377 research outputs found
Ba(Mg1/3Ta2/3)O3 Thermal Barrier Coating Deposited by Liquid Precursor Plasma Spray: Phases and Microstructure Control
This study explores a new route to deposit complex oxide thermal barrier coatings (TBCs) Ba(Mg1/3Ta2/3)O3 (BMT) from liquid precursors, using a radio frequency (RF) induction plasma spray (IPS), which differs from the most frequently used technique, direct current (DC) air plasma spray (APS).
Among the known oxide materials, BMT has the highest melting point (2900-3100 °C). Accordingly, it is envisioned as one of the most promising TBC candidate materials for the aeronautic field. Due to the limits imposed by BMT feedstock decomposition mainly caused by Mg evaporation during the APS process, and to the low service lifespan of dense lamellar coatings, liquid precursors were chosen as feedstock in this work. Indeed, they can attenuate feedstock decomposition by adding an excess of Mg into the initial precursor mixture. Furthermore, liquid precursors, normally prepared by solution and/or nanoscale solid particles suspensions, facilitate the formation of columnar structures. Therefore, the process adopted in this work is named hybrid suspension plasma spray (SPS)/ solution precursor plasma spray (SPPS). X-ray photoelectron spectroscopy (XPS) was used to evaluate quantitatively the element evaporation during plasma spraying. Thermogravimetric / differential thermal analysis (TG/DTA) was applied to investigate the BMT formation. The phase and microstructure were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Plasma diagnostic was performed by optical emission spectroscopy (OES).
This project first proved that complex oxide synthesis and coating deposition can occur simultaneously in the Hybrid SPS/SPPS or SPPS processes. The formation mechanism and the correlation between the main BMT phase and four other secondary phases (BaTa2O6, Ba3Ta5O15, Ba4Ta2O9, Mg4Ta2O9) were discussed clearly. The key parameters (plasma power, spraying distance, substrate pre-heating, precursor chemistry and particle size of suspended particles), were explored in order to optimize phase structure and deposition rate of as-sprayed coatings.
In addition, this research demonstrated the feasibility of applying RF SPPS to deposit BMT coating with an adjustable microstructure. Lamellar, columnar and dense vertically-cracked structures of BMT can be tuned by adjusting the spraying parameters. This result represents an opportunity to apply RF plasma spray in the TBCs field, in addition to that of DC plasma spray and EB-PVD. Short spray distance and bimodal atomized droplet size distribution were identified as key prerequisites for column formation. Parameters such as substrate roughness, precursor concentration and feed rate were studied with regards to the columnar morphology.
A distinctive TBC microstructure, namely vertical grains, was presented in the as-sprayed BMT coatings. The novel material and microstructure differentiate themselves from any commonly-seen TBCs. The phase structure of vertical grains was analyzed with the assistance of elemental mapping and BaO-MgO-Ta2O5 ternary phase diagrams. The formation mechanism of vertical grains was discussed in terms of temperature gradient. Finally, based on the microstructure optimized in this work and other physical property of thermal expansion coefficient, BMT presents the potential for acting as a thermal protection coating on niobium alloy in the foreseeable future.Cette étude explore une nouvelle voie pour déposer des revêtements d’oxydes complexes pour les barrières thermiques (TBC) Ba(Mg1/3Ta2/3)O3 (BMT) à partir de précurseurs liquides. Les dépôts sont faits en utilisant la projection par plasma radiofréquence (RF) à couplage inductif, qui diffère de la technique la plus fréquemment utilisée dans le domaine, à savoir la projection plasma à air (APS) en courant continu (DC).
Parmi les matériaux oxydes connus, le BMT a le point de fusion le plus élevé (2900-3100 °C). En conséquence, il est considéré comme l'un des matériaux candidats TBC les plus prometteurs pour le domaine aéronautique. En raison des limites imposées par la décomposition des matières premières du BMT, principalement causée par l'évaporation du Mg pendant le processus APS, et à la faible durée de vie des revêtements lamellaires denses, des précurseurs liquides ont été choisis comme matière première dans ce travail. En effet, ils peuvent atténuer la décomposition des matières premières en ajoutant un excès de Mg dans le mélange initial de précurseurs. En outre, les précurseurs liquides, normalement préparés par des solutions et/ou des suspensions de particules solides à l’échelle nanométrique, facilitent la formation d'une structure colonnaire. Par conséquent, le procédé adopté dans ce travail est nommé projection plasma hybride de suspension (SPS) / précurseur liquide (SPPS). La spectroscopie photoélectronique X (XPS) a été utilisée pour évaluer quantitativement l'évaporation des éléments pendant la projection par plasma. L’analyse thermique thermogravimétrique / différentielle (TG / DTA) a été réalisée pour étudier la formation de BMT. La phase et la microstructure ont été analysées par diffraction des rayons X (XRD) et par microscopie électronique à balayage (SEM), respectivement. Le diagnostic du plasma a été effectué par spectroscopie d'émission optique (OES).
