Chemical surface modification of glass beads for the treatment of paper machine process waters

Adsorption of detrimental contaminants on a solid sorbent is proposed to remove these contaminants from process waters to increase water recycling and reduce effluent loads in the papermaking industry. A self-assembly process of attaching (covalent grafting) cationic aminosilane molecules to glass beads was investigated. The existence and the hydrolytic stability of self-assembled monolayers and multilayers were confirmed by X-Ray Photoelectron Spectroscopy and contact angle measurements. Effects of reaction time and curing on aminosilane layer structures are also discussed. The curing step after silanization seems to be crucial in the hydrophobization of the quaternary ammonium silane coated onto glass beads, and curing could affect the final chemical structure of the ammonium groups of grafted organosilane. Results indicated that modified glass beads have a strong hydrophobicity, which is attributed to the hydrophobic property of the longest carbon chain grafted onto the glass surface. Adsorption of a model contaminant (stearic acid) onto chemically modified glass beads was determined using colloidal titration. Hydrophobic interactions could be the main driving force involved between the long carbon chains of stearic acid and the carbon chains of the aminosilane layers on glass bead surfaces. Finally, self-assembly processes applied onto glass beads may have two promising applications for papermaking and self-cleaning systems.     

动态毛吸法测定纤维及粉末料的接触角研究

本文用动态毛吸法研究了表面处理对纤维浸润性的影响,结果表明碳纤维及聚酯纤维表面经冷等离子体氧处理,浸润性有很大的改善,碳纤维约提高四倍,这是因为等离子氧表面处理过程,将含氧基团羧基,羟基及羰基等引入到表面所致。同时从测得的浸润过程表面自由能改变值△γ,计算出水对纤维的接触角,它与采用接触角测定仪倾斜法所测得的结果基本上一致。从所测得的接触角值也可以看出表面经处理之后,浸润性得以改善。如碳纤维由77°降为63°,聚酯纤维由77°降为52°。此外我们还研究了煤粉和玻璃粉体系对水的浸润性,发现水对玻璃粉的浸润性优于煤粉,前者的浸润接触角为47°、后者则为90°,此接触角值也与采用接触角测定仪由静滴法测得水对片材的接触角相一致。由此可见动态毛吸法可以用于研究纤维及粉末体系的浸润性,而且操作简单易行,测试周期短。      

Ductile streaks in precision grinding of hard and brittle materials

Ductile streaks produced during diamond grinding of hard and brittle materials have aided the subsequent process of polishing. Two novel techniques were used to study the formation of ductile mode streaks during diamond grinding (primary process) of germanium, silicon, and glass. In the first technique, aspheric surfaces were generated on Ge and Si at conventional speeds (5000 rpm). In the second technique, diamond grinding of plano surfaces on glass and Si surfaces using high speed (100,000 rpm) was carried out. Form accuracy, surface finish and ductile mode grinding streaks are discussed in this paper. It was found that resinoid diamond wheels gave more ductile streaks than metal-bonded wheels but better form accuracy was obtained with the latter. Ductile streaks were obtained more easily with pyrex rather than with BK 7 glass thus necessitating very little time for polishing. Ductile streaks appeared in abundance on germanium rather than silicon. Both the novel grinding techniques were used on CNC machining centres.     

钯对钛膜吸氢能力的抗污染作用的研究

为寻求一种防止因表面污染而导致钛膜吸氢能力下降的途径，用表面分析方法检测样品表面状态，用质谱仪测量样品吸氧能力，研究了表面状态和吸氢能力的相互关系。采用在钛膜上淀积钯膜（蒸发或溅射）的方法，可使受碳、氧污染的钛膜吸氢能力得以恢复。这种钯／钛复合结构在吸氢能力上对碳、氧污染并不灵敏。对样品的近费米能级处的占有电子态密度（densityofstate，DOS）的测量证明，凡吸氢能力良好的样品，DOS呈峰形结构。具有抗污染能力的钯／钛结构，其DOS因污染而导致的变化很小，而无抗污染能力的钛膜，其峰形结构受污染作用而消失。这种峰形结构能提供氢分子解离吸附过程中所需的电子。     

