aromatic foldamers as scaffolds for metal second coordination sphere design
Authors: Meunier Antoine , Singleton Michael L. , Kauffmann Brice , Granier Thierry , Lautrette Guillaume , Ferrand Yann , Huc Ivan
Published: October 2020

Wrapping a [2Fe–2S] metal complex in an aromatic foldamer helix is introduced as a new approach to tailor a second coordination sphere.
Crack-free hematite inverse opal photo-anodes for enhancing photo-electrochemical water splitting
Authors: Zhu Heling , Zhang Yajuan , Zhu Jingqian , Li Yuhuan , Jiang Saihua , Wu Na , Wei Yu , Zhou Jinming , Song Yanlin
Published: October 2020

Crack-free hematite inverse opal photoanodes were fabricated by directly “sewing” the cracks in opal templates, which exhibited record high photo-electrochemical water splitting for pristine nanostructured hematite anodes.
A flexible and wide pressure range triboelectric sensor array for real-time pressure detection and distribution mapping
Authors: Yang Dan , Guo Hengyu , Chen Xiangyu , Wang Longfei , Jiang Peng , Zhang Weiqiang , Zhang Liqun , Wang Zhong Lin
Published: October 2020

A flexible and wide pressure range triboelectric sensor array was constructed for real-time pressure detection and distribution mapping.
Insights into the hydronium-ion storage of alloxazine in mild electrolyte
Authors: Sun Tianjiang , Liu Chang , Xu XiuFang , Nian Qingshun , Zheng Shibing , Hou Xuesen , Liang Jing , Tao Zhanliang
Published: October 2020

Mg2+ ions, exhibiting catalytic properties, can promote hydronium-ion transfer in alloxazine in 1 M Mg(NO3)2 electrolyte.
Unraveling the mechanism for an amelogenin-derived peptide regulated hydroxyapatite mineralization via specific functional domain identification
Authors: Wang Yufei , Hu Die , Cui Jingyao , Zeng Yuhao , Gan Xinyan , Chen Zhongxin , Ren Qian , Zhang Linglin
Published: October 2020

The specific functions of different domains of one peptide were compared from different concerning aspects for unravelling the remineralization mechanism.
Fluorescent sensing for amines with a low detection limit based on conjugated porous polymers
Authors: Yu Jie , Zhang Chi
Published: October 2020

Two types of nitrogen-containing conjugated porous polymers as ultra-low detection limit amine sensors.
Genetic activity during early plant embryogenesis
Authors: Tian Ran , Paul Priyanka , Joshi Sanjay , Perry Sharyn E.
Published: October 2020

Seeds are essential for human civilization, so understanding the molecular events underpinning seed development and the zygotic embryo it contains is important. In addition, the approach of somatic embryogenesis is a critical propagation and regeneration strategy to increase desirable genotypes, to develop new genetically modified plants to meet agricultural challenges, and at a basic science level, to test gene function. We briefly review some of the transcription factors (TFs) involved in establishing primary and apical meristems during zygotic embryogenesis, as well as TFs necessary and/or sufficient to drive somatic embryo programs. We focus on the model plant Arabidopsis for which many tools are available, and review as well as speculate about comparisons and contrasts between zygotic and somatic embryo processes.
Comparison of tyrosine kinase domain properties for the neurotrophin receptors TrkA and TrkB
Authors: Artim Stephen C. , Kiyatkin Anatoly , Lemmon Mark A.
Published: October 2020

The tropomyosin-related kinase (Trk) family consists of three receptor tyrosine kinases (RTKs) called TrkA, TrkB, and TrkC. These RTKs are regulated by the neurotrophins, a class of secreted growth factors responsible for the development and function of neurons. The Trks share a high degree of homology and utilize overlapping signaling pathways, yet their signaling is associated with starkly different outcomes in certain cancers. For example, in neuroblastoma, TrkA expression and signaling correlates with a favorable prognosis, whereas TrkB is associated with poor prognoses. To begin to understand how activation of the different Trks can lead to such distinct cellular outcomes, we investigated differences in kinase activity and duration of autophosphorylation for the TrkA and TrkB tyrosine kinase domains (TKDs). We find that the TrkA TKD has a catalytic efficiency that is ∼2-fold higher than that of TrkB, and becomes autophosphorylated in vitro more rapidly than the TrkB TKD. Studies with mutated TKD variants suggest that a crystallographic dimer seen in many TrkA (but not TrkB) TKD crystal structures, which involves the kinase-insert domain, may contribute to this enhanced TrkA autophosphorylation. Consistent with previous studies showing that cellular context determines whether TrkB signaling is sustained (promoting differentiation) or transient (promoting proliferation), we also find that TrkB signaling can be made more transient in PC12 cells by suppressing levels of p75NTR. Our findings shed new light on potential differences between TrkA and TrkB signaling, and suggest that subtle differences in signaling dynamics can lead to substantial shifts in the cellular outcome.
Influence of planetary gas accretion on the shape and depth of gaps in protoplanetary discs
Authors: Bergez-Casalou C. , Bitsch B. , Pierens A. , Crida A. , Raymond S. N.
Published: October 2020

