Laser diffractometers

First, a defined amount of compact, well-stabilized particles (jc 100 pm) are measured with the laser diffractometer. Afterwards, a defined amount of the suspension in question is added to the reference system. The amount of agglomerates is reflected by the mixing ratio found by the analysis. In the case of compact particles, the mixing ratio will not be affected by disagglomeration, but for filmed powders it will. The method is reproducible and detects quality differences between particles. 

Washington (1992) has discussed the concepts and techniques of particle size analysis and its role in pharmaceutical sciences and other industries. There are many different methods available for particle size analysis. The techniques most readily available include sieving, optical microscopy in conjunction with image analysis, electron microscopy, the Coulter Counter and laser diffractometers. Size characterization is simple for spherical particles, but not for irregular particles where the assigned size will depend on the method of characterization used. Table 6.2 lists particle size measurement methods commonly used and the corresponding approximate useful size range (Mullin 1993). 

For quite a while, the most useful method for determining particle distributions was that of electrical conductivity. The most widely used instrument is the Coulter Counter (named after the Inventors), although there are now other similar instruments on the market. It has largely been supplanted by the Laser-Diffractometer. Originally, the Coulter-Counter was designed to measure blood corpuscles which are 2-8 p in size. It has proven to be very suited to measure micron and submicron particles easily, accurately, and reproducibly. Consider a conductive solution consisting of water with a soluble salt, i.e.- 1% NaCl, and a... 

Particle size distribution analysis was performed using a laser diffractometer (Mastersizer 2000, Malvern Instmments). The film samples (com starch, fir tree needles, and beech wood lignin, respectively) were diluted in water (concentration of 0.05 %) at 2000 rpm until an obscuration rate of 12.06 % was obtained. Three samples were measured in quintuplicate. The Mie theory was applied by considering the following optical properties R1 for starch of 1.527, and RI for lignocel-lulose of 1.36, respectively, and absorption of 0.001. 

Aerosols can be analysed using techniques that are based on the interactions between particles and light The examination of a scattered beam of light by a detector after hitting a particle is the basis for many optical instruments. For example, the number of scattered light pulses is a measure of particle number. Furthermore, the intensity and spatial scattering pattern can also be used for determination of particle size and particle shape, respectively. Optical methods are sensitive and easy to use. These methods are classified into four categories (1) optical particle counter, (2) laser diffractometer, (3) phase Doppler system and (4) intensity deconvolution system. 

The particle size distribution of South Afriea Coneentrate was measured using the laser diffractometer MS 2000 which is produced by Malvern Instruments. The moisture eapacity of raw material was measured in the self-made instrument in the laboratory. [5-6]The morphology of the particle surface were performed using scanning electron microscope (SEM) equipped with a tungsten filament emission source. 

Figure 6. Plan of the target preparation facilities consisting of UHV preparation chamber (a), (reactive) ion etching chamber (b), ion etching gun (c), laser (d), photon detector (e), transfer arms (f), Auger system for surface analysis (g), sample manipulator and annealing facility (h), load lock and optical microscope for viewing sample (i), evaporator (j), transmission diffractometer (k), and vacuum tank for main spectrometer (1).

Most of the routine work in structural analysis is performed with D5000 Siemens diffractometer equipped with a Gobel mirror and an energy-dispersive detector. Raman micro-spectrometry has been recently introduced with a Labram infinity spectrometer with two laser sources, fitted with a horizontal output adapted to the investigation of vertical items like paintings or statues. For the most fine structural investigations, experiments are conducted with EXAFS, XANES or diffraction lines from various synchrotron facilities (ESRF at Grenoble, BESSY at Berlin, LURE at Paris). 

Laser Raman spectroscopy (LRS) measurements were performed on a Spex Ramalog 1403 spectrometer described in detail elsewhere (23). Powder diffraction measurements were obtained with a Siemens D-500 diffractometer at a scan rate of l°/min using monochromatic Cu-Ka radiation. 

Compounds 5,6,7, and 8 are liquids at room temperature and a low temperature in situ crystallization was performed on the diffractometer using a miniature zone melting procedure with focused infrared light or C02 laser beam [/]. All bond lengths given are corrected for libration [54]. 

We used SIEMENS D 5005 X-ray Diffractometer to investigate crystal structure and quality. PL spectrum was measured by 325 nm He-Cd laser. The PL signals from the sample were filtered by a monochromator and picked up computer. X-ray photoemission spectra (XPS) were performed on ESCALAB Mark II X-ray photoemission spectrometer. 

Figure 14 An experimental setting for single-crystal X-ray diffraction study at 30 K, showing a Bruker three-circle diffractometer with a SMART 1000 CCD area detector, a laser device for crystal irradiation and a HehX open flow helium cryostat in action...

This is not a method commonly used for coordination compounds, which do not often melt without decomposition. Where applicable, it can be used by cooling from a high-temperature melt to room temperature, or by cooling a room-temperature liquid to a lower temperature. The latter is a specialized technique, usually carried out in situ on a diffractometer, with monitoring of the crystal growth by optical and X-ray methods the sample is contained in a sealed capillary tube, and selective heating may be applied by an infra-red laser to develop a single crystal. Twins and multiple crystals often result from these methods. 

Precursors and catalysts were characterized in ambient conditions by X-ray diffraction (XRD) on a Rigaku Powder Diffractometer using CuK radiation with a Ni filter. LiF was used as an internal standard for the activated catalysts. Laser Raman spectra (LRS) were collected using Ar ion laser excitation (514.5 nm) at a power of 25 mW at the sample. Spectra for the precursors were collected in ambient conditions, and reaction-used catalysts were characterized in-situ at 400°C in a 70 ml/min flow of C4H,(/02/He (0.99/10.2/88.81). Phosphorus to vanadium ratios (molar) were determined by inductively coupled plasma (ICP). Diffuse reflectance spectra (DRS) were collected in ambient conditions using polytetrafluoroethylene as a reference. 

Electroluminescence was excited by v oltage i mposed to the ELT samples by stripe contacts. Photoluminescence (PL) and lasing were excited at T=18-500 K by the radiation of a N2 laser ( A v = 3.68 eV, /= 1 kHz, Tp = 8 ns) and a CW HeCd laser (Av=3.81 eV). The X-ray diffraction was measured with a Philips X Pert Materials Research Diffractometer. The system uses CuX radiation and a four-crystal Ge monochromator in the (220) setting. It is also equipped with an X-ray mirror in order to increase the intensity of the primary beam. The beam size was limited to 1.4x3 mm, co - 20 scans were performed using a triple bounce Ge (220) analyser. 

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