Low-temperature Thermal Decomposition Research Articles

Specialized Methods of Thermal Treatment of Riverine and Marine Suspensions Preparatorily to Their Analysis for Trace Concentrations of Chemical Elements

The paper considerations of the possibility of the low-temperature (1000°C) and high-temperature (>1500°C) thermal decomposition of solid samples of suspensions and the selective fractional evaporation–condensation of elements in specialized electrothermal crucible and rod atomizers for the purposes of direct atomic-absorption analysis. The approach is applied to analyze samples of riverine and marine suspensions for Ag, Cd, and Tl.

Lithium doping and photoluminescence properties of ZnO nanorods

This article presents a comprehensive experimental study of optical properties of Li-doped ZnO nanorods grown by a low temperature (300 °C) thermal decomposition method. In particular, a study of the room temperature photoluminescence spectra dependence on the Li concentration is presented here. The doping of Li in ZnO nanorods results in a redshift in near band edge emission (NBE) compared to the undoped ZnO nanorods. Depending on the Li concentration, we observe a green emission in Photoluminescence spectra. The possible physical mechanisms governing the visible region luminescence are also discussed. These results show that Li-doped ZnO nanorods with strong visible region luminescence have potential applications in optoelectronic devices.

Morphology and mechanical properties of UV-curable castor oil-based waterborne polyurethane/organic montmorillonite nanocomposites

ABSTRACTWater resistance is a unique advantage of castor oil-based polyurethane, permitting the application of coatings in humid environments. However, its low thermal decomposition temperature remains a limitation. Here, to demonstrate a simple method to improve the thermal stability of cured films, we prepared an organic montmorillonite dispersion utilising 3-(methacryloyloxy)propyltrimethoxysilane and protonated 3-aminopropyltriethoxysilane for modifying the clay. The method was put into practice by directly mixing the dispersion with a UV-curable castor oil-based waterborne polyurethane dispersion. The inclusion of organic molecule chains from the silane coupling agents noticeably improves the compatibility of polyurethane with organic montmorillonite, which imparts the composite latex with better thermal stability and mechanical properties when the organic montmorillonite additive is 5.0 wt-%.

Enhanced thermal stabilization of polymer nanofibrous web using self-polymerized 3,4-dihydroxy-L-phenylalanine

When used as an industrial polymer, poly(vinyl alcohol) (PVA) has the disadvantage of low thermal decomposition temperature. Therefore, various studies are under way to overcome this drawback. PVA is thermally decomposed in a two-stage process, in which radicals are formed in the first stage, and subsequently the backbone chain of PVA is decomposed via a chain reaction. Poly(3,4-dihydroxy-L-phenylalanine) (pDA) synthesized by the self-polymerization of 3,4-dihydroxy-L-phenylalanine (DA) has radical scavenging ability. Therefore, the thermal stability of PVA was improved by the radical scavenging ability of pDA. The thermal decomposition behavior of poly(lactic acid) (PLA) was compared with that of PVA, to confirm that the thermal stability improvement was due to the radical scavenging reaction. In addition, the radical scavenging ability of pDA was confirmed by using antioxidant reagents DPPH and ABTS. The thermal decomposition behavior of the polymer was characterized by TGA and DTG, and the radical scavenging activity was analyzed by UV-Vis spectrometry.

Tuning of synthesis conditions by thermal decomposition towards gadolinium-doped manganese carbonate nanoparticles with uniform size and high relaxivity

A low temperature thermal decomposition method has been developed to synthesize uniform-sized Gd-doped MnCO3 nanoparticles.

