光催化纳米TiO2的低温液相制备及表征

以工业钛液为原料,通过低温液相法可以直接得到锐钛型纳米二氧化钛粉体.用X射线衍射(XRD)、高分辨率透射电子显微镜(HRTEM)、透射电子显微镜(TEM)、原子力显微镜(AFM)、激光粒度仪(LS)和N2-吸附脱附技术研究了制备的纳米TiO2粉体的晶型、形貌、晶粒尺寸、粒径分布及比表面积.在紫外光照下对哑甲基蓝的降解,评价了溶胶的光催化活性.结果表明,在低温下制备出结晶良好、细小品粒尺寸、高比表面积、分散性好的锐钛型纳米TiO2粉体粒子,且制备的TiO2溶胶显示出好的光催化活性.     

ZnO异质复合对纳米TiO2晶型转变和晶粒生长的影响

以TiCl4,ZnSO4溶液为原料,采用液相沉淀法制备了不同ZnO/TiO2摩尔比的纳米复合粉体.对合成的纳米复合晶的相变、晶粒生长过程以及紫外-可见光吸收性能进行了研究.结果表明:纳米TiO2经ZnO复合后,其晶型转变和晶粒生长均受到抑制.当ZnO为30%(摩尔分数)时,且采用氨水滴入TiCl4和ZnSO4溶液中的沉淀方式制备的ZnO/TiO2纳米复合晶的晶型转变和晶粒生长最缓慢.紫外-可见光吸收测试表明:800℃煅烧的ZnO/TiO2复合粉体的吸收强度比纯TiO2的高;900～1 050℃煅烧的复合粉体,虽然紫外区的吸收强度有所下降,但其光吸收带边比纯TiO2纳米晶的有显著红移.     

球磨法制备超细稻壳二氧化硅

将稻壳用10％(体积分数)的盐酸处理后在600℃焚烧得到稻壳二氧化硅,再利用球磨法进行研磨,得到平均粒径为5.01 μm、分散度为1.31的超细稻壳二氧化硅粉体.研究了研磨时间、球料比和磨球直径对粉体粒径的影响,并对研磨前后粉体的性质、红外光谱(FTIR)及X-衍射图谱(XRD)进行了比较.结果表明:合适的球料比、磨球...     

低温制备金红石型纳米TiO2粉体

利用TiCl4低温水解法,添加TiO2溶胶制备了纳米TiO2粉体.用X射线衍射、透射电子显微镜和激光粒度仪研究了制备的纳米TiO2粉体的晶型、形貌、晶粒尺寸及粒径分布.结果表明:所得纳米TiO2粉体原始沉淀为金红石型,其粒径为10 nm左右的棒状粒子,经500℃煅烧2h,获得结晶完整、球形、粒径分布很窄的纳米TiO2粉体,其平均粒径为34 nm,粒径分布范围为20～50 nm.     

机械法制备超细氧化铝粉体及其在ZTA陶瓷上的应用

采用机械研磨不同时间制备不同粒级的氧化铝(Al2O3)超细粉体,将该超细粉体应用于制备氧化铝一氧化锆(Al2O3-ZrO2,ZTA)复相陶瓷,研究了该超细粉体对ZTA复相陶瓷性能的影响.用氦气吸附法测萤Al2O3粉体的比表面积.用X射线透射沉降粒度仪、电超声粒度仪测定Al2O3粉体的粒径.研磨实验结果表明:微米级氧化铝原料经研磨可得到亚微米和纳米粒级产品,其中纳米Al2O3粉体平均粒径为70nm,比表面积大于115m2/g,X射线衍射表明:Al2O3晶形未发生变化,随着研磨时间的增加,Al2O3结晶度会降低、各晶面受到不同程度的破坏、晶相仍然是α相.将研磨制备的Al2O3超细粉体与15%(质量分数)的ZrO2复合并在不同温度F烧结ZTA陶瓷.经测试,ZTA在1 550℃烧结后,其体积密度最高可达到99%以上,抗弯强度最高可达到720 MPa,断裂韧性最高可达到6.86 MPa·m1/2,其机械性能优于用化学法制备的氧化铝超细粉体与15%质量分数)的ZrO2复合的ZTA陶瓷.     

