正硅酸锂陶瓷氚增殖剂辐照后力学性能分析

针对聚变堆氦冷固态产氚包层中固态氚增殖剂小球辐照产氚性能数据的需求,基于中国先进研究堆(CARR)堆固态氚增殖剂堆内辐照考核研究平台开展的固态氚增殖剂CARR堆内辐照在线氚提取试验(CIPTISE),设计研制了密闭式辐照盒,装载天然丰度的Li₄SiO₄、50%Li-6丰度的Li₄SiO₄两种氚增殖剂小球材料,开展锂陶瓷氚增殖剂小球辐照前、后的力学、微观等性能测试分析对比,为固态氚增殖包层产氚分析以及燃料循环氚提取工艺设计提供依据。     

液滴-冷凝法制备磷酸盐陶瓷微球颗粒

介绍了一种制备磷酸盐陶瓷微球的工艺--液滴-冷凝法工艺,该工艺以生物陶瓷羟基磷灰石[Ca10(PO4)6(OH)2,HA]和β-磷酸三钙[β-Ca3(PO4)2,β-TCP]为主料制备了磷酸盐陶瓷微球.采用扫描电镜、X射线衍射分别对磷酸盐陶瓷微球的微观形貌、相组成进行了表征.制备的微球主要由β-Ca3(PO4)2和Mg3(PO4)2组成,其表面和内部都存在丰富的微孔且孔间互相贯通,有望在骨修复材料和药物缓释载体中得到应用.与其它制备工艺相比较,液滴-冷凝法在制备粒径均匀的陶瓷微球方面具有优越性.     

空心球型二氧化硅担载Li_3PO_4催化剂的制备及催化效果研究

笔者以正硅酸乙酯(TEOS)为硅源,氨水溶液为催化剂,聚乙烯吡咯烷酮(PVP)功能化的聚苯乙烯为模板,在乙醇介质中利用一步法制得纳米空心二氧化硅,并用TEM、XRD、BET、TG、FTIR等表征手段对SiO_2粉体进行分析。首先,以苯乙烯(St)为单体,过硫酸铵为引发剂,聚乙烯吡咯烷酮为分散剂,水为分散介质,单分散聚合法制备功能化的聚苯乙烯,可得到平均粒径为90 nm的聚苯乙烯微球。以这种微球为模板,在乙醇/氨水介质中,正硅酸乙酯发生水解和缩合,在聚苯乙烯微球包覆形成SiO_2,同时PS核被溶解,得到纳米空心二氧化硅微球。研究氨水用量、TEOS用量及反应时间等因素对二氧化硅微球形貌和产率的影响。以空心纳米二氧化硅为Li_3PO_4催化剂载体,催化环氧丙烷的异构化,与以硅胶作为载体的Li_3PO_4催化剂的催化效果进行比较。结果表明,使用空心球形二氧化硅代替硅胶作为催化剂载体可提高环氧丙烷转化率和烯丙醇的选择性,降低反应温度和副产物选择性。     

Li_2O-Al_2O_3-SiO_2-B_2O_3系统玻璃纤维的核化晶化机理

本文运用扫描电镜、X射线衍射定性分析和定量分析等手段,研究了以TiO_2为成核剂的Li_2O-Al_2O_3-SiO_2-B_2O_3系统玻璃纤维的核化晶化机理。结果表明,不加TiO_2时,纤维析晶与同成份的块状玻璃明显不同,而且析晶具有明显的方向性。添加TiO_2后,整个纤维内部均匀析晶。另外,TiO_2的加入降低了高温粘度,升高了低温粘度,加快了析晶速度,并促使β-锂霞石(Li_2O·Al_2O_3·2SiO_2)较快地向β-锂辉石(Li_2O·Al_2O_3·4SiO_2)转变。     

Li_4SiO_4的制备表征及CO_2吸附与模拟

采用柠檬酸.乙醇络合法,以柠檬酸,乙醇、硝酸锂、正硅酸乙酯为原料制备了硅酸锂(Li_4SiO_4)超细晶体粉末,采用TG-DSC、XRD、SEM等手段对Li_4SiO_4的前体及Li_4SiO_4晶体粉末进行了表征,分析了凝胶的热分解变化过程和球状晶形结构的形成过程.在800℃下焙烧2 h,制备出的Li_4SiO_4超细晶体粉末为球状晶型,晶型完整、均匀.采用TG-DSC对Li_4SiO_4晶体粉末在程序升温和恒温状态下吸附CO_2的性能进行了研究,结果表明:最佳吸附温度为700℃,90 min样品吸附CO_2量可达吸附剂质量的32.2%.用吸附模型对Li_4SiO_4吸附CO_2进行模拟,模型模拟的数据与实验数据吻合较好.     

