热活化高岭土制备地质聚合物研究

将高岭土与氢氧化钠按不同的质量比混合,在980℃下煅烧35 min进行固体活化,生成硅、铝前聚物.选取碱/土配比最佳的活化产物,经加水、成型和养护,制成有一定抗压强度的地质聚合物.采用FTIR、XRD和SEM方法对原料、活化产物和地质聚合物的表面键合、物相及微观结构进行分析.结果表明,高岭土的特征—Si—O—Si(Al)链在加碱热活化过程中断裂,形成无序的硅、铝前聚物,这些高能的硅、铝前聚物经水化生成具有连续有序三维—Si—O—Si(Al)网状结构的地质聚合物.这种加碱固体热活化方法可有效利用天然硅铝酸盐合成地质聚合物.     

两种土壤聚合物碱激发剂的激发效果对比

采用大液固比的方法对比研究了氢氧化钠和硅酸钠溶液对偏高岭石的激发作用,将反应到一定时间的浆体进行分离,对分离后的溶液和粉体分别进行分析.研究结果表明:(1)随反应时间的延长,偏高岭土与硅酸钠溶液反应分离后溶液中Si的聚合度增加,溶解的Al单体与溶液中的硅酸根离子聚合,分离后的粉体既有被碱侵蚀后的硅氧的碎片,也有铝单体与硅酸根离子聚合的胶团;(2)随反应时间的延长,偏高岭土与氢氧化钠溶液反应分离后溶液中的Si和Al含量不断增多,但硅和铝没有发生聚合,分离后粉体仅是偏高岭石在碱侵蚀下生成的碎片;(3)硅酸钠溶液中的硅酸根离子对土聚反应起到了重要的作用.     

NaOH溶液浓度及反应时间对偏高岭土地质聚合反应的影响

采用等温量热法(ICC)、X线衍射仪(XRD)及傅里叶变换红外光谱仪(FT-IR),分析偏高岭土经不同浓度NaOH溶液激发后反应不同时间生成的产物。结果表明:40℃下偏高岭土与10和12 mol/L NaOH溶液反应,分别生成Na-A型沸石和硅铝酸钠材料(地质聚合物)。地质聚合反应初期涉及溶解、聚合及重排的过程,决定了产物的有序程度及性能。为保证地质聚合物的制备,应控制反应条件及激发剂浓度,避免产物向沸石转变。     

粉煤灰基矿质聚合物的制备研究

以粉煤灰、偏高岭土为主要铝硅原料,辅以矿山尾矿固体废弃物合成一系列的矿质聚合物.通过测定其抗压强度优选出偏高岭土、粉煤灰、矿渣的最佳配比为3:3 : 5,碱激发剂浓度在15%时,矿质聚合物的强度最高,达到36.36 MPa.XRD、SEM分析表明其结构主要是无定形态,并且形成了连续的胶凝相.     

固化重金属离子用地质聚合物基体的制备及其离子相容性

以改性钠水玻璃激发粉煤灰、偏高岭土和硅灰等复合硅、铝固体原料,采用混合正交实验设计方法,确定了固化重金属离子用地质聚合物基体的配方并初步研究了基体与Cu2+、Pb2+的相容性.结果表明:在常温(20℃)养护条件下、n(SiO2)/n(Al2O3)=4.0、水玻璃模数M=1.2时,可以获得制备性能和力学性能良好的地质聚合物基体,相应的固体原材料组成为:粉煤灰和偏高岭土的质量比为13∶7、硅灰掺量为粉煤灰和偏高岭土总量的18.5%;地质聚合物基体与Cu2+和Pb2+均具有较好的相容性;适当掺量的Cu2+和Pb2+在一定程度上能增加地质聚合物的抗压强度,在掺量达到2%时,固化体均具有较好的强度,能达到资源化利用的目的.     

