CeO2/SiO2复合磨粒合成与表征

以SiO2溶胶作内核,分别以(NH4)2Ce(NO3)6、CO(NH2)2混合溶液与Ce(NO3)3·6H2O、HMT混合溶液作壳层前驱体,均相沉淀工艺制备了两种不同的CeO2/SiO2复合磨粒.利用XRD、TEM和FF-IR对比了两种磨粒的物相组成、纳米形貌和化学结构,并对包覆机理进行了解释;结果表明:以(NH4)2Ce(NO3)6、CO(NH2)2为原料制备的CeO2/SiO2复合磨粒包覆程度低;以Ce(NO3)3·6H2O、HMT为原料制备的CeO2/SiO2复合磨粒为壳-核包覆结构完整的纳米微球,粒径约110 nm,核层为无定形SiO2,壳层为立方萤石型CeO2颗粒,CeO2壳层与SiO2内核之间存在Si-O-Ce化学键,形成了稳定的壳核结构.     

AFt@SiO2核/壳结构的制备及其性能研究

钙矾石(AFt,3CaO·Al2O3·3CaSO4·32H2O)因其结构中含有大量结晶水而具备了用于制造阻燃材料的潜质.以Al2(SO4)3·18H2O和Ca(OH)2为原料,在200℃条件下通过水热反应进行钙矾石的合成实验,研究了反应物浓度,反应时间,pH值对反应产物的影响,并使用改进的St?ber法在钙矾石晶体表面包覆SiO2壳层,制备AFt/SiO2核/壳结构.采用XRD、SEM、FT-IR、TG等方法对产物表征测试.结果表明:通过水热法可以快速合成出高纯度,结晶性好的钙矾石晶体,pH=10是钙矾石晶体生长的适宜条件;SiO2壳层的包覆能控制AFt的脱水速率,也会降低AFt的含水率.     

核壳结构SiO_2/SnO_2纳米复合微粒的合成与表征

文章从TEOS出发,先水解制备了纳米二氧化硅微粒,再以五水四氯化锡为锡源,碳酸铵为沉淀剂,通过控制反应条件,用共沉淀法在二氧化硅表面包覆上一层锡化物层,经600℃煅烧2 h后形成了具有核壳结构的SiO2/SnO2纳米复合微粒,并用透射电镜、激光粒度仪、FTIR等手段对其形貌、结构、组成进行了表征。结果表明：形成的核壳结构SiO2/SnO2纳米复合微粒是以二氧化硅为核,氧化锡为壳,内核直径约为120 nm,壳层厚度为8～18 nm;氧化锡基本以成膜包覆为主,伴有部分氧化锡自身成核团聚。     

磺化沥青包覆石墨制备复合材料

磺化沥青具备溶于水的特性,采用液相浸渍法,在水相体系下包覆天然鳞片石墨,然后碳化处理,得到核壳结构的碳涂层材料。采用扫描电镜(SEM)对所制备的碳复合材料进行表征,结果表明,包覆型复合材料经过碳化后可以提高石墨的密度;包覆层可以将石墨晶体的边缘和缺陷遮掩,形成一种具有核壳结构的碳复合材料。     

基于微生物和纳米TiO2的双负载核壳水凝胶的制备及性能

设计了能同时利用微生物和光催化剂,分步逐级降解亚甲基蓝(MB)的多功能双负载核壳水凝胶,核为聚乙烯醇和羟乙基纤维素包覆酵母菌,壳为海藻酸钠和钙离子负载纳米TiO2.SEM结果表明,核壳结构清晰可辨;显微镜照片和荧光标记照片证明了核中酵母菌的存在;XRD结果证明了壳中纳米TiO2的负载;FTIR、XPS结果证实了核壳结构...     

响应面优化核-壳结构TiO2@SiO2的制备工艺

以金红石二氧化钛为核、硅酸钠作为包覆剂,并流法制备核-壳结构TiO₂@SiO₂。采用单因素实验探究pH、温度、搅拌速率、包覆时间、二氧化钛初始浓度、包覆剂用量及陈化时间7个因素对产品酸溶率的影响,响应面实验优化制备工艺,用TEM、XPS、SEM、XRD、FT-IR、UV-vis等手段对产物进行表征。结果表明,固定搅拌速率为300 r/min、包覆时间为60 min、二氧化钛初始质量浓度为200 g/L,各因素对酸溶率的影响次序由大到小为：包覆剂用量、温度、pH、陈化时间,在较优工艺条件包覆剂用量为4.41%、温度为83.65 ℃、pH为9.59、陈化时间为25.62 h下,产物的酸溶率为3.43%。壳层为无定形二氧化硅、厚度约为5 nm左右的致密膜,以Ti—O—Si化学键合在二氧化钛核的表面,核-壳结构的TiO₂@SiO₂具有更高的紫外屏蔽能力。     

超细二氧化钛粉体的表面无机包膜及其机理

在超细悬浮的TiO2颗粒表面化学沉积Si(OH)4和Al(OH)3,经过洗涤、脱水、干燥、煅烧处理后形成致密的SiO2,Al2O3包膜.研究了TiO2表面形成SiO2,Al2O3包膜的机理和工艺条件.利用扫描电镜、红外光谱和X射线荧光光谱对包覆产物进行了分析.结果表明:最佳包覆条件为:pH值在8～10,温度85～90℃,陈化时间1～3 h.     

