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Preparation of Nano Aluminium Powder (NAP) using a Thermal Plasma: Process Development and Characterization

Pant A., Seth T., Raut V. B., Gajbhiye V. P., Newale S. P., Nandi A. K., Prasanth H., Pandey R. K.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 1

53--71

EN

A bottom up approach for the preparation of Nano Aluminium Powder (NAP) using a Transferred Arc Thermal Plasma Reactor (TAPR) is described. The aluminium block is subjected to evaporation by the application of a thermal plasma. The aluminium vapour produced is rapidly quenched to room temperature resulting in crystallization of the aluminium vapour in nano-particulate form. Various process parameters, such as the plasma torch power, reactor pressure and plasma gas composition were optimized. This paper also describes the characterization of NAP by analytical methods, for the estimation of the Active Aluminium Content (AAC), Total Aluminium Content (TAC), XRD, bulk density, BET surface area, HR-TEM etc. The results are compared with those for samples prepared in other thermal plasma reactors, such as the DC Arc Plasma Reactor (DCAPR) and the RF Induction Thermal Plasma Reactor (RFITPR), and for commercially available NAP samples (ALEX, prepared by the EEW technique).

2

Process Optimization for the Gas-Liquid Heterogeneous Reactive Crystallization Process Involved in the Preparation of the Insensitive High Explosive TATB

Nandi A. K., Kshirsagar A. S., Thanigaivelan U., Bhattacharyya S. C., Mandal A. K., Pandey R. K., Bhattacharya B.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 1

31--57

EN

The thermally stable, insensitive, high explosive 1,3,5-triamino-2,4,6- trinitrobenzene (TATB) is manufactured by amination of 1,3,5-trichloro-2,4,6- trinitrobenzene (TCTNB) in toluene with NH3 gas. It is an isothermal, single-feed, semi-batch, gas-liquid heterogeneous, reaction crystallization process. The amination process is discussed by applying the chemical engineering methodology of mass transfer and reactive crystallization processes based on Two-Film Mass- Transfer (TFMT) theory. Kinetic expressions have been developed to define the chemical reactions as well as the physical phenomena (mass transfer) associated with this process. A single expression has been derived to explain the dependence of the ammonia consumption rate on various process parameters. Subsequently, the influence of various process parameters on the product quality (particle size and chloride impurity content) has been studied on the laboratory scale. Finally, the process has been established in the pilot plant, with optimized process conditions, to realize TATB of desired particle size and chloride content. The effects of feeding excess ammonia, and the presence of mercaptans/hydrogen sulphide impurities in poor quality toluene on the formation of certain undesirable by-products in TATB, are also discussed.

3

Optimization of Ammonium Sulfamate Nitration for the Preparation of Ammonium Dinitramide

Mandal A. K., Kunjir G. M., Singh J., Adhav S. S., Singh S. K., Pandey R. K., Bhattacharya B., Lakshmi Kantam M.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 1

83--97

EN

The reaction kinetics for the preparation of ammonium dinitramide (ADN) is described. ADN is the ammonium salt of the dinitramide anion, and belongs to the group of inorganic oxidizers, mainly useful for energetic rocket propellant formulations, particularly for underwater applications. It is also a potential candidate to replace ammonium perchlorate (AP), in order to develop chlorine-free, green propellants. At HEMRL, ADN is prepared by the nitration of ammonium sulfamate (AS) using mixed acid, followed by hydrolysis, neutralization with ammonia (g) and rectification using solvent. The nitration of ammonium sulfamate (AS) is carried out at a subzero temperature of -40 ±1 °C. The yield of ADN is reliant on the formation of dinitramidic acid, an intermediate product formed during the hydrolysis step, and its stability is predominantly dependent upon the level of acidity and temperature of the reaction medium. Prior to these kinetics studies, process optimization of the nitration of ammonium sulfamate (AS) was performed and gave the final mole ratio of AS:HNO3:H2SO4. Since the nitration of AS is sensitive to temperature, the rate of reaction was studied at fixed temperatures with variation of time, keeping all of the other parameters, such as vessel volume, agitator speed, feed rate etc., constant. During these studies, predetermined quantities of ammonium sulfamate (AS) and mixed acid were allowed to react at a fixed temperature (-40 ±1 °C) for different reaction periods to generate the concentration profile of AS. Using this concentration profile, the reaction order and reaction rate constant were evaluated. In order to find the effect of temperature on the reaction rate and yield, experiments were conducted at other temperatures such as -30 and -50 °C. In the present studies, it was found that the optimum temperature of nitration is -40 ±1 °C and that the rate of reaction follows a pseudo second order process with rate constant 0.01113 (min-1)•(mol/L)-1. The reaction time evaluated for 55 to 60% conversion is about 70-80 minutes at -40 ±1 °C, based on this kinetics. The activation energy of AS nitration was found to be -4.6 kcal/mol, using the reaction kinetic data based on the temperature dependent rate equation derived from Arrhenius’s law.

4

Modelling and optimization of temperature in orthopaedic drilling : An in vitro study

Pandey R. K., Panda S. S.