Characterization of alkali-metal vapor cells fabricated with an alkali-metal source tablet

Optically pumped magnetometers (OPMs) that use alkali metal vapor cells can measure weak magnetic fields generated by the human body. A multichannel detector head with alkali-metal vapor cells mounted in arrays is employed to assure spatial resolution for real-time biomagnetic imaging of various body surfaces. However, further development of alkali metal vapor cell fabrication processes is required to obtain cells with uniform magnetic field sensitivities together with sufficient sensitivity of each individual cell. Herein, the authors propose the fabrication of alkali metal vapor cells for OPM arrays using alkali metal source tablets (AMSTs) as alkali metal dispensers. An AMST is a three-dimensional microstructure that contains precise quantities of the chemical precursors that are used to produce pure alkali metals by low temperature thermal decomposition and to fill reproducible quantities of these metals into cells. In this work, the K production efficiency was characterized with respect to the particular chemical precursors and AMST microstructure employed, and the potential of K-filled glass cells fabricated using AMSTs as components of OPM arrays was demonstrated. An AMST composed of KN3 deposited on porous alumina with 60 μm pore sizes exhibited the most efficient performance during the fabrication of K-filled glass cells. The magnetometric sensitivity obtained with eight K-filled cells was found to be in the range of 3.3–3.8 fTrms/Hz1/2 at a resonance frequency of 10 kHz.

A Layered Delta-MnO2 Nanoflake Cathode with High Zinc-Storage Capacities for Eco-Friendly Battery Applications

This study reports the use of a layered-type birnessite δ-MnO2 nano-flake cathode for eco-friendly zinc-ion battery (ZIB) applications. The present δ-MnO2 was prepared via the simple low temperature thermal decomposition of KMnO4. The X-ray diffraction (XRD) pattern of the samples was well indexed to the δ-MnO2 phase. Field emission SEM and TEM images of the δ-MnO2 revealed flake-like morphologies with an average diameter of 200 nm. The electrochemical properties, investigated by cyclic voltammetry and constant current charge-discharge measurements, revealed that the nano-flake cathode exhibited first discharge capacity of 122 mAh g-1 under a high current density of 83 mA g-1 versus zinc. The discharge capacity thereafter increased until it reached 252 mAh g-1 in the fourth cycle. On the hundredth cycle, the electrode registered a discharge capacity of 112 mAh g-1. Coulombic efficiencies of nearly 100% were maintained on prolonged cycling and thereby indicate the long cycle stability of the δ-MnO2. Besides, the realization of specific capacities of 92 and 30 mAh/g at high current densities of 666 and 1333 mA/g, respectively, clearly demonstrates the decent rate capabilities of δ -MnO2 nano-flake cathode. These results may facilitate the utilization of layered-type birnessite δ-MnO2 in ZIB applications.

Polyethylene Nanocomposites for the Next Generation of Ultralow-Transmission-Loss HVDC Cables: Insulation Containing Moisture-Resistant MgO Nanoparticles.

The use of MgO nanoparticles in polyethylene for cable insulation has attracted considerable interest, although in humid media the surface regions of the nanoparticles undergo a conversion to a hydroxide phase. A facile method to obtain MgO nanoparticles with a large surface area and remarkable inertness to humidity is presented. The method involves (a) low temperature (400 °C) thermal decomposition of Mg(OH)2, (b) a silicone oxide coating to conceal the nanoparticles and prevent interparticle sintering upon exposure to high temperatures, and (c) heat treatment at 1000 °C. The formation of the hydroxide phase on these silicone oxide-coated MgO nanoparticles after extended exposure to humid air was assessed by thermogravimetry, infrared spectroscopy, and X-ray diffraction. The nanoparticles showed essentially no sign of any hydroxide phase compared to particles prepared by the conventional single-step thermal decomposition of Mg(OH)2. The moisture-resistant MgO nanoparticles showed improved dispersion and interfacial adhesion in the LDPE matrix with smaller nanosized particle clusters compared with conventionally prepared MgO. The addition of 1 wt % moisture-resistant MgO nanoparticles was sufficient to decrease the conductivity of polyethylene 30 times. The reduction in conductivity is discussed in terms of defect concentration on the surface of the moisture-resistant MgO nanoparticles at the polymer/nanoparticle interface.

