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Formation of the Ti 3 (Al,Sn)C 2 solid solutions with a broad substitutional range was investigated by combustion synthesis from elemental powder compacts with Al 4 C 3 and TiC additions. High combustion temperatures of 1590–1700 °C and rapid flame-front speeds of 14.2–18.8 mm/s were measured for the Al 4 C 3 -adopted samples. Due to the dilution effect of TiC, the combustion temperature and velocity were significantly reduced for the TiC-added samples and approximated to 1220–1280 °C and 7.1–9.6 mm/s, respectively. The XRD analysis indicated that Ti 3 (Al 1– x Sn x )C 2 solid solutions with x = 0.2, 0.4, and 0.6 were produced from the Al 4 C 3 -adopted samples. Further increase of Sn to x = 0.8 led to the formation of a large amount of Ti 2 SnC and TiC. Because of the low reaction temperature for the TiC-based reaction scheme, the effective substitution of Sn for Al in Ti 3 (Al 1– y Sn y )C 2 was only achieved at y = 0.2 and 0.4. Incomplete phase formation at y = 0.6 and 0.8 yielded Sn-lean Ti 3 (Al,Sn)C 2 along with Ti 2 SnC, TiC, and free Sn. The as-synthesized Ti 3 (Al,Sn)C 2 grains were formed into the shape of platelets and most of them were closely stacked into a laminated microstructure. [ABSTRACT FROM AUTHOR]

An investigation on formation of the Ti 2 Al(C,N) solid solution with a broad range of substitutional proportion was performed by solid state combustion in the SHS mode. Metal nitrides, BN and TiN, were adopted as the solid source of nitrogen in the Ti–Al–C combustion system. On account of complete participation of BN in combustion, the BN-added sample is more exothermic than that adopting TiN which imposes a dilution effect on combustion. As a result, the combustion temperature and reaction front velocity are higher for the samples containing BN than TiN. Due to fully-sustainable combustibility, the BN-adopted samples were shown to produce TiB 2 /Ti 2 Al(C 1− x N x ) solid solution composites with x =0.2−0.8 and a TiB 2 /Ti 2 AlN composite from the sample free of carbon. However, the combustibility range of the TiN-added sample was constrained by lack of sufficient reaction exothermicity. Although the Ti 2 Al(C,N) solid solution was also produced from the TiN-adopted sample, the degree of substitution in the Ti 2 Al(C 1− y N y ) phase was confined to y ≤0.5. [ABSTRACT FROM AUTHOR]

Preparation of the Ti 2 (Al,Sn)C solid solution with a broad substitutional proportion was conducted by combustion synthesis of TiC- and Al 4 C 3 -containing powder compacts. Experimental results showed that due to the dilution effect of TiC, relatively low combustion temperatures of about 1090 °C and reaction front velocities of around 2.4 mm/s were obtained for the TiC-added samples. As a result of containing larger amounts of Ti and carbon, the Al 4 C 3 -adopted samples were more energetic than the TiC-added samples. However, the high combustion temperature (1220–1450 °C) and rapid flame speed (6.13–13.87 mm/s) associated with the Al 4 C 3 -added sample were found to be unfavorable for the formation of Ti 2 (Al,Sn)C because probably of insufficient reaction time. On the contrary, Ti 2 (Al 1– x Sn x )C solid solutions with x =0.2–0.8 were successfully produced from the TiC-adopted sample. The synthesized Ti 2 (Al,Sn)C grains exhibited a plate-like morphology and formed a laminated microstructure. [ABSTRACT FROM AUTHOR]

Preparation of the Ti 2 (Al,Sn)C solid solution with a broad substitutional proportion was conducted by combustion synthesis of TiC- and Al 4 C 3 -containing powder compacts. Experimental results showed that due to the dilution effect of TiC, relatively low combustion temperatures of about 1090 °C and reaction front velocities of around 2.4 mm/s were obtained for the TiC-added samples. As a result of containing larger amounts of Ti and carbon, the Al 4 C 3 -adopted samples were more energetic than the TiC-added samples. However, the high combustion temperature (1220–1450 °C) and rapid flame speed (6.13–13.87 mm/s) associated with the Al 4 C 3 -added sample were found to be unfavorable for the formation of Ti 2 (Al,Sn)C because probably of insufficient reaction time. On the contrary, Ti 2 (Al 1– x Sn x )C solid solutions with x =0.2–0.8 were successfully produced from the TiC-adopted sample. The synthesized Ti 2 (Al,Sn)C grains exhibited a plate-like morphology and formed a laminated microstructure. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the effects of surfactant and segregation from InAs surface quantum dots (SQDs) by incorporating antimony (Sb) into the QD layers. The Sb surfactant effect extends planar growth and suppresses dot formation. Incorporating Sb can reduce the density of SQDs by more than two orders of magnitude. Photoluminescence (PL) reveals enhancement in the optical properties of InAs SQDs as the Sb beam equivalent pressure (BEP) increases. This improvement is caused by the segregation of Sb on the surface of SQDs, which reduces non-radiative recombination and suppresses carrier loss. The dark line at the SQDs surface in the transmission electron microscopic image suggests that the incorporated Sb probably segregates close to the surface of the SQDs. These results indicate a marked Sb segregation effect that can be exploited to improve the surface-sensitive properties of SQDs for biological sensing. [Copyright &y& Elsevier]

