粉煤灰基矿物聚合材料的抗压强度和微观结构

以粉煤灰为硅铝原料,钠水玻璃为激发剂,在80℃下干燥养护6 h制备了矿物聚合材料。研究了钠水玻璃固相组成对试件抗压强度的影响,并通过X射线衍射、扫描电镜、27Al和29Si魔角自旋核磁共振方法分析了最优试件的物相组成、微观形貌和微观结构。结果表明,模数为1.5、Na2O掺量为10%(质量分数)的钠水玻璃激发粉煤灰制得的试件抗压强度约为18 MPa;SEM分析表明凝胶由纳米级颗粒组成,颗粒之间相互连接形成致密的空间网络;XRD和MAS-NMR分析表明矿物聚合材料具有一定的无定形状态,漫射峰对应的衍射角在25°～35°范围内,Al主要以四配位的AlQ4(4Si)结构单元存在,Si主要以Q4(2Al)和Q4(3Al)结构单元存在。     

Effect of SiO2/Na2O mole ratio on the properties of foam geopolymers fabricated from circulating fluidized bed fly ash

Geopolymers are three-dimensional aluminosilicates formed in a short time at low temperature by geopolymerization. In this pa-per, alkali-activated foam geopolymers were fabricated from circulating fluidized bed fly ash （CFA）, and the effect of SiO2/Na2O mole ratio （0.91-1.68） on their properties was studied. Geopolymerization products were characterized by mechanical testing, scanning electron mi-croscopy （SEM）, energy-dispersive X-ray spectroscopy （EDX）, and X-ray diffraction （XRD）. The results show that SiO2/Na2O mole ratio plays an important role in the mechanical and morphological characteristics of geopolymers. Foam samples prepared in 28 d with a SiO2/Na2O mole ratio of 1.42 exhibit the greatest compressive strength of 2.52 MPa. Morphological analysis reveals that these foam geo-polymers appear the relatively optimized pore structure and distribution, which are beneficial to the structure stability. Moreover, a combina-tion of the Si/Al atomic ratio ranging between 1.47 and 1.94 with the Na/Al atomic ratio of about 1 produces the samples with high strength.     

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.     

超疏水泡沫吸油材料的制备及性能研究

采用十二烷基三甲氧基硅烷(DTMS)对氧化锌颗粒表面进行处理,得到改性氧化锌颗粒,将改性氧化锌颗粒涂覆在聚氨酯泡沫表面,制备得到泡沫吸油材料.采用傅立叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)和扫描电镜(SEM)对泡沫吸油材料的表面进行表征,利用接触角测试仪(CA)对其表面性能进行分析,并对其吸油性能和重复利用率进行了研究.结果表明:(1)该泡沫的表面水接触角为153°,具有超疏水特性;(2)该泡沫可以吸收多种油,最高吸油倍率为9.55g/g,吸水倍率为0.58g/g,重复利用率高.此种泡沫是一种综合性能优良的吸油材料.     

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.     

低掺量粉煤灰基地聚物胶凝材料性能试验研究

为了研究粉煤灰基地聚物胶凝材料的组成对其性能的影响,对C类粉煤灰分别掺入少量（质量分数小于17%）偏高岭土和矿渣粉后,进行了两种地聚物胶砂试块的力学性能试验研究,并与相同配比、相同制作养护条件下的普通硅酸盐水泥胶砂试块进行了比较.试验结果表明：纯粉煤灰（C类）地聚物胶凝材料强度低于P.O 42.5水泥;当外掺料质量分数大于17%时,粉煤灰基地聚物胶凝材料强度超过同龄期（14 d）的水泥;掺入矿渣粉的粉煤灰基地聚物抗压强度高于掺入等量偏高岭土的粉煤灰基地聚物.     

