Optimal Conditions for Preparing Ultra-Fine CeO_2 Powders in A Submerged Circulative Impinging Stream Reactor

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor （SCISR） from Ce（NO3）3· 6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide （CeO2） powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce（NO3）3 and NH4HCO3 solutions were 02,5 and 0.3 mol · L^-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g · L^-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r · min^- 1,80 ℃, 20 min, 5 - 6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8 -2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point 5 group was OH^5-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor （STR）.

DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. 'the second plateau', appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.

Hydrogen Reduction:A Novel Method of Synthesizing Ultra-fine Chromic Oxide Powder

The ultra-fine chromic oxide powder was prepared by a novel gas-solid reduction reaction.Na2CrO4 was firstly reduced with hydrogen at 400-600 ℃.The obtained reduction products,mainly the mixture of NaCrO2 and sodium hydroxide（NaOH）,were converted into chromic oxide through hydrolysis followed by calcination.The obtained chromic oxide product was characterized by powder X-ray diffraction（XRD） and SEM.The results show that the hydrolysis process of sodium chromite is the key step and lower reduction temperature helps intensify the hydrolysis process.

Strengthening of HT250 by modified ultra-fine ceramic powders

In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, and the effects of the modified ultra-fine ceramic powders on microstructure, mechanical properties and wear resistance were studied. Metallographic examination, tensile test, scanning electron microscopy, and three-dimensional surface topography were applied to analyze and compare the samples containing modified powder with the original samples. The results showed that the most obvious modification effect among the powders was seen in the sample containing powder A, with the graphite and eutectic cells being refined, the tensile strength being increased by 36.9%, and the wear resistance being improved by 45.5% and 47.2% under loads of 150 N and 300 N, respectively. The improvements of mechanical properties and wear resistance in the HT250 cast iron with the modified ultra-fine ceramic powders were attributed to the synergistic effect of the grain refinement with the powder acting as a hard particle phase and the lubrication by the graphite.

Powder Quartz/Nano-TiO2 Composite: Mechanochemical Preparation and Photocatalytic Degradation of Formaldehyde

Powder quartz(PQ)/nano-TiO2composite was prepared by a mechanochemical method. Based on as-prepared PQ/nano-TiO2composite, we prepared interior paints and investigated the degradation efficiency of formaldehyde(DEF). Scanning electron microscopy showed that nano-TiO2got well dispersed by the adding of PQ. Thermogravimetric analysis indicated that the mass ratio of 4:1 was a relatively good proportion for the most production of PQ/nano-TiO2composite. Fourier transform-infrared spectrometry showed that the peak position of Ti-O-Si bond varied with the milling time. At the early stage, no characteristic peak of Ti-O-Si bond was observed, while at the later stage, new peaks at 902 cm-1and 937 cm-1appeared. Meanwhile, PQ/nano-TiO2composite-based interior paint exhibited significant DEF of 96.3% compared to that consisting of sole nanoTiO2of 92.0% under visible light illumination. As an abundant mineral resource, PQ would make interior paints with HCHO purifying effect much more efficient and cheaper.

Preparation of Well Dispersed and Ultra-Fine Ce(Zr)O_2 Mixed Oxide by Mechanochemical Processing

Ultra-fine CeO_2-ZrO_2 mixed oxide was successfully synthesized by wet-solid phase mechanochemical processing, Ce_2(CO_3)_3·8H_2O, ZrOCl_2·xH_2O and ammonia were used as reactants. It is found that the crystalline Ce_2(CO_3)_3·8H_2O and ZrOCl_2·xH_2O are changed to amorphous cerium and zirconium hydroxide precursor after milling with ammonia, and Ce_(0.15)Zr_(0.85)O_2 mixed oxide with pure tetragonal phase structure and medium particle size(D_(50))less than 1μm is formed by calcining precursor over 673 K. The XRD patterns indicate that the crystal unite size increases with rising calcining temperature due to crystal growth. However, the particle size and BET surface area of the Ce(Zr)O_2 mixed oxide decreases with rising calcining temperature, which may be attributed to the contract of particles and the vanish of holes inside grains.

