球磨法制备天然辣椒素粉体工艺研究

以天然辣椒素和硅胶为原料和辅料,采用球磨法制备天然辣椒素粉体,采用正交实验法,对球料质量比、天然辣椒素与硅胶的质量比、球磨时间、球磨机转速等参数进行4因素3水平的正交实验设计,研究这些工艺参数对球磨法制备天然辣椒素粉体的影响。结果表明,制备天然辣椒素粉体的最佳工艺为球料质量比为5∶1,天然辣椒素与硅胶的质量比为4∶6,球磨时间为20 min,转速为300 r/min,在此条件下,制备的天然辣椒素粉体中粒径小于10μm的颗粒的体积分数为94.98%。     

牙科复合树脂中无机填料双峰混合体的堆积性能

通过测定用作牙科复合树脂中无机填料的粉体的振实密度 ,使用Mathematica和SAS/STAT软件 ,用统计学的方法得到了双组分粉体混合物的粒度分布与堆积体比容之间关系的经验公式。说明可以使用引入了粒度分布宽度作为变量的改良线性堆积模型预测双峰粉体的堆积密度。结论为双组分粉体大小粒径比相差越大 ,混合物堆积密度越高。该结论为优化牙科复合树脂的组成提供了理论依据     

聚乙二醇表面改性SiC粉体的物性表征

采用聚乙二醇(PEG 200)作为分散剂对工业用SiC粉体进行表面改性处理,通过TG、IR、电镜等测试技术研究了改性前后SiC粉体的流动特性、吸附、热重以及形貌等物性,分析了PEG加入量及液体介质对各种物性的影响.试验结果表明:PEG添加量为5%(质量分数),介质为乙醇时,改性SiC粉体流动特性较好;PEG在粉体表面的吸附量随PEG量的增加而增加,介质基本不影响吸附量;SiC粉体表面吸附的PEG可以烧尽;改性后颗粒之间分散较好,尺寸分布均匀,形状多为块状分布;粉体改性后碳化硅陶瓷制品的烧结性能得到改善.     

混合溶剂沉淀法制备纳米NiO及其表征

采用NiCl2·6H2O和Na2C2O4为原料,在混合溶剂乙醇 水溶液中,通过化学沉淀法制备出一种浅绿色前驱物,以前驱物的热分析结果为依据,在400℃分解3h可得产物NiO粉体。经XRD、比表面积测定和TEM分析表明,产物为平均粒径23nm且粒径分布均匀、无团聚的球形纳米NiO粉体。     

氯离子对氧化镁纳米粉体合成及烧结性能的影响研究

以无水碳酸钠和六水合氯化镁为原料,采用沉淀法,制备了纳米MgO粉体,重点考察了氯离子在粉体合成中的影响.研究表明,在沉淀工艺中掺入氯离子,可以改变先驱物的物相组成,获得以碱式碳酸镁和水合碳酸镁为主要组分的先驱物,在900℃煅烧后可以获得一次颗粒尺寸为40nm的MgO粉体.粉体制备中加入氯离子,烧结时具有促进氧化镁烧结致密化和晶粒长大的作用,同时还有利于获得晶粒尺寸分布均匀的显微组织.掺杂5%(质量分数)氯离子的粉体在空气气氛1200℃烧结3h,样品密度为96.4%,而相同条件下未掺杂氯离子样品的密度只有52.4%.     

应用水化硅酸盐纳米粉体制备块体材料

以磨细生石灰和硅质原料的混合物为前驱物,采用动态水热合成方法制备了水化硅酸盐纳米粉体.借助SEM、TEM及氮吸附等测试方法,分析了制得的水化硅酸盐粉体的形貌、粒径和比表面积.将制得的水化硅酸盐纳米粉体压制成块状固体.采用正交设计方法研究了成型压力、水泥掺量、纤维掺量、聚合物掺量等因素对块体材料力学性能的影响.结果表明:由该粉体压制成的块体材料立即具有强度和耐水性,且表观密度低;成型压力是影响其力学性能最显著的因素.     

