SEM/EDS分析纳米TiN颗粒在SiC陶瓷中的分布状况

采用水基喷雾造粒技术制备SiC/纳米TiN复合粉体,并借助二步成型和无压烧结技术制备SiC/纳米TiN复合陶瓷,利用场发射扫描电镜结合能谱分析(SEM/EDS)研究了纳米TiN颗粒在SiC/纳米TiN复合粉体、素坯及烧结体过程中的分布状态,借此评价制备工艺。     

Cu颗粒包覆纳米SiC粉体的相分散性能分析

选用工业生产的纳米SiC粉料;利用歧化反应原理,分解出Cu颗粒,并与纳米SiC颗粒组成分散均匀的复合粉体;SEM和Auger电子探针形貌显示复合粉体颗粒呈球形;EDS、AES等检测结果表明,金属Cu颗粒包覆在纳米SiC颗料表面,从而使两相在纳米尺度范围内保持理想的均匀分散状态.     

TiN/聚吡咯纳米复合材料的制备及表征

采用氨解法制备了纳米氮化钛(TiN)粉体,对纳米TiN粉体进行表面改性,使其均匀分散到吡咯单体中.采用原位聚合法制备了TiN/聚吡咯(PPy)纳米复合材料.对合成的复合材料用X射线衍射(XRD)、透射电镜(TEM)、傅立叶变换红外光谱(FT-IR)、四探针测试仪等方法进行了表征与检测.结果表明:PPy成功地包覆在TiN纳米颗粒表面,形成了纳米TiN/PPy复合材料.复合材料具有优良的电性能.     

纳米TiN粉体在无水乙醇中的分散研究

应用超声、球磨等分散方法,分别以非离子型表面活性剂吐温-80、聚乙二醇1000、聚乙二醇1500及硅烷偶联剂A-1230为分散剂对纳米TiN粉末在无水乙醇中的分散性能进行了研究。分析了分散剂类型、分散剂用量、体系pH值、超声时间、球磨时间、球磨转速等因素对粉体分散效果的影响。采用分散相的沉降高度和沉降速率表征分散稳定性,试验结果表明硅烷偶联剂A-1230是纳米TiN粉体在无水乙醇中较为理想的分散剂,pH值和分散剂的用量存在一个最佳值,超声分散与球磨分散相结合是合适的分散工艺。当pH值为4、A-1230添加量为粉体质量的23%时,经10min超声处理、4h球磨后所得纳米浆料的分散效果最好,稳定时间可达6个月。对分散后的纳米TiN颗粒进行了TEM、SEM观察,纳米TiN均匀分散在无水乙醇中,颗粒平均粒径在20nm以下,纳米TiN在无水乙醇中的分散遵循空间位阻稳定机制和静电稳定机制。     

微-纳结构TiO2的制备及其紫外屏蔽性能研究

采用液相沉积法将纳米TiO₂负载于酸化微米TiO₂核体，制备具有微-纳结构的TiO₂复合粉体，然后以六偏磷酸钠为分散剂，获得具有优异防晒性能的分散浆。紫外线UV、透射电子显微镜和粒径测试结果表明，微米TiO₂和纳米TiO₂质量比为4∶3时，复合粉体紫外屏蔽性能最佳，且纳米TiO₂比较均匀地负载在微米TiO₂表面，此时粉体颗粒的粒径为312nm。模拟防晒乳液进行防晒测量，结果表明分散浆的紫外屏蔽性能优于复合粉体且具备更好的透明性。流变性能测试表明：分散浆为假塑性流体，具有剪切稀化特性，流动行为符合幂律模型且触变性较小可以长期存放；分散浆黏度随着温度升高而降低，在低固含量条件下，黏度对温度更为敏感。     

TiN-Al2O3纳米复合材料的力学性能和导电性能

以纳米TiN和α-Al2O3粉体为原料,采用球磨混合法制备了纳米TiN-Al2O3复合粉体,通过热压烧结得到致密烧结体.研究了纳米TiN颗粒对Al2O3材料力学性能和导电性能的影响,实验结果表明:在Al2O3基体中加入15vol％TiN纳米颗粒时,Al2O3材料的弯曲强度和断裂韧性分别从370MPa和3.4MPa·m1/2提高到690MPa和5.1MPa·m1/2,随着TiN添加量的增加,复合材料的电阻率逐渐降低,在25vol％TiN时达到最低值(6.5×10-3Ω·cm).     

