Advanced Materials Processing Research Articles

Integrated Robotic Plasma Spraying System for Advanced Materials Processing

During atmospheric plasma spraying (APS), to control the time dependent D.C. plasma jet behavior requires the comprehensive understanding of its electric, magnetic, thermal, thermodynamic phenomena. In this paper, influence of particles injection with the form of suspension on the fluctuation of plasma jet is analyzed, and a control approach is presented to eliminate the effect. Moreover, an integrated robotic plasma spraying system for advanced materials processing, i.e., rapid metal tooling and solid oxide fuel cell (SOFC), is developed, which combines a PC-based controller with a six-aids robot. The intelligent adaptive adjustment of robot spraying trajectories and self-dispatch of manufacturing strategies were carried out by the resultant system according to the feedback of the temperature and thickness of sprayed coatings and other information during plasma praying. The flexibility of the forming system was promoted by integrating plasma spray forming with robot motion control. Excellent control performance is observed and this system can be effective to meet the requirements of different materials processing techniques.

Application of phase diagram calculations to development of new ultra-high temperature structural materials

In-situ refractory metal intermetallic composites(RMICs) based either on (Nb, Si) or (Mo, Si, B) are candidate materials for ultra-high temperature applications (>1 400 °C). To provide a balance of mechanical and environmental properties, Nb-Si composites are typically alloyed with Ti and Cr, and Mo-Si-B composites are alloyed with Ti. Phase diagrams of Nb-Cr-Ti-Si and Mo-Si-B-Ti, as prerequisite knowledge for advanced materials design and processing development, are critically needed. The phase diagrams in the metal-rich regions of multicomponent Nb-Cr-Ti-Si and Mo-Si-B-Ti were rapidly established using the Calphad (Calculation of phase diagram) approach coupled with key experiments. The calculated isotherms, isopleths, and solidification paths were validated by experimental work. The important heterogeneous multiphase equilibria in both quaternary systems identified will offer engineers the opportunity to develop materials with a balance of properties for high-temperature applications.

Cost-effective power converter for thin film solar cell technology and improved power quality

Abstract Advances in material processing cause that new solar cell technologies are emerging. Emerging photovoltaic solar cell technologies such as thin film and photoelectrochemical (PEC) solar cells tend to be cheaper than silicon cells made in standard technologies. The high cost of crystalline silicon wafers representing up to 50% of the solar module cost has led the industry to find more cost-effective materials for solar cells production. Using a vacuum spraying process, very thin layers (0.3–1 μm) can be applied on glass, metal or even flexible plastic surfaces. Main difference between technologies is that new technologies use decreased number of solar cells so the lower dc voltage has to be inverted. It is expected that new types of converters are going to appear in order to achieve low voltage/high current conversion into the grid. In this paper the H-bridge active power filter with variable voltage is proposed. Its advantages and disadvantages are compared with the standard inverter—active power filter (APF) as well with an APF with boost converter (commercial solution). This article also shows the impact of different solar cell technologies on power converters and the impact of advances in material processing technologies on other branches of engineering.

Hydrothermal processing of materials: past, present and future

The hydrothermal technique provides an excellent possibility for processing of advanced materials whether it is bulk single crystals, or fine particles, or nanoparticles. The advantages of hydrothermal technology have been discussed in comparison with the conventional methods of materials processing. The current trends in hydrothermal materials processing has been described in relation to the concept of soft solution processing, as a single-step low energy consuming fabrication technique. Also some recent developments in multi-energy processing of materials such as microwave-hydrothermal, mechanochemical-hydrothermal, electrochemical-hydrothermal, sonar-hydrothermal, etc. have been discussed. An overview of the past, present and future perspective of hydrothermal technology as a tool to fabricate advanced materials has been given with appropriate examples.

Processing of Advanced Materials Using Conventional and Shock Techniques

Some of the activities of the Laboratory of Manufacturing Technology of the NTUA in manufacturing engineering are reported, focusing onto some recent trends and developments in advanced manufacturing of advanced materials, in the important engineering topics nowadays from industrial, research and academic point of view: nanotechnology/nanostructured materials, synthesis and net-shape fabrication of superconductors, biomedical engineering and solar energy devices.