掺钒TiO_2粉体的制备及物化性能研究

采用溶胶凝胶法制备得到掺钒TiO2溶胶,经3 h高温煅烧制成粉体;利用X射线衍射仪、X射线光电子能谱、紫外-可见分光光度计等对粉体的晶型、结构和吸光性能等进行了表征。结果表明:所制备的掺钒TiO2粉体均为锐钛矿型,粉体的吸收带边红移至600 nm左右。光催化实验表明,在可见光激发下,掺钒TiO2粉体对甲基橙的降解效果大于纯TiO2粉体。     

二氧化钛纳米管的合成及光催化性能

以纳米二氧化钛(TiO2,P25)为原料,通过水热法合成TiO2纳米管,同时,采用光沉积法将金属金(Au)或铂(Pt)负载于所合成的TiO2纳米管上,并对其进行了光催化性能的研究.用X射线粉末衍射仪、透射电子显微镜、紫外-可见分光光度计和比表面积法与孔径测定等仪器和方法对合成的样品进行表征.结果表明:合成出管径均匀且比表面积大于400 m2/g的TiO2纳米管.热处理结果表明:随着焙烧温度的增加,样品的比表面积减小.在焙烧过程中,TiO2的晶型由锐钛矿型向金红石型转变,TiO2纳米管的光催化活性高于P25纳米TiO2的.负载Au,Pt后,TiO2纳米管的光催化活性明显增加,且负载Au的样品在可见光区出现明显吸收峰,表明负载Au的Ti02纳米管有望成为可见光光催化剂.     

纳米SiO2/TiO2复合粉体的制备及表征

以Na2SiO3为原料,采用非均匀成核法在纳米TiO2基体上制备了SiO2表面保护膜层,通过红外光谱、X射线光电子能谱、扫描电镜、粒径测量、BET比表面积测量分析,证实纳米TiO2颗粒表面包覆了一层均匀致密的SiO2纳米膜,而且两者是以化学键合方式结合在一起。分散性能测试表明:纳米SiO2/TiO2复合粉体的分散性能明显提高。     

单模板法制备高活性锐钛矿型纳米二氧化钛

以聚乙二醇为模板剂,用溶胶凝胶法制备出高活性锐钛矿纳米TiO2。经XRD、TEM、BET-BJH测试表明:样品粒径约为10nm,比表面积为93m2/g。经TG-DTA、FTIR分析发现:冰醋酸在反应中与Ti形成螯合物,起到抑制钛酸丁酯的水解、缩聚和控制TiO2结晶生长的作用;而PEG与Ti结合进一步阻碍了晶体生长,使样品粒径降低。以3I-→I3-+2e-为模型反应,与商业品纳米TiO2粉体P-25相比来评价其光催化性能,结果显示,样品光催化活性高于商业品P-25。     

二氧化钛双粒径组合对染料敏化电池光电性能的影响研究

以不同粒径纳米TiO2粉体为原料,制备了单粒径TiO2薄膜以及双粒径TiO2组合薄膜,并测试了它们的光电转换性能。结果表明,以单粒径30 nm TiO2制备的薄膜光电转换效率最高,为6.28%;随着单粒径尺寸的增大或减小,TiO2薄膜的转换效率都降低;以粒径分别为45 nm和60 nm的TiO2等质量混合制备的薄膜在所有双粒径复合薄膜中光电转换效率最高,为4.62%。不同粒径组合膜层的性能差别可能是因为有效比表面积的不同所引起,而粒径组合引起的晶粒间隙大小和晶体自然比表面积间的协调又决定了样品间的有效比表面积。     

Ultrafine comminution of dental glass in a stirred media mill

A systematic study on the comminution of amorphous glass particles with complex composition (seven constituents) to produce nanoparticles has been performed in a high-energy stirred media mill. The influence of solids loading, dispersion stabilisation via pH and addition of dispersants on particle size was investigated in aqueous suspensions. Further, the effect of using 2-propanol and benzyl alcohol as dispersion media on the particle size and morphology is presented and compared to the aqueous system. The specific surface area of the product powder was analysed by the BET method, the secondary particle size was determined by static light scattering and the morphology was investigated by SEM and TEM. Dispersion viscosity and stability was measured using rotational viscosimetry and zeta-potential measurements, respectively. The results show that the solids loading plays a central role in the comminution efficiency, where lower loadings lead to finer particles after a given milling time. Stabilisation of the aqueous powder dispersion by adjusting the pH or by adding a dispersant did not result in an enhanced milling efficiency in terms of fast reduction of the particle size. The smallest glass nanoparticles with a primary particle size were achieved by a two-step comminution process. The particles were irregularly shaped when milled in water, however, when processed in 2-propanol and benzyl alcohol, they had a plate-like geometry.     

