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Effects of the biaxial orientation on the mechanical and optical properties and shrinkage of polyamide 6-66-montmorillonite-nanosilica nanocomposite films
摘要： Polyamide 6–66 (PA6-66)–montmorillonite (MMT)–nanosilica (NS) nanocomposite ?lms were fabricated through a cast ?lm process and then biaxially stretched on a laboratory stretcher. Uniaxial or biaxial stretching induced the elongated conformation of MMT and NS. The b axis of the α crystals and the amorphous phase were revealed to align along the machine direction (MD) after stretching, with the uniaxial orientation playing a more signi?cant role. Furthermore, the crystallinity of PA6-66 stretching increased with the stretching ratio. Uniaxial stretching gave rise to a signi?cantly enhanced tensile strength along the MD, whereas it slightly decreased the mechanical properties along the transverse direction (TD). In contrast, the ?lms subjected to biaxial stretching exhibited more balanced mechanical properties. Uniaxial and biaxial stretching led to decreased transmittance and increased haze in the PA6-66–MMT–NS ?lms; this could have been due to the elongated nanostructure of the two nano?llers, which inhibited the transmission and facilitated the scattering of visible light. The thermal shrinkage of the ?lms increased with increasing stretching ratio, and the biaxially oriented ?lms presented nearly equal shrinkage in the MD and TD. The addition of nano?llers decreased the shrinkage attributed to the mobility inhibition of the polymer chains during heating. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47504.
关键词： packaging,nanostructured polymers,?lms,differential scanning calorimetry (DSC),X-ray
更新于2025-09-19 17:15:36
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Thermo mechanical analyses and characterizations of TiNiCu shape memory alloy structures developed by laser additive manufacturing
摘要： Three di?erent compositions of TiNiCu (Ti50Ni (50?x) Cux (x = 10, 20 and 30)) shape memory alloys (SMA) were developed using an intelligent manufacturing technique of laser additive manufacturing (LAM). Based on a numerical analysis the nature and amount of residual stress ?ow was predicted. By implementing ?nite element method (FEM) with Gaussian distributed volumetric heat source, the deposition process was simulated. The numerical and experimental analyses were at par with each other. The developed samples were subjected to several characterizations in order to determine the best among them. Scanning electron microscopy (SEM), atomic force microscopy (AFM), were used to study the surface morphology of the samples. The mechanical properties were studied using micro-hardness test and compression test. X-Ray di?raction (XRD) was deployed to investigate the crystalline nature of the samples. The phase transformation ability of the samples were determined by di?erential scanning calorimetry (DSC). The SEM revealed the deposition of all three samples to be homogeneous. The AFM results showed the grain size of TiNiCu10 to be 20.12 nm, the smallest among the samples. The micro-hardness and ultimate strength of TiNiCu10 was found to be 242 VHN and MPa respectively. XRD reveals the presence of three step transformation for TiNiCu20 sample. From the results, LAM process was considered as a successful methodology in developing TiNiCu bulk SMA structures. The properties of laser additive manufactured TiNiCu10 was found to be the best among the developed samples.
关键词： DSC,TiNiCu,SEM,XRD,Laser additive manufacturing,Shape memory alloy
更新于2025-09-16 10:30:52
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Selective laser beam melting of polymers: In situ and offline measurements for process adapted thermal characterization
摘要： Selective laser beam melting of polymers has to overcome the borders between pure prototype construction and the manufacturing of serial parts. Therefore, a high level of reproducibility of the generated components must be ensured. Up to now, the thermal history of a component during selective laser beam melting is unknown. Neither the temperature during exposure of one layer nor the temperature development in z- or build direction is detected or even regulated. Therefore, in this study the temperature during laser exposure will be detected in a dual approach. The fundamental material beam interaction will be analyzed with a specific test set up, the so-called Laser-HS-DSC. This allows the detection of material beam interactions in combination with a commercial DSC experiment to analyze whether degradation occurs or not. With in situ infrared measurements in a selective laser beam melting system the maximum temperature during laser exposure can be measured. Finally, the offline Laser-HS-DSC experiments are compared to resulting maximum temperatures during exposure in a selective laser beam melting system. The same tendencies of maximum temperatures with varying energy input are obtained, whereas the maximum levels differ due to the different amount of exposed particles.
