Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (50)
- Vortrag (10)
- Beitrag zu einem Tagungsband (5)
- Beitrag zu einem Sammelband (4)
- Posterpräsentation (4)
- Buchkapitel (1)
Sprache
- Englisch (74) (entfernen)
Schlagworte
- Glass (12)
- Sintering (8)
- Crystallization (6)
- LTCC (6)
- Viscosity (5)
- Water-bearing glasses (5)
- Foaming (4)
- Glass powder (4)
- Inclusions (4)
- EBSD (3)
- Glass matrix composites (3)
- Internal friction (3)
- NMR spectroscopy (3)
- Oberflächenkeimbildung (3)
- Sintering kinetics (3)
- Surface energy (3)
- Thermal analysis (3)
- Water content (3)
- Alumina (2)
- Aluminosilicate glasses (2)
- Bond energy (2)
- Borate glasses (2)
- Crystal growth (2)
- Diopsid (2)
- Diopside (2)
- Glaskeramik (2)
- Glass ceramic composites (2)
- Glass structure (2)
- Glass transition (2)
- High pressure (2)
- Infrared spectroscopy (2)
- Ionic porosity (2)
- Modeling (2)
- Modelling (2)
- Orientation (2)
- Oriented surface crystallization (2)
- Orientierung (2)
- Relaxation (2)
- Rheology (2)
- SOFC (2)
- Silicates (2)
- Soda-lime-silica (2)
- Sol-gel processing (2)
- Solubility (2)
- Spectroscopy (2)
- Surface nucleation (2)
- Wasserhaltige Gläser (2)
- Water speciation (2)
- 27Al nuclear magnetic resonance (1)
- 3D etching (1)
- Acid-leaching (1)
- Al2O3-inclusions (1)
- Alkali aluminosilicate glasses (1)
- Alumina dissolution (1)
- Aluminium phosphate (1)
- Analytical scanning electron microscopy (1)
- Artificial weathering (1)
- Automated analysis (1)
- Barium and calcium silicate plass powders (1)
- Beta-christobalite structure type (1)
- Boratgläser (1)
- Borosilicate glass (1)
- Borosilicate glasses (1)
- Brittle fracture (1)
- Bubble formation (1)
- Calcium titanium phosphate (1)
- Calculated intrinsic fracture toughness (1)
- Coatings (1)
- Coordination polymers (1)
- Cordierite (1)
- Crack growth (1)
- Crosslinking (1)
- Crystal lattice (1)
- Curing (1)
- DCB geometry (1)
- DTA (1)
- Debindering (1)
- Degassing (1)
- Degradation (1)
- Densification (1)
- Density (1)
- Differential thermal analysis (1)
- Diffusivity (1)
- Dimensional stability (1)
- Effective Viscosity (1)
- Elastic constants (1)
- Environmental stability (1)
- Exposed metal sites (1)
- Facilitated activation (1)
- Ferrous phosphate hydrate (1)
- Fixation of silica (1)
- Fracture surface energy (1)
- Fragility (1)
- General Chemistry (1)
- Glas Matrix Composites (1)
- Glasmatrixkomposit (1)
- Glasmatrixkomposite (1)
- Glaspulver (1)
- Glass Ceramic (1)
- Glass Matrix Composites (1)
- Glass ceramic (1)
- Glass ceramics (1)
- Glass liner (1)
- Glass screening device (1)
- Glass transformation temperature (1)
- Glass-ceramic (1)
- Glasstruktur (1)
- Grain boundary precipitates (1)
- Growth kinetics (1)
- Growth rate (1)
- Heat treatment (1)
- High-cristobalite form (1)
- Hoher Druck (1)
- Hydrogen diffusivity (1)
- Hydrogen permeation (1)
- Hydrogen storage tank (1)
- Hydrous glass (1)
- In situ (1)
- Inconel 718 (1)
- Indentation fracture toughness (1)
- Ion beam erosion Sectioning (1)
- JMAK model (1)
- Kinetic Modelling (1)
- Kinetik (1)
- Kristallisation (1)
- Kristallwachstumsgeschwindigkeit (1)
- Laves phase (1)
- Lithiumionen-Batterie (1)
- Lösung (1)
- MOF-74 (1)
- Mass spectrometry (1)
- Materials Chemistry (1)
- Mechanical Engineering (1)
- Mechanical loss spectroscopy (1)
- Mechanics of Materials (1)
- Mechanochemistry (1)
- Metal additive manufacturing (1)
- Metals and Alloys (1)
- Microhardness (1)
- Milling (1)
- Mixed-linkers (1)
- Mixing (1)
- Modified Yoldas sols (1)
- Moisture (1)
- Nanochrystalline AlPO4 (1)
- Nucleation (1)
- Nucleation mode (1)
- Nucleation tendency (1)
