Mg2Si金属间化合物微波固相合成研究

为了解决传统方法制备Mg2Si化合物过程中带来的Mg氧化,挥发等问题,引进微波低温固相反应法,成功合成了Mg2Si粉体.用XRD分析手段对合成的粉体物相进行了表征,并系统研究了合成工艺对粉体制备的影响.结果表明:Mg2Si压坯在微波场中的加热升温曲线与Mg2Si压坯密度有关,密度越大,升温速率降低.本试验条件下,当Mg...     

专利信息

大电流制备铁基复合材料及硬质合金的方法本发明公开的大电流制备铁基复合材料及硬质合金的方法,是先将Fe、Ti、C或Fe、V、C或W、C、Co的粉末按照配比混制均匀,压制成相对密度为65%~78%的压坯,然后将压坯放置于加热设备中,在输出电压为3~10V、输出电流为3 000~20 000 A的电场,升温速度为50~1 200℃/s、真空度为10-4Pa的条件下,对压坯直接通电进行急速加热,使其发生燃烧合成,并在电场的持续作用下,加热至800~1 100℃保温2~5 min完成反应。本发明制备的压坯相对密度高,采用的电流大,电流大小和升温速度等均可以调节,因而可在<800℃下完成…     

SHS法工艺参数对NiZn铁氧体预烧料结构的影响

本文以还原铁粉、NiO、ZnO及Fe2O3为原料，利用自蔓延高温合成（SHS）法制备NiZnFe2O4预烧料，并且利用XRD图谱，Vegard定律等分析了产物结构。分析结果表明：SHS法可以制备纯度很高的NiZnFe2O4预烧料。试验发现，保温时间及粉料压坯密度均对SHS法制备的NiZnFe2O4预烧料的结构有一定的影响：随着保温时问的延长，产物的纯度提高，同时固溶体中的组元配比更接近配方比例；当粉料压坯相对密度为63％左右时，固溶体中的组元配比可达到配方比例。     

微波场中含碳铬矿粉升温特性曲线数值模拟

在微波加热过程中,冶金物料在微波照射下的温度分布是它与微波场相互作用且吸收微波的过程, 此期间伴随的传输过程所导致的升温都归因于微波能耗散转化为热能。分析了微波场影响含碳铬铁矿粉升温特性一系列重要因素,即分析了影响微波场分布的加热谐振腔体的结构和多管耦合方式;结合含碳铬矿粉在微波场中的比热容、介电性质等热及物理性质的变化,通过计算模拟得出微波耗散功率与温度的关系,进而拟合出含碳铬矿粉的升温曲线。这种方法对于不同物料、不同配比、不同体积条件下在类似场结构下的微波冶金物料的升温特性也是有效的     

微波场中FeNb2O6碳热还原反应研究

将微波加热与FeNb2O6碳热还原特性进行结合,探究FeNb2O6在微波场中的还原反应.利用微波热重分析研究了温度、粒度和配碳量等因素对微波碳热还原FeNb2O6反应速率的影响,同时对微波场中FeNb2O6碳热还原反应进行动力学分析.研究结果表明:在微波加热的情况下,FFeNb2O6具有良好的升温特性;相较于常规加热,...     

钛渣在微波加热过程中的升温特性和吸收行为

微波加热钛渣制备人造金红石具有均匀高效、能耗较低等突出优势。在不同条件下,钛渣在微波场中呈现出不同的升温特性,以钛渣为研究对象,系统地分析了微波输出功率、钛渣粒度以及物料量等参数对其微波吸收性能的影响,研究表明,增加微波输出功率有利于增加钛渣在微波场中温度升高的速率;物料量增多会导致钛渣在微波场中温度升高的速率变慢;钛渣粒度减小同样不利于其在微波场中加速升温。     

