Wafer-scale heterogeneous integration InP on trenched Si with a bubble-free interface

Heterogeneous integration of compound semiconductors on a Si platform leads to advanced device applications in the field of Si photonics and high frequency electronics. However, the unavoidable bubbles formed at the bonding interface are detrimental for achieving a high yield of dissimilar semiconductor integration by the direct wafer bonding technology. In this work, lateral outgassing surface trenches (LOTs) are introduced to efficiently inhibit the bubbles. It is found that the chemical reactions in InP-Si bonding are similar to those in Si-Si bonding, and the generated gas can escape via the LOTs. The outgassing efficiency is dominated by LOTs\u27 spacing, and moreover, the relationship between bubble formation and the LOT\u27s structure is well described by a thermodynamic model. With the method explored in this work, a 2-in. bubble-free crystalline InP thin film integrated on the Si substrate with LOTs is obtained by the ion-slicing and wafer bonding technology. The quantum well active region grown on this Si-based InP film shows a superior photoemission efficiency, and it is found to be 65% as compared to its bulk counterpart

Grey Correlation Analysis between Macro Mechanical Damage and Meso Volume Characteristics of SBS Modified Asphalt Mixture under Freeze-Thaw Cycles

The effect of freeze–thaw (F–T) in the seasonal frozen area would lead to damage to asphalt pavement. After water enters asphalt pavement, the water in voids would expand at a lower temperature, which could change the void content and number, affecting the macro mechanical properties of the asphalt mixture. The rapid development of CT scanning and digital image processing (DIP) provides powerful technical support for the research of asphalt mixture meso volume characteristics. In this paper, the mechanical properties of basalt fiber reinforced asphalt mixture subjected to F–T cycles were tested at different temperatures to clarify the decay law of mechanical properties under F–T cycles. Then, the meso images of the asphalt mixture under various F–T cycles could be obtained by using CT tomography. Based on DIP technology, the meso characteristic parameters of CT images for asphalt mixture were extracted, and the development of asphalt mixture freeze–thaw damage was further analyzed. The test results showed that with the F–T cycle, the macro mechanical properties of the asphalt mixture rapidly declined in the early stage of the F–T cycle and gradually tended to be flat. There would be serious damage inside the asphalt mixture in the late stage of the F–T cycle. The damage to the mechanical properties of the asphalt mixture under the F–T cycle can be attributed to the change in the internal mesostructure of the asphalt mixture. Based on the grey relational analysis theory, the formation of the connected void was the main factor affecting the damage in the early stage of the F–T cycle, while the formation of new voids mainly affected the later development of F-T damage

Thermodynamic Properties of Double Semiclathrate Hydrates Formed with Tetrabutylphosphonium Chloride + CH4

Phase equilibrium conditions for tetrabutylphosphonium chloride (TBPC) + CH4 double semiclathrate hydrates (SCHs) were determined to evaluate the stabilization effect of TBPC for potential applications of hydrate-based gas separation and storage. The equilibrium data revealed that TBPC strongly enhances the stability of CH4 hydrates by increasing the equilibrium temperature at a given pressure, and the system showed the strongest stabilization effect at a TBPC mass fraction of 0.30. The dissociation enthalpies of (TBPC + CH4) SCHs were calculated from the experimental data obtained in this work using the Clausius-Clapeyron equation and the Peng-Robinson equation of state. It was found that the mean dissociation enthalpies for (TBPC + CH4) SCHs with TBPC mass fractions of 0.05 to 0.50 were (135.49 to 158.32) kJ.(mol of CH4)(-1), which were much higher than that of the pure CH4 hydrate. In addition, to identify the molecular behavior and hydrate structure, Raman spectroscopy measurements were conducted at 203 K. The spectra demonstrated that (TBPC+CH4) SCHs were formed in tetragonal structure I with small 5(12) cages trapping CH4 molecules

Enhanced CH4 storage in hydrates with the presence of sucrose stearate

Clathrate hydrate is a promising option for gas storage and transportation. Sucrose stearate, an environmentally friendly chemical, was studied in CH4 hydrate formation process to evaluate its effect on gas storage of CH4 hydrate. The experiment was conducted systematically with four different sucrose stearate concentrations at three various initial pressures. The experimental data were employed to calculate the normalized hydrate formation rate and equilibrium time based on chemical affinity. The results indicated that the presence of sucrose stearate significantly enhanced the CH4 hydrate formation rate and storage when initial pressure was higher than 5.0 MPa. In addition, Raman spectroscopic analysis was performed to examine the hydrate structure and obtain the theoretical storage capacity. The spectra demonstrated that sucrose stearate decreased the hydration number with not changing CH4 hydrate's structure. The theoretical storage capacity and the energy value were increased by about 2.59%. Combing all the results, sucrose stearate was a good kinetic promoter for CH4 hydrate formation. The systems with sucrose stearate at low concentration and high concentration were suggested for designing gas storage process and fast hydrate formation process, respectively. (C) 2019 Elsevier Ltd. All rights reserved

