Micro-Structure Changes Caused by Thermal Evolution in Chalcogenide GexAsySe1−x−y Thin Films by In Situ Measurements

To understand the effects of thermal annealing on the structure of GexAsySe1−x−y thin films, the thermal evolution of these films was measured by the in situ X-ray diffraction (XRD) at different temperature (773 K or 1073 K) in a vacuum (10−1 Pa) environment. The entire process of crystallization can be observed by using in situ XRD, which is from the appearance of a crystal structure to melting liquid-state and ultimately to the disappearance of the amorphous structure. In the crystallized process, the corresponding state-transition temperatures Tx (the onset crystallization temperature), Tl (the transition temperature from glassy-state to liquid-state), Tp (peak crystallization temperature) are linear with MCN (Mean Coordination Number). In order to obtain information about changes in the amorphous structural origin of the anneal-induced material, the samples were analyzed by in situ Raman spectroscopy. Analysis of the results through decomposing the Raman spectra into different structural units showed that the Ge−Ge, As−As, or Se−Se homopolar bonds as the nonequilibrium minority carriers could be found in films. It suggests that the formation of these bonds cannot be completely suppressed in any case, as one falls and another rises.

Effect of 1,4-Naphthalenedicarboxylic Acid Derivative on Crystallization and Performances of Poly(L-lactide)

In this work, biodegradable Poly(L-lactide) (PLLA) was modified through adding a new organic additive N, N -bis(benzoyl) 1, 4-naphthalenedicarboxylic acid dihydrazide (NABH). A comparison on crystallization of the pure PLLA and PLLA/NABH revealed that the NABH as effective heterogeneous nucleation sites enhanced PLLA𠏋 crystallization, and an increase of NABH loading was able to further accelerate crystallization rate of PLLA; whereas a faster cooling rate was not conducive to PLLA𠏋 crystallization, but the appearance of obvious crystallization peak upon cooling at 30şC/min confirmed the advanced enhancing role of NABH for PLLA crystallization again. The investigation on influence of the final melting temperature on the crystallization behavior of PLLA showed that the 170 şC was optimum final melting temperature for enhancing crystallization, even the onset crystallization temperature of PLLA/NABH were higher than 150şC. The melting processes of PLLA/NABH after different crystallization not only could reflect the previous crystallization, but also depended on crystallization temperature and heating rate. Thermal decomposition results showed that the existence of NABH slightly weakened thermal stability of PLLA, and the maximum difference in onset thermal decomposition temperature was only 9.4şC comparing with the pure PLLA. However, the presence of NABH in PLLA matrix seriously weakened optical property.

Insight into the Role of a Isophthalic Dihydrazide Derivative Containing Piperonylic Acid in Poly(L-lactide) Nucleation: Thermal Performances and Mechanical Properties

This work was aimed at synthesizing the N, N -isophthalic bis(piperonylic acid) dihydrazide (PAID) to be as a new crystallization accelerator for poly(L-lactide) (PLLA), and a detailed investigations of the non-isothermal crystallization, melting behavior, thermal decomposition behavior and mechanical properties of PLLA nucleated by PAID were performed applying differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and electronic tensile tester. The melt-crystallization proved that the PAID could act as a heterogeneous nucleating agent to significantly promote the crystallization in cooling, even the crystallization was still able to be accelerated upon the fast cooling at 50 oC/min. The final melt temperature was another crucial factor for PLLA�s melt crystallization, and when the final melt temperature was 170 oC, the onset crystallization temperature and melt-crystallization enthalpy was almost up to 150 oC and 56.8 J/g upon cooling of 1 oC/min, respectively. Furthermore, the chemical nucleation was proposed to be the nucleation mechanism of PAID for PLLA via the preliminary theoretical calculation. For the cold-crystallization, the addition of PAID exhibited an inhibition for the crystallization of PLLA, but the total crystallization process depended on the heating rate and PAID concentration. The single melting peak after cooling of 1 oC/min indicated that the crystallization had been thoroughly completed in cooling. Additionally, the single melting peak with different locations after full crystallization resulted from the different crystallization temperatures. A comparison in the onset decomposition temperature implied that the presence of PAID only slightly decreased the thermal stability of PLLA. The mechanical testing showed that, in contrast with the elongation at break, the existence of PAID enhanced the tensile strength of PLLA.