金包覆的核壳结构纳米材料的制备进展

金、银等贵金属纳米材料具有独特的光学、电学和催化性能以及良好的生物兼容性,其在化学、物理、生物和医学等领域具有广泛的应用。以贵金属纳米金作为核或壳,制备成核壳结构复合纳米材料,这样的核壳材料同时具有核和壳的性质以及其他优越的性能,因此受到研究者的广泛青睐。金包覆纳米颗粒制备核壳结构的方法众多,主要对金包覆所形成的核壳型纳米材料的制备方法进行综述。     

水溶性沥青/石墨等温包覆过程的lnln分析法研究

水溶性沥青作为天然石墨的有效改性剂,在石墨表面包覆一层无定型碳形成"核-壳"型结构的C/C材料。在氮气保护下,采用热重分析仪对水溶性沥青包覆石墨复合材料的炭化过程进行动力学研究,得到了活化状态及络合参数。结果表明:水溶性沥青包覆石墨非等温干馏过程是该复合物的热解、缩聚过程;在快速升温条件下,包覆材料热解发生反应滞后,利于观察高温状态的中间态激活过程;lnln分析法研究复合材料包覆过程的表观活化能为9.266 kJ·mol~(-1),等温分解反应的平均活化自由能ΔG~≠、活化焓ΔH~≠和活化熵ΔS~≠分别为96.816 kJ·mol~(-1),2.497 kJ·mol~(-1)和-298.875 J·mol~(-1)·K~(-1);ΔH~≠和ΔG~≠的正值表明它们发生反应需要引入热量并具有非自发分解反应,ΔS~≠小于零,表明相应的激活态沥青在石墨表面包覆的排列程度高于初始状态,高温恒温可导致形成芳香核缩聚,通过逐渐热分解对石墨进行"包覆",炭化后可形成"核-壳"型结构的复合材料。这些结果有助于优化水溶性沥青包覆石墨炭化反应条件及反应炭化炉设计。     

核壳纳米材料制备及其在CO/CO2热催化加氢中的应用

采用多种包覆方法制备的核壳纳米材料具有许多优于单一材料的性能,其独特的核壳结构可产生出色的协同作用和新特性,现在已经广泛用于催化、吸附、储能与转化、药物传递和光学等领域。在CO/CO₂热催化加氢反应过程中,壳层包覆可对核体粒子表面进行修饰,如改变核体的表面电荷、官能团和反应特性等,从而提高核体的稳定性与分散性。核壳催化剂可形成封闭的内部微环境以富集反应物,提高反应速率和催化活性。部分核壳催化剂甚至还能实现接力催化,并提高体系内的能量利用率。主要介绍了核壳纳米材料的常用制备方法,不同类型壳层包覆的核壳催化剂在CO/CO₂热催化加氢中的应用进展,并对该领域的未来发展进行了展望。     

电工钢表面耐高温绝缘无机涂层的制备和表征

以磷酸和氢氧化铝为原料在90～100℃合成二聚磷酸三氢铝,将硅酸钠,草酸按一定比例加入到二聚磷酸三氢铝溶液中制备成粘度为0.16～0.2Pa.s的涂液。用浸渍提拉法在清洗过的电工钢表面涂覆,自然干燥12h后,经退火炉在600℃热处理1min得到耐高温绝缘涂层。用X射线衍射分析(XRD)、差热分析(DTA)、热重分析(TG)及显微镜研究了涂层组成变化。用Franklin烧损试验表征了涂层的绝缘能力。结果表明,磷酸和氢氧化铝比例为3.3∶1时生成二聚磷酸三氢铝产率最高,性能最稳定。硅酸钠的加入既可以加强涂层的结合力又可以改善涂液的分散性。螯合剂的加入使涂料稳定存放。涂层在300℃稳定使用。最高使用温度可达600℃。     

