monocline

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SELENIUM

Monoclinic selenium crystals appear charcoal-gray (left), but when light is shined through them, they transmit a deep red hue (right). Glassmakers use selenium to add red to their creations, whereas dandruff shampoos use it for its antifungal action. The element is also an essential micronutrient, used in several enzymes where it is usually held in place by the amino acid cysteine.

Credit: www.periodictable.ru

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I meant to post these a while back. They’re from the day trip I took with my mother’s friends up along the northeastern coast of Taiwan.

The northern coast of Taiwan is rocky. Monocline formations like these (at the 北關海潮公園 - Beiguan Tidal Park)are pretty much what you get. You have to go to the south for sandy beaches.

The formations are colloquially known as 豆腐岩, or tofu rocks; the rectangular segments look like sliced 豆腐 sliding apart.

I see it, but they mostly remind me of the coast of western Ireland.

arxiv.org
[1506.08513] Magnetic structure of the spin-1/2 frustrated quasi-one-dimensional antiferromagnet Cu3Mo2O9: Appearance of a partial disordered state

[ Authors ]
Masashi Hase, Haruhiko Kuroe, Vladimir Yu. Pomjakushin, Lukas Keller, Ryo Tamura, Noriki Terada, Yoshitaka Matsushita, Andreas Doenni, Tomoyuki Sekine
[ Abstract ]
We investigated the crystal and magnetic structures of the spin-½ frustrated antiferromagnet Cu3Mo2O9 in which the spin system consists of antiferromagnetic chains and dimers. The space group at room temperature has been reported to be orthorhombic Pnma (No. 62). We infer that the space group above TN = 7.9 K is monoclinic P2_1/m (No. 11) from the observation of reflections forbidden in Pnma in x-ray powder diffraction experiments at room temperature. We determined the magnetic structure of Cu3Mo2O9 in neutron powder diffraction experiments. Magnetic moments on dimer sites lie in the ac planes. The magnitudes are 0.50 - 0.74 mu_B. Moments on chain sites may exist but the magnitudes are very small. The magnetic structure indicates that a partial disordered state is realized. We consider the origin of the magnetic structure, weak ferromagnetism, and electric polarization.

Crystal of the Day for June 22nd is Lazulite

Crystal of the Day for June 22nd is Lazulite

Crystal of the Day


Lazulite

(Color: dark azure-blue to a bright indigo blue)

Hardness: 5.5 – 6
Specific Gravity: 3.1
Chemistry: (Mg, Fe)Al2(PO4)2(OH)2, Magnesium Iron Aluminum Phosphate Hydroxide
Class: Phosphates
Crystallography: Monoclinic; 2/m
Cleavage: distinct in one direction
Fracture: uneven
Streak: pale blue to white
Luster: vitreous to dull

Healing: Lazulite is used for treating…

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Chrome diopside Gemstone is a variety of natural monoclinic pyroxene mineral, possess property of transparent with vitreous luster and are available in rich-green color with micro cut rondelle shape in form of 8 strand necklace stung and tied with adjustable silk knot, in 17 to 20 inches long strand in AAA Grade. Visit http://www.ratnasagarjewels.com/exclusive-gemstone-necklace.html
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arxiv.org
[1506.05294] Temperature-dependent thermal properties of Mg-doped insulating $β$-$\mathrm{Ga_2O_3}$ bulk along [100] and [001]: thermal diffusivity, thermal conductivity and specific heat capacity

[ Authors ]
Martin Handwerg, Rüdiger Mitdank, Zbigniew Galazka, Saskia F. Fischer
[ Abstract ]
The thermal conductivity $\lambda$, diffusivity $D$, specific heat capacity $C_V$ and the Debye-temperature $\theta_\mathrm{D}$ have been investigated for insulating monoclinic $\beta$-$\mathrm{Ga_2O_3}$. Here, we apply AC current heating techniques and determine the thermal diffusivity and specific heat capacity along the [100] and [001]-direction from the so-called $3\omega$ and $2\omega$ voltage signals, respectively. At low temperatures we find an anisotropy of the thermal conductivity for the [100] and [001] direction ($\lambda_\mathrm{[100]}(109 \mathrm{K})=54\pm 5~\mathrm{Wm^{-1}K^{-1}}$;$\lambda_\mathrm{[001]}(109 \mathrm{K})=67\pm 5~\mathrm{Wm^{-1}K^{-1}}$). The anisotropy diminishes for increasing temperature which is reflected by the diffusivity ratio of $D_\mathrm{[001]}/D_\mathrm{[100]}=1.40\pm 0.08$ at $109~\mathrm{K}$ to $D_\mathrm{[001]}/D_\mathrm{[100]}=1.05\pm 0.07$ at $297~\mathrm{K}$. This may find its explanation in a decreased phonon mean free path for higher temperatures. This is confirmed by the temperature dependence of the thermal conductivity which agrees well with the phonon-phonon Umklapp scattering processes. The temperature dependence of the specific heat is in general accordance with the Debye model.

