Al2O3 含量对 YSZ 热障涂层性能的影响

Al_2O_3等氧化物对YSZ热障涂层的高温使用性能有一定的影响。本文用HVOF喷涂Ni Co Cr Al Y合金粘结层,APS喷涂YSZ陶瓷面层,制备了Al_2O_3含量为0.01~0.64wt%的YSZ涂层。比较了不同Al_2O_3含量的YSZ涂层在1100℃下的热震性能和抗烧结性能,并探讨Al_2O_3对涂层的影响机理。结果表明相较于高纯YSZ涂层,随着涂层中Al_2O_3含量升高,涂层的抗热震性能降低,且Al_2O_3促进YSZ涂层的烧结。Al_2O_3含量在小于0.01wt%-0.12wt%区间内时,对涂层抗热震和抗烧结性能有显著影响,含量继续增加至0.64%时,对性能影响减缓。显微组织观察与EDS检测结果表明涂层中Al_2O_3并未在熔融颗粒界面处偏聚,但在颗粒内部有局部偏析。由此推测,含Al_2O_3的YSZ涂层热震失效的原因可能是Al_2O_3在YSZ颗粒内部偏析,并影响涂层的烧结性能,导致裂纹容易萌生和扩展。     

工艺参数对高速火焰喷涂 NiCr-Cr3C2 涂层性能的影响

基于正交回归实验设计工艺参数的方法,本实验研究了喷涂距离、氧气流量和送粉量对高速火焰喷涂NiCr-Cr_3C_2涂层性能的影响,获得了喷涂工艺参数与涂层孔隙率、硬度、结合强度的关系。结果表明:喷涂距离、氧气流量和送粉量对涂层性能具有交互的影响,优化的喷涂距离、氧气流量和送粉量有利于获得性能较好的涂层。     

高能球磨制备NiCr-Cr_2O_3-BaF_2/CaF_2复合粉末及其爆炸喷涂层的性能

为了制备高性能复合涂层,以70%NiCr、20%Cr2O3及10%BaF2/CaF2为原料,采用高能球磨方法制备了复合粉体,并通过特定的爆炸喷涂工艺制得复合涂层。利用扫描电子显微镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)等对球磨后粉体和喷涂层的微观形貌、组织结构、成分及物相组成进行了分析。根据HB5143-96测定了爆炸喷涂复合涂层与基体间的结合强度。结果表明:随球磨时间的延长,粉体球形化程度逐步加大,颗粒尺寸逐步减小,粒度分布趋于集中,颗粒成分及结构均匀性逐步提高;当球磨11h后,粉体中的BaF2和CaF2固溶于NiCr合金,Cr2O3颗粒在NiCr基体内部镶嵌;通过爆炸喷涂将球磨粉喷涂在不锈钢基体上,其涂层微观组织均匀致密,显微硬度Hv为578,涂层与基体结合强度为67MPa,综合性能优于混合粉喷涂层。     

HVAF 制备 WC 基涂层结构与滑动摩擦磨损性能研究

采用HVAF超音速火焰喷涂制备三种WC基金属陶瓷复合涂层以及金属涂层Ni60,对比分析了各涂层的微观形貌、硬度、沉积速率、滑动摩擦磨损性能。结果表明:HVAF超音速火焰喷涂制备的各涂层与基体结合良好、涂层结构致密,孔隙率1.5%;随着复合涂层中碳化物陶瓷增强颗粒的增加,各涂层的显微硬度增大,沉积速率降低;摩擦磨损试验显示WC-10Co-4Cr、WC-12Co涂层磨损量仅为金属涂层Ni60的1/20,表现出优异的耐滑动磨损性能。     

超音速喷涂Cr3C2-25NiCr复合涂层的组织及电化学特性研究

采用超音速火焰喷涂(HVOF)设备在Q235钢表面制备了Cr3C2-25NiCr金属陶瓷涂层,对涂层的显微形貌、组织成分和机械性能进行了研究,结果表明:HVOF制备出的金属陶瓷涂层主要由NiCr、Cr3C2和Cr7C3相组成,涂层致密、硬度高,与基材的结合强度好。实验还测试了涂层和基材在0.5%H2SO4溶液中的腐蚀、电化学行为,阳极极化曲线测试结果显示出涂层在0.5%H2SO4溶液中具有很好的耐蚀性,通过SEM及所配能谱对基材和涂层腐蚀产物形貌和成分进行分析,发现涂层腐蚀主要发生粘结相NiCr合金处,而Ni、Cr氧化物阻止了腐蚀进一步发生,96h浸泡实验也证实了致密的金属陶瓷涂层对基材有很好的抗腐蚀保护作用。     