锂离子电池硅/石墨/蔗糖碳复合负极材料的制备和电化学性能

以纳米硅(Si)、天然石墨(NG)和蔗糖为前驱体通过球磨和裂解制备了具有壳核结构的碳硅复合材料(Si/NG/DC).用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)表征了复合材料的组成和形貌结构.恒电流充放电测试表明,Si/NG/DC复合材料表现出较好的电化学性能,它的最高可逆容量达730mA.h.g-1,在测试的45个循环中,从第二个循环开始,容量没有出现明显衰退.交流阻抗(EIS)测试表明,Si/NG/DC导电性的提高和电极结构在循环过程中的稳定性是其电化学性能改善的原因.     

纳米氧化铝增强铝硅磷质矿物键合材料的合成和性能

室温下,在偏高岭土与Al（H2PO4）2溶液混合均匀,并加入纳米氧化铝,采用浇注（Ф20mm×20mm×20mm）成型方法合成纳米氧化铝增强偏高岭土基矿物键合材料。采用XRD、SEM、ID等测试方法研究了纳米氧化铝对偏高岭土基矿物键合材料性能的影响。研究结果显示：纳米氧化铝可明显增强其抗压强度;随着纳米氧化铝添加量的增加,养护时间的延长对抗压强度的影响越明显;XRD和IR测试结果显示其含有非晶相和次结晶相;SEM测试结果显示其保留了偏高岭土的层状结构。     

Anomalies in mid-high-temperature linear thermal expansion coefficient of the closed-cell aluminum foam

Low-density closed-cell aluminum foam is promising to be used as load-bearing and thermal insulation components. It is necessary to systematically study its thermal expansion performance. In this work, linear thermal expansion coefficient(LTEC) of the closed-cell aluminum foam of different density was measured in the temperature range of 100–500 °C. X-ray fluorescence was used to analyze elemental composition of the cell wall material. Phase transition characteristics were analyzed with X-ray diffraction and differential scanning calorimetry. LTEC of the closed-cell aluminum foam was found to be dominated by its cell wall property and independent of its density. Particularly, two anomalies were found and experimentally analyzed. Due to the release of the residual tensile stress, the LTEC declined and even exhibited negative values. After several thermal cycles, the residual stress vanished. With temperature higher than 300 °C,instantaneous LTEC showed hysteresis, which should result from the redistribution of some residual hydrogen in the Ti2Al20 Ca lattice.     

碳点修饰硅在锂离子电池中的应用研究

Silicon (Si) particles were functionalized using carbon dots (CDs) to enhance the interaction between the Si particles and the binders. First, CDs rich in polar groups were synthesized using a simple hydrothermal method. Then, CDs were loaded on the Si surface by impregnation to obtain the functionalized Si particles (Si/CDs). The phases and microstructures of the Si/CDs were observed using Fourier-transform infrared reflection, X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. Si/CDs were used as the active material of the anode for electrochemical performance experiments. The electrochemical performance of the Si/CD electrode was assessed using cyclic voltammetry, electrochemical impedance spectroscopy, and constant current charge and discharge experiment. The electrodes prepared with Si/CDs showed good mechanical structure stability and electrochemical performance. After 150 cycles at 0.2 C, the capacity retention rate of the Si/CD electrode was 64.0%, which is twice as much as that of pure Si electrode under the same test conditions.     

成型压力对废弃物基地质聚合物制品性能的影响

采用压制成型法,利用工业固体废渣为原料,制备了一类能耗低、免烧的地质聚合物.研究了压制成型时成型压力对制品强度、体积密度、吸水率、软化系数、耐磨性、耐水性以及抗冻融循环的影响,并结合SEM及XRD分析试样的微观形貌和矿物组成.试验结果表明:成型压力对地质聚合物制品的性能有重要影响,制备该废弃物基地质聚合物制品的最佳成型压力为30 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.     