Ce projet a d'abord prouvé que la synthèse d'oxydes complexes et le dépôt de revêtement peuvent se produire simultanément dans les processus hybrides SPS/SPPS ou SPPS. Le mécanisme de formation et la corrélation entre la phase principale du BMT et quatre autres phases secondaires (BaTa2O6, Ba3Ta5O15, Ba4Ta2O9, Mg4Ta2O9) ont été clairement discutés. Les paramètres clés (puissance du plasma, distance de projection, préchauffage du substrat, chimie des précurseurs et taille des particules en suspension) ont été étudiés afin d'optimiser la structure des phases et le taux de dépôt des revêtements projetés.
En outre, cette recherche a démontré la faisabilité de l’application de RF SPPS pour déposer un revêtement de BMT ayant une microstructure contrôlable. Les structures lamellaires, colonnaires et à fissures verticales denses du BMT peuvent toutes les trois être obtenues en ajustant les paramètres de projection. Ce résultat représente une opportunité d'appliquer la projection plasma RF dans le domaine des TBC, en plus de celle de la projection plasma DC et du dépôt physique en phase vapeur par faisceau d'électrons (EB-PVD). Une courte distance de projection et une distribution bimodale de la taille des gouttelettes atomisées ont été identifiées comme des conditions préalables clés à la formation de colonnes. Des paramètres tels que la rugosité du substrat, la concentration en précurseur et le taux d'alimentation ont été étudiés pour connaître leur influence sur la morphologie en colonne.
Une microstructure TBC distinctive, à savoir avec des grains verticaux, a été trouvée dans les revêtements BMT projetés. Le nouveau matériau et la microstructure se distinguent de tous les autres TBC courants. La structure de phase des grains verticaux a été analysée à l'aide d'une cartographie élémentaire et de diagrammes de phases ternaires BaO-MgO-Ta2O5. Le mécanisme de formation des grains verticaux a été discuté en termes de gradient de température. Enfin, sur la base de la microstructure optimisée dans ce travail et d'autres propriétés physiques du coefficient de dilatation thermique, le BMT présente le potentiel d'agir comme un revêtement de protection thermique sur un alliage de niobium dans un avenir prévisible
Espumas e cerâmicos densos à base de cordierite: preparação, caracterização e modelação
Mestrado em Ciência e Engenharia dos MateriaisOs materiais cerâmicos à base de cordierite são normalmente usados como
materiais refractários devido às propriedades que possuem, tais como,
excelente expansão térmica e elevada resistência ao choque térmico. Os pós
precursores consistem numa composição estequeométrica de minerais à base
de alumina, talco, α-quartzo, K-feldspato, caolinite e mulite, bem como uma
pequena quantidade de calcite, cristobalite e fases vítreas derivadas da
moloquite, obtidas pela calcinação da caolinite a elevadas temperaturas
(1550ºC).
Os corpos em verde consolidados por enchimento por barbotina foram
sinterizados ao ar a diferentes temperaturas: 1050, 1150, 1250, 1350, 1425 e
1500°C. Os resultados obtidos por difracção de Raios-X mostraram que a
cristalização ocorre entre 1250 e 1350ºC e que a composição inclui não só
cordierite mas também mulite, alumina e quartzo residual. Aumentando a
temperatura de sinterização para 1500ºC, a única fase cristalina detectada é a
mulite, juntamente com uma elevada fracção de porosidade envolta por uma
abundante fase vítrea.
Além dos efeitos originados pela temperatura, a sinterização é também
dependente do tempo. Por este motivo, o tratamento térmico foi efectuado ao
fim de 2, 4 e 8 h de patamar de modo a relacionar as composições obtidas
com o tempo de sinterização. As composições obtidas à base de cordieritemulite-
alumina apresentam baixo coeficiente de expansão térmico 2~4x10-6/K
e resistência à flexão relativamente elevada, 90~120 MPa. As amostras
sinterizadas a 1250ºC durante 2 e 4 h apresentam os valores mais elevados de
resistência ao choque térmico (ΔT~350-400 K).
