ion, ion- +
(Greek: ion, "going"; neuter present participle of ienai, "to go"; because an ion moves toward the electrode of an opposite charge)
Static electric fields cannot separate ions by their mass but do separate them by their energy and so provide an important design element by functioning as an energy filter.
The beam removes atoms from the workpiece by transferring energy and momentum to atoms on the surface of the object.
When an atom strikes a cluster of atoms on the workpiece, it dislodges between 0.1 and 10 atoms from the workpiece material.
Ion-beam machining, IBM, permits the accurate machining of virtually any material and is used in the semiconductor industry and in the manufacture of aspheric lenses.
The technique is also used for texturing surfaces to enhance bonding, for producing atomically clean surfaces on devices; such as, laser mirrors, and for modifying the thickness of thin films and membranes.
2. A process in which bombardment of a solid with a beam of energetic ions causes the intermixing of atoms of two separate phases originally present in the near-surface region.
2. The process by which the mass spectrum of an ion beam is analyzed, generally by altering the electric or magnetic fields or by moving a probe in a mass spectrometer.
2. A device for detecting and measuring the mass distribution of ions orbiting in an applied magnetic field, either by applying a constant radio-frequency signal and varying the magnetic field to bring ion frequencies equal to the applied radio frequency sequentially into resonance, or by rapidly varying the radio frequency and applying Fourier transform techniques (an operation that transforms one complex-valued function of a real variable into another one).
Fourier transform techniques as used in electronics, control systems engineering, and statistics, is a term used to describe the analysis of mathematical functions or signals with respect to frequency, rather than time.
2. A chromatographic procedure in which the stationary phase consists of ion-exchange resins which may be acidic or basic.
3. The process of separating and analyzing different substances according to their affinities for chemically stable but very reactive synthetic exchanges, which are composed largely of polystyrene cellulose.
The process uses an absorbent containing ionizing groups and accommodates the exchange of ions between a solution of substance to be analyzed and the absorbent.
Ion exchange chromatography is often used to separate components of nucleic acids and proteins elaborated by various structures throughout the body.
Different ions deposited in the absorbent during the exchange produce bands of different colors, which constitute a chromatograph.
Operation is at atmospheric pressure and room temperature.
2. Synthetic organic substances of high molecular weight which are used to replace certain negative or positive ions that they encounter in solutions.
3. A polymeric resin that contains electrically charged fragments (fixed ions) permanently attached to the polymer backbone, electrical neutrality is achieved by attached mobile "counterions" in the solution phase the resin is immersed into.
A practical use of such resin is the removal of unwanted ions from a solution by replacing them with other ions; for example, a cation exchange resin containing fixed negative charges with attached mobile sodium ions can be used to remove "hardness" from water if the calcium and magnesium ions are more strongly attracted to the resin and therefore will replace the sodium ions.
Eventually all the sodium ions will go into solution and the ion-exchange process terminates; then, resin can be regenerated by soaking in a high concentration sodium salt solution.
Such a process can also be used to remove unwanted ions from polluted water streams.
More about ion-exchange resins
When immersed in a solution, the resins absorb the solution and swell; the degree of swelling is dependent on the polymeric structure and the total ion concentration of the solution.
Ion-exchange resins are light and porous solids, usually prepared in the form of granules, beads, or sheets.
Resins of suitable chemical compositions and physical properties may be synthesized at will for specific ion-exchange applications; thus, they comprise the bulk of synthetic ion-exchange materials used in the laboratory and industry.
In industrial and domestic applications, ion-exchange resins are used for the removal of calcium, magnesium, iron, and manganese salts from water (water softening), for purification of sugar, and for concentration of valuable elements; such as, gold, silver, and uranium from mineral ores.
In chemical analysis, ion-exchange resins are used for the separation or concentration of ionic substances, and in chemical synthesis, some ion-exchange resins have been used as effective catalysts, notably in esterification and hydrolysis reactions.
Types of ion-exchange resins
Two separate types of resins are commonly classed as ion-exchange resins, although their functions do not involve an interchange of ions.
These are the chelating resins and the electron-exchange resins.
- Chelating resins are styrene-divinylbenzene polymers to which iminodiacetate groups are introduced. This functional group forms complexes with all the metallic elements except the alkali metals, with stabilities that vary with the different metals; in analytical chemistry, they are used for the separation of trace amounts of metals.
- Electron-exchange resins accept or donate electrons to the surrounding solution and are used in oxidation-reduction reactions; examples include polymers prepared from hydroquinone, phenol, and formaldehyde.
2. Occurring in the form of an ion or ions.
3. A type of chemical bonding in which one or more electrons are transferred completely from one atom to another, and so converting the neutral atoms into electrically charged ions.
These ions are approximately spherical and attract one another because of their opposite charge.
2. A transmembrane protein structure that forms an aqueous pore that allows only certain ion species to pass through the membrane.
2. The charge of an electron; the charge of any ion is equal to this electron charge in magnitude, or is an integral multiple of it.
2. The contribution of a given type of ion to the total equivalent conductance in the limit of infinite dilution.