Showing papers on "Differential scanning calorimetry published in 2012"
TL;DR: NLCs demonstrated faster drug release than SLNs at low drug-loading, whereas there was no significant difference in drug release from SLNs and NLCs at high drug- loading, however, sustained/prolonged drug release was observed from both formulations.
433 citations
TL;DR: In this paper, the precursors of Li4Ti5O12 were characterized by thermogravimetry and differential scanning calorimetry using X-ray diffraction, transmission electron microscopy (TEM) and electrochemical measurements.
Abstract: Spinel Li4Ti5O12 nanoparticles were prepared via a high-temperature solid-state reaction by adding the prepared cellulose to an aqueous dispersion of lithium salts and titanium dioxide. The precursors of Li4Ti5O12 were characterized by thermogravimetry and differential scanning calorimetry. The obtained Li4Ti5O12 nanoparticles were characterized using X-ray diffraction, transmission electron microscopy (TEM) and electrochemical measurements. The TEM revealed that the Li4Ti5O12 prepared with cellulose is composed of nanoparticles with an average particle diameter of 20–30 nm. Galvanostatic battery testing showed that nano-sized Li4Ti5O12 exhibit better electrochemical properties than submicro-sized Li4Ti5O12 do especially at high current rates, which can deliver a reversible discharge capacity of 131 mAh g−1 at the rate of 10 C, whereas that of the submicro-sized sample decreases to 25 mAh g−1 at the same rate (10 C). Its reversible capacity is maintained at ~172.2 mAh g−1 with the voltage range 1.0–3.0 V (vs. Li) at the current rate of 0.5 C for over 80 cycles.
431 citations
TL;DR: Differential scanning calorimetry (DSC) is widely used to study the stability of amorphous solids, characterizing the kinetics of crystallization close to the glass-transition temperature Tg as discussed by the authors.
Abstract: Differential scanning calorimetry (DSC) is widely used to study the stability of amorphous solids, characterizing the kinetics of crystallization close to the glass-transition temperature Tg. We apply ultrafast DSC to the phase-change material Ge2Sb2Te5 (GST) and show that if the range of heating rates is extended to more than 104 K s-1, the analysis can cover a wider temperature range, up to the point where the crystal growth rate approaches its maximum. The growth rates that can be characterized are some four orders of magnitude higher than in conventional DSC, reaching values relevant for the application of GST as a data-storage medium. The kinetic coefficient for crystal growth has a strongly non-Arrhenius temperature dependence, revealing that supercooled liquid GST has a high fragility. Near Tg there is evidence for decoupling of the crystal-growth kinetics from viscous flow, matching the behaviour for a fragile liquid suggested by studies on oxide and organic systems.
388 citations
TL;DR: In this paper, the paraffin/expanded graphite (EG) composite phase change material (PCM) was prepared by absorbing liquid Paraffin into the expanded graphite, in which paraffIN was chosen as the PCM.
379 citations
TL;DR: In this article, a mixture of polyvinyl alcohol (PVA) and hydroxypropyl cellulose (HPC) was used as bio-equivalent materials for thermal analysis.
Abstract: Polymers and polymeric composites have steadily reflected their importance in our daily life. Blending poly(vinyl alcohol) (PVA) with a potentially useful natural biopolymers such as hydroxypropyl cellulose (HPC) seems to be an interesting way of preparing a polymeric blends. In the present work, blends of PVA/HPC of compositions (100/0, 90/10, 75/25, 50/50, 25/75, and 0/100 wt/wt%) were prepared to be used as bioequivalent materials. Thermal analyses [differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)], and X-ray diffraction (XRD) were employed to characterize and reveal the miscibility map and the structural properties of such blend system. The obtained results of the thermal analyses showed variations in the glass transition temperature (Tg) indicating the miscibility of the blend systems. Moreover, the changes in the melting temperature (Tm), shape and area were attributed to the different degrees of crystallinity and the existence of polymer-polymer interactions between PVA and HPC molecules. The X-ray diffraction (XRD) analysis showed broadening and sharpening of peaks at different HPC concentrations with PVA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo-polymers PVA and HPC is possible. The results showed that HPC doped in PVA film can improve the thermal stability of the film under investigation, leading to interesting technological applications.
