Добірка наукової літератури з теми "High-pressure Techniques - Diamond Anvil Cell (DAC)"

The diamond anvil cell (DAC) is considered one of the dominant devices to generate ultrahigh static pressure. The development of the DAC technique has enabled researchers to explore rich high-pressure science in the multimegabar pressure range. Here, we investigated the behavior of the DAC up to 400 GPa, which is the accepted pressure limit of a conventional DAC. By using a submicrometer synchrotron X-ray beam, double cuppings of the beveled diamond anvils were observed experimentally. Details of pressure loading, distribution, gasket-thickness variation, and diamond anvil deformation were studied to understand the generation of ultrahigh pressures, which may improve the conventional DAC techniques.

The externally heated diamond anvil cell (EHDAC) conducts high pressure and temperature experiments with spatial uniformity and temporal stability. These are conventionally combined with various spectroscopies and x-ray diffraction measurements. EHDAC techniques perform Joule heating on a heater placed close to or directly in contact with diamond anvils. However, the electrical wiring and heater required for Joule heating complicate EHDAC setups, hindering easy access for the measurement of physical properties. This study proposes an EHDAC technique using laser- instead of Joule-heating. We successfully achieved temperatures reaching 900 K by applying heat to diamond anvils through laser-heating of the gaskets with thermally insulating anvil seats. To test this setup, we measured the melting temperature of H2O ice VII, which was consistent with previous studies. We also measured the high-pressure and temperature impedance of H2O VII and verified the capability of electrical resistivity measurements in this setup. This technique allows various physical property measurements owing to its simple setup required for externally laser-heated diamond anvil cell experiments. The unique characteristics of this heating technique are that (1) no heaters or wiring are required, (2) it exhibits the most efficient heating among EHDAC studies, (3) it maintains the DAC body at room temperature, and (4) diamond anvils do not detach from anvil seats after the EHDAC experiment. This method significantly simplifies the experimental setup, which allows much easier access to various physical property measurements using an EHDAC.

Techniques of producing ultra-high pressure at very low temperature and measuring method of electrical resistance and magnetization of samples confirmed in the used diamond anvil ceil (DAC) are shortly described. Experimental results on simple molecular systems such as iodine, sulfur, oxygen and organic iodanil are reviewed as typical example of pressure induced superconductivity.

The diamond-anvil cell (DAC) was invented 60 years ago, ushering in a new era for material sciences, extending research into the dimension of pressure. Most structural determinations and chemical research have been conducted at ambient pressure, i.e. the atmospheric pressure on Earth. However, modern experimental techniques are capable of generating pressure and temperature higher than those at the centre of Earth. Such extreme conditions can be used for obtaining unprecedented chemical compounds, but, most importantly, all fundamental phenomena can be viewed and understood from a broader perspective. This knowledge, in turn, is necessary for designing new generations of materials and applications, for example in the pharmaceutical industry or for obtaining super-hard materials. The high-pressure chambers in the DAC are already used for a considerable variety of experiments, such as chemical reactions, crystallizations, measurements of electric, dielectric and magnetic properties, transformations of biological materials as well as experiments on living tissue. Undoubtedly, more applications involving elevated pressure will follow. High-pressure methods become increasingly attractive, because they can reduce the sample volume and compress the intermolecular contacts to values unattainable by other methods, many times stronger than at low temperature. The compressed materials reveal new information about intermolecular interactions and new phases of single- and multi-component compounds can be obtained. At the same time, high-pressure techniques, and particularly those of X-ray diffraction using the DAC, have been considerably improved and many innovative developments implemented. Increasingly more equipment of in-house laboratories, as well as the instrumentation of beamlines at synchrotrons and thermal neutron sources are dedicated to high-pressure research.