Além destas propriedades, os materiais à base de cordierite também
apresentam baixa constante dieléctrica (entre 5 e 10) e um baixo factor de
perda dieléctrica, o que faz deles materiais com forte potencial para aplicações
em circuitos integrados como substratos dieléctricos. A constante dieléctrica
em função da temperatura foi medida desde a temperatura ambiente até
600ºC, tendo-se verificado estabilidade das propriedades dieléctricas a 1 MHz
em toda a gama de temperaturas testada.
As propriedades reológicas das suspensões à base de cordierite foram
optimizadas de forma a obter uma boa impregnação do polímero. As
propriedades mecânicas das espumas cerâmicas obtidas pelo método de
replicação da espuma polimérica foram caracterizadas com base nas
propriedades dos cerâmicos densos. O módulo de Young foi determinado pelo
método de excitação por impulso. A teoria micro-mecânica para materiais
heterogéneos conhecida como método de “Mori-Tanaka” foi aplicada para
estimar o módulo efectivo das espumas cerâmicas. Dos resultados obtidos
verifica-se um desfasamento entre os valores experimentais (1~2 GPa) e os
teóricos (6~7 GPa). A tomografia computadorizada por Rais-X foi usada para
estudar a estrutura tridimensional (3D) das espumas cerâmicas por análise de
elementos finitos (FEA). As propriedades elásticas foram estudadas pelo
cálculo da força de reacção na deformação elástica. Embora a estrutura
tridimensional calculada das espumas cerâmicas represente apenas uma
pequena fracção da estrutura, os resultados mostram que a correlação entre
eles é fortemente melhorada pelo método de Mori-Tanak. A razão apontada
para o desfasamento é a existência de uma estrutura interna oca, que não é
tida em conta no modelo utilizado. Por outro lado, o método CT mostra que a
estrutura porosa e a diferença no microestrutura poderá também ser simulada.
O resultado da análise de elementos finitos mostrou que as espumas
cerâmicas são muito quebradiças, o que é consistente com a observação
experimental obtida nos testes de compressão.Cordierite ceramics have excellent thermal expansion and thermal shock
resistance for applications such as refractory materials. The precursor powder
consisted of a non-stoichiometric composition of minerals containing corundum,
talc, α-quartz, K-feldspar, kaolinite and mullite as well as small amount of
calcite, Cristobalite and glass phases probably derived from molochite,
produced by calcining kaolinite at high temperature (1550 ºC). The green
consolidates were sintered in air at 1050, 1150, 1250, 1350, 1425 and 1500°C.
It was discovered by XRD that cordierite crystallization takes place between
1250 oC and 1350 oC while the composition includes not only cordierite but also
mullite and alumina and residual quartz. At 1425oC, the ceramics consisted of
cordierite and mullite. With further increasing the sintering temperature to 1500
oC mullite was the single crystalline phase detected, together with a high
porosity fraction embedded in an abundant glassy phase. Besides the
temperature effects, sintering was also time-dependent, therefore heat
treatment was conducted for 2, 4 and 8 h to study the sintering time–
composition relationships. The cordierite-mullite-alumina heterogeneous
ceramics were obtained with low thermal expansion coefficient of 2~4x10-6/K
and relatively high flexural strength of 90~120 MPa. Thermal shock resistance
measurements demonstrated that the samples sintered at 1250 oC for 2 h and
4 h exhibited the highest thermal shock resistance values (ΔT~350-400 K).
Cordierite ceramics also exhibited very low dielectric constant (between 5 and
10) and low dielectric loss factor, showing a good potential for low dielectric
substrate applications in integrated circuits. The dielectric constant as function
of temperature was measured from RT to 600oC, demonstrating to have very
stable dielectric properties at 1 MHz across the entire temperature range.
The cordierite slurries were prepared with optimized rheological properties and
impregnation conditions to coat the polymer struts by dip casting. The
mechanical properties of ceramics foams fabricated by polymer replica method
were characterised on basis of properties of bulk ceramics. The foam’s
effective Young’s modulus was determined by Impulse excitation method.
