溶胶-凝胶和碳热还原法合成碳化硅晶须的研究

以工业硅溶胶和炭黑为主要原料，用溶胶－凝胶和碳热还原法合成了SiC晶须，获得的产物中碳化硅质量分数高于95％，碳化硅晶须质量分数高于74％，碳化硅晶须为直线形，具有光滑的表面，直径为0．2－0．5μm，长径比约为50－200，对影响碳化硅晶须产率和微观结构的主要因素进行了研究，结果表明：采取原料中碳含量稍多于理论值，并且严格控制反应温度，使得碳化硅的生成速度与碳化硅晶须的形成速度相匹配的措施对于提高产物中的碳化硅晶须含量是非常有效的。     

溶胶-凝胶-碳热还原法制备富碳β-SiC纳米粉体

采用溶胶-凝胶-碳热还原法,以正硅酸乙酯和蔗糖为原料,在0.1 MPaAr气气氛中碳热还原合成β-SiC纳米粉体。通过X射线衍射、Raman光谱、扫描电镜和透射电镜对β-SiC纳米粉体的物相、微观结构及形貌进行了表征。结果表明:当合成温度为1 600℃时,已经开始生成β-SiC相,随着温度升高至1 700℃,完全生成了含有C_(Si)缺陷的富碳β-SiC相。β-SiC纳米粉体表现为纳米级的团聚颗粒,平均粒径为40 nm,并生成晶须。对β-SiC纳米粉体的碳热还原反应机理进行了分析,结果表明:溶胶-凝胶法明显降低了生成气态SiO控制反应的温度。     

溶胶-凝皎-碳热还原法制备富碳β-SiC纳米粉体

采用溶胶-凝胶-碳热还原法,以正硅酸乙酯和蔗糖为原料,在0.1 MPaAr气气氛中碳熟还原合成β-SiC纳米粉体.通过x射线衍射,Raman光谱、扫描电镜和透射电镜对β-SiC纳米粉体的物相、微观结构及形貌进行了表征.结果表明:当合成温度为1 600℃时,已经开始生成β-SiC相,随着温度升高至1 700℃,完全生成了含有Csi缺陷的富碳β-Sic相.β-SiC纳米粉体表现为纳米级的团聚颗粒,平均粒径为40nm,并生成晶须.对β-SiC纳米粉体的碳热还原反应机理进行了分析,结果表明:溶胶-凝胶法明显降低了生成气态SiO控制反应的温度.     

溶胶--凝胶碳热还原法制备硼化锆超细粉体

以氧氯化锆、硼酸、葡萄糖等为原料,在柠檬酸和乙二醇的螯合作用下,采用溶胶--凝胶、碳热还原工艺合成了ZrB2超细粉体。研究了原料配比及合成温度对合成超细粉体的影响。结果表明:不同的B/Zr及C/Zr摩尔比显著影响ZrB2超细粉体的合成,其最佳摩尔比为:n(B)/n(Zr)=2.5,n(C)/n(Zr)=6.5;当热处理温度为1 773K时能够合成纯相的ZrB2超细粉体;1 773K保温2h条件下合成的ZrB2超细粉体的颗粒尺寸为1~2μm,晶粒尺寸为55nm。     

非水解溶胶-凝胶碳热还原氮化法制备TiN薄膜研究

以四氯化钛和无水乙醇为前驱体原料,按C/Ti摩尔比为12:1引入聚乙烯吡咯烷酮(PVP,分子量为1 300 000)作为碳源,采用非水解溶胶-凝胶碳热还原氮化技术,在流量为30ml/min高纯N2中,经1300℃碳热还原氮化5h,在石英基片上制备出具有金黄色光泽的TiN薄膜。利用XRD、RAMAN和FE-SEM表征TiN薄膜物相组成及显微结构,结果表明:薄膜为具有NaCl型面心立方结构的δ-TiN晶相,薄膜中TiN晶体在其最小应变能晶面(111)择优生长,部分晶粒呈棱角分明的三棱椎状,晶界清晰,薄膜厚度在200nm左右。镀有TiN薄膜的石英基片,在可见光范围内透过率峰值为13%,在近红外区域的反射率接近70%。     

溶胶-凝胶和微波碳热还原氮化法合成β-sialon超细粉

以正硅酸乙酯(tetraethoxysilane,TEOS),硝酸铝,蔗糖等为原料,通过溶胶-凝胶和微波碳热还原氮化法合成了β-sialon超细粉.研究了铝碳摩尔比、温度、埋粉条件、晶种、添加剂等工艺条件对合成β-sialon超细粉的影响.结果表明:铝碳摩尔比显著影响β-sialon超细粉的合成,过量碳有利于形成β-sialon超细粉.1573～1623 K为最佳合成温度.埋粉不利于β-sialon超细粉的合成.晶种对β-sialon超细粉的合成没有显著影响,添加剂Fe2O3对反应有明显促进作用.用场发射扫描式电子显微镜观察产物的显微形貌,结果表明:合成β-sialon超细粉的粒度大约为100nm.     