关键词： PA12,thermography,Additive manufacturing,process-oriented thermal analysis,process characterization,laser-flash DSC,selective laser melting
更新于2025-09-12 10:27:22
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In situ investigation of precipitation in aluminium alloys via thermal diffusivity from laser flash analysis
摘要： In this work, a commercially available laser flash analysis (LFA) device is used for in situ precipitation monitoring in aluminium alloys by following thermal diffusivity for the first time. The LFA measurement methods and data processing are adapted to allow continuous heating experiments over a wide range of heating rates (0.001–1 K s-1). Methods for LFA temperature calibration and thermal lag correction are suggested. Results of continuous heating of Al Mn0.5Mg0.5 aluminium alloy from the as-cast state are compared to in situ differential scanning calorimetry (DSC) and ex situ transmission electron microscopy. It is shown comparing in situ LFA, and DSC substantially improves the interpretation of superimposed reactions, in particular, the precipitation and dissolution of Mn-containing dispersoids and Mg–Si-containing secondary particles.
关键词： DSC,In situ LFA,Thermal diffusivity,Aluminium alloys,Precipitation,LFA thermal lag correction
更新于2025-09-11 14:15:04
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Investigations of the peritectic reaction and transformation in a hypo-peritectic steel: Using high-temperature confocal scanning laser microscopy and differential scanning calorimetry
摘要： The present work focuses on the peritectic reaction and transformation in a commercial hypo-peritectic steel. This multiple phase transformation was studied by means of the high temperature confocal scanning laser microscopy (HTCSLM) and the di?erential scanning calorimetry (DSC) analysis. The results indicate that the technique of combining HTCSLM and DSC can e?ectively distinguish and characterize the peritectic reaction and transformation. The results of these two methods verify and complement each other in interpreting the peritectic reaction and transformation. In situ observation of HTCSLM reveals that the austenite → δ-ferrite transformation during the continuous heating ?rstly occurred around the inclusion and at austenite grain boundary. The emerging δ/γ interfaces travel through previous γ grains by a ?nger-like morphology. With further heating, the unstable liquid phase formed by the peritectic reaction transforms into the δ-ferrite phases again. These stable δ-ferrite phases subsequently melt into liquid phase. During the peritectic solidi?cation, in situ observation reveals that the peritectic reaction is ?rstly observed to occur at the junction interface of the liquid phase and δ-ferrite phase. The γ intermediate phase propagates and thickens toward the liquid phase side and the δ-ferrite phase side in the subsequent peritectic transformation. The δ-ferrite and γ phases were observed to coexist in solid phase when the peritectic transformation ?nishes. Based on the linear regression of DSC results, it is found that the activation energy of the peritectic reaction is larger than that of the other phase transformations during heating, but it is on the contrary during cooling.
关键词： Peritectic reaction and transformation,In situ observation,DSC measurement,Hypo-peritectic steel,Continuous casting
更新于2025-09-11 14:15:04
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Synthesis and electro-optic properties of novel Y-type polyimide containing nitrothiazolylazodioxyphenyl group
摘要： New Y-type polyimide (5) containing nitrothiazolylazodioxyphenyl groups as nonlinear optical (NLO) chromophores, which are components of the polymer backbone, was prepared and characterized. Polyimide 5 is soluble in common organic solvents such as N,N-dimethylformamide and dimethylsulfoxide. Polyimide 5 shows a thermal stability up to 300 °C in thermogravimetric analysis with glass-transition temperature (Tg) obtained from differential scanning calorimetry near 130 °C. The second harmonic generation (SHG) coefficient (d33) of poled polymer film at the 1064 nm fundamental wavelength is around 2.32 pm/V. The dipole alignment of polymer 5 exhibits a thermal stability even at 5 °C higher than Tg, and there is no SHG decay below 135 °C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.
关键词： thermogravimetric analysis (TGA),NLO,dipole alignment,SHG coefficient,differential scanning calorimetry (DSC),polyimide
更新于2025-09-11 14:15:04
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Investigation of thermal and electrical properties of As–Se glasses modified with Cu using DSC and AC impedance spectroscopy
摘要： Investigations of thermal properties of CuxAs50Se50 ? x chalcogenides were carried out using a differential scanning calorimeter. It was established that copper introduction significantly affects the complexity of structural network. This was indicated by double-stage crystallization process in the compound Cu15As50Se35. Besides α relaxation, all the glasses during heating show β relaxation. The complexity of the network influences the conductivity values and transport properties in a way of higher DC and AC conductivity for the compound with the highest Cu share. Impedance spectra show two semicircles, indicating the existence of two polarization processes in different frequency ranges. The presence of kinetic and as well as diffusion processes in polarization of the samples with x = 10 and 15 at% of Cu strongly affects the unusually high values of the real part of dielectric permittivity in low- and medium-frequency range.
