硝酸腐蚀对等离子喷涂YAG:Ce涂层发光性能的影响

为探讨荧光元素在腐蚀监测领域的应用,围绕Ce掺杂YAG(Y_3Al_5O_(12))粉末和涂层的制备,探讨硝酸腐蚀对涂层发光性能的影响。结果表明高温固相法形成的YAG:Ce粉末主要为YAG相,等离子喷涂涂层则以YAG和YAP(YAlO_3)相为主。经过在硝酸中腐蚀不同的时间后,涂层的孔隙率和衍射峰的强度均增加。同时,衍射峰的主峰位置发生移动。涂层的发光强度随腐蚀时间的增加呈现先增加再降低之后增大的波动趋势。涂层的发光强度受其孔隙率、衍射峰位置和强度等多种因素的影响。     

溶胶-凝胶法制备YAG颗粒及在电接触材料中的应用

以硝酸钇(Y(NO₃)₃6H₂O)、硝酸铝(Al(NO₃)₃9H₂O)为主要原料,六次甲基四胺作为催化剂,采用溶胶-凝胶法合成Y₃Al₅O₁₂(YAG)纳米颗粒,并以YAG颗粒为第二相增强材料,通过粉末冶金工艺制备Ag/YAG电接触复合材料;采用X-射线衍射仪(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),傅里叶红外光谱(FT-IR)、硬度计、电导率仪等方法对其进行表征。结果表明：在水浴温度为50℃的条件下成功采用sol-gel法合成YAG纳米颗粒,物相纯度高;随着催化剂六次甲基四胺加入量的增加,YAG粉末颗粒粘连在一起,并出现大孔;以YAG为第二相增强材料制备的Ag/YAG电接触复合片材电阻率较低,维氏硬度大于80。     

黏结相对YSZ基高温封严涂层沉积效率和热循环性能的影响∗

为解决 YSZ(Y₂O₃ 部分稳定的 ZrO₂ ) 陶瓷基高温封严涂层沉积效率较低和易于过早剥落失效的问题,选择氧化铝 (Al ₂O₃ )、钇铝石榴石(Y₃Al ₅O₁₂ ,YAG)及镁铝尖晶石(MgAl ₂O₄ )为三种高温黏结相,通过喷雾造粒的方法分别制备出 B0(无黏结相)、B1(含 Al ₂O₃ )、B2(含 YAG)和 B3(含 MgAl ₂O₄ )等四种 YSZ 基团聚颗粒,研究黏结相对涂层沉积效率和热循环性能的影响。 结果表明,YAG 的黏附和包裹作用最强,与 B0 型粉末相比,B2 型粉末的沉积效率提高了 181. 49%;热循环过程中不断增长的裂纹扩展驱动力和陶瓷材料的脆性属性是导致陶瓷涂层剥落失效的主要原因,由于 YAG 相的弥散增韧作用,B2 型涂层的断口呈现出类韧窝形貌,与 B0 型涂层相比,B2 型涂层的断裂韧性提高了 39. 76%,热循环寿命提高了 43. 68%。 YAG 黏结相的添加显著地提高了 YSZ 陶瓷基高温封严涂层的沉积效率,同时较好地提高了涂层的热循环寿命。     

Ba(Mg1/3Ta2/3)O3热障涂层的制备及抗热震性能研究

本文以BaCO₃、MgO、Ta₂O₅为原料,采用固相反应法合成了Ba(Mg_1/3Ta_2/3)O₃(简称BMT)陶瓷粉末,利用大气等离子喷涂技术制备了BMT/YSZ双层陶瓷涂层。利用XRD、SEM和金相显微镜检测了BMT粉体及涂层的物相组成和显微结构。采用水淬法考核了涂层的抗热震性能。结果表明：1450℃下煅烧4h可合成出具有复合钙钛矿结构的BMT粉末,粉末具有良好的高温相结构稳定性。等离子喷涂制备的BMT/YSZ涂层组织致密,涂层系统中各界面结合紧密。涂层在室温至1150℃间热震9次后发生片状剥落,剥落位置位于BMT层间,BMT材料低的断裂韧性和第二相Ba₃Ta₅O₁₅的存在是导致涂层失效的主要原因。     

