Background

The discovery of fullerenes in 1985 by Curl, Kroto, and Smalley, culminated in their Nobel Prize in 1996. Fullerenes, or Buckminsterfullerenes, are named after Buckminster Fuller, the architect and designer of the geodesic dome, and are sometimes called bucky balls. The names derive from the basic shape that defines fullerenes; an elongated sphere of carbon atoms formed by interconnecting six-member rings, and twelve isolated five-member rings forming hexagonal and pentagonal faces. The first isolated and characterized fullerene, C60, contains 20 hexagonal faces and 12 pentagonal faces, just like a soccer ball, and possesses perfect icosahedral symmetry.
Fullerenes - Potential Industry Applications and Recent Developments

Fullerene chemistry continues to be an exciting field, generating many articles with promising new applications every year. Magnetic nanoparticles (nanomagnetic materials) show great potential for high-density magnetic storage media. Recent work has shown that C60 dispersed into ferromagnetic materials such as iron, cobalt, or cobalt iron alloy can form thin films with promising magnetic properties. A number of organometallic-fullerene compounds have recently been synthesized. Of particular note are a ferrocene-like C60 derivative and pair of fullerenes bridged by a rhodium cluster. Some fullerene derivatives even exhibit superconducting character. There has been a report of a fullerene containing a superconducting field-effect device with a Tc as high as 117K.
Structure and Different Types of Carbon Nanotubes

Carbon nanotubes (CNTs) are hollow cylinders of carbon atoms. Their appearance is that of rolled tubes of graphite, such that their walls are hexagonal carbon rings, and they are often formed in large bundles. The ends of CNTs are domed structures of six-membered rings, capped by a five-membered ring. Generally speaking, there are two types of CNTs: single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). As their names imply, SWNTs consist of a single, cylindrical graphene layer, whereas MWNTs consist of multiple graphene layers telescoped about one another.
The Unique Properties of Carbon Nanotubes

Carbon nanotubes (CNTs) were first isolated and characterized by Ijima in 1991. Since then, dozens of research articles have been published, and new applications for CNTs have been proposed every year. The unique physical and chemical properties of CNTs, such as structural rigidity and flexibility continue to generate considerable interest. Additionally, CNTs are extremely strong, about 100 times stronger (stress resistant) than steel at one-sixth the weight. CNTs can also act as either conductors or semiconductors depending on their chirality, possess an intrinsic superconductivity, are ideal thermal conductors, and can also behave as field emitters.
Carbon Nanotube-Based Nanodevices

Carbon nanotubes are a hot research area at the moment. The excitement has been fuelled by experimental breakthroughs that have led to realistic possibilities of using them commercially. Applications could include field emission-based flat panel displays, novel semiconducting devices, chemical sensors, and ultra-sensitive electromechanical sensors.
Carbon Nanotubes Used in Molecular Electronics

The utility of carbon nanotubes for molecular electronics or computers, first predicted by theory and simulations, is now being explored through experiments to fabricate and conceptualize new devices based on simulations. Carbon nanotubes are now the top candidate to replace silicon when current chip features cannot be made any smaller in 10-15 years’ time.
Semiconducting Properties of Carbon Nanotubes

Calculations show that nanotubes can have metallic or variable semiconducting properties with energy gaps ranging from a few meV to a few tenths of an eV. Experiments probing the density of states confirm these predictions. Conductivity measurements on single nanotubes have shown rectification effects for some nanotubes and ohmic conductance for others. These properties suggest that nanotubes could lead to a new generation of electronic devices.
Using Carbon Nanotubes as Electromechanical Sensors

Simulations to investigate the interaction of water molecules with a nanotube tip revealed an atomistic understanding of the interaction, which is critical in designing commercial-quality flat panel displays around carbon nanotubes. Their use as ultra-sensitive electromechanical sensors has also been explored.

Background

European Directives on Recycling and Hazardous Substances

The European Union (EU) has introduced legislation on electrical and electronic equipment in relation to its composition and the levels to which it should be recycled. This legislation has its origin in the EU Directives relating to Waste Electrical and Electronic Equipment (WEEE) and to the Restriction of Hazardous Substances (RoHS) in new products. Manufacturers will need to ensure that their products (and their components) comply in order to sell in the European market. If they do not comply, they will need to redesign their products.

Another EU directive, End-of Life Vehicles (ELV), aims to reduce, or prevent, the amount of waste produced from ELVs and increase the recovery and recycling of materials or components. The ELV Directive banned lead, cadmium, mercury and hexavalent chromium from products, with some exemptions, from 1 July 2002. The RoHS Directive will ban the placing on the EU market of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants from 1 July 2006. The limits for these substances required by both directives are given in Table 1.

Table 1. Limits for RoHS and ELV directives.