Micro-mechanical theory for heterogeneous material known as “Mori-Tanaka”
method was applied to model the effective modulus of ceramics foam. The
results showed that the agreement was not good between experimental (1~2
GPa) and modelling (6~7 GPa) data. In the meantime, Computed X-ray
tomography was applied to study the actual 3D structure of ceramic foams for
Finite Element Analysis (FEA). Elastic properties were studied by calculating
the reaction force in elastic deformation. Although the calculated 3D structure
of the ceramic foams represents only small fraction of the structure, the results
showed that the agreement has greatly improved over Mori-Tanaka method.
The reason of disagreement from the former method is the existence of internal
hollow structure in ceramics struts, which is not taken into account in the
model. On the other hand, CT method revealed the hollowed structure and the
influence of such microstructure could be simulated. The FEA also showed that
the ceramic foams are very brittle, which is consistent with the experimental
observation under compression tests
Spark-Plasma Sintering and Related Field-Assisted Powder Consolidation Technologies
Electromagnetic field-assisted sintering techniques have increasingly attracted attention of scientists and technologists. Spark-plasma sintering (SPS) and other field-assisted powder consolidation approaches provide remarkable capabilities to the processing of materials into configurations previously unattainable. Of particular significance is the possibility of using very fast heating rates, which, coupled with the field-assisted mass transport, stand behind the purported ability to achieve high densities during consolidation and to maintain the nanostructure of consolidated materials via these techniques. Potentially, SPS and related technologies have many significant advantages over the conventional powder processing methods, including the lower process temperature, the shorter holding time, dramatically improved properties of sintered products, low manufacturing costs, and environmental friendliness
Novel phosphate-based cements for clinical applications
This Thesis aims at the development of two novel families of inorganic phosphate cements with suitable characteristics for clinical applications in hard tissue regeneration or replacement. It is organized in two distinct parts.
The first part focuses at the development of silicon-doped a-tricalcium phosphate and the subsequent preparation of a silicon-doped calcium phosphate cement for bone regeneration applications. For this purpose, silicon-doped a-tricalcium phosphate was synthesized by sintering a calcium-deficient hydroxyapatite at 1250ºC with different amounts of silicon oxide. The high temperature polymorph a-tricalcium phosphate was stabilized by the presence of silicon, which inhibited reversion of the b-a transformation, whereas in the Si-free a-tricalcium phosphate completely reverted to the b-polymorph. It was observed that the presence of Si did not alter the b-a transformation temperature. Both the Si-doped a-tricalcium phosphate and its Si-free counterpart were used as reactants in the formulation of calcium phosphate cements. While Si-doped a-tricalcium phosphate showed faster hydrolysis to calcium deficient hydroxyapatite, the composition, morphology and mechanical properties of both cements were similar upon completion of the reaction. When the samples were immersed in simulated body fluid, the Si-doped cement exhibited a faster deposition of an apatite layer on its surface than its Si-free counterpart, suggesting an enhanced bioactivity of the doped-cement. An in vitro cell culture study, in which osteoblast-like cells were exposed to a medium modified by the materials, showed a delay in cell proliferation and a stimulation of cell differentiation, the differentiation being more marked for the Si-containing cement. These results were attributed to the Ca depletion from the medium by both cements and to the continuous Si release detected for the Si-containing cement.
The second part of this Thesis is focused on the development of a new family of inorganic phosphate-based cements for biomedical applications, namely magnesium phosphate cements. The magnesium phosphate cements have been extensively used in civil engineering due to their fast setting, early strength acquisition and adhesive properties, properties that can be also of use for biomedical applications. However, there are some aspects that should be improved before they can be used in the human body, namely their high exothermic setting reaction and the release of potentially harmful ammonium ions. Therefore, a new family of magnesium phosphate cements was explored as candidate biomaterials for hard tissue applications. These cements were prepared by mixing magnesium oxide with either sodium dihydrogen phosphate, ammonium dihydrogen phosphate or an equimolar mixture of both. The exothermia and the setting kinetics of the new cement formulations were tailored. The ammonium-containing magnesium phosphate cements resulted in struvite as the major reaction product, whereas the magnesium phosphate cement prepared with sodium dihydrogen phosphate resulted in an amorphous product. The magnesium phosphate cements studied showed an early compressive strength substantially higher than that of conventional apatitic calcium phosphate cements. Moreover, they showed antimicrobial properties against bacteria present in dental infections, which were attributed to the synergistic effect of a high osmolarity and high pH of the cement extracts. These properties make magnesium phosphate cements good candidates for endodontic applications. It is with this latter point in mind that some of the most relevant physico-chemical properties were further optimized and characterized. Particularly, their radiopacity was enhanced by the addition of bismuth oxide. The sealing efficiency of the magnesium phosphate cements and their adhesion to dentin were shown to be comparable or even higher than those presented by other inorganic cements used for endodontic treatments.Aquesta Tesi té com a objectiu el desenvolupament de dues noves famílies de ciments
inorgànics de base fosfat amb propietats adequades per a aplicacions clíniques en regeneració o
substitució de teixits durs. La Tesi està organitzada en dues parts.