沸石基地聚合物固化核素Sr~(2+)的性能及机制

"沸石原位转化地聚合物固化核素"可实现中低放射性核废液"吸附浓缩-固化"处置的一体化。该文在研究水玻璃模数、碱灰比和偏高岭土掺量对沸石基地聚合物抗压强度影响的基础上,探讨了沸石基地聚合物固化模拟核素锶Sr2+的性能及机制。研究结果表明,水玻璃模数在0.8~1.5时有利于制备出高强度的地聚合物;偏高岭土中硅铝成分活性大于4A沸石,但添加过量偏高岭土使反应体系硅铝比减小,反而导致其强度降低;地聚合物固化体性能优良,28d抗压强度为19 MPa;固化体在酸性和中性介质中42 d的浸出率和累积浸出分数均低于国家标准。X射线衍射(XRD)分析表明,Sr2+取代部分原料中的Na+进入地聚合物中,发生了吸附固化和胶凝相的物理包裹。红外(IR)分析表明,模拟核素锶可能通过化学键的形式进入地聚合物的三维网络结构实现固化。X射线光电子能谱(XPS)分析进一步表明,锶与含硅官能团发生了反应,促进了硅酸的聚合作用。     

以Al13和氯化铝为铝源合成莫来石

以[AlO4Al12(OH)24(H2O)12]7+(简称Al13)和氯化铝为铝源,以硅酸钠和活化硅酸为硅源,采用4种组合方法,研究莫来石的合成.通过27Al NMR、X射线衍射和红外吸收光谱等研究反应过程及材料微结构演变.结果表明:以Al13为铝源制备α-Al2O3具有低温优势;以活化硅酸和Al13为硅源和铝源制备的莫来石前驱体,经900℃煅烧生成莫来石,经1200℃煅烧生成单相莫来石,其机理在于在前驱体中已经形成类莫来石的 SiOAl 键合.     

脱硫石膏-偏高岭土-水泥复合胶凝体系研究

对50%脱硫石膏和偏高岭土组成的辅助胶凝材料与50%水泥组成的复合胶凝体系进行了试验研究.结果表明:800℃热激活脱硫石膏为无水石膏,透射电子显微镜(TEM)分析表明存在明显空腔结构和晶体缺陷;脱硫石膏经400~800℃热激活处理后试样10min~7d的溶解速率不同,且经800℃热激活处理的脱硫石膏溶解速度最快;标养条件下选用经800℃热激活的脱硫石膏作为复合胶凝体系的组分能够获得较高抗压强度,而蒸养条件下可选用未经热激活的脱硫石膏;脱硫石膏与偏高岭土配比按CaSO4和Al2O3摩尔比控制,其比值在0.7~1.1范围内较为适宜,能够达到理想的强度且体积稳定性良好.     

硅酸钠模数对无机聚合物力学性能与微观结构的影响

用模数m=1.0、1.2、1.4和1.6的4种硅酸钠溶液作激发剂制备偏高岭土基无机聚合物,通过强度测试、红外分析(IR)、X线衍射(XRD)和扫描电镜(SEM)等方法考察激发剂模数对无机聚合物力学性能和微观结构的影响。结果表明:模数在1.0~1.6变化时,激发剂中硅氧四面体呈低聚合态;随养护时间延长,无机聚合物抗压强度和抗折强度提高,m=1.2的无机聚合物28 d抗压强度最高(74.6 MPa),抗折强度为11.2 MPa;4种无机聚合物主体相均呈非晶态,结构上由凝胶体和残留原料颗粒组成,其中,m=1.2时无机聚合物的显微结构最平整。     

热活化污泥—高钙粉煤灰复合地聚合物的性能与机理研究

研究采用水玻璃激发的高钙粉煤灰和热活化污泥制备复合地聚合物的可行性,并讨论制备的复合地聚合物的性能与机理.结果表明:经900℃焙烧1h的污泥(<45μm)以10%质量分数的掺量取代高钙粉煤灰后研制成的地聚合物具有较好的抗压强度;在复合地聚合物体系中,无定形地聚合物凝胶包裹在球状粉煤灰颗粒周围,有类沸石矿物生成,出现Al—O/Si—O对称伸缩峰及Si—O—Si/Si—O—Al弯曲振动峰.这一研究可以丰富地聚合物原材料的选择,有助于含硅铝相和含钙工业废弃物的资源化利用.     