Cellulose dissolution and regeneration using various imidazolium based protic ionic liquids

A new series of six protic ionic liquids (PILs) comprising substituted imidazolium cations paired with lactate or glycolate anions were synthesized for cellulose dissolution. All the six synthesized PILs were able to dissolve about 5wt% of cellulose. Especially, 1-ethyl imidazolium lactate showed highest dissolution power since 5wt% of cellulose solution was obtained within 20min at 80°C. The effects of dissolution temperature on cellulose dissolution time were also investigated. As the dissolution temperature increases, dissolution time reduces significantly. The regeneration of cellulose with higher yield was achieved by adding anti-solvent like deionized water to the cellulose solution. Both the initial and regenerated cellulose samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscope (SEM) analysis. The results showed that the crystalline structure of initial cellulose (cellulose I) gets converted to cellulose II. In addition, all regenerated cellulose possessed nanostructure and lower thermal decomposition temperature than the initial cellulose and had new vistas in the industrial applications.

Controllable Synthesis of Covellite Nanoparticles via Thermal Decomposition Method

In this study, covellite (CuS) nanoparticles were synthesized through a facile and low temperature thermal decomposition method using [Cu(sal)2]- oleylamine complex, (sal = salicylaldehydeato, prepared in situ from [Cu(sal)2] and oleylamine as the precursors), and sulfur as the Cu2+ source and S source, respectively. Scanning electron microscope, transmission electron microscope, electron diffraction and ultraviolet–visible absorption (UV–Vis) spectra were used for the characterization of the products. The effect of reaction parameters, such as the copper:sulfur molar ratio, the reaction temperature and the reaction time on the shape, size and phase of CuS nanostructures, was investigated. The results showed that the, covellite (hexagonal structure of CuS) with an average size between 20 and 45 nm could be obtained with the Cu:S molar ratio of 1: 3 at 105 °C for 60 min. With increasing the reaction temperature from 105 to 200 °C, non-stoichiometric Cu1.65S with the average size of 25–50 nm was obtained due to the different existing state of the released Cu2+ ions from the copper-oleylamine complex.

A layered δ-MnO 2 nanoflake cathode with high zinc-storage capacities for eco-friendly battery applications

Abstract This study reports the use of a layered-type birnessite δ-MnO2 nano-flake cathode for eco-friendly zinc-ion battery (ZIB) applications. The present δ-MnO2 was prepared via the simple low temperature thermal decomposition of KMnO4. The X-ray diffraction (XRD) pattern of the samples was well indexed to the δ-MnO2 phase. Field emission SEM and TEM images of the δ-MnO2 revealed flake-like morphologies with an average diameter of 200 nm. The electrochemical properties, investigated by cyclic voltammetry and constant current charge-discharge measurements, revealed that the nano-flake cathode exhibited first discharge capacity of 122 mAh g− 1 under a high current density of 83 mA g− 1 versus zinc. The discharge capacity thereafter increased until it reached 252 mAh g− 1 in the fourth cycle. On the hundredth cycle, the electrode registered a discharge capacity of 112 mAh g− 1. Coulombic efficiencies of nearly 100% were maintained on prolonged cycling and thereby indicate the long cycle stability of the δ-MnO2. Besides, the realization of specific capacities of 92 and 30 mAh/g at high current densities of 666 and 1333 mA g−1, respectively, clearly demonstrates the decent rate capabilities of δ-MnO2 nano-flake cathode. These results may facilitate the utilization of layered-type birnessite δ-MnO2 in ZIB applications.

Hierarchically Ordered Porous Carbon as a Host Material for Energetic Composites

Hierarchically ordered macro-/mesoporous carbon (HOPC) was synthesized via a dual-template approach and used as the host matrixes to design the host-guest energetic composites. Monodisperse silica colloidal crystals were used as a hard template, amphiphilic triblock copolymer Pluronic F127 as a soft template, and soluble resols as a carbon source. The obtained HOPC is composed of highly ordered fcc macropores (225 nm), interconnected macropore windows (40 nm), and large mesopores (11.6 nm), resulting in high surface area (503.6 m2/g) and large pore volume (0.833 cm3/g). A high energy material (CL-20) had been encapsulated in HOPC by impregnation process, and the maximum loading amount was around 63 wt.%. The synthesized CL-20/HOPC host-guest energetic composites exhibit much lower thermal decomposition temperature than that of pure CL-20 and their physical mixture.