Эффективные коэффициенты диффузии и термическая устойчивость структуры металлического стекла Fe-=SUB=-48-=/SUB=-Co-=SUB=-32-=/SUB=-P-=SUB=-14-=/SUB=-B-=SUB=-6-=/SUB=-

The values of linear growth velocities of the eutectic colonies in the temperature range of 679–717 K have been determined for the first time from the electron microscopic studies of the partially crystallized samples of Fe48Co32P14B6 metallic glass. Using these data, the values of the effective diffusion coefficients governing growth have been calculated. It has been established that the temperature dependence of the effective diffusivity in Fe48Co32P14B6 glass is well approximated by an Arrhenius law and their values in the temperature range of crystallization are about 2–3 orders of magnitude smaller than those in the Fe40Ni40P14B6 commercial glass. The values of the effective diffusion coefficients at the onset crystallization temperature have been determined, the correlation between pre-exponential factors and activation energies has been found. It has been shown that the parameters which characterize the effective diffusivity in the glass investigated are in good agreement with the published data for the eutectically crystallizing metallic glasses. It has been established that the physical reason of the enhanced thermal stability of the FeCo-based glass compared with that of Fe40Ni40P14B6 is the lower atomic mobility at the glass/crystal interface.

Correlated Unique Variation of Electrical Resistivity to Crystallization Behavior of the Zr52.5Cu17.9Ni14.6Al10Ti5 Metallic Glass

Due to the differences between the glass and crystalline phases, crystallization of metallic glass occurs with heat release, volume shrinkage, and electrical resistivity drastic changes. Electrical resistivity of the Zr52.5Cu17.9Ni14.6Al10Ti5 metallic glass during crystallization was investigated under both continuous heating and isothermal annealing. This amorphous alloy exhibits a continuous variation instead of sharp decline when reaches the onset crystallization temperature. This unique variation was found to be related to the formation of a few quasicrystalline phases. The slower phase transformation process of this metallic glass brings lots of grain boundaries, which results in increasing of resistivity at the last stage during isothermal annealing. These results imply that electrical resistivity measurement is a more intuitive approach to investigate structure evolution of metallic glasses.

Crystallization, mechanical and electrochemical behavior of Al-Ce-TM (TM = Fe, Co, Ni and Cu) amorphous alloys

Al86Ce10TM4 amorphous alloys (TM=Fe, Co, Ni and Cu) were fabricated using melt-spin fast-quenching method. The crystallization, mechanical and electrochemical behavior of the as-spun and the post-annealed alloys were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), micro-indentation and electrochemical techniques. It was found the completely amorphous Al86Ce10TM4 alloys (TM=Fe, Co, Ni and Cu) go through two crystallization processes, where the first exothermal peak represents nucleation of nano-crystalline particles and the second exothermal peak signifies growth of the nano-crystalline precipitates. Both the nucleation and growth processes rely on diffusion-controlled mechanism. The first onset crystallization temperature Tx1 associated with activation energy E1 and frequency factor Ko1 can be used to evaluate the thermal stability of the amorphous alloys while the second onset crystallization temperature Tx2 associated with activation energy E2 and frequency factor Ko2 can be taken to judge the thermal stability of ideal amorphous-nanocrystalline mixed structure in sustaining optimized mechanical and electrochemical properties. The as-spun and post-annealed alloys exhibit higher mechanical hardness (860~1180 MPa), corrosion resistance (10-8A/cm2 ) and high temperature endurance (284, 300 and 420°C for Al86Ce10Co4 , Al86Ce10Ni4 andAl86Ce10Fe4 , respectively) compared to hardness 500~600 MPa, corrosion resistance 10-7A/cm2 and high temperature durability 200°C of traditional Al crystalline alloys, manifesting the value on scientific studies and engineering applications of the Al86Ce10TM4 amorphous alloys.