247 citations
TL;DR: In this article, nano-sized CuO, Co 3 O 4 and CuCo 2 O 4 powders were prepared via different methods such as co-precipitation, thermal decomposition of oxalate precursor and sol-gel and their catalytic activities towards thermal deformation of ammonium perchlorate.
234 citations
TL;DR: In this paper, a one-step combustion method using urea and titanyl nitrate as the fuel and oxidizer, respectively, was used to synthesize Graphene oxide (GO) and TiO2 hybrid materials with enhanced photocatalytic properties.
218 citations
TL;DR: In this paper, a nanocapsule containing phase change material (PCM) n-dodecanol as core and polymethyl methacrylate (PMMA) as shell was synthesized by mini-emulsion polymerization with polymerizable emulsifier DNS-86 and co-emulsifier hexadecane (HD).
202 citations
TL;DR: In this paper, the effect of lignin incorporation in the presence and absence of compatibilizer (maleic anhydride grafted polypropylene, PP-g-MA) was investigated by means of mechanical, thermal and morphological properties.
202 citations
TL;DR: In this article, a thermally induced phase separation (TIPS) method was used for the preparation of PVDF/TiO 2 hybrid microfiltration membranes with different nano-TiO2 dosage, and DMP was used as a diluent.
200 citations
TL;DR: In this paper, the morphology, thermal properties, fire resistance properties and mechanical properties of polyvinyl alcohol (PVA) and molybdenum disulfide (MoS2) nanocomposites are studied.
Abstract: As a graphene-like layered nano-material, molybdenum disulfide (MoS2) has gained much attention from the materials fields. In our research, MoS2/poly(vinyl alcohol) (PVA) nanocomposites are prepared by solvent blending method. The morphology, thermal properties, fire resistance properties and mechanical properties of the PVA/MoS2 nanocomposites are studied. MoS2 is homogeneously dispersed and partially exfoliated in the PVA matrix as indicated by X-ray diffraction (XRD) pattern, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) characterization. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results indicate improved the thermal decomposition temperature and the glass transition temperature (Tg). The thermal degradation temperature is increased by 20–40 °C. Meanwhile, the peak of heat release rate (pHRR) and total heat release (THR) are decreased by 33% and 20%, respectively. Storage modulus at 40 °C is increased by 28%, and the tensile strength is increased by 24% upon addition of 1 wt% and 5 wt% MoS2. The improvements in the thermal properties, fire resistance properties and mechanical properties of PVA nanocomposites are attributed to the good dispersion of MoS2, physical barrier effects of MoS2 and strong interactions between PVA and MoS2.
TL;DR: In this paper, copolymers were synthesized at 175?C by opening the rings of the cyclic dimers of the D,L-lactide and glycolide monomers in the presence of stannous octoate initiator and lauryl alcohol co-initiator.
Abstract: The copolymer poly(D,L-lactide-co-glycolide) is one of the most interesting polymers for medical applications. This interest is justified by the fact that it is bioreabsorbable, biocompatible and non-toxic, while its degradation kinetics can be modified by the copolymerization ratio of the monomers. In this study, copolymers were synthesised at 175?C by opening the rings of the cyclic dimers of the D,L-lactide and glycolide monomers in the presence of stannous octoate initiator and lauryl alcohol co-initiator. The application of vacuum to the reaction medium, coupled with adequate stirring, is essential for obtaining good results. The following analytical techniques were used to characterise the synthesised copolymers: Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Both the input monomers and the reaction products were analysed. Important characteristics, such as melting temperature, glass transition temperature, thermal stability, chemical composition and the ratio of the monomers in the synthesised copolymer, were obtained from these analyses. These results helped to infer the absence of residual monomers in the synthesised copolymers.
TL;DR: The results indicated that the electrospinning process had changed PVDF crystalline phase from the nonpiezoelectric α phase to the piezOElectric β phase, which indicates that the scaffolds are potential candidates for wound healing applications.
TL;DR: In this article, the copper shell/core nanoparticles were found to be formed by a novel coalescence mechanism that is quite different from the well-known dissolution-precipitation mechanism for some other graphene/metal (such as nickel, iron or cobalt) shell or core nanoparticles.
TL;DR: Dodecyl amine-modified graphene (DA-G)/linear low density polyethylene (LLDPE) nanocomposites were prepared through solution mixing in this article.