Development of hierarchically porous cobalt oxide for enhanced photo-oxidation of indoor pollutants

Porous cobalt oxide was successfully prepared by precipitation of cobalt hydroxide followed by low temperature thermal decomposition. The morphologies of the resultant oxides remained as the corresponding hydroxides, although the morphology of cobalt hydroxides was greatly influenced by the precursor salts. The cobalt oxides with average crystal size less than 20 nm were characterized by X-ray diffraction, scanning electron microscope, BET surface area, and XPS analysis. The photocatalytic activities of the various cobalt oxides morphologies were investigated by comparing the photo-degradation of acetaldehyde under simulated solar illumination. Relative to their low order structures and reference titania samples, the hierarchical nanostructures of cobalt oxide showed excellent abilities to rapidly degrade acetaldehyde, a model air pollutant. This was attributed to the unique nature of these hierarchical cobalt oxide nanoassemblies, which contained many catalytically active reaction sites and open pores.

Synthesis of different CuO nanostructures by a new catalytic template method as anode materials for lithium-ion batteries

CuO powders composed of different rod-like clusters or dandelion-like nanospheres are prepared by a low-temperature thermal decomposition process of Cu(OH)2 precursors, which are obtained via a catalytic template method.

Synthesis of copper conductive film by low-temperature thermal decomposition of copper–aminediol complexes under an air atmosphere

The low-temperature synthesis of electrical conductive copper films under an air atmosphere was successfully developed by thermal decomposition using copper–aminediol complexes. Ink-mixed copper(II) formate and various types of aminediols were coated onto glass substrates, which were then calcined in air at various temperatures. Copper–aminediol complex inks were calcined with either 3-dimethylamino-1,2-propanediol or 3-diethylamino-1,2-propanediol at 165–180 °C to produce films with electrical conductivity and a minimum surface resistivity of 0.2 Ω sq−1. The film consisted of copper particles 1–3 μm in diameter. Aminediol adsorbed onto the surface of copper particles in the film prevented attacks from oxygen.

Synthesis of water-dispersible silver nanoparticles by thermal decomposition of water-soluble silver oxalate precursors.

Silver oxalate, one of the coordination polymer crystals, is a promising synthetic precursor for transformation into Ag nanoparticles without any reducing chemicals via thermal decomposition of the oxalate ions. However, its insoluble nature in solvents has been a great disadvantage, especially for systematic control of crystal growth of the Ag nanoparticles, while such control of inorganic nanoparticles has been generally performed using soluble precursors in homogeneous solutions. In this paper, we document our discovery of water-soluble species from the reaction between the insoluble silver oxalate and N,N-dimethyl-1,3-diaminopropane. The water-soluble species underwent low-temperature thermal decomposition of the oxalate ions at 30 °C with evolution of CO2 to reduce Ag+ to Ag0. Water-dispersible Ag nanoparticles have been successfully synthesized from the water-soluble species in the presence of gelatin via similar thermal decomposition at 100 °C. The gelatin-protected and water-dispersible Ag nanoparticles with a mean diameter of 25.1 nm appeared. In addition, antibacterial activity of the prepared water-dispersible Ag nanoparticles has been preliminarily investigated.

Surfactant controlled low-temperature thermal decomposition route to zinc oxide nanorods from zinc(II) acetylacetonate monohydrate

Zinc oxide (ZnO) nanorods were synthesized via a low-temperature thermal decomposition of zinc(II) acetylacetonate monohydrate, [Zn(C5H7O2)2].H2O. A relatively inexpensive surfactant, octadecylamine (C18H37NH2) served both as a reaction solvent and a capping agent during the synthesis of ZnO nanorods. The synthesized nanorods were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR, UV–visible, and photoluminescence (PL) studies. The XRD spectrum furnished evidence for the hexagonal wurtzite structure of ZnO. TEM images revealed the material to be rod shaped having diameter 30nm and length 200nm. The HRTEM image showed that the lattice fringes between the two adjacent planes are 0.244nm apart, which corresponds to the interplanar separation of the (101) plane of hexagonal ZnO. The electron diffraction (ED) pattern confirmed the single crystalline nature of the nanorods. The PL spectrum showed two UV emissions at 356nm (~3.48eV) and 382nm (~3.25eV). ZnO nanorods also showed very weak blue bands at 445, 453 and 470nm.