高温气相法可控制备纳米TiO2

通过火焰反应器结构设计，实现TiCl4高温气相氧化过程可控制备纳米TiO2粒子，新型火焰设计保证了TiCl4低温进入高温反应区，预热过程隔离保护喷嘴，避免了结疤堵塞;通过实验条件控制颗粒平均粒径和粒径分布，较低的TiCl4气相浓度、较高的载气流速有利于小粒径TiO2颗粒的生成。载气流速增加，中心TiCl4火焰形态由层流向湍流发展，焰长缩短，颗粒平均粒径减小。CH4燃气流量增加，高温反应区扩大，颗粒停留时间增加，颗粒尺寸增大。二次氧气的补充，提高了氧气与TiCl4的预混，有效地减小了产品TiO2颗粒的粒径。获得的TiO2产品平均粒径在20～80 nm之间。     

废旧轮胎橡胶的常温粉碎及性能研究

采用盘式磨设备对废旧轮胎胎面胶颗粒进行常温粉碎,研究胶粉性能及其对丁苯橡胶(SBR)硫化胶物理性能的影响,并与胎面胶颗粒进行对比。结果表明:常温粉碎胶粉的粒径比胎面胶颗粒降低了一个数量级,形状更加不规则且表面粗糙;动盘和定盘相对转速对常温粉碎胶粉粒径及其分布影响不大,但动盘和定盘间隙影响较大;常温粉碎胶粉的热稳定性比胎面胶颗粒低,且交联密度减小一半以上;与胎面胶颗粒相比,添加常温粉碎胶粉的SBR硫化胶的拉断伸长率有很大提高,但邵尔A型硬度、100%和300%定伸应力以及拉伸强度有所减小。     

Effect of Milling Treatment on the Particle Size in the Preparation of AIN Powder from Aluminum Polynuclear Complexes

Aluminum nitride powder was synthesized from aluminum polynuclear complexes. Basic aluminum chloride (BAC) provided the aluminum polynuclear complexes. The effect of the milling treatment for the precursor made from basic aluminum chloride and glucose on the particle size was investigated. BAC and glucose were dissolved in water and mixed homogeneously. AIN powder was obtained by calcining under a nitrogen gas flow after drying, milling by vibration mill, and precalcining at 800°C. Then excess carbon was removed by firing in air. It was found that the milling treatment affected the particle size of AIN powder and nitridation mechanism. Without the milling treatment, AIN powder was synthesized directly from the γ-alumina of an intermediate product. In using a milled precursor, however, α-alumina was formed during the calcining, and the particle size of the AIN powder obtained was about five times larger than that of AIN powder synthesized from a raw precursor. The formation of α-alumina phase began at the rather low temperature of 800°C. These results suggest that the mechanochemical effects added by the milling promotes the formation of α-alumina during calcining, and the α-alumina phase formed accelerates the particle growth. AIN powders obtained were very uniform. The oxygen content and the surface area of AIN powders synthesized from the raw and milled precursors were 2.9 wt% and 17.5 m²/g, and 1.1 wt% and 3.6 m²/g, respectively.     

Characterization of media mills based on mechanical energy applied to particles

This paper deals with the evaluation of characteristics of media mills having a different milling mechanism based on the mechanical energy applied to the particles to be processed during a milling treatment. Spherical copper powder was used as a stress-sensitive material and the milling treatment of the copper powder was carried out under various operating conditions using three types of media mills, a horizontal tumbling ball mill, vertical agitating ball mill and bead mill. The size distributions of copper powder before and after the milling treatment were measured and the deformation of copper particles was determined experimentally. The net energy applied to the copper powder was estimated from the plastic deformation of copper particles. It has been clarified that the applied energy depends strongly on the motion of media in the mill. By introducing two dimensionless parameters, which express the energy transfer efficiency from the kinetic energy of media to the particles and the motion of media in the mill, respectively, the media mills could be characterized on a uniform scale based on the applied energy regardless of milling mechanism.     