- Oxide glasses (1)
- Permeability (1)
- Phase transitions (1)
- Phasenentwicklung (1)
- Phosphate (1)
- Polyurethane (1)
- Polyurethane (PU) (1)
- Porosity (1)
- Porous ceramics (1)
- Powder preparation (1)
- Powders (1)
- Property simulation (1)
- Rietveld analysis (1)
- Rigid Inclusion (1)
- Robot-assisted galss melting (1)
- SEM (1)
- Sample preparation (1)
- Silica-sol treatment (1)
- Silica-wood composites (1)
- Silicate Glasses (1)
- Silicate glass (1)
- Silicate glass powders (1)
- Silicoborate glasses (1)
- Silikatgläser (1)
- Sinter retardation (1)
- Sinterglaskeramik (1)
- Sintering Kinetics (1)
- Sintering glass composit bio material (1)
- Sintermodelle (1)
- Sintern (1)
- Slow crack growth (1)
- Soda-lime silicate glass (1)
- Sodium ion batteries (1)
- Sodiumborosilicate glasses (1)
- Sol-gel derived precursors (1)
- Solid-state reaction (1)
- Spektroskopie (1)
- Stabilization of high-temperature phase at RT (1)
- Stable crack growth (1)
- Stress intensity factor (1)
- Structural defects (1)
- Structural relaxation (1)
- Supersaturation (1)
- Surface Nucleation (1)
- Surface crystallization (1)
- Thermal analyses (1)
- Thermische Analyse (1)
- Thermo gravimetry (1)
- Ultrasonic relaxation (1)
- Unterschiedliche Atmosphären (1)
- Vacuum hot extraction (1)
- Vickers indentation (1)
- Viscous sintering (1)
- Viskoses Sintern (1)
- Viskosität (1)
- Vivianite (1)
- Water (1)
- Water in glass (1)
- Water repellency (1)
- Wood-inorganic composite (1)
- X-ray diffraction (1)
- XRD (1)
- high pressure (1)
- hydrogen storage (1)
- infrared spectroscopy (1)
- phosphate glasses (1)
- water speciation (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (31)
- 5.6 Glas (30)
- 6 Materialchemie (3)
- 5.1 Mikrostruktur Design und Degradation (2)
- 6.3 Strukturanalytik (2)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.2 Biophotonik (1)
- 1.7 Organische Spuren- und Lebensmittelanalytik (1)
- 5.0 Abteilungsleitung und andere (1)
- 5.2 Metallische Hochtemperaturwerkstoffe (1)
Eingeladener Vortrag
- nein (10)
The fundamental processes of nucleation and crystallization are widely observed in systems relevant to material synthesis and biomineralization; yet most often, their mechanism remains unclear. In this study, we unravel the discrete stages of nucleation and crystallization of Fe3(PO4)2·8H2O (vivianite). We experimentally monitored the formation and transformation from ions to solid products by employing correlated, time-resolved in situ and ex situ approaches. We show that vivianite crystallization occurs in distinct stages via a transient amorphous precursor phase. The metastable amorphous ferrous phosphate (AFEP) intermediate could be isolated and stabilized. We resolved the differences in bonding environments, structure, and symmetric changes of the Fe site during the transformation of AFEP to crystalline vivianite through synchrotron X-ray absorption spectroscopy at the Fe K-edge. This intermediate AFEP phase has a lower water content and less distorted local symmetry, compared to the crystalline end product vivianite. Our combined results indicate that a nonclassical, hydration-induced nucleation and transformation driven by the incorporation and rearrangement of water molecules and ions (Fe2+ and PO4 3−) within the AFEP is the dominating mechanism of vivianite formation at moderately high to low vivianite supersaturations (saturation index ≤ 10.19). We offer fundamental insights into the aqueous, amorphous-to-crystalline transformations in the Fe2+−PO4 system and highlight the different attributes of the AFEP, compared to its crystalline counterpart.