非水解溶胶-凝胶碳热还原氮化法制备TiN粉体研究

首先,以四氯化钛为原料,异丙醚为氧供体,二氯甲烷为溶剂,采用非水解溶胶凝胶法合成高活性的TiO2凝胶;其次以其为钛源,选用分子量为1300000的聚乙烯吡咯烷酮为碳源,采用碳热还原氮化法合成TiN粉体。X射线衍射仪、场发射扫描电镜和激光粒度仪测试结果表明,与水解法相比,采用非水解法合成的TiO2凝胶经800℃煅烧0．5h仍为活性较高的锐钛矿相,以该凝胶为钛源,经1200℃碳热还原氮化2h可合成纯度相对较高的TiN粉体,将合成温度升至1300℃还原氮化5h可合成更高纯度的TiN粉体。TiN粉体颗粒呈近似球形,发育较好,粒径在1μm以下,激光粒度测定粒径主要集中在10μm左右,d50为8μm。     

非水解溶胶—凝胶碳热还原氮化法制备TiN粉体研究

首先,以四氯化钛为原料,异丙醚为氧供体,二氯甲烷为溶剂,采用非水解溶胶-凝胶法合成高活性的TiO2凝胶;其次以其为钛源,选用分子量为1 300 000的聚乙烯吡咯烷酮为碳源,采用碳热还原氮化法合成TiN粉体。X射线衍射仪、场发射扫描电镜和激光粒度仪测试结果表明,与水解法相比,采用非水解法合成的TiO2凝胶经800℃煅烧0.5h仍为活性较高的锐钛矿相,以该凝胶为钛源,经1 200℃碳热还原氮化2h可合成纯度相对较高的TiN粉体,将合成温度升至1 300℃还原氮化5h可合成更高纯度的TiN粉体。TiN粉体颗粒呈近似球形,发育较好,粒径在1μm以下,激光粒度测定粒径主要集中在10μm左右,d50为8μm。     

以酚醛树脂为碳源碳热还原制备TiC的研究

本文以硫酸氧钛和酚醛树脂为原料在氩气保护下高温固相合成TiC微粉.以硫酸氧钛为钛源,酚醛树脂为碳源,通过液相混合的方式提高了钛源和碳源的混合均匀性,从而有利于促进后期固相合成反应的进行,并保证产物的均一性.探讨了酚醛树脂和硫酸氧钛的高温碳热还原过程,用TG、FTIR、XRD对前躯体和碳热还原后的产物进行了表征和研究.结果表明,通过边搅拌边加热的方式可以获得硫酸氧钛和酚醛树脂的均匀混合物前驱体,该前驱体在流通的氩气环境中经1500℃碳热还原反应1h可得到物相纯净的TiC微粉,产物平均粒径为200 nm.     

非水解溶胶-凝胶Al2O3碳热还原氮化合成AlN超细粉

以无水氯化铝和异丙醚为原料,利用非水解溶胶-凝胶法制备出高活性Al2O3凝胶,以其作为铝源,引入炭黑作为碳源,利用碳热还原氮化技术低温合成AlN超细粉体。研究了凝胶未经煅烧以及预煅烧温度分别为300、500℃,按n(C)/n(Al2O3)为3.9、7.8和9.6分别加入不同量的炭黑,1 400、1 450和1 500℃的合成温度以及N2流量分别为40和80 mL·min-1时对AlN粉体合成的影响。结果表明:Al2O3凝胶经300℃预煅烧后,按n(C)/n(Al2O3)=7.8与炭黑混合,在流量为80 mL·min-1的高纯N2中于1 450℃保温2 h后可以合成出高纯AlN超细粉体。FE-SEM分析表明,AlN超细粉体平均粒径在400 nm左右,分散较为均匀。     