氧化铝粒子化学气相包覆氧化钛的过程研究

探讨了回转炉化学气相淀积（CVD）包覆新工艺,利用Ti（OC_4H_9）_4水解,在Al_2O_3粒子表面实现了TiO_2包覆,研究了包覆过程特征。结果表明,TiO_2在Al_2O_3粒子表面的包覆是成功的,并具有一定的致密性,包覆量为0.1%～10%;化学气相包覆过程中既存在成膜包覆,又存在成核包覆,通过控制反应物浓度等方法可以强化成膜包覆,提高包覆效果。     

Preparation,scratch adhesion and anti-corrosion performance of TiO2-MgO-BHA coating on Ti6Al4V implant by plasma electrolytic oxidation technique

Bovine hydroxyapatite (BHA) (from cortical bone), was selected as the main electrolyte for plasma electrolytic oxidation (PEO) on Ti6Al4V implant. The prepared PEO coatings were examined by X-ray diffraction, field emission scanning electron microscope and energy-dispersive X-ray spectroscopy. The surface roughness, adhesion strength, wettability, surface energy and corrosion behaviour of the film were also investigated. The results show that the oxide layer (26 μm) formation on the Ti6Al4V was rough and porous. The micro-pores were filled with anatase TiO₂, cubic MgO and hexagonal BHA particles. The porous structures and the compound particles were mainly composed of Mg, O, Ca, P, Ti, Na and Al. Unlike previous coatings produced from calcium and phosphorus inorganic solutions, the coating formation from a newly developed bovine bone-derived HA electrolyte revealed an additional MgO phase in the coating layer. Moreover, higher amount of single phase hexagonal crystalline BHA phase with a Ca/P ratio of 1.1 was achieved with a single PEO process. A film-to-substrate adhesion strength of 1862.24 mN and scratch hardness of about 4.1 GPa was achieved from this method. The TiO₂/MgO/BHA film exhibited better wettability, higher surface energy and superior corrosion resistance compared to the bare Ti6Al4V substrate.     

Preparation of nano - coating powder CaF2@Al(OH)3 and its application in Al2O3/Ti(C,N) self-lubricating ceramic tool materials

Nano CaF₂ particles of different sizes were prepared by direct precipitation. The diameters of nano CaF₂ particles prepared in mixed solvent can reach 5–7 nm, and can be effectively dispersed. The surface of nano CaF₂ was modified and coated by heterogeneous nucleation method. A shell layer of Al(OH)₃ was coated on the surface of nano CaF₂, and the structure and coating mechanism of the coated powder were analyzed. Under varying preparation conditions, the surface morphology of CaF₂@Al(OH)₃ was analyzed using TEM and SEM. The results showed that the coating powder showed good dispersion in mixed solvents, and the particle size of the composite powder was about 20 nm. Self-lubricating ceramic tool materials were prepared by adding coating particles to the Al₂O₃/Ti(C,N) matrix. The coating powder shell and the matrix material melt during sintering, so that CaF₂ forms nanostructures in the particles. thereby improving the mechanical properties of the material. Cutting experiments show that the addition of coating particles can effectively reduce the temperature, cutting force and friction coefficient in the cutting process of the tool, thus improving the cutting performance of the tool material.     

Development of T-ZnOw@Al2O3-incorporated low-temperature curing aluminium phosphate coating on Ti–6Al–4V alloy

In this study, a low-temperature curing aluminium phosphate coating was developed on a Ti–6Al–4V alloy by prolonged curing. The coating was composed of a phosphate binder, a T-ZnOw@Al₂O₃ core-shell curing agent, and an Al filler. The phosphate binder was produced by the reaction between phosphoric acid and aluminium hydroxide (P/Al = 3:1.4) and was mainly composed of Al(H₂PO₄)₃. The T-ZnOw@Al₂O₃ curing agent was produced by sol-gel routes and its core-shell microstructure was verified by transmission electron microscopy. The curing mechanism of the coating in the presence of T-ZnOw@Al₂O₃ was investigated by obtaining its thermogravimetric differential thermal analysis curves and measuring its weight loss. The results showed that zinc oxide was released during curing. Complete curing was achieved at a relatively low temperature of 70 °C after prolonged curing for 120 min (P:Zn = 10:1). This rendered the phosphate coating suitable for practical applications. Though the peculiar tetrapod-like shape of T-ZnOw disappeared after being surrounded by Al₂O₃, the refining of the T-ZnOw@Al₂O₃ core-shell particles resulted in a decrease in the curing time and an increase in the hardness of the coating (higher than that of the ZnO@Al₂O₃ curing agent). The Al filler improved the surface roughness and oxidation resistance of the coating at 800 °C. A crack-free aluminium phosphate coating was achieved at the P:Zn:Al mass ratio of 10:1:0.05.     