The process of viscous flow sintering is a phenomenon that is closely linked to the surface properties of the glass particles. In this work, we studied the extreme case of acid-leaching of soda-lime-silicate glass beads of two different particle size distributions and its effects on non-isothermal viscous sintering of powder compacts. Depth profiling of the chemical composition after leaching revealed a near-surface layer depleted in alkali and alkaline earth ions, associated with concurrent hydration as mass loss was detected by thermogravimetry. Heating microscopy showed that acid treatment of glasses shifted the sinter curves to higher temperatures with increasing leaching time. Modelling of the shrinkage with the cluster model predicted a higher viscosity of the altered surface layer, while analysis of the time scales of mass transport of mobile species (Na+, Ca2+ and H2O) during isochronous sintering revealed that diffusion of Na+ can compensate for concentration gradients before sintering begins. Also, exchanged water species can diffuse out of the altered layer, but the depletion of Ca2+ in the altered surface layer persists during the sinter interval, resulting in a glass with higher viscosity, which causes sintering to slow down.
Up to now, the mechanisms of surface nucleation and surface-induced texture formation are far from being understood. Corresponding phenomena are discussed hypothetically or even controversial, and related studies are restricted to very few glasses. As a main drawback, the vast majority of previous work on oriented growth of surface crystals do not consider the possible effects of glass surface treatments (like polishing defects, adhered particles and cracks, …) or ambient annealing conditions (vacuum or atmospheric pressure) which both can influence crystal nucleation and growth. Moreover, very few observations of crystal orientation related to surface crystallization were focused on separately growing crystals. In conclusion, up to now, no systematic studies on initially oriented crystal growth or nucleation from defined active nucleation sites have been pursued.
Therefore, the main objective of the proposed project is to gain a basic understanding of the mechanisms of surface-induced microstructure formation in glass ceramics. We shall answer the question whether preferred orientation of surface crystals is the result of oriented nucleation or caused by other orientation selection mechanisms acting during early crystal growth. In both cases, crystal orientation may be caused by the orientation of the glass surface itself or the anisotropy and orientation of active surface nucleation defects.
New techniques of experimental characterization of surface-crystallized glasses shall be applied to find answers to the questions posed above. Based on a controlled preparation and annealing of the glass sample surfaces, that includes the defined creation of active nucleation defects, and followed by the microstructural characterization especially during the very early growth stages of separated surface crystals, the orientation relations between defect and initiated surface crystal will be analyzed. In order to gain new insights, a couple of entirely new microstructure diagnostics techniques, including chemically contrasted XRM, laser-based sample preparation for XRM, and 3D electron backscatter diffraction shall be developed or applied.
This way, using X-ray microscopy as a pivotal technique for the non-destructive 3D characterization of relatively large samples at superior spatial resolution (but also complemented by other microstructure diagnostics techniques, e.g. TEM elemental mappings at cross-sectioned samples) unprecedented insights into the microstructure evolution upon surface crystallization of model glasses will be gained.
Up to now, the mechanisms of surface nucleation and surface-induced texture formation are far from being understood. Corresponding phenomena are discussed hypothetically or even controversial, and related studies are restricted to very few glasses. As a main drawback, the vast majority of previous work on oriented growth of surface crystals do not consider the possible effects of glass surface treatments (like polishing defects, adhered particles and cracks, …) or ambient annealing conditions (vacuum or atmospheric pressure) which both can influence crystal nucleation and growth. Moreover, very few observations of crystal orientation related to surface crystallization were focused on separately growing crystals. In conclusion, up to now, no systematic studies on initially oriented crystal growth or nucleation from defined active nucleation sites have been pursued.
Therefore, the main objective of the proposed project is to gain a basic understanding of the mechanisms of surface-induced microstructure formation in glass ceramics. We shall answer the question whether preferred orientation of surface crystals is the result of oriented nucleation or caused by other orientation selection mechanisms acting during early crystal growth. In both cases, crystal orientation may be caused by the orientation of the glass surface itself or the anisotropy and orientation of active surface nucleation defects.
New techniques of experimental characterization of surface-crystallized glasses shall be applied to find answers to the questions posed above. Based on a controlled preparation and annealing of the glass sample surfaces, that includes the defined creation of active nucleation defects, and followed by the microstructural characterization especially during the very early growth stages of separated surface crystals, the orientation relations between defect and initiated surface crystal will be analyzed. In order to gain new insights, a couple of entirely new microstructure diagnostics techniques, including chemically contrasted XRM, laser-based sample preparation for XRM, and 3D electron backscatter diffraction shall be developed or applied.