锂离子电池负极材料Li4Ti4.9Ni0.1O12的制备及其电化学性能

以Li_2CO_3、TiO_2、Ni(CH_3COO)_2×4H_2O为原料,采用固相法制备尖晶石型Li_4Ti_(4.9)Ni_(0.1)O_(12)锂离子负极材料。通过X射线衍射(XRD)、扫描电镜(SEM)、恒流充放电测试以及交流阻抗等技术对材料进行了结构、形貌表征及电化学性能测试。结果表明,制备的Li_4Ti_(4.9)Ni_(0.1)O_(12)材料无杂相,颗粒大小均匀,在0.5 C下首次放电比容量为173.3 mA×h/g,库伦效率为97.4%,50次循环后,材料的放电比容量为163.4 mA×h/g,容量保持率为94.3%。     

Li3 PS4硫化物固态电解质制备及其电化学性能研究

采用高能球磨法制备出Li3 PS4玻璃陶瓷硫化物固态电解质,对制备出的Li3 PS4玻璃陶瓷硫化物固态电解质进行晶型结构和电化学性能测试,离子电导率达到10-3 S/cm.通过循环伏安测试,电化学窗口大于6 V,具有良好的电化学稳定性.     

稻壳灰为硅源制备硅酸锂及其吸附性能研究

利用农业废弃物稻壳灰作为硅源在一定工艺下合成硅酸锂材料。对Li_4SiO_4材料的组成结构以及物相形貌进行的观察分析,对影响Li_4SiO_4制备的时间、温度等因素进行了探究,并对其吸附性进行了有效的研究。试验结果表明,要制备出纯度较高、结晶度较好、颗粒尺寸合适的Li_4SiO_4材料,可通过硅源为稻壳灰,锂源为Li_2CO_3,在高于700℃的温度下煅烧,保温时间大于4 h,而在此条件下制备的Li_4SiO_4材料具有良好的CO_2吸附性能。     

羟基磷灰石陶瓷微球的制备研究

羟基磷灰石陶瓷微球的流动性好、容易填充,近年来在骨修复,尤其是口腔手术中得到较多应用。以HA-(NaPO3)6-Mg(H2PO4)2-明胶为陶瓷浆料,应用液滴-冷凝法对羟基磷灰石陶瓷微球的制备工艺进行了探索研究,获得了球形度好、粒径均一的陶瓷微球。     

SiO_2/TiO_2复合纳米粒子的可控制备及表征

以聚丙烯酸(PAA)为模板,采用正硅酸乙酯(TEOS)水解法制备了SiO_2微球,在体系中加入钛酸四丁酯(TBOT),水解后在SiO_2表面自组装一层TiO_2,煅烧产物获得SiO_2@TiO_2空心球;通过TEM、XRD、固体紫外分光光度计对SiO_2@TiO_2的粒子形貌尺寸、晶型、紫外吸收特性等进行表征。结果表明,900℃下煅烧的SiO_2@TiO_2紫外屏蔽效果最好。为抑制TiO_2的光催化活性,在SiO_2@TiO_2表面再包覆一层SiO_2,得到SiO_2@TiO_2@SiO_2微球,具有抗紫外线、防沉降、对皮肤友好等优点。包覆之后的SiO_2@TiO_2@SiO_2三层结构仍具有良好的紫外屏蔽效果。     

Preparation of tritium breeding Li2TiO3 ceramic pebbles via newly developed piezoelectric micro-droplet jetting

Wet methods as an emerging technique for the preparation of millimeter-sized tritium breeding ceramic pebbles, but the imposed air pressure as the driving forces to extrude slurry droplets are fluctuating during the reciprocating extrusion process, which caused a slight inconsistency in pebble sizes. In this study, a piezoelectric micro-droplet jetting approach was proposed by introducing a piezo-driven valve and modifying the slurry barrel mechanism to realize the air pressure invariable. A self-developed piezoelectric micro-droplet jetting device was successfully utilized to prepare Li₂TiO₃ green pebbles with coefficients of variation being lower than 2.7%. The size of the green pebbles could be precisely controlled in the range of 0.88–1.37 mm by manipulating the nozzle diameter, the air pressure, and the jetting time. The pebbles sintered at 1000°C for 3 h possessed a small grain size of ∼5.9 μm, a satisfied relative density of ∼84.8% T.D., and a high crush load of ∼25.7 N, implying the prepared pebbles could be used as a promising solid tritium breeding material in fusion reactors. These findings are anticipated to provide new opportunities for the highly efficient preparation of size-controllable tritium breeding ceramic pebbles.     