Investigating the Effect of Nanoclay Loadings and Re-Processing on the Melting and Crystallization Behavior of PP/Clay Nanocomposites

In this study, PP/clay nanocomposites have been fabricated at different nanoclay loadings, i.e. 0, 5, 10, and 5 wt% for the 1stcycle and 2ndcycle (re-processing). The prepared nanocomposites were then characterized by a Differential Scanning Calorimetry (DSC) to investigate the effects of nanoclay loadings and re-processing on the melting and crystallization of the nanocomposites. The DSC results showed that the melting temperature,Tmwas not significantly affected by the nanoclay loadings and re-processing. In the other hand, the degree of crystallinity,Xcof the nanocomposites was higher than that of neat PP, but only reached a maximum at nanoclay loading of 5 wt% (i.e. 51.2% for NC-5-I and 48.3% for NC-5-II). Thereafter, theXcdecreased at higher nanoclay loadings. There was no significant difference inXcbetween 1stcycle and 2ndcycle. Additionally, in all nanocomposites samples for both cycles, there were two crystallization temperatures, i.e.Tc1andTc2. In the overall crystallization process, theTcof nanocomposites increased by 11-12°C compared to that of neat PP. Whereas, the onset crystallization temperature,Tocalso increased by approx. 13°C. Apparently, there was no significant effect of nanoclay loadings and re-processing on theTcndTocof the nanocomposites.

Thermal behavior of modified poly(L-lactic acid): effect of aromatic multiamide derivative based on 1H-benzotriazole

The goal of this work was to synthesis a novel aromatic multiamide derivative based on 1H-benzotriazole (PB) as an organic nucleating agent for poly(L-lactic acid) (PLLA), and investigate the effect of PB on the non-isothermal crystallization, melting behavior and thermal decomposition of PLLA. Here, PB was firstly synthesized through 1H-benzotriazole aceto-hydrazide and terephthaloyl chloride, then PB-nucleated PLLA was fabricated via melt-blending technology at various PB concentration from 0.5 wt% to 3 wt%. Finally, the thermal performances were evaluated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The high thermal decomposition temperature of PB indicated that PB possessed possibility as a nucleating agent for PLLA, and the non-isothermal crystallization behavior confirmed the crystallization accelerating effectiveness of PB for PLLA. Upon optimum concentration of 2 wt%, the onset crystallization temperature, the crystallization peak temperature and the non-isothermal crystallization enthalpy increased from 101.4°C, 94.5°C and 0.1 J·g-1 to 121.3°C, 115.8°C and 35.1 J·g-1, respectively. In addition, the non-isothermal crystallization behavior was also affected by the cooling rate and the final melting temperature. The melting behavior further evidenced the advanced nucleating ability of PB, and the competitive relationship between PB and the heating rate, the nuclear rate and crystal growth rate. Thermal stability measurement showed that PB with a concentration of 1 wt%–2 wt% could slightly improve the thermal stability of PLLA.

Glass Formation and Thermal Stability of Mechanically Alloyed Al75Ni10Ti10Zr5 Amorphous Composites with Graphene Addition

In this study, the influence of 0.5 wt.% graphene (Gr) addition on the glass formation and thermal stability of the Al75Ni10Ti10Zr5 alloy during mechanical alloying (MA) process has been investigated. The as-milled products consist of the amorphous phase and a small amount of the AlNi nanocrystals. The results showed that the 0.5 wt.% Gr addition could shorten the amorphization process, indicating the enhancement of the glass forming ability. Moreover, the onset crystallization temperature (Tx1) slightly decreased with prolonging milling time for the as-milled alloys. However, it is worth noting that the Gr addition effectively increased the Tx1 of the as-milled Al-based amorphous composites for the long duration of MA time. The Tx1 values of the as-milled AlNiTiZrGr amorphous composites were more than 1120 K, exhibiting the highly thermal stability.

Crystallization Behavior and Thermal Analysis of CoFeB Thin Films

We examined two targets containing Co40Fe40B20and Co60Fe20B20. We deposited Co40Fe40B20and Co60Fe20B20monolayer thin films of various thicknesses on glass substrates through DC magnetron sputtering; the thicknesses ranged from 25 to 200 Å. The thermal properties of the Co40Fe40B20and Co60Fe20B20thin films were determined using a differential scanning calorimeter (DSC). The thermal properties included the glass transition temperature (Tg), onset crystallization temperature (Tx), and glass-forming ability, which were determined according to these values. Using the Kissinger formula revealed that the activation energy of the Co60Fe20B20with a thickness of 75 Å is the highest, implying that crystallization was the lowest and the Co60Fe20B20film showed anticrystallization properties. However, the energy of 75 Å Co40Fe40B20thin films was the lowest, which is opposite to that of Co60Fe20B20. This observation can be reasonably explained based on the concentration of Co or Fe. Therefore, a thickness of 75 Å is critical.