CoMoO4水热法制备及其在锂/钠离子电池中的应用

碳基负极材料比容量低,无法满足高能量密度电池的需求.为了进一步寻找高容量长循环寿命的电池负极材料,采用水热反应法制备了自支撑CoMoO₄负极,通过X射线衍射（XRD）和扫描电子显微镜（SEM）对材料的结构、形貌进行表征,利用循环伏安法和恒电流充/放电等技术对比研究了材料在锂/钠离子电池中的电化学性能.结果表明,CoMoO₄负极在锂离子电池中的首次可逆比容量为1 403.6 mAh/g,首次库伦效率为146.5%,在100 mA/g电流密度下经50次循环后仍然高达793.6 mAh/g;而CoMoO₄负极在钠离子电池中首次可逆比容量仅为314.2 mAh/g,但经50次循环后容量保持率仍有76.4 %.该自支撑负极无需导电剂和粘结剂,电极材料与泡沫镍结合力强,具有优异的循环稳定性.     

Microstructure and properties of mullite-based porous ceramics produced from coal fly ash with added Al_2O_3

Using coal fly ash slurry samples supplemented with different amounts of Al_2O_3,we fabricated mullite-based porous ceramics via a dipping-polymer-replica approach,which is a popular method suitable for industrial application.The microstructure,phase composition,and compressive strength of the sintered samples were investigated.Mullite was identified in all of the prepared materials by X-ray diffraction analysis.The microstructure and compressive strength were strongly influenced by the content of Al_2O_3.As the Al/Si mole ratio in the starting materials was increased from 0.84 to 2.40,the amount of amorphous phases in the sintered microstructure decreased and the compressive strength of the sintered samples increased.A further increase in the Al_2O_3 content resulted in a decrease in the compressive strength of the sintered samples.The mullite-based porous ceramic with an Al/Si molar ratio of 2.40 exhibited the highest compressive strength and the greatest shrinkage among the investigated samples prepared using coal fly ash as the main starting material.     

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.     

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.     

碱激发不同活性粉煤灰地质聚合物的研究

对不同粉磨时间的粉煤灰进行活性Al与活性Si的测定,其溶出量随机械粉磨时间的延长而增加.平均颗粒直径为10.36μm的粉煤灰在激发剂作用下合成28d抗压强度为82.16MPa的地质聚合物.采用XRD和SEM分析手段对地质聚合物的结构和形貌进行了表征,XRD和SEM结果表明,地质聚合物的抗压强度与无定形的硅铝酸盐凝胶相的存在及粉煤灰的颗粒级配密切相关.     

炭泡沫中Si含量对碳化硅多孔陶瓷 组织和性能的影响

研究炭泡沫预制体中Si添加量的变化对碳化硅多孔陶瓷的组织及性能的影响. 以中间相沥青添加一定质量分数的Si粉为原料,经发泡工艺制备含Si的炭泡沫预制体并结合反应烧结工艺制得碳化硅多孔陶瓷. 对碳化硅多孔陶瓷的微观形貌、相组成、孔隙率、孔筋密度和抗弯强度进行分析与测试. 结果表明:随着炭泡沫预制体中Si量的增加,碳化硅多孔陶瓷的孔隙率下降,孔筋密度增加,抗弯强度提高. 当Si的质量分数为50%时,多孔陶瓷孔筋完全由SiC相组成,孔筋密度为3.14g/cm3,多孔陶瓷的抗弯强度达到23.9MPa,对应孔隙率为55%.     

炭黑填充LDPE体系发泡复合材料的导电性能

以低密度聚乙烯（LDPE）和乙烯-乙酸乙烯酯（EVA）为主基体, 乙炔炭黑(ACET)为导电填料, 偶氮二甲酰胺（AC）为发泡剂, 过氧化二异丙苯（DCP）为交联剂制备LDPE/EVA/CB导电泡沫复合材料. 通过分析炭黑含量、 交联剂、 发泡剂对复合材料电性能的影响表明, 该导电泡沫具有较理想的泡孔结构, 升温电阻测试表明, LDPE/EVA/ACET导电发泡复合材料具有较好的开关特性, 呈明显的正温度系数(PTC)特性, 并确定了发泡剂和交联剂的用量, 获得了具有较好泡沫性能和PTC特性的导电泡沫材料. 