TL;DR: XPS studies revealed that nitrogen remained within the TiO(2) lattice at higher temperatures, and photocatalytic activity also reduced with increased annealing temperature, resulting in diminished visible light absorption capability.
TL;DR: The structure and properties of PBSFs can be tuned ranging from crystalline polymers possessing good tensile modulus and strength to nearly amorphous polymer of low T(g) and high elongation (~600%), and therefore they may find applications in thermoplastics as well as elastomers or impact modifiers.
TL;DR: In this article, a systematic investigation on the synthesis of hydrotalcites at different pH values was performed, and the results revealed that the synthesis pH plays a crucial role on the morphology, pore structure and chemical composition of the final products.
TL;DR: In this article, the segmental dynamics and glass transition temperature of polystyrene (PS) thin films were investigated by alternating current (AC) calorimetry and dielectric spectroscopy (BDS).
Abstract: We investigate the segmental dynamics and glass transition temperature (Tg) of polystyrene (PS) thin films. The former is investigated by alternating current (AC) calorimetry and dielectric spectroscopy (BDS). The Tg, underlying the equilibrium to out-of-equilibrium crossover from the supercooled liquid to the glass, is obtained by differential scanning calorimetry (DSC) and capacitive dilatometry (CD). We show that the intrinsic molecular dynamics of PS are independent of the film thickness both for the freestanding and supported films, whereas Tg decreases with film thickness from several microns down to 15 nm. This result is found for complementary methods and in a simultaneous measurement in BDS and CD. This questions the widespread notion that segmental mobility and the equilibrium to out-of-equilibrium transition are, under any experimental conditions, fully interrelated. For thin films, it appears that the molecular mobility and Tg are affected differently by geometrical factors.
TL;DR: In this paper, the form-stable composite phase change materials (PCMs) were prepared by absorbing galactitol hexa myristate (GHM) and galacticient hexa laurate (GHL) esters into porous networks of diatomite, perlite and vermiculite.
TL;DR: In this paper, a stereocomplex crystal was formed between poly(l-lactide) and poly(graphene oxide) nanocomposites using a ring-opening polymerization using modified GO as the initiator.
Abstract: Poly(lactide) (PLA)–graphene oxide (GO) nanocomposites were prepared by blending commercial poly(l-lactide) (PLLA) with GO-g-PDLA, where GO-g-PDLA was synthesized via ring-opening polymerization using modified GO as the initiator. Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) studies showed that a stereocomplex crystal could be formed between PLLA and GO-g-PDLA. The incorporation of GO nanofillers leads to a lower crystallization activation energy of stereocomplex and a higher crystallinity in solution casting samples, mainly due to the heterogeneous nucleating effect of the well-dispersed covalently bonded GO sheets, while in cold crystallized samples, the crystallinity was low owing to exfoliated GO sheets which may reduce chain mobility and hinder crystal growth.
TL;DR: In this article, a form-stable paraffin/silicon dioxide (SiO 2 )/expanded graphite (EG) composite phase change material (PCM) was prepared by sol-gel method.
TL;DR: The SCXRD structures of the various phases give clues to the structural changes that the compounds undergo at the phase transitions, which will now enable future studies of their optical and electronic properties to be better understood.
Abstract: Four inorganic-organic hybrid materials that consist of 2-D layers of corner-sharing lead(II) iodide octahedra separated by alkylammonium chains have been crystallized and characterized via single-crystal XRD (SCXRD). The four hybrids, represented by the general formula [(C(n)H(2n+1)NH(3))(2)PbI(4)] and abbreviated C(n)PbI, exhibit multiple reversible phase transitions for a narrow temperature range. The transition temperatures were determined with differential scanning calorimetry experiments. The number of transitions and the transition temperatures are dependant on the chain length; for n = 7 and 10, there are three transitions, and for n = 8 and 9, there are two transitions. Regardless of the number of transitions, all four compounds have identical lowest temperature phases, which have inorganic layers that are eclipsed, non-planar conformations of the alkyl ammonium chains and yellow-coloured crystals. The next highest temperature phase for three of the compounds (C(10)PbI goes through an intermediate phase first), has staggered inorganic layers, all-trans planar conformations of the chains and orange coloured crystals. The highest temperature phase for n = 8 and 10 has red-coloured crystals and shows a disordering of the alkylammonium chains over two positions and staggered inorganic layers. The high temperature phase of C(7)PbI retains its orange colour and has only increased thermal motion of its alkylammonium chain. The structure of the high temperature phase of C(9)PbI was not determined. The SCXRD structures of the various phases give clues to the structural changes that the compounds undergo at the phase transitions, which will now enable future studies of their optical and electronic properties to be better understood.
