Reaction of silica with tetraethyl orthosilicate

The reaction of tetraethyl orthosilicate with fumed silica at various temperatures was investigated by means of infra-red spectroscopy and gas chromatography. It was found that essentially no reaction occurred at 25° while at 100°, traces of reaction by-products were detected after short reaction periods. When the reaction temperature was raised to 165°, the condensation reaction proceeded with both hydrated and predried silica glass. It was shown that silanol sites on the glass do take part in a reaction which results in the formation of new siloxane bonds. These sites can be rehydrated after thermal degradation of the treated surfaces in vacuum.     

Removal of fatty soil from glass. Electrolyte detergent-builder effect

Summary The mechanism of radio-tagged tristearin removal from a glass substrate by sodium tripolyphosphate is primarily one of preferential displacement. Tristearin removal by STP appears to be a competition for primary polar adsorption sites: being the more polar, STP displaces the soil. Continuous soil films are more slowly removed than spotty soil films because initially fewer accessible adsorption sites are available for displacement attack by STP. It is believed that emulsification of these heavy films occurs initially by the ‘stripping” or preferential displacement by STP of the adsorbed monolayer at a site, followed by a rolling up of coherent soil along with the desorbed monolayer, resulting in a degree of emulsification. In addition to its sequestrant water-softening action, previously considered its main function, and its detersive effectiveness, another very important feature has been discovered. Tripolyphosphate (and sequestrant type of anion) adsorbs on a glass surface and reduces the tenacity of subsequent fatty resoiling. This may account to a considerable degree for the demonstratedly high practical cleansing effectiveness of the compound. Adsorption of STP is not by a base exchange mechanism for quartz also displays the same effect as glass. It seems apprarent that the same type of adsorption sites exists on both glass and quartz surfaces though those on quartz suggest either a stronger adsorption of a higher energy level or a larger number of adsorption sites. These data demonstrate the relatively high detersive efficiency of the polyphosphates for this soil/substrate system. Sodium metasilicate and sodium carbonate fall considerably lower in soil-removal value.     

Site-Dependent Study of the Optical Properties of Eu3+ in Pure and Chlorine-Doped Fluorozirconate Glasses

For the present study, the emission spectra and lifetimes of Eu³⁺ in fluorozirconate and fluorochlorozirconate glasses were measured site dependently using the fluorescence line narrowing (FLN) technique. At high excitation energies, two different types of Eu³⁺ sites can be distinguished in fluorozirconate glass. The introduction of chloride into this glass caused a significant effect at low excitation energy.     

Impact Fracture of Thermally Tempered Glass Helicopter Windshields

In-service fracture of helicopter windshields was studied. Simulated catastrophic fracture tests were conducted by firing alumina and steel spheres onto stationary tempered and as-received glass panels. The results were studied by Hertzian analysis and modified Auerbach's relations. Thermally tempered glass shows much higher impact resistance than that estimated from superposition of residual stresses. Subcritical impact sites exhibit slow crack growth in tempered plates, eventually leading to fracture of the entire plate.     

The Heterogeneity of Glass Surfaces Revealed by Temperature Programmed Desorption

Adsorption of butanol and pyridine on E‐glass fibers with three different compositions, as well as on powders of silica and the crushed fibers, was studied by temperature programmed desorption (TPD) with a mass‐sensitive detector. In the case of butanol, there are two types of desorbing molecules: at lower temperatures butanol desorbs, but in the range 450°C–600°C, 1‐butene desorption is also observed. It is shown that 1‐butene desorption is due to thermal decomposition of butanol chemisorbed to OH groups on both the glass and silica surfaces. The binding energy distributions of adsorption sites for butanol and pyridine are similar on all three glass compositions, but they are much more heterogeneous compared to silica; this difference is most evident for pyridine and is attributed to the presence Al and B in the glasses. The decomposition temperature of chemisorbed butanol is highest for silica and depends on glass composition for the fibers and powders. Interestingly, the glass which does not contain boron shows a well‐defined peak for the decomposition of chemisorbed butanol, suggestive of unique adsorption sites on this boron‐free surface; but they are much less temperature stable than the chemisorption sites on silica. In situ exposure to water vapor increased the number of active sites for chemisorption.     

Acid–Base interactions in filler characterization by inverse gas chromatography

Glass beads as model fillers were characterized by inverse gas chromatography (IGC) according to the Lewis acid–Lewis base (donor–acceptor) concepts as adapted by Fowkes. A range of organic probes (acidic chloromethanes, neutral n-alkanes, and basic acetone and diethylether) was used to elucidate the acid–base nature of the glass bead surface. The untreated glass bead surface was found to contain predominantly acidic sites while the treated glass bead (treated with an aminopropyltriethoxysilane coupling agent) was more basic than its unmodified counterpart. Calculation of the enthalpies of acid–base interactions (ΔH^ab) form the retention behavior of the basic probes with the two glass beads produced at least an 8-kJ/mol difference between the two glass types, the ΔH^ab of the untreated glass being greater than the treated glass. A difference of this magnitude is sufficient to produce a corresponding difference in the interfacial behavior of the two glass types. Therefore, IGC can be used as a quantitative technique for characterizing filler surfaces.     