Long-term thermal stability of Li4TiO4–Li2TiO3 core–shell breeding pebbles under continuous heating in H2/Ar atmosphere

The long-term thermal stability of tritium breeding materials during service is a key factor to ensure efficient tritium release. In this study, the long-term thermal stability of advanced Li₄TiO₄–Li₂TiO₃ core–shell breeding pebbles under continuous heating in 1%H₂/Ar at 900°C was investigated for the first time. The results show that this core–shell material loses 3.4% Li mass after heating for 30 days, resulting in a reduction in Li density to .415 g/cm³, which is still significantly higher than other breeding materials. The moisture in the sample bed will determine the form of Li volatilization and thus affect the rate of Li mass loss. The core–shell pebbles maintain favorable phase stability during long-term heating, and the grain sizes of the Li₂TO₃ shell and Li₄TiO₄ core after 30 days of heating are 6.5 ± 1.5 and 6.9 ± 2.5 μm, respectively. Moreover, the samples did not crack or collapse during long-term heating and still had a satisfactory crushing strength of 37.61 ± 7.13 N after 30 days of heating. Overall, the high Li density and good thermal stability during long-term heating demonstrate that the Li₄TiO₄–Li₂TiO₃ core–shell breeding pebbles are a very reliable tritium breeding material for long-term service under harsh operating conditions.     

High‐Speed Camera‐Based Analysis of the Lithium Ceramic Pebble Fabrication Process

Lithium ceramic pebbles are a main component of the tritium breeding blanket in a future thermonuclear fusion plant. The melt‐based fabrication of the pebbles using the Plateau–Rayleigh instability emerged to be a promising approach in past investigations. However, the influence of process parameter variations on the pebble fabrication process is not yet well understood. Here, a new high‐speed camera‐based method to analyze the melt jet and the droplets directly in their formation phase is presented. Via special image processing algorithms, various individual properties such as dynamic changes, velocities, or agglomerations of the droplets are extracted. This new high‐speed camera‐based method provides additional information on the process state during the fabrication process. It is therefore an essential part in adapting and improving process parameters with respect to an overall enhanced product quality.     

Comparison of the microwave and conventional sintering of Li2TiO3 ceramic pebbles

Microwave sintering was employed in the fabrication of Li₂TiO₃ ceramic pebbles using the powders synthesized via hydrothermal method. The as-prepared Li₂TiO₃ powders exhibited high reactivity with an average particle size as small as 40?nm. A comparative study between the microwave and conventional sintering behavior of Li₂TiO₃ pebbles was systematically investigated. The microstructure and density analyses showed that the presence of microwaves accelerated the densification and grain growth, thus decreasing the sintering temperature. Besides, an accelerated phase transformation from α-Li₂TiO₃ to β-Li₂TiO₃ was observed in microwave processing. The Li₂TiO₃ ceramic pebbles obtained by microwave sintering exhibited high density, good mechanical property and uniform microstructure, which might hold good potential as tritium breeding materials for blankets. The results showed that the microwave sintering was a promising process for the fabrication of Li₂TiO₃ pebbles.     

A comparative study on the properties of Li2TiO3 powders and pebbles fabricated by different routes

Lithium titanate (Li₂TiO₃) is one of the promising candidate breeders for tritium self-sufficiency of deuterium(D)-tritium(T) fusion reaction. The differences in powder synthesis methods have a great impact on the properties of Li₂TiO₃ powders and the performance of Li₂TiO₃ ceramic pebbles. In this study, the Li₂TiO₃ powders were successfully synthesized by hydrothermal method and solid-state method, and then the pebbles were fabricated by the agar-based wet method. The mechanism of hydrothermal synthesis of Li₂TiO₃ powder was discussed. For the hydrothermal method, the Li₂TiO₃ powder with single phase can be obtained when the rate of Li/Ti = 2.4, and the powder presented two different morphology, which involved two reaction mechanisms, including in-situ phase transformation mechanism and dissolution-precipitation mechanism, the phase transformation from α-Li₂TiO₃ to β-Li₂TiO₃ accomplished at 400°C, which is lower than that of 750°C for solid-state method. Li₂TiO₃ pebbles prepared by the hydrothermal-wet method had a uniform pore distribution, an optimal grain size of 2.7 μm, a crushing load of 58.6 N, and relative density of 90.2%, respectively. In comparison, pebbles prepared by the solid-state-wet method also had better mechanical properties, which the crushing load and relative density were 53.9 N and 86.9% respectively under the optimal fabrication conditions.     