It is widely known that giant planets have the capacity to open deep gaps in their natal gaseous protoplanetary discs. It is unclear, however, how gas accretion onto growing planets influences the shape and depth of their growing gaps. We performed isothermal hydrodynamical simulations with the Fargo-2D1D code, which assumes planets accreting gas within full discs that range from 0.1 to 260 AU. The gas accretion routine uses a sink cell approach, in which different accretion rates are used to cope with the broad range of gas accretion rates cited in the literature. We find that the planetary gas accretion rate increases for larger disc aspect ratios and greater viscosities. Our main results show that gas accretion has an important impact on the gap-opening mass: we find that when the disc responds slowly to a change in planetary mass (i.e., at low viscosity), the gap-opening mass scales with the planetary accretion rate, with a higher gas accretion rate resulting in a larger gap-opening mass. On the other hand, if the disc response time is short (i.e., at high viscosity), then gas accretion helps the planet carve a deep gap. As a consequence, higher planetary gas accretion rates result in smaller gap-opening masses. Our results have important implications for the derivation of planet masses from disc observations: depending on the planetary gas accretion rate, the derived masses from ALMA observations might be off by up to a factor of two. We discuss the consequences of the change in the gap-opening mass on the evolution of planetary systems based on the example of the grand tack scenario. Planetary gas accretion also impacts stellar gas accretion, where the influence is minimal due to the presence of a gas-accreting planet.
Chemical evolution during the formation of a protoplanetary disk
Authors: Coutens A. , Commerçon B. , Wakelam V.
Published: October 2020

Context.The chemical composition of protoplanetary disks is expected to impact the composition of the forming planets. Characterizing the diversity of chemical composition in disks and the physicochemical factors that lead to this diversity is consequently of high interest.

Aims.The aim of this study is to investigate the chemical evolution from the prestellar phase to the formation of the disk, and to determine the impact that the chemical composition of the cold and dense core has on the final composition of the disk.

Methods.We performed 3D nonideal magneto-hydrodynamic (MHD) simulations of a dense core collapse using the adaptive-mesh-refinement RAMSES code. For each particle ending in the young rotationally supported disk, we ran chemical simulations with the three-phase gas-grain chemistry code Nautilus. Two different sets of initial abundances, which are characteristic of cold cores, were considered. The final distributions of the abundances of common species were compared to each other, as well as with the initial abundances of the cold core.

Results.We find that the spatial distributions of molecules reflect their sensitivity to the temperature distribution. The main carriers of the chemical elements in the disk are usually the same as the ones in the cold core, except for the S-bearing species, where HS is replaced by H2S3, and the P-bearing species, where atomic P leads to the formation of PO, PN, HCP, and CP. However, the abundances of less abundant species change over time. This is especially the case for “large” complex organic molecules (COMs) such as CH3CHO, CH3NH2, CH3OCH3, and HCOOCH3which see their abundances significantly increase during the collapse. These COMs often present similar abundances in the disk despite significantly different abundances in the cold core. In contrast, the abundances of many radicals decrease with time. A significant number of species still show the same abundances in the cold core and the disk, which indicates efficient formation of these molecules in the cold core. This includes H2O, H2CO, HNCO, and “small” COMs such as CH3OH, CH3CN, and NH2CHO. We computed the MHD resistivities within the disk for the full gas–grain chemical evolution and find results in qualitative agreement with the literature assuming simpler chemical networks.

