Ionization Processes in Polar Solution of Tryptophan at 77° K

The triplet absorption spectrum of tryptophan in ethylene-glycol/water glass at 77°K has been registered. It is demonstrated that light of wavelength 250 nm produces trapped electrons by a two-photon process in this system. In both UV- and X-ray-induced ionization the probability that an ejected electron will recombine with its mother ion is around 0.5. Bleaching with visible light causes the trapped electrons to react with the solvent and there is also a considerable degree of retrapping. The retrapping becomes more probable when the temperature increases.     

Behavior of Glass Fibers in Strong Acidic and Alkaline Media

The properties of basaltic, glass wool, quartz, and E-glass fibers were investigated under strong acid (HF:H₂O=l:3, HF:H₂O=1:1, 10% H₂SO₄+3% HF:H₂O=1:1) and alkaline (1 N NaOH + 1 N Na₂CO₃) treatment. The multiple-oxide fibers were found to be composed of several layers which exhibit different morphology and composition. These findings are in accordance with some proposals in the literature.     

Models and Experiments for Sodium Evaporation From Sodium-Containing Silicate Melts

Universal simulation models based on (a) validated mass transfer relations and (b) thermodynamic modeling procedures for glass melts are developed to predict the evaporation rates of volatile species from a large range of glass melt compositions. Depending on the glass composition, temperature of the surface of the melt, local composition of the atmosphere, exposure time of a melt layer to the combustion atmosphere, and local gas velocities above the glass melt surface, the evaporation rates of volatile species can be estimated. Laboratory-scale transpiration evaporation experiments have been used to study evaporation kinetics, to derive mass transfer relations, as well as to validate the sodium evaporation modeling results for sodium-silicate melts as well as for soda-lime-silicate melts. In these investigations, the molten sodium-silicate and soda-lime-silicate melts are exposed to atmospheres of flowing gases with controlled composition and gas flow rates. In a humid atmosphere for example, sodium mainly evaporates as NaOH. From the measured NaOH evaporation rates and the mass transfer relations, the NaOH vapor pressures in equilibrium with the molten glass at prevalent temperature and furnace atmosphere composition were derived. The NaOH vapor pressures are assumed to be in equilibrium with the glass melt composition at the surface of the melt. During the evaporation test, the Na₂O surface composition will change due to depletion. This leads to equilibrium vapor pressures decreasing with time, reflecting the changing chemical activity at the glass melt surface. The results of evaporation tests for sodium-disilicate and soda-lime-silicate glass melts are shown. Chemical activities derived from these measurements are compared with the results of thermodynamic modeling, using a method based on a glass melt from ideal mixtures of associate (stoichiometric) species of structural compounds with known thermodynamic properties.     

Characterization of Insoluble Layers Formed by NaOH Attack on the Surface of a ZrO2-Containing Silicate Glass

The durability of an alkali-resistant glass containing ZrO₂ in NaOH solution was studied by scanning electron microscopy. Insoluble Zrrich reaction-product layers ∼1 to 3 μm thick were observed on the surface of glass which had been soaked for 25 d in 2N NaOH at 95°C. In some cases the layer seems to be an adherent film, but in others it adheres loosely to the glass surface and does not seem to effectively block alkali attack .     

A Novel Sodium Silicate Fluoride Solution and a H2 Gas Formed by a Reaction Between Si and an Aqueous Solution of NaOH and NaF

Oxidation of Si in an alkali solution has attracted much attention to produce hydrogen gas from Si wastes. It was found that hydrogen gas was generated from Si in NaOH and NaF solution with more than 10 times reaction rate than in the NaOH solution. The reaction by-product was a sodium silicate fluoride, Na _{x + z} Si _y O_{2 y + x /2}F _z solution, and it proved to transform to a glass foam by boiling. The Raman spectrum suggested that the silicon and oxygen atoms in the silicate anions were arranged in a sheet-like structure. This may affect the behavior to form the glass foam.     