This way, using X-ray microscopy as a pivotal technique for the non-destructive 3D characterization of relatively large samples at superior spatial resolution (but also complemented by other microstructure diagnostics techniques, e.g. TEM elemental mappings at cross-sectioned samples) unprecedented insights into the microstructure evolution upon surface crystallization of model glasses will be gained.
A glass of the composition 37BaO·16CaO·47SiO2 wt% produced on an industrial scale is crystallized at 970 °C for times ranging from 15 min to 2 h. The crystallization at the immediate surface as well as the crystal growth into the bulk are analyzed using scanning electron microscopy (SEM) including energy dispersive X-ray spectroscopy (EDXS) and electron backscatter diffraction (EBSD) as well as X-ray diffraction in the Θ–2Θ setup (XRD). The immediate surface shows the oriented nucleation of walstromite as well as the formation of wollastonite and an unknown phase of the composition BaCaSi3O8. All three phases also grow into the bulk where walstromite ultimately dominates the kinetic selection and grows throughout the bulk due to a lack of bulk nucleation. Walstromite shows systematic orientation changes as well as twinning during growth. A critical analysis of the XRD-patterns acquired from various crystallized samples indicates that their evaluation is problematic and that phases detected by XRD in this system should be verified by another method such as EDXS.
Up to now, the mechanisms of surface nucleation and surface-induced texture formation are far from being understood. Corresponding phenomena are discussed hypothetically or even controversial, and related studies are restricted to very few glasses. In this talk the state of the art on mechanisms of surface nucleation are summarized. On one hand, mechanical damaged surfaces show high nucleation activity, at which the nucleation occurs at convex tips and edges preferentially. On the other hand, solid foreign particles are dominant nucleation sites at low damaged surfaces. They enable nucleation at temperatures even far above Tg. The nucleation activity of the particles is substantially controlled by their thermal and chemical durability. But no systematic studies on initially oriented crystal growth or nucleation from defined active nucleation sites have been pursued, so far. Therefore, the main objective of a just started project is to advance the basic understanding of the mechanisms of surface-induced microstructure formation in glass ceramics. We shall answer the question whether preferred orientation of surface crystals is the result of oriented nucleation or caused by other orientation selection mechanisms acting during early crystal growth. In both cases, crystal orientation may be caused by the orientation of the glass surface itself or the anisotropy and orientation of active surface nucleation defects. As a first attempt we focused on possible reorientation of separately growing surface crystals during early crystal growth. First results show clear evidence that separately growing crystals can reorient themselves as they are going to impinge each other.
Borosilicate glasses (16Na2O–10B2O3–74SiO2, NBS) with water contents up to 22 mol% H2O were prepared to study the effect of water on structural relaxation using DTA, viscometry and internal friction measurements. The results show that the glass transition temperature Tg of DTA and the isokom temperature T12, of viscometry are in excellent agreement, confirming the equivalence of enthalpy and viscous relaxation for NBS glass. Combining Tg data with water speciation data demonstrates that OH groups are mainly responsible for the decrease of Tg with increasing hydration, while molecular water plays only a minor role. Internal friction spectra at 7.125 Hz confirm the decisive influence of water on mechanical relaxation. The temperature range of α-relaxation (glass transition) strongly decreases while two β-relaxation peaks (sub-Tg) progressively appear with increasing water content. A high temperature β-relaxation peak, attributed to the presence of OH groups, shifts from 670 to 450 K as total water content increases from 0.01 to 5 wt%. A low temperature β-relaxation peak, attributed to molecular water, appears at 380 K and 330 K in glasses containing 3 and 5 wt% H2O, respectively. These findings suggest that relaxation mechanism of different hydrous species at low temperature may contribute to fatigue of stressed glasses.
Stable crack growth was measured for nominal dry and water-bearing (6 wt%) soda-lime silicate glasses in double cantilever beam geometry and combined with DMA studies on the effects of dissolved water on internal friction and glass transition, respectively. In vacuum, a decreased slope of logarithmic crack growth velocity versus stress intensity factor is evident for the hydrous glass in line with an increase of b-relaxation intensity indicating more energy Dissipation during fracture. Further, inert crack growth in hydrous glass is found to be divided into sections of different slope, which indicates different water related crack propagation mechanism. In ambient air, a largely extended region II is observed for the hydrous glass, which indicates that crack growth is more sensitive to ambient water.