Conclusions.In conclusion, the chemical content of prestellar cores is expected to affect the chemical composition of disks. The impact is more or less important depending on the type of species. Users of stand-alone chemical models of disks should pay special attention to the initial abundances they choose.
Dorado and its member galaxies
Authors: Rampazzo R. , Ciroi S. , Mazzei P. , Di Mille F. , Congiu E. , Cattapan A. , Bianchi L. , Iodice E. , Marino A. , Plana H. , Postma J. , Spavone M.
Published: October 2020

Context. Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the southern hemisphere. Although several studies have been dedicated to defining its members, their kinematics, and the hot and cold gas content, in particular H I, their present star formation activity remains unknown.

Aims. For the first time, we map the Hα distribution as a possible indicator of the star formation activity of Dorado members, a large fraction of which show interaction and merging signatures independently of their morphological type.

Methods. With the 2.5 m du Pont and the 1m Swope telescopes, we obtained narrow-band calibrated images of 14 galaxies that form the backbone of the group, mapping Hα+[N II] down to a few 10−17 erg cm−2 s−1 arcsec−2. We estimated the galaxy star formation rate from the Hα fluxes and corrected for Galaxy foreground extinction and [N II] contamination.

Results. We detected Hα+[N II] emission in all galaxies. H II regions clearly emerge in late-type galaxies, while in early-type galaxies the Hα+[N II] emission is dominated by [N II], especially in the central regions. However, H II complexes are revealed in four early-type galaxies. Even in the compact group SGC 0414-5559, in the projected centre of Dorado, H II regions are found both throughout the late-type galaxies and in the very outskirts of early-type members. Considering the Dorado group as a whole, we notice that the Hα+[N II] equivalent width, a measure of the specific star formation, increases with morphological type from early- to late-type members, although it remains lower than that observed in similar surveys of spiral galaxies. The star formation rate of the spiral members is in the range of what is observed in similar galaxies surveys (James et al., 2004). However, in three spiral galaxies, NGC 1536, PGC 75125, and IC 2058, the star formation rate is well below the median for their morphological classes. Conversely, the star formation rate of some early-type members tends to be higher than the average derived from Hα+[N II] surveys of this morphological family.

Conclusions. We detected Hα+[N II] in all the early-type galaxies observed and half of them show H II regions in well-shaped rings as well as in their outskirts. These findings suggest that early-type galaxies in this group are not dead galaxies: their star formation has not yet shut down. Mechanisms such as gas stripping and gas accretion through galaxy–galaxy interaction seem relevant in modifying star formation in this evolutionary phase of Dorado.
Spectroscopic classification of a complete sample of astrometrically-selected quasar candidates using Gaia DR2
Authors: Heintz K. E. , Fynbo J. P. U. , Geier S. J. , Møller P. , Krogager J.-K. , Konstantopoulou C. , de Burgos A. , Christensen L. , Steinhardt C. L. , Milvang-Jensen B. , Jakobsson P. , Høg E. , Arvedlund B. E. H. K. , Christiansen C. R. , Hansen T. B. , Henriksen P. D. , Kuszon K. B. , McKenzie I. B. , Mosekjær K. A. , Paulsen M. F. K. , Sukstorf M. N. , Wilson S. N. , Ørgaard S. K. K.
Published: October 2020

Here we explore the efficiency and fidelity of a purely astrometric selection of quasars as point sources with zero proper motions in the Gaia data release 2 (DR2). We have built a complete candidate sample including 104 Gaia-DR2 point sources, which are brighter than 20th magnitude in the Gaia G-band within one degree of the north Galactic pole (NGP); all of them have proper motions that are consistent with zero within 2σ uncertainty. In addition to pre-existing spectra, we have secured long-slit spectroscopy of all the remaining candidates and find that all 104 stationary point sources in the field can be classified as either quasars (63) or stars (41). One of the new quasars that we discover is particularly interesting as the line-of-sight to it passes through the disc of a foreground (z = 0.022) galaxy, which imprints both NaD absorption and dust extinction on the quasar spectrum. The selection efficiency of the zero-proper-motion criterion at high Galactic latitudes is thus ≈60%. Based on this complete quasar sample, we examine the basic properties of the underlying quasar population within the imposed limiting magnitude. We find that the surface density of quasars is 20 deg−2 (at G <  20 mag), the redshift distribution peaks at z ∼ 1.5, and only eight systems (13-3+5%) show significant dust reddening. We then explore the selection efficiency of commonly used optical, near-, and mid-infrared quasar identification techniques and find that they are all complete at the 85−90% level compared to the astrometric selection. Finally, we discuss how the astrometric selection can be improved to an efficiency of ≈70% by including an additional cut requiring parallaxes of the candidates to be consistent with zero within 2σ. The selection efficiency will further increase with the release of future, more sensitive astrometric measurements from the Gaia mission. This type of selection, which is purely based on the astrometry of the quasar candidates, is unbiased in terms of colours and intrinsic emission mechanisms of the quasars and thus provides the most complete census of the quasar population within the limiting magnitude of Gaia.
A psychoacoustical study to investigate the perceived unpleasantness of infrasound combined with audio-frequency sound
Authors: Burke Elisa , Uppenkamp Stefan , Koch Christian
Published: October 2020

