Microwave absorption and thermal properties of coral-like SiC aerogel composites prepared by water glass as a silicon source

As a heat-resistant wave-absorbing material,silicon carbide(SiC)aerogel has become a research hotspot at present.However,the most common silicon sources are organosilanes,which are costly and toxic.In this work,SiC aerogels were successfully prepared by using water glass as the silicon source.Specifically,the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol–gel process,and the effect on SiC aerogel microwave absorption properties was investigated.The SiC aerogels prepared with Si:C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity,with a minimum reflection loss value of-46.30 dB at 12.88 GHz and an effective frequency bandwidth of 4.02 GHz.They also have good physical properties,such as the density of0.0444 g/cm^(3),the thermal conductivity of 0.0621 W/(m·K),and the specific surface area of 1099 m^(2)/g.These lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.

STUDY ON THE MUTUAL SOLUBILITY OF WATER GLASS AND WATER SOLUBLE ORGANIC BINDER

The careful studies have been made into the mutual solubility of water glass and water soluble organic binder in this paper, By means of many experiments, it has been found that water soluble polymer is able to be evenly soluble in water glass, and certain valuable conclusions have been concluded.

Preparation and Characterization of CA-MA Eutectic/Silicon Dioxide Nanoscale Composite Phase Change Material from Water Glass via Sol-Gel Method

This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon dioxide（nano-SiO_2） serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, Fourier-transform infrared（FT-IR） spectroscopy and polarizing microscopy（POM）. It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m^（-1）·K^（-1） by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.

Influences of SiO2/Na2O Molar Ratio on Aging and Chemical Modification of Water Glass

In this paper, the content of water glass before and after adding modifying agent was measured by Trimethylsilyl-gas-chromatography. The experimental results showed that different modulus of water glass could generate different content of mono-silicate acid and oligomeric silicate acid in water glass. After a period of storage, different modulus of water glass led to decrease of silicate content at different levels. Because higher content of Na2O in water glass tended to incur the alkaline polymerization, the occurrence of depolymerization of silicate species would lead to an increase of oligomeric silicate species, resulting in a drawback of silicate species content after a period of storage. And contrary to that, lower content of Na2O in water glass tended to incur the acidic polymerization. When the modifying agent was added to the newly made water glass, the amount of mono-silicate acid and oligomeric silicate acid also decreased. In modified water glass, the change of each silicate acid species was less than that in unmodified water glass. These results showed that the modifying agent retarded the aging of water glass. It had remarkable significance on the theory and practical application of water glass chemistry.

Recycling water glass from wet reclamation sewage of waste sodium silicate-bonded sand

Wet reclamation of waste sodium silicate-bonded sand produces much alkaline sewage and causes pollution. Recycling water glass from wet reclamation sewage of the waste sodium silicate-bonded sand can solve pollution issues and generate economic benefits. In this work, the wet reclamation sewage was filtered, and the filtrate was causticized with a quicklime powder to produce a lye. The effects of causticization temperature, causticization time, and the amount of quicklime powder on the causticization rate were studied. The lye was used to dissolve the silica in the filtration residue to prepare a sodium silicate solution. The effects of the mass of filtration residue, dissolution temperature, and dissolution time on sodium silicate modulus were studied. Finally, the recycled water glass was obtained by concentrating the sodium silicate solution, and the bonding strength of the recycled water glass was tested. The results showed that the causticization rate could be improved by increasing the amount of quicklime powder, causticization temperature, and causticization time, and the highest causticization rate was above 92%. Amorphous silica in the filtration residue dissolved in the lye. Increasing the amount of the filtration residue, dissolution temperature, and dissolution time could improve the sodium silicate modulus. The bonding strength of the recycled water glass was close to that of commercial water glass. The recycled water glass could be used as a substitute for the commercial water glass.

Hydrothermal Dissolution of Opal in Sodium Hydroxide Lyes for the Synthesis of Water Glass

Common opal was dissolved in NaOH lyes in rotating autoclaves. The starting material was characterized by X-ray diffraction and adsorption spectroscopy, thermal and chemical analysis, electron and atomic force microscopy. The opal proved to be an Opal-CT with a microstructure consisting of microcrystalline tridymite, traces of low-quartz, and amorphous parts built up by random packings of size distributed amorphous silica colloids. The dissolution conditions have been inspired by the technological process of hydrothermal water glass synthesis by dissolving silica. Temperature and time of the dissolution process as well as initial molar SiO2:Na2O (Rm) ratios of the starting materials were varied systematically. The particle size of the samples was varied, too, but due to the nanoscopic microstructure without greater impact on dissolution kinetics. The process products were analyzed chemically. Additionally, some of them were characterized by X-ray diffraction, viscosimetry and dynamic light scattering. Already after short dissolution times, water glasses with quite high silica concentrations of up to 27 wt.% and SiO2:Na2O ratios of up to 3.7 were obtained. At longer dissolution times low-quartz and analcime precipitated and the SiO2 contents were reduced to about 22 wt.% and Rm to about 2.7. The silica contents in equilibrium with low-quartz were almost independent on temperature.

