Chung-King Hsu

A study on the thermal decomposition behaviors of PETN, RDX, HNS and HMX

Abstract Pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine or octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (RDX), hexanitrostilbene or 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) and cyclotetramethylene tetramine, hexahydro-1,3,5-trinitro-1,3,5-triazine (HMX) are very important high explosives. All are used in a wide variety of military and industrial formulations owing to their suitable properties. Many researchers have demonstrated the usefulness of the above four energetic materials in explosive components. In this work, the thermal decomposition characteristics of PETN, RDX, HNS and HMX were studied using thermal analytical techniques (TG and DSC). Their compatibility with silicone rubber and the kinetic parameters such as decomposition activation energies and the frequency factor of the reaction are also evaluated by non-isothermal differential scanning calorimetry (DSC) techniques.

Fabrication, characterization, and application of greigite nanoparticles for cancer hyperthermia

Greigite is a Fe-S-containing complex having magnetic properties mainly synthesized in the solution. In the present study, greigite was synthesized by a coprecipitation method at different pHs and reaction times. The greigite phase was analyzed by the X-ray diffraction (XRD) method at an optimum pH of 3.0 and reaction time of 10 min, respectively. The magnetization characterization by superconducting quantum interference device (SQUID) revealed that the magnetic saturation was obtained at 16.1538 (emu/g). The inductive heating property of the greigite nanoparticles was carried out by induction heater power cube (IHPC) in an alternating current magnetic field and the results indicated that the heating effect was significant. Transmission electron microscopy (TEM) revealed that the size of the greigite was around 50-100 nm and the edges of nanoparticles have no clear boundary or distinctive morphology. Studies on LDH and WST-I assay revealed low cytotoxicity at greigite concentrations of 1 mg/ml. In vitro experiments suggested that cancerous cells, human lung adenocarcinoma epithelial cell line (A549), had the ability to become more damaged under AC magnetic field than the normal human lung cells (HFL-1).

The thermal decomposition behaviors of stearic acid, paraffin wax and polyvinyl butyral

Organic processing additives, such as polymers, dispersants, solvents and plasticizers, are often required to enhance the forming capabilities of ceramic powders. The term binder system is used to collectively describe those added materials that remain in the as-formed ceramic body after drying. Such additives must then be removed completely prior to component densification during subsequent different heat treating procedures. In this work, the thermal decomposition behaviors of binder system such as stearic acid, paraffin wax and polyvinyl butyral were investigated using DTA/TG. The kinetic parameters of thermal decomposition were also evaluated by non-isothermal DTA/TG techniques.

Cracking defect and porosity evolution during thermal debinding in ceramic injection moldings

Formation of cracking defect during thermal debinding of a wax-based zirconia–binder system has been investigated at varying binder formulations (volumetric ratio of low-melting vs high-melting binder constitutes ranging from 1.7 to 2.8), heating rates (5–30°C h−1) and the use of wicking powders in ceramic injection moldings. Increase of the low-melting binder ingredients to a critical ratio of 2.8 resulted in an apparent cracking at a relatively low pyrolysis temperature of 250°C as the heating rate was increased to 30°C h−1. The cracking was avoided by use of wicking powders during thermolysis. The most frequent pore diameter of samples debound without the packing powders rapidly increased by nearly 3-fold over a temperature range from 200 to 250°C; contrarily, a gradual increase in the pore size was resulted when moldings were debound under the identical condition but with the packing powders. This finding is correlated with the incidence of cracking and its possible causes are discussed.

The preparation of biphasic porous calcium phosphate by the mixture of Ca(H2PO4)2·H2O and CaCO3

Abstract Sintered hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), that analogous to the constituent of human hard tissues, are the most common bio-ceramics for bone substitute. However, the higher temperature preparation lose the functional groups for bioactivity and closed the micropores without any interconnection that hampere the body fluid transportation and angiogenesis during regeneration. Furthermore, the sinter ceramics with block and fixed size is difficult to fit non-regular defect area. In this study, a composite of HA/β-TCP will be prepared by mixing Ca(H2PO4)2·H2O and CaCO3 and distilled water as a bone cement. The slurry dough is fast setting and can be fit in any size and shape of the defect. The final product of setting cement will have a micropores and macropores for fluid transportation and tissue regeneration. The molar ratio of Ca(H2PO4)2·H2O and CaCO is in the range of 1.5 and 2.0 the mechanism of faster setting time of the prepared cement will be elucidated by in terms of the thermal properties and thermal decomposition kinetic parameters, which are going to be investigated by non-isothermal DTA/TG techniques and SEM, respectively.