复合添加剂的共沉淀法制备及ZnO压敏陶瓷研究

采用共沉淀法合成的复合添加剂粉体制备ZnO压敏陶瓷,用TG-DTA热分析沉淀物前驱体, 通过XRD、SEM、EDS和DLS表征复合粉体的物相、形貌、组成元素、粒度及其分布, 测试压敏陶瓷性能、并观察其结构.结果表明, 550℃煅烧前驱体生成各添加剂氧化物的混合物; 650℃煅烧1 h形成组成为(Bi_1.14Co_0.26Mn_0.29)(Sb_1.14Cr_0.57Ni_0.29)O_6.25焦绿石型复合添加剂粉体, 复合粉体平均粒径为0.26μm; 复合粉体制备的ZnO压敏陶瓷的电位梯度为330 V/mm、非线性系数为47、漏电流为5μA/cm², 电性能参数分别优于固相法混合添加剂粉体制备的压敏陶瓷, 这归因于复合粉体制备的压敏陶瓷具有更均匀的显微结构.     

钛酸丁酯有机相乙酐沉淀前驱物制备纳米晶体二氧化钛

钛酸丁酯和乙酐在低于100℃非水状态下生成非晶钛氧有机化合物，经焙烧得到纳米二氧化钛晶体。差热分析表明，表面吸附物和键合有机基团在314－389℃之间发生氧化和分解而除去，389－405℃之间无定形粉体转化为锐钛矿型晶体；热重分析中，表面物理吸附物失重10．60％，键合有机基团失重46．55％。制备的纳米二氧化钛为球形粒子，粒径为10－30nm。     

水热合成法制备银-氧化锡复合粉体备

采用水热合成法,以亚硫酸钠为还原剂,用硝酸银、氨水和锡酸钠为原料制备银-氧化锡复合粉体,对制备的粉体进行X射线衍射、扫描电镜和能谱分析。结果表明:采用水热合成法可以制备出银-氧化锡颗粒,颗粒近似球形,粒径约为400 nm;该粉体由银和氧化锡两种物相组成,银的衍射峰非常明显,银元素和锡元素在粉体中均匀分布,可以推断银和氧化锡的分布是均匀的。     

水相炭基溶胶—凝胶法制备纳米炭粉的研究

以高温煤焦油沥青为炭源,经浓硝酸和浓硫酸混合物在30℃氧化制备出较高收率的水性中间相沥青。将水怀中间相沥青溶于氨水溶液得到水相炭基凝胶,经过乙醇与水直接交换后超临界干燥和热处理制备出颗粒分布均匀、平均尺寸在10nm左右的无定型碳纳米粉。并采用透射电子显微镜、傅立叶红外光谱、热重、物理吸附、X－射线衍射等分析手段对纳米炭原粉在热处理过程中的物理化学变化规律进行了表征。     

形核密度对AlON粉体合成及其透明陶瓷制备的影响

以α-Al₂O₃为原料, 采用碳热还原氮化法合成AlON粉体, 利用活性炭和亚微米碳粉改变球磨后一次粉体(α-Al₂O₃和C混合粉体)的形核密度, 并研究形核密度对AlON粉体相组成、形貌及其透明陶瓷透光性的影响。结果表明, 形核密度不同的一次粉体在1750℃保温60 min均能合成纯相AlON粉体, 但是所合成的两种AlON粉体形貌和性能差异较大。高形核密度下(添加活性炭)合成的AlON粉体形貌不规则、结构疏松且晶粒较小, 并易于球磨获得细颗粒粉体(~0.93 μm); 而低形核密度下(添加亚微米碳粉)合成的AlON粉体整体形貌呈近球形, 晶粒发育较完整, 且尺寸较大, 该粉体球磨后颗粒尺寸较大(~2.13 μm)。因此, 形核密度是影响AlON粉体形貌、结构特征和破碎性的主要因素。研究结果表明, 高形核密度粉体合成的AlON粉体具有更好的烧结活性, 它在1880℃保温150 min获得的透明陶瓷最大红外透过率达76.5% (3 mm厚), 比低形核密度粉体制备的透明陶瓷提高48.3%。因此, 以α-Al₂O₃为原料时, 提高形核密度有利于制备颗粒较小的高活性AlON粉体, 该粉体适合制备高透过率AlON透明陶瓷。     

Density Gradients in Multilayer Compacted Iron Powder Parts

The use of multilayer compaction to form powder metal (P/M)components, is encouraging. With this process, a part is formed by successively compacting layers of powder. The formation of parts with larger than conventional height to diameter ratios is possible. Multilayer compaction also reduces the density gradients normally observed in large parts from conventional double action compaction. Optimization of the layer thickness based on the powder characteristics can lead to greatly reduced density gradients.

The physical properties of multilayer compacted components are investigated as a function of layer thickness. The research has been performed with two iron powders of varying characteristics. The compressibility of the powder versus the layer thickness is discussed and related to the density distribution in the component.     