Facile synthesis of water-soluble luminescent mesoporous Tb(OH)3@SiO2 core-shell nanospheres

Luminescent mesoporous Tb(OH)₃@SiO₂ core-shell nanospheres were synthesized through W/O microemulsion process at ambient temperature. The negatively charged silica favors a coating of the positively charged Tb³⁺ composite. Thus, silicon layer was adsorbed on the surface of Tb(OH)₃ groups to form Tb-O-Si through electrostatic interaction. X-ray diffraction, field emission transmission electron microscopy (FE-TEM), energy-dispersive X-ray spectrometry, and Fourier transform infrared, UV/Visible, and photoluminescence spectroscopies were applied to examine the phase purity, crystallinity, surface morphology, and optical properties of the core-shell nanospheres. The FE-TEM results have revealed typically ordered mesoporous characteristics of the material with monodisperse spherical morphology in a narrow size distribution. The luminescent mesoporous core-shell nanospheres exposed remarkable splitting with broadening in the emission transition ⁵D₄ → ⁷F₅ (543 nm). In addition, the luminescent mesoporous core-shell nanospheres emit strong green fluorescence (from Tb³⁺) in the middle of the visible region under 325 nm (3.8) excitation. The luminescent mesoporous Tb(OH)₃@SiO₂ core-shell nanospheres can therefore be exploited as fluorescent probes in biomarkers or biolabeling, optical sensing, and drug delivery system. Further, these nanospheres could have potential use as scattering layers in dye-sensitized solar cells.     

SiO2和Al2O3在TiO2表面的成核包覆与成膜包覆

从理论和实验上研究了ＴｉＯ２表面包覆的机理和工艺条件,分析了ＴｉＯ２成膜包覆与成核包覆的动力学控制因素,并提出了 ＴｉＯ２与包覆物之间的微观结构模型．实验研究了对 ＴｉＯ２进行硅、铝二元包膜的过程,测得二氧化钛在浆液中的等电点为 ３．６． ｐＨ＝１０左右有最大的Ｚｅｔａ电位,有利于颗粒分散．硅酸聚合速度研究表明,ＰＨ＝９～１０时硅酸聚合速度降低,有利于形成均匀致密的膜,因而最佳包覆ｐＨ值为９～１０．从ＸＰＳ 谱中钛的 ２ｐ轨道电子结合能推测,包覆层的硅和铝是以化学键结合于 ＴｉＯ２表面．     

TiO_2薄膜制备条件对甲醛光催化降解性能的影响

以钛酸丁酯为前驱体,用溶胶-凝胶法制备了TiO2薄膜,并进行了甲醛的光催化降解实验,考察了制备条件对光催化降解性能的影响。结果表明,适宜的制备工艺条件为:溶胶体系pH=3,溶胶配方中V(钛酸丁酯)∶V(无水乙醇)∶V(水)∶V(冰醋酸)=5∶34∶2∶2,干溶胶在600℃下活化5h,制成的薄膜光催化降解甲醛降解率大于50%。     

Synthesis and evaluation of TaC nanocrystalline coating with excellent wear resistance,corrosion resistance,and biocompatibility

To improve the mechanical properties, corrosion resistance, and biocompatibility of implanted titanium alloys, a TaC nanocrystalline coating was deposited on Ti–6Al–4V alloy using a double-cathode glow discharge method. The microstructure of the newly developed coating was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The coating exhibits a dense and uniform structure, composed of equiaxed TaC grains with an average grain size of 15.2 nm. The mechanical properties of the TaC-coated Ti–6Al–4V alloy were evaluated by a scratch tester, a nanoindentation tester, and a ball-on-disc tribometer. The average hardness of the TaC nanocrystalline coating is about 6 times higher than that of uncoated Ti–6Al–4V alloy and the specific wear rate of the coating is two orders of magnitude lower than that for Ti–6Al–4V at applied normal loads of 4.9 N under dry sliding condition. The electrochemical behavior of the TaC nanocrystalline coating after soaking in Ringer's solution for different periods was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Furthermore, in vitro cytocompatibility of the coating was assessed using MC3T3-E1 mouse osteoblastic cells. The results showed that the TaC coating exhibits better corrosion resistance and biocompatibility as compared to uncoated Ti–6Al–4V alloy.     

连续热镀锌表面的钛盐钝化膜研究

研究了一种适用于连续热镀锌钢板表面处理的钛盐钝化膜.通过正交试验和单因素试验,确定了钛盐钝化工艺的最佳条件为:Ti(SO4)2 8 g/L、H2O2 80 mL/L、HNO3 6 mL/L、H3PO46 mL/L,钝化温度30℃,钝化时间1Os.扫描电镜和能谱分析发现,由最佳工艺得到的钝化膜均匀致密,由O、P、Ti和Z...