A review on the synthesis of in situ aluminum based composites by thermal, mechanical and mechanical–thermal activation of chemical reactions

The aim of the present paper is to review the recent progress in the synthesis of in situ particle reinforced aluminum composites using thermal, mechanical and combined mechanical-thermal activation of aluminothermic reduction reactions. The combination of combustion synthesis (CS) and mechanosynthesis (MS) is the most recent development in the processing of advanced materials like micro and nano aluminum based composites. The combined mechanical thermal synthesis (MTS) has widened the possibilities for both CS and MS. MTS holds great potential for commercial viability and offers exciting processing route for the synthesis of advanced materials. Enhanced reaction kinetics and extended concentration limits in MTS are demonstrated by illustrating the synthesis of aluminum based nanocomposite involving Al–CeO2.

Computational Thermodynamics and Kinetics in Materials Modelling and Simulations

Over the past two decades, Computational Thermodynamics and Kinetics have been tremendously contributed to materials modeling and simulations and the demands on quantitative conceptual design and processing of various advanced materials arisen from various industries and academic institutions involved in materials manufacturing, engineering and applications are still rapidly increasing.

Advanced material processing with nano- and femto-second pulsed laser

In order to apply laser processing to advanced material mold making, basic research is carried out. First, box-shaped hole processing is carried out by laser beam scanning. Second, suitable machining conditions are investigated in terms of laser spot size, scanning path, scanning speed and scan times. Finally, the comparison of nano- with femto-second laser-processed surfaces is carried out. The laser-processed surfaces and debris are observed with a scanning electron microscope (SEM) and a laser microscope, and are also analyzed using an electron probe microanalysis (EPMA), an X-ray diffractometer and a Vickers hardness tester.

Particle deposition mechanisms during processing of advanced composite materials

Liquid composite moulding of advanced composite materials often comprises infiltration of a particle-filled resin into a multi-scale porous fabric. These injections/infusions are subject to severe particle depositions inside the reinforcement, leading to undesired inhomogeneous mechanical and functional properties. Hence, the mechanisms for particle depositions are investigated by detailed meso-scale experiments, analysed by microscopic imaging and micro-particle image velocimetry, and macroscopic infusions of a biaxial non-crimp fabric. It is shown that two main particle deposition mechanisms are filtration during fibre bundle impregnation and filtration induced by stationary flow through fibre bundles. It is also clarified where in the reinforcement the particles will deposit. Finally, a number of suggestions on how to process advanced composite materials with a more homogeneous particle distribution are launched.

Adaptive Modeling of Laser Powder Deposition Process for Control and Monitoring Application

The laser powder deposition (LPD) process is an advanced material processing technique with many applications. Despite this fact, reliable and accurate control schemes have not yet been fully developed for the process. In this paper, identification of the LPD process is examined to find a more accurate model to predict and control the height of clad in real time. The model is adaptive single input—single output (SISO) and its structure is very similar to the Hammerstein model when the effective power (a function of laser power and velocity) is selected as the input and the clad height as the output. Weighted extended recursive least square (WERLS) is adopted to simultaneously estimate the model parameters using experimental data. Comparison of the results shows that this method can be used very efficiently in control of laser powder deposition process.

Micromolding in capillaries and microtransfer printing of silver nanoparticles as soft-lithographic approach for the fabrication of source/drain electrodes in organic field-effect transistors

Abstract Within the past years there has been much effort in developing and improving new techniques for the processing of advanced functional materials used in promising applications like micro-optics or organic electronics. Much attention has been paid to solution-based techniques, which enable low-cost processing and new possible developments like flexible displays or inkjet printed electronics. An alternative approach to inkjet printing is soft-lithography, which is a collective term for a number of non-photolithographic techniques and has become an important tool for the micron-sized structuring of materials. Here we report on the use of micromolding in capillaries (MIMIC) and microtransfer printing (μTP) as two soft-lithographic techniques for the fabrication of silver source/drain electrodes in well-performing bottom-gate/bottom-contact organic field-effect transistors (OFETs) with poly(3-hexylthiophene) as active layer material. While MIMIC combines solution-processability with high lateral resolution for highly accurate patterns, μTP is the miniaturized counterpart to conventional letterpress printing. The performance of the OFETs fabricated with these techniques is similar to devices based on conventional gold source/drain electrodes with well-defined source-to-drain current saturation and a linear behavior at low drain voltages suggesting a low contact resistance and hence good carrier injection from the silver electrodes into the organic semiconductor.

