Decrease In Decomposition Temperature Research Articles

Insight into the Types of Alkanolamines on the Properties of Copper(II) Formate-Based Conductive Ink.

Conductive inks are one of the most important functional materials for printed flexible electronic devices, and their properties determine the methods of subsequent patterning and metallization. In comparison with copper nanoparticle or nanowire inks, copper particle-free inks employing copper(II) formate (Cuf) as a precursor have attracted the interest of researchers due to their flexibility in preparation, excellent stability, and lower conversion temperature. Alkanolamines can provide Cuf with excellent solubility in alcohols while being less toxic and having a certain reducibility, making them preferable ligands in comparison with aliphatic amines and pyridine. However, there have been few studies on the effects of the alkanolamine types on the performance of Cuf inks. Also, the decomposition mechanism of copper-alkanolamine complex inks is not clear. In this work, different kinds of alkanolamines were chosen as ligands to formulate Cuf inks to address the mentioned issues. The influences of amine types on the stability, wettability, thermal decomposition behavior, and electrical performance of the formulated Cuf particle-free inks were investigated in detail. The results show that the utilization of alkanolamines could provide Cuf with excellent solubility in alcohols, resulting in an ink with good stability and favorable wetting properties. The thermal decomposition temperature and electrical performance of the formulated copper ink are largely dependent on the amine used. When amines with a longer carbon chain and more branches were utilized to prepare the ink, a decreased decomposition temperature was observed on the derived inks because of the steric hindrance effect. Copper films with good morphology and conductivity could be obtained at low temperatures by selecting the appropriate alkanolamine. Copper particle-free conductive ink from 2-amino-2-methyl-1-propanol demonstrated better morphology and electrical performance (16.09 μΩ·cm) and was successfully used for conductive circuits by direct-writing.

Hydrogel Membranes from Chitosan-Fish Gelatin-Glycerol for Biomedical Applications: Chondroitin Sulfate Incorporation Effect in Membrane Properties.

Chondroitin sulfate (ChS), chitosan (Chi), and fish gelatin (FG), which are byproducts of a fish-treatment small enterprise, were incorporated with glycerol (Gly) to obtain dense hydrogel membranes with reduced brittleness, candidates for dressing in wound healing applications. The mechanical properties of all samples were studied via Dynamic Mechanical Analysis (DMA) and tensile tests while their internal structure was characterized using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Diffraction (XRD) instruments. Their surface morphology was analyzed by ThermoGravimetric Analysis (TGA) method, while their water permeability was estimated via Water Vapor Transmission Rate (WVTR) measurements. Wettability and degradation rate measurements were also carried out. Characterization results indicated that secondary interactions between the natural polymers and the plasticizer create the hydrogel membranes. The samples were amorphous due to the high concentration of plasticizer and the amorphous nature of the natural polymers. The integration of ChS led to decreased decomposition temperature in comparison with the glycerol-free sample, and all the materials had dense structures. Finally, the in vitro endothelial cell attachment studies indicate that the hydrogel membranes successfully support the attachment and survival of primary on the hydrogel membranes and could be appropriate for external application in wound healing applications as dressings.

Influence of the memory effect during CO2/CH4 mixed gas hydrate reformation process

The study of the memory effect can help to clarify the mechanisms of synthesis and decomposition of the CO2/CH4 mixed gas hydrate for mixed gas separation, CO2 sequestration, and CH4 recovery from unconventional natural gas reservoirs. To examine the impact of the memory effect on the CO2/CH4 mixed gas hydrate synthesis in terms of induction time, gas consumption rate, change of gas components, and separation factor, we conducted initial and second CO2/CH4 mixed gas hydrate synthesis experiments in a porous medium and deionized water system. The influence characteristics of the memory effect on CO2/CH4 hydrate synthesis under the predesigned decomposition temperatures (5 ∼ 25 °C) and pressures (0.5, 1.0, and 1.5 MPa) were investigated under decomposition times of 0.5 and 1.0 h. Compared to the induction time of the initial synthesis, the induction time of the second synthesis was greatly shortened, reaching a maximum of 87.42%. The induction time decreased with decreasing decomposition temperature and pressure in the same decomposition period. The decomposition time had a large effect on the peak value of the induction time during the second synthesis process. Besides, the memory effect was greatly affected by the decomposition time in depressurization cases, and the 0.5 h decomposition time was significantly better than that of 1.0 h. The memory effect had the strongest promotion effect on the second synthesis when the decomposition pressure and time were 1.0 MPa and 0.5 h, respectively. Furthermore, the memory effect improved the nucleation rate of the CO2/CH4 mixed gas hydrate and increased the amount of CO2 hydrate synthesis to 1.3 times that of the initial synthesis. Also, the memory effect influenced the hydrate to exhibit stronger CO2 selectivity, which provides a novel approach for the separation of mixed gases via the hydrate method.