地聚物基复合材料的制备及弯曲强度的研究

地聚物材料属于脆性材料,为了提高其韧性,以偏高岭土、水玻璃、聚氧化乙烯(PEO)为原料,首先将PEO高分子材料适量插入偏高岭土层片中,再通过碱聚合反应,形成地聚物基复合材料,结果表明,复合材料的弯曲强度有所增加;另外,分散剂、消泡剂的添加有利于复合材料弯曲强度的提高.     

Replacement of alkali silicate solution with silica fume in metakaolin-based geopolymers

A metakaolin(Mk)-based geopolymer cement from Tunisian Mk mixed with different amounts of silica fume(SiO_2/Al_2O_3 molar ratio varying between 3.61 and 4.09) and sodium hydroxide(10M) and without any alkali silicate solution, is developed in this work. After the samples were cured at room temperature under air for 28 d, they were analyzed by X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, environmental scanning electron microscopy, mercury intrusion porosimetry, ~(27)Al and ~(29)Si nuclear magnetic resonance(NMR) spectroscopy, and compression testing to establish the relationship between microstructure and compressive strength. The XRD, FTIR, and ~(27)Al and ~(29)Si NMR analyses showed that the use of silica fume instead of alkali silicate solutions was feasible for manufacturing geopolymer cement. The Mk-based geopolymer with a silica fume content of 6 wt%(compared with those with 2% and 10%), corresponding to an SiO_2/Al_2O_3 molar ratio of 3.84, resulted in the highest compressive strength, which was explained on the basis of its high compactness with the smallest porosity. Silica fume improved the compressive strength by filling interstitial voids of the microstructure because of its fine particle size. In addition, an increase in the SiO_2/Al_2O_3 molar ratio, which is controlled by the addition of silica fume, to 4.09 led to a geopolymer with low compressive strength, accompanied by microstructures with high porosity. This high porosity, which is responsible for weaknesses in the specimen, is related to the amount of unreacted silica fume.     

Preparation of fly ash and rice husk ash geopolymer

The geopolymer of fly ash (FA) and rice husk ash (RHA) was prepared. The burning temperature of rice husk, the RHA fineness and the ratio of FA to RHA were studied. The density and strength of the geopolymer mortars with RHA/FA mass ratios of 0/100, 20/80, 40/60, and 60/40 were tested. The geopolymers were activated with sodium hydroxide (NaOH), sodium silicate, and heat. It is revealed that the optimum burning temperature of RHA for making FA-RHA geopolymer is 690oC. The as-received FA and the ground RHA with 1%-5% retained on No.325 sieve are suitable source materials for making geopolymer, and the obtained compressive strengths are between 12.5-56.0 MPa and are dependent on the ratio of FA/RHA, the RHA fineness, and the ratio of sodium silicate to NaOH. Relatively high strength FA-RHA geopolymer mortars are obtained using a sodium silicate/NaOH mass ratio of 4.0, delay time before subjecting the samples to heat for 1 h, and heat curing at 60oC for 48 h.     

Properties of high calcium fly ash geopolymer pastes with Portland cement as an additive

The effect of Portland cement (OPC) addition on the properties of high calcium fly ash geopolymer pastes was investigated in the paper. OPC partially replaced fly ash (FA) at the dosages of 0, 5%, 10%, and 15% by mass of binder. Sodium silicate (Na₂SiO₃) and sodium hydroxide (NaOH) solutions were used as the liquid portion in the mixture: NaOH 10 mol/L, Na₂SiO₃/NaOH with a mass ratio of 2.0, and alkaline liquid/binder (L/B) with a mass ratio of 0.6. The curing at 60℃ for 24 h was used to accelerate the geopolymerization. The setting time of all fresh pastes, porosity, and compressive strength of the pastes at the stages of 1, 7, 28, and 90 d were tested. The elastic modulus and strain capacity of the pastes at the stage of 7 d were determined. It is revealed that the use of OPC as an additive to replace part of FA results in the decreases in the setting time, porosity, and strain capacity of the paste specimens, while the compressive strength and elastic modulus seem to increase.     