Quality of hemodialysis water in a resource‐poor country: The Nigerian example

Hemodialysis (HD) patients are exposed to large volumes of water, separated from patients' blood by semipermeable membrane of dialyzers. Chemical contaminants in poorly treated water impact negatively on quality of life of these patients. This survey was carried out to assess the HD water quality in Lagos, Nigeria. Ten milliliters of feed and treated water from all six HD centers in Lagos were tested for aluminum, copper, zinc, magnesium, calcium using atomic absorption spectrometry; sodium and potassium were tested using flame photometry, fluoride with molecular photoluminescence method; sulfate using turbidimetry, nitrates measured by cadmium column reduction method, chloramines and free chlorine were measured using N, N‐diethyl‐1‐P‐phenylenediamine colorimetric method. Information on sources of feed water, frequency of testing of HD water, methods of water treatment, type of water purification system and maintenance was also obtained. All centers used borehole as main source of water supply. None of the centers met Association for the Advancement of Medical Instrumentation (AAMI) guidelines for most chemical contaminants. Only chlorine (0.48 ± 0.07 mg/L) and potassium (3.9 ± 0.95 mg/L) levels met AAMI standards after treatment. Mean levels of chemical contaminants in treated water were as follows: aluminum 0.04 ± 0.01 mg/L, zinc 0.27 ± 0.08 mg/L, chloramines 0.16 ± 0.03 mg/L, fluoride 1.83 ± 0.40 mg/L, sulfate 117 ± 86.1 mg/L which were mildly elevated; calcium 126.00 ± 22.7 mg/L, sodium 179 ± 25.6 mg/L, and nitrate 70.5 ± 50.8 mg/L, which were markedly elevated; and magnesium 8.3 ± 3.38 mg/L, which was moderately elevated above AAMI recommended levels. HD water quality is poor in our environment. Concerted efforts are required to ensure good quality water for HD.     

Influence of the evaporation rate and the evaporation mode on the hydrogen sorption kinetics of air-exposed magnesium films

It has been shown that the hydrogen sorption properties of air-exposed magnesium films are influenced by the deposition parameters such as the evaporation rate or the evaporation mode used during their preparation. As the evaporation rate increases, the structure of the film tends to be highly oriented along the [002] direction and the kinetics of hydrogen absorption and desorption are faster. Moreover, the hydrogen sorption kinetics of magnesium films prepared with an electron beam source under a high vacuum are faster by almost a factor of two compared to those prepared using resistive heating under low vacuum. These two parameters reduce drastically the activation and the incubation period during hydrogen absorption and desorption, respectively.     

Spectroscopic investigation of sulfonate phthalocyanine to probe enzyme reactions for heavy metals detection

Optical absorption and Raman spectra of the sulfonated copper phthalocyanine (CuTsPc) layer were exploited for detection of cadmium (Cd) contaminants in water. Acetylcholine esterase was immobilized by freely suspending them in calcium alginate microbeads and this gel was then spincoated on the drop cast sulfonated copper phthalocyanine film on a glass substrate to form a bilayer. The inhibition of catalytic reaction between acetylcholine chloride and enzyme due to Cd contaminants was monitored by recording changes in spectra of drop cast CuTsPc as an indicator. The detection limit of cadmium content in water was found to be 1 ppm.     

碳纤维表面性能的研究

通过此表面、接触角、浸润性、表面能和表面基团的测定,本文较系统地研究了碳纤维表面性能。结果表明经处理后的碳纤维表面的浸润性、此表面、表面能与表面基团含量都增加。就浸润性而论,不论对环氧或水的接触角都随氧化处理时间增加而减少,浸润速度随氧化处理而上升,表面能随氧化处理而提高。特别是表面能中极性组份增加得较为显著,这与表面基团分折结果表明表面含氧极性基团随氧化时间增加而增加的结论是相一致的。另外表面基团含量化学分析的结果与XPS分析的结果基本上一致,因此可以用XPS表面基团分析来代替烦杂的化学分析方法。      

微晶碳对镁粉快速纳米化、储氢体系温度的影响研究

将微晶碳和镁粉在H2气氛中反应球磨复合,球磨时间为3h,制备的镁碳复合材料的平均粒度在20~120nm,说明适量微晶碳的引入,在短时间内,可实现镁粉的纳米化。对其进行吸氢性能研究,70Mg30C材料的储氢密度,在8min内可达5.0%(wt),微晶碳含量越高,储氢时间越短。储氢体系温度瞬间升高200℃,得益于微晶碳在球磨中的助磨作用和镁粉吸氢的催化作用。     

Synthesis of Ca–Mg Apatite via a Mechanochemical Hydrothermal Process

Mixtures of calcium and magnesium hydroxides and calcium dihydrogenphosphate in various molar ratios were ground in water with a fine grinding machine, which features multiring grinding media. Mechanochemical amorphization of the mixtures occurs quickly by grinding. The mixtures, after grinding for 5, 20, and 60 min, were then subjected to hydrothermal treatment at 573 K for 24 h. The influence of Mg/(Mg + Ca) molar ratio on the thermal behavior of the mechanically activated powders and the structure of the final products has been investigated. The microhomogeneity of Mg, Ca, and P elements on the samples is enhanced by the mechanochemical treatment. A shift in the X-ray diffraction peaks was observed among the final products with different grinding times, presumably due to a partial substitution of calcium by magnesium.     

