partial crystallization
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Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 564
Author(s):  
Beate Capraro ◽  
Manuel Heidenreich ◽  
Jörg Töpfer

We have studied the sintering behavior of CT708 LTCC tapes with large CTE of 10.6 ppm/K. This low-k dielectric LTCC material is a quartz-based glass ceramic composite system with partial crystallization of celsian upon firing. The shrinkage, densification and dielectric properties were examined using different heating rates and a sintering temperature of 900 °C. The maximum shrinkage rate is at 836 °C (for a heating rate of 2 K/min) with a sintering density of 95% and a permittivity of ε’ = 5.9 and tan δ = 0.0004 (at 1 GHz). Due to their similar shrinkage and thermal expansion properties, CT708 tapes may be cofired with functional ceramic layers. As an example, we report on cofiring of a multilayer laminate of CT708 and a Sc-substituted hexagonal ferrite for applications as integrated microwave circulator components. This demonstrates the feasibility of cofiring of functional ceramic tapes and tailored LTCC tapes and documents the potential for the realization of complex LTCC multilayer architectures.


Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3532
Author(s):  
Alireza Zare ◽  
Borja Pascual-Jose ◽  
Silvia De la De la Flor ◽  
Amparo Ribes-Greus ◽  
Xavier Montané ◽  
...  

Dendronized polyethers give rise to columnar LC structures which can successfully act as cation transport materials. Therefore, we prepared two different materials, based on Poly(epichlorohydrin-co-ethylene oxide) (PECH-co-EO) grafted with methyl 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy] benzoate, containing 20% or 40% modified units, respectively. The obtained polymers were characterized by differential scanning calorimetry (DSC), X-ray diffraction and optical microscopy between crossed polars (POM) and compared to the unmodified PECH-co-EO. In order to reach efficient transport properties, homeotropically oriented membranes were prepared by a fine-tuned thermal annealing treatment and were subsequently investigated by dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA). We found that the presence of the dendrons induces a main chain partial crystallization of the polyether chain and coherently increases the polymer Tg. This effect is more evident in the oriented membranes. As for copolymer orientation upon annealing, the cooling rate and the annealing temperature were the most crucial factors. DMTA and DETA confirmed that grafting with the dendron strongly hinders copolymer motions, but did not show great differences between unoriented and oriented membranes, regardless of the amount of dendrons.


2021 ◽  
Vol 27 (S1) ◽  
pp. 400-402
Author(s):  
Alicia Koenig ◽  
David Tweddle ◽  
Alex Leary ◽  
Ronald Noebe ◽  
Claudia Mewes ◽  
...  

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ganesh Shete ◽  
Sushil Mishra ◽  
Shyamprasad Karagadde ◽  
Atul Srivastava

AbstractThe present work reports real-time observations of the phenomena of partial crystallization of one of the glass-forming materials, namely enstatite (MgSiO3) from its supercooled liquid droplet. Initially, the molten droplet has been held under purely non-contact conditions using the aerodynamic levitation technique. The desired levels of undercooling have been achieved by deliberately making the levitated molten droplet touch a thin molybdenum wire and hence to initiate heterogeneous nucleation from the point of contact. Influence of thermal parameters like undercooling, cooling rates and recalescence on the process of crystallization is investigated. To understand and report the morphological properties and extent of crystallinity, the solidified enstatite samples have been characterized using optical/scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively, which confirmed the formation of partially crystallized enstatite spherules and fully glass spherules. XRD showed sharp peaks of enstatite, which confirm crystallinity and a halo profile confirms the amorphous phase of enstatite. Based on the observations of several experiments, we propose the effect of thermal parameters such as levels of undercooling and recalescence on the partial crystallization, as well as partial glass formation from the initially molten droplets of enstatite composition.


Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1024
Author(s):  
Jingjing Peng ◽  
Changshan Hao ◽  
Hongyan Liu ◽  
Yue Yan

Highly transparent indium-free multilayers of TiO2/Cu/TiO2 were obtained by means of annealing. The effects of Cu thickness and annealing temperature on the electrical and optical properties were investigated. The critical thickness of Cu mid-layer with optimal electrical and optical properties was 10 nm, with the figure of merit reaching as high as 5 × 10−3 Ω−1. Partial crystallization of the TiO2 layer enhanced the electrical and optical properties upon annealing. Electrothermal experiments showed that temperatures of more than 100 °C can be reached at a heating rate of 2 °C/s without any damage to the multilayers. The experimental results indicate that reliable transparent TiO2/Cu/TiO2 multilayers can be used for electrothermal application.


Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1142
Author(s):  
Yasuhiko Shimotsuma ◽  
Kotaro Tomura ◽  
Tatsuya Okuno ◽  
Masahiro Shimizu ◽  
Kiyotaka Miura

Direct three-dimensional laser writing of crystallization inside glass has been intensely studied as an attractive technique for fabricating photonic devices. In particular, polarization-dependent periodic nanostructures composed of the partial crystallization in glass can be self-assembled through focused irradiation of femtosecond pulses. Here, we report on the Y3Al5O12 (YAG) crystal precipitation in nanoscale by femtosecond laser irradiation inside Al2O3-Y2O3 glass. Furthermore, we focus on the white emission by Ce: YAG in which a part of Y3+ site was replaced by Ce3+, the effect on photoluminescence (PL) characteristics by changing of ligand field induced by nanostructure formation was observed.


Friction ◽  
2020 ◽  
Author(s):  
Wanjun He ◽  
Qunfeng Zeng

Abstract The microstructure, mechanical and micro/nano-tribological properties of the 60NiTi film annealed at different temperature were investigated. The results reveal that annealing as-deposited 60NiTi film at 300, 375, and 600 °C for 1 h leads to structural relaxation, partial crystallization and full crystallization, respectively. Compared with the structurally relaxed structure, the partially crystallized structure exhibits increased hardness but decreased elastic modulus. This is because that the elastic modulus is reduced by Voigt model while the hardness is improved by composite effect. Due to the highest hardness and ratio of hardness to elastic modulus (H/E), the partially crystallized 60NiTi film has the lowest penetration depth and residual depth (i.e., groove depth). Besides, the results also reveal that ductile plowing is the dominant wear mechanism for all the annealed 60NiTi films. Under the condition of the ductile plowing, coefficient of friction and wear resistance are related to penetration depth and residual depth, respectively. Therefore, the partially crystallized 60NiTi film shows the best tribological performance at the micro/nano-scale. The current work not only highlights the important roles of hardness and H/E in improving the micro/nano-tribological properties but also concludes an efficient and simple method for simultaneously increasing hardness and H/E.


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