Fe/C复合纳米炭粉的制备及其磁学性能研究

以高温煤焦油沥青为原料,以体积比7∶3的浓硫酸和浓硝酸混合酸为氧化剂,制备水性中间相沥青;采用溶胶-凝胶法先形成碳基溶胶,加入FeCl3后进一步形成复合Fe/C凝胶;凝胶经醇水交换、常温干燥和900℃炭化制备出Fe/C复合磁性纳米炭粉。利用FT-IR、XRD、TG和TEM等对水性中间相沥青、磁性纳米炭原粉以及磁性纳米炭粉进行表征。结果表明:采用溶胶-凝胶和常温干燥的方法可以制备出粒度均匀、形状近似于椭圆形的Fe/C复合磁性纳米炭;其磁性纳米炭粉的平均粒径约5 nm,以聚集成粒度为20 nm～30 nm的团聚体形式存在。磁性纳米炭粉中的碳以无定型结构的形式存在,Fe元素以α-Fe、Fe2O3和Fe3C的形式存在,Fe/C复合磁性纳米炭粉具有软磁性和较高的磁响应性。     

NiAl-B composites with nanocrystalline intermetallic matrix produced by mechanical alloying and consolidation

Powder mixtures with equiatomic Ni–Al stoichiometry and with the addition of 5, 10, 20 and 30 vol% of boron were mechanically alloyed in a high-energy SPEX mill. Differential scanning calorimetry (DSC) was used for examination of the thermal behaviour of the milled powders. The mechanically alloyed powders and powders after DSC examinations were investigated by X-ray diffraction (XRD). For all the powder mixtures, a nanocrystalline NiAl intermetallic phase was formed during milling. With the increase of boron concentration in the mixtures, more intense refinement of the NiAl grain size during mechanical alloying was observed. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) examinations showed that the produced powders have composite structure, with boron particles uniformly distributed in the nanocrystalline NiAl intermetallic matrix. The density of the composite powders decreases with the increase of boron content, following the rule of mixture.The produced powders were subjected to consolidation by hot-pressing at 800 °C under the pressure of 7.7 GPa for 180 s. The produced bulk materials were investigated by XRD, SEM and EDS as well as characterised by hardness, density and open porosity measurements. It was found that during applied consolidation process the nanocrystalline structure of the NiAl matrix was maintained. The average hardness of the bulk composite samples is in the range of 10.58–12.6 GPa, depending on boron content, increases with the increase of boron content, and is higher than that of the NiAl intermetallic reference sample (9.53 GPa). The density of the bulk composite samples is the same as that of the corresponding powders after milling, decreases with the increase of boron content and is lower than that of the NiAl reference sample. To the best of our knowledge, the NiAl-B composites with nanocrystalline intermetallic matrix have been produced for the first time.     

Supersaturation produces high bioavailability of amorphous danazol particles formed by evaporative precipitation into aqueous solution and spray freezing into liquid technologies

The bioavailability of high surface area danazol formulations was evaluated in a mouse model to determine what effect high supersaturation, as measured in vitro, has on the absorption of a poorly water soluble drug. Danazol, a biopharmaceutics classification system II (BCS II) compound, was used as the model drug. Evaporative precipitation into aqueous solution (EPAS) and spray freezing into liquid (SFL) technologies were used to prepare powders of danazol/PVP K-15 in a 1:1 ratio. The evaporative precipitation into aqueous solution (EPAS) and SFL compositions, physical mixture and commercial product were dosed by oral gavage to 28 male Swiss/ICR mice for each arm of the study. Samples were taken at time points ranging from 0.5 to 24 h. Pooled mouse serum was analyzed for danazol by high performance liquid chromatography (HPLC). Powders were analyzed for their ability to form supersaturated solutions through dissolution at concentrations of 1 mg/mL which was the dose delivered to the mouse models. Spray freezing into liquid (SFL) and EPAS compositions displayed higher C(max) at 392.5 ng/mL and 430.1 ng/mL, respectively, compared to the physical mixture (204.4 ng/mL) and commercially available danazol (199.3 ng/mL). The T(max) for all compositions studied was near the 1 h time point. The area under the curve (AUC) for the SFL composition was 2558 ng.h/mL compared to EPAS composition at 1534 ng.h/mL. The area under the curve (AUC) for the physical mixture and commercially available danazol were 672 ng.h/mL and 1519 ng.h/mL, respectively. The elimination rate constants for the EPAS composition, SFL composition, and physical mixture were similar at approximately 0.15 h(-1) where as the commercially available danazol capsules displayed an elimination rate constant of 0.103 h(-1). The extent of danazol absorption in the mouse model was higher for SFL composition compared to the less amorphous EPAS composition, physical mixture, and commercially available danazol powders. Both EPAS and SFL compositions were able to form supersaturated solutions. However, the SFL composition displayed a supersaturation of 33% above control and was able to maintain supersaturation for 90 min compared to the EPAS composition (27% supersaturation above control for 60 min). Through the use of a testing method for supersaturation, it was found that EPAS and SFL compositions achieve higher apparent solubilities when compared to the physical mixture and commercially available danazol capsules. Because of the greater extent of dissolution of the SFL composition, the bioavailability was enhanced in a mouse model.     