山东长清木鱼石食品接触材料钙、铁、镁元素迁移研究

目的通过研究木鱼石作为食品接触材料时,对食品中钙、铁、镁元素的迁移来证实木鱼石是否具有对人体有益的功效。方法在全矿区采样,将木鱼石磨片,采用水性食品模拟液、酸性食品模拟液浸泡法,利用原子吸收光谱仪,对钙、铁、镁元素的迁移进行研究。结果山东长清木鱼石中钙、铁、镁元素等3种主要元素在水性、酸性食品模拟液中均会发生不同程度的迁移。结论山东长清木鱼石主要组成矿物为白云石,木鱼石在水性食品模拟液(蒸馏水)浸泡液以及酸性食品模拟液中都可以迁移出铁、钙、镁,其中酸性食品(体积分数为4%的乙酸)模拟液迁出的钙、铁、镁元素含量远高于水性食品。     

Magnetic mesoporous materials for removal of environmental wastes

We have synthesized two different magnetic mesoporous materials that can be easily separated from aqueous solutions by applying a magnetic field. Synthesized magnetic mesoporous materials, Mag-SBA-15 (magnetic ordered mesoporous silica) and Mag-OMC (magnetic ordered mesoporous carbon), have a high loading capacity of contaminants due to high surface area of the supports and high magnetic activity due to the embedded iron oxide particles. Application of surface-modified Mag-SBA-15 was investigated for the collection of mercury from water. The mercury adsorption using Mag-SBA-15 was rapid during the initial contact time and reached a steady-state condition, with an uptake of approximately 97% after 7 h. Application of Mag-OMC for collection of organics from water, using fluorescein as an easily trackable model analyte, was explored. The fluorescein was absorbed into Mag-OMC within minutes and the fluorescent intensity of solution was completely disappeared after an hour. In another application, Mag-SBA-15 was used as a host of tyrosinase, and employed as recyclable catalytic scaffolds for tyrosinase-catalyzed biodegradation of catechol. Crosslinked tyrosinase in Mag-SBA-15, prepared in a two step process of tyrosinase adsorption and crosslinking, was stable enough for catechol degradation with no serious loss of enzyme activity. Considering these results of cleaning up water from toxic inorganic and organic contaminants, magnetic mesoporous materials have a great potential to be employed for the removal of environmental contaminants and potentially for the application in large-scale wastewater treatment plants.     

Zum Ermüdungsverhalten eines vakuum- und eines elektroschlackeumgeschmolzenen martensitaushärtenden (Maraging-) Stahles (Typ X2 NiCoMo 18 8 5) bei Umlaufbiegung und Rollreibung

The fatigue behaviour of a vacuum- and an electroslagremelted 18% nickel-cobald-molybdenum maraging steel under rotating bending and rolling contact conditions. The endurances of an eletroslag- and a vacuumremelted maraging steel have been compared under conditions of rotating bending as well as under rolling fatigue conditions; with the finishing conditions (grinding and scouring) as additional parameter. Under conditions of rotating bending no significant difference in endurance has been found between the vacuum- and the electroslagremelted material. The same applies for rolling contact experiments under conditions of lubricant starvation. – Under conditions of thick-film lubrucation, however, the vacuumremelted material shows a considerable longer life expectancy than the electroslagremelted material. – Under conditions of rotating bending a scouring finish gives a shorter life expectancy than a grinding finish. Under conditions of rolling contact fatigue the opposite is found. – The effects are discussed in terms of structure and surface topography, special attention has been paid to structural changes that occur in heavily strained areas.     

Partial-Ductile Grinding and Reduced Polishing for Ophthalmic Glass Molds

Plastic lenses are manufactured by the classical replication technique where two glass molds are assembled in a jacket and liquid plastic is injected into it. The glass molds are fabricated conventionally by fracture mode grinding, followed by lapping, and Finally polishing. This paper presents an alternative fabrication process using partial-ductile grinding, followed by a short polishing in an industrial polishing machine. The partial-ductile surfaces were generated on a laboratory ultra-precision machine using Fine grit resinoid-bond diamond wheel and they were compared to the glass molds prepared by industry. The results showed that (i) as much as 100% ductile streaks (fully ductile grinding) can be obtained in the ultra-precision ground surface and (ii) a net saving of 55 seconds polishing time if only 60% of ductile streaks on the glass mold surface was used prior to polishing.     

