Intercalation of hafnium oxide between epitaxially-grown monolayer graphene and Ir(111)substrate

Intercalation of insulating materials between epitaxial graphene and the metal substrates is highly demanded to restore the intrinsic properties of graphene,and thus essential for the graphene-based devices.Here we demonstrate a successful solution for the intercalation of hafnium oxide into the interface between full-layer graphene and Ir(111)substrate.We first intercalate hafnium atoms beneath the epitaxial graphene.The intercalation of the hafnium atoms leads to the variation of the graphene moire superstructure periodicity,which is characterized by low-energy electron diffraction(LEED)and lowtemperature scanning tunneling microscopy(LT-STM).Subsequently,we introduce oxygen into the interface,resulting in oxidization of the intercalated hafnium.STM and Raman's characterizations reveal that the intercalated hafnium oxide layer could effectively decouple the graphene from the metallic substrate,while the graphene maintains its high quality.Our work suggests a high-k dielectric layer has been successfully intercalated between high-quality epitaxial graphene and metal substrate,providing a platform for applications of large-scale,high-quality graphene for electronic devices.

Intensification of zirconium and hafnium separation through the hollow fiber renewal liquid membrane technique using synergistic mixture of TBP and Cyanex-272 as extractant

The novel synergistic mixture of TBP and Cyanex-272 is used as the extractant in the hollow fiber renewal liquid membrane(HFRLM) technique for Zr/Hf separation.The effects of the chemical and operational parameters such as HNO3 concentration in the donor phase,NH4 F concentration in the acceptor phase,Cyanex-272 and TBP concentration in the liquid membrane phase,the lumen and shell side flow rates,and aqueous/organic volume ratio on the mass transfer and separation performance of HFRLM method were investigated.The obtained results reveal the intensification potential of proposed HFRLM technique for selective extraction of Zr over Hf with separation factor higher than 100.The HFRLM method provides two times higher mass transfer flux in comparison with hollow fiber supported liquid membrane(HFSLM).Also,the HFRLM method shows satisfactory stability for 700 min of continuous operation.The Zr ion transport through the LM phase follows the coupled co-transport mechanism and the diffusion in the renewal layer is recognized as the rate-controlling step in the HFRLM process.Moreover,the Zr mass transfer coefficient and molar flux in the HFRLM method are calculated in the range of 1×10^-8 to 8.4×10^-7 m·s^-1 and 4.9×10^-6 to 20.1×10^-6 mol·m^-2·s^-1,respectively.

Separation of hafnium from zirconium in hydrochloric acid solution with di(2-ethylhexyl)phosphoric acid by solvent extraction

The preparation of nuclear-grade zirconium and hafnium is very important for nuclear power. The separation of hafnium from zirconium in a hydrochloric acid solution by solvent extraction was investigated with di(2-ethylhexyl)phosphoric acid(D2 EHPA). The effects of hydrochloric acid concentration, extractant concentration,diluents, and temperature on the distribution coefficient of hafnium and zirconium were studied. The species extracted were ZrOA_2·2 HA and HfOA_2-2 HA. In this process, the separation factors varied with different diluents and followed the order octane > hexane > toluene > chloroform.A high separation factor value of 4.16 was obtained under the conditions of a solution containing 0.05 mol/L HCl and0.01 mol/L D2 EHPA for the separation of hafnium from zirconium. The extraction reaction was endothermic.

Study of Zirconium and Hafnium Separation by Solvent Extraction Technique from Nitric and Hydrochloric Solutions with Acid, Basic and Neutral Extractants

This paper describes the study of the extraction of Zr and Hf in nitric and hydrochloric media by solvent extraction technique using different types of extractants. The effect of the extractants DEHPA, IONQUEST?801 and CYANEX?272, TBP, CYANEX?923, PRIMENE?JTM, ALAMINE?336 and ALIQUAT?336 was investigated. For acid extractants in both nitric and hydrochloric media, a high degree of extraction was observed, although they had low selectivity in separating the metals. For the acid extractants also, it was not possible to strip the metals from the organic phase through acid solutions. In this case, a stripping solution with very high acidity would be required, and this is not viable. When the basic extractants were used, no metal extraction was observed under the conditions investigated, indicating no extractable anionic species in either media. The optimum zirconium/hafnium separation was achieved using an acidity of 7.0 mol?L?1, nitrate concentration of 9.2 mol?L?1 and 1.5 mol?L?1 of TBP. In these conditions, a separation factor of 12.6 was obtained.

