Ultra-low Expansion Research Articles

Space-confinement of MnO nanosheets in densely stacked graphene: Ultra-high volumetric capacity and rate performance for lithium-ion batteries

The requirements on volumetric and gravimetric performances of lithium-ion batteries have been more and more urgent for their applications in miniaturized consumer electronics. Herein, we report a simple synthesis strategy of densely stacked graphene/MnO architecture anode for lithium-ion batteries. Through a simply modified Hummers method, the MnO2 nanofibers are homogeneously confined in-between the graphene oxide sheets, which can form a three-dimensional layered dense structure that can be easily reduced to densely stacked graphene/MnO architecture during annealing process. More importantly, the integration of MnO nanosheets and graphene sheets with dense architecture is beneficial for the enhanced electron/ion transfer kinetics, and the improved structural and interfacial stability during charge-discharge process. As a result, the graphene/MnO architecture electrode exhibits ultra-high gravimetric/volumetric capacities (1000mAhg−1/2288mAhcm−3 at 0.1Ag−1), excellent rate performance (270mAhg−1/618mAhcm−3 at 8.0Ag−1), ultra-low volume expansion (18%) and outstanding cycling stability (118% of capacity retention after 300 cycles).

Controlling Piezoelectric Responses in Pb(Zr0.52Ti0.48)O3 Films through Deposition Conditions and Nanosheet Buffer Layers on Glass.

Nanosheet Ca2Nb3O10 (CNOns) layers were deposited on ultralow expansion glass substrates by the Langmuir–Blodgett method to obtain preferential (001)-oriented growth of Pb(Zr0.52Ti0.48)O3 (PZT) thin films using pulsed laser deposition (PLD) to enhance the ferroelectric and piezoelectric properties of the films. The PLD deposition temperature and repetition frequency used for the deposition of the PZT films were found to play a key role in the precise control of the microstructure and therefore of the ferroelectric and piezoelectric properties. A film deposited at a high repetition frequency has a columnar grain structure, which helps to increase the longitudinal piezoelectric coefficient (d33f). An enhanced d33f value of 356 pm V–1 was obtained for 2-μm-thick PZT films on CNOns/glass substrates. This high value is ascribed to the preferential alignment of the crystalline [001] axis normal to the substrate surface and the open columnar structure. Large displacement actuators based on such PZT films grown on CNOns/glass substrates should be useful in smart X-ray optics applications.

Ultra-low thermal expansion realized in giant negative thermal expansion materials through self-compensation

Materials with zero thermal expansion (ZTE) or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE) materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn–Co–Ge–In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE owing to a martensitic magnetostructural transition. The major finding is that the thermal expansion behavior can be totally controlled by modulating the crystallinity degree and phase transition from atomic scale. Self-compensation effect leads to ultra-low thermal expansion with a linear expansion coefficient as small as +0.68 × 10−6/K over a wide temperature range around room temperature. The present study opens an avenue to reach ZTE particularly from the large class of giant NTE materials based on phase transition.

High pressure Raman spectroscopic study of low thermal expansion AZr2(PO4)3, A=K, Rb and Cs

AZr2(PO4)3 (A=K, Rb, Cs) are a set of flexible framework compounds that exhibit tunable ultralow thermal expansion over the wide temperature range of 293-1273 K. High pressure Raman spectroscopic measurements on AZr2(PO4)3 reveals structural phase transformation above 2 GPa and amorphization above 20 GPa. On decompression from 20 GPa, the amorphous phase remains unchanged indicating irreversible nature of pressure induced amorphization (PIA). Various low frequency Raman modes corresponding to translation of Zr atoms and coupled rotation of PO4 tetrahedra and ZrO6 octahedra soften with increase in pressure which could be the driving force for the observed phase transition. Pressure induced phase transition could be due to collapse of Zr-O-P bond angles, and PIA due to kinetic hindrance of equilibrium decomposition. We have compared the phase transition and amorphization pressures of the various members of AZr2(PO4)3 to account for the stability of the ambient rhombohedral phase.

