NANOTECHNOLOGIES

Invisibility Cloak: New Technique To Control Nanoparticles

2008-03-06T23:45:00.000-08:00

Through a collaborative effort, researchers from the departments of Materials Science and Engineering and Chemistry have developed a new design paradigm that makes particles invisible.

In a recent edition of Advanced Materials Magazine, the researchers demonstrate that controlling the structure of nanoparticles can "shrink" their visible size by a factor of thousands without affecting a particle's actual physical dimension.

"What we are doing is creating a novel technique to control the architecture of nanoparticles that will remedy many of the problems associated with the application of nanomaterials that are so essential to business sectors such as the aerospace and cosmetics industry," said Bockstaller, an assistant professor of materials science and engineering.

Colloidal particles are omnipresent as additives in current material technologies in order to enhance strength and wear resistance and other attributes. Light scattering that is associated with the presence of particles often results in an undesirable whitish, or milky, appearance of nanoparticles, which presents a tremendous challenge to current material technologies. Carnegie Mellon researchers have successfully created a way to prevent this problem by grafting polymers onto the particles' surface.

"Essentially, what we learned how to do was to control the density, composition and size of polymers attached to inorganic materials which in turn improves the optical transparency of polymer composites. In a sense, light can flow freely through the particle by putting 'grease' onto its surface," said Matyjaszewski, the J.C. Warner University Professor of Natural Sciences in the Department of Chemistry.

The new "particle invisibility cloak" will help create a vast array of new material technologies that combine unknown property combinations such as strength and durability with optical transparency.

Adapted from materials provided by Carnegie Mellon University.

The Use of Instrumented Indentation to Measure Hardness and Elastic Properties of Tablets

2008-03-06T23:36:00.000-08:00

Background

This paper presents the use of instrumented indentation as a mean to measure hardness and elastic properties of tablets, a technique proven to be more advantageous, reliable and precise than conventional techniques. Hardness and Young’s modulus are reported.

Optically measuring the diagonals of indents is a well-established technique used to determine the hardness of bulk materials and coatings. Unfortunately, this technique is limited in its applications.At low loads, the indents can be so small that determining their size can involve unacceptable human errors. The texture and appearance of the surface can also complicate the observations, which is especially the case for tablets.

Instrumented indentation is based on the analysis of the load-penetration curve measured while doing an imprint. It is computer-controlled and it is not influenced by the operator’s judgment of the imprint’s shape. Properties such as hardness, Young’s modulus, fracture toughness and creep behavior can be determined with a single indent. Load-penetration curves also reveal the load and depth at which cracking and failure occur.

Samples

The tablets are made of polymers, A and B, shaped in 1 centimeter diameter disks and have porosity (P) ranging from 3 to 8%. Measurements were performed in the center of the disks.

Instrument

The Micro Hardness Tester (MHT) from CSM Instruments was used with a Vickers diamond indenter. Values of hardness and Young’s modulus are computed using the Oliver and Pharr theory. Indentation is performed in less than 5 minutes including the time for tip approach.

Testing Parameters

Two sets of parameters are presented 1) Maximum load: 0.2N, loading rate: 0.4N/min, pause: 15s and 2) Maximum load: 1N, loading rate: 1N/min, pause: 15s.

Results and Discussion

Figure 1 shows a picture of a tablet after an indentation was performed with a maximum load of 1N.

Figure 1. Indent on a tablet with 1N load

It reveals no apparent trace of imprint complicating the computation of hardness using conventional method in which case the diagonal is measured optically.

Figure 2. What indent should look like

Thus using load-penetration curves (Fig. 3) from the instrumented indentation technique allows us to measure the level of hardness and Young’s modulus of various tablets with known porosity (Tables 1 and 2).

Figure 3. Example of indentation curve

Table 1. Hardness (Hv, H), Youngs’ modulus (E) and penetration depth (ƒ´d) for maximum load of 0.2N

Tablet	P [%]	Hv [Vickers]	H [MPa]	E [GPa]	ƒ´d [ ƒÝm ]
A	3	32	338	9.1	5.358
A	4	29	305	8.1	5.625
A	8	26	278	7.7	5.869
B	3	13	136	3.1	8.575
B	6	12	122	2.6	9.043
B	8	7	74	1.7	11.634

Table 2. Hardness (Hv, H), Youngs’ modulus (E) and penetration depth (ƒ´d) for maximum load of 1N

Tablet	P [%]	Hv [Vickers]	H [MPa]	E [GPa]	ƒ´d [ ƒÝm ]
A	3	34	360	9.3	11.663
A	4	23	246	3.4	15.044
A	8	15	159	6.1	17.016
B	3	13	141	3.1	18.886
B	6	10	107	2.6	21.357
B	8	3	34	0.4	42.331

The sensitivity of the technique facilitates the monitoring of these properties even for small changes in porosity (1%) as well as in function of depth by using different indentation loads.

Primary author: Ethel Poiré

Source: EP Laboratories adapted from original poster presented at Biomaterials 2005

For more information on this source please visit EP Laboratories

Gold 2009 - International Conference on the Science, Technology and Applications of Gold

2008-03-06T23:18:00.000-08:00

The field of gold science and technology continues to undergo an exciting period of discovery. World Gold Council and the University of Heidelberg are pleased, therefore, to announce their co-organisation of the 5th international conference on gold science, technology and its applications at the University of Heidelberg, Germany between Sunday 26th – Wednesday 29th July 2009.

Gold Conferences History

This conference follows the successful and stimulating conferences held in Cape Town (2001), Vancouver (2003) and Limerick (2006) and the earlier meeting on 'Progress in the Science and Technology of Gold’ which took place in Hanau, Germany in 1996. Many scientists and technologists in academia and industry have praised the excellence of these forums, where they can come together to learn of and discuss the latest advances, with the overall objective of encouraging important new industrial applications for gold.

Conference Themes

Gold 2009 will cover all aspects of the science, technology and applications of gold under the principal themes:

Catalysis
Chemistry
Nanotechnology
Materials

Technical Programme

The Gold 2009 conference will cover all aspects of the science, technology and applications of gold, including, but not limited to:

Alloy catalysts
Applications - fuel cells, pollution control, chemical processing, sensors
Catalyst preparation and characterisation
Chemistry on gold surfaces
Electrocatalysis
Gas and liquid phase heterogeneous systems
Gold-support interaction
Homogeneous systems

Chemistry

Biochemistry and medical applications
Electrochemistry
Fluorescence phenomena and applications
Ligand design
New reactions
New structures
Supramolecular chemistry

Materials

Alloys and metallurgy
Coating technology
Composites and novel materials
Decorative technologies
Dental materials and applications
Electroless and immersion gold deposition
Electronic materials applications
Electroplating and electroforming

Nanotechnology

Applications - decorative, electronic, medical
Colloid technology
Cluster science
Nanoparticles and wires - preparation & characterisation
Photophysical properties
Self assembly systems

Posted March 2009

For more information please contact Ms Christiane Eckert
URL: www.gold2009.or