Development of Amorphous Oxide Coated Anode for Electrowinning of Zinc and Copper

Zinc and copper are produced by electrowinning (EW) using sulfuric acid based solutions, in which oxygen evolution from water is the main anodic reaction, while it is known that the oxidation of Mn(II) or Pb(II) ions contained in the EW solutions also occur as unwanted side reactions on the anode, resulting in anodic deposition of MnOOH or PbO2 [1, 2]. These reactions cause an increase in oxygen overpotential and a decrease in lifetime of the anode, because such metal oxides have a low conductivity and oxygen evolution is disturbed by the accumulation of the oxides. Although a commercially available IrO2-Ta2O5/Ti anode comprising crystalline IrO2 and amorphous Ta2O5 has a high catalytic activity and a long lifetime for oxygen evolution [3], it is impossible to suppress such unwanted side reactions even with this anode [4]. On the other hand, one of the authors of this paper has previously revealed that amorphous IrO2-Ta2O5/Ti anodes prepared by a low temperature thermal decomposition, e.g., at 360 oC, have a higher catalytic activity for oxygen evolution than crystalline IrO2-Ta2O5/Ti anodes and can suppress anodic depositions of MnOOH and PbO2 [5,6]. Furthermore, we have been developing RuO2-Ta2O5/Ti anode consisting of amorphous RuO2 and amorphous Ta2O5 for oxygen evolution in EW. This paper reports the effect of the crystallographic structure and surface morphology of the RuO2-Ta2O5 catalytic coatings on oxygen evolution, including suppression of MnOOH and PbO2deposition in addition to a significant cell voltage reduction for zinc and copper EW. RuO2-Ta2O5/Ti anodes were prepared by thermal decomposition of the precursor solution containing Ru (III) and Ta (V). The precursor solution was painted on a titanium substrate and calcined at a temperature between 260 oC to 500 oC. The characterization of the oxide coating was carried out with XRD, SEM and EDX. Electrochemical measurements were performed using a conventional three-electrode cell, in which the electrolytes were H2SO4 solutions with and without MnSO4 5H2O or HNO3 solutions with and without Pb(NO3)2. Constant current electrolysis was conducted using a two-electrode cell to determine the cell voltage during zinc or copper EW and to evaluate the anode’s durability for a long term operation. The crystallographic structure of RuO2 changed from crystalline to amorphous when the thermal decomposition temperature decreased from 500 oC to 260 oC. The surface morphology of the amorphous coating showed that nano-RuO2 particles, ca. 20 nm, were dispersed in amorphous Ta2O5 matrix. Such nano particles worked well to increase the active surface area for oxygen evolution, resulting in not only a low overpotential for oxygen evolution but also a high overpotential for PbO2 deposition as shown Fig. 1. The onset potentials obtained with RuO2-Ta2O5 coatings prepared at 500 oC, 280 oC and 260 oC indicates that the overpotential for oxygen evolution decreases, but that of PbO2 deposition increases as thermal decomposition temperature becomes lower; therefore, the difference between the onset potentials for oxygen evolution and PbO2 deposition becomes larger and especially reaches 500 mV with amorphous RuO2-Ta2O5/Ti anode obtained at 260 oC. This means that the overpotentials of two difference reactions occurring on the same anode are individually controlled and the amorphization of RuO2 works well to accelerate only to oxygen evolution, not to PbO2 deposition. As similar to this, MnOOH deposition was also suppressed on the amorphous RuO2-Ta2O5/Ti anode. The cell voltage during zinc or copper EW was measured using different anodes; amorphous RuO2-Ta2O5/Ti, amorphous IrO2-Ta2O5/Ti, and Pb alloy. Table 1 shows a comparison of the cell voltages at 500 A/m2. The results revealed that the amorphous RuO2-Ta2O5/Ti anode showed 700 mV lower voltage than the Pb alloy anode and 140-160 mV lower voltage than the amorphous IrO2-Ta2O5/Ti anode. This significant voltage reduction is important because a large energy saving is expected for zinc and copper EW. This work further demonstrated the excellent durability of amorphous RuO2-Ta2O5/Ti anode for oxygen evolution for more than 1000 hours. This work was financially supported by Grant-in-Aid for "Kyoto Environmental Nanotechnology Cluster" of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Table 1 Comparison of cell voltages during constant current electrolysis in zinc or copper EW at 500 A/m2. RuO2-Ta2O5/TiIrO2-Ta2O5/TiPb alloyZn2.32 V2.46 V3.02 VCu1.22 V1.38 V1.92 V References1) S. Nijjer, J. Thonstad, G. M. Haarberg, Electrochim. Acta, 46, 3503 (2001).2) Z. S. Msindo, V. Sibanda, J. H. Potgieter, J. Applied Electrochemistry, 40, 691 (2009).3) S. Trasatti, Electrochimica Acta, 45, 2377 (2000).4) M. S. Moats, JOM, 60, 46 (2008).5) M. Morimitsu, N. Oshiumi, T. Yamaguchi, Proc. Lead-Zinc 2010, 813 (2010).6) M. Morimitsu, N. Oshiumi, N. Wada, Proc. Copper 2010, 4, 1511 (2010).