Composition Of Fused Cast High Zirconia Block

In recent years, fused cast high zirconia block is introduced to decrease the number of glass defects and increase the corrosion resistance of refractories for high quality glasses and special glasses, due to its excellent corrosion resistance and no pollution to glass.

Fused cast high zirconia block is developed to operate in extreme condition and also require control of the making process. It is made of artificial synthesis high purity raw materials through special casting process.

The high zirconia fused cast refractory has a structure in which grain boundaries of relatively coarse baddeleyite crystals are filled with a matrix glass mainly composed of SiO2, Al2O3 and ZrO2 and contains a small amount of Na2O and/or K2O.

ZrO2 adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The larger the content of the ZrO2 component in the refractory, the higher the corrosion resistance against molten glass.

However, when the content of ZrO2 is too much, it becomes difficult to obtain a fused cast refractory having no cracks by casting. When the zirconia crystals undergo reversible transformation between monoclinic crystals and tetragonal crystals, a rapid volume change will happen at a temperature from 1,000℃ to 1,150℃. As a result, fused cast high zirconia block is more difficult than fused cast AZS, as the volume expansion rate may cause cracks and a spalling phenomenon. The stress caused by the volume change can be absorbed by glass phase. So the SiO2 component is an essential component to avoid cracking.

The Al2O3 component plays an important role in adjusting the relation between the temperature and the viscosity of the matrix glass and provides an effect of reducing the concentration of the ZrO2 component dissolved in the matrix glass. By utilizing this effect of the Al2O3 component, it is possible to prevent precipitation of zircon in the matrix glass and to prevent the change in quality of the matrix glass, whereby it is possible to avoid the chipping off phenomenon of the refractory and cracking due to an accumulation of remaining volume increase.

Na2O and/or K2O provides a function of softening glass. They are important components which influence the viscosity of the matrix glass and also have an effect of controlling the concentration of the ZrO2 component to some extent.

Fused cast high zirconia block has wide application in a wide range of super high temperature furnaces and kilns in military industry,science research, high melting point Metallurgical, laser crystal and electronic,etc. Sunrise Refractory offers fused cast high zirconia block TY-Z88-WS and TY-Z95-WS, and are used in sidewall, throat cover, throat support, electrode block, dam block parts.

Composition Of Fused Cast High Zirconia Block

In recent years, fused cast high zirconia block is introduced to decrease the number of glass defects and increase the corrosion resistance of refractories for high quality glasses and special glasses, due to its excellent corrosion resistance and no pollution to glass.

Fused cast high zirconia block is developed to operate in extreme condition and also require control of the making process. It is made of artificial synthesis high purity raw materials through special casting process.

The high zirconia fused cast refractory has a structure in which grain boundaries of relatively coarse baddeleyite crystals are filled with a matrix glass mainly composed of SiO2, Al2O3 and ZrO2 and contains a small amount of Na2O and/or K2O.

ZrO2 adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The larger the content of the ZrO2 component in the refractory, the higher the corrosion resistance against molten glass.

However, when the content of ZrO2 is too much, it becomes difficult to obtain a fused cast refractory having no cracks by casting. When the zirconia crystals undergo reversible transformation between monoclinic crystals and tetragonal crystals, a rapid volume change will happen at a temperature from 1,000℃ to 1,150℃. As a result, fused cast high zirconia block is more difficult than fused cast AZS, as the volume expansion rate may cause cracks and a spalling phenomenon. The stress caused by the volume change can be absorbed by glass phase. So the SiO2 component is an essential component to avoid cracking.

The Al2O3 component plays an important role in adjusting the relation between the temperature and the viscosity of the matrix glass and provides an effect of reducing the concentration of the ZrO2 component dissolved in the matrix glass. By utilizing this effect of the Al2O3 component, it is possible to prevent precipitation of zircon in the matrix glass and to prevent the change in quality of the matrix glass, whereby it is possible to avoid the chipping off phenomenon of the refractory and cracking due to an accumulation of remaining volume increase.

Na2O and/or K2O provides a function of softening glass. They are important components which influence the viscosity of the matrix glass and also have an effect of controlling the concentration of the ZrO2 component to some extent.

Fused cast high zirconia block has wide application in a wide range of super high temperature furnaces and kilns in military industry,science research, high melting point Metallurgical, laser crystal and electronic,etc. Sunrise Refractory offers fused cast high zirconia block TY-Z88-WS and TY-Z95-WS, and are used in sidewall, throat cover, throat support, electrode block, dam block parts.

Gemstone of the Day for June 14th is Raspite

Gemstone of the Day for June 14th is Raspite

Gemstone of the Day

Raspite
 
Named for Charles Rasp (1846-1907), German-Australian prospector, discoverer
of the Broken Hill ore deposit.


Hardness: 2.5 – 3                 Specific Gravity: 8.4                          Chemistry: PbWO4
Class: Anhydrous Molybdates and Tungstates (Sheelite group)                 Crystallography: Monoclinic – Prismatic                    
Cleavage: perfect    …

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