Tuning the energy density of matter at high pressures gives rise to exotic and often unprecedented properties, e.g., structural transitions, insulator–metal transitions, valence fluctuations, topological order, and the emergence of superconductivity. The study of specific heat has long been used to characterize these kinds of transitions, but their application to the diamond anvil cell (DAC) environment has proved challenging. Limited work has been done on the measurement of specific heat within DACs, in part due to the difficult experimental setup. To this end, we have developed a novel method for the measurement of specific heat within a DAC that is independent of the DAC design and is, therefore, readily compatible with any DACs already performing high pressure resistance measurements. As a proof-of-concept, specific heat measurements of the MgB2 superconductor were performed, showing a clear anomaly at the transition temperature ( T c), indicative of bulk superconductivity. This technique allows for specific heat measurements at higher pressures than previously possible.

Experimental results in search for pressure-induced superconductivity are reviewed. Typical examples are simple inorganic and organic molecular crystals, magnetic metals, and elements. We have developed complex extreme condition of very low temperature down to 30 mK and ultra high pressure exceeding 200 GPa by assembling compact diamond-anvil cell (DAC) on a powerful 3 He /4 He dilution refrigerator. Using the newly developed apparatus and techniques, we have studied superconductivity in various materials in various pressure range. In this paper, we will shortly review our newly developed experimental apparatus and techniques and discuss about examples of pressure-induced superconductivity in simple metals.

Vibrational spectroscopy is used in Earth science for both quantitative and qualitative analysis. This report focuses on infrared (IR) spectroscopy, although similar efforts are on-going in Raman spectroscopy.Qualitative studies utilize the fact that the vibrational spectrum is a characteristic of a material: hence comparison to a set of standards allows for identification of the phase. Most of these types of studies in Earth science involve macrosamples, but measurements of microsamples from meteorites are on interest in order to identify the structure of SiC inclusions and the type of organic compounds in interplanetary dust. As most of these samples are micron sized, which is below the diffraction limit for the mid-IR, the approach has been to compress the sample using a diamond anvil cell (DAC) into a disk of sub-micron thickness, adhere the sample to a KBr plate, and to subsequently remove the disk from the DAC and obtain spectra with the aid of an FTIR microscope.

AbstractUltrahigh-pressure and -temperature (P-T) experimental techniques have progressed rapidly in recent years. By combining them with X-ray diffraction measurements at synchrotron radiation facilities, it is now possible to examine deep Earth mineralogy in situ at relevant high P-T conditions in a laser-heated diamond anvil cell (DAC). The lowermost part of the mantle, known as the D″ layer, has long been enigmatic because of a number of unexplained seismological features. Nevertheless, the discovery of a phase transition from MgSiO3 perovskite to ‘post-perovskite’ above 120 GPa and 2400 K indicates that post-perovskite is a principal constituent in the lowermost mantle, which is compatible with seismic observations. The ultrahigh P-T conditions of the Earth’s core have not been accessible by static experiments, but the structure and phase transition of Fe and Fe-alloys are now being examined up to 400 GPa and 6000 K by laser-heated DAC studies.

The phase diagrams of Na 2 CO 3 and K 2 CO 3 have been determined with multianvil (MA) and diamond anvil cell (DAC) techniques. In MA experiments with heating, γ -Na 2 CO 3 is stable up to 12 GPa and above this pressure transforms to P 6 3 /mcm-phase. At 26 GPa, Na 2 CO 3 - P 6 3 /mcm transforms to the new phase with a diffraction pattern similar to that of the theoretically predicted Na 2 CO 3 - P 2 1 /m. On cold compression in DAC experiments, γ -Na 2 CO 3 is stable up to the maximum pressure reached of 25 GPa. K 2 CO 3 shows a more complex sequence of phase transitions. Unlike γ Na 2 CO 3 , γ -K 2 CO 3 has a narrow stability field. At 3 GPa, K 2 CO 3 presents in the form of the new phase, called K 2 CO 3 -III, which transforms into another new phase, K 2 CO 3 -IV, above 9 GPa. In the pressure range of 9–15 GPa, another new phase or the mixture of phases III and IV is observed. The diffraction pattern of K 2 CO 3 -IV has similarities with that of the theoretically predicted K 2 CO 3 - P 2 1 /m and most of the diffraction peaks can be indexed with this structure. Water has a dramatic effect on the phase transitions of K 2 CO 3 . Reconstruction of the diffraction pattern of γ -K 2 CO 3 is observed at pressures of 0.5–3.1 GPa if the DAC is loaded on the air.