Mechanochemical Wear of Soda Lime Silica Glass in Humid Environments

The mechanochemical wear of multicomponent glasses was studied under controlled humidity conditions using a reciprocating ball‐on‐flat tribometer. For dry conditions, the surfaces were extensively damaged by scratching for all of the glasses, while for humid conditions the wear behavior varied with the glass composition suggesting a chemical effect on scratch behaviors of glass surfaces. The wear of soda lime silica (also called sodium calcium silicate) glass was suppressed with increasing humidity, while the borosilicate and barium boroaluminosilicate glasses showed an increase in wear volume with increasing humidity. The unique humidity dependence of the observed mechanochemical wear of soda lime silica glass supports the hypothesis that hydronium ion formation in the sodium‐leached sites of the soda lime glass enhances its wear resistance.     

Multi-step derivatization and analysis of the surface of nonporous silicate glass

Multi-step heterogeneous phase chemical reaction schemes were used to develop different surface chemistries on nonporous glass substrates. Reliable analysis of the products of reaction was needed, because many of the functional groups introduced to the surface were intended to serve as reactive sites for further chemical tailoring to meet specific applications. Because the mass of the surface derivatization layer was only parts per million of the substrate mass, analysis of the reaction products was daunting. However, surface evaluation was accomplished by using several analysis methods in combination and by using the particular glass geometry most suitable to each analysis method.     

石英玻璃和载玻片衬底磁控溅射纳米TiO_2薄膜的光致亲水性(英文)

采用射频磁控溅射法在石英和载玻片衬底上淀积纳米TiO2薄膜。利用X射线衍射仪、原子力显微镜、紫外可见分光计和接触角仪对薄膜相结构、表面形貌、光学性能和光致亲水性能进行表征。结果表明:在高压汞灯的辐射下,薄膜呈现出从疏水到亲水性能的转变。TiO2薄膜的光致亲水性能与衬底有关,载玻片衬底的TiO2薄膜的光致亲水性能优于石英玻璃衬底。载玻片衬底上淀积的薄膜经高压汞灯辐射240min后呈现出超亲水性能。讨论了薄膜的能隙、Ti3+缺陷位和衬底对TiO2薄膜的光致亲水性能的影响。     

Hydronium Ions in Soda‐lime Silicate Glass Surfaces

The presence of leachable alkali ions, or their hydrated sites in the glass, is believed to be a determining factor for the interfacial water structure at the glass surface, influencing the surface properties of glass. The interfacial water structure on soda‐lime silicate glass in humid ambience at room temperature was analyzed with sum‐frequency‐generation (SFG) vibration spectroscopy, which can probe the interfacial water layer without spectral interferences from the gas phase water. The soda‐lime glass surface exposed to water vapor shows three sharp SFG peaks at 3200, 3430, and 3670 cm^?1 in SFG, which is drastically different from the SFG spectra of the water layers on the fused quartz glass surface and the liquid water/air interface. The sharp peak at 3200 cm^?1 is believed to be associated with the hydronium ions in the Na⁺‐leached silicate glass surface. The 3200 cm^?1 peak intensity varies with the relative humidity, indicating its equilibrium with the gas phase water. It is proposed that the hydronium ions in the Na⁺‐leached sites produce compressive stress in the silicate glass surface; thus the growth of hydronium ions with increasing humidity might be responsible for the increased wear resistance of soda‐lime glass surfaces in near‐saturation humidity conditions.     

A specific distribution and bonding mechanism of emulsified adhesives in granular and fibrous substrates

It is shown both theoretically and experimentally that highly effective bonding of granular and fibrous materials can be realized on the basis of a specific liquid distribution and adhesive linkage mechanism of emulsions during evaporation. The formation of adhesive links was investigated with glass microspheres as a standard substrate and a series of emulsified and dissolved adhesives. In contradistinction to dissolved adhesives, emulsified adhesives of the type oil-in-water could be located almost quantitatively at the contact sites of the substrate material as a result of interfacial retraction during evaporation. Retraction and the selective accumulation of the adhesive at contact sites of the glass microspheres appeared to be governed by the contact angle, the surface tension, and the colloidal stability of the emulsion. Aggregate formation was measured with a given amount of the adhesive in different states of dilution, so as to change the water content of the substrate upon application. These measurements showed that water is involved in the distribution of emulsified adhesives as a carrier: relatively high water contents of the substrate are required in order to incorporate the larger substrate materials into aggregates. The formation of aggregates and their mechanical stability attain a maximum at dilutions corresponding to saturation of the substrate capillary system. This carrier mechanism was confirmed by measurements of the size distributions of the glass particles in aggregates of different size classes. The selective location of adhesives at the contact sites of substrate materials, the high efficiency of aggregate formation, and the high aggregate stability are promising in view of the production of composites with specific perspiration characteristics.     