多孔ZrO2-8 wt% Y2O3涂层的制备及性能

航空发动机的效率与转动叶片和机匣之间的间隙密切相关。为了控制转子和静子之间的间隙,需要在机匣表面制备可磨耗的封严涂层。在发动机的高温端,ZrO₂-8wt% Y₂O₃涂层是经常采用的封严涂层基体。涂层中的孔隙可以增加涂层的可磨耗性。本文利用聚苯酯(PHB)增加等离子喷涂的ZrO₂-8 wt% Y₂O₃涂层的孔隙率。为了避免聚苯酯在等离子喷涂过程中的烧损,利用溶胶-凝胶法在聚苯酯颗粒表面沉积一层TiO₂层。文中将讨论采用此方法制成的涂层的形态、孔隙率、硬度和可磨耗性。结果表明,在喷涂粉末中混合包覆型的聚苯酯后,涂层的孔隙率将会得到提升,涂层硬度将会下降。磨耗试验的结果表明涂层的磨耗深度随着涂层孔隙率的增加而增加。     

机械合金化制备Fe-Cr-Mn-N奥氏体不锈钢厚熔覆涂层的研究

本实验采用机械合金化方法制备了Fe₇₆Cr₁₂Mn₁₂N合金粉末,研究其机械合金化过程,并对机械合金化的机制进行探讨。研究表明,棒磨4小时时粉末就可以完全合金化,并且随着棒磨时间增加,衍射峰逐渐宽化,衍射强度逐渐降低。粉末颗粒形貌也逐渐类球形化。机械合金化得到的非球形固溶体粉末也可用于激光熔化沉积(LMD)增材制造技术,解决了LMD对球形粉末的局限性,机械合金化粉末通过LMD技术得到的厚熔覆涂层具有较好的耐蚀性,其物相结构是BCC+FCC的双相结构,同时在打印过程中有Cr₂N生成,维氏硬度最高达到456.3HV。     

等离子喷涂不同比例掺杂G-Al2O3-13%TiO2复合涂层的耐腐蚀性能

为解决等离子喷涂陶瓷涂层孔隙率高的问题,将 Al₂O₃-13%TiO₂(AT13)粉体与 CaO-MgO-Al₂O₃ -SiO₂(G)硅酸盐玻璃粉按不同比例混合,采用等离子喷涂技术制备得到 AT13、G ∶AT13 = 1 ∶ 10(GA-1)、G ∶AT13 = 2 ∶ 10 (GA- 2)、 G ∶AT13 = 3 ∶10 (GA-3) 这 4 种涂层,对 4 种涂层的相组成和微观形貌进行了分析,利用浸泡腐蚀与电化学腐蚀试验分别对涂层耐腐蚀性能进行了研究。 结果表明:4 种涂层均由 α-Al₂O₃ 、γ-Al₂O₃ 、金红石型 TiO₂ 和 Al₂TiO₅ 相组成;AT13、 GA-1、GA-2 和 GA-3 涂层的孔隙率分别为 13. 2%、11. 4%、7. 8%和 8. 8%;在 3. 5% NaCl 溶液中浸泡腐蚀 1000 h 后,3 种 GA-X (X= 1,2,3)涂层的腐蚀面积与纯 AT13 涂层相比都有所减小;电化学阻抗(EIS)和动电位极化曲线(PD)结果表明涂层的耐腐蚀性随着玻璃粉的掺入而提高,但玻璃粉掺量不是越高越好,以 G ∶AT13= 2 ∶10 比例掺杂的涂层耐腐蚀性能最优。     

功率对激光熔覆(Fe0.25Co0.25Ni0.25Cr0.125Mo0.125)86B14涂层组织均质性及磨损性能的影响*

目前激光熔覆缺少对涂层组织、相结构纵向均质性与性能关联的研究。采用激光熔覆技术,选取不同的激光功率,制备(Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)₈₆B₁₄ 高熵合金涂层;借助电子探针(EPMA)、扫描电子显微镜(SEM)、能谱仪(EDS)和 X 射线衍射仪(XRD)等观察涂层微观组织与物相纵向分布,利用显微硬度计和摩擦磨损试验机测试涂层不同深度部位显微硬度及磨损性能,分析激光功率对熔覆(Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)₈₆B₁₄ 涂层纵向组织、物相分布影响规律及磨损性能。结果表明：三种功率下,涂层均由 BCC+FCC 相、硬质相 Mo₂B 组成,Mo₂B 在枝晶间富集。随着功率的增加,涂层中底部显微组织由细枝晶向粗大的柱状晶转变。三种涂层硬度均由表及里先增加后降低,摩擦因数先降低后增加;但是当激光功率为 1.6 kW 时,涂层呈现以 BCC 相为主的 FCC+BCC 双相结构,且由表及里 BCC 相含量不断增加、Mo₂B 含量逐渐减少,涂层组织均质化最高,摩擦因数变化梯度最小,耐磨损性能最佳。激光功率会影响熔覆高熵合金耐磨涂层均质性,进而影响摩擦性能的稳定性。     