At many immission sites of infrasound (frequency f < 20 Hz), humans are exposed to a mixture of infrasound and sound in the common audio-frequency range (audio sound, 20 Hz < f < 20 kHz). Therefore, the purpose of this study was to examine the auditory perception of infrasound and audio sound not only in isolation but also in combination. This laboratory study aims to investigate the perceived unpleasantness of infrasound (sinusoid at 12 Hz) and audio sound (sinusoid at 1000 Hz, pink-noise 250–4000 Hz), presented alone or in combination with each other. A pairwise comparison task and a rating task using a numerical scale were conducted with 19 normal hearing listeners. In addition, individual detection thresholds were determined for the infrasound stimulus. Combinations of infrasound and audio sound were rated as equally or more unpleasant than either sound presented alone. Inter-individual differences in unpleasantness ratings using the numerical scale were particularly high for stimuli containing infrasound. This can only in part be related to the large variability in infrasound thresholds. These findings suggest that simultaneous exposure to infrasound and audio sound can increase the perceived unpleasantness when both are presented at a sufficient level above the detection threshold.
Current Situation of Titanium Research, Development and Applications in China
Authors: Chang Hui , Zhou Lian
Published: October 2020

This planery paper reviewed the progress of titanium research, development, applications and industry in China during the past four years since the Ti-2015 conference in San Diego. Including additive manufacturing, material genome engineering technologies, low cost titanium and short manufacture processing, powder metallurgies and near net shape fabrication technologies, applications in marine, gas and oil exploitations, as well as consuming products. And the industry situation in China has also been reviewed.
RECENT ADVANCES IN TITANIUM TECHNOLOGY IN THE UNITED STATES
Authors: Li Dongjian(Don) , Venkatesh Vasisht
Published: October 2020

Substantial progress has continued in the US since the last (13th) World Titanium Conference with regards to titanium technology, products, processing, computational modeling tools and applications. Titanium components produced by additive manufacturing have been qualified and achieved production applications in commercial and military aircraft hardware. New high-performance titanium alloys have been developed for higher temperature service and applications requiring more demanding static and dynamic properties. Current production processes for titanium have been optimized, and new processes have been developed to further reduce cost and improve product quality. Titanium suppliers, OEM’s, government labs and academia are working closely together to address fundamental industry-wide issues. Computer modeling is now used extensively in industrial and research facilities to accelerate the pace and success of these developments.
Repairing Ti-6Al-4V aeronautical components with DED additive manufacturing
Authors: Rauch Matthieu , Hascoët Jean-Yves , Mallaiah Manjaiah
Published: October 2020

Direct Energy Deposition (DED) processes are Additive Manufacturing (AM) processes that provide new perspectives for the manufacturing industry. In particular the area of component repair could highly benefit from these processes. It is consequently necessary to ensure the ability of DED processes, so that the repaired component can provide the same level of service than a new one. This paper focuses on the repair of Ti-6Al-4V parts by powder based LMD AM and investigates its accuracy, repeatability and reliability. At first, an experimental campaign has been carried out to evaluate the characteristics of as-built material. Optimal process parameter selection is made by a porosity and macrostructure analysis. Tensile properties, Low Cycle Fatigue and crack propagation studies have been done on as-built samples (100% AM) and interface samples (50% AM / 50% substrate). The results compare to wrought alloy and validate the relevance of LMD to produce sound repaired parts. In a second section, the paper proposes a semi automatic repair method of Ti-6Al-4V components: the defect geometry and the CAD model of the part to repair are identified from 3D scanning operations. Adapted additive and machining tool paths are then generated on the selected equipment.
LINEAR FRICTION WELDING – PROCESS DEVELOPMENT AND APPLICATIONS IN AEROSPACE INDUSTRY
Authors: SADALLAH Y.
Published: October 2020

Linear Friction Welding (LFW) is a solid-state joining process very well adapted to titanium alloys, producing high integrity joints with fine grain, hot-forged microstructure and narrow heat affected zone. The first industrial application of this process was found in aircraft engines, for the manufacturing of “blisks” (“bladed disks”): linear friction welding the blades onto a disk provides economic savings and reduces the manufacturing time, compared to machining the whole blisk from solid. While the diffusion of LFW process in the blisk manufacturing market is still at the early stages and have promising growth potential, the process is now being developed for aircraft structures such as clips, brackets, hinges, fittings, and larger parts like seat rails, wing ribs, lintels and fuselage frames. The LFW process allows not only to manufacture a given part at a lower cost, it also open new part design possibilities, that were not available with traditional manufacturing processes.