Sintering and foaming of barium and calcium silicate glass powder compacts have been studied for different powder milling. Sintering was measured by means of heating microscopy backed up by XRD, DTA, Vacuum Hot Extraction (VHE) and electron microscopy. Foaming intensity strongly increased with decreasing glass partiefe size. Although powder compacts were uniaxially pressed and sintered in ambient air, foaming was affected by the milling atmosphere and most intensive for milfing in C02. Conformingly, VHE studies revealed that foaming of fully sintered samples was mainly driven by C02, even for powders milled in technical air, Ar and N2. Prolonged storage of air milled barium silicate glass powders in ambient air before pressing and sintering caused further increase of foaming intensity. These findings indicate that carbonaceous species are preferentially trapped to or close beneath the powder surface during milling and later storage. The temperature range of C02 degassing from fully sintered barium and calcium silicate g/ass powder compacts fits the temperature ranges of decomposition of BaC03 and CaC03 mix-milled with the respective barium and calcium silicate glass powders.
In the present study we have investigated whether the effect of water on properties of borate glasses resembles that of alkali oxide. Soda-lime-borate glasses with nominal compositions of x Na2O, 10 CaO, (90-x) B2O3 (x = 5, 15 and 25 mol%) were doped with up to 8 wt.% H2O by processing glass powder + distilled water in platinum capsules in an internally heated gas pressure vessel at 1523 K and 500 MPa. The water content of hydrous glasses was determined by Karl-Fischer titration and near-infrared spectroscopy. The glass transition temperature T-g. was derived from DTA and micropenetration experiments for which the effect of water loss at the surface of the hydrous glasses was studied. Heating glass samples at 10 K min(-1) in the DTA resulted in T-g values which are close to T-12 isokom temperatures confirming the equivalence of enthalpy relaxation and viscous relaxation for borate glasses. For all three glass series it is shown that T-g strongly decreases whereas the liquid fragility strongly increases upon the addition of water. These findings reveal that H2O primarily causes breaking of B-O-B bonds rather than supporting 4-fold coordinated boron as it is well-known for alkali oxides in this concentration range. (C) 2015 Elsevier B.V. All rights reserved.
The crystallization behavior of sodium ion conductive Na2MnP2O7 glass was examined to clarify the crystallization mechanism. The formation of thermodynamically metastable phase, layered Na2MnP2O7, at the surface of the glass occurred. Heat treatment at 430 °C for 3 h lead to surface crystals of Na2MnP2O7 oriented with the (101) direction perpendicular to the sample surface. As the heat treatment temperature increased, the glass-ceramic samples deformed, and the presence numerous micro bubbles due to dissolved water was detected.
The crystallization of 11BaO-25CaO-64SiO2 mol% glass powders and related effects of glass powder milling have been studied by X-ray diffraction (XRD), light and scanning electron microscopy (SEM) and differential thermal analysis (DTA). Glass powders were made by ZrO2 crushing with subsequent sieving or sedimentation or alternatively made by milling with agate, corundum and tungsten carbide. Although surface crystallization was detectable during late sintering, all powders fully sintered. Wollastonite was found as primary crystal phase followed by cristobalite and sanbornite precipitation. The latter crystallization steps caused a second DTA-peak for fine powders. DTA-peak temperatures shifted to lower temperature with decreasing particle size in any case. No significant effects of milling materials on DTA-peak temperatures were evident. As an exception, however, milling in agate caused strongly decreased temperatures of the second DTA-peak. This observation can be explained by the progressive mechanical damaging, which results from the required prolonged milling time with agate due to its small materials density, and the fact that diamond made scratches did promote surface crystallization of cristobalite. The present study thus shows that even for glass powders with excellent sinterability, milling can affect microstructure evolution.
Open cell rigid foams made from polyurethane (PU) are frequently used in ceramic processing for preparation of porous ceramics by the so-called replica technique. This work presents data regarding the PU burnout, shrinkage characteristics as well as the morphology of the ceramic coated PU sponges during heating up. Shrinkage of the ceramic coated PU sponges closely follows the mass loss due to PU decomposition. Two temperatures (i) 267 °C and (ii) 380 °C were identified at which PU decomposition reaches local maxima. Shrinkage measurements on ceramic coated PU sponges reveal that both PU decomposition stages lead to similar extends of shrinkage in the ceramic coated PU sponge. Differential thermal analysis (DTA) showed that the two decomposition related temperatures (267 and 380 °C) differ concerning the energy release. While the low-temperature signal is endothermic, an exothermic signal was detected at 380 °C. The morphology of the ceramic coated PU sponges was investigated with scanning electron microscopy (SEM) which gave insight into the formation of hollow ceramic struts-a well known feature of ceramics being prepared by the replica technique.
