Thiol-capped CdTe quantum dots hosted in saponites

A novel synthesis of β-CD@SA@Ag composite hydrogel microspheres with high catalytic activity and environmental adaptability

The formation of a composite material during combustion of a two-layer sample in a centrifugal device was studied by mathematical modeling. The liquid combustion products of the upper layer flow into the lower porous layer under the action of the centrifugal force and initiate its combustion to form a composite material. The critical conditions for the passage of the combustion wave from the upper to the lower layer of the sample are determined depending on the gravitational overload and initial porosity. Dependences of the burning velocity and the impregnation depth of the lower layer on its porosity and overload are obtained.

: The thrust of the work completed is an investigation on the effect of an electric field on the synthesis and densification of complex materials. Experimental investigations were made on the field effect in the synthesis of: (a) solid solution precursors for nanoscale modulated composites, (b) a high temperature ceramic with relatively high fracture toughness, (c) macro-alloyed high temperature silicides, and (d) hard material of boride composites with highly oriented precipitates. Modeling studies on the effect of the electric field (current) on synthesis reactions were also made. In addition, an important new direction in the completed work was the investigation of the simultaneous synthesis and densification of nanometric materials. The latter work has led to the issuance of a U.S. Patent and a pending application for an International Patent. The work was facilitated by the use of the Spark Plasma Synthesis (SPS) apparatus, the only one of its kind in the U.S..

Casted composite materials have found certain application in mechanical engineering. Their advantages are lower cost due to the use of casting technology (solid-liquid synthesis), absence of any restriction on the shape and weight of parts. It is known that the transition zone between the matrix alloy and reinforcing phase plays an important role on the level of mechanical properties of cast composites. So, the aim of the study is investigations of transition zone formation during the infiltration of matrix alloy into the frame formed by the reinforcing phase. Copper based alloy was used as a matrix alloy and cast-iron granules were used as a reinforcing phase. Cast composite materials have been exposed for different time during the synthesis. Specimens were studied using electron microscopy. Results on the concentration distribution of main elements (Si, Fe, Cu) in a transition zone are presented. It is shown that the formation of transition zone starts during the infiltration process with further its growth during the exposition at the synthesis temperature. It is established that the formation of the transition zone takes place not only due to elements diffusion but as well due to the dissolution of granules of reinforcing phase. Experiments carried out allow establishing some peculiarities of the transition zone formation. To achieve required level of mechanical properties it is necessary to control the melt temperature and duration of the synthesis of cast composite materials.

Lightweight and high strength composite materials are vital for unmanned aerial vehicles (UAVs) and aerospace technologies with desired characteristics. Carbon composite materials exhibit extraordinary properties for UAVs and aerospace applications. This study aimed to discover the best-prepared composition of composites material having epoxy LY-5052 and carbon fibres laminate for UAVs. Besides, to develop a low cost with high specific strength composite material for aerospace application to replace metallic alloys. In this work, the vacuum bag technique is used to prepare rectangular strips of three different ratios of carbon fibre/epoxy laminates [(40:60), (50:50) and (60:40)] to obtain the best composite in terms of properties. The thermo-mechanical and viscoelastic behaviour of composite materials were evaluated using differential scanning calorimetry (DSC), universal testing machine (UTM) and dynamic mechanical analysis (DMA). The tensile strength of epoxy LY5052 composites with 60 wt% has enhanced to 986%, and glass transition temperature (Tg) was improved from 71oC to 110oC. Overall, 60 wt% carbon fibre exhibits better thermo-mechanical properties with lightweight, which may be a future composite material for aerospace, especially UAVs technologies.

A new approach to computer simulation of the synthesis of medical composite materials has been developed to study the determining factors for obtaining a promising class of scaffolds for personalized replacement of bone defects. This class of scaffolds is a dispersed-filled polymer with a biodegradable matrix and a gradient pore structure. Particles of calcium phosphate, magnesium, zinc, boron nitride and biodegradable fibers are considered as dispersed components. This provides antibacterial, medicinal and other properties.

A reactive hot-melt resin (polyurethane) was used to manufacture Guadua composites with a certain flexibility, high processing speed, good initial rigidity, and high temperature performance. These composites can support a moderate tensile stress, allow for large strains at low stresses, and have a low density and a working temperature range of -40 °C and 110 °C. During the flexural test, bamboo composites with reactive polyurethane matrix do not break or fail during the test. A polyurethane-based reactive hot-melt resin was characterized by tensile tests, Shore hardness tests, differential scanning calorimetry, and thermogravimetry. Besides, a composite material was made with Guadua fiber and polyester matrix, which had a greater strength in the test of tension and flexion, although it had a lower percentage of elongation than the composite material with reactive polyurethane. Guadua fiber can increase the strength by 266% of polyurethane matrix and 228% of polyester matrix.