碳热还原氧化法制备氧化镁粉体研究

为提高镁质含碳耐火材料中氧化镁的利用率,对该材料中的氧化镁进行提纯。以废弃镁质含碳耐火材料为原料,设计感应加热装置模型,利用感应炉加热系统对含碳原料加热,用碳热还原氧化法将废弃镁质含碳耐火材料中的氧化物在高温还原气氛下,还原成气相并在空气中氧化形成氧化镁粉体。经化学分析、XRD、SEM等测试发现,氧化镁粉体材料中氧化镁含量大于98%(质量分数),氧化镁粉体晶粒粒径为2～3μm,尺寸均匀。通过热力学分析,采用碳热还原氧化法还原生成的SiO气相在氧化过程中受到了Mg(g)、Ca(g)钙气相氧化的抑制作用。     

高炉瓦斯泥碳热还原脱锌研究*

利用碳热还原方法,开展了高炉瓦斯泥焙烧脱锌实验研究。研究结果表明,碳热还原焙烧高炉瓦斯泥可有效脱除高炉瓦斯泥中的锌。最佳工艺条件为：焙烧温度为1 423 K,焙烧时间为180 min,物料粒径为9.5～10.5 mm。在最佳工艺条件下,高炉瓦斯泥脱锌率达99.2%,焙烧剩余渣中锌质量分数低于0.15%,可返回高炉使用。     

锆英石碳热还原制备ZrB2-ZrO2-SiC复合粉体

以锆英石、硼酸和炭黑为原料,在流通氩气气氛中于1 500℃煅烧制备ZrB₂-ZrO₂-SiC复合粉体,研究了保温时间（分别为3、6和9 h）和添加剂AlF₃添加量（质量分数分别为0、0.5%、1.0%、1.5%、2.0%和2.5%）对合成产物物相组成和显微结构的影响。结果表明：1)将锆英石在流通氩气气氛中于1 500℃碳热还原可制备ZrB₂-ZrO₂-SiC复合粉体;ZrB₂、ZrO₂呈粒状,SiC呈纤维状。2)随着保温时间的延长,ZrB₂的量逐渐增多,m-ZrO₂和SiC的量均逐渐减少,非氧化物ZrB₂、SiC、ZrC的总量逐渐增多。3)与未添加AlF₃的试样相比,添加0.5%（w）AlF₃的试样中m-ZrO₂量显著减少,ZrB₂的量显著增多,SiC的量有所减少;但随着AlF     

Photoluminescence property of inexpensive flexible SiC nanowires membrane by electrospinning and carbothermal reduction

Silicon carbide nanowire (SiC NW), as a typical wide band gap semiconductor was used as light-emitting materials and devices in high-temperature and harsh environments due to its excellent properties. In this paper, flexible ultra-long SiC NWs membrane was successfully synthesized by electrospinning and subsequently high-temperature sintering using phenolic resin and silica sol as precursors. Results of system characterization reveal that SiC NWs possess a smooth and uniform surface with diameter distribution mainly between 50-300 nm and a length of more than tens of micrometers, forming a network structure. The growth mechanism of synthesized nanowires was mainly carbothermal reduction in situ and was accompanied by vapor-solid (V-S) reaction. The present work provides a simple and cost-effective way for controllable fabrication of SiC NWs membrane. The photoluminescence spectrum of SiC NWs membrane emerged a clear blue shift, indicating a potential application in optoelectronic devices and discussed the potential applications of SiC NWs membrane in other fields.     

Formation mechanism of Ti4O7 phase prepared by carbothermal reduction reaction

The unique structure of Ti₄O₇ endows it with excellent properties such as outstanding electrical conductivity and corrosion resistance, which makes it one of the most promising electrode materials in the electrochemical field. Carbothermal reduction reaction (CRR) is widely used to synthesize Ti₄O₇, while thermodynamics, kinetics, and reaction mechanism are still limited. Besides, the purity of Ti₄O₇ powders prepared by CRR is also relatively low. It's necessary to study the reaction mechanism of CRR and synthesize single-phase Ti₄O₇. In this work, the unknown thermodynamic data were firstly assessed by the rule of oxygen potential increasing with oxygen mole fraction in oxides. In addition, the isothermal thermal analysis suggested that the reduction process was composed of interfacial and diffusion-controlled reactions. The activation energy of the two stages was 272.0 and 325.4 kJ mol⁻¹ respectively. Based on this, single-phase Ti₄O₇ was successfully synthesized, and a core-shell model of the reaction mechanism was proposed and well verified by the TEM results. This study provided an in-depth and systematic analysis of the CRR process, and it is significant to realize the preparation of single-phase Ti₄O₇.     