纳米TiO2半导体光催化性能的影响因素

TiO2以具有安全、廉价、无污染、适用范围广等优点而成为最有开发前途的绿色环保型光催化剂。以TiO2半导体为光催化剂的多相光催化氧化技术是几十年发展起来的一项污染治理新技术,具有良好的应用前景。文中主要从晶体结构、粒径、比表面积、表面羟基及载流子俘获剂5个方面,详细分析了这些因素对纳米TiO2光催化性能的影响。     

Optimization of milling parameters on the synthesis of stearic acid coated CaCO3 nanoparticles

Surface modification of precipitated calcium carbonate particles (calcite) in a planetary ball mill using stearic acid as a modification agent for making dispersion in hydrocarbon oil was investigated. Different parameters for processing (milling) such as milling time, ball-to-sample ratio, and molar ratio of the reactant were varied and analyzed for optimization. The physical properties of the hydrophobically modified calcium carbonate particles were measured; the particle size and morphology of the resulting samples were characterized by transmission electron microscopy and X-ray diffraction. The surface coating thickness was estimated using small angle X-ray scattering.     

The Effects of Operating Conditions on the Milling of Microcrystalline Cellulose

There is little detailed work relating the physical process that occurs during milling to the mechanical properties and mechanism of particle breakage. Very often, the selection of an appropriate mill and subsequently the determination of its optimum operating conditions are by trial and error. This paper look into optimizing the operating conditions of a ball mill through statistical analysis and the effect of temperature on the milling behavior of a common pharmaceutical excipient, microcrystalline cellulose (MCC). In addition, the bulk milling behavior of MCC is compared to its single particle breakage behavior. In this work, milling is conducted in a Retsch single ball mill where a bed of powder is subjected to impact by a steel ball in a horizontal cylindrical container. The container is vibrated horizontally at a set frequency, causing the ball to impact on the bed of particles. It is found that the finest MCC product can be achieved by milling a 2 g batch of material using a 12 mm ball size and at a frequency of 18 Hz. Temperature is found to have insignificant effect on the extent of breakage of MCC in both bulk milling and single particle impact testing. Milling and single particle impact experiments have both shown that MCC is more susceptible to breakage with increasing strain rate. In conclusion, the single impact tests could be used successfully for predicting the bulk milling behavior of the material, as shown in the case of MCC.     

Effect of high-energy ball milling on the microstructure and properties of ultrafine gradient cemented carbides

Planetary low-temperature high-energy ball mill was used for preparing the mixed powders with different particle sizes by adjusting the milling time. The ultrafine grain gradient cemented carbides were prepared by sinter-HIP treatment. The effects of milling time on the gradient formation, grain growth, and mechanical properties of ultrafine grain gradient cemented carbides were investigated. The results show that the high-energy ball milling cannot effectively reduce the particle size of mixed powder with short milling time. In addition, the particle size of the mixed powder is significantly reduced, while the specific surface area is significantly increased when the ball milling time exceeds 25 hours. The gradient layer thickness and the grain size increase at the beginning and then decrease when the mixed powder particle size was decreased. Simultaneously, the density, hardness, and fracture toughness of the alloy increase gradually. On the contrary, the number of WC with abnormal grain growth is significantly increased. The thickness of the gradient layer reached 32 μm, and the mean WC grain size is 314 nm. Based on the analyzed results, an optimized gradient layer thickness, grain size, density, and hardness can be obtained when the ball milling time is 35 hours.     

Optimized experimental design for natural clinoptilolite zeolite ball milling to produce nano powders

Nano powder of natural clinoptilolite zeolite was mechanically prepared by using a planetary ball mill. Statistical experimental design was applied to optimize wet and dry milling of clinoptilolite zeolite. To determine appropriate milling conditions with respect to the final product crystallinity, particle size and distribution, different milling parameters such as dry and wet milling durations, rotational speed, balls to powder ratio and water to powder ratio (for the wet milling) were investigated. Laser beam scattering technique, scanning electron microscopy and X-ray diffraction analyses were carried out to characterize samples. Results showed that larger than 1 mm particle size of clinoptilolite powder may mechanically be reduced into the size range of less than 100 nm to 30 μm by means of planetary ball milling.