一种新型经济高效非晶涂层的制备与性能表征

利用火焰喷涂技术喷涂自制的气雾化合金粉末取代非晶粉末,制备了NiFeBSiNb非晶纳米晶涂层。分别对粉末和涂层的微观组织结构和热力学性能进行了表征。结果表明,自制的合金粉末球形度较好,大多为球形或椭球形;主要为晶体结构,由Nb₂Ni₂₁B₆晶体相和(Ni,Fe)₂₃B₆固溶体组成。而经过火焰喷涂制备的涂层,形成了非晶相和纳米晶相。通过公式计算此合金体系粉末和涂层形成非晶相的临界冷却速率分别为6.01×10₅K/s和4.56×10₃K/s,解释了在粉末制备过程中较难形成非晶相而喷涂过程中形成非晶结构比较容易。对涂层的摩擦磨损性能进行了测试,涂层摩擦系数仅为0.17,具有优异的耐磨性能。     

SiC晶须对等离子喷涂YSZ涂层显微结构的影响

为了研究SiC晶须对等离子喷涂YSZ（Y₂O₃部分稳定的ZrO₂）涂层显微结构的影响规律,采用喷雾造粒技术制备了晶须含量分别为0%、1%、2%和3%（质量分数）的团聚YSZ颗粒（0#、1#、2#和3#粉末）,利用等离子喷涂技术（APS）分别制备了0#、1#、2#和3#等4组涂层。利用扫描电镜（SEM）及金相显微镜等测试分析设备研究SiC晶须分散工艺和定量表征方法,以及团聚颗粒的形态和涂层的显微结构,并分析了含晶须涂层的成型过程。结果表明：机械搅拌时间增加至5 h时,晶须具有较好的分散程度,对应的晶须面积分数为11.03%。含晶须的团聚颗粒主要呈“水滴状”和“纺锤状”,1#、2#和3#粉末中“水滴状”和“纺锤状”团聚颗粒的数量比例分别为16.5%,22.7%和39.3%。由于非水平态晶须对颗粒中未熔融原粉末在冲击和铺展过程的阻碍作用,涂层的孔隙率随着晶须含量的增加而增加,0#涂层的孔隙率为3.89%,1#、2#和3#涂层的孔隙率分别是0#涂层的3.15倍、4.17倍和7.52倍。     

Preparation of YAG：Ce^3＋ phosphor by sol-gel low temperature combustion method and its luminescent properties

YAG：Ce^3＋ phosphor was prepared by sol-gel low-temperature combustion method. The effects of the precursor properties and calcining temperature on the crystallization process, microscopic morphology and luminescent properties of phosphor were studied. The results indicate that the pure phase of YAG can be obtained at 800 ℃ by sol-gel low temperature combustion method, using citric acid as complexing agent. When the molar ratio of metal ion to citric acid is 2.0 and pH value is 2, the crystallinity increases and the phosphor particle size grows up gradually with the increase of the calcining temperature. The powders were characterized through thermal analysis, X-ray diffraction analysis and scanning electron microscope analysis. The excitation spectra of YAG：Ce^3＋ phosphor take on a double peak structure, and the peak value of the main excitation spectra occurs at 460 nm and that of the emission spectra is near 530 nm. With the gradual increase of the calcining temperature, the peak position of excitation and emission spectra remains basically unchanged, but its relative intensity increases gradually.     