Cladding of WC–12 Co on low carbon steel using a pulsed Nd:YAG laser

Laser cladding is an advanced material processing technology that has potential to deposit various materials locally on highly non-planar and complex surfaces. It can be used to refurbish or improve corrosion, wear and other surface related properties of components. The laser cladding of WC–Co using continuous wave (CW) laser has been tried and problems, like—cracks, porosity, poor bonding, partial melting of WC particles in the Co matrix, etc., have been observed. To resolve these issues, the successful laser cladding with alternate binder materials, like—Ni, Fe, Co–Cr, Ni–B–Si, etc., have been reported. In the present study, a pulsed Nd:YAG laser was used to deposit multi-layer overlapped cladding on low carbon steel substrate using dynamic powder blowing technique. Thus, produced laser cladding samples were subjected to various mechanical tests and metallurgical analyses. The results showed that fully dense and crack free clad surfaces of WC–Co with an excellent metallurgical bonding and low dilution were deposited. No melting of WC particles in the Co matrix was observed during the microscopy. The average microhardness at the clad surface was about 1350 HV, while that at substrate was 200 HV. The observed adhesion strength of the WC–Co cladding to the substrate was about 60 MPa.

Electrohydrodynamic Processing Routes for Bioceramics

Bioceramic fibres, scaffolds and mats are important structures in biomedical applications. Electrohydrodynamic routes are relatively new for processing advanced materials and in this paper we use electrospinning to prepare zirconia fibres diameter down to 200nm and hydroxyapatite (HA) fibres down to 1$m. Zirconia-polymer and nHA-polymer composite scaffolds structures (mats) with 400-1000 $m windows were also prepared.

Biohybrid polymers: novel options for regenerative therapies

genetic matrices polymeric materials capable of rekindling the cellular potential to regenerate tissues and organs evolve into a new paradigm of biomaterials research: Advanced therapeutic concepts require biodegradable cell scaffolds transmitting spatio-temporal sequences of signals to trigger cellular fate decisions. To this end, three-dimensional carrier structures have to provide fine-tuned physical characteristics and specific adhesion sites, the formation of chemokine gradients and the presentation of growth factors. So far, a vast majority of materials applied for that purpose is either based on reconstituted extracellular matrix biopolymers such as collagen I or on common biodegradable polymer (bio)materials such as polylactide. A wealth of technologies has been developed for the advanced processing of these materials. To extend the resulting options biohybrid polymers – biopolymers covalently linked to synthetic polymers – receive more and more attention: A key feature of this emerging class of polymeric materials concerns the modulation of the specific signalling properties of the incorporated biomolecules. This may even allow for tuning of signal profiles of the bioactive scaffold structures beyond the characteristics of naturally occurring matrices – to switch cells into the ‘regeneration mode’. Another advantage of biohybrid polymers is related to their localized application via injection which is an important prerequisite of in vivo tissue engineering strategies. Based on these principles biohybrid polymers may be expected to induce regeneration processes where we are missing them as urgently as in the injured heart muscle after myocardium infarction. Successful examples of biohybrid polymers include polyethylene glycol (PEG) based networks with enzymatically cleavable peptide units to permit the ingrowth of cells ‘on demand’, i. e. in response to the local cellular activity or PEG-tethered transforming growth factor beta (TGF-b) to regulate smooth muscle cell function. Self assembling nanostructures of peptide-amphiphiles define another category of biohybrid materials with particular advantages for in vivo tissue engineering strategies. The rapid progress in genetic engineering and synthesis of biomimetic peptide and carbohydrate structures will broaden the applicability of biohybrid polymers further and foster the merging of the strengths of molecular life science and ‘classical’ polymer science for the rational design bioactive materials. Progress of regenerative therapies is critically dependent on that.

Application of high magnetic fields in advanced materials processing

Recently, steady magnetic fields available from cryogen-free superconducting magnets open up new ways to process materials. In this paper, the main results obtained by using a high magnetic field to process several advanced materials are reviewed. These processed objects primarily include superconducting, magnetic, metallic and nanometer-scaled materials. It has been found that a high magnetic field can effectively align grains when fabricating the magnetic and non-magnetic materials and make inclusions migrate in a molten metal. The mechanism is discussed from the theoretical view-point of magnetization energy.

