Additive manufacturing of metals

1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

Biodegradable metals are breaking the current paradigm in biomaterial science to develop only corrosion resistant metals. In particular, metals which consist of trace elements existing in the human body are promising candidates for temporary implant materials. These implants would be temporarily needed to provide mechanical support during the healing process of the injured or pathological tissue. Magnesium and its alloys have been investigated recently by many authors as a suitable biodegradable biomaterial. In this investigative review we would like to summarize the latest achievements and comment on the selection and use, test methods and the approaches to develop and produce magnesium alloys that are intended to perform clinically with an appropriate host response.

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Degradable biomaterials based on magnesium corrosion

Additive manufacturing (AM) technology has been researched and developed for more than 20 years. Rather than removing materials, AM processes make three-dimensional parts directly from CAD models by adding materials layer by layer, offering the beneficial ability to build parts with geometric and material complexities that could not be produced by subtractive manufacturing processes. Through intensive research over the past two decades, significant progress has been made in the development and commercialization of new and innovative AM processes, as well as numerous practical applications in aerospace, automotive, biomedical, energy and other fields. This paper reviews the main processes, materials and applications of the current AM technology and presents future research needs for this technology.

Additive manufacturing: technology, applications and research needs

Nanocomposites, a high performance material exhibit unusual property combinations and unique design possibilities. With an estimated annual growth rate of about 25% and fastest demand to be in engineering plastics and elastomers, their potential is so striking that they are useful in several areas ranging from packaging to biomedical applications. In this unified overview the three types of matrix nanocomposites are presented underlining the need for these materials, their processing methods and some recent results on structure, properties and potential applications, perspectives including need for such materials in future space mission and other interesting applications together with market and safety aspects. Possible uses of natural materials such as clay based minerals, chrysotile and lignocellulosic fibers are highlighted. Being environmentally friendly, applications of nanocomposites offer new technology and business opportunities for several sectors of the aerospace, automotive, electronics and biotechnology industries.

/pdf/nanocomposites-synthesis-structure-properties-and-new-4nejccptqe.pdf

Nanocomposites: synthesis, structure, properties and new application opportunities

The purpose of this study was to investigate the influence of Cu-coating on the spreading kinetics and equilibrium contact angles of aluminum on ceramics using a sessile drop technique. Al2O3 and SiC plates were coated by electroless plating. The copper film overcomes the low wetting of the uncoated samples by dissolution in the drop at 800 °C in argon, showing an intrinsically favorable effect on the adhesion energy. Just after 2 min, the contact angle decreased to 12.6° and 26°for Al/Cu–Al2O3 and Al/Cu–SiC, respectively. However, a de-wetting behavior was observed, reaching equilibrium contact angles of 58.3° and 45.5° for the couples. The dissolution reaction rate at the triple junction was so high that the spreading process was controlled by local diffusion rather than chemical reaction kinetics.

Wettability and spreading kinetics of molten aluminum on copper-coated ceramics

Engineering ceramics such as alumina, zirconia, silicon nitride and silicon carbide can now be manufactured reliably with reproducible properties As such, they are of increasing interest to industry, particularly for use in demanding environments, where their thermomechanical performance is of critical importance, with applications ranging from fuel cells to cutting tools One aspect common to virtually all applications of engineering ceramics is that eventually they must be joined with another material, most usually a metal The joining of engineering ceramics to metals is not always easy There are two main considerations The first consideration is the basic difference in atomic bonding: the ionic or covalent bonding of the ceramic, compared to the metallic bond The second consideration is the mismatch in the coefficient of thermal expansion In general, ceramics have a lower coefficient of thermal expansion than metals and, if high tensile forces are produced in the ceramic, either a

Joining of engineering ceramics

The structural evolution of carbon nanotubes (CNTs) during mechanical milling was investigated using SEM, TEM, XRD, XPS and Raman spectroscopy. The study showed that milling of the CNTs alone introduces defects but preserves the tubular structure. When milling the CNTs with aluminum (Al) powder in order to produce a composite, Raman spectroscopy has shown that most of the nanotubes are destroyed. During sintering of the CNT/Al milled mixture, the carbon atoms available from the destruction of the nanotubes react with the Al to form aluminum carbide (Al4C3). The effect of milling on the Al matrix was also studied.

Structural characterization of a mechanically milled carbon nanotube/aluminum mixture

The preparation of nickel-coated ceramic particles as precursors for MMC fabrication was studied. Al2O3 and SiC powders of three different particle sizes were successfully coated with Ni using an electroless metal plating technique. Uniform and continuous nickel films were deposited on both, alumina and silicon carbide powders, with a final composition ranging from 1.6 to 1.9wt% phosphorus, 18–21wt% of metallic nickel and the balance is ceramic. XRD showed that the Ni-P deposit was predominantly amorphous. However, after heat treatment, the metallic deposits crystallize into Ni and Ni3P phases, as confirmed by DSC analyses. Preliminary results showed that the use of Ni-coated powders enhances the wettability between the matrix and ceramic phase when processing particulate MMCs by infiltration techniques. The coating promoted easy metal flow through the preform, compared to the non-infiltration behavior of the uncoated counterpart samples.

Robin A. L. Drew

Papers

Wettability and spreading kinetics of molten aluminum on copper-coated ceramics

Joining of engineering ceramics

Structural characterization of a mechanically milled carbon nanotube/aluminum mixture

Preparation of nickel-coated powders as precursors to reinforce MMCs

Wettability and spreading kinetics of Al and Mg on TiC