等离子喷涂工艺参数对YSZ:Tm涂层发光性能的影响

为提高荧光涂层在热障涂层中的适配性,本研究制备了Tm掺杂YSZ(Y2O3-ZrO2)粉末和涂层,探讨了等离子喷涂工艺参数对其发光性能的影响。结果表明:化学沉淀法制备粉末的过程中,静置陈化时间在15 h以上、母液中的Zr4+浓度为0.2 mol/L时氧化钇可完全固溶到基体粉末中。Tm的掺杂浓度降低,粉末的发光强度增加显著。等离子喷涂距离和功率对涂层的发光性能有明显影响,在现有范围内,喷涂距离和功率越小,发光强度越高。     

Formation of molybdenum boride cermet coating by the detonation spray process

The effects of the powder particle size and the acetylene/oxygen gas flow ratio during the detonation spray process on the amount of molybdenum phase, porosity, and hardness of the coatings using MoB powder were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The results show that the presence of metallic molybdenum in the coating results from decomposition of MoB powder during thermal spray. The compositions of the coatings are metallic Mo, MoB, and Mo₂B, which are different from the phases of the original powder. The amount of molybdenum phase increases monotonously with the oxygen/acetylene ratio, but the increasing rate for the fine powder is faster than that for the coarse powder. The porosity and hardness of the coating are related to the amount of molybdenum phase. The phase constitution of the coating is discussed.     

Effect of PEG Addition on the Properties of YAG:Ce Phosphor Synthesized via a Homogeneous Precipitation Method

在均相沉淀法制备YAG:Ce荧光粉前驱体的过程中,分别将分子量为6000和10000的聚乙二醇（PEG）作为分散剂添加到反应体系中。傅里叶变换红外光谱结果未发现不同分子量聚乙二醇的加入会对所制得的YAG:Ce前驱体产物的化学组成产生明显影响。相比于未添加聚乙二醇的样品,扫描电子显微镜（SEM）图像显示随着聚乙二醇的加入荧光粉的颗粒尺寸明显减小。在添加聚乙二醇的样品中,差示扫描量热分析（DSC）和X射线衍射（XRD）的结果证实了在钇铝石榴石（YAG）的结晶过程中没有任何中间相的形成,表明聚乙二醇的加入能够显著地促进YAG晶相的形成并且同时抑制Ce3+的氧化反应,最终大幅提高YAG:Ce荧光粉的荧光性能。     

Crystallization, morphology and luminescent properties of YAG：Ce^3＋ phosphor powder prepared by polyacrylamide gel method

A novel synthesis process, based on the polyacrylamide gel method, was used to prepare Ce-doped YAG phosphor powders. Effects of heat treatment parameters, temperature and holding time, the fluxes, and atmosphere on microstructure and particle morphology as well as luminescent properties of YAG：Ce^3＋ phosphor powders were studied by X-ray powder diffractometry, scanning electron microscopy, and fluorescence spectrophotometry. The results show that the formation temperature （1 000 ℃） of pure YAG phase is significant low when being synthesized by the polyacrylamide gel method, compared with solid-state reaction. For luminescent properties, the intensity of emission of YAG：Ce^3＋ phosphor increases steadily with increasing temperature from 900 ℃ to 1 300 ℃ and prolonging holding time from 100 min to 400 min. But blue shift phenomenon is observed for 400 min calcination Fluxes as BaF2 and H3BO3 can enhance the intensity of emission of phosphor due to the improvement of crystallization of YAG and the stabilization of trivalence cerium ion in YAG host lattice at high temperature. Weak reduction atmosphere can contribute to improvement of the emission intensity of YAG：Ce^3＋ phosphor powders.     

Effect of Spraying Powders Size on the Microstructure,Bonding Strength,and Microhardness of MoSi2 Coating Prepared by Air Plasma Spraying

Molybdenum disilicide (MoSi₂) coatings were deposited on carbon steel by air plasma spraying technology with different feedstock powder sizes (i.e., powder A: ?15 + 2.5 μm, powder B: ?30 + 15 μm, powder C: ?54 + 30 μm, powder D: ?74 + 54 μm and powder E: ?106 + 74 μm). Phase composition and microstructure of coatings were characterized by x-ray diffraction (XRD) and scanning electron microscope. The bonding strength and microhardness of coatings were also evaluated. The XRD results show that there exists mutual transformation between T-MoSi₂ and H-MoSi₂ phase and part of Mo-rich phases are formed because of oxidization during the spraying process. With the increase of spraying powders size, the content of Mo-rich phases (Mo or Mo₅Si₃) and molybdenum oxide (MoO₃) in coatings decreases, and that of disilicide-rich phase (MoSi₂) in coatings increases. The oxidation degree of MoSi₂ particle gradually decreases during the spraying process with the increase of spraying powders size. The MoSi₂ is the main phase of the as-sprayed coatings when the spraying powders size is beyond 30 μm. With the increase of spraying powders size, the porosity of the as-sprayed coating increases, and the bonding strength of the coating gradually decreases. The hardness of coatings first increases and then decreases with the increase of spraying powders size.     