One-step fabrication of Li2TiO3 ceramic pebbles using pulsed YAG laser

A large amount of Li-containing ceramic breeder pebbles is packed in the solid breeding blanket of a nuclear fusion reactor. Several pebble fabrication technologies have been proposed in previous studies, including wet process, emulsion method, extrusion spheronization, additive manufacturing, and melt process. However, a simple, energy-effective, and scalable fabrication technology remains to be developed for the automated mass production and reprocessing of used radioactive pebbles post-operation. Selective laser melting potentially enables the quick and automated fabrication of breeder pebbles. Herein, we employ a high-power density pulse laser to produce ceramic breeder pebbles. A pulsed YAG laser was irradiated over a lithium metatitanate (Li₂TiO₃) powder bed in air, and the corresponding temperature was monitored using fiber-type infrared pyrometers. Spherical Li₂TiO₃ pebbles were successfully fabricated in a single step with an average diameter of 0.78 ± 0.13 μm and the sintering density of 87.4% ± 5.6% (input power: 7.9 J/pulse). The irradiated Li₂TiO₃ powder melted and turned spherical under surface tension and rapidly solidified, resulting in uniaxial fine grains and a decrease in the degree of long-range cation ordering.     

Fabrication of attractive Li4SiO4 pebbles with modified powders synthesized via surfactant-assisted hydrothermal method

Li₄SiO₄ pebbles have been widely studied as attractive tritium breeding materials in the fusion reactor blanket of international thermonuclear experimental reactor (ITER). In this work, surfactant-assisted hydrothermal method was first employed to prepare ultrafine ceramic powders for fabricating attractive Li₄SiO₄ pebbles. SEM analysis revealed that the introduction of sodium dodecyl sulfate could eliminate the particle aggregation to prepare monodispersed precursor powders, and thus generated the green bodies of pebble with homogeneous microstructure, which was helpful to eventually obtain high-quality Li₄SiO₄ pebbles. Moreover, the effects of sintering temperature on the grain size, relative density, and crush load of Li₄SiO₄ pebbles were also investigated. Li₄SiO₄ pebbles sintered at 700 °C had a high crush load (average value 27.39 N), small grain size (average value 0.57 μm), satisfactory density (88.13%T.D.) and abundant pore structure, which were expected to show favorable tritium release behavior as a promising tritium breeding material for fusion reactor blanket.     

Study on the chemical compatibility between Li2TiO3 ceramic pebbles and diverse advanced structural materials

The tritium breeder and structural materials are necessary components in the blanket to realize tritium (T) self-sustainment of nuclear fusion. The long-term exposure between tritium breeders and structural materials will cause surface corrosion in irradiation environments and then further affect the tritium release behavior. In this study, chemical compatibility between Li₂TiO₃ ceramic pebbles and advanced structural materials was studied systematically at 700 °C for 300 h under He+0.1 % H₂ environment, respectively. The color of the Li₂TiO₃ ceramic pebbles changes from white to dark grey and black. Moreover, the grain size of Li₂TiO₃ ceramic pebbles increases to more than 5 μm, and the crushing load decreased slightly. For the structural materials, the Al-rich oxide layer with about 188.7 nm of 14Cr-5Al oxide dispersion strengthened (ODS) steel and Cr-Fe rich oxide layer with about 1.04 μm of 14Cr-ODS steel were observed on the cross-section. The effective diffusion coefficient of O element in Li₂TiO₃ ceramic moved into ODS steel at 700 °C was calculated to be 3.3 × 10⁻¹⁶cm²/s and 1.02 × 10⁻¹⁴ cm²/s. Unfortunately, when SiC ceramics were contacted with the pebbles, the crystal phase transformed into SiO₂, which severely limits its application. Therefore, these results will provide guidance for the selection of structural materials in the future.     

Low-cost fabrication of Li2TiO3 tritium breeding ceramic pebbles via low-temperature solid-state precursor method

Lithium metatitanate (Li₂TiO₃) ceramic pebbles were fabricated from the powder synthesised via low-temperature solid-state precursor method. Solid H₂TiO₃ and LiOH·H₂O react chemically during ball milling process to form a nano-sized precursor powder. Pure β-Li₂TiO₃ powder can be obtained by calcining the precursor powder at 500 °C, which is half the temperature of conventional solid-state method. The synthesis process is simple and low-cost, which would be more available to achieve batch production among all feasible techniques. The low-temperature calcination will effectively avoid hard particle aggregates and poor sinterability caused by high-temperature heat treatment, which is conducive to prepare ceramics with good properties. The results show that the powder exhibits high sinterability with small particle size of 19 nm. The Li₂TiO₃ ceramic pebbles sintered at 800 °C have small grain size (470 nm), high relative density (83%) and good crush load (45 N), which has great potential as tritium breeding materials for fusion reactors.     

负极材料Li_4Ti_5O_(12)合成中优化原料组成的研究

以不同的钛源(锐钛矿型TiO2、金红石型TiO2和无定形TiO2)和不同的锂源(Li2CO3和LiOH.H2O),采用高温固相合成法合成Li4Ti5O12,并对Li4Ti5O12的合成工艺进行了优化。经试验发现,在900℃下以锐钛矿型TiO2和Li2CO3为原料合成的Li4Ti5O12具有良好的电化学性能,Li4Ti5O12材料在Li+嵌入和脱出的过程中,其晶型不发生变化。