超音速火焰喷涂WC-12Co涂层抗磨粒磨损性能研究

采用超音速火焰（HVOF）喷涂工艺在316L不锈钢基体上制备了WC-12Co涂层,测试了涂层的结合强度、显微硬度、气孔率以及抗磨粒磨损性能。并利用XRD对喷涂粉末及涂层进行了相结构分析,用扫描电子显微镜对喷涂粉末、磨粒磨损前后的涂层表面形貌进行了观察。结果表明：在喷涂过程中,仅有很少量的WC粒子发生氧化脱碳。涂层的结合强度和显微硬度高,组织结构致密。在相同的实验条件下,316L的磨粒磨损量是WC-12Co涂层的95倍,这表明HVOF制备的WC-12Co涂层具有优异的抗磨粒磨损性能。     

HVAF喷涂La2O3改性WC-20Cr3C2-11NiMo涂层的耐磨耐蚀性能

为进一步提升高质量WC涂层的耐磨性、耐海水腐蚀性和耐海水气蚀性。采用大气超音速火焰喷涂(HVAF)在0Cr13Ni5Mo基体上制备稀土La₂O₃改性WC-20Cr₃C₂-11NiMo涂层。通过显微硬度测试、平面孔隙测试、摩擦磨损实验、电化学实验和模拟海水超声波气蚀实验,测试涂层的显微硬度、孔隙率、摩擦因数、摩擦磨损性能、耐海水腐蚀性能和耐海水气蚀性能,分析La₂O₃对WC-20Cr₃C₂-11NiMo涂层耐磨耐蚀性能的影响。结果表明,改性后的涂层显微硬度提升到1400 HV0.2左右,平均孔隙率降低约48.6%;涂层磨损质量降低约33%,摩擦因数降低约30%,摩擦磨损表面微凹坑和微裂纹明显减少;电化学自腐蚀电位明显右移,电化学自腐蚀电流密度明显减小;涂层的气蚀质量损失减少约20%,气蚀坑洞明显减少和变小。HVAF喷涂La₂O₃改性后的WC-20Cr₃C₂-11NiMo涂层硬度略微提升,致密性、耐磨性、耐海水腐蚀性和耐海水气蚀性得到明显提升,除表面疲劳磨损外,表面摩擦磨损机理从严重磨粒磨损转变为轻微磨粒磨损,气蚀机理主要为流体冲击波侵蚀。     

超音速火焰喷涂WC-12Co涂层抗磨粒磨损性能研究

采用超音速火焰(HVOF)喷涂工艺在316L不锈钢基体上制备了WC-12Co涂层,测试了涂层的结合强度、显微硬度、气孔率以及抗磨粒磨损性能。并利用XRD对喷涂粉末及涂层进行了相结构分析,用扫描电子显微镜对喷涂粉末、磨粒磨损前后的涂层表面形貌进行了观察。结果表明:在喷涂过程中,仅有很少量的WC粒子发生氧化脱碳。涂层的结合强度和显微硬度高,组织结构致密。在相同的实验条件下,316L的磨粒磨损量是WC-12Co涂层的95倍,这表明HVOF制备的WC-12Co涂层具有优异的抗磨粒磨损性能。     

HVAF喷涂不同碳化物含量的NiCr-Cr_3C_2涂层研究

本文利用HVAF技术在CrZrCu基体上喷涂制备了NiCr-30%Cr_3C_2涂层和NiCr-50%Cr_3C_2涂层。采用X射线衍射仪和扫描电镜表征涂层物相组成和截面形貌;使用拉伸试验机、维氏硬度计、销盘磨损试验机测量了涂层的结合强度、硬度和摩擦磨损性能。结果显示:含有50%Cr_3C_2的涂层具有更高的硬度和耐磨性,但是由于碳化物含量较多使得涂层内部孔隙率增加,同时结合强度变差。而30%Cr_3C_2涂层具有较低的孔隙率和较高的结合强度。两种喷涂层均以机械结合为主,磨损机制主要为黏着磨损和轻微的氧化磨损。     