Hydration Products of Cement-silica Fume-quartz Powder Mixture under Different Curing Regimes

Composition, morphology, and structure of hydration products in hardened pastes of three kinds of blended cement（cement-silica fume, cement-quartz powder and cement-silica fume-quartz powder） hydrated under different curing regimes（standard curing, 90 ℃ steam curing, 200 ℃ and 250 ℃ autoclave curing） were investigated by X-ray diffraction and field emission scanning electron microscope equipped with EDAX system. Results showed that the main hydration products in three kinds of hardened pastes under standard curing condition are all C-S-H gels, CH, and AFt. Under 90 ℃ steam curing condition, the main hydration products of cement-silica fume and cement-silica fume-quartz powder are C-S-H gels, whereas those of cement-quartz powder are C-S-H and CH. Under 200 or 250 ℃ autoclave curing condition, no obvious crystallized CH phase is found in hardened pastes of three kinds of blended cement, and C-S-H gels are transformed into one or more crystalline phases such as tobermorite, jennite, and xonotlite. The chemical composition and morphology of these crystalline phases depend on the composition of mixture and autoclave temperature.

Characteristic Analysis of a Powder Quartz Mine in Yunnan Province

The characteristic study of powder quartz is the basis of the comprehensive utilization of quartz powder resources.In this paper,the characteristic of a powder quartz mine in Yunnan Province is analyzed, through the analysis of X-ray diffraction,chemical composition,SEM analysis of the different samples those purified to different extent,etc.The results indicated that the powder quartz’s whiteness is 81.4, and the main mineral compositions are quartz,clay mineral(mostly kaolinite and illite) and a little of feldspar,and the content of quartz is about 85%。

CARBOTHERMAL PREPARATION OF Si_2N_2O FROM NATURAL QUARTZ POWDER

Si2N2O powder was synthesized by car-bothermal reduction and nitridation natural quartz powder. At the same time, the effects of the process parameters such as SiO2/C ratio, temperature and time on the compositions of products were analysed. It is found that the compositions of products depend closely on the parameters mentioned above, and that the product containing higher Si2N2O phase could be obtained by choosing suitable process parameters.

固废资源合成堇青石工艺及其性能研究

为了合理利用固废资源、缓解资源紧张,根据堇青石的化学组成,以质量分数分别为12%的电熔镁砂收尘粉、40%的电熔刚玉收尘粉、48%的石英尾砂为原料,分别在1320、1350、1380、1390、1400、1410℃保温3 h煅烧,制备堇青石质耐火原料,研究了煅烧温度对堇青石试样相组成、显微结构、物理性能等的影响。结果表明:在1390℃之前,镁铝尖晶石和方石英逐渐反应生成堇青石直至方石英相完全消除,当煅烧温度达到1390℃时,试样中的堇青石相含量达94%(w),次晶相为镁铝尖晶石,此时试样的热膨胀系数最低,为3.2×10^(-6)℃^(-1),体积密度较低,为1.85 g·cm^(-3),热导率较低,为1.279 W·(m·K)^(-1),显微结构较致密,综合性能最优。

石英陶瓷的制备技术及应用进展

石英陶瓷具有热膨胀系数小、热稳定好、介电常数低等优良特性,是诸多结构材料和功能材料领域的关键产品。基于石英陶瓷材料的性能优势及制备工艺,详细分析了高纯石英粉体的制备技术、石英陶瓷制备过程中的关键技术,归纳了提升石英陶瓷各项性能的关键因素及控制原理,分析了石英陶瓷在航空航天、浮法玻璃、电子、冶金、太阳能多晶硅等国家战略需求领域的应用现状,并对石英陶瓷未来的发展方向和解决方案进行了展望。