The manufacturing process of Ti-6Al-4V structural and engine parts by LFW is explained, highlighting advantages, limitations and part design best practices. Several LFW candidate parts are introduced and evaluated through feasibility, mass savings, post weld operations and overall cost savings.
An experimental study of Ti-6Al-4V powder reactivity in gaseous environment: Application to additive manufacturing
Authors: Mahdi Siblani Mohamad , Ollivier Maelig , Favergeon Loïc
Published: October 2020

Currently, one of the current issues related to the additive manufacturing is the change in the properties of Ti-6Al-4V powder during this process. This change has been attributed to the interaction of this powder with its gaseous environment that can contain a small quantity of oxygen, nitrogen, carbon dioxide and/or water vapour. Therefore, the aim of this work is to study the effect of oxygen and nitrogen partial pressure as well as the effect of the temperature on the corrosion of the Ti-6Al-4V powder. The results show that the temperature and the oxygen partial pressure have an effect on the corrosion kinetics, which is not the case of nitrogen partial pressure. This study is a first step towards a better understanding of the ageing of Ti-6Al-4V powder during additive manufacturing processes.
An analysis of thermo-mechanical fatigue crack growth in the titanium alloy Ti-6246
Authors: Palmer J. , Jones J. , Whittaker M. , Williams S.
Published: October 2020

Titanium alloys are equipped with impressive high strength and low density, along with other notable mechanical properties. Often the choice for low to intermediate temperature mechanical applications, titanium alloys are well utilised within the aerospace industry, making up 40% of the aero-engine. Within the gas turbine engine, the high transient thermal stresses developed due to variations in power requirements during a typical flight cycle give rise to the phenomenon of thermo-mechanical fatigue (TMF). The lifing models utilised within this research focus on damage tolerance approaches. TMF crack growth test techniques have been developed for high performance titanium alloys, in which diverse phasing (φ) between mechanical loading and temperature have been investigated. In addition, factors affecting the TMF behaviour of Ti-6246, including peak temperature, minimum temperature and temperature range have also been explored.
Micromechanical approaches to understand dwell fatigue: from titanium a-b microstructures to disc thermal alleviation
Authors: Zheng Zebang , Zhang Zhen , Britton Ben , Dunne Fionn
Published: October 2020

Micro-pillar tests on α and α-β colony Ti alloys in combination with crystal plasticity finite element analysis has enabled the extraction of a and b phase slip strength and rate sensitivity properties. Faithfully representative α-β microstructure polycrystal plasticity models have then been established in order to investigate dwell fatigue in isothermal rig test behaviour and anisothermal thermomechanical flight loading conditions. The role of thermal alleviation in diminishing dwell sensitivity has been demonstrated.
Normal and dwell fatigue behavior of a near-alpha titanium alloy - IMI 834
Authors: Yazar K.U. , Karmakar Anish , Sahu Vivek , Bhattacharjee Amit , Suwas Satyam
Published: October 2020

Dwell sensitivity of titanium alloys at ambient temperature (~250 C) is a well-known phenomenon, although the question about the exact micromechanical reasons responsible for this still remains open. In this work, the normal and dwell fatigue response of a near-alpha titanium alloy, IMI 834, is studied. Samples with three different microstructures, namely, fully lamellar, fully equiaxed and bimodal, are evaluated for their dwell fatigue behaviors. A reduction in fatigue life by at least an order of magnitude is seen in all the three microstructures. Large plastic strain accumulation (almost equal to the monotonic ductility) was observed during the dwell fatigue loading condition and this is held responsible for this large debit in fatigue life. The normal fatigue lives decreased in the order, bimodal > fully equiaxed > fully lamellar, while the dwell fatigue lives decreased in the order, fully equiaxed > fully lamellar > bimodal. Bimodal microstructure showed a dwell fatigue debit of 17, while fully lamellar and fully equiaxed showed a debit of 9 and 10, respectively.
Effect of microstructure on tensile properties of Ti-17 alloys forged using a 1500-ton forging simulator
Authors: Yamabe-Mitarai Y. , Kuroda S. , Motohashi N. , Matsumoto H. , Miyamoto G. , Yoshida Y. , Yamanaka K. , Niinomi M. , Itsumi Y.
Published: October 2020

