球形硅微粉的微观结构研究

文章采用XRD、SEM研究了球型硅微粉的晶体结构和微观结构。XRD测试晶体结构,发现高温熔融喷射法制备的球型硅微粉里面有晶态石英存在;SEM分析微观结构发现高温熔融喷射法制备的部分球型硅微粉颗粒内部有孔洞存在。通过对晶体结构和微观结构进行分析,找到了高温熔融喷射法生产的球型硅微粉内结晶态存在的原因。     

硅微粉在粉末涂料中的应用研究

本文通过添加硅微粉来部分替代钛白粉,制得的复合粉体以应用于粉末涂料中,从而提高了漆膜的硬度,耐热等性能.主要考察了喷涂电压、固化温度和固化时间施工工艺,测试了不同配比的复合粉体(硅微粉:钛白粉为0:1、1:1、2:1、3:1、1:0)粉末涂料漆膜的白度、光泽度、硬度、耐冲击力以及耐热性等性能.结果表明,研究中粉末涂料最佳施工工艺条件为:喷涂电压70 kV、固化温度180℃、固化时间20 min.硅微粉的添加提高了漆膜的硬度,铅笔硬度由3H达到5H;漆膜的抗冲击力高于50 kg·cm;同时也提高了漆膜的耐热性,涂膜的TP由433.19℃上升到440.76℃;漆膜的光泽度有所降低,由78％降到66％;白度由88.5％降到39％.当硅微粉与钛白粉的配比为1:1时,漆膜综合性能最好,铅笔硬度为4H、耐冲击力高于50 kg· cm、光泽度达到75％、白度达到82％.复合微粉的粉末涂料,基本性能保持不变,降低了涂料的生产成本,为制备高硬度和耐冲击涂料提供了依据.     

硅微粉增韧增强聚丙烯材料研究

文章制备了硅微粉填充的聚丙烯材料.考察了不同硅微粉含量对材料的常低温冲击强度,拉伸强度,耐热性能的影响.结果表明硅微粉含量为20%是能使材料的性能达到最好.其常温的缺口冲击强度为空白样品的1.56倍;低温的缺口冲击强度为空白样品的1.70倍.同时材料的刚性和耐热温度也得到了提高.     

超声波酸浸除铁提纯硅微粉实验研究

研究了超声波外场下酸浸去除硅徽粉中铁杂质的效果,实验考察了超声波频率、时间对硅徽粉中铁杂质质量分数的影响.结果表明:超声波的机械作用能促成酸液的乳化和徽粉的分散,空化作用产生的局部高温高压,不仅可撕裂硅微粉中含铁杂质带,使酸液进入而溶出铁杂质,并且反应徽区的高能高温加速了反应进程,强化了酸浸除铁的效果.此外,提高超声波频率和增加处理时间均能提高铁杂质的去除率.经超声波处理后,样品铁杂质质量分数最低可以降到8 μg/g,相当于不加超声波外场情况的1/3.该结果为超声波用于硅徽粉提纯提供了相关研究基础.     

硅微粉/聚丙烯复合材料的性能研究

采用熔融共混方法制备了聚丙烯(PP)/硅微粉(Micro-Si O2)复合材料,采用SEM、热机械分析仪、高绝缘电阻仪测试了PP复合材料的性能。结果表明,硅微粉用量低于10%(质量分数)时,缺口冲击强度和拉伸强度分别提高了7.91%与3.87%。用量超过40%时,材料的电绝缘性能和热膨胀性能获得较高改善,表面电阻率增加到3.62×1010Ω,线膨胀系数由最初的1.51×10-4减小到1.29×10-4。通过SEM观察分析,低含量下硅微粉可起到一定的颗粒强化作用,分散应力的同时增加了材料的韧性。     

改性硅微粉在天然橡胶中的性能研究

硅微粉用双-[γ-(三乙氧基硅)丙基]四硫化物(Si69)和钛酸酯进行表面改性,将其添加到天然橡胶中,探讨了改性硅微粉对复合材料性能的影响。结果表明,Si69和钛酸酯改变了硅微粉的表面结构,分散性有很大程度的提高;Si69改性的硅微粉用量为20份时,天然橡胶的综合性能最佳。     

硅微粉的湿氧化损耗和表面钝化保护研究

硅微粉在水溶液中的损耗主要包括湿氧化及硅溶解过程,对其表面钝化处理可减少水对硅微粉的腐蚀。采用1%H2O2溶液对硅微粉钝化处理后其表面形成致密、光滑的钝化层,钝化表层的悬挂键Si-O-Si和Si-H有利于阻止水对硅微粉的湿氧化损耗。经钝化处理的硅微粉在水溶液中浸泡48h后损耗率少于1%,与未经钝化处理的硅微粉在相同条件下损耗率超过20%相比,表面钝化处理对减少硅粉湿氧化损耗能发挥有效作用。     