歧化反应及置换反应制备Cu/纳米SiC复合粉体

为了实现Cu对纳米SiC的表面包覆改性,分别采用歧化反应和置换反应两种方法制备了Cu/纳米SiC复合粉体.利用扫描电子显微镜、透射电子显微镜和能谱仪研究了Cu/纳米SiC复合粉体的微观形貌、聚集状态、粒径以及Cu和纳米SiC的质量分数.实验结果表明:单个复合粒子的粒径约为100 nm;针对随机选择的两种方法制备的复合粉体的两个不同区域进行的分析表明,歧化反应条件下Cu的质量分数分别为37%和35%,成分均匀;置换反应条件下Cu的质量分数分别为79%和25%,成分差异大.歧化反应法比置换反应法的包覆效果好,实现了Cu对纳米SiC的均匀性包覆.     

TiN-Al2O3纳米复合材料的力学性能和导电性能

以纳米TiN和α-Al₂O₃粉体为原料,采用球磨混合法制备了纳米TiN-Al₂O₃复合粉体,通过热压烧结得到致密烧结体.研究了纳米TiN颗粒对Al₂O₃材料力学性能和导电性能的影响,实验结果表明:在Al₂O₃基体中加入15vol％TiN纳米颗粒时,Al₂O₃材料的弯曲强度和断裂韧性分别从370MPa和3.4MPa·m^1/2提高到690MPa和5.1MPa·m^1/2,随着TiN添加量的增加,复合材料的电阻率逐渐降低,在25vol％TiN时达到最低值(6.5×10^-3Ω·cm).     

脉冲电沉积纳米SiC/Ni-Co复合镀层腐蚀特性

采用X射线衍射(XRD)、扫描电镜(SEM)、能谱分析(EDS)研究了脉冲电沉积法制备的纳米晶Ni-Co合金镀层及其纳米 SiC/Ni-Co复合镀层的组织结构、表面形貌和成分。用浸泡法和电化学极化法对比测试了纳米晶Ni-Co合金镀层和纳米 SiC/Ni-Co复合镀层在3.5 wt% NaCl和5 wt% HCl溶液中的腐蚀行为。研究结果表明：通过脉冲电沉积法制备的Ni-Co合金镀层和纳米SiC/Ni-Co复合镀层具有典型的纳米晶结构;随着纳米SiC颗粒的增加,复合镀层的晶粒尺寸减小,硬度增加。所制备的纳米SiC/Ni-Co复合镀层颗粒分散均匀,其在3.5 wt% NaCl和5 wt% HCl溶液中的耐蚀性均优于纳米晶Ni-Co合金镀层。纳米晶Ni-Co合金镀层和纳米SiC/Ni-Co复合镀层在3.5 wt% NaCl溶液中的腐蚀速率极低,表现出极好的耐腐蚀性能,而在5 wt% HCl溶液中的腐蚀形态则表现为点蚀。     

SPE电解池催化剂载体的研究

采用氮化钛、碳化钛、碳化硅纳米粉体作为载体,制备担载型RuO2催化剂;并利用X-射线衍射(XRD)及电化学测试技术对样品进行表征.结果表明:纳米TiN、TiC粉体在高温煅烧时都发生了氧化反应,部分转化为TiO2,而纳米粉体SiC比较稳定,不发生化学反应,RuO2/SiC催化剂相比RuO2/TiC、RuO2/TiN催化剂也具有较好的析氧催化活性.     

