Temperature-induced reversible structural phase transition of 1,4-dimethyl-1,4-diazabicyclo[2.2.2]octane bis(perchlorate)

RSC Advances ◽  
2015 ◽  
Vol 5 (69) ◽  
pp. 55914-55919 ◽  
Author(s):  
Li-Zhuang Chen ◽  
Xing-Xing Cao ◽  
Deng-Deng Huang ◽  
Qi-Jian Pan
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Phase Change ◽  
Phase Change Material ◽  
Structural Phase Transition ◽  
Room Temperature ◽  
Paraelectric Phase ◽  
Structural Phase ◽  
Disorder Transition ◽  
Change Material

A novel molecular-based phase change material was synthesized. The phase transition from a room temperature to a low temperature paraelectric phase might be driven by the order–disorder transition of ClO4− anions and the ordering of twisting motions of the dabco ring.

Phase Transitions and Water Dynamics of [Mn(H2O)6](ClO4 )2 Studied by Differential Scanning Calorimetry and Neutron Scattering Methods

2000 ◽  
Vol 55 (9-10) ◽  
pp. 759-764 ◽  
Author(s):  
E. Mikuli ◽  
A. Migdał-Mikuli ◽  
I. Natkaniec ◽  
J. Mayer
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Neutron Scattering ◽  
Structural Phase Transition ◽  
Room Temperature ◽  
Structural Phase ◽  
Water Dynamics ◽  
Water Molecules ◽  
Temperature Phase ◽  
Solid Phases

Abstract DSC measurements performed at 95 -290 K have shown that [Mn(H 2 O) 6 ](CIO 4) 2 possesses, besides a high-temperature phase, existing above 323 K, four low-temperature solid phases. The inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) pat-terns registered at 20 -290 K have supported the DSC results and provided evidence that the investigated substance possesses even more than five solid phases. The IINS spectra have shown that in the room-temperature phase, water molecules perform fast stochastic reorientation at the picosecond scale. The orientational disorder characteristic for the room-temperature phase can be easily overcooled and frozen. Even by relatively slow cooling at ca. 40 K/hour a metastable, orientational (protonic) glass phase is formed below ca. 160 K. Below ca. 100 K, a structural phase transition was observed by the NPD, however the IINS spectra indicate existence of the pure ordered low-temperature phase only after annealing the sample for a few hours at 100 K. On heating, a structural phase transition takes place at ca. 120 K, and at ca. 225 K water molecules begin fast reorientation.

scholarly journals Thermal Performance Test of a Phase-Change-Material Cool Roof System by a Scaled Model

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Suk Goo Yoon ◽  
Young Kwon Yang ◽  
Tae Won Kim ◽  
Min Hee Chung ◽  
Jin Chul Park
Keyword(s):  
Temperature Distribution ◽  
Low Temperature ◽  
Surface Temperature ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Performance ◽  
Room Temperature ◽  
Roof System ◽  
Cool Roof ◽  
Change Material

General cool roof is effective for reduction of cooling load, but it has a problem of increasing heating load. Therefore, the purpose of this study is to complement the disadvantages of the cool roof system by utilizing phase change characteristics of phase change material (PCM). The study was carried out to verify the thermal performance of the PCM cool roof system by measuring the temperature on the top and bottom of the PCM cool roof system by making a miniature model (600 × 600 × 600 mm). PCM was inserted and not inserted, and the temperature difference according to the finish color (brown and white) was compared. As a result, the plate surface temperature using PCM was lower than that without PCM, and time-lag of temperature increase occurred. As a result of the comparison of temperature according to the finish color (brown and white), white showed a low temperature distribution up to 16.35°C. Even at room temperature, white maintained a low temperature distribution of 5.40°C than brown. The use of PCM cool roof system in roof finishes could lower the surface temperature and keep the room temperature low.

On the polymorphism of benzocaine; a low-temperature structural phase transition for form (II)

2009 ◽  
Vol 65 (4) ◽  
pp. 509-515 ◽  
Author(s):  
Eric J. Chan ◽  
A. David Rae ◽  
T. Richard Welberry
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Structural Phase Transition ◽  
Room Temperature ◽  
Structural Phase ◽  
Space Group ◽  
Polymorphic Forms ◽  
Similar Phase

A low-temperature structural phase transition has been observed for form (II) of benzocaine (BZC). Lowering the temperature doubles the b-axis repeat and changes the space group from P212121 to P1121 with γ now 99.37 °. The structure is twinned, the twin rule corresponding to a 21 screw rotation parallel to a. The phase transition is associated with a sequential displacement parallel to a of zigzag bi-layers of ribbons perpendicular to b*. No similar phase transition was observed for form (I) and this was attributed to the different packing symmetries of the two room-temperature polymorphic forms.

Low-Temperature Structure (T = 235 K) and Structural Phase Transition in [(C2H5)4N]2SnCl6

1987 ◽  
Vol 103 (1) ◽  
pp. 73-78 ◽  
Author(s):  
H. Ketata ◽  
M. H. Ben Ghozlen ◽  
A. Daoud ◽  
I. Pabst
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Temperature Structure

Synthesis and Study of Microcapsules with Beeswax Core and Phenol-Formaldehyde Shell Using the Taguchi Method

2021 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Tejashree Amberkar ◽  
Prakash Mahanwar
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Taguchi Method ◽  
Phase Change ◽  
Phase Change Material ◽  
Surfactant Concentration ◽  
Phenol Formaldehyde ◽  
Processing Parameters ◽  
Agitation Speed ◽  
Change Material

Phenol-formaldehyde shelled phase change material microcapsules (MPCMs) were fabricated and their processing parameters were analyzed with the Taguchi method. Core to shell ratio, surfactant concentration and speed of mixing are the parameters that were optimized in five levels. The optimized values for the surfactant concentration, core to shell ratio and agitation speed were 3%, 1:1 and 800 rpm, respectively. The obtained microcapsules were spherical in shape. The melting enthalpy of the MPCMs synthesized with optimized processing parameters was 148.93 J/g in 35–62 °C. The obtained temperature range of phase transition temperature can be used for storing different food articles such as chocolate and hot served foods.

Structural phase transition at low temperature in La2−x Sr x CuO4 aroundx=0.12 under magnetic fields

1996 ◽  
Vol 46 (S3) ◽  
pp. 1237-1238 ◽  
Author(s):  
Takao Suzuki ◽  
Kaichiro Chiba ◽  
Takayuki Goto ◽  
Tetsuo Fukase
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Magnetic Fields ◽  
Structural Phase Transition ◽  
Structural Phase
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