On the Use of Ball Milling for the Production of Ceramic Powders

In the present research work, the mixture of boron carbide and graphite ceramic powders with a theoretical composition of 50% each by weight were mechanically alloyed in a laboratory ball mill with different milling times of 12.5, 25, 50, 75, and 100 h. The investigation was carried out on the morphologies and densities of ball-milled powders. Morphology results revealed that ball milling is a very dominant and dynamic practice for preparation of two different powders into single entity powder having appropriate and consistent morphology. The results of density measurement showed that with milling times, density increased initially and then reduced with further increase in milling times. The density is reduced by 1.68% as the milling time increased from 0 to 100 h.     

Mn-Ce oxide as a high-capacity adsorbent for fluoride removal from water

A novel Mn-Ce oxide adsorbent with high sorption capacity for fluoride was prepared via co-precipitation method in this study, and the granular adsorbent was successfully prepared by calcining the mixture of the Mn-Ce powder and pseudo-boehmite. High-resolution transmission electron microscopy (TEM) image showed that the Mn-Ce adsorbent consisted of about 4.5 nm crystals, and X-ray diffraction (XRD) analysis indicated the formation of solid solution by Mn species entering CeO(2) lattices. The surface hydroxyl group density on the Mn-Ce adsorbent was determined to be as high as 15.3 mmol g(-1), mainly responsible for its high sorption capacity for fluoride. Sorption isotherms showed that the sorption capacities of fluoride on the powdered and granular adsorbent were 79.5 and 45.5 mg g(-1) respectively at the equilibrium fluoride concentration of 1 mg L(-1), much higher than all reported adsorbents. Additionally, the adsorption was fast within the initial 1 h. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that the hydroxyl groups on the adsorbent surface were involved in the sorption of fluoride. Both anion exchange and electrostatic interaction were involved in the sorption of fluoride on the Mn-Ce oxide adsorbent.     

Effect of ball milling on the physical and mechanical properties of the nanostructured Co–Cr–Mo powders

In the present study, Co-based machining chips (P1) and Co-based atomized alloy (P2) has been processed through planetary ball mill in order to obtain nanostructured materials and also to comprise some their physical and mechanical properties. The processed powders were investigated by X-ray diffraction technique in order to determine several microstructure parameters including phase fractions, the crystallite size and dislocation density. In addition, hardness and morphological changes of the powders were investigated by scanning electron microscopy and microhardness measurements. The results revealed that with increasing milling time, the FCC phase peaks gradually disappeared indicating the FCC to HCP phase transformation. The P1 powder has a lower value of the crystallite size and higher degree of dislocation density and microhardness than that of the P2 powder. The morphological and particle size investigation showed the role of initial HCP phase and chemical composition on the final processed powders. In addition results showed that in the first step of milling the crystallite size for two powders reach to a nanometer size and after 12 h of milling the crystallite size decreases to approximately 27 and 33 nm for P1 and P2 powders, respectively.     

富硅镁镍渣粉磨细度和掺量对硅酸盐水泥水化特性的影响

通过机械粉磨,将富硅镁镍渣(简称"镍渣")粉磨至微米级,制得的镍渣用作水泥混合材部分替代硅酸盐水泥熟料。测试并分析了镍渣的化学组成、细度、筛余量、体积安定性及孔结构。结果表明:4种镍渣的细度均大于硅酸盐水泥熟料,使得水泥颗粒密度随着镍渣掺量增加而减小;镍渣的胶凝活性低于硅酸盐水泥熟料,使得掺有镍渣的水泥粉末水化反应放热量降低,并伴随有缓凝现象,但随镍渣细度提高,有助于改善其反应活性;掺入镍渣不利于硬化水泥砂浆的抗压强度、抗折强度发挥,提高镍渣细度,则由于紧密堆积效应可改善力学性能;镍渣中的MgO不以f-MgO形式存在,使得硬化水泥浆体的体积安定性合格。