Element	Limit
Pb, Hg, Cr6+, PBB*, PBDE*	0.1wt%
Cd	0.01wt%

Note: *only for RoHS directive

Directives on Materials Recycling in the Rest of the World

In other parts of the world similar directives are being introduced including electronic waste recycling legislation in the USA, often referred to as California RoHS, and the adoption of RoHS in China. Given the rigorous demands of such legislation, X-ray fluorescence spectroscopy (XRF) has emerged as the optimal solution for elemental analysis of heavy metals in a wide variety of materials, including brass.

Analysis of Cadmium and Lead in Brass

This note demonstrates the capability of the Epsilon 5 energy-dispersive XRF spectrometer for the analysis of Cd and Pb in bulk brass samples. In addition, results are presented for the analysis of Cd in brass samples of various shapes and sizes, since such samples are likely to be encountered when analyzing product sub-assemblies.

Measurement Criteria

Measurement criteria The application was set up and calibrated using five brass certified reference materials (MH1 to 5) from MBH Analytical Ltd (UK). The measurement conditions are given in Table 2.

Table 2. Analytical parameters used for the application set-up. *This is the maximum current; for each measurement the current is adjusted to obtain maximum 50% detector dead-time.

Element	Secondary Target	Measurement live time (s)	kV	mA*
Cd	CsI	300	100	6
Pb	Zr	300	100	6

Accuracy

Figures 1 and 2 show calibration curves for Cd and Pb in brass samples and a summary of the calibration data is given in Table 3. These data show a good correlation between the certified concentrations and the measured intensities. The calibration RMS indicates the accuracy of the method. It is a statistical comparison (1 sigma) of the certified chemical concentrations of the standards with the concentrations calculated by the regression in the calibration procedure. In addition, a certified reference material (BNF C48.06) was analyzed as an unknown sample. A comparison of the certified and measured values for Cd and Pb is shown in Table 4.

Figure 1. Calibration curve for Cd in brass.

Figure 2. Calibration curve for Pb in brass.

Table 3. Calibration details.

Element	Cd	Pb
Concentration Range (wt%)	0.0012-0.026	0.0065-0.33
RMS (wt%)	0.0006	0.0072
Correlation coefficient	0.9988	0.9989

Table 4. Results of the analysis of CRM BNF C48.06 as unknown sample.

Element	Cd	Pb
Certified (wt%)	0.008	0.025
Measured (wt%)	00.0078	0.024

Precision and Instrument Stability

CRM BNF C48.06 was measured 20 times consecutively in a single day to show the repeatability of the Epsilon 5. The reproducibility was determined by measuring the same sample once per day over a 10-day period. The repeatability and reproducibility data are shown in Table 5. No drift correction was applied during the precision studies.

Table 5. Repeatability (20 measurements consecutively) and reproducibility (10 measurements over 10 days)

Element	Cd	Pb
Repeatabaility
Mean wt%	0.0077	0.024
RMS	0.00001	0.0016
RMS rel%	1.73	6.43
Reproducibility
Mean wt%	0.0077	0.024
RMS	0.0002	0.0014
RMS rel%	1.95	5.86
CSE
CSE rel%	1.08	3.02

The repeatability and reproducibility are both excellent and are nearly identical. Comparison of the relative RMS values with the counting statistical error (theoretically, the minimum possible error) shows the excellent precision of both the instrument and the method.

Detection Limits

The detection limits for Cd and Pb in brass are given in Table 6 and are based on 100 seconds live time measurement. The higher detection limit for Pb is caused by the very strong absorption of the Pb fluorescent line by the two major elements in brass, Cu and Zn. The LLD’s are calculated from:

Where:

s = sensitivity (cps/ppm)
r_b = background count rate (cps)
t_b = live time (s)

Table 6. Detection limits.

Element	Cd	Pb
LLD (100s)	3.5ppm	30ppm

Analysis of Cd in Brass Samples of Various Shape and Size

It is possible to measure small irregular shaped samples (samples that do not cover the complete opening diameter of the sample cup) by setting up a calibration using the Raleigh line of the secondary target as ratio channel. The intensity of this line has proven to be proportional to the sample size (area) and can thus be used to correct for variations in intensity due to differences in size. For the analysis the small samples were put in a P2 liquid cup in which the sample was fixed between two thin foils (e.g. polypropylene). The samples illustrated in Figure 3 were measured as unknowns and the results are shown in Table 6. A comparison of these results with the results obtained from a subsequent ICP analysis of the samples, shows that there is a very close agreement between the XRF (Epsilon 5) and ICP techniques.

Table 6. Results for the analysis of Cd in brass samples of various size and shape.