改性硅微粉在天然橡胶中的性能研究

硅微粉用双-[γ-(三乙氧基硅)丙基]四硫化物(Si69)和钛酸酯进行表面改性,将其添加到天然橡胶中,探讨了改性硅微粉对复合材料性能的影响。结果表明,Si69和钛酸酯改变了硅微粉的表面结构,分散性有很大程度的提高;Si69改性的硅微粉用量为20份时,天然橡胶的综合性能最佳。     

高端环氧树脂灌封料所用硅微粉的研究

硅微粉是高端环氧树脂灌封料中的一种重要填料.文章对日本、河南有色金源实业有限公司、国内三个地方产的800目硅微粉在高端灌封料应用中,粉体固化块的颜色和透明度、粘度、24h沉降三个技术指标进行了对比研究.得出结论,河南有色金源实业有限公司生产的800目硅微粉可以替代日本产的硅微粉,远远优于国内其它三个地方产的硅微粉.     

包膜增韧硅微粉对环氧树脂增韧机理的研究

本文首次提出预先对硅微粉进行增韧处理来达到增韧环氧树脂的新思路,并根据断裂理论,采用循环脉冲载荷对增韧硅微粉／环氧树脂复合材料进行冲击性能试验。分析了微裂纹的形成与扩展,探讨增韧硅微粉对环氧树脂的增韧机理。     

硅灰性能及其再利用的研究进展

硅灰作为硅铁行业的副产品,在建筑材料领域得到了广泛应用.通过分析中国硅铁行业的现状和硅灰回收的现状,可以看出未来几年硅铁冶炼行业在中国西北地区的突出优势,尤其是青海地区;青海地区硅灰的回收以湿排为主,回收的湿排硅灰大量堆放,对环境造成污染,给企业增加了负担.从国内外硅灰性能的研究进展和硅灰的应用领域来看,对硅灰性能的研究和应用主要是针对干排硅灰,而性能相近的湿排硅灰没有得到应用.提出应加强对湿排硅灰性能的理论和试验研究.     

Silica fume-basic blast furnace slag systems activated by an alkali silica fume activator

This paper deals with the results of research on binder systems based on the use of silica fume. The data obtained show that the optimal proportion of blast furnace slag and alkali activator prepared from silica fume permits the obtaining of interesting materials from the point of view of their technical properties as well as from the possibility of utilizing industrial wastes. The composite developed is hydraulic. It is possible to state that these kinds of binding systems have shown promise of future use.     

Alkali silica reactivity of agglomerated silica fume

It is commonly accepted that replacement of a portion of cement in mortar or concrete with well-dispersed silica fume reduces expansion caused by alkali silica reaction. Recently there has been much discussion that large, agglomerated particles of silica fume may actually act as alkali silica reactive aggregates, thereby increasing expansion rather than reducing it. The data in the literature, from both field and laboratory studies, are inconsistent. This prompted an extensive laboratory investigation into the alkali silica reactivity of silica fume. Results from accelerated expansion testing and microscopic investigations are presented. It was seen that some agglomerated silica fumes participate in ASR while others do not. Factors determining the reactivity of silica fume agglomerates are suggested.     

SiO2微粉浆体的流变性研究

利用流变仪研究了改变SiO2微粉种类(其d50分别为0.202、3.457、5.789 um,ω(SiO2)分别为96.70%、93.64%、93.00%)、浆体中SiO2微粉的体积分数(分别为15%、20%、25%、30%)和分散剂(分别为一水柠檬酸和三聚磷酸钠)时SiO2微粉浆体流变性的差异,并定量计算了SiO2微粉浆体相应的流变参数.试验结果发现:在0-300 s<'-1的剪切采集区域内,不同条件下测得的流变曲线均符合Bingham流体模型;加入分散剂三聚磷酸钠和一水柠檬酸能明显改善SiO2微粉浆体的流变性,且两者的分散效果有所差异.     

Preparation and characterization of a porous silicate material from silica fume

A porous silicate material derived from silica fume was successfully prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, Thermogravimetry and Differential thermal gravity (TG-DTG), N₂ adsorption and desorption isotherms, and scanning electron microscopy (SEM). Raw silica fume was analyzed by XRD, FT-IR and SEM. The analysis results of silica fume indicated that SiO₂ in silica fume is mainly determined as amorphous state, and that the particles of raw silica fume exhibited characteristic spherical structure with a diameter of from 50 nm to 200 nm. The preparation of the porous silicate material involved two steps. The first step was the extraction of the SiO ₃ ^2? leachate from raw silica fume. The maximum value of SiO ₃ ^2? extraction yield was obtained under the following conditions: reaction temperature of 120 °C, reaction time of 120 min, NaOH concentration of 15%, and alkali to SiO₂ molar ratio of 2. The second step was the preparation of the porous silicate material though the reaction of SiO ₃ ^2? leachate and Ca(OH)₂ suspension liquid. The optimum preparation conditions were as follows: preparation temperature of 90 °C, preparation time of 1.5 h, Si/Ca molar ratio of 1 : 1, and stirring rate of 100 r/min. The BET surface area and pore size of the porous silicate material were 220.7 m²·g^?1 and 8.55 cm³/g, respectively. The porous silicate material presented an amorphous and unordered structure. The spectroscopic results indicated that the porous silicate material was mainly composed of Si, Ca, O, C, and Na, in the form of Ca²⁺, SiO ₃ ^2? , CO ₃ ^2? and Na⁺ ions, respectively, which agreed with the XRD, TG-DSC, and FT-IR data. The N₂ adsorption-desorption isotherm mode indicates that the porous silicate material belonged to a typical mesoporous material. The porous silicate material presented efficiency for the removal of formaldehyde: it showed a formaldehyde adsorption capacity of 8.01 mg/g for 140 min at 25 °C.     

