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Biomedical subjects

S Venugopalan

Publications and source records attributed to S Venugopalan.

11 recordsLinked to original sources
PubMed2006

Preparation and thermal studies on tetranitrodibenzo tetraazapentalene (TACOT): a thermally stable high explosive.

Thermally stable high explosive, tetranitro-2,3,5,6-dibenzo-1,3a,4,6a-tetraazapentalene (TACOT) was synthesized and characterized during this work. Thermo analytical techniques (TG and DSC) were applied to study the thermal decomposition behaviour of TACOT in comparison with benchmark thermally stable high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Kinetic parameters such as reaction order, activation energy and pre-exponential factors were computed from the thermal data. The activation energy for TACOT (292 kJ/mol) was found 1.5 times to that of TATB (200 kJ/mol), which can account for its higher thermal stability and can be attributed to pentalene moiety in the former.

Aza Compounds↗
PubMed2006

Study on ultrasound assisted precipitation of CL-20 and its effect on morphology and sensitivity.

Applying ultrasound to crystallizing systems offers significant advantages for modifying and improving the processes as well as quality of products. This paper reports on ultrasound assisted reprecipitation of CL-20 to obtain fine particles as well as to achieve desired morphology, which will improve insensitivity characteristics. In this study, CL-20 has been reprecipitated by sonication process and has been characterized by DSC, SEM and particle size analysis. The results are compared with control CL-20 sample (unsonicated). SEM photographs revealed that sonication process offer uniform crystalline morphology without any agglomeration. The particle size of sonicated CL-20 sample obtained is around 5+/-1 microm with a narrow particle size distribution. The DSC thermogram of sonicated and unsonicated sample is identical. CL-20 samples were subjected to impact and friction sensitivity experiments, the results indicate the sensitivity characteristics reduced considerably. Ultrasonic assisted crystallization technique reduces the time of reprecipitation considerably with an enhanced recovery of CL-20 with a very narrow particle size distribution.

Aza Compounds↗
PubMed2006

Method for preparation of fine TATB (2-5 microm) and its evaluation in plastic bonded explosive (PBX) formulations.

There is a need of fine 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) (2-5 microm) for various high explosive formulations to achieve desired mechanical strength, ease in processing and finally, provide better performance of end product. The reprecipitation method for TATB has been developed using concentrated sulfuric acid as a solvent. The reprecipitation parameters of TATB were optimized to achieve required fine TATB of particle size approximately 2-5 microm. The characteristic properties of fine TATB thus obtained have been confirmed by FTIR, DSC and TG-FTIR. The spectroscopic and thermal data obtained for fine TATB were compared with standard coarse TATB and found chemically unchanged during particle size reduction. In the present study, the preparation of fine TATB was also attempted using ultrasonication method. The fine (2-5 microm) TATB has been introduced to study in the bimodal high explosive formulations. High explosive formulations based on coarse (55 microm) and fine TATB ( approximately 2-5 microm) with 10% polyurethane were studied. It was observed that properties like bulk density (1.70 g/cm(3)), mechanical strength/compressed strength (115.9 mg/cm(2)), %elongation (6.36) were improved for fine TATB in comparison with coarse TATB ( approximately 55 microm) alone in high explosive formulations.

Calorimetry, Differential Scanning↗
PubMed2006

Synthesis, characterization and thermolysis of 1,1-diamino-2,2-dinitroethylene (FOX-7) and its salts.

The present paper discusses the efforts made in HEMRL to establish the synthesis of FOX-7 at 100 g/batch level. In the present study, 1,1-diamino-2,2-dinitroethylene has been synthesised by treatment of acetamidinium chloride with diethylmalonate to obtain 2-methyl-pyrimidine-4,6-dione which on nitration followed by hydrolysis gave FOX-7. The synthesised FOX-7 has been characterized by spectroscopic and thermal techniques. The data obtained confirms the structure of FOX-7. The sensitivity of FOX-7 towards mechanical stimuli indicated its insensitive nature. The theoretically computed explosive and ballistic parameters are close to that of RDX. The synthesised FOX-7 has been used as a precursor for the synthesis of potassium and guanidinium salts and the thermal analysis of these salts indicate their exothermic nature.

Ethylenes↗
PubMed2006

Synthesis, characterization and thermolysis studies on triazole and tetrazole based high nitrogen content high energy materials.

