Multifunctional dream ceramic matrix composites are born!

December 05, 2018

Researchers at Osaka University produced composites consisting of alumina (AI2O3) ceramics and titanium (Ti), namely AI2O3/Ti composites. They designed a percolation structure for forming a continuous conduction pathway by dispersing fine-sized Ti particles into an AI2O3 matrix, optimizing the particle size of metallic Ti powder and sintering processes. They improved fracture toughness and electrical conductivity of AI2O3/Ti composites while simultaneously giving them photocatalytic ability through chemical and/or thermal treatment. (Figure 1)

Various types of metal-ceramic composites have been researched and developed, but their combination and fine structures were limited. In particular, the combination of ceramics such as alumina used as matrices and titanium, a biocompatible metal, has a problem in that the structure of composites is not uniform because of the high reactivity of titanium (oxidation happens and chemical compounds are produced) and the large particle size of commercially-available Ti powder (several tens of micrometers). Thus, it was difficult to produce composites that have advantages of both ceramics and metal: that is, composites in which metallic Ti powder is homogeneously dispersed in the matrix and has excellent mechanical properties.

The group prepared ball-milled titanium hydride (TiH2) fine powder mixed with alumina powder, producing AI2O3/Ti composites using a method based on the in situ decomposition of TiH2 to Ti and simultaneous sintering with Al2IO3, which process inhibited AI2O3 dissolution into Ti by diffusion through interfacial reaction between AI2O3 and Ti during sintering. As a result, they minimized reactivity of Ti and AI2O3 to disperse significantly finer and more homogeneous Ti (compared to those produced with conventional methods) in AI2O3, realizing composites with a percolation structure by controlling the content of added Ti.

In this way, the group improved fracture toughness of inherently brittle AI2O3 through dispersion of fine Ti particles into AI2O3 and, due to percolation of metallic Ti particles, contributing electrical conductivity to insulator ceramics AI2O3. They also demonstrated that AI2O3 ceramics could be machined by electrical discharge machining like metals. (Usually, ceramics are not electrically conductive.) In addition, they formed a nano-porous- or nanorod- structured titania layer on the surface of the composite by selectively oxidizing Ti via NaOH treatment and/or heat treatment. Through this, they demonstrated that the photocatalytic ability to break down organic substances could also simultaneously be given to AI2O3/Ti composites.

Group leader Tohru Sekino says, "AI2O3/Ti composites will be used as ceramic matrix composites that have excellent mechanical properties and can be machined by electrical discharge machining. They will also be used for industrial products and biomaterials as new multi-functional composites that have an active surface layer with antibacterial properties and a photocatalytic ability to break down pollutants."
-end-
Other Related Articles

Article: Formation of vertically grown 1D TiO2 nanorods on the surface of AI2O3/Ti composites by simple heat treatment and their photocatalytic performance
Journal: Journal of the Ceramic Society of Japan
DOI: 10.2109/jcersj2.18133
Authors: Shengfang SHI, Tomoyo GOTO, Sung Hun CHO, Hideki HASHIMOTO, Shu YIN, Soo Wohn LEE and Tohru SEKINO

Article: Combinative effects of Y2O3 and Ti on AI2O3 ceramics for optimizing mechanical and electrical properties
Journal: Ceramics International
DOI: 10.1016/j.ceramint.2018.07.054
Authors: Shengfang Shi, Sunghun Cho, Tomoyo Goto, Takafumi Kusunose, and Tohru Sekino

Article: Fine Ti-dispersed AI2O3 composites and their mechanical and electrical properties
Journal: Journal of the American Ceramic Society
DOI: 10.1111/jace.15472
Authors: Shengfang Shi, Sunghun Cho, Tomoyo Goto, Tohru Sekino

About Osaka University

Osaka University was founded in 1931 as one of the seven imperial universities of Japan and now has expanded to one of Japan's leading comprehensive universities. The University has now embarked on open research revolution from a position as Japan's most innovative university and among the most innovative institutions in the world according to Reuters 2015 Top 100 Innovative Universities and the Nature Index Innovation 2017. The university's ability to innovate from the stage of fundamental research through the creation of useful technology with economic impact stems from its broad disciplinary spectrum. Website: https://resou.osaka-u.ac.jp/en/top

Osaka University

Related Titanium Articles from Brightsurf:

From lab to industry? Ideally ordered porous titania films, made at scale
Researchers from Tokyo Metropolitan University have realized high-throughput production of thin, ordered through-hole membranes of titanium dioxide.

A 40-year-old catalyst unveils its secrets
Activity of the industrial catalyst TS-1 relies on titanium pairs / important discovery for catalyst development

Direct observation of a single electron's butterfly-shaped distribution in titanium oxide
A research team led by Nagoya University has observed the smeared-out spatial distribution of a single valence electron at the centre of a titanium oxide molecule, using synchrotron X-ray diffraction and a new Fourier synthesis method also developed by the team.

Titanium oxide-based hybrid materials promising for detoxifying dyes
Photoactive materials have become extremely popular in a large variety of applications in the fields of photocatalytic degradation of pollutants, water splitting, organic synthesis, photoreduction of carbon dioxide, and others.

Scientists have created new nanocomposite from gold and titanium oxide
ITMO University researchers together with their colleagues from France and the USA have demonstrated how a femtosecond laser can be used to tune the structure and nanocomposite properties for titanium dioxide films filled with gold nanoparticles.

Skoltech scientists developed a new cathode material for metal-ion batteries
Researchers from the Skoltech Center for Energy Science and Technology (CEST) created a new cathode material based on titanium fluoride phosphate, which enabled achieving superior energy performance and stable operation at high discharge currents.

First view of hydrogen at the metal-to-metal hydride interface
University of Groningen physicists have visualized hydrogen at the titanium/titanium hydride interface using a transmission electron microscope.

The properties of thin titanium oxide films have been studied
Some titanium oxides are known for their unique properties, such as increased photocatalytic activity (i.e. they effectively use light to speed up chemical reactions).

Adding copper strengthens 3D-printed titanium
Successful trials of titanium-copper alloys for 3D printing could kickstart a new range of high-performance alloys for medical device, defence and aerospace applications.

Fatigue-resistant, high-performance cooling materials enabled by 3D printing
High-performance solid-state elastocaloric cooling materials with exceptional fatigue resistance are made possible by 3D printing a nickel-titanium based alloy, researchers report.

Read More: Titanium News and Titanium Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.