电介质陶瓷材料辅助微波烧结金属铁粉压坯的试验研究

本文用氧化铝、碳化硅、氧化锆三种不同粒度的介质材料作为辅助材料,采用1 150℃、1 050℃两种烧结温度对铁基压坯材料进行微波烧结,获得不同物理性能、微观特征的铁坯,探讨不同介质材料对微波烧结的作用机理。结果表明,介质陶瓷材料对微波烧结金属铁基压坯有促进作用,其组织致密性、硬度明显高于无介质辅助加热。其辅助加热的作用是通过介质材料在微波加热过程中,由于存在介质损耗,介质分子间互相产生摩擦,引起介质温度升高,使介质材料内部、外部几乎同时加热升温,形成体热源状态,缩短了热传导时间,且物料内外加热均匀一致。介质材料影响由大到小依次是碳化硅、氧化锆和氧化铝,而粒度则影响不大。     

粉末冶金法制备SiCp/Al-Cu-Mg复合材料的固溶时效行为

通过XRD、硬度和电导率测试对比了不同固溶温度下Al-Cu-Mg合金与SiCp/Al-Cu-Mg复合材料中的析出相。XRD分析表明,经T4处理后,未增强基体铝合金中析出相为Al2CuMg相和CuAl2相,而复合材料中的析出相为CuAl2相和Mg2Si相。由SiC颗粒提供的游离Si与基体中的Mg生成了Mg2Si相,从而提高基体合金中Cu/Mg含量比,进而影响Al2CuMg相的生成。     

电场作用下保温过程对Fe-Ti-C体系低温燃烧合成的影响

采用Gheble-1500D热模拟机，在电场作用下，研究保温过程对几种工艺条件下Fe-Ti-C体系压坯低温燃烧合成过程的影响。结果表明：在电场和大热流密度的共同作用下，体系的点火温度得到大幅度降低，且随工艺条件的不同在390～570℃范围内变化；200℃保温2min过程对体系的低温燃烧合成过程有较大的影响，即200℃保温压坯的点火温度和实际所达到的最高温度均高于相应的未保温压坯。合成产物的XRD结果表明：200℃保温压坯的合成产物由TiC和Fe组成，而未保温压坯的合成产物中除了TiC和Fe外，还残留有少量Fe2Ti相。     

均质处理冷速与显微组织对Al-Mg-Si可挤压性和T5性能的影响

通过全方位工业试验,研究了6063铝锭坯在均匀化后不同冷却速度的可挤压性,考察了含不同Mg、Si元素质量分数锭坯的显微组织,除了生成Mg2Si外,过量Si也很重要,在合金成分一定的条件下,Mg2Si相粒子的数目和大小是由均匀化处理后的冷却速度来确定的,这些因素强烈地影响了从铸锭开始到最终产品为止的显微组织变化.试验发现:均匀化处理后快冷,可减小Mg2 Si粒子的尺寸,此情况下,即使快速加热到固溶温度以上的挤压温度,在金属从挤压模孔出来之前,有足够的时间将Mg2Si粒子完全溶解在基体中,所以,均质后快速冷却是使合金可挤压性和T5态性能最好的一个方法[1].     

Si4+掺杂对富锂Li[Li0.15Mn0.575Ni0.275]1-xSixO2材料性能的影响

利用共沉淀合成的锰镍氢氧化物前躯体,采用Si掺杂合成Li[Li0.15Mn0.575Ni0.275]1-xSixO2(0≤x≤4%)正极材料.用X射线衍射和扫描电镜对合成的粉末样品进行了表征,研究了材料的电化学性能.通过掺杂样品的晶胞参数及电化学性能研究发现:少量的Si4+掺杂可有效提高材料的循环性能;随掺杂量的增大,晶格畸变增大,半高宽变大;其中掺量x=1%的材料电化学性能最佳,4.2 V首次放电容量为146.7 mAh/g,经200次循环放电容量仍保持在135.7 mAh/g,容量保持率为92%.     

新型Al-1Mg-0.8Si-xCu铝合金均匀化工艺研究

Al-1Mg-0.8Si-xCu铝合金是汽车轻量化首选材料之一。采用光学显微镜、DTA分析、X射线衍射等分析检测手段,研究了Al-1Mg-0.8Si-xCu这一新型铝合金的均匀化工艺。结果表明,Cu元素含量为0.5%的Al-1Mg-0.8Si-xCu合金理想均匀化工艺为450℃×4 h+550℃×12 h,该工艺适用于Cu元素含量不大于1.05%的合金。     

