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Resonant Acoustic Mixing and its applications to energetic materials



Resonant Acoustic Mixing (RAM) is a technology developed by ResoDyn Corporation which provides a low-energy contactless mixing system. This paper examines how the RAM technology can be applied to the processing of energetic materials and provides a comparison with conventional mixing techniques. Through research carried out to date, it has been established that RAM technology offers several advantages over traditional mixing techniques, especially where energetic materials are concerned. The main advantage lies in the relatively gentle mechanism of the RAM technique, where only minor damage occurs to sample particulates, with no blades or impellers being used in the process. The extent of particle damage encountered has been assessed by scanning electron microscopy, and shown that very little shear occurs during mixing at low accelerations. The process is also relatively thermally benign, although some temperature excursions have been encountered. Work has been undertaken to prepare energetic co-crystals and salts using a solvent-drop approach in the RAM, offering advantages in terms of diverse container compatibility and fast processing time.
... The co-crystal ( Figure 1a, space group P2 1 /c) was prepared using a ResoDyn LabRAM Resonant Acoustic Mixer (RAM, Figure 2) -a low-frequency (60 Hz) shaker/sonication technology [10] -following a method published by Nalas Engineering [11]. This method was chosen over the more well-known evaporative method for reasons of time and as a test of the RAM's known co-crystallisation capabilities [12]. ...
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Two energetic co-crystal systems have been investigated under pressure using neutron powder diffraction – 2(CL-20):HMX, and nitroguanidine:2-hydroxy-3,5-dinitropyridine (NQ:DNP). The 2(CL-20):HMX co-crystal was prepared with a ResoDyn LabRAM Resonant Acoustic Mixer using a published method. Neutron diffraction experiments were performed on the PEARL beamline at the ISIS Neutron Source in Harwell, Oxfordshire. Compression was observed in this system up to 3.5 GPa broadly in line with the results of DFT-D calculations, and equations of state were determined from the experimental data. No phase transitions were observed during the experiment. The NQ:DNP co-crystal was prepared by solvothermal co-crystallisation, and neutron diffraction experiments were also performed on the PEARL beamline. A potential phase transition was observed between 1.0 and 1.4 GPa. The crystal structure of this high- pressure phase is currently under investigation.
The paper presents a view on the achievements, challenges and prospects of mechanochemistry. A major reference list can serve as a good entry point to a plethora of mechanochemical literature.
Resonance Acoustic Mixing ® (RAM) technology applies an external low-frequency vertical harmonic vibration to convey and mix the non-Newtonian fluid across space. However, although this method is used for various applications, its mechanism is yet not well understood. In this paper, we investigate the Faraday instability of power-law non-Newtonian fluids in RAM utilizing theory and simulations. According to the Floquet analysis and the dimensionless Mathieu equation, the critical stable region besides the stable region and the unstable region is discovered. Based on the numerical solutions of the two-dimensional incompressible Euler equations for a prototype Faraday instability flow, the temporal evolution of the surface displacement and the mechanism of Faraday waves for two cases are explored physically. For the low forcing displacement, there are only stable and critical stable regions. The surface deformation increases linearly and then enters the steady-state in which the fluctuation frequency is twice the vertical harmonic vibration. For the large forcing displacement, there are only stable and unstable regions. Under the effect of the inertial force, both cases have a sudden variation after the brief stabilization period. Furthermore, a ligament structure is observed, which signals that the surface is destabilized. In addition, a band-like pressure minimum distribution below the interface is formed. The fluid flows from the bottom to the crest portion to balance the pressure difference, which raises the crest.
To solve the problems of poor mixing consistency, low preparation efficiency and serious material waste of trace and high solid content explosive inks, this paper proposes a new preparation process by combining Resonant Acoustic-Mixing technology with rheological apparent viscosity. The experimental results showed that the mixing acceleration and the shape of the mixing container only affected the mixing efficiency. The temperature sensitivity of the material at 45 to 60 °C was significantly higher than that of 30 to 45 °C, and the ink viscosity value changed greatly. Under the best preparation process route, the ink could be prepared in only 5 min. The ink-finished product prepared under the above-mentioned optimal technology had almost no change in its crystal shape, thermal properties, and sensitivity compared with paddle stirring. In this paper, the possibility of preparing explosive inks from RAM is practiced, and the powerful mixing ability of RAM is verified.Graphical abstract
Intensive research subjected to the improvement of solubility and bioavailability of certain drugs has popularized the formation of cocrystals, wherein the desired drug is non-ionically bonded to a coformer by means of weak bonds. This paper addresses how crystal engineering of two compatible drug components can enhance the physicochemical and therapeutic properties of either or both of the drugs, resulting in drug-drug cocrystals, with pertinent examples. The paper also discusses the continuous screening processes which are replacing the traditional methods of crystallization due to numerous benefits to the producer as well as the products. Although faced with certain regulatory and scale-up constraints, cocrystals provide immense opportunities to the field of novel drug development.
This study is a structured literature review of published ResonantAcoustic® Mixing (RAM) literature, considering the benefits and constraints of using RAM. Focussing on how this will affect the future production of rubbery composite rocket propellants. The main benefits of RAM were found to be shorter mixing time, versatility of mixing and ability to mix higher viscosities than conventional mixers. Facilitating the next generation of composite propellants with improved performance and mechanical properties. Mixed in‐situ RAM overcomes viscosity limitations by removing the casting process and has safety and environmental benefits, but does need to be tested at larger production scales. The implications of RAM production on the energetics qualification process was considered. A new framework was discussed based on understanding the entire product development process including ingredient properties, manufacturing processes, and linking this to product performance; through adoption of a digital twin approach with in‐situ monitoring. Future R&D focuses on process and material control through a validated model of the mixing mechanisms, linked to material properties and output performance. Validation with scaled up comparative studies and continuous in‐situ monitoring. A full list is provided in the conclusions. Overall RAM offers numerous benefits to mixing existing and new materials with large savings in time, cost, improved safety and is more environmentally friendly.
The solid forms of pharmaceutically relevant compounds are technologically important. Correspondingly, extensive efforts have been devoted to the development of methods capable of monitoring the formation and growth of solid forms. When following solid‐state transformations, one typically aims to understanding the rate of formation of the solid, and the physical form of the solid being prepared. The choice of analytical method depends on both the process being monitored, and the type of information regarding the solid form that is desired. This chapter introduces the major techniques used to follow solid‐state transformations in solution and during mechanochemical treatment. For each technique, a brief introduction to the underlying theory is provided, along with technique‐specific considerations for their applications in process monitoring and a set of illustrative examples. Finally, this chapter highlights how the combined use of multiple techniques can provide the necessary insights to fully characterize and control solid formation.
Nanothermites are the most important family of energetic materials in contemporary pyrotechnics. This article traces the main research which was carried out in this still recent domain and the challenges that remain to be overcome. The academic effort of past two decades has brought nanothermites from the status of laboratory curiosities to the one of pre‐industrial materials. Different aspects of nanothermites are discussed in order to provide valuable information to scientists experimenting in this domain. Experimental details on the preparation and the disposal of nanothermites are reported. The current research on nanothermites deals with: (i) the development of new aluminothermic mixtures; (ii) the preparation of hybrid compositions by combining nanothermites with explosive nanopowders and (iii) the study of reactive properties. From an academic standpoint, the future challenges are to find new compositions and effects. From a practical standpoint, the effort must focus on the integration of nanothermites and their derivatives in pyrotechnic systems. Toxicological concerns are expected to become increasingly important over the next decade.
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