碳热还原氮化法制备碳氮化钛粉末

以物质的量比为1∶2.5的TiO_2粉和活性炭粉为原料,于N2气氛下采用碳热还原氮化法在不同的合成温度(分别为1500℃、1600℃、1650℃、1700℃、1750℃,N2压力固定为0.1MPa)和N2压力(分别为0.05MPa、0.1MPa、0.15MPa、0.2MPa,温度1700℃)下保温3h合成了碳氮化钛粉末。研究结果表明提高合成温度和降低N2压力有利于合成碳含量高的碳氮化钛粉末;在N2压力为0.1MPa的条件下,于1700℃保温3h热处理后,可以获得平均粒径为2μm的碳氮化钛粉末。     

TiO2碳还原氮化法制备TiN粉末

本文报道了用TiO_2碳还原氮化法制备TiN粉末的实验结果,当用N_2为氮化剂时影响皮应的主要因素为温度和时间,而用分解氨为氮化剂时分解氨的流量也成为重要的影响因素。采用XRD法探讨了反应过程的机制,初步确定了还原过程的中间产物为Tj_3O5。     

TiO2碳还原氮化法制备TiN的实验规律

本文报道了采用TiO_2-C-N_2(或NH_3)系制备TiN粉末的实验规律,指出了分别采用N_2和分解氨(N_2 3H_2)为氮化剂时影响合成反应进行的因素,并初步摸索出了合成单相TiN粉末的条件。     

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。     

碳热还原氮化粉煤灰的研究

以粉煤灰加入炭黑为主要原料,在氮气气氛下对粉煤灰进行了碳热还原氮化研究.研究了碳加入量、合成反应温度、保温时间和Fe2O3含量等因素对生成物物相的影响.实验结果表明:选用理论加入碳含量的样品,在反应温度为1350℃、保温9h条件下,产物中含有较多β-Sialon相;而且经磁选除铁后的粉煤灰较未除铁粉煤灰在反应温度为1400℃、保温9h条件下,碳化还原氮化产物中15R相含量明显增多.     

TiO2 在煤矸石碳热还原氮化过程中的作用

以煤矸石、炭黑为原料,分别加入0、2%、4%、6%、8%、10%、15%和20%的TiO2,组成的不同试样在流动氮气中进行热处理,热处理温度分别是1350 ℃、1400 ℃、1450 ℃、1500 ℃、1550 ℃,保温时间为6 h,测定热处理后试样的质量损失率,借助XRD、SEM和EDS等手段,分析热处理后试样的物相组成、显微结构和微区成分,研究引入TiO2对煤矸石还原氮化的作用.结果表明TiO2的加入有利于煤矸石还原氮化转变成β-SiAlON,并能促进β-SiAlON晶粒的生长发育.这也许是因为TiO2的加入有利于莫来石及SiO2分别还原氮化为X相及Si2N2O,Si2N2O与Al2O3固溶形成O'-SiAlON;最后X相和O'-SiAlON转变成β-SiAlON;多余的TiO2可以被还原氮化为耐火度高、耐磨性好的TiN.TiO2的最佳加入量为4%.     

碳热还原氮化法合成氮化钒/氮化铬复合粉末

以纳米V_2O_5、纳米Cr_2O_3和纳米碳黑为原料,经过干燥、球磨混料后,在流动氮气中焙烧,得到了氮化钒/氮化铬(VN/CrN)复合粉末。利用XRD、TG-DSC、SEM、BET和TEM对合成产物进行了表征和测试,考察了反应温度和保温时间对VN/CrN复合粉末的微观结构和性能的影响。结果表明:在1 200℃、保温2 h条件下,可制备出平均晶粒直径为40 nm的VN/CrN复合粉末。该复合粉末主要由VN、CrN和VCrN_2组成,这3种物质均为面心立方结构,空间群均属于Fm3m。复合粉末的比表面积为21.09 m~2/g。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,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115.6 MPa和207.2%。     

天然原料碳热还原氮化合成β''''-SiAlON的研究进展

本文介绍β'-SiAlON的结构、基本性能及应用领域,阐述了合成β'-SiAlON的原材料和各种合成方法,重点介绍了利用天然原料合成β'-SiAlON的还原剂外加法和还原剂内加法即有机插层法.详细阐述了各工艺条件(反应原料的组成、反应温度、反应时间、反应气氛、流速及反应物颗粒尺寸、添加剂等)对合成β'-SiAlON反应结果的影响.同时本文指出目前该研究可能存在的问题及解决的途径.     