Luminescence properties of Mn2） ions doped Lu2CaMg2Si3O1） garnet phosphors

Yttrium aluminum garnet structure phosphors Lu2CaMg2Si3O12:Mn2+ were synthesized by conventional high temperature solid-state reaction in reductive atmosphere. The structure and optical properties of samples were characterized by application of powder X-ray diffraction (XRD) and photoluminescence spectroscopy. Results of X-ray diffraction (XRD) analysis showed that the phosphors mainly presented garnet structure with a few weak peaks of impurity phases. Lu2-xCaMg2Si3O12:xMn2+ (x=0.01-0.8) phosphors showed a broad emission band peaking at around 590 nm under ultraviolet (UV) light of 408 nm when Mn2+ concentration was less than 0.08 mol. With an increase in the Mn2+ concentration (above 0.08), another broad emission band peaking at 720 nm besides 590 nm was observed, which may be due to manganese ion having different valence and occupying different host lattice. The critical quenching concentrations of manganese ion in the wavelength of 590 and 720 nm were about 0.06 and 0.2 mol, respectively. With 408 nm excitation wavelength, emission color of the samples had a red shift trend as the Mn2+ concentration increased. All the results indicated that the Lu2CaMg2Si3O12:Mn2+ phosphors could be applicable to n-UV based white LEDs.     

Eco-friendly green synthesis of novel magnetic Fe_3O_4/SiO_2/ZnO-Pr_6O_(11) nanocomposites for photocatalytic degradation of organic pollutant

This study reports the successful so nochemical synthesis of novel Fe_3O_4/SiO_2/ZnO-Pr_6O_(11)(Fe/Si/Zn-Pr_6O_(11)) nanocomposites using fructose as a green capping agent.The influence of various parameters containing capping agent,power and time of ultrasound irradiation was investigated to reach optimum morphology and size conditions.The products obtained were characterized by transmission electron microscopy(TEM),UV/Vis diffuse reflectance spectroscopy(DRS),Fourier transform infrared spectra(FT-IR),vibration sample magnetometer(VSM),scanning electron microscopy(SEM),energy dispersive X-ray microanalysis(EDS) and X-ray diffraction(XRD).The Fe_3O_4/SiO_2/ZnO-Pr_6O_(11) nanocomposites display remarkably enhanced photocatalytic activity towards rhodamine b degradation(89.6%)and Congo red(84.7%) under UV irradiation compared with the other products.The results illustrate that the photocatalytic efficiency of magnetic nanocomposites is very much higher than pure Pr_6O_(11)nanostructures.Magnetic photocatalyst still has good stability after five successive runs.So,these recyclable nanocomposites can play a role in the treatment of both industrial and domestic contaminated water.     

Preparation and luminescence properties of the red-emitting phosphor（Sr1-xCax）2Si5N8：Eu^2＋ with different Sr/Ca ratios

A series of Eu2+-doped ternary nitride phosphors, with a formula of (Sr1-xCax)2Si5N8: Eu2+, were synthesized by high-temperature solid-state method. The structure and luminescence properties were characterized, indicating the potential application as a red phosphor in the phosphor-converted white light-emitting diodes. The X-ray diffraction patterns showed that the Sr2Si5N8 and Ca2Si5N8 phases were generated at each end of (Sr1-xCax)2Si5N8: Eu2+ and coexisted in the range of 0.5≤x≤0.75. The emission spectra showed broad emission bands originating from the 4f65d1→4f7 transition of Eu2+ ions. The emission peak changed with the variations in Ca2+ concentration.     

Effects of ceria/zirconia ratio on properties of mixed CeO_2-ZrO_2-Al_2O_3 compound

A series of CexZr0.50-xAl0.50O1.75(0.05≤x≤0.45) mixed oxides with different Ce/Zr ratio were prepared by co-precipitation method and characterized by means of X-ray diffraction(XRD),Brunauer-Emmet Teller method(BET),temperature-programmed reduction(H2-TPR) and oxygen pulsing technique.The XRD results showed that all samples kept the single CeO2 cubic fluorite structure after calcination at 600 and 1000 oC for 5 h.The results of BET revealed that CexZr0.50-xAl0.50O1.75 with Ce/Zr molar ratio 1/1 exhibited higher specific surface area(212 m2/g) and larger pore volume(0.40 ml/g).For all aged samples,CZA with Ce/Zr molar ratio 3/7 presented the highest specific surface area(104 m2/g) and pore volume(0.34 ml/g).The compounds could still keep prominent structural and textural stability with excellent redox properties even calcined at 1000 oC.     