Microfabrication of U-Shaped Grooves on the Surface of BaO–TiO2–GeO2 Glass by YAG Laser Irradiation and Selective Chemical Etching

A combination technique of Nd:YAG laser (wavelength: 1064 nm) irradiations and chemical etchings was applied to fabricate microsize U-shaped grooves on the surface of CuO-doped BaO–TiO₂–GeO₂ glass, and chemical etching behaviors were examined by using a confocal scanning laser microscope. Continuous-wave Nd:YAG lasers with a power of 0.7–0.8 W were irradiated onto the glass surface and scanned at a speed of 10 μm/s, inducing structural modified lines with refractive index changes. The chemical etching rates for the refractive index changed lines in a nitric acid solution (1 N HNO₃) were larger than those for the base glass (nonirradiated part). The etching profile was changed gradually from W-shaped to U-shaped grooves with increasing etching time. The sharp bending lines with an angle of 150° and the cross-linked lines were also smoothly etched. The U-shaped grooves with a surface covered by nonlinear optical Ba₂TiGe₂O₈ crystals were formed by the crystallization of etched samples. This study proposes that the patterning of microchannels with optical functional surfaces is possible on the glass surface using the present technique.     

纳米氧化锌的室温合成及表征

文章以醋酸锌、氯化锌和氢氧化钠为原料,在室温下成功制备了氧化锌纳米晶。制备的氧化锌样品用x射线衍射仪、透射电镜、荧光光谱仪等进行表征。XRD结果表明,制备的氧化锌样品为六方纤锌矿结构且具有好的结晶度;从透射电镜照片可以看出,氧化锌颗粒分散性较好,平均粒径在6～10nm;从紫外吸收光谱可以看到,在200-380nm具有很强的紫外吸收,在400-800／lm的可见光区吸收则比较弱;在340nm的激发光下,氧化锌呈现出较好的蓝光和绿光发光效应。     

Use of glass waste as an activator in the preparation of alkali-activated slag. Mechanical strength and paste characterisation

The alkaline activation of aluminosilicates yields alkaline cements, eco-efficient alternatives to ordinary Portland cements. Alkaline cements and concretes exhibit highest strength and longest durability when activated with a solution of alkaline silicate hydrates (waterglass). To obtain these alkaline silicates, however, an aqueous solution of the proper proportion of carbonate and silica salts must be heated to temperatures of around 1300 °C. The present paper explores the feasibility of using urban and industrial glass waste as a potential alkaline activator for blast furnace slag (AAS).AAS pastes were prepared with three activators: waterglass, a NaOH/Na₂CO₃ mix and the solutions resulting from dissolving glass waste in NaOH/Na₂CO₃. Mechanical, mineralogical (XRD, FTIR) and microstructural (porosimetry, NMR and SEM/EDX) trials were conducted to characterise the pastes obtained.The findings proved the feasibility of using glass waste to alkali activate slag. Treating glass waste with NaOH/Na₂CO₃ (pH = 13.6) favours the partial dissolution of the Si in the glass into its most reactive monomeric form.The solutions resulting from the treatment of glass waste act as alkaline activators, partially dissolving vitreous blast furnace slag. The composition and microstructure of the reaction products identified in the two types of paste were similar. Strength and microstructural development in the pastes activated with glass waste were also comparable to the parameters observed in AAS pastes prepared with conventional activators.     

粉煤灰地质聚合物凝结时间的研究

本文研究了水量、碱量、水玻璃量和矿渣对粉煤灰(FA)地质聚合物凝结时间的影响.用扫描电子显微镜(SEM)对样品微观形貌进行了表征,用核磁共震(~(29)SiNMR)对激发剂的结构进行了表征.结果表明:H_2O/FA比对凝结时间影响较大,当H_2O/FA比从0.29增加到0.36,终凝时间由120 min增加到280 min;NaOH/FA比对凝结时间和抗压强度的影响一致,它们均随NaOH/FA比的增加而提高,当NaOH/FA比为0.1时,终凝时间最长为200 min,抗压强度最高为70 MPa;Na_2SiO_3/FA比对地质聚合物凝结时间影响不大;加入矿渣使凝结时间明显缩短.粉煤灰地质聚合物的凝结时间可以通过H_2O/FA质量比、NaOH/FA质量比和加入矿渣进行调节.     