Debranching facilitates malate esterification of waxy maize starch and decreases the digestibility

In this study, the debranching followed by malate esterification was employed to prepare malate debranched waxy maize starch (MA-DBS) with a high degree of substitution (DS) and low digestibility using malate waxy maize starch (MA-WMS) as the control. The optimal esterification conditions were obtained using an orthogonal experiment. Under this condition, the DS of MA-DBS (0.866) was much higher than that of MA-WMS (0.523). A new absorption peak was generated at 1757 cm−1 in the infrared spectra, indicating the occurrence of malate esterification. Compared with MA-WMS, MA-DBS had more particle aggregation, resulting in an increase in the average particle size from scanning electron microscopy and particle size analysis. The X-ray diffraction results showed that the relative crystallinity decreased after malate esterification, in which the crystalline structure of MA-DBS almost disappeared, which was consistent with the decrease of decomposition temperature by thermogravimetric analysis and the disappearance of the endothermic peak by differential scanning calorimeter. In vitro digestibility tests showed an order: WMS > DBS > MA-WMS > MA-DBS. The MA-DBS showed the highest content of resistant starch (RS) of 95.77 % and the lowest estimated glycemic index of 42.27. In a word, pullulanase debranching could produce more short amylose, promoting malate esterification and improving the DS. The presence of more malate groups inhibited the formation of starch crystals, increased particle aggregation, and enhanced resistance to enzymolysis. The present study provides a novel protocol for producing modified starch with higher RS content, which has potential application in functional foods with a low glycemic index.

Structure, thermal stability and magnetostriction of melt-spun Nd(Fe1-xCox)1.93 ribbons

Nd-containing rare-earth-iron magnetostrictive compounds are of interest but cannot be synthesized by the conventional method when the concentration of Nd is high. Here we present an investigation of the structure, thermal stability, and magnetostriction of Nd(Fe1-xCox)1.93 ribbons prepared by melt-spinning. When the Co concentration decreases, the crystallization temperature of the ribbons increases, but the decomposition temperature decreases. Single-phase alloys with x ≥ 0.1 were obtained by annealing their ribbons between the crystallization and decomposition temperatures. With increasing x, the lattice parameter declines, while the Curie temperature and saturation magnetization reach their maximum at x = 0.2. The magnetostriction of epoxy-bonded Nd(Fe1-xCox)1.93 ribbons is slightly larger than that of those prepared by high-pressure annealing. It suggests that Nd(Fe0.7Co0.3)1.93 might be a promising and inexpensive 〈100〉 terminal compound for anisotropic compensation systems. Furthermore, this study discussed why these compounds can be prepared by melt-spinning but not by annealing their ingots, and it offers a facile and low-cost method for synthesizing high-Nd content Laves compounds.

Dilute cobalt doping induced low temperature epitaxial growth of fluorine-free MOD prepared GdBa2Cu3O7−z superconducting films

Chemical solution deposition is becoming one of the most promising routes toward cost-effective production of REBa2Cu3O7−z (REBCO) based high temperature superconducting tapes. However, a comprehensive understanding of nucleation and growth for REBCO films with dopants, especially considering low sintering temperature and high reproducibility, is still far from being achieved. In this work, dilute Co was introduced into fluorine-free precursor, and comparison studies of a set of pristine and doped GdBCO films were carried out. Correlation between texture, microstructure and critical current density were established, and nucleation & growth mechanism for doped films were proposed. By comparison, Co doping enables to reduce the textured temperature about 50 ℃ because of the dramatically decreased decomposition temperature of intermediate phase BaCO3, which facilitate Ba-Cu-O liquid phase transformation and thus GdBCO epitaxial growth at lower temperatures. These results bring particular opportunities for fine tuning of the film fabrication process by incorporating dilute impurities in precursors.