La primera part està centrada en el desenvolupament de fosfat tricàlcic a dopat amb silici i
la subseqüent preparació de ciments de fosfat de calci dopats amb silici. Per a aquest objectiu, es
va obtenir fosfat tricàlcic a dopat amb silici mitjançant la sinterització d’una hidroxiapatita
deficient en calci amb diferents quantitats d’òxid de silici a 1250°C. La presència de silici va
estabilitzar el polimorf d’alta temperatura (fosfat tricàlcic a), inhibint-se la reversió de la
transformació b-a, mentre que el fosfat tricàlcic a sense silici va revertir completament a polimorf
b. La presència de silici no va alterar la temperatura de la transformació b-a. Tant el fosfat tricàlcic
a dopat amb silici com el seu homòleg sense silici van ser utilitzats com a reactius en la formulació
de ciments de fosfat de calci. Si bé el fosfat tricàlcic a dopat amb silici va mostrar en les fases
inicials una hidròlisi més ràpida a hidroxiapatita deficient en calci, un cop completada la reacció, la
composició, morfologia i propietats mecàniques d’ambdós ciments van ser similars. L’estudi de
bioactivitat mitjançant la immersió de les mostres en fluid corporal simulat va donar com a resultat
la formació d’una capa d’apatita a la superfície del ciment dopat amb silici, més ràpida que al seu
homòleg sense silici, fet que va suggerir una bioactivitat millorada del ciment dopat. L’estudi in
vitro, en el qual cèl·lules osteoblàstiques es van exposar a un medi de cultiu que havia estat
prèviament en contacte amb els ciments estudiats, va mostrar un retràs en la proliferació cel·lular i
un estímul de la diferenciació cel·lular, aquest últim més marcat pel ciment que contenia silici.
Aquests resultats es van atribuir a la reducció de calci en els medis en els quals estaven introduïts
els ciments i a l’alliberament continu d’ions silici per part del ciment que en contenia.Postprint (published version
Sintering
This book is addressed to a large and multidisciplinary audience of researchers and students dealing with or interested in sintering. Though commonly known as a method for production of objects from fines or powders, sintering is a very complex physicochemical phenomenon. It is complex because it involves a number of phenomena exhibiting themselves in various heterogeneous material systems, in a wide temperature range, and in different physical states. It is multidisciplinary research area because understanding of sintering requires a broad knowledge - from solid state physics and fluid dynamics to thermodynamics and kinetics of chemical reactions. Finally, sintering is not only a phenomenon. As a material processing method, sintering embraces the wide group of technologies used to obtain such different products as for example iron ore agglomerate and luminescent powders. As a matter of fact, this publication is a rare opportunity to connect the researchers involved in different domains of sintering in a single book
An In Vitro Investigation of a Novel, Two-Piece Zirconia Dental Implant System
Implant treatment is currently overriding other prosthetic solutions especially in the case of replacing anterior teeth in the aesthetic zone. Zirconia ceramics exhibit promising aesthetic, periointegration and antibacterial properties that may overcome critical drawbacks associated with titanium based dental implants. They also possess distinctive mechanical properties due to the unique transformation toughening mechanism. However, the effects of low-temperature degradation (LTD) or ageing on the durability of the material is of a major concern. Additionally, the currently available one-piece and two-piece zirconia dental implant designs exhibit sub-standard performance.
This study aimed to investigate ageing, mechanical properties and biofunctional characteristics of a new implant system with a novel biomechanical design. The proposed design utilises a relatively low-strength glass fibre composite abutment bonded with resin cement to an injection-moulded, soft tissue level, acid-etched zirconia implant.