Development of Modified Glasses by Transparent, Functional Hybrid Sol-Gel Nano-Ceramic Coatings, a Comparative Study

This paper concentrates on the development of glasses with self-cleaning surfaces exhibiting high water contact angles. In this study, we prepared super-hydrophobic nano-ceramic coated glass based on titania & silica using simple sol-gel & dip coating methods and studied the best composition of the coatings by altering ratios of titanium tetraisopropoxide (TTIP)/tetraethyl orthosilicate (TEOS) with different homogenizing agents. We characterized the coatings by surface roughness measurement, percentage of optical transmission, static contact angle, near-infrared (NIR) transmission, and diffuse reflectance. The fabrication of coatings on glass substrates played an important role in increasing the water contact angle of about 95° and visible & NIR transmission of about 90%. We compared our modified glass substrate with commercial low emissivity (Low E) glass using X-ray diffraction (XRD) analysis, which showed pure amorphous surface claiming excellent wettability and thus the prepared glass substrate could have a variety of applications in different fields.

Test for the effects of three surfactants on the penetration ability of the calcium chloride and water glass Solutions in dust

By using a downward penetration testing device, a large number of experiments were made to investigate the effects of surfactants (sodium succinate, sodium dodecyl sulfonate and dodecyl benzene sulfonic acid sodium salt) on the penetration ability of the calcium chloride and water glass solutions in four dust samples. The experimental results showed that the surfactants can enhance the penetration ability and decrease the surface tension of the calcium chloride and water glass solutions in great extent. After adding the surfactants in 0.2—0.6 wt.% to the solutions of calcium chloride and water glass in 5—25 wt.% respectively, the largest percent of penetration ability increases to 28% more. Among the three surfactants, the size of their effects on the penetration ability of calcium chloride and water solutions in the dust samples is dodecyl benzene sulfonic acid sodium salt, sodium dodecyl sulfonate and sodium succinate.The achieved conclusions are great significant for calcium chloride and water glass to be applied in the field of soil stabilization and raising dust control.

Effect of Water Washing Pre-treatment on the Properties of Glass-ceramics from Incinerator Fly Ash Using Electronic Arc Furnace

Production of glass-ceramics by sintering the molten slag obtained from electric arc furnace treatment of fly ash was investigated. The effect of washing pretreatment prior to melting the fly ash on the microstructure and properties of the glass-ceramics was examined. The results show that washing pretreatment of fly ash can decrease alkali metal chloride and increase network former in fly ash, which results in the increase of peak crystallization temperature of parent glass and strengthening of properties of bending strength and chemical stability of the glass-ceramics. The optimal heat treatment temperature for parent glass of washed fly ash is 1 173 K, at which the crystalline phase of glass-ceramics is composed of gelignite （Ca2A12SiO7） and akermanite （Ca2MgSi207）. Glass-ceramics produced at optimal heat treatment temperature are excellent in term of the physical and chemical properties and leaching characteristics, indicating attractive potential as substitute of nature materials.

Bulk metallic glass rings prepared by a modified water quenching method

Bulk metallic glass rings have the potential applications as annular gasket and active solder in special fields. The bulk metallic glass ring of ZГ41.2Ti13.8Cu12.5Ni10.0Be22.5 with the outer diameter, the inner diameter, and the thickness of 38, 36, and 5 mm, respectively, was prepared by using a special shaped quartz tube water quenching method. The mechanical properties along the whole cross section were investigated by a nanoindentation method, and no evident variation of the Young＇s modulus and hardness was found, further indicating the single amorphous structure. Amorphous ring and tube-shape parts with different dimensions can be produced by this method.

