转炉烟尘制备氮化铁磁性材料及其性能的研究

在NH3/H2气氛下对转炉烟尘进行了还原与氮化的连续处理,以穆斯堡尔谱学结合X光衍射方法对处理试样进行物相分析.实验结果表明,氮化温度为560℃,NH3/H2比小于11时,γ-Fe4N的含量超过70%,处理试样的比饱和磁化强度σs高达140emu/g,较原始样品的有明显增加.     

形成条件对氮化铁（γ′-Fe4N）微观结构及磁性的影响

提纯后的转炉烟尘通过还原、氮化处理生成氮化铁磁粉（γ′-Fe4N），用穆斯堡尔谱和X射线衍射（XRD）对γ′-Fe4N磁粉的微观结构进行了研究，并用振动样品磁强计（vSM）测量了样品的磁性，讨论了形成条件对γ′-Fe4N结构与磁性的影响。     

新型磁记录材料——氮化铁磁粉制备的研究

为了获得具有优异磁有的氮化铁磁粉,本研究采用铁粉氮化制备γ’－Ｆe4N,优越氮化温度及氮化气氛,提高γ’Ｆe4N与α－Fe的混合粉末高能球磨后,在２４０℃真空退火４h,形成含５％左右α６”－Fe16N2相的复合氮化铁磁粉。     

水热法制备CoFe2O4纳米颗粒及其穆斯堡尔谱与磁性能研究

用水热法在不同温度下制备结晶性较好、颗粒均一的CoFe2O4纳米颗粒,无需进一步煅烧。利用X射线衍射仪(XRD)、场发射扫描电镜(SEM)、穆斯堡尔谱仪和综合物性测量系统(PPMS)对不同温度下合成的样品进行表征。结果表明,随着合成温度的升高,CoFe2O4纳米颗粒的结晶性增强,粒径逐渐增大,样品的饱和磁化强度逐渐增强。当合成温度为500℃时,CoFe2O4纳米颗粒的饱和磁化强度达到64.1A.m2/kg,与块体的CoFe2O4(72A.m2/kg)接近。穆斯堡尔谱分析表明,当晶粒粒径超过了超顺磁性的临界尺寸,样品的超顺磁性消失,随着合成温度的升高,B位上Fe3+离子的比例增高,磁性能增强。     

Ni-Fe普鲁士蓝的离子交换选择性研究

研究了Ni—Fe普鲁士蓝对不同价态金属离子的交换选择性。在Ni—Fe普鲁士蓝与一价Cs^＋溶液反应中,Ni—Fe普鲁士蓝主要由K^＋与Cs^＋进行离子交换;而在与二价和三价的离子溶液反应中,离子交换主要是通过目标离子（Cr^3＋、Sr^2＋、Cu^2＋）与K^＋和Ni^2＋发生交换。结合全谱等离子直接光谱（ICP）和穆...     

碳热还原氮化法制备碳氮化钒的研究

以工业级五氧化二钒(V2O5)和纳米碳黑为原料,在氮气气氛下利用碳热还原法合成了碳氮化钒(V(C1-xNx))粉末。通过XRD、SEM测试方法对不同配碳量、不同反应温度下的反应产物进行了表征,结果表明:按配碳量为24.8%的化学计量配比的原料在1200～1250℃的温度范围内反应后可获得物相单一、含氮量相对较高、平均粒径大约为500nm的V(C1-xNx)固溶体粉末;低于1150℃的温度下合成的粉末中含有未反应完全的氧化物存在;高于1250℃的温度下反应开始向碳化方向转变,导致x值降低,且粉体颗粒间存在桥联和熔融现象。     

碳弧法制备碳包铁纳米颗粒的研究

用直汉碳弧法制备碳包铁纳米颗粒,应用透射电镜（ＴＥＭ）、Ｘ射线衍射分析（ＸＲＤ）和穆斯堡尔谱学进行研究,结果表明,当阳极复合棒中为纯铁粉加石墨粉时,出现３种碳包铁纳米颗粒：α－Ｆｅ,渗碳体（Ｆｅ３Ｃ）和奥氏体;当阳极复合棒中为Ｆｅ２Ｏ３加石墨粉时,出现４种碳包铁纳米颗粒：α－Ｆｅ,渗碳体,奥氏体和ＦｅＯ。它们的尺寸大小在５～５０ｎｍ范围。     

Fe3O4/聚苯胺纳米复合材料高能球磨法制备及其性能研究

以Fe3O4粉体及导电聚苯胺为原料,用高能球磨法制备Fe3O4／聚苯胺纳米复合材料,用Moessbauer谱、XRD、FTIR、VSM等方法对样品进行表征。结果表明随着球磨时间的增加,Fe3O4的粒径迅速减小到纳米量级;Fe3O4表面与聚苯胺作用生成了某种顺磁性物质;同时有少量的α—Fe3O4生成;复合物中Fe3O4颗粒A、B晶位中Fe的含量发生了明显的变化。复合物的电磁性能也明显发生了改变。     

钠钨青铜NaxWO3(x～0.88)纳米晶的机械化学法制备研究

利用机械化学法合成了平均粒径为17nm的钠钨青铜NaxWO3(x～0．88)纳米晶材料。高纯Na片和WO3粉末经过行星式球磨机1h高能球磨．有固相反应Na WO3→NaxWO3 Na2WO4发生。反应经过44h基本完成。利用去离子水洗涤后可得到纯净的钠钨青铜粉末。”。^182W穆斯堡尔谱在77K温度下为一单线峰．显示样品为立方晶体结构。电性质测量表明样品的电阻率随着温度降低而升高,呈半导体特征．并可用三维可变程跃迁模型来描述。     