Ionic liquid-assisted production of high-porosity biochar with more surface functional groups: Taking cellulose as attacking target

• Ionic liquid pretreating biomass produced high-porosity biochar at low temperature. • Ionic liquid modification enhanced the O-containing functional groups on biochar. • In pyrolysis ionic liquid attacked cellulose reducing its dehydration activation energy. • The recyclability of the used ionic liquid was high as 87.6% with less pollution. • Ionic liquid-modified biochar achieved higher Pb adsorption (99.4%) than control. Biochar has been widely used as a multifunctional environmental material, mainly attributing to its porous structure and O-containing functional groups. However, it is hard to simultaneously improve these two properties, because pyrolysis at high temperature (600–700 °C) usually causes loss of functional groups while low temperature (300–400 °C) is adverse to form porous structure. Ionic liquid (IL) is an organic solvent, which is regarded to have catalysis on biomass during pyrolysis. In this study, a representative IL, 1-butyl-2,3-dimethylimidazolium triflate was selected to co-pyrolysis with wastepaper, and a biochar with high-porosity and more functional groups was produced at low temperature (350 °C). With incorporation of IL, the wastepaper biochar’s surface area and pore volume were increased from 19.8 to 52.8 m 2 g −1 and from 0.033 to 0.174 cm 3 g −1 , respectively. Meanwhile, more O-containing functional groups were retained. In order to reveal the mechanisms, cellulose and lignin, as two model main compositions of wastepaper, were mixed with IL respectively to produce biochar. It was found that during thermal process, IL preferred to attack cellulose rather than lignin. Before 250 °C, IL induced cellulose cleaving to monosaccharides, including levoglucosan, furanoglucose and monocyclic furfural; between 250 °C and 300 °C, IL promoted monosaccharides dehydration by reducing dehydration activation energy, leading to a decrease of decomposition temperature. Adsorption experiments showed that this IL-modified biochar had a significantly higher Pb adsorbing capacity (99.4%) than the routine biochar (25.7%). This study provides a simple method to produce high-porosity biochar with more O-containing functional groups, which would maximize and broaden its environmental application.

Additive Destabilization of Porous Magnesium Borohydride Framework with Core-Shell Structure.

Design of interfaces with thermodynamic and kinetic specificity is of great importance for hydrogen storage from both an applied and fundamental perspective. Here, in order to destabilize the metal hydride and protect the dehydrogenated products from oxidizing, a unique core-shell structure of porous Mg(BH4 )2 -based framework with a thin layer (no more than 5nm) of MgCl2 additives on the surface, has been proposed and synthesized via a wet-chemical method. The local structure and electronic state of the present complex system are systematically investigated to understand the correlation between the distribution of additives and dehydrogenation property of Mg(BH4 )2 . A significant improvement is achieved for hydrogen desorption with chlorides: initial hydrogen release from MgCl2 decorated γ-phase Mg(BH4 )2 particles commences at 100°C and reaches a maximum of 9.4 wt% at 385°C. Besides the decreased decomposition temperature, an activation barrier of about 76.4kJ mol-1 lower than that of Mg(BH4 )2 without MgCl2 is obtained. Moreover, MgCl2 decoration can also prevent the whole decomposed system (both Mg- and B- elements) from oxidizing, which is a necessary condition to reversibility.