Simultaneous Determination of Zirconium and Hafnium by Dual System and Dual Wavelength Spectrophotometry

A dual system and dual wavelength spectrophotometry（DSDWS）used to simultaneously determine Zrand Hf were proposed.《Zr（Hf）-xO-CTMAB》and《Zr（Hf）-CAB-CDMAA-Triton X-100》were chosenas a pair of chromophoric systems.The difference of chromophoric behaviours between Zr and Hf is in-creased by the addition of hydrogen peroxide as masking agent and by adjustment of acidity.The apparentmolar absorptivities of Zr and Hf are 2.0×105 and 5.0×104 L·mol-1·cm-1respectively.The proce-dure is simple and rapid.

Measurement of L_Ⅲ Subshell Absorption Jump Parameters of Hafnium

The L_Ⅲ subshell absorption jump ratio and jump factor of hafnium have been measured using two different ways which are X-ray attenuation method and Energy Dispersive X-ray Fluorescence technique.The results obtained both ways have been compared with theoretical values.They are in good agreement with each other.

High-pressure elastic anisotropy and superconductivity of hafnium:A first-principles calculation

The elastic anisotropy and superconductivity upon hydrostatic compression ofα,ω,and β Hf are investigated using first-principle methods.The results of elastic anisotropies show that they increase with increasing pressure for α and ω phases,while decrease upon compression forβphase.The calculated superconducting transition temperatures are in excellent agreement with experiments.Electron-phonon coupling constants(λ)are increasing with pressure for α and ω phases,while decreasing for β phase.For β phase,the large values ofλare mainly due to the obvious TA1 soft mode.Under further compression,the TA1 soft vibrational mode will disappear gradually.

First principles study of hafnium intercalation between graphene and Ir(111)substrate

The intercalation of heteroatoms between graphene and metal substrates is a promising method for integrating epitaxial graphene with functional materials.Various elements and their oxides have been successfully intercalated into graphene/metal interfaces to form graphene-based heterostructures,showing potential applications in electronic devices.Here we theoretically investigate the hafnium intercalation between graphene and Ir(111).It is found that the penetration barrier of Hf atom is significantly large due to its large atomic radius,which suggests that hafnium intercalation should be carried out with low deposition doses of Hf atoms and high annealing temperatures.Our results show the different intercalation behaviors of a large-size atom and provide guidance for the integration of graphene and hafnium oxide in device applications.

Rapid label-free SERS detection of foodborne pathogenic bacteria based on hafnium ditelluride-Au nanocomposites

Two-dimensional(2D)nanomaterials have captured an increasing attention in biophotonics owing to their excellent optical features.Herein,2D hafnium ditelluride(HfTe_(2)),a new member of transition metal tellurides,is exploited to support gold nanoparticles fabricating HfTe_(2)-Au nanocomposites.The nanohybrids can serve as novel 2D surface-enhanced Raman scattering(SERS)substrate for the label-free detection of analyte with high sensitivity and reproducibility.Chemical mechanism originated from HfTe_(2) nanosheets and the electromagnetic enhancement induced by the hot spots on the nano-hybrids may largely contribute to the superior SERS effect of HfTe_(2)-Au nanocomposites.Finally,HfTe_(2)-Au nanocomposites are utilized for the label-free SERS analysis of foodborne pathogenic bac-teria,which realize the rapid and ultrasensitive Raman test of Escherichia coli,Listeria mono-cytogenes,Staphylococcus aureus and Salmonella with the limit of detection of 10 CFU/mL and the maximum Raman enhancement factor up to 1.7×10^(8).Combined with principal component analysis,HfTe_(2)-Au-based SERS analysis also completes the bacterial classification without extra treatment.

Nanometer Thick Diffused Hafnium and Titanium Oxide Light Sensing Film Structures

We examine 10 nm thick film structures containing either Hf or Ti sandwiched between two respective oxide layers. The layers are deposited onto heated substrates to create a diffusion region. We observe a high degree of light sensitivity of the electric current through the film thickness for one polarity of an applied voltage. For the other polarity, the current is not affected by the light. We explain the observed phenomenology using the single-particle model based on the existence of interface states on the metal-oxide interfaces.