球磨对碳热还原氮化法制备氮化铝粉末的作用

研究了高能球磨对氧化铝碳热还原反应制备氮化铝的作用。结果表明：氧化铝及没料经高能球磨后,碳热还原反应开始温度降低,完全反应的温度降至1250℃。与未经球磨的反应相比,反应进行程度提高。球磨产生的机械化学作用,如细化晶粒、晶格畸变和大量缺陷及表面断健作用是球磨促进碳热还原反应的主要原因。     

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。     

Low temperature synthesis of Titanium diboride by carbothermal method

Titanium diboride powders have been synthesized by means of carbothermal reduction method utilizing Titanium oxide, Boric acid and Graphite. The effect of mechanical activation of mixed raw materials and the use of additional Boric acid on the final phases have been studied. The resultant powders were characterized by X-ray diffraction (XRD) analyzer and Field Emission Scanning Electron Microscope (FESEM). XRD patterns showed that TiB₂, TiC and C phases after heat treatment at stoichiometric ratio of reactants. By increasing the milling time, the unwanted phases such as C and TiC will be reduced. Pure TiB₂ could be synthesized with mechanical activation of raw materials for 24?h at non-stoichiometric ratio (using additional Boric acid) and heat treatment at low temperature of 1380?°C. In this condition, Titanium diboride could be achieved with residual carbon of 0.92 0.09wt% and mean average particle size of 3.28µm. Thermal analysis (TGA-DTA) was used to determine the reaction progress and mechanism. Results revealed that the intermediate phase, TiBO₃, played an important role in getting to lower temperature synthesis. This phase was identified after mechanical milling of raw materials and heat treatment at temperature of 1250?°C.     

铝源孔容和焙烧升温过程对碳热还原法制备氮化铝粉体的影响

碳热还原氮化法是大规模制备高纯度氮化铝（AlN）粉体的主要方法,通过微反应器制备不同孔容的铝源,系统探究了前体孔容和微观形貌对AlN粉体产物的影响,并通过动力学模拟验证了筛选出的前体的活性。同时对氮化反应升温过程的影响也做了探究,最终通过对前体和焙烧升温过程的优化,得到纯度99%以上的AlN粉体,其平均粒径约为150 nm,O元素含量为0.55%。     

Phase,microstructure and sintering of aluminum nitride powder by the carbothermal reduction-nitridation process with Y2O3 addition

Aluminum nitride powders were synthesized by carbothermal reduction-nitridation method using Al(OH)₃, carbon black and Y₂O₃ as raw materials. The change of phase, microstructure and densification during the AlN synthesis and sintering process were investigated and the effects of Y₂O₃ was discussed. The results showed that Y₂O₃ reacted with Al₂O₃ to form yttrium aluminates of YAlO₃ (orthorhombic and hexagonal phases), Y₄Al₂O₉ and Y₃Al₅O₁₂ at the low temperature of 1350 °C. YAlO₃ could firstly be transformed into Y₂O₃ and then completely into YN when the firing temperature and holding time increased. However, YN could be oxidized into Y₂O₃ again after the carbon removal at 700 °C in the air atmosphere. There were two ways generating AlN when adding Y₂O₃ and the possible mechanism was proposed. Y₂O₃ from YN oxidation favored the densification of AlN ceramics because the liquid had better flowability and distribution in the sintering process at 1800 °C.     