Thermal decomposition properties of polymer fibers

Polymer fibers are one of the main substances used for the reinforcement of plastic composites. Their characteristics are very important, especially the thermal properties of the reinforcement materials and matrix polymers. In this work, the thermal properties of polymer fibers were investigated using DSC/DTA/TG. The thermal decomposition kinetic parameters of polypropylene fibers were then evaluated by non-isothermal DSC/DTA/TG techniques. The data from the thermal analysis for the polymer fibers would be a reference fingerprint for thermal analysis.

Thermal properties and shelf life of HMX-HTPB based plastic-bonded explosives

Abstract Plastic-bonded explosives (PBXs) with different amounts of polymer and based on explosives with different particle size distributions have been compared for their thermal properties and shelf life. Chung Shan Institute of Science and Technology has extensive experience with the processing of hydroxyl terminated polybutadiene (HTPB)-based PBXs. The investigation showed that the shelf life of HMX-based formulations is longer than 60 years at ambient temperature. The thermal properties of three HMX-based formulations such as specific heat, linear thermal expansion coefficient, auto-ignition temperature and kinetic parameters concerning the explosion, explosion temperature, etc. are very close with the exception of glass transition temperature.

The devitrification behavior of calcium phosphate glass with TiO2 addition

Abstract The effects of TiO 2 addition on the devitrification behavior of the calcium phosphate glasses were investigated using thermal analysis techniques. Both the DTA traces of coarse powder and fine powder for calcium phosphate glasses indicated that the glass transition temperature ( T g ), gradually increased. To determine whether the devitrification begins at the surface or in the bulk of these glasses, we recorded DTA curves of coarse powder and fine powder. By comparing the exothermic peak temperature of coarse powder and fine powder, we found that the two exothermic peak temperatures tend to be nearer when the amount of TiO 2 in calcium phosphate is increased. This indicates that bulk devitrification or, more appropriately, devitrification at the internal interface is easier, i.e., TiO 2 is an effective nucleating agent in these glass systems.

The DSC studies on the phase transition, decomposition and melting of potassium perchlorate with additives

Abstract It has been shown that the addition of metal oxide to potassium perchlorate gives rise to change in the thermochemical behavior of the potassium perchlorate. Some investigations on the particle sizes and materials were examined, and given data for choosing optimum weight percentage to achieve certain firing characteristics of hot-wire pyrotechnic devices. In this study, the additives (Al 2 O 3 and Fe 2 O 3 ) are found to have no effect on the crystal structure transformation, the fusion of KClO 4 and the fusion of KCl. But both of the metal oxide powders exhibited a remarkable acceleration effect on the decomposition of KClO 4 , especially Fe 2 O 3 does.

Thermal and microstructural characterizations of nickel nanoparticles at elevated temperatures

Abstract The isothermal oxidation behavior and the oxidized structure of nanometer-sized nickel powders have been investigated over a temperature range 300–1100 °C in ambient air. The oxidation began at about 300 °C and the weight gain increased linearly as the isothermal time lengthened. The isothermal oxidation kinetics became parabolic as the temperature was raised above 500 °C. A nickel chromium oxide (NiCr 2 O 4 ) was formed in addition to the nickel oxide (NiO) as the temperature exceeded 700 °C, due to the presence of chromium as a major impurity in the as-received nickel nanoparticles. A reaction of NiO+Cr 2 O 3 →NiCr 2 O 4 was suspected to occur concurrently in addition to the Ni+1/2O 2 →NiO oxidation reaction at the temperatures (≥700 °C) involved.