The effect of iron decorated MWCNTs and iron‐ionic liquid decorated MWCNTs onto thermal decomposition of ammonium perchlorate

AbstractIn the present study, the effect of four nanocatalysts, namely, purified multi‐walled carbon nanotubes (MWCNTs), MWCNTs functionalized with ionic liquid (MWCNTs‐IL), MWCNTs decorated with iron nanoparticles (Fe‐MWCNTs) and the hybrid Fe‐MWCNTs‐IL on the thermal decomposition of ammonium perchlorate (AP) is highlighted. Firstly, MWCNTs are purified and impregnated under infrared irradiation followed by calcinations to obtain Fe‐MWCNTs. Secondly, a green ionic liquid (IL), based on choline chloride and urea is synthesized and used for the functionalization of MWCNTs and Fe‐MWCNTs to obtain MWCNTs‐IL and Fe‐MWCNTs‐IL, respectively. Subsequently, these nanomaterials at a ratio of 1 wt.% are introduced to AP to assess their catalytic effect using DSC and TG analyses. The obtained results highlight the catalytic effect of the functionalized MWCNTs on the thermal decomposition of AP for which a decrease in decomposition temperature of 10.7, 48.4 and 49.9 °C with an increase in decomposition enthalpy of 56.76, 689.99 and 861.11 J/g for AP supplemented with MWCNTs‐IL, Fe‐MWCNTs and Fe‐MWCNTs‐IL, respectively. Furthermore, the calculation of the kinetic parameters confirms that the best catalytic effect is obtained with the Fe‐MWCNTs‐IL hybrid, revealing the synergistic effect of iron and ionic liquid. This combination allows obtaining the lowest activation energy (∼120 kJ/mol).

Cracking mechanism and degradation performances of HTV silicone rubber with interfacial defects under acid and thermal stress

High temperature vulcanized (HTV) silicone rubber (SIR), as the sheath of composite insulators, is widely used as the insulation device in transmission lines due to their excellent hydrophobicity and pollution flashover resistance. However, the interfacial defects of insulators and severe operating environment will accelerate the aging of HTV SIR sheath, seriously affecting the operation reliability of electrical equipment. Herein, the samples designed with different sizes of interfacial defects are aged under water, sulfuric acid and nitric acid at 80 °C, respectively. The results show that a large number of cracks appear on the surface of HTV SIR samples with interfacial defects after nitric acid treatment at 80 °C for more than 2 days, while samples with no interfacial defects aged under same condition for 8 days maintain unchanged. According to the results of the micro morphology of the sample, the crack is caused by the interfacial stress of the sample. In addition, after nitric acid treatment, the thermal stability, tensile and dielectric properties of HTV SIR with interfacial defects decreased significantly. The initial decomposition temperature decreases by about 30 °C, while the residual weight increases by about 2.5%. Meanwhile, the tensile strength and fracture strain decrease from 4.58 MPa and 470% to 2.07 MPa and 130% respectively, proving that cracks caused by interfacial defects can critically avianize the mechanical properties and thermal stability of HTV SIR. Also, there is an extra dielectric loss peak appearing in the frequency range of 102–104 Hz, which attributed to water invading and the MWS polarization at cracks. By aging HTV SIR with artificial interfacial defects under thermal and acid stress, the HTV SIR cracking phenomenon of composite insulators under severe operating environment is successfully simulated. This work can provide theoretical support ulteriorly for studying the cracking mechanism and the corresponding aging characteristics of HTV SIR used in composite insulators.

Probing calorimetric heat transfer phenomena in multi-nanophase substances: A case study of some over-stoichiometric nanoarsenicals

Thermochemical events recognized from heat flux DSC measurements involving dynamic and progressive step-cycling are identified in multi-nanophase substances exemplified by melt-quenched and nanomilling-derived AsxS100-x arsenicals enriched in As over As4S3 composition (As60S40, As62S38, As64S36). Thermal-alteration heat transfer in these alloys composed of normal- and plastic-crystalline phases supplemented by dual-nature amorphous substance are complicated by transformations in nanocrystalline dimorphite-type As4S3 and realgar-type As4S4 phases. Primary calorimetric events in the examined nanoarsenicals are shown to be as follows: (i) reduction in onset temperature from normal- (α′-As4S3) to plastic-crystalline (β-As4S3) phase; (ii) depression in pre-melting temperature of β-As4S3 phase; (iii) decrease in decomposition temperature of dimorphite-type phase supplemented by appearance of realgar-type β-As4S4 and amorphous phase, (iv) increase in crystallization temperature of β-As4S3 phase; (v) high-temperature shift in relaxation from liquid to stabilized heterogeneous state. The multiphase occurrence of nanoarsenicals results in unexpected increase in some heat transfer events detected in reheating modes.