泡沫陶瓷材料的制备及性能研究

以石英砂尾泥为主要原料采用发泡剂法制备泡沫陶瓷材料。主要研究了原料配方即石英砂尾泥、废玻璃粉、发泡剂、稳泡剂的用量对泡沫陶瓷的体积密度、吸水率和孔隙率的影响。结果表明:体积密度随石英砂尾泥和SiC用量的增加而降低,随稳泡剂用量的增加而升高。吸水率随石英砂尾泥用量的增加而增大,随SiC和稳泡剂用量的增加而降低。石英砂尾泥和废玻璃粉的最佳配比为55%和45%。发泡剂、稳泡剂最佳用量分别为2%和1%。

SGTF粉末干式永磁磁选机的研制及应用

为解决干旱缺水地区石英砂开发利用难、湿式磁选投资大、生产成本高的问题,提出采用COMSOL MULTIPHYSIC多物理场仿真软件对磁系排列、磁场梯度等磁系特征进行模拟仿真的方法设计新的磁系,并通过选用耐高温型稀土材料磁钢解决了筒体发热和磁块性能之间的矛盾,研制出的SGTF粉末干式永磁磁选机的磁场强度可达597 kA/m,最大处理量为250 t/h。河南某选矿厂的工业应用中,石英砂经SGTF粉末干式永磁磁选机1次分选,铁含量可降低至0.06%,达到了作为生产玻璃原材料的使用标准。研究结果表明:新式粉末干式永磁磁选机的磁场强度及处理能力得到了提升,提高了在非金属除铁中的应用,缩减了生产工艺流程,降低了选矿成本,可为干旱缺水和北方寒冷地区石英砂矿的经济开发提供新的解决方案。

Preparation of Reactive Powder Concrete Using Fly Ash and Steel Slag Powder

To decrease the cement and SF content of RPC by using ultra-fine fly ash （UFFA） and steel slag powder （SS）, the effect of these mineral admixtures on compressive strength of RPC were investigated. The experimental results indicate that the utilization of UFFA and SS in RPC is feasible and has prominent mechanical performance. The microstructure analysis （SEM and TG-DTG-DSC） demonstrated that the excellent mechanical properties of RPC containing SS and UFFA were mainly attributed to the sequential hydration filling effect of the compound system.

Synthesis and Characterization of Nano-sized Boron Powder Prepared by Plasma Torch

Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4.5：1, total feed of 4.9 m3/h, and plasma power of 25 kW. The samples were analyzed by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, and inductively coupled plasma - mass spectrometry （ICP-MS）, inductively coupled plasma - atomic emission spectrometry （ICP-AES）, inductive combustion infrared absorption （ICIA） and infrared thermal conductivity of oxygen and nitrogen analyzer （ITCA）. The results show that the boron powders have different crystal structures with higher dispersion and purity. The average diameter is about 50 nm, and the purity is 90.29% or so. This new technology can use simple process to produce high quality boron powders, and is feasible for industrial production.

Preparation of Ultrafine Tungsten Powder by Sol-Gel Method

Sol-gel method was employed for the preparation of nanoscale tungsten powder. The effects of different preparation conditions on particle size were discussed and the optimum preparation condition was found. The products were characterized by X-ray diffraction, scan electron microscopy and so on. The results show that the intermediate is monoclinic WO3, its particle shape is approximately spherical, and the particle size distribution is narrow. The average particle size is about 60 nm. After deoxidization, WO3 turns into cubic tungsten powder with small particle size （average particle size about 120 nm） and narrow size distribution.