This work compares thin layers (films) and monoliths prepared from alumina sols with respect to their microstructure, thermal evolution, porosity and specific surface area. After heat treatment at similar temperatures, films and monoliths showed the same qualitative changes in porosity and specific surface area. However, some marked quantitative differences were detected. Film fragments had a lower open porosity, a lower specific surface area and a narrower pore size distribution. Furthermore, the thermal evolution showed a markedly different burnout of organic components between films and monoliths. The observed differences between films and monolith can be explained by the ageing history of the sols during sample preparation.
Sintering of LTCC
(2008)
Low Temperature Co-fired Ceramic materials (LTCC) have attracted growing interest in recent years since they are promising candidates for highly integrated ceramic packaging. This paper surveys materials concepts of related glass ceramic composites (GCC) and discusses unsolved problems and challenges. The densification of GCC based on "viscous sintering" may be affected by steric effects and partial dissolution of dispersed crystal particles, crystallization and phase boundary reactions.
The manufacture of sintered glasses and glass-ceramics, glass matrix composites, and glass-bounded ceramics or pastes is often affected by gas bubble formation. Against this background, we studied sintering and foaming of barium silicate glass powders used as SOFC sealants using different powder milling procedures. Sintering was measured by means of heating microscopy backed up by XPD, differential thermal analysis, vacuum hot extraction (VHE), and optical and electron microscopy. Foaming increased significantly as milling progressed. For moderately milled glass powders, subsequent storage in air could also promote foaming. Although the powder compacts were uniaxially pressed and sintered in air, the milling atmosphere significantly affected foaming. The strength of this effect increased in the order Ar ≈ N2 < air < CO2. Conformingly, VHE studies revealed that the pores of foamed samples predominantly encapsulated CO2, even for powders milled in Ar and N2. Results of this study thus indicate that foaming is caused by carbonaceous species trapped on the glass powder surface. Foaming could be substantially reduced by milling in water and 10 wt% HCl.
Boron oxide glasses usually show low glass transition temperature Tg due to the three-fold oxygen coordination of boron. Adding of alkali and alkaline earth oxides to the glass composition will not decrease but increase Tg due to a change in boron coordination from trigonal to tetrahedral, known as the boron anomaly. Only for higher fractions of alkali oxides, non-bridging oxygens (NBO) are progressively formed in competition with tetrahedrally coordinated boron, which leads to a decrease in viscosity.
ln contrast to this well-known behavior of alkali oxides (R2O), there is little known about adding H2O to borate glasses. The present work therefore aims in shedding light on the rheological properties of hydrous soda lime borate glasses with particular focus on the role of water. For doing so, we determined Tg as a function of Na2O and H2O content using differential thermal analysis (DTA) backed up by micropenetration viscosity measurements. Results show that water decreases Tg for all glasses and water concentrations under study (< 8 wt.% total water). Obviously, water mostly causes the formation of NBO having no significant influence on boron coordination as seen for alkaline.
The structural investigation of hydrated borate glasses provides new insights on the influence of water on boron speciation using spectroscopic methods. In the present study three soda–lime–borate glasses (NCBx with x = 5, 15 and 25 corresponding to xNa2O, 10CaO, 90 - xB2O3 in mol%) were prepared with water content up to 8 wt.%. The water speciation in the glasses was derived by near-infrared (NIR) spectroscopy while boron speciation was investigated by 11B MAS NMR (Magic Angle Spinning Nuclear Magnetic Resonance). For the three glasses effective molar absorption coefficients were determined experimentally for the bands at 5200 cm- 1 and 4600 cm- 1, corresponding to combination modes of H2O molecules and OH-groups, respectively. In contrast to silicate glasses, in which at most ~ 2 wt.% H2O are dissociated to OH-groups, the amount of dissociated H2O may even exceed 5 wt.% in borate glasses. The fraction of tetrahedral to total boron (N4 = BIV / BIV + BIII) is predominantly controlled by the ratio of Na2O + CaO / B2O3, but only weakly affected by the water content of the glasses. When increasing the H2O content from 0 to 8 wt.%, N4 increases from 25% to 26% for NCB5 and from 42% to 47% for NCB25 glasses.