Perfume‐containing polyurea microcapsules with undetectable levels of free isocyanates

Core‐shell polyurea microcapsules with a 40% fragrance load were prepared by interfacial polymerization of guanidine and a technical polyisocyanate prepolymer containing mainly the biuret trimer derived from hexamethylene di‐isocyanate (HDI). Residual free polyisocyanates were still present at a level slightly above 100 mg NCO functional group per kg as determined by liquid chromatography hyphenated with tandem mass spectrometry of HDI and of its biuret trimer. This level was decreased by a factor of about 10 when the polymerization process was allowed to proceed for a longer time and by a factor of about 500 when guanidine or NaOH were added to the microcapsule suspension to act as scavengers. In these cases, polyisocyanate conversion was observed to proceed for about one month when the microcapsules were stored at room temperature before reaching a plateau at a level below 1 mg NCO/kg. Overall, ammonia was the most efficient polyisocyanate scavenger as no residual HDI biuret trimer and only less than 2 μg NCO/kg as HDI were detected at the end of the process, a level which had dropped below the limit of detection of 0.25 μg NCO/kg after about 40 days of aging at room temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Relation of Dissolved Nitrogen to Phototropy of Reduced Silicate Glasses

Soda-silica glasses melted under strong reducing conditions (graphite crucible) contain the precursor of a 570-nm color center. Glasses thus prepared under an N₂ atmosphere are readily colored by exposure to ultraviolet light; the uv-generated color fades rapidly at room temperature, giving phototropic response. However, with glasses melted under N₂-free atmospheres (for example, Ar), this phototropic response is greatly attenuated or absent. The precursor of the 570-nm center evidently results from strong reduction of the glass independent of the covering atmosphere, since X irradiation generates the same characteristic optical absorption in glasses melted under both N₂ and Ar. For compositions melted under N₂, the amount of N dissolved correlates positively with increasing SiO₂ content and phototropic response. The dissolution of N markedly affects the uv absorption of otherwise "clean" glass. An N-free reduced soda-silica glass exhibits essentially the same uv absorption as a similar oxidized glass. However, as N dissolves in the glass, the uv cutoff moves to longer wavelengths. The phototropic response of reduced glasses under long-wavelength uv light is greatly enhanced by incorporation of europium. Again, an N₂ atmosphere during melting yields improved phototropic response. Dissolved N lowers the dissolved H₂O content and increases the concentration of Eu in the lower valence state (Eu²⁺).     

Effect of Test Environment on Stress-Corrosion Susceptibility of Glass

The stress-corrosion susceptibility of abraded and acid-polished soda-lime and borosilicate glasses in test environments of 6N NaOH, distilled water, and 6N HCI was measured by dynamic fatigue techniques. Dynamic-fatigue data for these glasses agree well with crack-velocity data for the water and 6N NaOH environments. The lack of agreement in the 6N HCI environment suggests that the failure mechanism for glass in HCI is not simply crack propagation by stress corrosion. The agreement in failure predictions based on strength and crack-velocity data in 6N NaOH and water suggests that either set of data may be used for effective design calculations; however, caution should be used when basing strength calculations on crack velocity data in 6N HCI.     

Alkali Durability of Oxynitride Glass Fibers

Oxynitride glass fibers were drawn from the melt in N₂ atmospheres. The fibers were tested for their alkali durability in 10% NaOH at 96°C for 6 h. The durability is reported as weight loss in mg/cm². The photomicrographs of the fibers before and after testing are presented. Calcium silicate oxynitride fibers have good durability because of a protective surface layer of Ca(OH)₂. Yttria-containing glasses have the best durability among the compositions reported here.     

Observation of photocurrent generation in electrodeposited zinc oxide layers

Wurtzite zinc oxide (ZnO) films with band gap energy of about 3.3 eV were deposited onto conductive substrates by electrodeposition from a simple aqueous zinc nitrate solution at 335 K. The films showed optical transmission around 70% in the visible light region. The electrical resistance showed a strong dependence on cathodic potential. The decrease in electrical resistance could be observed with light irradiation irrespective of the cathodic potential and was attributed to the excitation of electrons from valence band to conduction band by light with wavelength below 375 nm. A photocurrent of about 0.10 A was generated for a cell composed of Ag electrode/Au/ZnO/NESA glass substrate under conditions of irradiation by sunlight.     

Studies on the anodic and cathodic polarization of amalgams—V. the behaviour of tin amalgams in alkaline solutions

Tin-amalgams of varying concentrations were oxidized galvanostatically in 0·01, 0·10 and 2·00 N NaOH solutions at 25°C. For each amalgam and solution composition a number of constant polarizing currents were used and cyclization was repeated until the oxidation (reduction) features of the amalgam became apparent. Two different oxidation patterns were distinguished. The first describes the behaviour of all amalgams in 0·01, 0·1 N NaOH, and of concentrated amalgams in 2 N NaOH, and the second for the behaviour of dilute tin amalgams in 2 N NaOH solutions.     