碳热还原法合成TiB_2的热力学分析与研究

以30μm TiO2(w(TiO2)>99.8%,金红石型)、50 μm B2O3(w(B2O3)>99.5%)及10μm石墨粉(w(C)>99%)为原料,按n(TiO2):n(B2O3):n(C)=1:1:5进行配料后放入不锈钢球磨罐中抽真空球磨24 h,然后将反应混合物移入石墨坩埚内置于热压炉中,分别在1 250、1 350、1 400、1 500、1 600、1 700℃保温4 h进行反应.对以TiO2、B2O3、石墨粉为原料合成TiB2的反应体系进行了热力学计算,并对反应产物进行XRD与SEM分析.热力学计算表明,上述3种原料通过碳热还原反应合成硼化钛的反应开始温度为1 556 K.而合成产物的XRD分析表明,生成硼化钛的开始温度为1 350℃以上.碳热还原TiO2和B2O3合成TiB2的反应机理应为C还原TiO2,其中间产物为Ti3O5、Ti2O3、TiO,然后这些中间产物与B2O3一起逐渐被C还原生成TiB2.SEM分析表明,TiB2颗粒呈不规则短柱状,粒度为5～10m;当反应温度达到1 700℃以上时,硼化钛晶粒有长大的现象.     

碳热还原氮化锆英石合成ZrN-Si3N4复合材料

以锆英石(粒度≤44μm)和炭黑(粒度≤30μm)为原料,按m(锆英石):m(炭黑)=100:40的比例配料,于球磨罐中以无水乙醇为介质湿混24 h,然后将料浆放入干燥箱中于60℃下充分干燥,再将干燥后的粉料置于球磨罐中干混10 h。最后,将混匀的物料以60 MPa的压力压制成尺寸为20 mm×5 mm的柱状试样,在120℃下充分干燥后置于N2流量为1.0 L.m in-1的气氛炉内,分别在1 400、1 450、1 480和1 500℃的温度下煅烧,保温时间分别为6、9和12 h。自然冷却至室温后,采用XRD分析试样的相组成,采用SEM观察试样的显微结构,并对碳热还原氮化反应过程进行热力学分析。结果表明:以锆英石和炭黑为原料,利用碳热还原氮化反应,在N2气氛下可以合成出ZrN-Si3N4复合材料;通过控制煅烧温度或炉内CO气体分压,可以获得不同组成的复合材料。在本试验条件下,合成ZrN-Si3N4复合材料的适宜工艺参数为1 500℃保温12 h。     

Carbothermal reduction synthesis of TiB2 ultrafine powders

Submicrometric TiB₂ powders were synthesized by carbothermal reduction process using titanium dioxide, boron carbide and carbon black as the starting materials. The influence of different amount of boron carbide (22.0–26.8 wt%), calcination temperature (1400–1900 °C) and holding time (15–90 min) on the composition and microstructure of the product was investigated. The resultant powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results showed that hexagonal impurity-free TiB₂ crystalline powders with the grain size below 1.0 μm could be successfully prepared at 1600 °C for 30 min in Ar atmosphere when the amount of boron carbide was 25.3 wt%. The increase in temperature contributed to reaction completion and grain growth, but the abnormal grain growth and oversintering took place above 1800 °C.     

Highly transparent AlON ceramics sintered from powder synthesized by carbothermal reduction nitridation

Aluminum oxynitride (AlON) powders were synthesized by the carbothermal reduction and nitridation process using commercial γ-Al₂O₃ and carbon black powders as starting materials. And AlON transparent ceramics were fabricated by pressureless sintering under nitrogen atmosphere. The effects of ball milling time on morphology and particle size distribution of the AlON powders, as well as the microstructure and optical property of AlON transparent ceramics were investigated. It is found that single-phase AlON powder was obtained by calcining the γ-Al₂O₃/C mixture at 1550 °C for 1 h and a following heat treatment at 1750 °C for 2 h. The AlON powder ball milled for 24 h showed smaller particles and narrower particle size distribution compared with the 12 h one, which was benefit for the improvement of optical property of AlON transparent ceramics. With the sintering aids of 0.25 wt% MgO and 0.04 wt% Y₂O₃, highly transparent AlON ceramics with in-line transmittance above 80% from visible to infrared range were obtained through pressureless sintering at 1850 °C for 6 h.