Long-term thermal stability of addition-type polyimide resins derived from pyromellitic dianhydride, 2-phenyl-4,4′-diaminodiphenyl ether, and 4-phenylethynylphtalic anhydride

2017 ◽  
Vol 30 (3) ◽  
pp. 347-354 ◽  
Author(s):  
Yuki Kubota ◽  
Takefumi Furuta ◽  
Yuichi Ishida ◽  
Rikio Yokota ◽  
Masahiko Miyauchi ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Degradation Process ◽  
Small Degree ◽  
Pyromellitic Dianhydride ◽  
Chain Extension ◽  
Cure Reaction ◽  
Excellent Thermal Stability ◽  
Dimensional Changes ◽  
A Chain

The previously developed TriA-X polyimide resin, consisting of pyromellitic dianhydride/2-phenyl-4,4′-diaminodiphenyl ether; 9,9-bis(4-aminophenyl)fluorene/4-phenylethynylphthalic anhydride (PEPA), was exposed for 3000 h to air at 180, 240, and 270°C or a vacuum environment at 270°C, in order to study its long-term thermal stability. The weight loss and dimensional changes were measured. Elemental analysis was also conducted in order to estimate the TriA-X degradation process. The TriA-X exhibited excellent thermal stability at 180°C and a very small degree of degradation at 240°C, with the degradation becoming significant at 270°C. The latter was primarily dominated by the oxidation of a chain-extension moiety formed by the cure reaction of the end-cap PEPA.

Effect of Long-Term Aging on Microstructure and Mechanical Properties of a Wrought Ni-Base Superalloy

2015 ◽  
Vol 816 ◽  
pp. 546-550
Author(s):  
Chao Yuan ◽  
Huan Wang ◽  
Jian Ting Guo ◽  
He Yong Qin
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Room Temperature ◽  
Excellent Thermal Stability ◽  
Good Thermal Stability ◽  
Increasing Trend ◽  
Size And Morphology ◽  
Strength And Plasticity ◽  
Base Superalloy

During long-term and high temperature service, microstructures of superalloys may change and then have an adverse impact on mechanical properties, so the stabilities of a wrought Ni-base superalloy aging without stress at 650°C were investigated in this paper. The results showed that the size and morphology of γ' precipitates in the alloy were not obviously influenced with the increase of exposure time, and primary MC carbides present excellent thermal stability. Moreover, almost no detrimental phase was found. Tensile strength and plasticity at room temperature after aging remained steady. Under the condition of 650°C/823MPa, the stress ruptures life presented increasing trend overall and plasticity decreases slightly. In conclusion, the experiment alloy presents a good thermal stability at 650°C.

Structure and Properties of PM Nano-Crystalline Al-Cr based Alloys

2007 ◽  
Vol 567-568 ◽  
pp. 197-200
Author(s):  
Dalibor Vojtěch ◽  
Alena Michalcová ◽  
Jan Verner ◽  
Jan Šerák ◽  
František Šimančík ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Elevated Temperature ◽  
Tensile Tests ◽  
Paper Properties ◽  
Excellent Thermal Stability ◽  
Nano Crystalline ◽  
Rapidly Solidified ◽  
Thermal Stability Of ◽  
Powder Fraction

In the presented paper, properties of Al-Cr-Fe-Ti alloy produced by powder metallurgy (PM) are described. Rapidly solidified powder alloy was prepared by the pressure nitrogen melt atomization. The granulometric powder fraction of less than 45 μm was then hot-extruded. Microstructure of the as-extruded material comprised recrystallized α-Al grains and spheroids of intermetallic phases. Tensile strength of the investigated material was similar to that of a conventional casting Al-Si alloy commonly used in elevated temperature applications. Excellent thermal stability of the PM Al-Cr based material, which much exceeded the elevated temperature casting alloy, was proved by room temperature tensile tests after long-term annealing at elevated temperature. Reasons for the observed thermal stability of the investigated PM alloy are discussed.

scholarly journals Bio-Based Bisbenzoxazines with Flame Retardant Linker

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4330
Author(s):  
Thorben Sören Haubold ◽  
Laura Puchot ◽  
Antoine Adjaoud ◽  
Pierre Verge ◽  
Katharina Koschek
Keyword(s):  
Thermal Stability ◽  
Flame Retardant ◽  
Ethylene Carbonate ◽  
Ring Closure ◽  
Chain Extension ◽  
Ambient Atmosphere ◽  
Rheological Analysis ◽  
Polymerization Behavior ◽  
A Chain ◽  
Halogen Free

