Thermal Decomposition Of Sodium Azide Research Articles

Preparation of GaN Single Crystals Using a Na Flux

GaN single crystals were prepared in a sealed stainless steel tube at 600−800 °C from Ga using a Na flux and N2 from the thermal decomposition of sodium azide, NaN3. The maximum size of the crystals obtained was 2 mm. Oxygen and other impurity elements were not detected in the crystals by AES and EDX. When scaled up, this method may provide large GaN crystals for use as substrates for nitride based lasers.

Magnetic and structural characterization of superconducting sodium-doped C60 prepared with the thermal decomposition of sodium azide

Abstract We have prepared Na4C60 samples by the different ways of the thermal decomposition of sodium azide NaN3. The superconducting (SC) samples were obtained by the decomposition under the dynamic vacuum, while the non-SC samples by the decomposition in the sealed tube. The SC sample was composed of two fee phases with a lattice constant a=14.207(5)A (phase A) and a=14.339(4)A (phase B). On the contrary, the non-SC sample had single fee phase which can be assigned to phase A. This result strongly suggests that phase B is the SC phase.

Thermal analysis of sodium azide

The thermal reaction and decomposition of sodium azide were affected by the gas species, its pressure, sample type (powdered or tablet), par- ticle size, sample weight, surface heterogeneity, additives, aging, etc. In actual experiments, very complicated problems arose because those effects were combined together. In addition, it was determined that heat and mass transfer effects must also be considered when evaluating the thermal reactivity of sodium azide and its mixture. In this report, the thermal decomposition of sodium azide was mainly studied by thermal analysis, and the factors which affect its thermal properties were discussed.

New superconducting sodium-nitrogen-C 60 ternary compound

We have prepared sodium-doped C 60 utilizing the thermal decomposition of sodium azide (NaN 3). The strong low-magnetic field microwave absorption with a clear hysteresis was observed in the samples of Na nC 60 ( n=3∼4), indicating the superconducting nature. By means of a SQUID measurement, the superconducting transition temperature is found to be around 12 K. Significantly, elemental analysis detected a nitrogen which was surely produced in the process of the thermal decomposition of NaN 3. We suppose that this new superconducting phase will be Na xN yC 60 where x is between 3 and 4, and y is unknown. This is the first superconducting material in Na-doped C 60 without other alkali metals.

The affect of pretreatment and of Mn(II) doping on the thermal decomposition of sodium azide

The affect of pretreatment and of Mn(II) doping on the thermal decomposition of sodium azide

Thermal decomposition of sodium azide

The thermal decomposition of sodium azide has been investigated in the temperature range 240–365°C. Three values for the activation energy, 37.0, 59.0 and 14 kcal mol −1 have been obtained depending on the temperature range of study. The mechanism of decomposition seems to involve excited azide ions (through internal conversion) and excitations. The activation energy of 14 kcal mol −1 appears to be associated with the promotion of electron in the presence of sodium metal.

Incomplete decomposition of alkali metal azides

The thermal decomposition of sodium azide has been studied in the temperature range 240–360°C in vacuum and under pressure of an inert gas, argon. The results show that the decomposition is partial 360°C. From the observations made in the present work, namely: (i) the decomposition is incomplete both under vacuum and inert gas; (ii) mass spectrometric studies do not reveal any decrease in the intensity of the background species, CO + 2, CO +, H 2O +, and (iii) sodium metal remains in the ‘free state’ as seen by the formation of a metallic mirror at temperatures above 300°C, it has been argued that the partial nature of decompostion is due to the confinement of the decomposition to intermosaic regions within the lattice.

Thermal decomposition of sodium azide: Crystal size effects, topochemistry and gas analyses

The kinetics of thermal decomposition of sodium azide are shown to be dependent on the specific surface area of crystals. Decomposition commences at the edges of crystal platelets and advances inward in directions parallel to the alternating planes of sodium and azide ions. The acceleration and decay of the decomposition after an initial first stage is dependent on the development of a closed two-dimensional envelope at the crystal edges and a subsequent contraction of the envelope. The boundary between decomposed and undecomposed material is indicated by three colored zones of the sodium decomposition product in different states of aggregation. With crystals grown slowly from aqueous solutions a residue remains when crystals are decomposed at temperatures up to 370°C. Residual gas analyses during decomposition suggest that the residue results from a back reaction between impurity gases such as H 2O 2, CO and CO 2 and the sodium, and the deposition of the more stable compounds on islands of undecomposed azide. At higher temperatures than 370°C, where NaOH is appreciably volatile, little residue remains.

Dielectric investigation of the thermal decomposition of sodium azide

The thermal decomposition of sodium azide has been investigated by monitoring changes in dielectric constant, dielectric loss, and pressure with time at a fixed frequency during decomposition at 262–305°C, and by monitoring changes in dielectric properties with frequency in the range 100 Hz to 300 kHz for samples cooled to 20°C after partial decomposition at 290°C. Curves of ε′ and ε″ against time both show maxima at the stage where the fractional decomposition α shows a marked increase. Three stages of decomposition (A, B and C) can be identified for α < ca. 0.02, and activation energies for the three stages and for two types of sodium azide vary between 28.0 and 73.4 kcal/mole. At 100 kHz, and during stage B, changes in ε′ and ε″ are both related to changes in α by simple power laws, the exponents for which show an approximate linear decrease with increasing temperature. At frequencies below ca. 1 kHz, d.c. conductance is mainly responsible for the dielectric loss, whereas at higher frequencies Debye or Maxwell-Wagner type relaxation processes predominate. The difference in static dielectric constant at 20°C between partially decomposed and undecomposed samples is directly proportional to α2 for values of α corresponding to stage B. Changes in dielectric properties during decomposition are discussed in terms of “dipoles” involving the defect structure of the solid.

Thermal decomposition of sodium azide: Crystal size effects, topochemistry, and gas analyses

Thermal decomposition of sodium azide: Crystal size effects, topochemistry, and gas analyses