Organic Based Additives Impact on Thermal Behavior of Ammonium Perchlorate: Superior 4, 4′‐Bipyridine Versus Inferior Biphenyl

AbstractFor the first time, the thermal decomposition behavior of heterogeneous mixtures of ammonium perchlorate (AP) with two organic additives – 4, 4’‐Bipyridine, and biphenyl – were investigated. The heterogeneous mixtures of the additives and ammonium perchlorate were prepared by dissolving 1, 2, 3, 4, and 5 mg of the organic additives and 100 mg ammonium perchlorate in 2 ml of methanol as solvent. After that, the thermal decomposition behavior of prepared solid heterogeneous mixtures was monitored by thermogravimetry analysis, differential scanning calorimetry, and mass spectrometry analysis. The effect of the 4, 4’‐Bipyridine on thermal decomposition of AP enhanced the released heat from 479 to 1842 J g−1 and produced a decrease of decomposition temperature from 433 °C to 308 °C while the thermal decomposition of AP in the presence of biphenyl did not change as dramatically as it did with 4, 4’‐Bipyridine. With biphenyl, the decomposition temperature was found to be similar to that of pure AP and the evolved heat was about 718 J g−1. The gaseous products of decomposition of 4, 4’‐Bipyridine /ammonium perchlorate were monitored by mass spectrometric analysis. The main evolved decomposition gases of pure AP are N2O, O2, Cl2, ClO, ClO2, ClO3, HClO4, and HCl, while the major gaseous products of the 5:100 (w/w) mixture of 4, 4’‐Bipyridine with AP were detected as N2, NO, N2O, O2, Cl2, ClO, ClO2, ClO3, HClO4, HCl and 4, 4’‐Bipyridine. The change in the composition of volatile products indicates a change in the mechanism of AP decomposition from proton transfer to electron transfer in the presence of 4, 4’‐Bipyridine.

The significant impact colloidal nanothermite particles (Fe2O3/Al) on HMX kinetic decomposition

ABSTRACT HMX is one of the most powerful energetic materials; however, HMX experience low sensitivity and high activation energy. Whereas ferric oxide particles can act as catalyst for HMX decomposition with change in its decomposition kinetics from C-N bond cleavage to hydrogen atom abstraction; ferric oxide can induce vigorous thermite reaction with aluminum particles. Consequently, thermite particles can catalyze HMX decomposition, and enhance its decomposition enthalpy. This study reports on the fabrication and of ferric oxide nanoparticles of 5 nm particle size. Ferric oxide NPs and aluminum nanoplates of 100 nm were effectively integrated into HMX via co-precipitation technique. Elemental mapping was performed using EDAX detector; uniform dispersion of nanothermite particles was confirmed. Nanothermite particles experienced enhanced HMX decomposition enthalpy by 53%, with decrease in decomposition temperature by 13°C. The impact of nanothermite particles on HMX kinetic decomposition was evaluated using two different analysis models including differential isoconversional method of model-free Friedman analysis, and integral isoconversional method of Ozawa. Thermite nanoparticles demonstrated drastic decrease in HMX activation energy by 24 and 30% using Friedman and Ozawa models, respectively. The developed colloidal nanothermite particles demonstrated superior catalytic effect with enhanced decomposition enthalpy.