This work explores the strategy of incorporating a highly substituted reactive flame retardant into a benzoxazine moiety. For this purpose, a DOPO-based flame retardant received a chain extension via reaction with ethylene carbonate. It was then reacted with phloretic acid to obtain a diphenol end-capped molecule, and further reacted with furfurylamine and paraformaldehyde to obtain a benzoxazine monomer via a Mannich-like ring closure reaction. This four-step synthesis yielded a partly bio-based halogen-free flame retardant benzoxazine monomer (DOPO-PA-fa). The successful synthesis was proven via NMR, IR and MS analysis. The polymerization behavior was monitored by DSC and rheological analysis both showing the polymerization starts at 200 °C to yield pDOPO-PA-fa. pDOPO-PA-fa has a significant thermal stability with a residual mass of 30% at 800 °C under ambient atmosphere. Furthermore, it reached a V-0 rating against small flames and an OI of 35%. Blended with other benzoxazines, it significantly improves their thermal stability and fire resistance. It emphasizes its potential as flame retardant agent.

A new resin with improved processability and thermal stability

2016 ◽  
Vol 29 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Liping Sheng ◽  
Jingcheng Zeng ◽  
Suli Xing ◽  
Changping Yin ◽  
Jinshui Yang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Synergistic Effect ◽  
Curing Temperature ◽  
Proton Nuclear Magnetic Resonance ◽  
Resonance Spectroscopy ◽  
Curing Time ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Cure Reaction ◽  
Excellent Thermal Stability

To maintain outstanding thermal stability, amino- and hydroxyl-containing phthalonitrile monomers, 4-(4-aminophenoxy)-phthalonitrile (APN) and 4-(4-hydroxyphenoxy)-phthalonitrile (HPN) were selected and synthesized. Their structures were confirmed by proton nuclear magnetic resonance spectroscopy. Their curing polymers were characterized by Fourier transform infrared spectroscopy. The self-catalytic curing behaviors of the monomers were investigated by differential scanning calorimetry (DSC) at different heating rates. From the results, APN exhibits a higher curing temperature, while HPN exhibits a longer curing time. Then, mixtures of these monomers were investigated by DSC. The result shows that the 50/50 mixture exhibits different autocatalytic behaviors: the curing temperature is lower than that of APN and the curing time of the mixture is shorter than that of HPN. Furthermore, thermogravimetric analysis shows that the polymer from the mixture exhibits higher temperature of 5% weight loss ( T5%) and char yield value at 800°C than those of the polymers from each monomer. All these results indicate that the new mixture resin exhibits improved processability with excellent thermal stability, attributed to the synergistic effect between similar monomers; the synergistic effect optimizes the cure reaction kinetics and promotes cross-linking reactions, thereby producing an excellent resin; this approach is a new method for improving the processability without sacrificing thermal stability.

Highly Thermally Stable Light-Weight Al Based Alloys Prepared by Centrifugal Atomization and Powder Compaction

2014 ◽  
Vol 782 ◽  
pp. 347-352
Author(s):  
Dalibor Vojtěch ◽  
Karel Dám ◽  
Filip Průša
Keyword(s):  
Thermal Stability ◽  
Chemical Compositions ◽  
Thermally Stable ◽  
Creep Tests ◽  
Centrifugal Atomization ◽  
Excellent Thermal Stability ◽  
High Concentrations ◽  
Rapidly Solidified ◽  
Compressive Tests

Combination of centrifugal melt spraying and hot die-forging of a rapidly solidified semi-product was presented as a promising and inexpensive method for processing of aluminium based alloys of unconventional chemical compositions, e.g., those containing high concentrations of thermally stabilizing transition metals. In our study, the use of this processing method is illustrated for the Al–23Si–8Fe–5Mn (wt. %) alloy. Structure was examined by LM, SEM, EDS and XRD. Mechanical properties were determined by hardness and compressive tests. Thermal stability was assessed by measuring the hardness development during long-term annealing, elevated temperature compressive tests and creep tests. The research showed that the investigated alloy exhibits excellent thermal stability as compared with commercial thermally stable aluminium alloys currently used in automotive and aerospace industry.