Due to its exceptional mechanical and electrical properties, graphene (one layer sheet of carbon atoms) has attracted a lot of attention since its discovery in 2004. The purpose of this research is to compare the Raman spectra of graphene with plasma treated graphene sheets which have been treated by changing the different parameters affecting the plasma treatment like gas flow, power and pressure and treatment time. The graphene we used for our high pressure studies are 4-5 layer CVD deposited graphene samples prepared by our collaborators in Dr. W. B. Choi’s group. First we report a Raman spectroscopy study of graphene on copper substrate at high pressures. Diamond anvil cell (DAC) was used to generate pressure. In situ Raman spectra were collected at pressures up to 10 GPa. The results indicate that the G band of graphene shifts with pressure significantly (about 5 cm-1/GPa) whereas the 2D band changes very little. The plasma treated samples were loaded into DAC. Raman spectrum was captured. Parts of the spectrum which were not related to the grapheme peak position were eliminated. The background was reduced. Peaks were found and fitted using FITYK software and the shift of each peak compared to its last position was observed when the pressure was increased. Next we studied plasma treated graphene samples treated with different partial pressure treatments under high pressure and compared them to each other using zirconia anvil cell with the same method.

This thesis presents experimental as well as theoretical studies on several contemporary systems like quantum spin liquids (QSLs), skyrmion lattices, and transition metal dichalcogenides (TMDs) under extreme conditions like low temperature (down to 4K) and ultra high pressures (up to 26 GPa). Temperature-dependent Raman studies are carried out to investigate Raman signatures of Kitaev quantum spin liquid (QSL) state of Cu2IrO3 and Ag3LiIr2O6 and orbital ordering in Heisenberg quantum magnet Ca10Cr7O28. High-pressure studies are performed on Kitaev QSL candidates -RuCl3, Cu2IrO3, kagomé QSL ZnCu3(OH)6Cl2, skyrmion lattice system Cu2OSeO3, and TMD candidate VSe2. Structural and vibrational evolutions of these systems under pressure are probed by X-ray diffraction measurements using synchrotron source and Raman scattering, respectively.