Radiotagged soils. Removal from several substrates and adsorption site character

Substrates investigated were glass, quartz, porcelain, steel, stainless steel, aluminum, polyethylene, methylmethacrylate, Nylon, and Teflon. Radiotagged (C-14) soils used were algal protein, stearic acid, and tristearin. Soil removal curves showed that Nylon, Teflon, methacrylate, and stainless steel had few soil-adsorption sites and that the adsorption was of an ion-exchange type. Algal protein and stearic acid soils appeared to adsorb through an ion-exchange type mechanism, with most substrates, while tristearin showed a van der Waals' type of adsorption with glass, quartz, steel, and aluminum. Conclusions as to adsorption type were based upon the shape of the soil-removal curves. Adsorption studies showed that both anionic and nonionic surfactants were adsorbed by glass, procelain, steel, and aluminum surfaces, apparently by an ion-exchange type of adsorption. The character of the surfactant adsorbed affected the degree of removal of subsequently applied soil; the more hydrophilie surfactants permitted easier soil-removal. Tripolyphosphate, orthophosphate, and ethylenediamine tetraacetate anions and tetraethylammonium cations were adsorbed by these same substrates and influenced the ease of removal of subsequently applied soil. Pretreatment of substrate by alkali generally increased the ion or surfactant adsorption more than acid-pretreated surfaces, and rather marked similarities between the adsorption sites of glass and quartz were apparent from acid pretreatment. Stearic acid soiled substrates were cleaned by a preferential displacement mechanism; the soil was rolled up into globules. Tristearin-soiled surfaces were cleaned by a similar mechanism.     

Surface Nucleation and Crystal Orientation in Lithium Silicate Glass Fibers

The effect of inorganic surface treatments on the orientation of lithium disilicate crystals formed in Li₂O·2.75SiO₂ glass fibers was studied. Glass fibers 0.5 mm and 9μ in diameter were subjected to various surface treatments at room temperature and then heated between 550O and 800°C. It was observed that metal salt solutions applied to the fiber surfaces at room temperature decreased the degree of orientation during heating only if the metal entered the glass and formed nucleation sites within the fibers. Orientation could also be decreased by removing lithium from the glass surfaces. Comparison of the crystallization characteristics of untreated and AgNO₃-treated fibers indicated that the crystallization behavior was controlled by either a growth process or a nucleation process, depending on whether the temperature was below or above 625°, respectively.     

Crystallization kinetics of glass fiber reinforced PBT composites

The effect of glass fibers on the crystallization of poly(butylene terephthalate) (PBT) was investigated by crystallization kinetics analysis under isothermal and nonisothermal conditions. From the crosspolar optical micrographs of melt‐ and solvent‐crystallized PBT composites, the glass fibers were found to increase the number density and decrease the size of crystallites. The glass fibers provided heterogeneous nucleation sites, and thus enhanced the overall rate of PBT crystallization in isothermal experiments. However, the Avrami exponent and the regime transitions were not significantly affected by the presence of glass fibers. For the nonisothermal kinetics of PBT composites, the model prediction was excellent in most ranges of crystallization, but it deviated above 70% of crystallization especially at fast cooling rates (>40°C/min). This discrepancy of the model seemed to result from the growth regime transitions, which were clearly observed especially at high undercoolings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 576–585, 2000     

Synthesis and Characterization of a SiAION Glass

Homogeneous SiAION glasses containing up to 1 wt% nitrogen were synthesized via a pressureless method with a controlled quench rate and structurally investigated using ²⁷Al and ²⁹Si magic-angle spinning nuclear magnetic resonance (MAS NMR), Raman, and infrared (IR) spectroscopies. Minor changes occur with the incorporation of nitrogen into the aluminosilicate glass structure as evidenced by modifications to spectra of a nitrogen-free aluminosilicate glass. The ²⁷Al MAS NMR spectrum of the SiAION glass shows the existence of aluminum in 4-,5-, and 6-coordination to oxygen. The ²⁹Si MAS NMR spectra show a distribution of silicon sites in 4-coordination to oxygen. Raman and IR spectra of the SiAION glass show additional features due to incorporation of nitrogen in the structure compared with spectra of nitrogen-free aluminosilicate glasses.     