TL;DR: The results suggest that the porous starch has a more excellent adsorption capacity than the native starch, and may be expected to have wide potential applications in many fields.
TL;DR: In this article, the epitaxial crystallization of polyethylene (PE) on reduced graphene oxide (RGO) nanosheets via a controlled solution crystallization method was reported.
Abstract: We report epitaxial crystallization of polyethylene (PE) on reduced graphene oxide (RGO) nanosheets via a controlled solution crystallization method. Polarized light microscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy were used to investigate morphology of RGO-induced PE crystals. The PE edge-on crystals formed from randomly distributed rodlike nuclei on the basal plane of RGO nanosheets and further grew into larger lamellae with an average dimension of a few hundreds of nanometers. Selected area electron diffraction (SAED) pattern revealed that the c-axis of polymer chain is parallel to the basal plane of the RGO nanosheets. PE/RGO nanocomposites (PGNs) with different RGO loadings were fabricated through solution crystallization/precipitation using the PE-decorated RGO hybrid as the precursor. Both nonisothermal and isothermal crystallization behaviors of PGNs were studied using differential scanning calorimetry (DSC). Crystallization kinetics of PGNs w...
TL;DR: In this article, chemically derivatized graphene/polyvinyl alcohol (PVA) nanocomposites were successfully fabricated by combination of solution processing and compression molding, and the results showed enhanced thermal stability for the composites containing modified graphenes.
Abstract: Chemically derivatized graphene/poly(vinyl alcohol) (PVA) nanocomposites were successfully fabricated by combination of solution processing and compression molding. SEM imaging combined with XRD measurements revealed that graphene platelets were fully incorporated into the polymer matrix after their chemical modification through adsorption of amphiphilic copolymer. The chemical functionalities onto the graphitic surface prevented particle aggregation and pro- vided compatibility with the polymer matrix. Thermogravimetric analysis demonstrated enhanced thermal stability for the composites containing modified graphenes at loading above 1 wt%. Differential scanning calorimetry thermograms showed that graphene nanoplatelets induced the crystallization of matrix with optimum loading at 2 wt%. Dielectric spectroscopy measurements showed enhanced electrical permittivity for the graphene oxide/PVA system, compared to the one of graphene/copolymer/PVA. This could be attributed to the formation of an insulating coating between graphite inclusions and PVA because of the presence of the copolymer.
TL;DR: In this paper, a new superabsorbant cellulose-lignin hydrogels (CL) were prepared by a new two-step procedure consisting in dissolving cellulose in an alkaline solution with further mixing with lignin, followed by the chemical crosslinking with epichlorohydrin.
TL;DR: The results showed that the optimal formulation of baicalin-loaded SLN had entrapment efficiency (EE) of 88.29%, particle size of 347.3 nm and polydispersity index (PDI) of 0.169, which indicated that the drug incorporated into SLN was not in an amorphous form but in a crystalline state.
TL;DR: In this article, the crystallization behavior of polylactide (PLA) was investigated in the presence of dissolved CO2 using high-pressure and regular differential scanning calorimeter, and the results showed that increasing the CO2 pressure decreased crystallization half-time.
TL;DR: It is shown that the behavior of model nanocomposites can be quantitatively described with a gradient of glass-transition temperature and the range of this gradient allows a quantitative description of the Nanocomposite calorimetric response from the one of the bulk polymer.
Abstract: The slowing-down of the dynamics of a polymer chain near a surface has been observed for many years now. Here we show that the behavior of model nanocomposites can be quantitatively described with a gradient of glass-transition temperature. We describe with a single parameter---the range of this gradient---the temperature and solvent effect on the spin relaxation dynamics. Moreover, this parameter allows a quantitative description of the nanocomposite calorimetric response from the one of the bulk polymer.