Equilibrium and kinetic data of adsorption and separation for zirconium and hafnium onto MIBK extraction resin

The equilibrium and kinetics of methyl isobutyl ketone(MIBK) extraction resin for adsorption and separation of zirconium and hafnium were studied under the different conditions of acidity,initial total concentrations of zirconium and hafnium and temperature.The equilibrium data of both zirconium and hafnium are found to follow the Freundlich adsorption isotherm,and the Freundlich isotherm constants(KF) are 3.53 and 0.64 mg/g,respectively.The equilibrium data of zirconium also fit the Langmuir adsorption isotherm,and the saturation adsorption capacity(Qmax) and the Langmuir isotherm constant(KL)are 75.93 mg/g and-0.012 7 L/g,respectively.The obtained kinetic data of both zirconium and hafnium are found to fit the HO pseudo-second-order kinetic model,and the rate constants of pseudo-second-order equation(k2) are-0.019 and 0.41 g/(mg·min),respectively.Column tests show that the MIBK extraction resin could be used as efficient adsorbent material for separating hafnium from zirconium.

Effect of hafnium addition on solidification structure of cast Ti-46Al alloys

To investigate the effect of hafnium addition on the solidif ication structure, Ti-46Al alloys with nominal compositions of Ti-46Al-xHf (x = 0, 3, 5, 7) (at.%) were arc-melted into small ingots in an argon atmosphere. The characteristics of the macrostructures and microstructures were studied using a linear intercept method, OM, SEM (BSE), XRD and TEM. The results showed that the ingots with Hf have near lamellar microstructure in columnar and dendrite morphology. The hafnium concentration has a strong effect on the columnar spacing refi nement. Increasing Hf from 0 to 7 (at.%), the columnar spacing can be reduced from～1000 to～400 μm. Constitute phases of the ingots are α2, a small amount of B2 and c. Most of the B2 phases, richer in Hf and leaner in Al and Ti, exist on the node of the dendrite core in block shape and a little across the lamellar colonies in stick shape. The c phases exist on the boundaries of lamellar colonies in small cellular shape. There also exists a segregation of Hf on the columnar and dendrite core. Particularly, both the α- and β-phase form from the melt as prior phases. The possible phase sequencing during solidif ication and solid-state transformations with Hf is given in this paper.

Low-temperature Rapid Synthesis of Ultrafine Hafnium Carbide Ceramic Powders

Nano hafnium carbide(HfC) powders were synthesized by sol-gel combining hightemperature rapid heat treatment process using citric acid and hafnium tetrachloride as the raw materials. The effects of ball milling treatment on the phase and morphology of pyrolysis products(HfO_2-C) and final HfC product were investigated and the influences of heat treatment temperature and holding time on the structure and properties of the synthesized hafnium carbide powders were also studied. The experimental results showed that the HfO_2-C powders with good uniformity and small particle size were prepared by controlling the milling time. Pure HfC powders with an average particle size of 500 nm were obtained at 1 700 ℃ with a holding time of 3 min, and the oxygen content was about 0.69 wt%, lower than that of the hafnium carbide powders prepared by SPS(0.97%).

氧化铪基铁电薄膜相结构调控的研究进展

随着微电子技术的发展,氧化铪(HfO2)因具有与Si基半导体工艺相兼容、适宜的相对介电常数、良好的热稳定性和化学稳定性以及较大的禁带宽度等优点,成为当前新型铁电材料的研究焦点.HfO2是一种典型的“相结构决定性能,性能决定应用”的材料,其铁电性能源于薄膜中存在空间点群为Pca21的非中心对称的正交相.因此,实现HfO2薄膜铁电性能稳定与提升的前提是调控HfO2薄膜于亚稳正交相结构.以正交相的调控机理为出发点,综述了HfO2正交相的稳定因素,并分别从薄膜厚度、掺杂元素、退火工艺、晶粒取向和电极材料等方面进行归纳,例如HfO2材料的正交相含量随薄膜厚度的增加而降低;适宜含量的元素掺杂可以稳定HfO2材料的正交相;高的升温速率,极短的退火时间可抑制单斜相的形成;制备具有特定取向的正交相薄膜以及顶部电极的夹持作用都是保证HfO2材料正交相稳定的重要因素.最后,对HfO2薄膜未来发展做出展望.