张力辊表面处理工艺的应用分析

为提高张力辊辊面性能,分别采用在辊面电镀硬铬、HVOF喷涂WC-12Co、HVAF喷涂WC-12Co三种工艺对张力辊辊面进行强化处理,并对随辊试样进行分析。发现镀铬层内部存在一定的微裂纹,硬度达到900HV_0.3;HVOF制备的涂层孔隙率为2.3%,涂层硬度1 100HV_0.3;HVAF制备的涂层孔隙率为0.6%,涂层硬度1 400HV_0.3;三种工艺制备的最终辊面粗糙度Ra均能满足上机使用要求,镀铬辊使用6个月后,辊面粗糙度下降严重,而WC涂层辊面的粗糙度保持相对稳定。     

Investigation on pumping oxygen characteristics of （Bi2O3）0.73（Y2O3）0.27 solid electrolyte

（Bi2O3）0.73（Y2O3）0.27 fine powders prepared by wet chemical precipitation method were cold isostatically pressed to form solid electrolyte tubes, and sintered at 900 ℃ for 10 h in the air. Their pumping oxygen characteristics in non-dehydrated Ar gas were investigated, where a ZrO2 （Y2O3 stabilized） oxygen sensor was used to measure the oxygen partial pressure Po2. The results showed that the Po2 value reached magnitudes of 1×10^-2-1×10^-10 Pa at the applied pumping oxygen voltage of 0.5 V, 1×10^-37-1×10^-27 Pa at 1.0 V and 1×10^-53-1×10^47 Pa at 2.0 V within the temperature range from 550 to 650 ℃. Moreover, no cracks were found in the tested solid electrolyte tubes. Thus, the Bi2O3-Y2O3 system might be used in solid electrolyte oxygen pump for purifying gases.     

重型燃气轮机用La_2(Zr_(0.7)Ce_(0.3))_2O_7/YSZ双层热障涂层热循环性能研究

重型发电燃气轮机低排放、高效率的发展目标,要求燃气轮机透平的进气温度不断提高。热障涂层作为保护金属热端部件的重要手段,是实现这一目标的关键技术之一。目前世界上最先进的J级燃气轮机的透平进口温度已经达到1600℃,热端部件表面温度超过1250℃,传统的YSZ热障涂层已经不能满足这一发展需求,因此迫切需要开发温度更高、热导率更低的新型热障涂层。本文对La_2(Zr_(0.7)Ce_(0.3))_2O_7(以下简称LZ7C3)热障涂层在重型发电燃气轮机中的应用进行了初步验证。结果表明,LZ7C3涂层具有比常规YSZ热障涂层更低的热导率(0.79～0.48Wm~(-1)K~(-1),相对传统YSZ涂层下降30%以上),且在1250℃的高温火焰台架试验中表现出优良的热循环寿命( 7370次),具有良好的应用前景。     

Spectroscopic investigations of Gd3Sc2Ga3O12 garnet doped with Cr^3＋ and Nd^3＋ ions

Absorption, excitation and emission spectra as well as decay time measurements at 10, 77, and 300 K were performed for Ga₃Gd₃Sc₂O₁₂ garnet single-crystal doped with Cr³⁺ and Nd³⁺ ions. Strong reabsorption of Cr³⁺ emission by Nd³⁺ absorption lines was observed. The assignments of f–f and d–d transitions were proposed. The broad emission band of chromium ions is an indication that weak/intermediate crystal field strength is present at the Cr³⁺ site.     

Precipitation of sodium silicofluoride (Na2SiF6) and cryolite (Na3AlF6) from HF/HCl leach liquors of alumino-silicates

The HF + HCl leach liquor generated from the dissolution of silica, alumina and silicate gangue minerals in a low-grade molybdenite concentrate contains H₂SiF₆ and H₃AlF₆. Studies were conducted to recover the two valuable fluorides as Na₂SiF₆ and Na₃AlF₆ (synthetic cryolite) by precipitation with Na₂CO₃ from the leach liquor. An initial investigation was carried out to determine the precipitation conditions for Na₂SiF₆ and Na₃AlF₆ from their individual acid solutions. Subsequently, the conditions were determined for the selective precipitation of the two fluorides from a synthetic mixed acid solution similar to the leach liquor. When the acid solution was neutralized with 3 mol/L Na₂CO₃, Na₂SiF₆ precipitated first at pH 1.35 whilst Na₃AlF₆ required an increase in pH above 2.2 before it precipitated. Maximum recovery of the two fluorides was best achieved at about 50 °C. A similar trend was observed for the precipitation of Na₂SiF₆ and Na₃AlF₆ from the leach liquor of molybdenite upgrading. Phases of precipitated fluorides were identified by XRD and surface morphology by SEM. The purity of the Na₂SiF₆ precipitate was 99.5% whereas Na₃AlF₆ was contaminated with Na₃FeF₆.     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3：Eu^3＋ phosphor