Synthesis and Electrical Properties of La0.8Sr0.2-xCaxCo0.9Fe0.1O3-δ

Ａｎｉｍｐｏｒｔａｎｔｇｏａｌｉｎｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｓｏｌｉｄｏｘ ｉｄｅｆｕｅｌｃｅｌｌｓ (ＳＯＦＣｓ)ｉｓｔｏｒｅｄｕｃｅｔｈｅｏｐｅｒａｔｉｎｇｔｅｍ ｐｅｒａｔｕｒｅｏｆｔｈｅｆｕｅｌｃｅｌｌｓｔａｃｋｆｒｏｍ 10 0 0℃ｔｏｂｅｌｏｗ85 0℃ｓｏａｓｔｏｇｅｔａｎｏｐｔｉｍｕｍｔｒａｄｅ ｏｆｆｂｅｔｗｅｅｎｐｅｒ ｆｏｒｍａｎｃｅａｎｄｌｉｆｅｔｉｍｅｏｆｔｈｅｓｔａｃｋａｎｄｔｏｒｅｄｕｃｅｔｈｅｏｖｅｒａｌｌｓｙｓｔｅｍｃｏｓｔ[1] .Ｔｏａｃｈｉｅｖｅｔｈｉｓｄｅｓｔｉｎａｔ…     

Microstructure and phase constituents in the interface zone of Mg/Al diffusion bonding

The microstructure and phase constituent for the Mg/Al diffusion-bonded joint were studied via scanning electron microscope (SEM), microhardness test, electron probe microanalyzer (EPMA), and X-ray diffraction (XRD). The test results indicated that the new compact phase was formed near the transition region of the Mg/Al diffusion interface. There are three new phase layers in the transition region. The microhardness of the diffusion zone is higher than that of the Mg and Al substrate. The fracture morphology mainly consists of a coarse and gray fracture, and the fracture is mainly the mixed fracture of cleavage and intergranular. X-ray diffraction tests indicate that the diffusion zone of the Mg/Al diffusion-bonded joint consists of intermetallic compounds MgAl, Mg₃Al₂, and Mg₂Al₃. With the increase of temperature, the content of Mg₃Al₂ and Mg₂Al₃ phases with good stability was increased.     

Blue-green BaAl_2O_4：Eu~（2＋）,Dy~（3＋） phosphors synthesized via combustion synthesis method assisted by microwave irradiation

Blue-green luminescent BaAl2O4:Eu2+,Dy3+ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The XRD results revealed that when the concentration of urea was over 3 times higher than theoretical quantities, a BaAl2O4 single hexagonal phase was obtained. The SEM results revealed that the surface of the BaAl2O4:Eu2+,Dy3+ pow...     

FeSiAlCr合金/W型六角晶系Ba铁氧体复合粉体的制备及微波特性

以雾化Fe85Si2Al6Cr7粉和溶胶凝胶法制备的W型六角晶系Ba1Co0.9Zn1.1Fe16O27铁氧体粉末为原料,通过高能球磨复合改性得到FeSiAlCr合金/W型六角晶系Ba铁氧体复合粉体。采用X射线衍射仪(XRD)和扫描电镜(SEM)对该粉体的微结构和形貌进行分析和观察,利用微波矢量网络分析仪系统测定粉体试样在2~18 GHz频段内的复介电常数和复磁导率以及吸波涂层试样板的吸波性能,研究该复合粉体的微波电磁特性和电磁损耗性能。结果表明,FeSiAlCr合金/W型六角晶系Ba铁氧体复合粉体颗粒保持W型铁氧体的六角片状晶粒形貌和微结构;其ε′、ε″、μ′和μ″均高于W型铁氧体而低于Fe合金的对应值;FeSiAlCr合金含量与复合材料的磁损耗和介电损耗的相对强弱密切相关,Fe合金含量适中的复合材料,其吸波涂层厚度为2 mm时,在2~18 GHz全频段的吸波性能高于20 dB,峰值点达50 dB。