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Nonlinear Ptychographic coherent diffractive imaging
No full textPtychographic Coherent Diffractive Imaging (PCDI) is
a significant advance in imaging allowing the measurement of the full electric field at a sample without use of any imaging optics. So far it has been confined solely to imaging of linear optical responses. In this paper we show that because of the coherence-preserving nature of nonlinear optical interactions, PCDI can be generalised to nonlinear optical imaging. We demonstrate second harmonic generation PCDI, directly revealing phase information about the nonlinear coefficients, and showing the general applicability of PCDI to nonlinear interactions.
Data supports the paper "Odstrcil, Michal, Baksh, Peter, Gawith, Corin, Vrcelj, Ranko, Frey, Jeremy and Brocklesby, William (2016) Nonlinear ptychographic coherent diffractive imaging. Optics Express"</span
Dataset for Metal-Organic Fireworks! MOFs as Structural Scaffolds for Pyrotechnic Materials
No full textA new approach to formulating pyrotechnic materials is presented whereby constituent ingredients are bound together in a solid-state lattice in the form of a Metal-Organic Framework. This reduces the batch inconsistencies arising from the traditional approach of combining powders by ensuring the key ingredients are ‘mixed’ in stoichiometric quantities and are in intimate contact. Further benefits for the application of these types of material are increased safety levels as well as simpler logistics, storage and manufacture. A systematic series of new frameworks comprising fuel and oxidiser agents (group 1 and 2 metal nodes and terephthalic acid derivatives as linkers) has been synthesised and structurally characterised. These new materials have been assessed for pyrotechnic effect by calorimetry and burn tests. Results indicate that these materials exhibit the desired properties of a pyrotechnic mate-rial and that the effect can be correlated to the di-mensionality of the structure.</span
Metal-Organic Fireworks! MOFs as integrated structural scaffolds for pyrotechnic materials
Get PDFA new approach to formulating pyrotechnic materials is presented whereby constituent ingredients are bound together in a solid-state lattice in the form of a coordination polymer. This reduces the batch inconsistencies arising from the traditional approach of combining powders by ensuring the key ingredients are ‘mixed’ in stoichiometric quantities and are in intimate contact. Further benefits for the application of these types of material are increased safety levels as well as simpler logistics, storage and manufacture. A systematic series of new frameworks comprising fuel and oxidiser agents (group 1 and 2 metal nodes and terephthalic acid derivatives as linkers) has been synthesised and structurally characterised. These new materials have been assessed for pyrotechnic effect by calorimetry and burn tests. Results indicate that these materials exhibit the desired properties of a pyrotechnic material and that the effect can be correlated to the dimensionality of the structure.A new approach to formulating pyrotechnic materials is proposed whereby constituent ingredients are bound together in a solid-state lattice. A series of coordination polymers comprising fuel and oxidiser agents exhibits the desired properties of a pyrotechnic material and this effect is correlated to the dimensionality of the structure
Polymorphism in 2-4-6 trinitrotoluene
No full textTwo crystal structures of 2-4-6 trinitrotoluene (TNT) are given, the monoclinic form (a(0) = 1.49113 (1) nm, b(0) = 0.60340 (1) nm, c(0) = 2.08815(3) nm, beta = 110.365 (1)degrees, V = 1.76137 (4) nm(3), space group = P2(1)/a, T = 100 K) and the orthorhombic form (a(0) = 1.4910 (2) nm, b(0) = 0.6031 (2) nm, c(0) = 1.9680 (4) nm, V = 1.7706 (7) nm(3), space group = Pca2(1), T = 123 K). Of these two forms, the most stable is the monoclinic and the less stable is the orthorhombic form. These two polymorphs are shown to be orientational, rather than configurational in character. Due to their restricted molecular motifs, no strong hydrogen bonding exists and the crystalline form is dominated by van der Waals type forces. The two structures are shown to be closely related and an analysis of the two structures shows that they are effectively large scale polytypes. Calorimetric studies show that the two polymorphs are monotropic and that the enthalpy of transformation is very low, concurring with the similarity shown by the diffraction data and calculated lattice energies. The thermal expansion coefficients are defined, and it is shown that both polymorphs have similar thermal expansions
Nonlinear ptychographic coherent diffractive imaging
Get PDFPtychographic Coherent Diffractive Imaging (PCDI) is a significant advance in imaging allowing the measurement of the full electric field at a sample without use of any imaging optics. So far it has been confined solely to imaging of linear optical responses. In this paper we show that because of the coherence-preserving nature of nonlinear optical interactions, PCDI can be generalised to nonlinear optical imaging. We demonstrate second harmonic generation PCDI, directly revealing phase information about the nonlinear coefficients, and showing the general applicability of PCDI to nonlinear interactions
Material Chemistry Control for the Additive Manufacture of Composite Propellants
Get PDF© Cranfield University 2022. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner.This thesis has sought to aid the additive manufacture of propellants using a
novel dry powder printing system developed at Cranfield. The energetic