Near‐zero thermal expansion transparent lithium aluminosilicate glass‐ceramic by microwave hybrid heat treatment

AbstractThe material of choice for space applications which demand very high dimensional stability is lithium aluminosilicate (LAS) based Ultra Low thermal Expansion Glass‐Ceramic (ULEGC). Generally, the controlled crystallization process recommended for the processing of transparent ULEGC involves a long soaking duration to achieve the required crystal number density. This paper brings out the process optimization procedure adopted for realizing transparent and nanocrystalline ULEGC from conventionally processed LAS glass using microwave‐assisted (hybrid) crystallization. The experimental strategy involves two stages (i) identification of the optimum crystallization temperature (Tc) under a microwave field (ii) optimization of a microwave‐assisted crystallization process to achieve near zero Coefficient of Thermal Expansion (CTE).. Optimum heat‐treatment schedules for nucleation and crystallization under a microwave environment were found to be 720°C/24 hours and 775°C/0.3 hours, respectively. The optimized heat‐treatment condition revealed the efficacy of the microwave hybrid heating, by producing nanocrystalline (35‐50 nm) and transparent (>82%) ULEGC having a thermal expansion of −0.03 × 10−6 K (0°C to 50°C).

Effect of the sintering method on microstructure and thermal and mechanical properties of zirconium oxophosphate ceramics Zr2O(PO4)2

Due to an ultra-low thermal expansion, Zr2O(PO4)2 could find many applications as a thermal shock resistant material. To this end, ceramic processing is a key step in order to reach best properties. In this work, Zr2O(PO4)2 was sintered by conventional sintering and by the spark plasma sintering technique (SPS) with and without additive. Samples made by conventional sintering with ZnO as sintering aid have a maximum relative density of around 92%. Microstructure is composed of large grains and microcracks can be observed. When doped with 5 wt. % of MgO, samples can be densified by SPS up to 99.6% of the relative density and the grain size maintained between 0.5 and 1.5 μm. Thermal conductivity and Vickers microhardness were investigated as a function of the microstructure. Best values were obtained for the ceramic doped with 5 wt.% MgO and sintered by SPS, thanks to a fine microstructure and a small amount of residual microcracks.

Transportable 1555-nm Ultra-Stable Laser with Sub-0.185-Hz Linewidth**Supported by the National Natural Science Foundation of China under Grant No 91536217, the West Light Foundation of the Chinese Academy of Sciences under Grant No 2013ZD02, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences under Grant No 2015334.

We present two cavity-stabilized lasers at 1555 nm, which are built to be the frequency source for a transportable photonic microwave generation system. The frequency instability reaches the thermal noise limit ( of the 10-cm ultra-low expansion glass cavity at 1–10 s averaging time and the beat signal of the two lasers reveals a remarkable linewidth of 185 mHz.

Spectroscopy of the B(1)[formula omitted] transitions of PbO with 10-MHz precision

We have performed high precision spectroscopy of lead oxide (PbO) molecules. The B(1)(υ′=3-6)-X(0+)(υ″=0) transitions located in 398–423nm were investigated by using a cold and slow PbO beam. About 140 lines were measured by comparing with resonances of an ultralow expansion etalon, which allows us to determine absolute frequencies of these lines with the uncertainty of about 10MHz. The υ′=4 level has considerably different spectroscopic constants from other vibrational levels. This can be explained by a homogeneous perturbation due to a near-degenerate vibrational level in the a(1) state.

Medium-finesse optical cavity for the stabilization of Rydberg lasers.

We describe the design, construction, and characterization of a medium-finesse Fabry-Perot cavity for simultaneous frequency stabilization of two lasers operating at 960 and 780 nm wavelengths, respectively. The lasers are applied in experiments with ultracold rubidium Rydberg atoms, for which a combined laser linewidth similar to the natural Rydberg linewidth (≈10 kHz) is desired. The cavity, with a finesse of ≈1500, is used to reduce the linewidth of the lasers to below this level. By using a spacer made of ultra low expansion (ULE) glass with active temperature stabilization, the residual frequency drift is limited to ≲1 MHz/day. The design optimizes for ease of construction, robustness, and affordability.