Sample Weight (mg)	Cd (ppm) E5 results	Cd (ppm) ICP result
987	71	70
213	37	40
59	66	68
64	67	68

Background

Bronzes are copper-based alloys. Major alloying elements are often, but not always, zinc and tin. They offer a combination of properties such as high strength, hardness, corrosion resistance and wear resistance. Phosphor Bronzes Phosphor Bronzes are alloys of Copper and Tin. PB102 has good corrosion resistance and is known for its high fatigue strength. It also shows a good combination of strength and ductility. Alloy PB102 Bronze alloy PB102 is a Phosphor Bronze. Along with the very similar alloy C51800, PB102 is the most widely used of the wrought phosphor bronzes.

Chemical Composition

Table 1. Typical chemical composition for bronze alloy PB102 % PB102 Cu 95 Pb - Sn 5 Fe - Al - Mn - Zn - Si - Ni -

Properties

Mechanical Properties Table 2. Typical mechanical properties for bronze alloy PB102 Half Hard Properties PB102 Tensile Strength (MPa) 650 Proof Stress 0.2% (MPa) 560 Elongation A5 (%) 3 Hardness VPN 210-240 Physical Properties Table 3. Typical physical properties for bronze alloy PB102 Property Value Density 8.85 g/cm3 Melting Point 930°C Modulus of Elasticity 121 GPa Electrical Resistivity 0.096x10-6 Ω.m Thermal Conductivity 63 W/m.K at 20°C Alloy Designations Bronze alloy PB102 corresponds to the following designations: CEN BS UNS ISO CW451K PB102 C51000 CuSn5 Corrosion Resistance Alloy PB102 has good corrosion resistance, almost equivalent to that displayed by the Aluminium Bronzes. Fabrication Cold Working Cold working response of PB102 is excellent. Hot Working Hot formability of PB102 is poor. Heat Treatment Solution treatment or annealing of PB102 can be done by rapid cooling after heating to 500-700°C. Machinability The machinability rating of PB102 is rated as poor at 20 compared to Alloy 360 FC Brass which is rated as 100. Welding and Joining · Soldering, brazing and butt welding of PB102 are rated as “excellent”. · Oxyacetylene welding, seam welding and coated metal arc welding are rated as “fair”. · Spot welding and gas shielded arc welding are rated as “good”. Applications PB102 is typically used in: · Gears · Worm Gears · Bushes · Marine applications · Aircraft applications · Chemical applications · Springs

Background

Bronzes are copper-based alloys. Major alloying elements are often, but not always, zinc and tin. They offer a combination of properties such as high strength, hardness, corrosion resistance and wear resistance. Aluminium Bronzes Copper-Aluminium alloys are commonly known as Aluminium Bronzes. These alloys cover a range of copper-based alloys in which the primary alloying element is up to 14% aluminium. The four major groups of Aluminium Bronze are: · Single phase alloys containing less than 8% Aluminium. · Two-phase or duplex alloys containing 8 to 11% Aluminium. These alloys also frequently have additions of Iron and Nickel to increase strength. This group contains casting alloys AB1 and AB2, the wrought alloys CA105, CA104 and Naval Engineering Standard (NES) alloys (NES 747 when cast and the wrought form NES 833). · The low magnetic permeability Aluminium Silicon alloys. · The Copper Manganese Aluminium alloys with good castability. Alloy NES833 Alloy NES833 is an Aluminium Bronze with good ductility and impact strength. It also has superior corrosion resistance.

Chemical Composition

Table 1. Typical chemical composition for bronze alloy NES833 % NES833 Cu 82 Pb - Sn - Fe 4.2 Al 9.3 Mn 0.3 Zn - Si - Ni 4.2

Properties

Mechanical Properties Table 2. Typical mechanical properties for bronze alloy NES833 Grade NES833 Tensile Strength (MPa) 635 Proof Stress 0.2% (MPa) 295 Elongation A5 (%) 17 Hardness HB 150 Physical Properties Table 3. Typical physical properties for bronze alloy NES833 Property Value Density 7.5 g/cm3 Electrical Resistivity 0.172x10-6 Ω.m Thermal Conductivity 42 W/m.K at 20°C Alloy Designations Bronze alloy NES833 corresponds to the following designations: European British Proprietary CW307G DGS1043 Hidurax Corrosion Resistance NES833 has high corrosion resistance, particularly in marine environments. Alloy NES833 is immune to chloride stress corrosion cracking. This alloy also has excellent resistance to cavitation erosion. Temperature Resistance Bronze alloy NES833 largely retains its strength and hardness up to 400°C. It is also resistant to high temperature scaling at up to 1000°C. Fabrication Welding and Joining Bronze alloy NES833 is fully weldable by common welding methods. Machinability NES833 has good machinability. Applications Aluminium bronze NES833 is typically used in: · Marine Valves · Pumps · Weapons handling systems · Couplings · Fasteners · Gears · Marine propeller shafts