Formation and Characterization of Nanolayered Pd-Based Metal/p-4H SiC Systems with Ohmic Behaviour

2010 ◽  
Vol 10 ◽  
pp. 77-85 ◽  
Author(s):  
Lilyana Kolaklieva ◽  
Roumen Kakanakov ◽  
Efstathios K. Polychroniadis ◽  
Eleni Pavlidou ◽  
Ioannis Tsiaousis ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Surface Roughness ◽  
Thermal Properties ◽  
Structural Analysis ◽  
Surface Morphology ◽  
Barrier Height ◽  
Contact Resistivity ◽  
Excellent Thermal Stability

Three types of nanolayered Pd-based metal/p-4H SiC systems, Au/Pd, Au/Pd/Al and Au/Pd/Ti/Pd have been investigated and compared to Pd monolayered metallization regarding the electrical and thermal properties. The lowest contact resistivity of 2.8x10-5 .cm2 has been achieved with the Au/Pd/Ti/Pd contact. This contact exhibits excellent thermal stability during long-term heating at temperature of 700oC and at operating temperatures up to 450oC. The surface morphology investigation has shown that despite the observed decrease, the palladium agglomeration has been not avoided completely in the same contact. The dominated surface roughness was measured to be 75 nm. However, the formation of dendrites in certain places leads to increase the surface roughness to 125 nm. The structural analysis revealed that palladium silicides are formed at the interface metal/p-4H SiC which affects on decrease of the barrier height in more than two times and conversion of the contact from Schottky into ohmic.

Microstructure studies of tungsten silicide schottky contacts on Gaas

1987 ◽  
Vol 45 ◽  
pp. 328-329
Author(s):  
Yih-Cheng Shih ◽  
E. L. Wilkie
Keyword(s):  
Thermal Stability ◽  
Field Effect Transistors ◽  
Schottky Contact ◽  
Schottky Contacts ◽  
Excellent Thermal Stability ◽  
Barrier Heights ◽  
Gaas Substrates ◽  
Film Adhesion ◽  
Threshold Voltages ◽  
Thermal Stability Of

Tungsten silicides (WSix) have been successfully used as the gate materials in self-aligned GaAs metal-semiconductor-field- effect transistors (MESFET). Thermal stability of the WSix/GaAs Schottky contact is of major concern since the n+ implanted source/drain regions must be annealed at high temperatures (∼ 800°C). WSi0.6 was considered the best composition to achieve good device performance due to its low stress and excellent thermal stability of the WSix/GaAs interface. The film adhesion and the uniformity in barrier heights and ideality factors of the WSi0.6 films have been improved by depositing a thin layer of pure W as the first layer on GaAs prior to WSi0.6 deposition. Recently WSi0.1 has been used successfully as the gate material in 1x10 μm GaAs FET's on the GaAs substrates which were sputter-cleaned prior to deposition. These GaAs FET's exhibited uniform threshold voltages across a 51 mm wafer with good film adhesion after annealing at 800°C for 10 min.

scholarly journals Boosted piezoelectricity with excellent thermal stability in tetragonal NaNbO3-based ceramics

2020 ◽  
Author(s):  
Lu Wang ◽  
Shengdong Sun ◽  
Huajie Luo ◽  
Yang Ren ◽  
Hui Liu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Temperature Stability ◽  
Lead Free ◽  
Excellent Thermal Stability ◽  
Lead Free Ceramics ◽  
Piezoelectric Performance

The realization of high piezoelectric performance and excellent temperature stability simultaneously in lead-free ceramics is the key for replacing Pb-containing perovskites in industry. In this study, large piezoelectric performance (d33...

scholarly journals Co‐Evaporated MAPbI 3 : Excellent Intrinsic Long‐Term Thermal Stability of Co‐Evaporated MAPbI 3 Solar Cells at 85 °C (Adv. Funct. Mater. 22/2021)

2021 ◽  
Vol 31 (22) ◽  
pp. 2170155
Author(s):  
Herlina Arianita Dewi ◽  
Jia Li ◽  
Hao Wang ◽  
Bhumika Chaudhary ◽  
Nripan Mathews ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Solar Cells ◽  
Thermal Stability Of
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