Nanoindentation of Soda Lime–Silica Glass: Effect of Loading Rate

Structural and mechanical reliability of glass for both conventional and advanced applications is determined by the rate at which it can deform and sustain externally applied static or dynamic strain at the microstructural length scale. Hence, a large number of nanoindentation experiments were conducted on a thin (∼300 μm) commercial soda lime–silica glass with a 150 nm radius Berkovich tip at a constant load of 10,000 μN as a function of variations in the loading rates in the range of 10–20,000 μN/s. The results showed that the nanohardness of the soda lime–silica glass increased by as much as 74% as the loading rate was increased from 10 to 20,000 μN/s. Further, the presence of serrations in load–depth plots and deformation band formations inside the nanoindentaion cavities were more vividly observed in the nanoindentation experiments conducted at lower loading rates rather than those conducted at higher loading rates. These results are explained in terms of shear stress acting underneath the indenter as well as the time scale of interaction between the nanoindenter and the weak links at local microstructural length scale, which owe their origin to the subtle variations in the composition of the given glass.     

Yttrium-Silicon-Aluminum Oxynitride Glass Fibers

Fibers were made from Y-Si-Al-O-N glasses previously shown to have excellent mechanical properties and outstanding water corrosion resistance. Fibers of glasses containing, respectively, 3.2 and 6.6 wt% N were pulled free-hand in air and from glass rods in N₂ Continuous fibers (up to several kilometers long) of the former glass were melt-drawn in N₂ while being wound in air outside of the glass-melting furnace. The fibers, some as small as 10 μm in diameter, retained the desirable properties of the bulk glass.     

不同碱介质对合成硅基MCM-41的影响

研究了在较高的硅与表面活性剂摩尔比(10)体系中,采用不同的碱介质(氨水、乙二胺、三乙醇胺／NaOH)来合成MCM-41。通过XRD,N2吸附-脱附等表征手段,分析了不同碱介质体系对制备MCM-41的影响,并分别与NaOH介质中合成的MCM-41进行比较。结果显示,弱碱介质(NH3,EDA)有利于提高MCM-41的热稳定性;而采用混合碱介质(三乙醇胺／NaOH),则可在一定程度上改善MCM-41的水热稳定性,但随着三乙醇胺量的增加,材料的孔径会相应的减小。     

Evaluation of locally available amorphous waste materials as a source for alternative alkali activators

The production of alkali-activated materials with excellent mechanical performance requires the use of water glass, which has a significant carbon footprint. Such materials can have a lower carbon footprint if we replace water glass with alternative activators sourced from waste. In this study, we assessed the suitability of locally available amorphous waste materials (stone wool, glass wool, bottle glass and cathode-ray tube glass) as a source for the preparation of alternative alkali activators. We quantified the amount of silicon and aluminium dissolved in the activator solutions via inductively coupled plasma-optical emission spectrometry. The alternative activators were then used to produce alkali-activated fly ash and slag. The compressive strength values of alkali-activated fly ash specimens upon the addition of NaOH, water glass and the most promising alternative activator were 38.98 MPa, 31.34 MPa and 40.37 MPa, respectively. The compressive strength of slag specimens activated with alternative activators with the highest concentration of dissolved silicon (21 g/L) was, however, 70% higher than the compressive strength of slag specimens activated with only 10 M sodium hydroxide. The compressive strength of slag specimens with the addition of the most promising alternative activator was significantly lower (3.5 MPa) than the compressive strength of those that had been activated by commercial water glass (34.3 MPa).     

Effect of geothermal waste on strength and microstructure of alkali-activated slag cement mortars

Mortars of blast furnace slag replaced with 10% of a geothermal silica waste were cured for 90 days. The binder was activated by 6 wt.% Na₂O equivalent of NaOH and water glass. The presence of the silica enhanced the formation of hydration products as shown by nonevaporable water (NEW) results. Backscattered electron images indicated that the microstructures of blended slag had less porosity than those of neat slag mortars and the interfacial zone between aggregate and hydration products was dense and of homogeneous composition similar to the matrix of hydration products. The main hydration products were C-S-H and for NaOH a hydrotalcite type phase was found as finely intermixed with the C-S-H.