A Biomimetic Approach for Hierarchically Structured Inorganic Crystals through Self-Organization

Abstract Here, we describe a biomimetic pathway for the synthesis of hierarchically structured inorganic crystals. In artificial systems mimicking biomineralization, versatile morphogenesis was achieved with the construction of bridged nanocrystals through self-organization by controlling growth with polymeric molecules such as a gel matrix and soluble anionic polymers. The self-organized formation of bridged crystals in hierarchical architectures is a possible new paradigm for advanced materials processing which could afford new inorganic–organic nanocomposites for use as novel functional materials.

Study on process of dual-frequency electromagnetic confinement and shaping for stainless steel

Electromagnetic confinement and shaping (EMCS) is an advanced materials processing technique. In this paper, a novel dual-frequency EMCS was proposed, i.e. lower frequency magnetic field (20 kHz) was used to produce the electromagnetic force, and higher frequency magnetic field (50 kHz) to heat and melt metal materials without effect on the electromagnetic force. Shaping inductors and heating inductors were designed according to the experimental results and our previous works, and distance between them was experimentally determined. Stability of dual-frequency EMCS of melt was detailedly analyzed. At last, several stainless steel samples were produced by the new method, and results show that it can easily achieve good coupling of temperature field and electromagnetic force by separately designing and controlling the two magnetic fields.

We do exactly what every other anesthesia group does, so why are we doing so poorly?

Application of electromagnetic force to materials processing, so called Electromagnetic Processing of Materials (EPM) has been recognized as a cutting edge technology, especially in the fields of advanced materials processing. The background to promote EPM is described. The present state of EPM is given through a brief introduction of several examples of the applications of a high frequency magnetic field, a DC magnetic field, DC magnetic and electric fields, and a traveling magnetic field. Furthermore, a high static magnetic field has been applied to generate compression waves in molten metals. As other examples of the application of a high static field, the crystal orientations in thin films in vapordeposition and electrodeposition processes and those in carbon fibers in a graphitization process are described. Finally the future view of EPM is revealed.

Study on Morph-Genetic Materials Derived from Natural Structure

Synthesis of morph-genetic materials derived from biological structures by rapid, high temperature conversion represents a novel technology of advanced materials processing. The resulting morph-genetic materials exhibit unique macro- and microscopic cellular morphologies. In addition, based on the porous character of some natural plants, there is a further possibility of compounding the resulting morph-genetic materials with molten metal or polymer to produce morph-genetic composites with interpenetrating networks. Thus, the morph-genetic materials will be endowed with new use values, such as good mechanical properties, and friction behaviors, etc.

Design for Living

W hen a child sees a bird flying past or the fluttering wings of a butterfly, does it inspire thoughts about how to build airplanes? Or does it simply convey the idea that flight is possible? We are immersed in the natural world, so it is not surprising that it inspires the design of engineered structures, or that we would like to probe this world further to learn all its secrets. The four Reviews in this issue highlight this two-sided relationship as it applies to the development of new materials. From nature we have learned how soft brittle materials like chalk are made tougher through composite structures. Some of these same design principles have been applied to the much wider range of building blocks available to the engineer (Mayer, p. [1144][1]). Advances in materials processing, particularly in the area of polymers, are also making it possible to fabricate systems with advanced optical capabilities (Lee and Szema, p. [1148][2]), inspired by living eyes and by creatures that we have recently learned can see even though they appear to lack eyes. On the flip side, new material systems have been designed to probe and manipulate biological interactions. Two Reviews examine highly complementary questions. The first summarizes what has been learned about the interactions of cells with surfaces that possess features at different size scales (Stevens and George, p. [1135][3]). The second explores how cells sense the stiffness and strength of underlying substrates (Discher et al. , p. [1139][4]). From both we see how new materials are being used to probe cell cycles and interactions and to coax cells to grow in desired ways. The drive toward medical applications is helping push research at the biology/materials interface. On the small scale, nanotechnology is being explored to find new methods for cancer detection and treatment (Service, p. [1132][5]). A Science of Aging Knowledge Environment (SAGE KE) feature story by Davenport explores the progress and problems of engineering tissues in the lab. This endeavor could revolutionize medicine, potentially reversing illnesses such as diabetes, heart disease, and liver failure. As research at the interface between materials and biology increasingly overlaps, we look forward to seeing how each continues to inspire developments in the other. [1]: /lookup/doi/10.1126/science.1116994 [2]: /lookup/doi/10.1126/science.1115248 [3]: /lookup/doi/10.1126/science.1106587 [4]: /lookup/doi/10.1126/science.1116995 [5]: /lookup/doi/10.1126/science.310.5751.1132