Thin Films High Pressure Laboratories High-Temperature Laboratories Optical Laboratory
X-Ray Laboratories Central facilities
Chemical Laboratories
The chemistry-lab is able to analyze quantitatively the bulk chemical compositions of any inorganic solid material; e.g. rocks, ores, soils, cements, glasses, metals and alloys, technical products. Special requirements for the samples are given below. Only the inorganic part of fluids can be detected.
Please note: All methods are destructive to the sample!!
X-Ray fluorescence spectroscopy (XRF) - PHILIPS PW 2404
Elements to be detected: all elements with Z > 9 (fluorine) except the nobel gases requirements: the mass of the sample should exceed approximately 1 gram.
Atomic emission spectroscopy with inductively coupled plasma (ICP-OES) - UNICAM PU 7000
Elements to be detected: all elements with Z > 4 (beryllium) requirements: the sample must be soluble in an anorganic solvent, the mass must exceed 1 mg (depends on the number of elements to be analyzed).
Atomic absorption spectroscopy (AAS) - VARIAN AA 300
Elements to be analyzed: all elements with Z > 3 (lithium) requirements: the sample must be soluble in an anorganic solvent, the mass must exceed 1 mg (depends on the number of elements to be analyzed) Coulometric analyses of Carbon, Carbondioxide, Sulfur, and H2O (in minerals as hydroxyl groups or as H2O, moisture) requirements: mass should exceed 10 mg/analysis (depends on the content) Potentiometric determination of fluorine and Fe2+requirements: mass should exceed 50 mg/analysis (depends on the content) Determination of loss on ignition (l.o.i.).
Contact: Thomas Fockenberg
Thin Films
Producing thin films of complex refractory materials such as silicates and oxides was not possible until recently. Advances in the techniques of pulsed Laser ablation using an excimer Laser have now made it possible to produce such thin films, which enable a variety of diffusion and other kinetic studies to be carried out. A laboratory for the production of such thin films is now in place at the Institute of Geology, Mineralogy and Geophysics of the Ruhr-University at Bochum now. This is the first equipment of this kind dedicated to mineralogical studies.
The equipment, built to suit our special needs, consist of an excimer Laser capable of operating at three wavelengths (ArF - 193nm, KrF - 248nm and XeF 351nm). This laser is powerful enough (pulse energies of 650 to 1200mJ, maxium wattage of upto 50 and a frequency of 50 Hz) to convert refractory minerals [targets] stoichiometrically to a plasma. The plasma then deposits the material on the surface of a second solid object [substrate], which is typically the polished/cleaved surface of a mineral or rock. The high energy ensures tight bonding between the deposited thin film and the substrate, thereby producing excellent starting materials for diffusion and other kinetic studies.
Among the many advantages of this method are the speed and versatility with which a wide range of chemistry can be handled. We have so far produced, for example, thin films of olivines, garnets, pyroxenes, feldspars, perovskites and various ocides of complex chemistry, similar to those found in nature.
Related Publications:
Dohmen, R., Becker, H.-W., Meißner, E., Etzel, T., and Chakraborty, S. (2002) Production of silicate thin films using pulsed laser deposition (PLD) and applications to studies in mineral kinetics, Eur. J. Mineral., vol. 14, pp. 1155-1168.
Contact: Sumit Chakraborty and Ralf Dohmen
High Pressure Laboratories
The well equipped High Pressure Laboratories of the Mineralogy Section of the Institute of Geology, Mineralogy and Geophysics comprise of several units:
the Hydothermal Autoclave laboratory
About 30 autoclaves, where high pressure is obtained by pumping water into narrow capillaries, make up the hydrothermal laboratory. These are heated externally in a furnace.
Pressures of upto 7 kbar and temperatures of upto 800 üC can be obtained using these equipments.
The main advantage of this kind of equipment is in the large sample volumes that can be obtained, relatively more hydrostatic pressure (compared to solid-media apparatus)and long run durations of months, during which stable pressure and temperature conditions can be maintained.
Contact: Thomas.Mueller-1@rub.de
the piston-cylinder laboratory
4 presses make up the piston-cylinder laboratory. High pressure is obtained in these equipments by compressing specially designed solid-media high pressure cells. Pressures of up to 60 Kbar and Temperatures of up to 1600 °C can be achieved in this kind of equipment. The capabilities will extend considerably through the installation of the new "Walker Module", which will allow pressures as high as 100 Kbar to be obtained.
Two of the presses have completely computerized pressure and temperature controllers, which can be used to carry out experiments along pre-defined P-T paths. Pressure and Temperature conditions can thus be held at defined conditions for long durations without the need for manual intervention. One of the presses has additional facilities to monitor the piston displacement, which allows compressibility measurements to be carried out at high pressures. Samples of upto 200 mg can be used for experiments up to 50 kbar, at higher pressures only small samples of about 10 mg can be used.
Between them, experiments can be carried out over a wide range of pressures (upto 100 kbar) and temperatures (upto 1600° C).
Contact: Thomas Fockenberg
High-Temperature Laboratories
The Mineralogy Section of the Institute of Geology, Mineralogy and Geophysics has a number of high-temperature furnace labs where experiments can be carried out at temperature up to 1800° C. Available facilities include:
vacuum furnaces
controlled athmosphere furnaces (defined by flowing gas mixtures)
ffurnaces with multiple heating zones
furnaces dedicated to crystal growth, e. g. Czochralski-method
ddifferential thermal analysis
Contact: Sumit Chakraborty and Ralf Dohmen
Optical Laboratory
Optical Properties
The optical properties of solids (minerals, synthetic crystals) are very sensitive physical parameters and can be used to reveal petrological and crystallographic processes as well as technical problems.
Two different kinds of high precision measurements are routinely applied in our department:
Spindle stage technique for determination of refractive indices: An advanced spindle stage to determine the indices of refraction and the optical angle (2V) has been constructed in our department. For the refractive index measurement, the index of a liquid, whose index matches exactly with that of the unknown crystal, is determined using an internal refractometer. This method thus avoids all external sources of error and the precision of measurements can be increased to ü 0.0003 for n.
Minimum deviation method for determination of optical dispersion: This classical method for the determination of the dispersion of the indices of refraction normally requires large samples, which are not always available for all materials. The development of an elaborate technique in our department permits the preparation of prisms from minute crystals. In some cases, optical dispersion in samples as small as 500 üm could be measured.
Minimum deviation method for determination of optical dispersion: This classical method for the determination of the dispersion of the indices of refraction normally requires large samples, which are not always available for all materials. The development of an elaborate technique in our department permits the preparation of prisms from minute crystals. In some cases, optical dispersion in samples as small as 500 üm could be measured.
Contact: Ralf Dohmen and Olaf Medenbach
X-Ray Laboratories
The Xray labs in the Mineralogy section are equipped with a number of equipments for the identification and structure analysis of crystalline materials. The following provides a brief overview of the available facilities.