Zum Einfluss von in Flüssigkeiten unter Druck gelösten Gasen auf Grenzflächenspannungen und Benetzungseigenschaften

Measurements of interfacial tensions of water and ethanol in dense carbon dioxide up to 10 MPa and 373 K were performed. Also, in order to predict the wettability of these liquids on teflon and glass surfaces in the presence of carbon dioxide, contact angles between these liquids and both surfaces were determined under the same conditions of pressure and temperature. The interfacial tension were measured according to the pendant drop method. A mathematical derivation for the evaluation of the interfacial tension according to the geometry of the pendant drop and the difference of the density between the phases is presented. The contact angle determinations were performed using both the static and the dynamic method. The results show that because of the solubility of carbon dioxide in the liquids, the measured interfacial tensions are much lower than the interfacial tension of the pure substances. The interfacial tension appears as a function of only the density of CO₂ above its critical temperature [1]. Even though the solubility of carbon dioxide in the liquid phase affects the interfacial tension, such a clear relation between these variables, like the one between the interfacial tension and the density of carbon dioxide, cannot be observed. The excess concentration on the interphase, as a measurement of adsorption according to Gibbs, was calculated for both systems. The contact angle of water on teflon surface increases with pressure until total non wetting is reached. On the other hand, the contact angle of ethanol decreases with the increasing pressure until spreading occurs. The same phenomena was noted for the wetting characteristic of water on glass surface. The contact angle of water increases as pressure increases. Ethanol spreads totally on the surface of glass at all evaluated pressures. With the dynamic method, contact anglesgreater than the ones obtained with the static method were measured.     

Reactive mechanical grinding of magnesium in hydrogen and the effects of additives

The use of reactive mechanical grinding (MG under H₂) of magnesium powder improves the hydrogen sorption properties. The hydrogenation of Mg starts in situ during the milling process, thus circumventing the activation procedure that is generally required for Mg. The effects of the addition of various elements or compounds have been studied. The hydriding is determined to be a two-step process: nucleation and diffusion. A direct relationship exists between the nucleation duration and the specific surface area of the magnesium powder. A critical milling time exists up to which the diffusion process is improved and above which no more improvement is observed (the maximum internal stress in the powder is also reached at this critical time). The diffusion is controlled by the number of crystallites per particle that can be reduced by increasing the milling time up to 10 hr. The addition of Co (catalyst), YNi (hydrogen pump), or oxides (abrasive elements and nucleation centers) leads to an improvement of the hydrogen sorption properties (but a strong dependence upon the milling time is reported). Finally, the sorption properties of these mixtures are comparable with those reported for MgH₂-metal mixtures.     

固体储氢材料的研究进展

论述了目前几种主要固体储氢材料的研究进展,包括金属基合金材料(镁系合金、稀土系合金、钛系合金和锆系合金)、碳基材料(活性炭、石墨纳米纤维、碳纳米纤维和碳纳米管)、玻璃微球、配合物以及金属有机框架物。通过比较各种材料储氢的机理与方式、吸放氢的温度与压力、循环寿命,分析了其优缺点,并展望了固体储氢材料未来的发展趋势,认为开发安全稳定高效的复合储氢材料、实现固体储氢材料的工业化制备是未来储氢材料研究的新方向。     

球磨工艺对太阳能电池正面银浆用玻璃粉的影响

研究了球磨时间、固液比、料球比和磨球尺寸与级配对太阳能电池银浆用玻璃粉粒度及形貌的影响,并将其与一定比例的银粉、有机载体配制成导电银浆,印刷、烧结在硅片上形成晶体硅太阳能电池片,测试了其电学性能。实验结果表明,将玻璃粉用作正面银浆粘接剂时,其最佳的行星球磨工艺参数:球磨时间为4h,固液质量比为1∶0.8,料球质量比为2.5∶1,磨球级配w(大)∶w(中)∶w(小)为3∶2∶1。此时,制备的多晶硅太阳能电池串联电阻为7.15mΩ,光电转换效率可达16.56%。     

Degassing of magnesium alloy by rotating impeller degasser: Part 1 – Mathematical modelling

Abstract

A mathematical model was used to simulate the removal of hydrogen from magnesium alloy by a rotary impeller. It has been shown that the degassing efficiency is mainly dependent on the total surface area of the inert gas bubbles that is related to the rotation speed and the gas flowrate as well as the design of the impeller. An oxygen/water system was used to determine the total surface area of the inert gas bubbles experimentally. Finally, degassing experiments were carried out on magnesium melt to verify the mathematical model. Excellent agreement was obtained between the model predicted and the measured degassing efficiency. It was concluded that this model and the oxygen/water system are suitable to predicate the removal of hydrogen from magnesium alloy by the rotary impeller, and are also useful to the design of the impeller and the research of the effect of the processing parameters.     

镁含量对MmNi5-x(CoAlMn)x/Mg复合储氢合金吸氢性能的影响

借助扫描电镜、X- ray及吸氢性能测试装置研究了镁含量对机械合金化制备的 Mm Ni5- x ( Co Al Mn) x/Mg纳米晶复合储氢材料的性能的影响。结果表明 ,随着镁含量的增加 ,合金的活化性能表现出差 -好 -差的变化趋势。当镁含量达到50 wt%时 ,材料无法被活化。镁含量对吸氢量也有影响 ,具体表现为 ,随着镁含量的增加 ,材料的吸氢量增加。