Microstructure dependence on mechanical properties were investigated for Ti-17 forged at temperatures between 700 and 850 ˚C with deformation ratio from 33 to 80 %, and solutiontreated at 800˚C for 4 hours and aged at 620 ˚C for 8 hours. The microstructure was observed after solution and aging treatments. The volume fraction and the size of the primary alpha phase was controlled by solution treatment temperature, not forging temperature and deformation ratio. Forging temperature affected the morphology of grain boundary (GB) alpha phase. Deformation ratio affected the grain size and the aspect ratio of the horizontal and vertical grain size of the prior beta phase. The tensile strength was investigated at room temperature, 450, and 600 ˚C. Forging temperature and deformation ratio did not affect the tensile strength because there is no large difference of the volume fraction of the alphaphase. On the other hand, the elongation and the reduction of area increased with increase of the aspect ratio of the prior beta grains; that means, increase of the deformation ratio. Raising of forging temperature also increased elongation and reduction of area due to the film-like GB alphaphase.
DEMONSTRATION OF THE APPLICATION OF SUPERPLASTIC FORMING USING INFRARED HEATING EMITTERS TO A PART OF STRUCTURE INCLUDING VARIOUS GEOMETRICAL SINGULARITIES
Authors: LAMIC Elise , FLEURISSON Nicolas , NAZARET Fabien , BONNAFÉ Jean-Pierre , ROPARS Ludovic , COLLOT Alexandre
Published: October 2020

ArianeGroup and Aurock led a feasibility study through the realization of a scale 1 TA6V demonstrator, using superplastic forming (SPF). ArianeGroup designed the demonstrator according to its knowledge of representative structures, comprising singularities: welds, stiffeners and areas with important thicknesses variations. Aurock performed first numerical simulations of the complete process, putting in evidence the various difficulties to be solved. Then, the demonstrator was physically carried out.

Once the demonstration was virtually obtained, each steps of the process were experimented: welding of thick plates with limited deformation, machining of flat panels, pre-forming by rolling and final SPF. For the SPF step, a heating cover and a reinforced refractory castable die were manufactured. Infrared emitters’ position and heating power regulation laws were carefully defined, for the panel to be kept at the correct temperature until being formed.

The SPF step led to a successful demonstration of the representative structure. The experimental approach confirmed the process modelling predictability. Limited Scale 1 demonstration was necessary to ensure the process validity with real thicknesses and thickness variations, which are known to mask problems if scale reductions are used without precautions. This methodology can be transfer to a real structure only by tooling adaptations, without additional feasibility works.
The orbital friction welding process for engines components in aeronautic
Authors: Escaffre Jérémy , Lefaux Yann , Lenain Astrid
Published: October 2020

Titanium alloys are key materials in engines due to their low density, their high mechanical properties and their good resistance to corrosion and oxidation. Titanium engine parts are manufactured most of the time by forging, giving good mechanical properties associated with the possibility to optimize final microstructures of the parts.

Due to design challenges consisting of making parts more robust and lighter, new processes are emerging. For some parts, friction welding can give opportunities to achieve those objectives because these assemblies are characterised by very good mechanical properties, generally higher than the raw unwelded materials [1].

As a consequence, the friction welding process is finding increasing applications as a manufacturing technology for the production of titanium alloy Ti-6Al-4V aerospace components [2]. Among those processes, the Orbital Friction Welding (OFW) technology is under study for low pressure compressors manufacturing. The BLuM® (Bladed drum, Figure 1), is constituted of a drum comprising several stages of friction-welded blades. Such architecture allows an important weight saving and performances improvement compared to current design.

The objective of the article consists of addressing the orbital friction welding process, through the description of its characteristics, the key process parameters, the microstructures and the way of ensuring good integrity of the interface.

