Analysing the composition of glass is important in industry and academia. It is important to have quantitative knowledge of the analysis method's precision. This allows the use of statistical methods to calculate the number of samples that should be measured to be sure of drawing a conclusion with an acceptably low risk of being incorrect. Calculating the appropriate number of samples in advance avoids the time and costs associated with either unnecessary or insufficient sampling. In the present study a statistical approach, Gage repeatability and reproducibility (Gage R&R), has been applied to two techniques for measuring boron in glass: induction-coupled plasma optical emissions spectroscopy (ICP-OES) and electron probe microscopic analysis (EPMA); to quantify and compare their precision, and identify the different sources of measurement system variation. Information has also been obtained on the measurement systems' accuracy. The precision of both methods was found to be acceptable for typical glass analysis situations, although the precision of the EPMA method was significantly lower than the ICP-OES method (95% confidence). The number of replicate measurements needed in order to reliably detect a difference of 0.5% B2O3 is practical for most situations: three replicates for the ICP-OES method and six replicates for the EPMA method. Measurement system variation in the ICP-OES technique was found to be primarily due to repeatability rather than reproducibility. The EPMA method was found to have bias and linearity issues. It was concluded that the ICP-OES method has acceptable precision, and the EPMA method has been shown to be a viable alternative provided steps are taken to correct the bias and linearity. The information obtained on the precision of both measurement systems allows better data driven decision-making through the use of appropriate sample sizes.
The recycling of glass from obsolete cathode ray tubes (CRT) has hitherto only occurred to a very limited extent, but the production of foam glass used as an insulation material component has recently been proposed as a promising recycling method. CRT panel glass has high recycling potential due to its non-hazardous composition. Here we report on the foaming of CRT panel glass using Na2CO3 as the foaming agent. We explore how heat treatment temperature and concentration of Na2CO3 affect the density and porosity of the foam glasses, and whether Na2O is incorporated in the glass network. The optimum foaming temperature for minimising density and maximising closed porosity is found to be between 1023 and 1123 K. The pore structure depends on the amount of added Na2CO3, viz, the pores generally become more open with increasing Na2CO3 content. A minimum density of 0.28 g/cm(3) is found when 14 wt% Na2CO3 is added and the heat treatment temperature is 1023 K. Interestingly, the glass transition temperature (T-g) of the final foam glass decreases linearly with increasing [Na2CO3], indicating that the Na2O is incorporated into the glass network.
To investigate the potential use of a thermochemical software package (FactSage 6.2), in the design of alkaline earth boroaluminosilicate glass ceramics, experimental and modelled results on four glass ceramics were compared. Initially large discrepancies were found. These are described and related to deficiencies in the modelling of borate crystallisation and phase separation from a liquid oxide solution. Furthermore, a disparity in reproducing phase separations reported in the literature, through modelling, was also found. By accounting for potential error sources in the modelling, through semi-empirical optimisation of boron and alkali/alkali earth oxide activities in the liquid oxide solution, significantly improved fits between modelled and experimental results were obtained. Based on these results, it is suggested that more precise descriptions of higher order interactions need to be addressed, to account for the topology of multicomponent melts, before accurate prediction of phase relations within boron-containing glass ceramics can be obtained.
Glass ceramic (GC) materials containing a single phase of Ce: YAG microcrystals were developed from homogeneous glasses in an Y2O3-Al2O3-SiO2 system. The glass ceramics show yellow fluorescence due to the Ce3+ : 5d -> 4f transition by 460nm excitation. Backward excitation of the GC plate with a blue LED gives white emission, which is binary complementary. From the analyses of the electro-luminescence (EL) measurement data with an integrating, it was revealed that the composite of the GC and a blue LED chip gives high luminous efficiency comparable to that of commercial white LEDs working by the same current power. With increasing GC thickness, the color coordinate (x,y) of the spectra increased owing to the increase of ratio of yellow to blue bands. There exists an optimum thickness for the maximum luminous efficiency, where the GC show maximum yellow fluorescence by absorbing moderate amount of 460 nm-light. The variation of color coordinate locus in the CIE chromaticity diagram followed nearly that of the Planckian locus for the black body radiation. The correlated color temperature can also be changed from 8000K to 5000K by increasing GC thickness. With this GC plate, we can avoid the problems of the present packaged white LEDs, i.e., degradation of organic resin, difficulty in packaging of powder phosphors and so on.
Tb3+ (4f(8)) and Mn2+ (3d(5)) ions, known as active luminescent centres for blue, green and red fluorescence. were doped in various fluoride, phosphate and silicate glasses with well known structure. Narrow bands of f-f transitions with strong emission of Tb3+ in the blue, green and red and broad bands of d-d transitions of Mn2+ were measured with green emission in high optical basicity glasses with tetrahedrally coordinated Mn2+. Orange to red Mn2+ emission was found in glasses with low optical basicity where Mn2+ is octahedrally coordinated. Lifetimes, tau(e), in the range of milliseconds were recorded in dependence of glass composition and dopant concentration for both Tb3+ and Mn2+ doped glasses. Fluorescence lifetimes are as well shortened by higher basicity of the glasses as by increasing dopant concentration.