This paper reports the synthesis, characterisation and thermolysis studies of hydrazinium azotetrazolate (HAZ) and 1,1'-dinitro-3,3'-azo-1,2,4-triazole (N-DNAT). TGA and DSC results suggested that HAZ decomposes in the range of 150-180 degrees C and N-DNAT in the range of 160-170 degrees C, respectively. The pattern of decomposition of HAZ dihydrate and N-DNAT has been predicted with the help of pyrolysis GC/MS technique and a probable decomposition mechanism has been proposed. The theoretically predicted performance data suggests the potential nature of HAZ and N-DNAT for their use in propellant/explosive as well as in gas generator formulations.

Hot Temperature↗
PubMed2006

Computer code for the optimization of performance parameters of mixed explosive formulations.

LOTUSES is a novel computer code, which has been developed for the prediction of various thermodynamic properties such as heat of formation, heat of explosion, volume of explosion gaseous products and other related performance parameters. In this paper, we report LOTUSES (Version 1.4) code which has been utilized for the optimization of various high explosives in different combinations to obtain maximum possible velocity of detonation. LOTUSES (Version 1.4) code will vary the composition of mixed explosives automatically in the range of 1-100% and computes the oxygen balance as well as the velocity of detonation for various compositions in preset steps. Further, the code suggests the compositions for which least oxygen balance and the higher velocity of detonation could be achieved. Presently, the code can be applied for two component explosive compositions. The code has been validated with well-known explosives like, TNT, HNS, HNF, TATB, RDX, HMX, AN, DNA, CL-20 and TNAZ in different combinations. The new algorithm incorporated in LOTUSES (Version 1.4) enhances the efficiency and makes it a more powerful tool for the scientists/researches working in the field of high energy materials/hazardous materials.

Algorithms↗
PubMed2006

Diaminofurazan (DAF): Thermolysis and evaluation as ballistic modifier in double base propellant.

Diaminofurazan (DAF) is used as a precursor in the synthesis of many high performance insensitive high explosives. This paper reports the thermal studies on DAF and its evaluation as a ballistic modifier in double base propellant formulations. Differential scanning calorimetry (DSC) and differential thermal analysis (DTA) revealed that DAF shows two-stage decomposition, whereas the kinetics of initial stage of thermal decomposition of DAF evaluated from TG data gave activation energy (E(a)) of 67 kJ mol(-1). The evolution of gases containing species such as CN, NH, OH and oxides of nitrogen during thermal decomposition of DAF was also revealed by hyphenated TG-FTIR data. Evaluation of DAF as a ballistic modifier in RDX incorporated double base propellant formulations indicated that it brings down the pressure index to 0.20 compared to 0.70 for a control composition in the pressure range 6.9-8.8 MPa when used in combination with basic lead salicylate (BLS). It was observed that DAF does not have adverse effect on vulnerability and chemical stability of the propellant formulation.

Calorimetry, Differential Scanning↗
PubMed2005

Prediction of heat of formation and related parameters of high energy materials.

Heat of formation is one of the most important parameters in the performance prediction of explosive and propellant formulations and their individual ingredients. This paper reports the development of user-friendly computer code for the prediction of heat of formation based on two approaches. In first methodology, the logic of Benson's Group additivity method and in the second method, the logic of Pedley method was used for predicting the heats of formation of high energy materials (HEMs). The predicted heats of formation by Benson method for various classes of high energy materials gave deviation in the range of 2-10%, whereas nearly 10-15% deviation was observed using Pedley methodology in comparison to experimental values. The linear regression coefficient values (R(2)) of 0.9947 and 0.9637 are obtained for heat of formation values predicted by this code using methodologies I and II, respectively. The newly developed code LOTUSES (version 1.3) has been validated by calculating the heats of formation of standard explosives such as TNT, pentaerythritol tetranitrate (PETN), RDX, HMX, etc., To the best of our knowledge, no such code is reported in literature which can predict heats of formation values integrated with performance parameters of HEMs belonging to all categories of organic compounds viz. aliphatic, aromatic and heterocyclic materials. The code can also be used to obtain parameters such as velocity of detonation, C-J pressure, volume of explosion products, power index, temperature of explosion and oxygen balance of HEMs. The code has been developed in Visual Basic having enhanced Windows environment. This software namely LOTUSES 1.3 is an updated version of the earlier ones namely LOTUSES 1.1 and 1.2 which do not cater for the calculation of heat of formation and temperature of explosion of HEMs. LOTUSES 1.3 is, therefore, a totally integrated software for computing most of the vital parameters of HEMs requiring mainly the molecular structural information of an explosive under consideration.

Energy-Generating Resources↗