半导体用高纯超细SiC粉体的表面改性

通过偶联剂预处理、接枝聚合丙烯酸钠两步法对SiC粉体进行表面改性,制备聚丙烯酸钠接枝改性SiC粉体,并对改性粉体进行表征,测试SiC粉体的zeta电位,讨论改性对SiC粉体料浆分散稳定性和流动性的影响。结果表明:SiC微粉经表面改性后并未改变原始SiC微粉的物相结构,只是改变其在水中的胶体性质;微粉团聚现象减少,分散性得到改善;改性SiC微粉与原始SiC微粉相比,表面特性发生很大变化,zeta电位值显著提高,悬浮液的分散稳定性得到明显改善,且黏度降低。     

超细球形空心磷铵灭火粉的制备与应用

采用气流和离心两种喷雾干燥方法制备超细球形空心磷酸二氢铵灭火粉,并添加甲基含氢硅油乳液、氟碳表面活性剂FK-510、羧甲基纤维素钠对粉体进行原位改性。结果表明:气流喷雾制备出的颗粒较细但不均匀,而离心喷雾制备出的颗粒均匀却较粗;表面活性剂甲基含氢硅油、FK-510的添加使粉体疏水性得到了很大提高;羧甲基纤维素钠的添加能使提高颗粒的球形度以及表面光滑度;喷雾干燥过程选择温度较低以及空气相对湿度较小的大气条件有利于制备高品质灭火粉。另外灭火实验结果表明:喷雾干燥制备的超细球形空心磷酸二氢铵灭火粉灭火效果明显优于某些市售灭火粉。     

水基注浆成型碳化硅坯体的研究

运用注浆成型技术制备了亚微米碳化硅陶瓷复杂部件坯体。研究了分散剂、pH值对SiC水基浆料粘度的影响,以及不同固含量的SiC水基浆料和脱气泡处理对坯体密度的影响。结果表明：选用的3种分散剂的分散效果大小顺序为：四甲基氢氧化铵（TMAH）〉聚甲基丙烯酸铵（PMAA）〉聚乙烯亚胺（PEI）,且3种分散剂的最佳加入量分别为：1．8wt％、0．8wt％、0．056wt%,最佳pH值为10。对固含量为55wt%的SiC浆料磁力搅拌抽真空脱气泡处理20min可以注浆得到密度为1.64g／cm^3的碳化硅坯体。     

等离子喷涂纳米结构Al_2O_3-TiO_2-SiO_2-SiC喂料的研究

纳米结构Al_2O_3、TiO_2、SiO-2、SiC粉体经过合理的预处理,经制浆并喷雾干燥,得到微米级粉体,然后将制备出的粉体进行1100℃烧结。着重研究实验条件对粉体制备的影响,利用扫描电镜观测粉体的形貌,通过XRD检测烧结前后物相的变化。结果表明:在喂料制备过程中发现,粉体的松装密度和搅拌时间是成两段线性关系,不同的喷雾造粒温度对粉体形貌有重要的影响。在250℃制得的粉体内部部分中空、结合强度高、球形度好。粉体经合适的温度烧结后,没有新物相生成,是适合等离子喷涂的纳米喂料。     

Preparing of nanostructured Al2O3–TiO2–ZrO2 composite powders and plasma spraying nanostructured composite coating

Nanostructured Al₂O₃–TiO₂–ZrO₂ composite powders for plasma spraying were prepared by spray drying granulation technology. The effects of processing parameters on the microstructure and properties of composite powders were investigated. The results show that with increasing the slurry solid content, the particle size of powders increases, and the bulk density of powders increases, and the flowability of powders increases firstly and then decreases. With increasing the binder content, the particle size of powders increases, and the bulk density of powders increases, and the flowability of powders increases firstly and then decreases. With increasing the spray drying temperature, the particle size of powders increases, and the bulk density and flowability of powders increases firstly and then decreases. The most appropriate spray drying parameters are the slurry solid content of 40 wt.%, the binder content of 2.0 wt.% and the spray drying temperature of 250 °C. The nanostructured composite coating was successfully prepared by using the as-prepared nanostructured Al₂O₃–TiO₂–ZrO₂ composite powders as feedstocks. The nanostructured coating possessed higher hardness and toughness compared with the conventional microstructured one, which was attributed to the use of the nanostructured composite powders feedstocks.     