Chemical modification of pullulan exopolysaccharide by octenyl succinic anhydride: Optimization, physicochemical, structural and functional properties

Pullulan (PU) is an exo-polysaccharide used in the food and pharmaceutical industries. However, the use of PU in different industries is limited due to its highly hydrophilic nature and consequently weakness in surface properties which can be remedied by its chemical modification with octenyl succinic anhydride (OSA). For this purpose, PU modification with OSA was optimized and the results showed that the maximum degree of substitution (0.061 ± 0.003) was obtained under pH of 9.0, pullulan concentration of 40% (w/w), temperature of ~40.90 °C, reaction time of ~101.21 min and OSA concentration of 14.96% (w/w). Also, the grafting of OSA on pullulan structure was confirmed by FTIR, 1H NMR and zeta-potential analyzes. Although this modification had no significant effect on the amorphousity of pullulan, it led to an increase in viscosity and a decrease in decomposition temperature and surface tension. Improvement of emulsifying properties of PU-OSA sample was proved by the evaluation of emulsifying capacity of un- and modified samples and also, zeta-potential, particle size and viscosity of the prepared emulsions. In line with surface characteristic results, an increase in foam capacity of modified samples was observed with decreasing the interfacial tension.

Effect of Transition Metal Additives on the Catalytic Performance of Cu–Mn/SAPO-34 for Selective Catalytic Reduction of NO with NH3 at Low Temperature

The adsorption of NO, NH3, H2O, and SO2 gaseous molecules on different transition metal oxides was studied based on density function theory (DFT), and three better-performing transition metal elements (Fe, Co, and Ce) were selected. Cu–Mn/SAPO-34 catalysts were prepared by impregnation method and then modified by the selected transition metals (Fe, Co, and Ce); the SO2 resistance experiments and characterizations including Brunner−Emmet−Teller (BET), X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), and thermal gravity analysis (TG)-differential thermal gravity (DTG) before and after SO2 poisoning were conducted. The results showed that the deactivation of the Cu–Mn/SAPO-34 catalyst is ascribed to the deposition of lots of ammonium sulfates on the surface, depositing on the active sites and inhibiting the adsorption of NH3. After the modification of Fe, Co, and Ce oxides, the SO2 resistance of the modified Cu–Mn/SAPO-34 catalyst was significantly enhanced due to the less formation of ammonium sulfates. Among all these modified Cu–Mn/SAPO-34 catalysts, the Cu–Mn–Ce/SAPO-34 exhibited the highest SO2 resistance owing to the decreased decomposition temperature and the trapper of ceria for capturing SO2 to form Ce(SO4)2, further inhibiting the deposition of ammonium sulfates.

High energy-density multi-form thermochemical energy storage based on multi-step sorption processes

A novel multi-form thermochemical energy storage method is proposed for high energy-density thermal energy storage based on multi-step sorption processes. The proposed multi-form thermochemical energy storage combines the physisorption energy storage of a porous matrix, the chemisorption energy storage of a salt hydrate, and the absorption energy storage of the salt solution. High-performance composite sorbent of MgCl2@zeolite was prepared to demonstrate the feasibility of the proposed multi-form thermochemical energy storage. The water uptake contributions of physisorption, chemisorption and absorption of the composite sorbent were measured by a “three-step” hydration method. The multi-step desorption processes measured by TG at an extremely slow heating rate shows the apparent decrease of decomposition temperature of MgCl2 hydrates in zeolite matrix. The maximum sorption capacity of the MgCl2@zeolite composite sorbent without solution leakage is as high as 0.55 g/g and its gravimetric and volumetric thermal energy densities reach 1368 kJ/kg and 308 kWh/m3 respectively with charging temperature of 200 °C. This gravimetric energy density is about 2.26 times higher than that of pure zeolite 13X. The experimental results verified that the proposed multi-form thermochemical energy storage is an effective method to improve sorption capacity and to achieve high energy-density thermal storage.

Structure and Properties of Polymer–Polymer Composites Based on Biopolymers and Ultra-High Molecular Weight Polyethylene Obtained via Ethylene In Situ Polymerization