Compressive and Tensile Fracture Failure Analysis of Asphalt Mixture Subjected to Freeze–Thaw Conditions by Acoustic Emission and CT Scanning Technologies

The cracking of bitumen pavement in seasonal frozen areas has direct and significant influences on its properties. In order to study the compressive and tensile fracture failure features of basalt fiber-reinforced asphalt mix after freeze–thaw (F-T) treatment, the load–displacement curves under the compression and tensile modes of asphalt mixture after F-T conditions were tested. As a real-time detection means, acoustic emission (AE) was used for testing asphalt mix under compression and tensile load modes. X-ray computed tomography (CT) was employed to represent and evaluate the interior void in F-T conditions. The results showed that, as F-T conditions continue, the compressive and tensile strength of the specimens at different temperatures decreases. The amplitude and count of AE signals with the time history of load level show different characteristics of change in various intervals. AE signal indirect parameters reveal that under compressive and tensile load modes there is a gradual deterioration of performance for asphalt mix due to the coupling interactions between tensile and shear cracks. The asphalt mixtures have different behavior in F-T conditions, which are attributable to interior meso-void characteristics based on CT analysis. This study is limited to the type and loading mode of asphalt mixture in order to quantitatively predict the performance of asphalt mixture

Grey Correlation Analysis between Macro Mechanical Damage and Meso Volume Characteristics of SBS Modified Asphalt Mixture under Freeze-Thaw Cycles

The effect of freeze–thaw (F–T) in the seasonal frozen area would lead to damage to asphalt pavement. After water enters asphalt pavement, the water in voids would expand at a lower temperature, which could change the void content and number, affecting the macro mechanical properties of the asphalt mixture. The rapid development of CT scanning and digital image processing (DIP) provides powerful technical support for the research of asphalt mixture meso volume characteristics. In this paper, the mechanical properties of basalt fiber reinforced asphalt mixture subjected to F–T cycles were tested at different temperatures to clarify the decay law of mechanical properties under F–T cycles. Then, the meso images of the asphalt mixture under various F–T cycles could be obtained by using CT tomography. Based on DIP technology, the meso characteristic parameters of CT images for asphalt mixture were extracted, and the development of asphalt mixture freeze–thaw damage was further analyzed. The test results showed that with the F–T cycle, the macro mechanical properties of the asphalt mixture rapidly declined in the early stage of the F–T cycle and gradually tended to be flat. There would be serious damage inside the asphalt mixture in the late stage of the F–T cycle. The damage to the mechanical properties of the asphalt mixture under the F–T cycle can be attributed to the change in the internal mesostructure of the asphalt mixture. Based on the grey relational analysis theory, the formation of the connected void was the main factor affecting the damage in the early stage of the F–T cycle, while the formation of new voids mainly affected the later development of F-T damage

Experimental Study on the Formation Kinetics of Methane Hydrates in the Presence of Tetrabutylammonium Bromide

Tetrabutylammonium bromide (TBAB) could form semiclathrate hydrate under milder conditions compared to gas hydrate and, thus, effectively improve the thermodynamic stability of gas hydrate. To evaluate the effect of TBAB on the formation kinetics of methane hydrates, the kinetic properties of TBAB + CH4 semiclathrate hydrate were investigated with an isobaric method at 7.0 MPa with salt mass fraction and subcooling degree varying from 0.05 to 0.60 and from 4 to 10 K, respectively. The result showed that, with a higher salt concentration and subcooling degree, the induction time presented its stochastic property, while the normalized gas consumption and gas consumption rate were relatively constant and higher, respectively. In addition, Raman spectroscopy, powder X-ray diffraction (PXRD) device, and cryo-scanning electron microscopy were employed to identify the molecular behavior and observe the morphology of the hydrate. The spectra of Raman and PXRD revealed that the CH4 molecules were encaged in dodecahedron cages and its addition induced the orthorhombic pattern, which had the larger potential gas capacity, rather than the tetragonal pattern. The microstructure pictures presented that the addition of TBAB could make the surface of the hydrate more ordered and tight, as a contrary to that of inhibitors, which led to a more chaotic and porous surface. These results could provide important information for hydrate-based industrial applications, such as gas separation and storage

Carrier Phase-Based Ionospheric Gradient Monitor Under the Mixed Gaussian Distribution

Anomalous ionospheric gradient is a critical risk to be monitored by ground-based augmentation systems (GBASs) utilized for safety-of-life navigation applications. A dual-frequency carrier phase-based ionospheric gradient monitoring method is proposed under the mixed Gaussian distribution. The minimum detection error of the proposed method can be greatly reduced by allowing acceptable ambiguity resolution failure modes, given the required averaging length. The real BeiDou navigation satellite system data were utilized to test the proposed method. The experimental results showed that the minimum detection error (MDE) of the proposed dual-frequency ionospheric gradient monitoring method can be reduced by at least 30% in comparison with the maximum acceptable anomalous ionospheric gradient of category III GBAS. This study demonstrated that the proposed method can be used to protect against the ionospheric gradient for a ground-based augmentation system