The objective of the article consists of addressing the orbital friction welding process, through the description of its characteristics, the key process parameters, the microstructures and the way of ensuring good integrity of the interface.
Extra-high oxygen addition as a new strengthening strategy to overcome strength/ductility trade-off in fully biocompatible hexagonal titanium alloys
Authors: Poulain Régis , Delannoy Stéphanie , Couzinié Jean-Philippe , Guillot Ivan , Clouet Emmanuel , Prima Frédéric
Published: October 2020

A new titanium alloy family was developed aiming at creating a fully biocompatible alternative to titanium alloys currently on the dental implants market. Despite their hexagonal closepacked (HCP) single-phase structure, these Ti-Zr-O materials display an extremely interesting combination of properties. Zirconium is shown to be involved through a double contribution: on the one hand, a moderate but noticeable solid solution strengthening effect and on the other hand, a strong grain refinement. Therefore, the combination of both effects results in a beneficial strengthening of Ti-Zr-O alloys. However, the main remarkable aspect remains the outstanding hardening generated by extra high oxygen addition, occurring without any drop of ductility. The evolution of the dislocation network according to the oxygen content has been investigated to understand the underlying mechanisms in these Ti-Zr-O alloys, allowing to overcome the classical strength/ductility trade-off in commercial titanium alloys. Finally, the different perspectives of these findings in the field of biomedical and more generally in the field of titanium alloys are discussed.
Deformation and fracture behavior of in-situ Ti composites reinforced with TiB/nano-sized particles
Authors: Han Yuanfei , Sun Xianglong , Liu Pinwang , Huang Guangfa , Xiao Lv , Lu Weijie
Published: October 2020

The hot deformation and fracture behavior of TiB/nano-sized particulate reinforced titanium matrix composites were investigated. The effect of reinforcement contents and initial structures on the isothermal deformation and fracture characteristic were investigated through microstructure analysis, tensile tests and crack propagation tests. It was found that the optimal working parameters for Ti composites is determined at 900-950°C/0.01-0.1 s-1, which is associated with the continuous dynamic recrystallization of primary a grains and dynamic globularization of lamellar α. The necklace recrystallization was observed in β phase region, and the instability mechanisms include inhomogeneous deformation and breaking or debonding of TiB whiskers. Additionally, the addition of reinforcements refines α phases, decreasing the lamellar α width. The aspect ratio of TiB is much higher with the increase of reinforcement content. Higher content (2.5 vol. % and 5 vol. %) brings about more broken reinforcements and defects, which result in brittle fracture in Ti composite. Reinforcements and defects are believed to be the key factors to determine the crack propagation. Intergranular cracking is the main cracking way in the region where there are few reinforcements. Defects caused by fractured TiB play a dominant role in diverting intergranular cracking to transgranular cracking.

Key words: Hot deformation, dynamic globularization, dynamic recrystallization, Titanium matrix composites
Tribological functionalization of titanium alloys by Micro-Arc Oxidation for marine applications
Authors: MATHIS Aude , MILLOT Thierry , BRANGER Vincent , MULLER Remy , GUENEHEUX Jean-Yves
Published: October 2020

Micro-arc Oxidation (MAO) process is a plasma assisted electrochemical process, which allows formation of ceramic-like dry oxides on top of light alloys surfaces.

The good corrosion resistance as well as the low density of titanium alloys are recognized and so required for conception of structural parts in marine environment. However, their tribological behaviour reveals an important tendency to stick-slip phenomenon, which makes use of these alloys for dynamic contact mechanisms difficult.

Through the MAO project from IRT M2P, formation of a MAO coating composed of aluminium titanate has been investigated to improve tribological behaviour of a commercially pure titanium (Grade 2) and an α+β alloy (TA6V, Grade 5). Pin-on-disc testing has been carried out to evaluate friction coefficient and the presence or not of stick-slip phenomenon in various contact configurations (involving non-treated titanium surfaces, MAO treated surfaces, with steel or titanium balls …) in dry or artificial seawater media. Those test campaigns are completed by evaluation of fatigue behaviour, and tribological testing on a demonstrator. Finally, this study highlights influence of MAO coating on diminishing (to removed) stick-slip phenomenon, accompanied by a reduction of friction coefficient, whatever the kind of contact (single treated surface or both ones) and the medium.
Deformation and fracture behavior of new strain-transformable titanium alloys: a multi-scale investigation
Authors: VARENNE Chloé , PRIMA Frédéric , BROZEK Cédrik , BOURGON Julie , BESSON Jacques , GOURGUES-LORENZON Anne-Françoise
Published: October 2020