关键词： AC impedance spectroscopy,electrical properties,thermal properties,Cu modification,DSC,As–Se glasses
更新于2025-09-10 09:29:36
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STRUCTURAL AND MECHANICAL CHARACTERIZATION OF DEFORMED POLYMER USING CONFOCAL RAMAN MICROSCOPY AND DSC
摘要： Polymers have various interesting properties, which depend largely on their inner structure. One way to in?uence the macroscopic behaviour is the deformation of the polymer chains, which e?ects the change in microstructure. For analyzing the microstructure of non-deformed and deformed polymer materials, Raman spectroscopy as well as di?erential scanning calorimetry (DSC) were used. In the present study we compare the results for crystallinity measurements of deformed polymers using both methods in order to characterize the di?erences in micro-structure due to deformation. The study is ongoing, and we present the results of the ?rst tests.
关键词： Raman spectroscopy,DSC,crystallinity,deformed polymers
更新于2025-09-10 09:29:36
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Two novel Sm(III) complexes with different aromatic carboxylic acid ligands: Synthesis, crystal structures, luminescence and thermal properties
摘要： Two novel Sm(Ⅲ) complexes, [Sm(3,4-DMBA)3(3,4-DMHBA)(5,5′-DM-2,2′-bipy)]2 (1), [Sm(3-MOBA)3(5,5′-DM-2,2′-bipy)]2 (2) (3,4-dimethylbenzoic acid = 3,4-DMHBA, 3-methoxybenzoic acid = 3-MOHBA and 5,5′-dimethyl-2,2′-bipyridine = 5,5′-DM-2,2′-bipy), have been successfully synthesized and assembled. The crystal structures were determined by single crystal X-ray diffraction. Two complexes were characterized by the elemental analysis, IR, powder X-ray diffraction, thermal gravimetric technology. Because of the different ligands, the structures of the two complexes are very different, especially the structure of the complex 1. Each central Sm(Ⅲ) ion of complex 1 was coordinated by three deprotonated 3,4-DMBA-,one unprotonated 3,4-DMHBA and one 5,5′-DM-2,2′-bipy, which has rarely been reported before. However each central Sm(Ⅲ) ion of complex 2 was only coordinated via three deprotonated 3-MOBA- and one 5,5′-DM-2,2′-bipy. In addition, the thermal decomposition mechanism and the three-dimensional infrared accumulation spectra of the evolved gas during the thermal decomposition for two complexes were studied by the simultaneous TG/DSC-FTIR technology. What′s more, the luminescence properties of two complexes were also discussed. Finally, the bacteriostatic activities of two complexes were evaluated against Staphlococcus aureus, Escherichia coli and Candida albicans.
关键词： TG/DSC-FTIR,Crystal structure,Bacteriostatic activities,Lanthanide complexes,luminescence
更新于2025-09-10 09:29:36
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Thermal behaviour of poly(methyl methacrylate)/fullerene composite films
摘要： Poly(methyl methacrylate)/fullerene composite films were fabricated by casting from toluene solutions. The mass fraction of fullerene (C60) was varied from 0.05–3 wt. %. The effect of the fullerene (C60) content on the thermal degradation parameters of the composite films was evaluated by thermogravimetric (TG) analysis. It was found that the incorporation of C60 improved the thermal stability of the polymers. The films eventually decomposed in three stages. Incorporation of fullerene caused a change in the distribution of mass loss over the stages of degradation in comparison with the pristine polymer. Using differential scanning calorimetry (DSC), the phase transitions from the glassy state to the elastic one was studied for the examined polymeric materials. New data relating to the effect of C60 on the glass transition temperature of composites with low weight fractions of filler were obtained. Specifically, for films containing up to 0.1 wt. % of C60, a single glass transition temperature was found, whereas for composites with a higher concentration of filler, two glass transition temperatures were recorded.
关键词： Composite materials,thermogravimetric (TG) analysis,glass transition,DSC,fullerenes,thermal stability
更新于2025-09-09 09:28:46