performance and hazard safety of crystalline energetic materials is intrinsically
linked to crystal properties such as size, morphology, and crystalline phase. By
optimisation of cooling, antisolvent, sonocrystallisation, spray drying and
microencapsulation, the properties of cyclotrimethylenetrinitramine (RDX) and
ammonium perchlorate (AP) have been engineered towards better performance
within our printing system. Crystallisation of AP from solution in water has been assessed as a means of
producing particles with a controllable particle size and morphology. Slow
cooling processes (−7.5 °C hr-1
) failed to produce material suited for use in
propellant formulations. However, by significantly increasing the nucleation rate
using rapid cooling crystallisation processes (~ −5 °C min-1
) the size of
generated crystals was greatly reduced, with a d50 range of 79.1 - 152.3 µm,
compared to ~ 500 – 2000 µm. The application of ultrasonic radiation via a
horn to the rapid cooling crystallisation gave promising results – leading to
particle size reduction (d50 range: 33.5 – 43.4 µm) and a reduced frequency of
secondary nucleation. Moreover, the average particle size distribution width
was reduced from 245 µm to 75 µm by the application of sonication. Flow
character, as assessed by angle of repose measurements, was good for these
sonicated materials (31.0° to 34.1°). Spray drying and micro encapsulation was assessed as a means of RDX
particle size reduction. Initial studies using paracetamol as an inert simulant
demonstrated that modifications to spray drying process parameters (flow,
atomisation pressure, nozzle diameter and feed concentration) produced
measurable changes in particle size and size distribution. However, attempts to
rationalise these effects using a multifactorial design of experiment were
inhibited with the significant errors retrieved from the model. Attempts to
understand how particle properties impact the flow character of a powder led to
the observation that increased particle size gave decreased angle of repose. However, the magnitude of change was negligible when compared to the effect
of reformulation in the presence of known glidant nanomaterials.
Microencapsulation of RDX with cellulose acetate butyrate (CAB) was
conducted at a range of operating temperatures between 55 and 100 °C. Both
particle morphology and impact Figure of insensitiveness were demonstrably
affected by drying temperature, and both were minimised by the use of lower
drying temperatures (d50 = 2.60 µm, FoI = 102.0). FoI values for RDX/CAB
microparticles correlated negatively with drying temperature, suggesting that the
strain imparted by this rapid crystallisation process may be retained in the
material thereby acting to influence its hazardous nature.
Crystallisation of RDX by antisolvent precipitation and spray drying was
assessed with the inclusion of five different tailor-made additives (TMAs). Of
the assessed TMAs, 2,4-dimethyl-1nitrobenzene and 1,2-diemthyl-3-
nitrobenzene were noteworthy for causing significant particle size reduction of
antisolvent precipitated RDX. Crystal size enlargement and aspect ratio
elongation was most pronounced when 1,3,5-triazine-2,4-diamine impurity was
present. A novel application of the Scherrer equation was employed, to study
the effect of TMA inclusion on the constituent crystallites within spray dried
microparticles. The investigation revealed reduced coherence length of the
(002) plane and extension of the (210) plane when RDX was spray dried in the
presence of TMAs.PH
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Additively manufactured (3DP) thermite structures vs conventionally manufactured equivalents
Get PDFResearch into additive manufacturing (AM) has been steadily expanding over the past five decades. Where once only polymeric materials could be reliably printed, AM has been adapted to print with a range of materials such as biological, metallic, ceramic and even foodstuffs. The advantages of manufacturing in an additive manner include; a) a layer-by-layer approach allows the creation of architecturally complex structures, b) a reduction in weight, c) lessening of waste and d) the ability to create parts that that are otherwise difficult or too costly to produce.
Pyrotechnic materials, including thermites, are used in a wide range of commercial and defence applications. However, hazards present during manufacturing and storage have resulted in major accidents around the world, with subsequent loss of life and in some cases loss of public infrastructure. AM, using a dry powder printing technique means that parts can be manufactured on demand, reducing the need for storage of large volumes of fully formed products or mixes, thus increasing the safety over lifetime of a product.
The performance of pyrotechnics materials is dependent on a number of properties, including chemical composition, thermodynamic properties and physical form. In combination with composition, architecture could be utilised to understand and control these properties. A bespoke printer capable of additively manufacturing pyrotechnic materials has been constructed with the aim to explore this research area.
In this presentation, we compare the burn rates of AM thermites and compare them to conventionally fabricated compositions and discuss the effects of the print parameters and confinement. We conclude with the results from the burning of AM thermite structures and compare their performance with conventionally prepared equivalent thermite examples.45th International Pyrotechnics Society Seminar (2022 IPS Seminar
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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