Yb:YAG与Nd:YAG纳米晶的制备及性能

通过超声-微波辅助醇盐水解沉淀法合成了Yb:YAG与Nd:YAG纳米晶。研究了微波辐射功率、微波辐射时间及煅烧温度对产物的影响。采用X-射线粉末衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)及光致发光谱(PL)等对Yb:YAG与Nd:YAG纳米晶进行表征。结果表明,在微波辐射功率385 W、微波辐射时间30 min、煅烧温度1100 C条件下,可以获得纯相Yb:YAG与Nd:YAG纳米晶。当煅烧温度为1100 C时,Yb:YAG与Nd:YAG纳米晶的合作发光强度均达到最大值。     

粉末粒度对WC-Co涂层结构和性能的影响

采用低功率内送粉等离子喷涂设备,选择两种粒度不同的WC-Co粉末,在不同功率下,在不锈钢基体上制备WC-Co涂层。利用XRD、SEM等分析手段对原始粉末和涂层的显微结构和物相组成进行观察和分析,利用显微硬度仪测量涂层显微硬度。结果表明:与细粉相比,粗粉喷涂涂层的组织致密、均匀,孔隙率小。粗粉喷涂涂层显微硬度可达1500 HV以上,涂层主晶相是WC,也存在少量W2C相,随着等离子能量增加,W2C增多;细粉喷涂涂层,WC发生大量的脱碳分解,涂层主晶相是W2C,显微硬度低。因此粗粉在适当功率下更适合低能等离子喷涂。     

Effect of processing parameters on the microstructures and corrosion behaviour of high‐velocity oxy‐fuel (HVOF) sprayed Fe‐based amorphous metallic coatings

A FeCrMoMnWBCSi amorphous metallic coating was prepared by using high‐velocity oxy‐fuel spray. The influence of processing parameters on microstructure, porosity level, amorphous phase fraction and corrosion behaviour of the coatings was characterised by scanning electron microscopy, X‐ray diffraction, differential scanning calorimeter and electrochemical methods. The results indicated that the microstructures of the coatings were sensitive to the spray parameters considerably. Porosity and unmelted particle proportion decreased with the oxygen/fuel (O/F) ratio and increased with the powder feed rate. The trend of oxides content was opposite to the porosity and unmelted particle proportion. The coatings obtained with higher O/F ratio and lower powder feed rate exhibited higher hardness. The low coating hardness was mainly due to the high porosity especially when the porosity was higher than 1.21%. The spraying parameters strongly affected the amorphous phase fraction. There was a critical passive current density for balancing the porosity and the amorphous phase fraction. Corrosion resistance is dominant by the amorphous phase fraction when the porosity is less than 1.21%, while by porosity when it is higher than that. Open‐circuit potential, potentiodynamic polarisation and electrochemical impedance spectroscopy results showed that the coatings obtained with the O/F ratio of 4.2 and the powder feed rate of 40 g/min exhibiting the best corrosion resistance in 1 wt% sodium chloride solution.     

溶剂热法合成YAG:Ce荧光粉体的研究

采用溶剂热法,以乙二胺为溶剂,碳酸氢铵沉淀法制备的沉淀产物为前驱体,在低温下合成了YAG:Ce荧光粉体.研究了反应时间对合成产物的组成、分散性以及荧光性能的影响,结果表明:在200 ℃低温保温5 h条件下,可得到颗粒尺寸为260～280 nm的球形YAG:Ce颗粒,颗粒尺寸均匀,且分散性好;荧光性能表征显示,其发射光谱为一宽带,峰值在530 nm附近,对应于Ce~(3+)的最低5d能级到4f能级跃迁所发出的光,可与高效蓝光LED匹配制备双基色白光LED,用于新型节能光源.