The molar entropy, S, and enthalpy (energy), H, of crystals, glasses and melts of the same one-component systems have been suitably visualized including the transformation from the melt into a glass or crystallization. For the temperature T -> 0 K the enthalpy and entropy of the glass are larger by Delta H-0 and Delta S-0 as compared to the stable crystal. The S and H functions of glasses correspond to a simple continuation of these functions from the molten state to lower temperatures. Crystallization occurs as a spontaneous process under production of entropy.Extrapolating the entropy of the molten and crystalline states from the melting range to lower temperatures, which is the basis of "Kauzmann's paradox", is ambiguous and misleading, as the extrapolated data deviate considerably from the experimental temperature dependencies of S of glasses and crystals. A proper extrapolation does not cause an entropy catastrophe as claimed in "Kauzmann's paradox", since the enthalpy difference between the undercooled melt and the corresponding crystals must be taken into account, and the respective entropies in both states are not connected by an isothermal process.The molar entropy and enthalpy are visualized as functions of temperature by numerical results of a Debye model. The molar entropy is a universal function of the ratio T vertical bar T-D, wherein T-D is the Debye temperature of the well known specific heat capacity, C-D. Between 0 K and T-D the entropy increases by 1.36 X 3R approximate to 4R irrespective of T-D. Above T-D, it increases approximately as 3R X 1n(T/T-D). The entropy capacity. C-D/T scales with 1/TD and the enthalpy with T-D, both considered as functions of T/T-D. The entropy capacity shows a maximum of 2.033 X 3R/T-D for T/T-D = 0.28.
High-power diode lasers show very efficient conversion of electrical into optical energy. Increasing absolute power levels, reliability in various operation modes, extended wavelength range and reduced cost become more and more important.For high-power industrial lasers in pumping or illumination applications, we developed a laser package that offers > 30W at good reliability and provides a collimated beam using internal optics at very low cost. This was achieved by using packaging concepts originally intended for high-power semiconductor devices.In the visible spectral region, powerful red laser diodes are available for a variety of applications, like medial or analytics. Extending the wavelength region even further, there is an increasing demand for green and blue lasers in the display market. Using new technologies like optically pumped semiconductor disk laser, this spectral range can be accessed in the near future via frequency doubling of IR light into blue and green. Crucial points are the low cost fabrication and assembly technology of the micro optical elements.
High power diode lasers are used in different applications, the main purpose is pumping of solid state lasers like rods, slabs and fibres, but also they find their way more and more in direct applications like soldering, welding, hardening etc. At the moment the strongest request from industrial customers who use this kind of technology in their production line is a demand for safe operation, reasonable durability i.e. long lifetime of the diode lasers used in these production lines. More than 20,000 hours of time are requested in order to satisfy the requests at the moment, but the trend is going to even higher requirements like 30,000 hours of minimum expected lifetimes and more for those modules. Different set-up technologies and research projects at JENOPTIK Laserdiode GmbH lead to a totally new design of cooling geometry in order to satisfy this kind of requests.
Containerless melting techniques provide great potential for small-scale preparation of highly homogeneous as well as high-purity glasses and glass ceramics. However, available techniques lack the possibility to produce samples of a size beyond some cm(3). Their applicability is usually limited to a certain group of materials, or a certain atmosphere or temperature range. A promising way that can be adopted from known techniques is optical melting by infrared image furnace techniques. Image furnaces and other floating zone techniques have been used to produce single crystals for decades. They have been shown to offer great experimental versatility and very high achievable temperatures at low operation cost when melting oxide materials. In this context, a xenon/halogen-based high-temperature image furnace was developed for processing non-conventional glasses with high transformation temperatures. It is demonstrated to offer obvious advantages which make it competitive to other containerless melting techniques.
Light directing glass with holographic optical elements (HOE) has been developed in joint research projects by collaboration of industry and the University of Dortmund for various building applications [1, 2, 3]. The holograms are produced on transparent films, which are laminated between two panes of floatglass. By the physical effect of diffraction HOE's can function as gratings, zone plates, lenses, mirrors or any other type of optical element. Large optical apertures, thin flat layers and lightweight are the features of HOE's. They can also offer unique optical properties, which are not possible with conventional optical elements. The main applications in buildings are light and colour images, improved daylighting and solar control in transparent elements. Another application is the projection of pictures in glazed building components, not being affected by other light sources.
We present the fabrication of ridge waveguides for generation of continuous-wave blue laser light. Efficient frequency doubling of IR laser sources has been demonstrated in KNbO3. waveguides produced via ion implantation, photolithography, and subsequent ion etching, Conversion efficiency as high as 23% W(-1)cm(-2) has been obtained at 438 nm. An alternative approach using femtosecond laser ablation for micromachining of ridge waveguides in borate crystals is under development for further wavelength extension to the UV range.