Performance of Water in Glass Evacuated Tube Solar Water Heater under Kenya Climatic Condition

Solar water heaters which provide a cost-effective and environmental friendly approach to hot water generation are in widespread application. Evacuated tube solar water heaters perform better than flat plate solar water heaters as a result of their greater surface area exposed for sunlight absorption. Water-in-glass evacuated tube solar water heaters are widely used as compared to heat-pipe solar water heaters due to their short payback periods. In this study, the performance of water-in-glass evacuated tube solar water heater is investigated through experiments under the climatic conditions in Kenya. The results revealed a daily efficiency range of 0.58 - 0.65 and a daily final outlet temperature greater than 55°C given an initial temperature of 25°C.

The Mixed-Alkali Effect on The Resistance of Glass to Water

Based on the composition of float glass, the resistance of glassto water, in which a small amount of K_2O(0-1.0 wt/100)wassubstituted for equivalent amount of Na_2O, was investigated by meansof glass grains testing. The components extracted from the glass andtotal alkalinities in extraction solution were de- termined by atomicabsorption spectroscopy and neutralizing method, respectively. Thecomposition of the glass was 14.4 K_2O+ Na_2O, 4.0 MgO, 8.2 CaO, 1.4Al_2O_3, 72.0 SiO, and the minimum extraction radio of oxides(maximum durability)occurred at a K_2O/Na_2O radio of 0.051(byweight)due to the presence of the mixed- alkali effect.

矿粉-再生微粉-水玻璃旧砂超细粉磨协同制备地聚合物试验研究

为研究矿粉-再生微粉-水玻璃旧砂超细粉磨协同制备地聚合物的可行性,开展了粉磨参数、不同再生微粉掺量、不同粉磨细度,不同赤泥掺量下的地聚合物力学性能、耐久性能、重金属浸出试验研究。结果表明:最佳粉磨参数为振动磨填充率40%,料球比1∶12;最佳粉磨细度700 m~2/kg;在此基础上,地聚合物基材最佳配比为矿粉70%,再生微粉20%,水玻璃旧砂微粉10%,其中激发剂的最佳配比(占基材总质量)为P·O52.5水泥15%,赤泥2.5%,脱硫石膏2.5%。铜、铅、镍、锌、镉重金属的浸出率都在0.2%以内。

粉煤灰基地聚合物的制备及其性能研究

以低钙粉煤灰为硅铝原料制备了地聚合物胶凝材料,研究了激发剂种类和掺量对地聚合物抗压强度的影响,以及产物对Cr^(3+)和Pb^(2+)固化效果。结果表明:当水玻璃掺量为15%,脱硫石膏掺量为7%时,所制得地聚合物抗压强度最高,3 d、 7 d、28 d龄期抗压强度分别为19.8 MPa、32.5 MPa和53.5 MPa;地聚合物对重金属离子Cr^(3+)和Pb^(2+)的固化效果均较好,其在去离子水和硫酸硝酸混合酸液中的浸出量均远低于国标限值。

组合羟肟酸下方解石和萤石中浮选氟碳铈矿的分离机理

苯甲羟肟酸(BHA)和辛基羟肟酸(OHA)以及二者组合羟肟酸(BHA+OHA)下,对氟碳铈矿、方解石、萤石三种矿物进行了浮选研究。通过红外光谱分析、总有机碳和紫外光谱吸附量测试和XPS分析研究了羟肟酸类在矿物表面的作用机理。结果表明:在pH=9.5、组合捕收剂(n(BHA)∶n(OHA)=2∶1)浓度为3×10^(-4) mol/L和盐化水玻璃3×10^(-3) mol/L条件下,氟碳铈矿、方解石和萤石的回收率分别为89.8%、18.5%和13.7%,人工混合矿REO品位由28.90%提升至55.41%,氟碳铈矿的回收率为80.41%,与方解石和萤石实现较好分离;组合捕收剂(BHA+OHA)在三种矿物表面发生共吸附,且组合捕收剂中每种药剂的吸附率大于相同浓度的单一药剂;盐化水玻璃阻碍捕收剂在方解石、萤石表面的吸附对捕收剂在氟碳铈矿表面吸附无影响,可以达到抑制方解石和萤石的目的,实现氟碳铈矿的选择性浮选。

