Formation of hydrogarnets: Calcium hydroxide attack on clays and feldspars

The reaction of calcium hydroxide with sericite, with shale and with a few igneous rocks gives hydrogarnets, hydrated calcium silicates and free alkalies. In the experiments described, slurries of the hydroxide and the starting materials were boiled (95 °C). Hydrothermal treatment was carried out at 1 MPa and at 2 MPa. The full significance of the findings is unknown but the possible unfavourable influence of these reactions on the durability of concrete is considered.     

Calcium hydroxide attack on feldspars and clays: Possible relevance to Cement-aggregate reactions

The reaction of calcium hydroxide with feldspars in aqueous suspensions at 39°C and also at room temperature gives tetracalcium aluminate hydrates, free alkalies, alkali silicates and hydrogarnets, depending on the type of feldspar. A theory related to cement-aggregate reactions is advanced.     

Measurement of acid attack on phosphate rocks

A continuous analyser of thermometric type was modified and connected to a batch reactor to obtain quick kinetic curves of phosphate rock acid attack. Different kinds of rocks and two acids were tested in the physical conditions where the dissolution velocity is slow (diluted solutions and low temperatures). A mass transfer model, based on calcium diffusion from the rock particle to the liquid bulk, was verified, although at the beginning of the reaction a delay (as yet of unknown origin) appeared as described in the literature.     

利用氢氧化铝和碳酸钙制备六铝酸钙

以工业氢氧化铝和轻质碳酸钙为原料,采用反应烧结法合成了六铝酸钙( CA6),研究了成型压力(分别为50、100、150 MPa)和煅烧温度(分别为1200、1300、1400、1500℃)对CA6性能、相组成和显微结构的影响.结果表明:以150 MPa压力成型,在1500℃保温3h煅烧,可以合成出体积密度达1.49 9·cm-3,常温耐压强度达34.4 MPa的CA6材料.对于1500℃烧后试样,成型压力不会影响试样的相组成和CA6的结晶程度;但随着成型压力的增大,试样中CA6片状晶体的架空程度明显减弱,晶粒尺寸有所减小,厚度逐渐增大.     

Effects of sodium hydroxide and calcium hydroxide on polyester fabrics

The results of a comparison between the effects of sodium hydroxide and calcium hydroxide on poly(ethylene terephthalate) fabrics are presented. Calcium hydroxide can produce weight‐loss effects similar to an aqueous solution of sodium hydroxide. The effects of some treatment variables on weight loss, fiber diameter, bending rigidity, and strength of yarns taken from fabrics are examined. The results are explained in terms of current views of polyester alkaline hydrolysis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 631–637, 1999     

Calcium hydroxide distribution and calcium silicate hydrate composition in tricalcium silicate and β-dicalcium silicate pastes

Pastes of tricalcium silicate (C₃S) and β-dicalcium silicate (C₂S) 23 years old were studied by electron probe microanalysis. In both cases, regions consisting entirely or largely of calcium hydroxide and of CSH were distinguished on a scale of 2–50 μm. The regions high in CSH accounted for 75–80 percent of the whole in the C₃S paste and about 96 percent in the C₂S paste; these values are much higher than those initially occupied by anhydrous starting materials. Within the high CSH areas, no compositional variation was detected that could have corresponded to the so-called inner and outer hydrates. The ratio of mean Ca to mean Si in the high CSH areas was found to be 1.72 for the C₃S paste and 1.78 for the C₂S paste with an exciting beam energy of 10 keV.     

氢氧化镍制备方法的研究进展

综述了近年来氢氧化镍的制备方法，详细介绍了其工艺原理、工艺过程及其利弊。     

Calcium oxide and potassium hydroxide catalysed low temperature methane production from graphite and water Comparison of catalytic mechanisms

An experimental study was carried out to obtain information on the catalytic mechanisms involved in the methanation of graphite using, separately, potassium and calcium as catalysts, and water and/or hydrogen as reactants. The mechanisms for the potassium-catalysed graphite—water reaction appear to be the same in the wide temperature range from 473 to 873 K as indicated by the constant activation energy, 46 kJ mol^?1, found for methane production. The intercalation of potassium into the graphite as a possible step in the methane synthesis has been investigated and ruled out. XPS studies indicate the formation of an active form of more positively charged carbon from graphite when graphite is heated at low temperature in the presence of a calcium catalyst and water vapour. The activation energy for this carbon depolymerization reaction is 68.1 kJ mol^?1. Methane formation occurs only in the presence of hydrogen due to its reaction with the active carbon with an activation energy of 106.6 kJ mol^?1.     

纳米Mg(OH)_2·Al(OH)_3苯甲酸乙酯包复体的制备研究

采用液相共沉淀法首先合成出纳米氢氧化镁和氢氧化铝的复合物Mg(OH)2.Al(OH)3,再制备出纳米Mg(OH)2.Al(OH)3与苯甲酸乙酯的包复体,运用TEM、XRD、TG-DTA研究复了合物及包复体的性能。结果显示复合物的平均粒径为55nm,包复体的平均粒径为75nm。包复体有较高的热稳定性,且均匀分散在有机溶剂中。     

The effect of iron hydroxide on nickelous hydroxide electrodes with emphasis on the oxygen evolution reaction

The electrochemical response of mixed Ni(OH)₂ and Fe(OH)₂ electrodes prepared either by chemical coprecipitation or layer by layer precipitation in alkaline solutions at 25°C was studied. Ni(OH)₂ coprecipitated with Fe(OH)₂ forms a mixed hydrated oxide with specially high catalytic activity towards the oxygen evolution reaction (OER). In layer by layer precipitated electrodes, the catalytic activity for the OER depends on the sequence of precipitation of the hydroxides and there is a loss of efficiency when the inner layer is made of Fe(OH)₂ because of a poisoning of the electrode. Kinetic and mechanistic aspects are discussed. Some long term experiments at controlled potential were also carried out.     

