Impact of compression,physical aging,and freezing rate on the crystallization characteristics of an amorphous sugar matrix

Amorphous matrices made up of sugar molecules, are frequently used in food and pharmaceutical industries. A drawback to their use is that they are susceptible to collapse, as a result of water uptake and an increase in temperature and subsequently crystallize. Herein, the crystallization characteristics of amorphous sugar (sucrose and α-lactose) preparations were analyzed, with the purpose of obtaining knowledge that could lead to the prediction of how long the amorphous state is retained under various conditions. The impact of compression, physical aging and freezing rate on the induction period (t_ind) for crystallization were examined. Freeze-dried sugar samples were compressed at 74 or 443 MPa (5 min) and then rehumidified at specified RHs. Some freeze-dried sucrose samples were physically aged, and alternatively freeze-drying was conducted under different conditions. The isothermal crystallization of the prepared samples at different temperatures (T), the glass transition and the crystallization temperature (T_cry) were measured, using differential scanning calorimetry. The compression markedly decreased the t_ind, while significantly lowered the hygroscopicity. Physical aging and slower-freezing also shortened the t_ind. The t_ind was found to be correlated exclusively with (T_cry–T), regardless of rehumidification, compression, sugar type, physical aging and freezing rate in the freeze-drying process.     

Study on the fabrication of a SU-8 cantilever vertically-allocated in a closed fluidic microchannel

Microsystem Technologies - This paper describes the fabrication of a vertically-allocated SU-8 cantilever in a closed fluidic channel. The difficulties to fabricate the vertically-allocated SU-8...     

Phase transformation and interface segregation behavior in Si3N4 ceramics sintered with La2O3–Lu2O3 mixed additive

Microstructure and mechanical property of silicon nitride (Si₃N₄) ceramic are strongly dependent on the selection of sintering additives. When rare‐earth (RE) oxide is used as the sintering additive, segregation of RE ions at interface between Si₃N₄ grain and intergranular glassy film (IGF) is believed to play a critical role. Although the ionic radius of RE ion is known to be an empirical parameter to modify the mechanical property, the correlation between the segregated ions and their ionic radii is still under controversy. In order to address this issue, (i) rate of α‐β phase transformation and (ii) segregation behavior at the interface were studied for Si₃N₄ ceramics sintered using mixture of La₂O₃ and Lu₂O₃ as additives in this study. Specimens of Lu content 30% and higher exhibited lower activation energies for the α‐β phase transformation as compared with those of Lu content 20% and lower. In terms of the segregation behavior, La was preferably segregated at one site and Lu at the other site along β‐Si₃N₄/IGF interface in the specimens of Lu content 30% and higher. It is understood from these results that Lu segregation site should be more closely related with grain growth.     

Hydrogenation and structural properties of Gd2Ni7 with superlattice structure

The crystal structure and hydrogenation properties of Ce₂Ni₇-type Gd₂Ni₇ were investigated by X-ray diffraction (XRD) and the hydrogen pressure–composition (P–C) isotherm. Ce₂Ni₇-type Gd₂Ni₇ was obtained by annealing at 1523 K for 12 h and quenching in ice water. Two superlattice reflections (002 and 004) of the Ce₂Ni₇-type were clearly observed at 2θ = 7.3° and 14.6° in the XRD profile. The refined lattice parameters were a = 0.49662(9) nm and c = 2.4255(3) nm, respectively. Two plateaus were clearly observed during the absorption–desorption process in the P–C isotherm. The first and second plateaus were at 0.015 and 0.13 MPa, respectively, in the first desorption. The maximum hydrogen capacity reached was 1.13 H/M. The enthalpy and entropy were calculated as −20 kJ/mol H₂ and −80 J/mol H₂ K, respectively, from the van’t Hoff plot. After the P–C isotherm, the GdNi₅ cell expanded by 2.15%, but the Gd₂Ni₄ cell shrank by 2.83%.     

Fabrication of fluorine-terminated diamond-like carbon thin film using a hyperthermal atomic fluorine beam

Surface modification of diamond-like carbon (DLC) film was performed using a hyperthermal atomic fluorine beam on the purpose of production of hydrophobic surface by maintaining the high hardness of DLC film. By the irradiation of atomic fluorine beam of a 1.0 × 10²⁰ atoms/cm², the contact angle of a water drop against the DLC surface increased from 73° to 111°. The formation of CF₃, CF₂ and CF bonding on the modified DLC surface was confirmed from the measurements of X-ray photoelectron spectra and near-edge X-ray absorption fine structure spectra. Irradiation of hyperthermal atomic fluorine beam was concluded to produce insulator fluorine-terminated DLC film, which has high F content on the surface, by the taking of the use of neutral atomic beam as a fluorine source.     

Feasible method,utilizing density changes,for estimating in situ dynamic strength and deformation properties of sand samples

Laboratory tests and design reliability are directly controlled by sample quality. The frozen sampling (FS) method is useful for dynamic strength and deformation tests of undisturbed clean sand. However, it is very expensive and requires considerable equipment. The sample quality of Toyoura sands obtained from 48 mm and 75 mm samplers are scrutinized based on void ratio, dynamic strength and deformation properties through model and cyclic undrained triaxial tests. A conventional method for estimating in-situ dynamic strength and deformation properties of sand samples utilizing density changes is examined and the applicability of the proposed method is discussed for the samples obtained from Niigata sand deposits.The main conclusions obtained from this study are summarized as follows:(1) A conventional method for estimating in-situ void ratio (e₀), D_r, stress ratio (R_L20) in a 20 cyclic time frame and the initial modulus of rigidity (G₀) of sand samples utilizing density changes is proposed.(2) The in-situ R_L20 and G₀ estimated from the proposed method for sand samples from tube samplers were similar to those of frozen sampling and the in-situ modulus of initial rigidity was calculated from the secondary wave velocity for Niigata sand deposits.Therefore, dynamic strength and deformation properties changes, caused by sampling, can be modified appropriately to an in-situ condition by this proposed method.     

Evaluation of mixing profiles for a new micromixer design strategy

The relationship between mixing history and reaction performance in microreactors using computational fluid dynamics (CFD) simulations is identified. In the idealized, simplified mixing model, mixing proceeds linearly and only the mixing time determined the reaction performance. However, in the case of realistic models where mixing proceeds unequally, the partial rapid progression of mixing, more than the mixing time, significantly impacts the reaction. The use of the fluid segment size distribution to capture this effect is proposed. The effective Damköhler number derived from the fluid segment size distribution predicted the reaction yield well. To demonstrate the utility of the mixing profile design strategy, we fabricated a novel micromixer with multiple partial rapid mixing zones. This micromixer achieved excellent results both in a CFD simulation and an experiment. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1154–1161, 2016     

Development of gap sensing system for narrow gap laser welding

Narrow gap welding with an oscillation laser beam is one of the effective processes for thick plate welding. To put this welding process into practical manufacturing, a groove-sensing system using image processing for narrow gap welding with an oscillation laser beam is used. This developed system uses still images of the weld zone taken by a coaxial CMOS camera. It can recognize the position of the groove wall by analysing the brightness distribution in the still image. It can then control the oscillation width and the laser-irradiated area by calculating the groove width and the groove centre position. Some narrow gap welding experiments were performed to evaluate the performance of the developed system. The results revealed that the developed system is effective for narrow gap welding with an oscillation laser beam. Using this system, the narrow gap groove can be welded even if the groove width has changed during the welding process.