Electrical conductivity and dielectric property of fly ash geopolymer pastes

The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were studied. The effects of the liquid alkali solution to ash ratios (L/A) were analyzed. The mineralogical compositions and microstructures of fly ash geopolymer materials were also investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The 10 mol sodium hydroxide solution and sodium silicate solution at a sodium silicate-to-sodium hydroxide ratio of 1.0 were used in making geopolymer pastes. The pastes were cured at 40℃. It is found that the electrical conductivity and dielectric constant are dependent on the frequency range and L/A ratios. The conductivity increases but the dielectric constant decreases with increasing frequency.     

非金属矿物聚合材料的制备及性能研究

以偏高岭土、粉煤灰为主要原料,沸石、黏土为辅料,生石灰和钠水玻璃为碱激发剂制备矿物聚合材料.通过正交试验研究了养护温度、养护时间、蒸养时间对抗压强度影响,通过单因素实验研究了生石灰用量、水固比及水玻璃模数对抗压强度影响;并通过红外光谱、X-射线衍射和扫描电镜分析了样品的化学键变化、物相组成及微观形貌.结果表明,最佳的养护条件为养护温度80℃、湿度95%,养护时间72 h,0.8 MPa蒸养8h;生石灰用量、水固比、水玻璃模数的最佳值分别为3%(wt)、0.37、2.3,样品的最大抗压强度为60.8 MPa.     

Thermal treatment and utilization of Al-rich waste in high calcium fly ash geopolymeric materials

The Al-rich waste with aluminium and hydrocarbon as the major contaminant is generated at the wastewater treatment unit of a polymer processing plant. In this research, the heat treatment of this Al-rich waste and its use to adjust the silica/alumina ratio of the high calcium fly ash geopolymer were studied. To recycle the raw Al-rich waste, the waste was dried at 110℃ and calcined at 400 to 1000℃. Mineralogical analyses were conducted using X-ray diffraction (XRD) to study the phase change. The increase in calcination temperature to 600, 800, and 1000℃ resulted in the phase transformation. The more active alumina phase of active θ-Al₂O₃ was obtained with the increase in calcination temperature. The calcined Al-rich waste was then used as an additive to the fly ash geopolymer by mixing with high calcium fly ash, water glass, 10 M sodium hydroxide (NaOH), and sand. Test results indicated that the calcined Al-rich waste could be used as an aluminium source to adjust the silica/alumina ratio and the strength of geopolymeric materials. The fly ash geopolymer mortar with 2.5wt% of the Al-rich waste calcined at 1000℃ possessed the 7-d compressive strength of 34.2 MPa.     

粉煤灰基地聚合物砂浆组成设计与性能研究

以粉煤灰为主要原材料,矿粉为添加剂,水玻璃和氢氧化钠为复合激发剂,标准砂为细集料,制备地聚合物砂浆。运用三维图与等值线作图分析的方法,探究水胶比与胶砂比这两个组成设计参数对粉煤灰基地聚合物砂浆的流动度、抗压强度、抗折强度的影响规律。试验结果表明水胶比与胶砂比均对粉煤灰基地聚合物砂浆流动度与力学强度影响较大。水胶比在0.4~0.42,胶砂比在0.45~0.5时,制备出的地聚合物砂浆工作性能和力学性能较优。基于地聚合物砂浆脆性较大的特点,应用长度为8 mm与12 mm的PVA纤维进行增韧改性。结果表明,掺量为0.5%的PVA纤维对地聚合物砂浆抗压强度影响不大,但是抗折强度显著提高,延性增强,因此压折比下降,弯曲韧性增强。