聚合物/Fe3O4混合体系高能球磨过程的穆斯堡尔谱研究

运用高能球磨法研磨聚合物／Fe3O4混合体系，对样品的穆斯堡尔谱与XRD的测定表明有纳米级α-Fe2O3颗粒生成；通过改变聚合物种类、比例以及球磨气氛从不同角度考察聚合物对Fe2O4球磨的影响。     

等离子体法制备超细粉体氮化铝的研究

以微米级铝粉为原料 ,用N2 热等离子体法制备了超细氮化铝粉体。在等离子体功率12kW ,运行N2 流量 2m3/h ,急冷NH3流量 0 6m3/h ,送粉N2 流量 0 8m3/h条件下 ,铝粉全部转化为纳米氮化铝。采用SEM技术和粒度分析仪对产品进行了分析 ,制得的氮化铝粉末平均粒径为10 0nm ,粒度分布为 4 0～ 14 0nm     

The influence of iron on the preparation of silicon nitride from silica

The thermodynamics of carbothermal reduction and nitriding of silica in the temperature range 1200 to 1600° C have been evaluated and may be used to determine the conditions required to form silicon nitride, silicon oxynitride or silicon carbide. The products of reaction are, however, frequently dictated by kinetic rather than thermodynamic considerations and the presence of impurities in the silica and carbon reactants is especially important. α-silicon nitride has been prepared from high purity silica and carbon but under identical conditions of temperature and nitrogen pressure the chemistry of the process changes markedly when a small amount of iron is added to the reactants. Below 1320° C iron has no effect and pure α-silicon nitride is formed but with increasing temperature the proportion of silicon carbide in the product increases. Above 1550° C silicon carbide is the stable solid phase in the Si-C-O-N system at 1 atm pressure. The process chemistry has been investigated by high-temperature reaction studies and X-ray diffraction and reaction mechanisms are proposed on the basis of microstructural observations of reactants and products.     

Rotary powder bed chemical vapour deposition of titanium nitride on spherical iron powder

Titanium nitride (TiN) was coated on to spherical iron powder by the rotary powder bed chemical vapour deposition technique using a reactant gas of the TiCl₄-N₂-H₂ system. The dispersibility of the coated powder was significantly improved by the adsorption of the reactant gas on to the rotating particles during raising the temperature. Polycrystalline TiN film, having a columnar structure of a few micrometres was coated on to the iron powder, typically at a deposition temperature of 1000° C and at a treatment time of 80 min. The TiN-coated iron powder showed an oxidation resistance up to about 650° C.     

Acidic leaching both of zinc and iron from basic oxygen furnace sludge

During the steel production in the basic oxygen furnace (BOF), approximately 7-15 kg of dust per tonne of produced steel is generated. This dust contains approximately 1.4-3.2% Zn and 54-70% Fe. Regarding the zinc content, the BOF dust is considered to be highly problematic, and therefore new technological processes for recycling dusts and sludge from metallurgical production are still searched for. In this study the hydrometallurgical processing of BOF sludge in the sulphuric acid solutions under atmospheric pressure and temperatures up to 100 °C is investigated on laboratory scale. The influence of sulphuric acid concentration, temperature, time and liquid to solid ratio (L:S) on the leaching process was studied. The main aim of this study was to determine optimal conditions when the maximum amount of zinc passes into the solution whilst iron remains in a solid residue.     

Magnetic particles derived from iron nitride

Due to its high saturation magnetization (σ_s(0K)≈208 emu/g) and to the ease of obtaining it as a particulate material, Fe₄N could be a suitable magnetic material for replacing highly reactive metallic iron pigments (σ _s(0K)≈218 emu/g) in high-density recording. Throughout a nitriding process of properly selected precursors Fe₄N can be obtained in either of two morphologies: acicular or isotropic. Further protection of the magnetic particles can be ensured through coating of the precursor particles prior to thermal decomposition in NH₃/H₂ atmosphere or through substitutions with selected elements. The obtained passivated nitrides are characterized by high magnetic properties (H_c≈600 Oe; σ_s≈150 emu/g) and chemical stability well adapted for use as magnetic pigments for high-density recording     

Synthesis of cubic boron nitride with boron nitride powder formed from triammoniadecaborane

Cubic BN was synthesized under high temperature and pressure conditions from BN powder formed by reaction of triammoniadecaborane (TAD) with ammonia. The BN powder formed from TAD and ammonia had a low degree of ordering. The crystal lattice of the BN powder increased in regularity with increasing synthesis temperature and time for the reaction of TAD with ammonia. The conversion yield of cubic BN at 1300 °C and 6.5 GPa in the presence of AIN increased with decreasing of reaction temperature of TAD and ammonia from 1000–700 °C. Cubic BN decreased in yield with increasing reaction time of TAD and ammonia at 800 °C. BN powder pre-heat treated at 1550 °C had a crystallite size,L _c, of 22 nm, and was converted to cubic BN in a 43% yield at 1300 °C and 6.5 GPa for 10 min. The activation energy for cubic BN synthesis from BN powder-20 mol% AIN was 97 kJ mol^–1, when the starting BN was synthesized at 800 °C. The conversion yield of cubic BN from the disordered BN-20 mol% AIN was 100% after heat treatment at 1300 °C and 6.5 GPa for 20 min.