Abstract: Mirror-like and pit-free non-polar a-plane (11−20) GaN films are grown on r-plane (1−102) sapphire substrates using metalorganic chemical vapor deposition (MOCVD) with multilayer high-low-high temperature AlN buffer layers. The buffer layer structure and film quality are essential to the growth of a flat, crack-free and pit-free a-plane GaN film. The multilayer AlN buffer structure includes a thin low-temperature-deposited AlN (LT-AlN) layer inserted into the high-temperature-deposited AlN (HT-AlN) layer. The results demonstrate that the multilayer AlN buffer structure can improve the surface morphology of the upper a-plane GaN film. The grown multilayer AlN buffer structure reduced the tensile stress on the AlN buffer layers and increased the compressive stress on the a-plane GaN film. The multilayer AlN buffer structure markedly improves the surface morphology of the a-plane GaN film, as revealed by scanning electron microscopy. The effects of various growth V/III ratios was investigated to obtain a-plane GaN films with better surface morphology. The mean roughness of the surface was 1.02nm, as revealed by atomic force microscopy. Accordingly, the multilayer AlN buffer structure improves the surface morphology and facilitates the complete coalescence of the a-plane GaN layer. [Copyright &y& Elsevier]

Abstract: This study introduced a novel method using a modified helium gas closed cycle cryogenic system to measure the force acting on a C-shaped magnet by a YBCO superconductor with bias current as a function of temperature. The results showed that the measured force agrees with Lorentz force due to the bias current for normal conductor at temperature higher than the superconducting transition temperature, as expected. However, under a temperature at the beginning of the superconducting transition region, the measured force became larger than the expected Lorentz force. As temperature further decreased, the measured force gradually dropped to zero. A qualitative argument based on the Bean’s model was given to explain the peak in the measured force at the beginning of the transition temperature. [Copyright &y& Elsevier]

A modified helium gas closed cycle cryogenic system has been used to measure the zero field cooling levitation force relaxation as a function of temperature (40–85 K) for three different sizes of YBCO superconducting sample. The time range in our relaxation measurements was from 3 s to 1000 s. A linear logarithmic decay of the levitation forces with time was observed. It was found that the levitation force might decrease more than forty percent in our measured interval. It was also found that the higher temperature and the smaller size the superconductor we have, the faster the levitation force it decays, as one would expected. [Copyright &y& Elsevier]

Chitosan (CTS) microspheres were prepared by a spray drying method using type-A gelatin and ethylene oxide–propylene oxide block copolymer as modifiers. Surface morphological characteristics and surface charges of prepared microspheres were investigated by using scanning electron microscopy (SEM) and microelectrophoresis. The particle shape, size and surface morphology of microspheres were significantly affected by the concentration of gelatin. Betamethasone disodium phosphate (BTM)-loaded microspheres demonstrated good drug stability (less 1% hydrolysis product), high entrapped efficiency (95%) and positive surface charge (37.5 mV). The in vitro drug release from the microspheres was related to gelatin content. Microspheres containing gelatin/CTS 0.4∼0.6(w/w) had a prolong release pattern for 12 h. These formulation factors were correlated to particulate characteristics for optimizing BTM microspheres in pulmonary delivery. [Copyright &y& Elsevier]

Strain-induced tunability of thin DWDM thin-film filters (TFF) fabricated by thinning the substrates of the 100 GHz standard filters was measured. For a 100 µm-thick, 250 by 200 µm thin TFF, wavelength drifts larger than 4.4 nm were achieved with the maximum insertion loss of less than 1.6 dB. [ABSTRACT FROM AUTHOR]