Hydrothermal treatment was used to simulate in vivo ageing. A battery of complimentary crystallographic and imaging studies was used to characterise hydrothermally- and stress-induced phase transformation. Additionally, the effect of ageing on basic mechanical properties of standard samples was investigated at the macro-, micro- and nano-scales. Dynamic fatigue was performed in order to determine durability and reliability of various components and interfaces of the design under simulated clinical conditions. The acid-etched zirconia surface (MDS) was compared to a high-performance, mechanically and chemically modified titanium surface in terms of; surface topography, biocompatibility and cell biofunctional response.
The results of this study indicated that hydrothermal ageing resulted in phase transformation that was localised to the surface of the material without any involvement of the bulk. No evidence of extensive cracking was detected as a result of the used ageing conditions. The aged samples exhibited static mechanical properties that were not significantly different from the control group apart from marginal decreases in surface hardness. The implant samples restored with two different crown materials did not exhibit any premature failures. The engineered weak connection seemed to favour retrievable failures especially when low strength crown material was used to restore the implants. The studied MDS zirconia surface exhibited moderate surface roughness and high biocompatibility when tested with human osteoblast-like cells and human gingival fibroblasts. Cell attachment and bone formation capacity of cells were similar or marginally higher in cells cultured on MDS surface when compared to titanium (SLActive-like) counterpart.
Within the limitations of this study, it can be concluded that the studied zirconia material was not drastically affected by hydrothermal ageing and thereby, in vivo LTD may be not of a concern whilst using such material. The current implant design may withstand long-term functional forces in the anterior region of the oral cavity. The MDS surface may reduce the time required for bone and soft tissue healing which is essential for clinical cases require immediate provisionalisation and/or early loading. Soft tissue remodelling may be of a less concern owing to the high soft tissue attachment (periointegration) capacity of the studied MDS zirconia surface
Eleventh European Powder Diffraction Conference. Warsaw, September 19-22, 2008
Zeitschrift für Kristallographie. Supplement Volume 30 presents the complete Proceedings of all contributions to the XI European Powder Diffraction Conference in Warsaw 2008: Method Development and Application,Instrumental, Software Development, Materials. Supplement Series of Zeitschrift für Kristallographie publishes Proceedings and Abstracts of international conferences on the interdisciplinary field of crystallography
Master of Science
thesisSix metal boride compounds (AlB2, MgB2, Al0.5Mg0.5B2, AlB12, AlMgB14 and SiB6) with particle sizes between 10-20 m were synthesized for insensitive energetic fuel additives from stoichiometric physical mixtures of elemental powders by high temperature solid state reaction. B4C was also investigated as a lower cost source of boron in AlB2 synthesis and showed promise as a boron substitute. Thermal analysis confirmed that the formation of boride compounds from physical mixtures decreased sensitivity to low temperature oxidation over the aluminum standard. Both Al+2B and AlB2 were much less sensitive to moisture degradation than aluminum in high humidity (10-100% relative humidity) and high temperature (20-80°C) environments. AlB2 was determined to be safe to store for extended periods of time in cool, dry environments. Impact, friction and shock sensitivity testing indicated that AlB2 and MgB2 were less sensitive than aluminum. The activation energies for the oxidation of Al, B, Al+2B and AlB2 were determined through an isothermal, isoconversional method in N2-20%O2 and O2 at one atmosphere. An activation energy of 413 ± 20 kJ/mol was calculated for AlB2 in O2. The incorporation of magnesium and/or aluminum with boron increased its oxidation rate and overall conversion through the formation of metal-borate crystals (2Al2O3·B2O3 and 3MgO·B2O3) which removed liquid B2O3 from the surface of oxidizing particles. Aluminum also increased the oxidation efficiency of B4C by a similar mechanism. AlB2, MgB2 and Al0.5Mg0.5B2 oxidized to greater than 85% of their theoretical values while exhibiting decreased sensitivity to low temperature oxidation, making them top candidates for further energetic testing. Cylinder expansion testing of AlMgB14 showed little reaction of the boride material within seven volume expansions, corresponding to poor energetic performance. Detonation calorimetry of AlB2 and Al + 2B using proprietary energetic mixtures in an argon atmosphere showed that AlB2 reacted almost completely while Al + 2B did not. Future work should focus on testing the diboride materials and synthesizing and testing similar materials made from B4C
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