Self-reliance and independently developed high-finesse spherical ultrastable optical reference cavity

Ultra-stable reference cavity with high finesse is a crucial component in a narrow-linewidth laser system which is widely used in time and frequency metrology, the test of Lorentz invariance, and measure of gravitational wave. In this paper, we report the recent progress of the self-made spherical reference cavity, aiming at the future space application. The main function of cavity is the reference of ultra-stable laser, which is the local reference oscillation source of space optical clock. The diameter of the designed spherical cavity spacer made of ultra-low expansion glass is 80 mm, and the cavity length is 78 mm, flat-concave mirrors configuration, and the radius of the concave mirror is 0.5 m. The support structure is designed to have two 3.9 mm-radius spherical groves located at the poles of the sphere along the diameter direction (defined as support axis), and a 53 angle between the support axis and the optical axis. The mechanic vibration sensitivities of the cavity along and perpendicular to the optical axis are both calculated by finite element analysis method to be below 110-10/g. Five-axis linkage CNC machining sphere forming technology is applied to S80 mm spherical surface processing with spherical contour degree up to 0.02. After a three-stage surface polishing processes, the fused silicamirror substratessurface roughness is measured to be less than 0.2 nm (rms). Implementing double ion beam sputtering technique for mirror coating, the reflection of the coating achieves a reflectivity of 99.999% and a loss of 4 ppm for 698 nm laser. The coating surface roughness is measured to be 0.3 nm (rms). The cavity spacer and the mirror are bonded by dried optical contact. In order to improve the thermal noise characteristics of the cavity, an ultra low expansion ring is contacted optically to the outer surface of the mirror. The cavity is characterized by ring-down spectroscopy, and the finesse is around 195000. With the help of a home-made 698 nm ultra narrow line-width laser, the cavity line-width is measured to be 9.8 kHz by sweeping cavity method. A 698 nm semiconductor laser is locked to this spherical cavity by PDH technology, and the cavity loss is measured to be5 ppm.

Noise Suppression on the Tunable Laser for Precise Cavity Length Displacement Measurement.

The absolute distance between the mirrors of a Fabry-Perot cavity with a spacer from an ultra low expansion material was measured by an ultra wide tunable laser diode. The DFB laser diode working at 1542 nm with 1.5 MHz linewidth and 2 nm tuning range has been suppressed with an unbalanced heterodyne fiber interferometer. The frequency noise of laser has been suppressed by 40 dB across the Fourier frequency range 30–300 Hz and by 20 dB up to 4 kHz and the linewidth of the laser below 300 kHz. The relative resolution of the measurement was that corresponds to 0.3 nm (sub-nm) for 0.178 m long cavity with ability of displacement measurement of 0.5 mm.

A compact, sub-Hertz linewidth 729 nm laser for a miniaturized 40Ca+ optical clock

We present a compact, sub-Hertz 729nm laser for a miniaturized 40Ca+ single-ion optical clock. An external cavity diode laser is frequency-stabilized to a horizontally mounted, vibration-insensitive and high-fineness ultra-low-expansion (ULE) cavity with Pound–Drever–Hall (PDH) method. The laser linewidth is measured to be about 0.9Hz from a heterodyne beat note with the other 729nm laser. After removing the linear drift of about 0.1Hz/s, the fractional frequency instability is less than 2×10−15 (1~100s). This compact, ultra-stable laser system with a volume about 0.1m3 excluding the electronics has been employed into a miniaturized 40Ca+ single-ion optical clock. The clock frequency instability has been measured to be 3.4×10−14/τ1/2 (1~10,000s) with a 729nm laser probe pulse time of 20ms.