Effect of pure-solvents without deflocculants for finer SiC particle dispersed MgO based composite

The deagglomeration process and its effects on the microstructure have been investigated for fine MgO, SiC powders and SiC particle added MgO mixed powders which were ball-milled under both polar- and non-polar solvent without deflocculants. During the drying, exothermic reactions are observed at 300–450 °C in MgO and SiC powders ball-milled in alcohol. On the other hand, no chemical reaction could be observed for the powders ball-milled using acetone, and nn-hexane. The observed exothermic reactions, then, are believed to be due to the oxide and/or oxide layer-alcohol reaction product formed during milling. This mechano-chemical reaction directly affects to deagglomerate during the drying process after wet-milling. Among the alcohol media, the well-dispersibility and deagglomeration of SiC powders as well as MgO powders seem to be reached by n-butyl alcohol, considering the balance between the steric effects and the dielectric constant of alcohol. These dispersion characteristics also effect on the microstructure of SiC particle dispersed MgO based composites.     

Fabrication and characterization of heat and plasma treated SiC/Al2O3-YSZ feedstocks used for plasma spraying

The SiC/Al₂O₃-YSZ (ZrO₂ + 8 wt.% Y₂O₃) powders with different SiC particle sizes were fabricated and treated from spray drying, heat treatment, and plasma spraying. The morphology, phase composition, flowability and density of powders were analyzed. The sphericity and flowability of powders treated by plasma flame are increased greatly, and the particle surface is very smooth. The flowability and density of powder with nano SiC were evident better than those of powder with submicron SiC. The optimum flowability and compactness of powder with submicron SiC is obtained when the critical plasma spray parameter is 341 and 325, respectively. For nano size SiC, the optimum flowability and the maximum compactness of powders are obtained with critical plasma spray parameter of 341. The grain size of powders is increased after heat treatment and plasma spraying. The SiC is oxidized to SiO₂ in the powders after heat treatment and plasma spraying. The Y₂O₃ dissolved from 8YSZ solid solution at higher critical plasma spray parameter. Besides, there is no phase transformation of ZrO₂ for powders. The metastable phase of Al₂O₃ appeared in feedstocks with submicron SiC, but no metastable phase was formed in feedstocks with nano SiC particles, which nano SiC can hinder the formation of Al₂O₃ metastable phase. The densification process and mechanism of reconstituted particles used for plasma spraying were analyzed from surface morphology, cross section and simulation.     

影响喷雾造粒Al2O3/nano-TiO2复合陶瓷粉体流动特性的流变学因素研究

本文研究了分散剂、粘结剂及固相含量等流变学因素对喷雾造粒粉体流动性的影响.结果表明,Al2O3/3wt.%nano-TiO2浆料具有剪切变稀的特性,有利于复合陶瓷粉体的喷雾造粒.当固相含量为浆料总质量的60%,分散剂和粘结剂分别为固相质量的0.3%和1.0%时,浆料具有合适的粘度和最佳的分散稳定性,喷雾造粒所得到的粉体形状为球形或近球形,具有较高的松装密度和良好的流动性,满足用于热喷涂的需要.     

短碳纤维增强碳化硅基复合材料的制备与力学性能

利用注浆成型结合反应烧结的方法制备了高强度短碳纤维增强碳化硅基复合材料, 研究了分散剂(四甲基氢氧化铵)的含量和混料时间对浆料粘度的影响; 短碳纤维的体积分数、碳化硅粉的粒径对复合材料微观结构和力学性能的影响。结果表明, 添加0.1wt%的四甲基氢氧化铵得到的浆料粘度最低, 混料时间控制在6 h为佳。添加35vol%短碳纤维的复合材料的弯曲强度达到(412±47) MPa。由5 μm粒径碳化硅粉制备的复合材料的力学性能最佳, 其弯曲强度可达(387±40) MPa。将5与50 μm粒径的碳化硅粉进行2 : 1混合后得到的复合材料的力学性能优异, 弯曲强度可达(357±41) MPa。