复合添加Ni和Hf元素对沉淀强化Co-Al-W高温合金组织和力学性能的影响

研究了Ni和Hf元素对Co-Al-W合金的组织结构的影响,并进行900℃高温压缩试验,测量屈服强度和极限强度。试验结果证明:Hf元素含量为0.5%时,合金主要为γ相和γ′相的两相结构;当Hf元素为1%时,10Ni1Hf合金中出现了Co_(23)Hf_(6)相、20Ni1Hf和30Ni1Hf,40Ni1Hf合金中出现了Co_(23)Hf_(6)相和Co_(2)Hf相。900℃的压缩试验表明,随着Ni元素的增加,合金的屈服强度和极限强度都呈现为先增大后减小的趋势。随着Hf元素增加到1%,10Ni、20Ni合金极限强度和屈服强度均增大,40Ni合金的极限强度和屈服强度均最小,20Ni1Hf合金的屈服强度和抗拉强度均为最大值。因此合金中添加少量的Hf对力学性能是有利的,当Hf含量为1%时导致富Hf有害相的产生。添加一定量的Ni可以提高合金的力学性能,但不能超过20%,过多反而降低其高温强度。

电感耦合等离子体质谱(ICP-MS)法测定锆钛矿中的铪

锆钛矿中存在耐高温的锆、钛化合物,铪以类质同象进入锆矿物中,准确测定锆钛矿中的铪对选矿研究、矿物综合利用及工业生产有重要作用。通过考察锆钛矿成分及熔融方法,以碳酸钠-硼砂高温熔融锆钛矿,以178 Hf为分析同位素及185 Re为内标,使用电感耦合等离子体质谱法测定锆钛矿中含量不均的铪。结果表明,碳酸钠-硼砂高温熔融效果最好,可完全溶解耐高温难分解的锆钛矿,当碳酸钠-硼砂质量配比为2∶1时熔融效果最佳。ICP-MS蠕动泵转速为45 r/min、雾化气流量为1.06 L/min时雾化效率最优。在选定的实验条件下,HfO_(2)质谱强度与质量浓度在0.01~250 ng/mL呈良好的线性关系,相关系数为0.9997,背景等效浓度为0.029 ng/mL,方法检出限为0.0032 ng/mL。按实验方法对中国国家标准物质中的HfO_(2)进行测定,测定值与认定值一致,相对标准偏差在1.6%~3.2%。按实验方法对锆钛矿样品中的HfO_(2)进行测定并进行加标回收实验,测定结果的相对标准偏差(RSD,n=9)为0.90%~3.4%,加标回收率在96.0%~106%,满足国家地质矿产行业标准DZ/T 0130—2006的要求。

铪钛酸钡陶瓷制备及其压电性能的微观机制研究

采用传统固相反应法制备系列BaHf_(x)Ti_(1-x)O_(3)陶瓷,通过对陶瓷的压电、铁电、相组成、晶粒尺寸的测试和分析,发现:所有BaHf_(x)Ti_(1-x)O_(3)陶瓷样品均具有纯钙钛矿结构,室温均为铁电体具有压电性;在x<0.1时室温压电系数为195~327p C/N,x=0.02时,压电系数、剩余极化强度和平均晶粒尺寸最大,分别为327pC/N,13.3μC/cm^(2)和37.2μm,大晶粒尺寸和四方-正交-三方多相共存是其具有大压电系数的主要原因。

Technological conditions for purification of hafnium by iodide process

In nuclear industry,the purity of hafnium control rod is usually significant,and the process parameters will affect the impurity contents.In this study,the four key factors(filament temperature,retort materials,feeds,and iodide reaction time)were investigated.It is found that the impurity contents of Fe,Ni in the hafnium crystal bar decrease with the K value rising.Both the retort materials and feed types have obvious influence on the impurity contents of hafnium crystal bar.The iodide reaction time has little effect on the impurity contents of hafnium crystal bar.

测定地质样品中铌、钽、铪、锆不同分析方法的比较

研究了不同酸溶、碱融测定地质样品中铌、钽、铪、锆的前处理方法,利用电感耦合等离子体发射光谱法、电感耦合等离子体质谱法进行测定。选用不同种类地质样品标准物质进行了条件实验,并分析了敞口酸溶、密闭消解、碱融三种不同分析方法的优劣点,供不同实验条件的实验室进行选择。采用硝酸-氢氟酸-过氧化氢体系密闭消解酸溶ICP-MS检测的方法能很好地测定铌、钽、铪、锆,相对标准偏差(RSDn=12)小于4%,并应用于尼日利亚高山州ZURAK地区一批实际样品的分析检测,取得了较好的效果。