超深缝洞型碳酸盐岩储层超低密度钻井液技术

塔里木油田压力系数低于1.0的超深井碳酸盐岩低压储层常发生钻井液失返性井漏,其平均井深超过6000 m,井控风险极大,除了强钻再无更好手段,往往只能提前完井。为提升超深井水平段延伸能力,研究人员研发了高强度空心玻璃微珠,可配制密度为0.93~1.07 g/cm^(3)的超低密度水基钻井液。详述了中古262-H4C井井漏失返后利用低密度水基钻井液重建井筒循环、恢复常规定向钻进的施工过程。现场钻井液密度最低降至0.98 g/cm^(3),井漏失返后多钻373 m,实现了一井钻穿两个缝洞体的地质目的,保障了该井井漏失返后钻至设计井深,开创了空心玻璃微珠超低密度钻井液在国内垂深超6000 m的超深井应用先例,为我国类似老区低压地层应用提供了技术参考。

水玻璃种类对聚合物改性碱激发矿渣性能的影响

从水化过程、力学性能、收缩性能等方面系统研究了2种水玻璃对苯丙乳液(SA乳液)改性碱激发矿渣(AAS)性能的影响及其作用机理,以期指导SA乳液在AAS中的应用.结果表明:钾水玻璃(PWG)加速矿渣水化进程的能力强于钠水玻璃(SWG);SA乳液不影响AAS的水化进程,不会阻碍水化硅酸钙/水化硅铝酸钙的生成,但会抑制水滑石的生成;SA乳液显著降低了AAS的抗压强度,并且对PWG激发AAS的影响强于SWG激发AAS;AAS的抗折强度随着SA乳液掺量的增加呈先增大后减小的趋势,在SWG与PWG激发AAS中,SA乳液的最佳掺量分别为2.5%与5.0%;PWG激发AAS在14d内的总变形量高于SWG激发AAS,SA乳液可显著降低硬化浆体的总收缩量.

矿用聚氨酯/水玻璃堵水复合材料的制备及研究

随着煤矿开采力度加大,突水、动水等灾害严重影响施工人员的安全,注浆堵水材料发挥着重要的作用。采用水玻璃对聚氨酯改性,制备合成聚氨酯/水玻璃(PU/WG)复合注浆材料。探究催化剂[二月桂酸二丁基锡(DBTDL)、二甲基苄胺(BDMA)、二甲胺基乙氧基乙醇(DMAEE)]对复合材料固化时间和最高反应温度的影响,得到其最佳配方为DBTDL∶BDMA=1∶1(总含量为0.2%)。同时,通过力学性能、最高反应温度等参数探究不同水玻璃模数对PU/WG复合材料的影响,得到水玻璃模数为2.31的效果最好,并对其进行抗老化性能、水质影响、渗透系数等测试,结果表明其均符合最新行业安全标准AQ/T 1087—2020《煤矿堵水用高分子材料》,PU/WG复合材料在煤矿堵水方面有潜在应用前景。

水玻璃固化冰碛物的强度及固结机理分析

为解决普朗铜矿在开采过程中地表松散冰碛物堆积造成地面塌陷和泥石流的问题,本文采用水玻璃复合酯类固化剂制备固结材料固结冰碛物,对冰碛物固结体的抗压强度进行了研究,并通过XRD、FTIR、DSC-TG和SEM对水玻璃复合酯类固化剂固结材料固结冰碛物的固结机理进行了探究。结果表明,冰碛物固结体28 d抗压强度最高可达2.05 MPa,具有较好的固结性能。酯类固化剂作用下,水玻璃水解产物与酯类固化剂的水解产物反应生成乙酸钠和硅凝胶,硅凝胶起到了填充冰碛物颗粒之间的空隙、胶结冰碛物颗粒的作用。

改性水玻璃加固细砂层暗挖隧道现场注浆试验

全断面细砂地层暗挖隧道施工存在塌方失稳的工程风险。本研究通过开展室内试验、现场原位浆液渗透注浆加固试验和现场原位注浆开挖试验,对改性水玻璃浆液在细砂层内部的扩散特征、固砂性能及隧道开挖稳定性开展了一系列工作。结果表明:当改性水玻璃浆液凝结时间控制在1~4 h时,可有效改善低应力条件下粉细砂的抗剪强度,无侧限抗压强度可达到140~170 kPa;在0.3~0.5 MPa注浆压力作用下,改性水玻璃浆液在小导管周边形成了60~80 cm厚的固砂体,有效抑制了砂层塌落,为暗挖隧道的稳定开挖提供保障,现场实测地表变形量控制在25 mm以内;细砂层暗挖隧道超前小导管布孔间距控制在30~50 cm以内,改性水玻璃浆液合理配比宜通过室内试验初选、现场浆液渗透注浆加固试验验证和现场开挖效果反馈等多种手段进行综合确定。