Titanium alloys possessing Twinning and Transformation Induced Plasticity effects show promising mechanical properties, particularly high ductility, hardenability, impact and fracture toughness. This work focuses on a strain-transformable, coarse-grained β-Ti-Cr-Sn alloy displaying TWIP effect. To account for the enhanced properties of this alloy, compared to more conventional β-Ti alloys, fracture and deformation features were correlated at different scales. Examinations evidenced a major role of twinning and, more generally, of plasticity-induced phenomena in the ductile fracture process. The resistance of this alloy to plastic deformation (work-hardening), and to crack initiation and propagation is interpreted in view of the progressive, multiscale twinning mechanisms that occur up to the very final stages of fracture.
Extremely rapid age hardening behavior in solution treated Ti-5Al-2Fe-3Mo
Authors: KUNIEDA Tomonori , FUJII Hideki , TAKAHASHIa Kazuhiro
Published: October 2020

To grasp age hardening and phase transformation behaviors in a β rich α+β type titanium alloy, Ti-5Al-2Fe-3Mo, during aging at 300-500°C after the solution treatment at high α+β temperature. Vickers hardness and microstructure changes during aging were closely investigated using XDR and TEM/EDS. Vickers hardness rapidly increased with increasing holding time and reached about 440HV by aging at 450°C for only 5 min. It further increased to 510HV in 8h of aging time. The initial stage of age hardening is extremely fast compared to that in other conventional α+β and β type titanium alloys. After aging for only 5min, extremely fine acicular products of about 2 to 10 nm in width were formed in the transformed β phase. TEM/EDS analysis revealed that all substitutional alloying elements, Al, Fe and Mo, homogeneously distributed after the aging, indicating that the transformation is diffusionless as far as substitutional elements are concerned just like martensite transformation although it has time dependency. To explain the mechanism of this unique phase transformation having features of isothermal martensite transformation, we propose bainitic transformation where interstitials such as O diffuse without conspicuous diffusion of substitutional elements.
The effect of loading direction on the dwell fatigue properties of Ti-6Al-4V forged bar with highly oriented texture
Authors: Mori Kenichi , Hashimoto Shohtaroh , Okui Toshiyuki , Shirai Yoshihisa , Miyahara Mitsuo
Published: October 2020

The purpose of this study was to improve our understanding of the effect of macro/micro texture on dwell fatigue properties. The Ti-6Al-4V forged bar with highly oriented texture and fine equiaxed microstructure was used. Dwell fatigue, cyclic fatigue and creep tests were conducted at room temperature by using specimens taken in the longitudinal (L) direction and the transverse (T) direction of the bar. The effects of loading direction on dwell fatigue life and fracture surface morphology were examined in detail. The dwell fatigue life in T direction was shorter than that in L direction. The fracture surface morphologies were characteristically varied by loading waveform, amplitude and directions. In the range of 93 - 95% of 0.2%PS, the characteristic large facets were observed in the T direction in dwell fatigue. Detailed analyses revealed that the large facet consists of multiple initiation facets and propagation facets. The propagation facet plane and crack propagation direction appeared to correspond to alpha (0001) <10-10>. Furthermore, the relationship between strain rate and life time was compared to that for room temperature creep. The deviation from the Monkman-Grant relationship corresponded to the change of the fracture surface morphology.
In-situ characterization of growth of isothermal ω phase in metastable β-Ti alloy TIMETAL LCB
Authors: Nejezchlebova J. , Bodnarova L. , Janovska M. , Sedlak P. , Seiner H. , Smilauerova J. , Janecek M. , Appolaire B.
Published: October 2020

Metastable β-Ti alloys exhibit various solid-solid phase transitions. Our study is focused on the characterization of the diffusion controlled β→ωiso phase transition. The particles of ω phase play an important part in thermomechanical treatment since they serve as heterogeneous nucleation sites for precipitation of finely dispersed particles of hexagonal α phase. The in-situ observation of the growth of particles of ω phase could be difficult by conventional techniques. However, it was shown recently that the ω phase significantly influences the elastic constants of the material, and the different forms of ω phase have different effects on the elastic anisotropy, as well as on the internal friction coefficients. Therefore, the β→ω phase transformation could be in-situ observed by the precise measurement of the tensor of elastic constants. In this contribution, we present the study of the kinetics of the β→ωiso phase transformation by resonant ultrasound spectroscopy. The polycrystalline samples of TIMETAL LCB alloy were in-situ examined by this technique during isothermal and non-isothermal ageing at temperatures up to 300 °C.