Niniejsza rozprawa doktorska opisuje badania związków srebra wykonane metodami spektroskopowymi. Główny nacisk został położony na związki srebra dwuwartościowego: fluorek srebra(II) AgF2, siarczan(VI) srebra(II) wraz ze swoim monohydratem, tetrafluoroboran fluorosrebra(II) (AgF)BF4, fluorosrebrzan(II) cezu CsAgF3, rubidu RbAgF3, oraz wysokotemperaturowa forma fluorosrebrzanu(II) potasu, HT-KAgF3 Ponadto zbadane zostały inne związki srebra: fluorek srebra(I) oraz tlenek srebra(I,III) AgO. Wszystkie związki zostały zbadane za pomocą spektroskopii fourierowskiej w zakresie dalekiej podczerwieni. Część związków zbadana została za pomocą spektroskopii ramanowskiej, spektroskopii absorpcyjnej w zakresie średniej i bliskiej podczerwieni, jak również za pomocą spektroskopii elektronowej z zakresu światła widzialnego i ultrafioletu oraz za pomocą nieelastycznego rozpraszania neutronów. Trzy związki, AgO, AgF i AgF2 zostały zbadane metodą spektroskopii Ramana pod zwiększonym ciśnieniem. Głównym celem pracy było zrozumienie struktury oscylacyjnej badanych związków, jak też wniknięcie w naturę ich przemian strukturalnych pod wysokim ciśnieniem (dla wybranych układów). Drugim celem było oszacowanie stałej nadwymiany magnetycznej dla dwuwymiarowego AgF2 z użyciem spektroskopii Ramana, a dla jednowymiarowego AgFBF4 z użyciem spektroskopii absorpcyjnej w zakresie NIR. Celem ubocznym, który wyniknął w trakcie prowadzenia prac badawczych, było zrozumienie rozkładu fotochemicznego AgF2 i AgSO4. Badania nad fluorkiem srebra(I) pod wysokim ciśnieniem wykazały obecność większej liczby pasm ramanowskich niż przewidywana z obliczeń teorii grup (brak pasm); część z nich prawodpodobnie pochodzi od centrów barwnych lub od nadtonu aktywnego w podczerwieni drgania normalnego T1u. Badania nad fluorkiem srebra(II) wykazały jego wysoką fotoczułość. Produkt indukowanego światłem laserowym fotorozkładu został zbadany w zakresie od ciśnienia atmosferycznego do 47 GPa. Wydaje się, ze rozkład fotochemiczny prowadzi do pochodnej zawierającej aniony Ag(II)F42–, zapewne Ag(I)2Ag(II)F4, który jest pierwszym znanym fluorkiem srebra o mieszanej wartościowości Ag(I)/Ag(II). Wyznaczono zależność ciśnieniową charakterystycznego pasma ramanowskiego tej nowej fazy do ciśnienia 47 GPa. Ponadto dzięki zastosowaniu spektroskopii rozproszenia ramanowskiego oraz nieelastycznego rozpraszania neutronów z powodzeniem zidentyfikowano i zarejestrowano po raz pierwszy przejścia bimagnonowe w dwuwymiarowym antyferromagnetyku, AgF2, i wyznaczono wartość wewnątrzwarstwowej stałej nadwymiany magnetycznej, J, dla tego związku. Duża wartość J=70 meV plasuje ten związek jako jedyny, poza warstwowymi tlenkami miedzi(II), wykazujący tak silną nadwymianę magnetyczną w dwóch wymiarach. Fluoroboran fluorosrebra(II) został scharakteryzowany za pomocą spektroskopii rozproszenia ramanowskiego, nieelastycznego rozproszenia neutronów, spektroskopii fourierowskiej w podczerwieni oraz spektroskopii odbiciowej w zakresie średniej podczerwieni. Charakterystyczne pasmo absorpcyjne w zakresie bliskiej podczerwieni pozwolilo na oszacowanie wewnątrzłańcuchowej stałej nadwymiany magnetycznej dla tego związku na około 270 meV, co przekracza najwyższą znaną do tej pory wartość zmierzoną dla Sr2CuO3 (240 meV). Badania nad tlenkiem srebra(I,III) prowadzone w zakresie wysokich ciśnień wykazały brak indukowanego ciśnieniem rozkładu lub komproporcjonacji tego związku do nie mniej niż 74 GPa. Ponadto, z uwagi na dobrą zgodność pozycji pasm ramanowskich z obliczeniami teoretycznymi dokonanymi na modelach wysokociśnieniowych faz AgO udało się wykazać istnienie dwóch strukturalnych przejść fazowych w przedziale ciśnienia od 0 do 74 GPa. W trakcie badań przeprowadzonych na trzech fluorosrebrzanach(II) metali alkalicznych: HT-KAgF3, CsAgF3 i RbAgF3 wykazano bardzo duże podobieństwo widm spektroskopii fourierowskiej w zakresie dalekiej podczerwieni tych związków mimo wyraźnych różnic strukturalnych.
