CRYSTALLOGRAPHIC DATA. 36. Cyclotetramethylene Tetranitramine (HMX)

McCrone, Walter C.

doi:10.1021/ac60045a050

Cited by 78 publications

(47 citation statements)

References 3 publications

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“…In addition, a very small number of crystals exhibited a bulky prismatic habit with (101) faces very small and sometimes absent. The morphology of the last were similar to those described by McCrone [8] and by Palmer and Field [9]. Typically the smaller crystals were 6 mm along the longest dimension, although several larger crystals up to a maximum size of 21×10×8 mm 3 were also obtained.…”

Section: Resultssupporting

confidence: 80%

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Growth and dislocation studies of β-HMX

Gallagher

Sherwood

Vrcelj

2014

Chemistry Central Journal

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BackgroundThe defect structure of organic materials is important as it plays a major role in their crystal growth properties. It also can play a subcritical role in “hot-spot” detonation processes of energetics and one such energetic is cyclotetramethylene-tetranitramine, in the commonly used beta form (β-HMX).ResultsThe as-grown crystals grown by evaporation from acetone show prismatic, tabular and columnar habits, all with {011}, {110}, (010) and (101) faces. Etching on (010) surfaces revealed three different types of etch pits, two of which could be identified with either pure screw or pure edge dislocations, the third is shown to be an artifact of the twinning process that this material undergoes. Examination of the {011} and {110} surfaces show only one type of etch pit on each surface; however their natural asymmetry precludes the easy identification of their Burgers vector or dislocation type. Etching of cleaved {011} surfaces demonstrates that the etch pits can be associated with line dislocations. All dislocations appear randomly on the crystal surfaces and do not form alignments characteristic of mechanical deformation by dislocation slip.ConclusionsCrystals of β-HMX grown from acetone show good morphological agreement with that predicted by modelling, with three distinct crystal habits observed depending upon the supersaturation of the growth solution. Prismatic habit was favoured at low supersaturation, while tabular and columnar crystals were predominant at higher super saturations. The twin plane in β-HMX was identified as a (101) reflection plane. The low plasticity of β-HMX is shown by the lack of etch pit alignments corresponding to mechanically induced dislocation arrays. On untwinned {010} faces, two types of dislocations exist, pure edge dislocations with b = [010] and pure screw dislocations with b = [010]. On twinned (010) faces, a third dislocation type exists and it is proposed that these pits are associated with pure screw dislocations with b = [010].Graphical abstractEtch pits on the twinned (010) face of β-HMX.

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Section: Resultssupporting

confidence: 80%

“…McCrone [8] obtained massive crystals exhibiting forms {110}, {011}, and {101} by crystallization from acetic acid, acetone, nitric acid and nitromethane. As part of their studies on mechanical deformation of β-HMX, Palmer and Field [9] grew crystals with typical dimensions 5×5×3 mm 3 by solvent evaporation from acetone solution.…”

Section: Introductionmentioning

confidence: 99%

Growth and dislocation studies of β-HMX

Gallagher

Sherwood

Vrcelj

2014

Chemistry Central Journal

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“…HMX exists in four solid phase polymorphs, labeled α, β, γ, and δ-HMX [9], each of which can be prepared by a specific cooling rate of the reaction solution [10]. The phase conversion of the β phase (monoclinic lattice structure) to the δ phase (hexagonal lattice structure) involves a major disruption of the crystal lattice and a ring conformation change long-term storage.…”

Section: Introductionmentioning

confidence: 99%

Coefficient of Thermal Expansion of the Beta and Delta Polymorphs of HMX

Weese

Burnham

2005

Propellants, Explosives, Pyrotechnics

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Dimensional changes related to temperature cycling of the β and δ polymorphs of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are important for a variety of applications. The coefficient of thermal expansion (CTE) of the β and δ phases are measured over a temperature range of -20˚C to 215˚C by thermo-mechanical analysis (TMA). Dimensional changes associated with the phase transition were also measured, and the time-temperature dependence of the dimensional change is consistent with phase transition kinetics measured earlier by differential scanning calorimetry (DSC). One HMX sample measured by TMA during its initial heating and again three days later during a second heating showed the β-to-δ phase transition a second time, thereby indicating back conversion from δ-to-β phase HMX during those three days. DSC was used to measure kinetics of the δ-to-β back conversion. The most successful approach was to first heat the material to create the δ phase, then after a given period at room temperature, measure the heat absorbed during a second pass through the β-to-δ phase transition. Back conversion at room temperature follows nucleation-growth kinetics.

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“…The polymorphic forms of HMX are well reported in the literature [5]. The ␤ polymorph of HMX is reported to exist in chair conformation while that of ␣, ␥ and ␦ phases exist in chair-chair conformation [6].…”

Section: Introductionmentioning

confidence: 74%