Ordering of the α-Fe(Si) Crystallization Phase in Annealed Fe_(73.5)Cu_1Mo_3Si_(13.5)B_9 Alloy

The ordering of the α-Fe(Si) crystallization phase in annealed Fe73.5Cu1Mo3Si13.5B9 alloy has been studied using XRD method. The α-Fe(Si) phase in Fe73.5Cu1Mo3Si13.5B9 alloy annealed at 460℃ for 1 h consists of the DO3-type ordered region with spherical shape and disordered region. The size of DO3 ordered region increases with the annealing temperature. When the annealing temperature is 560℃, the size of the ordered region in the α-Fe(Si) grain is 14.0nm,which is nearly as large as that of the α-Fe(Si) grain (14.2 nm) and the degree of order of the α-Fe(Si) phase is about 0.78. When Fe73.5Cu1 Mo3Si13.5B9 amorphous alloy is annealed at 520℃， with the increment of the annealing time, the shape of the DO3 ordered region in the α-Fe(Si) phase is spheroidal at the beginning of the annealing and becomes spherical and has asize of 12.8 nm when the annealing time is 60 min. In addition, the DO3 superlattice lines of the α-Fe(Si) phase will vanish if Fe73.5Cu1Mo3Si13.5 B9 amorphous alloy is annealed for 1 h at 750℃.

A Reproducible Approach of Preparing High-Quality Overdoped Bi_2Sr_2CaCu_2O_(8+δ) Single Crystals by Oxygen Annealing and Quenching Method

We report a reproducible approach in preparing high-quality overdoped Bi2 Sr2 CaCu2 08＋δ （Bi2212） single crystals by annealing Bi2212 crystals in high oxygen pressure followed by a fast quenching. In this way, high-quality overdoped and heavily overdoped Bi2212 single crystals are obtained by controlling the annealing oxygen pressure. We find that, beyond a limit of oxygen pressure that can achieve most heavily overdoped Bi2212 with a Tc N63 K, the annealed Bi2212 begins to decompose. This accounts for the existence of the hole-doping limit and thus the Tc limit in the heavily overdoped region of Bi2212 by the oxygen annealing process. These results provide a reliable way in preparing high-quality overdoped and heavily overdoped Bi2212 crystals that are important for studies of the physical properties, electronic structure and superconductivity mechanism of the cuprate superconductors.

Enhanced αγ′ Transition of Poly(vinylidene fluoride) by Step Crystallization and Subsequent Annealing

Poly（vinylidene fluoride）（PVDF） exhibits pronounced polymorphs. Its γ phase is attractive due to the electroactive properties. The γ-PVDF is however difficult to obtain under normal crystallization condition. In a previous work, we reported a simple melt-recrystallization approach for producing γ-phase rich PVDF thin films through selective melting and subsequent recrystallization. We reported here another approach for promoting the αγ′ phase transition to prepare γ-phase rich PVDF thin films. To this end, a stepwise crystallization and subsequent annealing process was used. The idea is based on a quick generation of a large amount of α-PVDF crystals with some of their γ-PVDF counterparts at suitable crystallization temperature and then annealing at a temperature above the crystallization temperature for enhancing the molecular chain mobility to overcome the energy barrier of phase transition. It was found that crystallizing the PVDF melt first at 152 °C for 4 h, then quenching to room temperature and finally annealing the sample at 160 °C for 100 h was the most efficient to produce γ-PVDF rich films. This is related to the melting and recrystallization of the α-PVDF crystals produced during quenching in the annealing process at 160 °C, which favors the formation of γ-PVDF crystals for triggering the αγ′ phase transition.

Transmission Spectral Characteristics of Photonic Crystals Milled in Annealed Proton-Exchange LiNbO_3 Waveguide

Transmission spectra of triangular lattice photonic crystals milled in the top surface of an annealed proton- exchange waveguide are numerically simulated. The effects of the finite depth, conical shape, trapezoidal shape and hybrid shape of holes are theoretically analyzed. Due to the difficulty of milling high aspect-ratio cylindrical holes in lithium niobate （LiNbO3 ）, a compromised solution is proposed to improve the overlap between shallow holes and the waveguide mode, and useful transmission spectra with strong contrast and sharp band edges are achieved.

Differences in the structure and magnetic properties of(Nd0.75Pr0.25)9.5Fe76X4B10.5(X=Nb, Zr) ribbons by conventional and microwave-assisted annealing treatment

Amorphous ribbons with（Nd_（0.75）Pr_（0.25））_（9.5）Fe_（76）X_4B_（10.5）（X=Nb, Zr） nominal composition were annealed by conventional and microwave-assisted annealing furnaces, respectively. The thermal decomposition process, structure and magnetic properties of products were characterized by a thermal differential scanning calorimeter（DSC）, X-ray diffraction（XRD） and a vibrating sample magnetometer（VSM）. The addition of Nb and Zr increased the glass-forming ability（GFA） of as-spun ribbons. The proportion of Nd_2Fe_（14）B and α-Fe could be adjusted with power from 800 to 2000 W in microwave annealing process, during which the well-coupling between the soft and hard magnetic phase and higher coercivity reached up to 780.2 and 815.4 kA/m for（Nb,Zr）-doped alloys. The best magnetic properties of ribbons could be obtained by annealing at 650 oC for 10 min under the microwave power of 2000 W.

Further Understanding on the Three Domains of Isotactic Polypropylene by Investigating the Crystalline Morphologies Evolution after Treatment at Different Domains

The introduction of concept of the three domains of isotactic polypropylene（iPP） by Wittmann and Lotz et al. is an important advance in understanding the influence of the melt structures on the crystallization behaviors and consequent properties. To further understand the physical nature of the melt structures, the crystalline structures of i PP after thermal treatment in the three domains are systematically investigated. It is found that after treated at different domains the crystal morphologies, including the sizes and birefringence of spherulitic, the proportion of radial and tangential lamellae, etc., have distinctly different features. Our study reveals that the ＂nuclei＂ at domain II compose of locally ordered chains and the induced memory effect could not be erased under annealing treatment, while the ＂nuclei＂ at domain III compose of crystal fragments, which will aggregate under annealing process. Based on our results, highly schematic diagrams are proposed to illustrate the probable physical characteristics of the melt structures at the three different domains.