Acta of Bioengineering and Biomechanics

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2014

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Vol. 16, no. 1

107--116

EN

This present investigation uses the Taguchi and response surface methodology (RSM) for modelling and optimization of the temperature produced during bone drilling. The drilling of bone is a common procedure in orthopaedic surgery to produce hole for screw insertion to fixate the fracture devices and implants. A major problem which is encountered during such a procedure is the increase in temperature of the bone due to the plastic deformation of chips and the friction between the bone and the drill. The increase in temperature can result in thermal osteonecrosis which may delay healing or reduce the stability and strength of the fixation. The drilling experiments are conducted on poly-methyl-meth-acrylate (PMMA) (as a substitute for bone) using Taguchi’s L27 experimental design technique. The cutting parameters used are drill diameter, feed rate and cutting speed. The optimum cutting parameters for minimum temperature are determined by using S/N ratios and the effect of individual cutting parameters on temperature produced is evaluated using analysis of variance (ANOVA). A second-order model is established between the drilling parameters and temperature using RSM. The experimental results show that the drill diameter is the most significant drilling parameter affecting the temperature during drilling followed by cutting speed and feed, respectively. The values predicted and the values obtained from experiment are fairly close, which indicates that the developed RSM model can be effectively used to predict the temperature in orthopaedic drilling.

5

Preparation and characterization of ultrafine RDX

Pant A., Nandi A. K., Newale S. P., Gajbhiye V. P., Prasanth H., Pandey R. K.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 3

393--407

EN

This paper describes the synthesis of ultrafine Hexogen (UF-RDX) of size <5μm by drowning-out crystallization. RDX was precipitated from acetone or dimethylformamide (DMF) solution by reducing the solvent power using either a miscible, non-aqueous antisolvent, n-hexane, or an aqueous antisolvent, water containing polyethylene glycol (PEG). Process parameters such as solvent/ antisolvent ratio, agitation, ultrasonication etc. were studied. UF-RDX was characterized for Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and sensitivity tests. In the case of the non-aqueous antisolvent, the precipitated RDX crystals were rod shaped of diameter <1 μm. For the aqueous antisolvent, oval shaped crystals (<5 μm) were precipitated. UF-RDX was found to be more sensitive to impact and less friction sensitive compared to production grade RDX (60-80 μm).

6

Assay of the Insensitive High Explosive 3-Nitro-1,2,4-triazol-5-one (NTO) by Acid-Base Titration

Nandi A. K., Singh S. K., Kunjir G. M., Singh J., Mandal A. K., Pandey R. K.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 1

113--122

EN

The insensitive high explosive 3-nitro-1,2,4-triazol-5-one (NTO) is a weak acid (pKa 3.76) due to the labile N–H bond. The weakly acidic character of this compound is exploited for its assay by aqueous acid-base titration. The NTO sample was dissolved in water and the resultant solution was titrated against 0.07 N NaOH solution using phenolphthalein as indicator. Regular batch samples were assayed by this method and the results were compared with those obtained by the HPLC method. The aqueous acid-base titration method was found to be suitable for the quality control of the product.

7

Surface Coating of Cyclotetramethylenetetranitramine (HMX) Crystals with the Insensitive High Explosive 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB)

Nandi A. K., Ghosh M., Sutar V. B., Pandey R. K.

Central European Journal of Energetic Materials

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2012

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Vol. 9, nr 2

119-130

EN

A method to crystallize the thermally stable, insensitive high explosive, 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) onto the surface of another high explosive cyclotetramethylenetetranitramine (HMX) crystal is described. Amination of 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) in toluene produces TATB which is precipitated by a reactive crystallization process. When the reaction is carried out in the presence of HMX, TATB crystals are found to be deposited onto the HMX crystal surface. This phenomenon was utilized to obtain in situ surface coating of HMX crystals with TATB. Both the conventional amination and the sonochemical amination methods, using dry ammonia (NH3) gas and ammonium hydroxide (NH 4 OH) respectively as the aminating agents, were studied. The coated materials were characterized by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Simultaneous Thermal Analysis (STA) and sensitivity tests. The results were compared with those of the virgin materials. Sonochemical amination provided a uniform coating of the HMX crystals. Coated HMX has shown substantial friction insensitivity gain as compared to uncoated HMX. However there is a drop in impact insensitivity in the coated materials.

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Formation of Boric Acid by Surface Oxidation of Amorphous Boron Powder: Characterization and Quantitative Estimation

Nandi A. K., Ghosh M., Newale S. P., Jadhav A. J., Prasanth H., Pandey R. K.

Central European Journal of Energetic Materials

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2012

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Vol. 9, nr 4

387-398

EN

Amorphous Boron Powder (ABP) is used as a fuel in air breathing propulsion systems due to its high gravimetric and volumetric heat value. ABP is sensitive to air and undergoes slow oxidation during storage and handling, leading to the formation of a boric acid layer on the particle surface. This paper describes an analytical method for the estimation of boric acid in ABP. In-house samples obtained from the pilot plant of this laboratory, as well as commercial samples, were assayed for their boric acid content. The study is substantiated by characterization of the ABP samples by SEM with EDX and FTIR. The ageing characteristics of in-house boron powder was also studied.

9

Assay of the Insensitive High Explosive FOX-7 by Non-Aqueous Titration

Nandi A. K., Paramasivan P., Singh S. K., Mandal A. K., Pandey R. K.

Central European Journal of Energetic Materials

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2012

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Vol. 9, nr 4

343-352

EN

A non-aqueous titration method was developed to assay the insensitive high explosive 1,1-diamino-2, 2-dinitroethene (FOX-7). The weak acidic nature of FOX-7 (pKa 10.6) was exploited in the assay method. The sample was dissolved in the protophilic solvent N, N-dimethylformamide and titrated against sodium methoxide solution in benzene/methanol using azo violet as indicator. FOX-7 samples obtained from regular batch operations were assayed by this method and the results were compared with that of a recrystallized sample. The method is simple, rapid and has good accuracy and precision.