Crystal Structure of Ba_xSr_1-xTiO₃Fine Powder

Various compositions of the system BaxSr1-xTiO3 (BST) have been elaborated both as fine powders and ceramic monoliths, using the co-precipitation route within a warmed supersaturated solution of oxalic acid. The appropriate stoichiometry was determined from the mixtures of precisely titrated aqueous solutions of cations chlorides (SrCl2, BaCl2, and TiCl4). The reason of this process was to apply low sintering temperature in production of BST samples with ultra-fine powders. These powders primarily calcined at (850°C) for (5 hr) were used to elaborate ceramics after pellets sintering at (1200°C) during (8 hrs). Indeed, XRD patterns were confirmed that the samples are a pure phase and a perovskite cubic structural type at (x = 0, 0.5, 0.6). Whereas, (x = 0.7, 0.8, 0.9, 1) showed a tetragonal phase. There is agreement between the FTIR and XRD analysis, by the relation of the wave vector (K) and lattice constant. It was deduced a stimulated relation between (x) and (K). The results of TEM, they were clear that the lowest particle sizes investigated of BST powders nearly (36 - 50 nm).

Effect of Quartz Particle Size and Cement Replacement on Portland Limestone Cement Properties

This research focuses on investigating the effect of quartz particle size and cement replacement on their physicomechnical properties.Portland limestone cement(PLC)was employed and replaced with quartz powder(QP)at various particle sizes(1.19 mm,425μm,300μm,212μm,<212μm)and cement replacement between 2.5 wt.%~15 wt.%at interval of 2.5 wt.%to study their impact on the cement properties.The PLC chem­ical composition revealed a relatively low lime and high silica content compared to the conventional cement.QP revealed a high silica,lime and sulphur contents compared to natural sand.A high consistence,elongated setting times and lower strengths and specific gravities were observed as cement was replaced with QP at a given particle size respectively.The effect of replacing cement with QP content between 2.5 wt.%and 15 wt.%at various particle sizes resulted in average increments by 45.32%,23.13%and 36.06%for initial setting time,final setting time and water demand respectively.This increase could be related with clinker diminution cou­pled with enhanced QP surface area and clinker diminution.Similarly,an increase in the QP surface area at a given cement replacement led to higher water consistence,retarded setting times and lower strength.The effect of enhancing the QP’surface area between 1.19 mm and below 212μm at a given cement replacement resulted in average increments by 26.27%,8.61%and 7.49%for initial and final setting times and water demand respectively.The strength gain of the QP cement blend diminished significantly above 30%up to 15 wt.%cement replacement especially beyond 3 days.The low strength could be due to the high-water consistence linked with silica con­tent resulting in setting time retardation.The optimal QP content was deter­mined at 5 wt.%owing to the fact that the physicomechnical properties did not significantly deviate from the properties of control.

使用石英手性项进行归一化的宽带红外和频振动光谱方法的验证

和频振动光谱已被广泛用于表征各种界面、然而,对于某些界面。如担载粉末颗粒的界面,由于粉末会散射和频振动光谱信号使得光谱难以准确测量,获取高信噪比的和频振动光谱信号成为了一个巨大的挑战.本文发展了一种新的方法,在和频振动测量时,使用一片z切的α-石英晶体作为基底,担载少量催化剂粉末样品.该方法不仅可以通过石英晶体非共振电场的干涉放大界面颗粒上吸附分子的和频振动信号,并获得相位信息,还可以用于宽带红外和频振动光谱进行归一化.通过分离不同偏振的和频振动信号,能够分离并同时收集手性和非手性的和频振动信号.使用手性的和频振动信号来归一化非手性的和频振动强度,从而避免因担载物质到石英晶体上或由于不同时刻光的不稳定性引起的界面变化或者光重合差异.本文通过测量担载有MoC纳米粒子的石英基底上CH3OD的吸附来验证了本文的方法.无论界面情况如何,都能获得高信噪比的和频振动光谱.

绢云母石英片岩浮选尾砂提纯工艺研究

本研究利用绢云母石英片岩浮选云母后获得的石英尾砂为原料提纯制备了纯度99.9%高纯石英粉。研究结果表明,采用熔解-中和-灼烧提纯工艺,可打破SiO_(2)晶格内化学键,可使石英晶格中采用物理法提纯无法去除的气液包裹体类和类质同象类等杂质转移到熔液中,再通过固液分离使其得以有效去除而获得高纯石英粉。