Determining size of nanosized specimens

1.XRD: Take X-ray diffraction spectrum of the specimen material. Using De bye-Schrrer formula, You can easily fix the exact size of the nano grains.
2.TEM: Take transmission electron micrograph to get an accurate grain size value. TEM equipment far expensive than XRD.
3. SEM: Rough idea can be inferred from scanning electron micrograph.

Nanocomposites

nanoparticles treated with conducting polymers(polyaniline,polypyroll etc.) gives superlative properties.

Nuclear magnetic resonance

At first glance, it seems odd that the neutron, with no net charge, has a spin magnetic moment. But if we assume that the neutrons contain equal amounts of positive and negative charges, a spin magnetic moment could arise even with no net charge.

Let E₀ be the energy of the nucleus. When the nucleus is in a constant magnetic field B, magnetic moment of protons interacts with magnetic field B and the energy of interaction is given by µ_pB. As a result, the energy level E0 splits into two components E₀+µ_pB and E₀-µ_pB.

At this stage, magnetic moment vector M of the nucleus makes precession around the magnetic field direction. This precision is called Larmour precision. Larmour frequency for protons,

n_L=ΔE/h=2µ_pB/h

If an electromagnetic radiation of frequency n_L is now incident on the sample, the nuclei will receive the energy to flip their spins and reach the higher state. This phenomenon is called nuclear magnetic resonance (NMR). Radio frequency range electromagnetic radiations are used here.

Experimental method for the detection of NMR

The specimen material is taken in a glass vessel and placed between the pole pieces of the magnet. The magnetic field acting between the pole pieces can be varied by changing the current through the sweep coil. Radio frequency generator supplies Radio frequency electromagnetic radiations to the specimen through Radio frequency coil wound round the specimen. At the same time Radio frequency generator supplies the signal to the external circuit which measures the power absorbed by the specimen. At resonance, the specimen absorbs energy from electromagnetic radiation and hence there occurs a drop in its amplitude. The absorption signal is amplified by the amplifier and finally displayed on a CRO.

Applications of NMR

1. To study the molecular structure.
2. In chemical structure analysis of materials.
3. In the study of chemical reactions.
4. To study the internal and local electric fields in an alloy.
5. In the study of diffusion co-efficient.
6. For measuring nuclear magnetic moment.
7. For measuring magnetic field.

Synthesis of Fine Particles of Zinc Ferrite

Synthesis of nanoparticles in very fine form is a difficult task and various researchers all over the world are trying their level best in this field to develop nanoparticles in the fine and pure form. Zinc ferrite is an antiferromagnetic material with good electrical and magnetic properties which can be utilised for several applications such as transformer cores, dielectric etc. For the synthesis of zinc ferrite, starting precursors are zinc oxide and iron oxide. These two starting materials are taken in the weight ratio 1:2 in a agate mortar and mixed with the help of toluene for 30 minutes. Now heat the material at around 500 Kelvin and then allow it to cool. This process(Mixing-heating-cooling) repeat for 3 times. Now the powder sample is put in the vial of high energy ball milling unit and milled for 60 minutes. The powder is now taken from the milling unit and mix a small amount of water and make it in the paste form. This paste is taken in a crucible and heated to 750 Kelvin in a furnace. This will yield very fine particles of zinc ferrite.

Alloying elements for steel

The melting point of aluminium metal is above 1000 Kelvin. By virtue of its strong deoxidizer power, it is less susceptible to strain ageing. Alloying with Boron can be done for increasing core hardness in constructional steels. Beryllium is a best choice for the manufacture of coil springs for watches which are antimagnetic. Chromium is a superlative material for steel alloying because it yields corrosion resistant and wear resisting alloys. Manganese is another choice in alloying of steel and resultant compound is showing excellent forging and welding properties. Nickel positively modifies the notch-impact value of structural steels. Since Sulphur is very much harmful and hazardous, it is always better to avoid it in alloying with steel. Silicon steels show superlative electromagnetic properties.

Duroplastics

The most common examples of duroplastics are Bakelite and textolite. They are nothing but resins made of chemical phenol formaldehyde. The properties can be fine controlled appreciably in these materials by the optimal usage of filler materials. Phenolic fabric-filled laminates are current choice and is used for the construction of low cost, thin stamped gears or punched parts. For changing colour and altering pastel shades, we use urea aldehydes. High values of dielectric strength and resistance of melamine aldehydes makes it best candidate for the construction of moulded electrical parts. Aniline aldehyde is another alternative with exceptional mechanical, electrical and chemical properties. For the usage in housings, containers and ducts epoxy-glass can be preferred. Polyester-glass, acetal, silicone and synthetic rubbers are some other examples of duroplastics.

Nanoparticles of magnesium cobalt ferrites

Take Manganese nitrate, cobalt nitrate and ferric nitrate in the weight ratio 1:1:1. Dissolve in distilled water and make it a rich paste. Keep this paste in a oven and heat it to 400 Kelvin temperature. Dried sample crush using agate mortar till it becomes fine powder. Keep this powder in a bowl of high energy ball milling unit. Mill it for more than 5 hours with a minimum of 500 rotations per minute speed. Resulting powder is the fine form of nanoparticles of magnesium cobalt ferrites.

Zinc Ferrite

Zinc ferrites (ZnFe2O4) prepared in the micron regime is purported to be a normal spinel with no net magnetization. Recent investigations carried out by various researchers clearly shows that, contrary to the earlier belief, it is not a normal spinel, and exhibits a net magnetization when they are prepared in the form of fine particles. This is possible if Zn2+ occupies octahedral sites (B), which results in a magnetic interaction. Various other hypotheses also exists and if this is to tested, a systematic study on similar compounds is to be undertaken.

How to synthesize nanomagnetic fluid

Using agate mortar, crush Chloride crystals of two metals, say cobalt chloride and iron chloride into fine powder. Put the fine crystals in a beaker and add distilled water so that we obtain a concentrated solution. Using high energy ball milling apparatus, ball mill it for 2 hours in a 650 rotations per minute speed. Add potassium hydroxide solution until it become brown. If it is not becoming brown, add a few drops of concentrated sodium hydroxide. The solution is subjected to heating till it boils. Let it remain there for 2 minutes. Ball milling shall repeated to 3 hours in a 600 rpm speed now. Filter the liquid and residue be dried using oven. Dried samples are heated to 773 K using a quality furnace. Put water, oleic acid and paraffin liquid in equal amount and ball mill it for 10 hours in a relatively low rpm (250 rpm enough). The resultant fluid is nanomagnetic and very much useful.

Compounding (Staging) of Impulse Turbine

In an impulse turbine, the steam expands completely in one stage (i.e., the entire pressure drop from high pressure to low pressure takes place in only one set of nozzles). As a result, the rotor rotates at a very high speed of about 30,000 rpm (K.E. is fully absorbed). This high speed poses number of technical difficulties like destruction of machine by the large centrifugal forces developed, increase in vibrations, quick overheating of bearings, impossibility of direct coupling to other machines, etc. To reduce the speed, reduction gearing is not preferable because of large and bulky construction. Hence a method of reducing the speed of the turbine is adopted. To overcome the above difficulties, the expansion of steam is performed in several stages. A number of successive stages are usually arranged one behind the other such that the expansion of steam would perform in several stages. Utilization of the high pressure energy of the steam by expanding it in successive stages is called Compounding (Staging).