Thermo-optical simulation and experiment for the assessment of single, hollow, and large aperture retroreflector for lunar laser ranging

A single aperture and hollow retroreflector [corner-cube mirror (CCM)] that in principle has no internal optical path difference is a key instrument for achieving lunar laser ranging one order or more accurate than the current level (~2 cm). We are developing CCM whose aperture is 20 cm with optimized dihedral angles. The 20-cm CCM yields two times peak height for returned laser pulse compared with Apollo 15’s retroreflector. Two investigations were conducted to confirm the feasibility of the 20-cm aperture CCM. The first is thermo-optical simulation and evaluation of the 20-cm CCM in the lunar thermal environment. Through this simulation, it has turned out for the first time that 20-cm aperture CCM made of single-crystal Si or “ultra-low expansion glass–ceramics” such as CCZ-EX® (OHARA Inc.) can be used for CCM with no thermal control, if the perfectly fixed point of CCM is limited to one. The second is annealing and shear loading experiments of single-crystal silicon (Si) samples. Through these experiments, high-temperature annealing from 100 to 1000 °C is confirmed to be effective for the enhancement of the adhesive strength between optically contacted surfaces with no optical damage in roughness and accuracy, indicating that this annealing process would enhance the rigidity of CCM fabricated by the optically contacted plates.

1 Hz linewidth Ti:sapphire laser as local oscillator for (40)Ca(+) optical clocks.

A Ti:sapphire laser at 729 nm is frequency stabilized to an ultra-stable ultra-low thermal expansion coefficient (ULE) cavity by means of Pound-Drever-Hall method. An acousto-optic modulator is used as the fast frequency feedback component. 1 Hz linewidth and 2 × 10(-15) frequency stability at 1-100 s are characterized by optical beating with a separated Fabry-Perot cavity stabilized diode laser. Compared to the universal method that the error signal feedback to inject current of a diode laser, this scheme is demonstrated to be simple and also effective for linewidth narrowing. The temperature of zero coefficient of the thermal expansion of the ULE cavity is measured with the help of a femto-second frequency comb. And the performance of the laser is well defined by locking it to the unperturbed clock transition line-center of 4 S1/2-3 D5/2 clock transition of a single laser cooled (40)Ca(+) ion. A Fourier-transform limited resonance of 6 Hz (Δv/v = 1.5 × 10(-14)) is observed. This laser is also used as the local oscillator for the comparison experiment of two (40)Ca(+) ion optical clocks and improves the stability of comparison for an order of magnitude better than the previous results.

Molecular frequency reference at 1.56 μm using a 12C16O overtone transition with the noise-immune cavity-enhanced optical heterodyne molecular spectroscopy method.

We report on a molecular clock based on the interrogation of the 3ν rotational-vibrational combination band at 1563 nm of carbon monoxide C1612O. The laser stabilization scheme is based on the noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) technique in frequency modulation (FM) saturation spectroscopy. We use a high-finesse ultra-low expansion (ULE) glass optical cavity with CO as the molecular reference for long-term stabilization of the cavity resonance. We report an Allan deviation of 1.8×10-12 at 1 s that improves to ∼3.5×10-14 with 1000 s of averaging.

Distance measurement using frequency scanning interferometry with mode-hoped laser

In this paper, frequency scanning interferometry is implemented to measure distances up to 5m absolutely. The setup consists of a Michelson interferometer, an external cavity tunable diode laser, and an ultra-low expansion (ULE) Fabry-Pérot (FP) cavity to measure the frequency scanning range. The distance is measured by acquiring simultaneously the interference fringes from, the Michelson and the FP interferometers, while scanning the laser frequency. An online fringe processing technique is developed to calculate the distance from the fringe ratio while removing the parts result from the laser mode-hops without significantly affecting the measurement accuracy. This fringe processing method enables accurate distance measurements up to 5m with measurements repeatability ±3.9×10−6L. An accurate translation stage is used to find the FP cavity free-spectral-range and therefore allow accurate measurement. Finally, the setup is applied for the short distance calibration of a laser distance meter (LDM).