Polymer–polymer composites (PPC) of biopolymers (starch, cellulose, poly-3-hydroxybutyrate) and ultra-high molecular weight polyethylene (UHMWPE) were obtained by ethylene in situ polymerization (polymerization filling). Ethylene polymerization was carried out in “mild” conditions (25 °C, 0.1 MPa) on a traditional Ziegler–Natta catalyst [TiCl4 + (C2H5)2AlCl], biopolymer-supported. Catalyst activity increases in the presence of polysaccharides depending on their type and quantity. UHMWPE matrix possesses a molecular weight of 1.20–1.65 MDa, melting point of 138–143 °C, high melting enthalpy and a crystallinity of 60–70%. PPCs generally exhibit better tensile properties than neat polyethylene, such as elastic modulus and elongation at break. Thermogravimetric analysis shows a significant decrease in decomposition temperature and the rate of mass loss on both stages of PPC destruction. The photo-oxidative destruction of PPC after UV-irradiation for different periods of time was studied by FTIR and XRD. Carbonyl indices indicate the rate of oxidation to be 3–4 times greater than in neat PE. Prolonged irradiation leads to a considerable increase in crystallinity and crystallite size. Irradiated PPC films show a 90% extent of biofouling by mold fungi, compared to no growth apparent for neat samples.

Multistage thermal decomposition in films of cadmium chloride-doped PVA–PVP polymeric blend

Films of cadmium chloride (CdCl2) doped polyvinyl alcohol (PVA)–polyvinyl pyrrolidone (PVP) polymer blend have been studied using thermogravimetry (TG) and differential scanning calorimetry (DSC), for doping levels ranging from 0.0 mass% to 50.5 mass%. At high doping levels (beyond 10.2 mass%), TG scans of these films showed several stages of decomposition at temperatures beyond 100 °C, indicating that the incorporation of CdCl2 results in deterioration of PVA–PVP blend, on thermal activation. The presence of melting peaks, which is due to melting of crystalline regions in CdCl2-doped PVA–PVP blend samples and the occurrence of thermal decomposition, in different stages, is confirmed by DSC curves. There is a decrease in decomposition temperature of the doped PVA–PVP blend, with an increase in salt (CdCl2) concentration. Kinetic analysis has been performed using iso-conversional models, using Flynn–Wall–Ozawa (FWO) equation, Kissinger–Akahira–Sunose (KAS) equation and Kissinger relation at four different stages of thermal decomposition, for the 10.2 mass% CdCl2-doped PVA–PVP blend. The higher values of activation energy, Ea= 197.5, 196.0 and 175.3 kJ mol−1 obtained from FWO, KAS and Kissinger models reveal that CdCl2-doped PVA–PVP sample has more thermal stability when compared to the undoped PVA–PVP blend.

Novel dextran modified bacterial cellulose hydrogel accelerating cutaneous wound healing

Development of an ideal wound dressing to efficiently improve the wound healing process is an important issue in wound care. The present study aims to develop a dextran/bacterial cellulose (BC) hydrogel and to evaluate its performance in wound healing applications. The assessments include material properties (morphology, thermostability and its mechanical properties), cytotoxicity, cell proliferation and wound healing. The results show that the addition of dextran affected the network structure of BC resulting in decreased decomposition temperature (339–261 °C), water content (98.7–89.2%), and tensile strength (23–0.61 MPa). However, the elongation rates were kept at approximately 33–28% in BC, 10% and 20% in dextran modified groups. Cell-based experiments showed that the dextran-modified BC hydrogel promoted enhanced cell proliferation without cytotoxicity compared to unmodified BC. Finally, the in vivo wound healing test demonstrated that dextran-modified BC hydrogel can accelerate the wound healing process and facilitate skin maturation, which suggests that dextran/BC hydrogel is a promising wound dressing for clinical applications.

Green synthesis of ZnCo2O4 nanoparticles by Aloe albiflora extract and its application as catalyst on the thermal decomposition of ammonium perchlorate

ZnCo2O4 nanoparticles were prepared by green method using Aloe albiflora extract solution and characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy, and the result showed that the average particle size was <30 nm. The effect of the ZnCo2O4 nanoparticles on thermal decomposition of ammonium perchlorate (AP) was enhancing the evolved heat from 400 to 1505 J g−1 and a decrease of decomposition temperature from 420 to 310 °C. The kinetic parameters of thermal decomposition of both pure AP and catalyzed sample have been calculated by Kissinger method, and the results showed that the values of pre-exponential factor and activation energy of thermal decomposition of catalyzed sample increased with respect to that of pure AP. However, the calculated rate constant was higher in presence of ZnCo2O4 nanoparticles.