In this study we evaluated the potential use of hazelnut shell powder in the production of a composite material. Polystyrene was used as a polymer matrix. This work presents the results of modifying hazelnut powder particles to create a polystyrene shell on their surfaces. Modification of the filler increased its contact angle wetted with water from θ=60.16±1.03° to θ=87.02±1.10°. Composite materials containing from 10 to 50 wt.% of modified hazelnut shell powder were prepared and studied. As a result of the experiments, it was found that the composites have optimal physical, mechanical, and operational properties at the following ratio: polystyrene 60-80 wt.%, modified hazelnut shell powder 20-40 wt.%. If the introduction of polystyrene was more than 90 wt.%, the flexural strength and Vickers hardness were quite low at the load of 200 g, and accordingly, the durability of such materials was not satisfactory. These samples are characterized by small percentages of hazelnut shells; therefore, the resulting material will be of pale, unsaturated color. The upper limit of the working temperature range for the composite lies between 265.0-376.0 °C, depending on the percentage of the hazelnut shell powder filling.

Synthesis and characterization of epoxy and natural fiber composite material

A unique bipolar pulse electrodeposition is developed to efficiently prepare composite electrode materials and the structural stability of NiCoS nanoflowers and PPy is noticeably enhanced by the symbiotic growth.

Synthesis and characteristic analysis of an inorganic composite phase change materials for medium-temperature thermal storage

Self-propagating high-temperature synthesis (SHS) was carried out in the Ni-Al-Ti-B system. The aim of the study was to obtain a composite material with ceramic and intermetallic frameworks and with a developed porous structure in the combustion mode in one process step from the «boron-titanium-large nickel-clad aluminum granules» powder system pressed by sequential batch compaction. The synthesis process featured by a stage nature where a highly exothermic reaction between titanium and boron formed a boride matrix with developed open porosity and acted as a «chemical furnace» to maintain the reaction in clad granules resulting in nickel aluminides. The aluminide melt impregnated the porous diboride matrix. The synthesis stages are reflected in the process thermograms. The final structure of the product features multi-scale porosity characterized by large round pores (~100÷160 μ m in diameter) with the location corresponding to the position of clad granules in the original powder system. Small (0.1-5.0 μ m) and some average-sized (up to 15 μ m) diboride matrix pores are filled with nickel aluminides. The resulting material has a composite structure in analogy with interpenetrating frameworks - ceramic (TiB 2 ) and aluminide (NiAl, Ni 3 Al). The diboride matrix is formed by randomly oriented small hexagonal crystals with a size of mainly ~0.2÷1.0 μm across. Diboride crystalline grains increase in size to 2-6 um in diameter and 0.5-2.0 μm in thickness near the macropores becoming strongly plate-shaped. The main size of intermetallic layers filling the pores between the diboride crystalline grains is ~0.2÷1.0 μm.

The review discusses aspects of the synthesis and application of new composite materials with molecular sieve properties, formed on the basis of metal–organic framework (MOF) structures and ionic liquids (ILs). Ways of creation, physicochemical characteristics, and problems of practical application of IL/MOF systems to selective adsorption and gas separation are considered.

Biomimetic strategies which utilise hydrogels have been targeted due to favourable hydrogel characteristics such as the presentation of a large surface area for crystal nucleation within a structured yet responsive scaffold. Chitosan hydrogels were prepared and mineralised using a combined method which involves alternate soaking of the films with precursor solutions, followed by treatment with saturated mineral solution. This method has been shown to be effective for the synthesis of calcium carbonate-chitosan composite materials with tensile strength comparable to nacre. The ratio of organic to inorganic is readily controlled through the presoaking solution concentrations. The ubiquity of this method is shown here with respect to switching out both the anion (CaHPO(4)) and the cation (BaSO(4)). Cation doping is also readily achieved allowing formation of Mg-rich CaCO(3). Poly(acrylic acid) added to (Mg,Ca)CO(3)-chitosan systems induces the formation of two polymorphs (vaterite and calcite) which coexist within the composite material. The mineralised scaffolds were analysed by SEM and powder XRD. The successful mineralisation of chitosan templates with various inorganic compounds shows that this combined approach is widely applicable as a biomimetic approach.

In-vitro investigation of graphene oxide reinforced bioactive glass ceramics composites