Electrical conductivity of concrete containing silica fume

The influence of silica fume on concrete properties represents an important technical research. In general, silica fume tends to improve both mechanical characteristics and durability of concrete. Thus the electrical properties of concrete containing silica fume can be studied to clarify its physical performance during hydration. The electrical conductivity of neat cement, mortar and concrete pastes was measured during setting and hardening. The ordinary Portland cement was partially replaced by different amounts of silica fume by weight. The changes in the electrical conductivity were reported during setting and hardening after gauging with water. The results of this study showed that the electrical conductivity can be used as an indication for the setting characteristics as well as the structural changes of the hardened pastes made with and without silica fume.     

Properties of rubberized concretes containing silica fume

A test program was carried out to develop information about the mechanical properties of rubberized concretes with and without silica fume. Two types of tire rubber, crumb rubber and tire chips, were used as fine and coarse aggregate, respectively, in the production of rubberized concrete mixtures which were obtained by partially replacing the aggregate with rubber. Six designated rubber contents varying from 2.5% to 50% by total aggregate volume were used. The concretes with silica fume were produced by partial substitution of cement with silica fume at varying amounts of 5–20%. Totally, 70 concrete mixtures were cast and tested for compressive and splitting tensile strengths, and static modulus of elasticity in accordance to ASTM standards. The design strength level ranging from 54 to 86 MPa was achieved using water–cementitious material (w/cm) ratios of 0.60 and 0.40. Test results indicated that there was a large reduction in the strength and modulus values with the increase in rubber content. However, the addition of silica fume into the matrix improved the mechanical properties of the rubberized concretes and diminished the rate of strength loss. Results also revealed that a rubber content of as high as 25% by total aggregate volume might be practically used to produce rubberized concretes with compressive strength of 16–32 MPa.     

Interaction of polycarboxylate ether with silica fume

The interaction of silica fume with negatively charged polycarboxylate ethers in comparison to a polyacrylate and two non-ionic polyethylene glycols is investigated by adsorption and streaming potential measurements at slight alkaline pH value. The results indicate that polyethylene glycol is adsorbed on the silica fume in a flat conformation. Increased molecular weight however favours network formation. In contrast, the polyacrylate is adsorbed only in a very low amount due to a mutual electrostatic repulsion of the negative charged silica surface and the carboxylate groups. Polycarboxylate ether, which combine both structural features, a negative charged backbone and non-ionic polyethylene glycol side chains, adsorb via hydrogen bonding mechanism of the side chains with the silica particles. The adsorption rate of the polycarboxylate ethers predominantly increases with decreasing carboxylic equivalent. However, the adsorption affinity is determined by both, the carboxylic equivalent and the side chain length of the polycarboxylate ether.     

Influence of silica fume on the tensile strength of concrete

The present paper is directed towards developing a better understanding on the isolated contribution of silica fume on the tensile strengths of high-performance concrete (HPC). Extensive experimentation was carried out over water-binder ratios ranging from 0.26 to 0.42 and silica fume-binder ratios from 0.0 to 0.3. For all the mixes, compressive, flexural and split tensile strengths were determined at 28 days. The compressive, as well as the tensile, strengths increased with silica fume incorporation, and the results indicate that the optimum replacement percentage is not a constant one but depends on the water-cementitious material (w/cm) ratio of the mix. Compared with split tensile strengths, flexural strengths have exhibited greater improvements. Based on the test results, relationships between the 28-day flexural and split tensile strengths with the compressive strength of silica fume concrete have been developed using statistical methods.     

High strength mortars containing condensed silica fume

A silica fume and a superplasticizer have been added to an ordinary easily flowing mortar composition. The optimal amounts of those constituents have been determined in order to obtain the maximum compressive strength for a constant workability. Large contents of silica fume and superplasticizer are needed (silica/cement=0.40 and superplasticizer/ce cement=2.4% in dry weights). The compressive strengths are approximately twice higher at 2,7 and 28 days as compared to the reference mortar. The drying shrinkage is slightly increased and the hydration kinetics is highly modified.