Thermodynamic and kinetic analyses of vacuum synthesis of AlN by the alumina carbothermal reduction nitridation method

Ultrafine single-phase aluminium nitride (AlN) particles were successfully synthesized by the vacuum carbothermal reduction nitridation (VCRN) method at shorter times and lower temperatures. The mechanism of the process was investigated. By analyzing the X-ray diffraction (XRD) patterns and thermodynamic calculations, the main reaction path was determined to be Al₂O₃→Al₂CO→Al₄C₃→Al₅C₃N→AlN. By investigating the kinetics mechanism, the process was a gas–solid reaction model, which was controlled by the crystalline chemical reaction from 0.5  to 1.5 h, combination control from 1.5 to 2 h, and gas diffusion control from 2 to 2.5 h. Moreover, the apparent activation energy (E_a) was calculated from the nitridation ratio, the value obtained, 237.71 kJ mol^–1, is 31% of the energy reported for the conventional synthesis method. These results show that ultrafine AlN could be effectively synthesized at 1823–1873 K and 300 Pa N₂ pressure for 2.5 h.     

碳热还原氮化法合成氮化钒/氮化铬复合粉末的研究

以纳米V2O5、纳米Cr2O3和纳米碳黑为原料,经过干燥、球磨混料后,在流动氮气气氛中焙烧得到了氮化钒/氮化铬复合粉末。利用XRD、TG-DSC、SEM、BET和TEM对合成产物进行了分析。结果表明：在1200 ℃、2 h条件下,可制备出平均晶粒尺寸为40 nm的VN/CrN复合粉末。复合粉末主要由VN、CrN和VCrN2组成。这3种物质均为面心立方结构,空间群均属于Fm3m。将复合粉末作为添加剂加入到陶瓷磨具结合剂中进行性能测试,结果显示：当w（复合粉末）=0.2%时,可使陶瓷磨具结合剂抗折强度和流动性分别提高约20%和50%。当w（复合粉末）=1.0%时,其抗折强度和流动性均达到最大值。     

Morphological features of porous silicon carbide obtained via a carbothermal method

Samples of porous silicon carbide were obtained using sucrose or carbon and aerosil or silica mesoporous molecular sieves (SBA‐3, SBA‐15, KIT‐6 and MCF). Fibers content in silicon carbide samples is higher when the mesopore surface area of carbon materials derived from carbon‐silica composites is lower. Based on the found correlation between the morphology and porosity of SiC and mesopore surface area of the carbon component in the composites, a templating action of carbon in carbothermal reduction was suggested.     

碳热还原氮化合成TiN的研究

以锐钛矿(中位径0.38μm)、金红石(中位径4.58μm)和鳞片石墨(粒度<0.15mm)、炭黑(平均粒度0.02μm)、可膨胀石墨(粒度<0.15mm)为原料,固定配比nC∶nTiO2为5∶1时分别组成不同的原料组合,并以锐钛矿和鳞片石墨为原料,改变配比nC∶nTiO2分别为3∶1、4∶1、5∶1、6∶1、7∶1和8∶1进行配料,在管式电炉、流动N2中分别于1300℃和1400℃制备了TiN,并进行了合成产物的氧化脱碳试验;采用XRD测定TiN的特征峰(d200=0.212nm)强度,以表征TiN的合成率,研究了原料粒度、反应物活性、反应温度等因素对TiN合成率的影响。结果表明:选用粒度较细或晶格活性大的原料,提高反应温度,均有利于提高TiN粉末的合成率;合成TiN粉末的最佳原料组合是可膨胀石墨和锐钛矿;以鳞片石墨和锐钛矿为原料时,其配比为nC∶nTiO2=6∶1时TiN合成率最高;合成产物中均含有一定量的碳,采用普通的加热氧化法不能除碳,其原因是TiN的氧化温度低于石墨的。     

Synthesis of rod-like ZrB2 crystals by boro/carbothermal reduction

Rod-like ZrB₂ crystals were synthesized at 1600 °C in Ar atmosphere by boro/carbothermal reduction using ZrOCl₂⋅8H₂O, B₄C and carbon powders as raw materials. The optimum molar ratio of raw materials required to form pure ZrB₂ grains was found to be 2: 1.2: 3. With increase in temperature and subsequent heat preservation stage, ZrB₂ powders grew into a rod-like morphology along the c axis. The rod-like ZrB₂ grains obtained at 1600 °C have diameters of 0.5–3 μm and high aspect ratios of >8. Effects of molar ratio of raw materials, heating temperature and holding time on the phase composition and final morphology were investigated. Growth mechanism of rod-like ZrB₂ grains was also analyzed.