Structural and vibrational relaxations during aging of an ultralow-expansion glass

We accurately measured the aging of an ultralow-expansion (ULE) glass for 1250 days using a diode laser resonated in the glass cavity at −3.3 °C, where the glass has zero thermal expansion coefficient. We observed that the glass shows exponential and linear decreases in length ΔL(d)/L(0)=A0[exp(−d/τ0)−1]−K0×d, where d is the day, τ0 is the relaxation time, and A0 and K0 are constants. Equation shows the structural relaxation with a spontaneous linear contraction after the termination of a classical exponential contraction. It was observed that the rate of linear contraction K0 becomes slightly smaller after an extremely long aging time. These results indicate that after prolonged aging, the length of the glass spontaneously decreases at a constant rate with respect to time, and that its linear contraction becomes weaker due to glass densification.In addition, it is theoretically shown that glass aging is a nonlinear irreversible process with the spontaneous relaxations of a linear contraction and a dissipated heat. The origin for the linear contraction is an osmotic pressure which is spontaneously generated during glass aging, and the origin for the dissipated heat is the irreversibility on thermal vibrations of molecules. The result obtained is a verification of the Glansdorff–Prigogine evolutional criterion, which is first applied to a structural relaxation phenomenon in this paper. We conclude that a glass reaches a steady nonequilibrium state, which has the dissipative structure both in a steady configurational state and in steady irreversible processes.

Comparative Raman spectroscopic study of phase stability and anharmonic effects in AZr2(PO4)3 (A = K, Rb and Cs)

AZr2(PO4)3 (A=Na, K, Rb, Cs) are a set of framework structured compounds that exhibit tunable ultralow thermal expansion over the wide temperature range of 293–1273K. We report a systematic Raman spectroscopic investigation on AZr2(PO4)3 (A=K, Rb and Cs) compounds as a function of temperature in the range 80–860K and pressures of up to 32GPa. To get insight into the thermal expansion property, phonon anharmonicity has been investigated by studying the temperature and pressure dependence of Raman peak shifts and line widths and computed bulk modulus. We have compared the phase transition and amorphization pressures of the various members of AZr2(PO4)3 to account for the stability of the ambient rhombohedral phase. We find that unlike most of the anomalous thermal expansion materials, in AZr2(PO4)3 (A=K, Rb and Cs), the phonons that are anharmonic with temperature do not necessarily exhibit anharmonicity with pressure.

ABSOLUTE DISTANCE MEASUREMENT USING FREQUENCY SCANNING INTERFEROMETRY

Absolute distance measurement is necessary for many applications where the distance to a fixed-target is required. In this paper, frequency scanning interferometry is implemented with an external cavity tunable diode laser, which has a wavelength scanning range of (665-675 nm), to measure distances up to 5 m absolutely (achieved by multi-reflection system). An ultra-low expansion (ULE) Fabry-Perot (FP) cavity has been used as a reference to measure the tunable-laser scanning range. Absolute distance is determined by counting the synthetic fringes and FP peaks simultaneously while scanning the laser frequency. A fringe processing technique is developed to perform online distance measurement even though the tunable laser is not mode-hop free. This fringe processing method enables simple, fast and accurate distance measurements with repeatability ±3.9×10-6 L and combined uncertainty ±38.9×10-6 L which is limited by the calibration system used.

Universal gate-set for trapped-ion qubits using a narrow linewidth diode laser

We report on the implementation of a high fidelity universal gate-set on optical qubits based on trapped 88Sr+ ions for the purpose of quantum information processing. All coherent operations were performed using a narrow linewidth diode laser. We employed a master-slave configuration for the laser, where an ultra low expansion glass Fabry–Perot cavity is used as a stable reference as well as a spectral filter. We characterized the laser spectrum using the ions with a modified Ramsey sequence which eliminated the affect of the magnetic field noise. We demonstrated high fidelity single qubit gates with individual addressing, based on inhomogeneous micromotion, on a two-ion chain as well as the Mølmer–Sørensen two-qubit entangling gate.