Synthesis and antioxidant activity of cupric oxide nanoparticles accessed via low-temperature solid state thermal decomposition of bis(dimethylglyoximato)copper(II) complex

Cupric oxide (CuO) nanoparticles have been successfully synthesized via low-temperature thermal decomposition of bis(dimethylglyoximato)copper(II) complex. The synthesized nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS) and Raman spectroscopy. The powder XRD pattern furnished evidence for a monoclinic structure of CuO with average crystallite size 28.9nm. The TEM image showed aggregation of some quasi-spherical nanoparticles. The Raman spectrum showed three characteristic modes of CuO which further affirmed the phasic purity of the obtained material. The CuO nanoparticles studied in an in vitro system using the modified diphenylpicrylhydrazyl (DPPH) method exhibited pronounced antioxidant activity.

A comparative study on two explosive acetone peroxides

Two explosive cyclic acetone peroxides, diacetone diperoxide (DADP) and triacetone triperoxide (TATP) have been studied in respect of thermal decomposition, burning behavior, impact sensitivity, and initiating efficiency. Using the glass Bourdon gauge technique, the vapor pressures of TATP and DADP were determined over the temperature range 75–144°C and 67–120°C, respectively. The kinetic parameters of decomposition of the peroxides in the gas phase have been obtained in the temperature interval of 140–200°C. The decomposition of both DADP and TATP followed the first-order reaction to high degrees of decay with close activation energies of 159.2kJ/mol (38.0kcal/mol) and 165.8kJ/mol (39.6kcal/mol), respectively. The decomposition rate constants of DADP were found to be approximately 2 times less than those of TATP. The linear burning rate of DADP measured in a constant-pressure window bomb appeared to be approximately 5 times less than that of TATP. Temperature profiles in the combustion wave were measured at subatmospheric pressures with the help of thin tungsten-rhenium thermocouples. The leading reaction on combustion of both volatile peroxides was assumed to occur in the gas phase. Kinetic parameters of the leading reaction derived from the combustion data showed a good agreement with kinetic parameters of low-temperature thermal decomposition extrapolated to the high-temperature flame zone. In the drop-weight impact test, DADP appeared to be notably less sensitive peroxide than TATP. No deflagration-to-detonation transition was observed when RDX was attempted to explode by using 0.5g of DADP in the standard detonator No. 8 shell. Comparing explosive properties of the studied peroxides, DADP may be considered as a less dangerous, however still unsafe explosive in handling as TATP.