This doctoral dissertation describes research on silver compounds carried out with a range of spectroscopic methods. The main focus of the thesis was on divalent silver compounds: AgF2, AgSO4, AgSO4∙H2O, (AgF)BF4, CsAgF3, RbAgF3, and high-temperature form of KAgF3. In addition, other silver compounds were investigated, particularly AgF and silver(I, III) oxide AgO. All compounds were studied by FT-FIR spectroscopy, some were also investigated with Raman spectroscopy (at ambient or high pressure), MIR, NIR, as well as UV and visible absorption spectroscopy and by inelastic neutron scattering. The main scope of the work was to get insight into vibrational structure of the studied compounds as well as understand their pressure-induced phase transitions. The second goal was to determine magnetic superexchange constants for 2D AgF2 from Raman scattering spectra, and for 1D AgFBF4 from NIR-absorption spectra. The auxiliary task, dictated by the course of the experimental work, was to understand photochemical decomposition of AgF2 and AgSO4. The spectroscopic measurements of AgIISO4 prepared using the new electrosynthesis method in concentrated H2SO4 showed its similarity with the product of chemical synthesis developed earlier, albeit substantial differences in reactivity to water vapor were also found. In addition, the laser-induced decomposition of AgIISO4 was observed and it was shown that the decomposition product is dependent on the wavelength of the laser used. A similar photosensitivity was observed in AgIISO4∙H2O. The hydrate was also studied spectroscopically from far-infrared to UV, which allowed determination of the orbital splitting parameters as well as has provided the supplementary evidence for the presence of water molecules in its crystal structure. Research on AgF at high pressure showed the presence of several Raman bands in contrast with predictions of group theory (no Raman-active bands), some of them probably originating from color centers or overtone of the IR-active fundamental. Research on AgF2 proved its high photosensitivity to laser light. Laser-induced photodecomposition product has been studied in the range from atmospheric pressure up to 47 GPa. The decomposition product seems to contain Ag(II)F42– anion, notably Ag(I)2Ag(II)F4, which is the first mixed-valence Ag(I)/Ag(II) fluoride known. Pressure dependence of the characteristic Raman band for this phase was measured up to 47 GPa. In addition, using Raman scattering spectroscopy and inelastic neutron scattering, I have successfully identified and measured for the first time the bimagnon transitions in 2D antiferromagnet, AgF2, and determined the value of the intra-sheet magnetic superexchange constant, J. The large value of J=70 meV sets this compound second only to lamellar oxocuprates(II). (AgF)BF4 has been characterized by Raman scattering, inelastic neutron scattering, IR absorption and reflection spectroscopy. The characteristic band appearing in the NIR absorption spectra enabled estimation of the intra-chain magnetic superexchange constant for this compound to be about 270 meV. This value surpasses the largest known superexchange constant ever measured (240 meV for Sr2CuO3). Research on AgO conducted under a high pressure showed no pressure-induced decomposition or comproportionation of this compound to no less than 74 GPa. Due to the good agreement of the experimental Raman band positions with those derived from the theoretical calculations made on the AgO high-pressure models, it was possible to demonstrate the existence of two structural phase transitions in the pressure range from 0 to 74 GPa. The research carried out on three alkali metal fluoroargentates: CsAgF3, RbAgF3, and high-temperature form of KAgF3 has shown that despite clear structural differences between them, the Fourier transmission spectra in the far infrared range of all compounds show substantial similarity.

In order to grasp the possibility of evaluating shear properties for solidified lubricants under high pressure, plastic deformations of metal micro-spheres (about 0.07mm) in solidified lubricants were evaluated by employing a diamond-anvil pressure cell (DAC). Large deformations (2–5 times larger than the original sphere dimensions) were observed for CVT oil and ester oil up to 6 GPa at 23–25°C. Deformation starting pressure agreed with the solidified pressure. These deformations were caused by the non-hydrostatic pressure in the solidified lubricants. Shear stresses of the solidified lubricants were tentatively and roughly estimated from the plastic deformations of the spheres based on some assumptions. They almost agreed with the mean shear stress (traction force / hertzian contact area) from traction test.