The production of Indo-Pacific monochrome drawn glass beads in the Sasanian Empire: Insights from Xinjiang,northwest China

Indo-Pacific glass beads are produced by the drawn technique, which originates from South Asia, and their chemical compositions are unique in South and Southeast Asia. However, a small number of Indo-Pacific beads with Sassanian glass compositions are excavated in Asia and Africa after the 3rd c. CE, and their production sites in South/Southeast Asia or in the Sassanian region remain controversial. In this study, 15 drawn glass beads with various colours from Astana necropolis (ca. the 4th-8th c. CE) in Xinjiang, northwest China were investigated by using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), Scanning Electron Microscope, Raman spectroscopy and visible to near-infrared spectroscopy to characterize the production technology and origins. The results show that most Astana glass beads share similar chemical compositions with the glassware from Veh Arda?īr, a famous Sasanian site. Furthermore, Sasanian glass compositions predominate in Indo-Pacific beads in Xinjiang during the 4th-8th c. CE, while popular glass recipes in contemporary South/Southeast Asia are infrequently found; thus, it is deduced that the drawn method should have been mastered by Sasanian craftsmen. Moreover, the cobalt materials in Sasanian glass were imported from further western regions and changed over time. The popular Sasanian glass across central Eurasia reflects the trade monopoly of Sasanian in West and Central Asia, and the land glass bead trade is distinct from the contemporary maritime trade in the Indian and Pacific Oceans.     

北京市大气颗粒物中多环芳烃的分布特征

用撞击式分级采样器同步采集了北京市城乡结合部、郊区的2003年4个季节的不同粒径大气颗粒物样品,用气相色谱-质谱分析了其中的多环芳烃,并对两个地区大气颗粒物中的多环片烃含量、分布及季节性变化特征进行了探讨。     

Heterogeneous Plantinum Nucleation and Crystallization of a Heavy-Metal Fluoride Glass

The effect of controlled heterogeneous nucleation by platinum on the crystallization of a ZrF₄-BaF₂-LaF₃-AlF₃-NaF (ZBLAN) glass was studied. Various levels of platinum were incorporated into this glass by a combination of PtCl₂-doping and melting-atmosphere variation. The effect of doping levels and melting conditions on the incorporation of platinum and the subsequent nucleation of crystals was studied by optical microscopy, scanning electron microscopy, differential scanning calorimetry (DSC), and X-ray diffraction. Increased platinum in the glass resulted in an increased number of nucleation sites for the growth of β-ZrF₄-BaF₂ crystals. Analysis of isothermal and ramp-rate DSC measurements indicated that the crystallization of this glass changed from surface controlled to bulk controlled with an increased number of nuclei. This was confirmed by optical microscopy. In addition, Avrami analysis of the isothermal crystallization data gave an accurate approximation of the number of nuclei in the glass.     

Thermal Poling of Soda‐Lime Silica Glass with Nonblocking Electrodes—Part 1: Effects of Sodium Ion Migration and Water Ingress on Glass Surface Structure

It is generally well known that not only the sodium itself, but also the non‐bridging oxygen (NBO) sites associated with sodium ions are largely responsible for the surface reactivity of soda‐lime‐silica (SLS) glass. Thermal poling can modify the distribution of sodium in the subsurface region. In this work, a commercial SLS float glass was thermally poled using nonblocking electrodes in air. The Na⁺?depleted anode surface and the Na⁺?gradient cathode surface were characterized using a variety of methods to find the compositional, structural and morphological effects of thermal poling. Of particular significance is the use of nondestructive vibrational spectroscopy methods, which can lead to new and improved understanding of water interactions with sodium and its sites in the glass. It was found that during thermal poling, the Na⁺?depleted glass network on the anode side undergoes condensation reactions of NBO sites accompanied by the increase in concentrations of silanol (SiOH) groups and molecular water species. In contrast, silanol and water species do not increase and the silicate network change is negligible in the Na⁺?gradient cathode side. Vibrational sum frequency generation (SFG) spectroscopy analysis revealed the difference in distributions of hydrous species in the Na⁺?depleted and Na⁺?gradient surfaces. The structural information of the thermally‐poled surfaces provides critical insights needed to understand the mechanical and mechanochemical properties of the Na⁺?concentration modified SLS glass surfaces reported in the Part 2 companion paper.     

钙云母可切削微晶玻璃的非等温晶化过程研究

云母基可切削微晶玻璃的应用由于材料强度低而受到限制，钙云母为主相的微晶玻璃强度较高。本文研究了钙云母在CaO—MgO-Al2O3-SiO2-F系玻璃基体中的生长过程。随着温度的升高，板条形钙云母晶体的直径和长径比升高；根据晶体生长动力学分析，钙云母的生长受界面过程控制。掺杂的ZrO2为云母晶体的成核提高戍核位，受氧化锆在玻璃基质中的溶解度影响。其晶粒尺寸不随温度的升高而改变。