Dimensional changes during micropyretic synthesis (original) (raw)

Fabrication of High Aspect Ratio Porous Microfeatures Using Hot Compaction Technique

2008

High aspect ratio porous microfeatures are becoming more important in the modern industry. However, the fabrication of such features under a mass production environment remains a challenge when robustness, cost effectiveness, and high productivity requirements are required. In this study, the forming of such porous microfeatures using hot compaction was investigated. A hot compaction experimental setup was designed and fabricated that is capable of performing high temperature operation (700°C), quick heatup, and avoiding oxidation. 3D thermal simulation of the experimental setup was conducted to investigate the heat transfer performance and internal temperature distribution, which was then used as a reference for the experiment. Hot compaction experiments were carried out, and the effects of compression force and temperature on the quality in terms of powder consolidation strength and porosity were investigated. In addition, the achievable aspect ratio and taper angle were also discussed.

Applying micro-computed tomography for porosity analysis of polypropylene modified with microspheres

2021

Porosity of polypropylene samples was investigated by applying X-ray micro-computed tomography (micro-CT), which is getting more and more popular as a non-destructive method. Microspheres were applied as a blowing agent at three concentrations: 3%, 6% and 9% by weight. Tensile testing specimens were obtained by injection molding technology and its central, measuring part were examined by micro – CT. Results were compared to porosity calculated based on difference in porous and solid material density. Pore size distribution curves were discussed as well.

Fundamental Studies of Crystal Growth of Microporous Materials

Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include:

Synthesis and characterisation of porous polymer microneedles

Journal of Polymer Research, 2010

This paper presents a study on the synthesis of porous polymers with an application to microneedles. A range of Poly (ethylene glycol-co-methacrylic acid) polymers are synthesised using bulk polymerisation techniques to produce porous polymers with various strength and fluid transport characteristics. The synthesised materials are morphologically and mechanically characterised. Using different porogens in the polymer synthesis results in different mechanical strength and fluid flow characteristics. The results indicate that the fluid flow characteristics of the polymers can be sacrificed to improve strength. Optimum polymer strength can be attained by synthesising polymers with macropores that are interconnected via nanopores using the minimum amount of porogenic solvents.

Comparative analysis of parameters affecting micro-forming process

Engineering review, 2023

This review paper provides a comprehensive analysis of the various factors affecting micro-forming and the parameters involved in manufacturing micro-parts. To ensure minimal wear and tear and error-free products, it is important to optimize both the process parameters and framework. The paper aims to highlight the importance of metal micro-forming technology in designing and manufacturing highly precise micro metallic devices, biodegradable implants, micro-pumps, and gears. Through this review paper, readers can gain a better understanding of metal micro-forming, the variables that influence micro-forming and deep drawing, and the process parameters that affect micro-forming and deep drawing technology. Optimizing the process parameters is crucial for the success of micro-forming and can lead to improved product quality, increased production efficiency, cost reduction, process robustness, and improved material properties. The paper specifically discusses the significance of parameters such as blank holder force and size effects on variables that play an important role in optimizing the metal micro-forming process.

Modeling of sequential reactions during micropyretic synthesis

Metallurgical and Materials Transactions A, 1996

A numerical model for a two-step sequential micropyretic reaction is reported. Such multiple reactions can take place during micropyretic synthesis of composite materials. The model was developed for the aluminothermic reaction between molybdenum oxide, aluminum, and silicon, which react to give molybdenum disilicide and aluminum oxide. The model was used to obtain the solution for the propagation of the combustion front. The melting of various constituents of reactants and products was incorporated into the model. The effect of the pre-exponential factor and the amount of diluent on the nature of propagation and temperature profile was investigated. Other conditions of propagation and synthesis for general two-step reactions were explored by changing the activation energy and heat release of each sequential reaction. A mapping procedure to characterize the types of sequential reactions is proposed and studied for several aluminothermic type reactions.

Preparation of porous materials with controlled pore size and porosity

Journal of the European Ceramic Society, 2004

Well-defined porous ceramics with controllable pore size and porosity were fabricated via a hetero-coagulation of template/ ceramic particle colloidal processing. Monodispersed polymer spheres were used as template and ceramic nanoparticles as inorganic building blocks to create porous structures. The preparation of well-dispersed suspensions of polymers and ceramics is essential for the fabrication of uniformly porous materials. Core-shell composites of polymer/ceramic could be obtained by mixing the oppositely charged two suspensions via electrostatic attraction following by filtration and calcination to produce macroporous ceramic materials. SEM images and pore size distribution results revealed that various materials, such as Al 2 O 3 , TiO 2 and ZrO 2 , with ordered and uniform macropores have been obtained by this simple procedure. The pore size could be controlled readily by varying the polymer size and the porosity could be manipulated by modifying the volume ratio of polymer/ceramic particles. #