氢氧化镁吸附性能研究

采用氢氧化镁乳液对富含重金属离子废水、印染废水以及海水中的微量硼实施吸附处理。研究结果表明:氢氧化镁对废水中各类重金属离子均有很好的吸附效果,去除率最高达到98%;对印染废水的脱色率与COD去除率分别达到97.5%和80%;对海水中硼的吸附率达到74%。     

不同氢氧化镁对LLDPE性能的影响

采用气泡液膜法制备了疏松型纳米氢氧化镁（LN-MH）,将其和不同氢氧化镁分别填充到线型低密度聚乙烯（LLDPE）中制得复合材料。通过常规力学性能测试、TG、极限氧指数（LOI）和锥形量热仪（CONE）研究了疏松型氢氧化镁（LN-MH）和普通氢氧化镁（C-MH）对LI。DPE性能的影响。结果表明：LN-MH／LLDPE复合材料的拉伸强度、弯曲强度和氧指数均比C-MH／LLDPE有显著的提高;与C-MH相比,LN-MH对LLDPE有更好的阻燃效果和成炭作用,但热稳定性稍差。     

纳米级氢氧化镁的研究进展

文章对国内外纳米级氢氧化镁的研究状况做了阐述,较详细地讨论了纳米氢氧化镁粉体的制备方法及制备过程中应采取的防团聚措施,提出了纳米氢氧化镁材料研究的几点建议。     

羟基及其药剂制取方法研究

羟基是自然界存在的一种原子团簇物质,具有极强氧化能力的天然物质。采用了强电场电离放电方法,在分子层次上加工羟基及其药剂。加工羟基的浓度高达20％以上,制取羟基药剂浓度达到相对质量分数1.6×10~(-5)以上。成为治理赤潮、船舶压载水、水处理以及杀菌、消毒的有效、快速、廉价、无污染和无残留物的绿色理想药剂。     

A study on nickel hydroxide crystallization characteristics

The precipitation characteristics of nickel hydroxide as well as carbonate and sulfide were studied to determine the proper treatment condition of the wastewater induced from nickel-plating industry. When the pH value was maintained higher than 10, the nickel concentrations in the effluent could be kept lower than 5 mg/l. The precipitation of nickel salts in the model wastewater was conducted by alkaline addition, such as the uses of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium sulfide. In case of sulfide treatment, the nickel concentration of treated wastewater showed the lowest value after the removal of precipitates. The change of particle size of the crystal precipitates by the precipitation conditions and precipitants was also investigated. In spite of the various precipitation conditions that were adopted, the change of particle size of the crystal precipitates showed no great differences. The settling rates of the precipitated particles were observed and the free settling period was terminated within 20 minutes. Although the hindered settling as well as bed compaction progressed subsequently, the bed heights were maintained almost the same level after few hours later     

Influence of lithium hydroxide on alkali-silica reaction

Several papers show that the use of lithium limits the development of alkali-silica reaction (ASR) in concrete. The aim of this study is to improve the understanding of lithium's role on the alteration mechanism of ASR.The approach used is a chemical method which allowed a quantitative measurement of the specific degree of reaction of ASR. The chemical concrete sub-system used, called model reactor, is composed of the main ASR reagents: reactive aggregate, portlandite and alkaline solution. Different reaction degrees are measured and compared for different alkaline solutions: NaOH, KOH and LiOH.Alteration by ASR is observed with the same reaction degrees in the presence of NaOH and KOH, accompanied by the consumption of hydroxyl concentration. On the other hand with LiOH, ASR is very limited. Reaction degree values evolve little and the hydroxyl concentration remains about stable.These observations demonstrate that lithium ions have an inhibitor role on ASR.     

Sulfate attack on alkali-activated slag concrete

This paper presents an investigation into durability of alkali-activated slag (AAS) concrete in sulfate environment. Two tests were used to determine resistance of AAS concrete to sulfate attack. These tests involved immersion in 5% magnesium sulfate and 5% sodium sulfate solutions. The main parameters studied were evolution of compressive strength, products of degradation, and microstructural changes. After 12 months of exposure to the sodium sulfate solution, the strength decrease was up to 17% for AAS concrete and up to 25% for ordinary Portland cement (OPC) concrete. After the same period of exposure to the magnesium sulfate solution, the compressive strength decrease was more substantial, up to 37% for OPC and 23% for AAS. The main products of degradation were ettringite and gypsum in the case of Portland cement and gypsum in AAS. OPC samples had significant expansion, cracking, and loss of concrete, while AAS samples were not expanded but cracked in the test. During experiments with the sodium sulfate solution, some increase in strength of AAS concrete was recorded, likely due to continuing hydration.