The Gd2O2CO3：Eu^3＋ with type-Ⅱ structure phosphor was successfully synthesized via flux method at 400 ℃ and their photoluminescence properties in vacuum ultraviolet （VUV） region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO3^2- host absorption and charge transfer （CT） of Gd^3＋-O2^- were observed for Gd2O2CO3：Eu^3＋. Under 172 nm excitation, Gd2O2CO3：Eu^3＋ exhibited strong red emission with good color purity, indicating Eu^3＋ ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3：Eu^3＋ was （x=0.652, y=0.345）. The photoluminescence quenching concentration of Eu^3＋ excited by 172 nm for Gd2O2CO3：Eu^3＋ was about 5%. Gd2O2CO3：Eu^3＋ would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.     

Partial oxidation of methane on Ni/CeO2-ZrO2/γ-Al2O3 prepared using different processes

The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane （POM） were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were characterized by XRD, TPR, H2-chemsorption, and TG-DTA. For fresh catalysts, the results showed that the salt precursor mixing catalyst （ATOM） presented better performance than the catalysts prepared by the precipitator mixing method （MOL） and the powder mechanically mixing method （MECH）. The result of XRD suggested that the interaction between CeO2-ZrO2 and Al2O3 in ATOM sample was stronger than the others, which led to more lattice defects and thereby better initial activity. Moreover, the MECH sample had the best stability and the least coke deposition in 24 h stability tests. The results of TPR and H2-chemsorption indicated that the intimate contact of Ni-Al in MECH sample enhanced the ability of resisting coke deposition and metal sintering.     

Leaching of a sphalerite concentrate with H2SO4–HNO3 solutions in the presence of C2Cl4

The enhanced leaching of sphalerite concentrates in H₂SO₄–HNO₃ solutions and the extraction of sulfur with tetrachloroethylene were studied. Variables of the process were investigated including leaching temperature, reaction time, liquid / solid ratio, and tetrachloroethylene concentration. The number of cycles that tetrachloroethylene could be recycled did not have a significant effect on zinc extraction. The results indicated that 99.6% zinc extraction was obtained after three hours of leaching at 85 °C and 0.1 MPa O₂, when 20 g of sphalerite concentrate were leached in a 200 ml solution containing 2.0 mol/L H₂SO₄ and 0.2 mol/L HNO₃, in the presence of 10 ml C₂Cl₄. Leaching rates were significantly improved under these conditions.     

Low-field magnetic entropy changes in （Gd1-xYx）3Al2 alloys

The effects of Y substitution on the magnetic properties and magnetocaloric effect of(Gd1-xYx)3Al2(x=0-0.3) alloys were investigated by X-ray diffraction and magnetization measurements.All samples crystallized in single phase with Zr3Al2-type tetragonal structure.The lattice parameters and magnetic transition temperature decreased obviously with increasing Y content.The magnetic entropy change and refrigerant capacity of these alloys were calculated.The adjustable transition temperature and favorable proper...     

Luminescence properties of YAl3（BO3）4 phosphors doped with Eu^3＋ ions

YAl3 （BO3）4： Eu^3＋ phosphors were prepared by the conventional solid state reaction. The phase structure and morphology were investigated by X-ray diffraction （XRD） and scanning electron microscope （SEM）. Doping YAl3（BO3）4： Eu^3＋ phosphors with concentration of Eu^3＋ ions of 0, 2, 5, 8 and 10 mol% were studied and their luminescent properties at room temperature were discussed. The excitation spectrum of Y0.95Eu0.05Al3（BO3）4 was composed of a broad band centered at about 252 nm and a group of lines in the longer wavelength region. In the emission spectra, the peak wavelength was about 614 nm under a 252 nm UV excitation. The optimal doping concentration of Eu^3＋ ions in YAl3（BO3）4： Eu^3＋ phosphors was 8 mol%.     

Preparation and Characterization of Red Luminescent Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ Nanophosphor

Nanophosphor with the nominal composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ （CZTOPN） was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti（OC4H9）4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis （TG-DSC）, powder X-ray diffraction （XRD）, and scan election microscopy （SEM）. Results of TG-DSC and XRD reveal that the composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.