Diopside Crystals Research Articles

Glass-ceramics one-step crystallization accomplished by building Ca2+ and Mg2+ fast diffusion layer around diopside crystal

CaOMgOSiO2 (CMS) glass-ceramics preparation normally needs two-step heat treatment (nucleation and crystal growth). In this work, CMS glass-ceramics are successfully produced by one-step heat treatment by building Ca2+ and Mg2+ fast diffusion layer between the residual glass and diopside crystal. High-temperature X-ray diffraction (HTXRD) shows that diopside crystals formed during the crystallization of CMS glass. At the glass layer between diopside crystal and residual glass, an enrichment of Na+ is observed by energy dispersive spectroscopy line scanning (EDSLS), which increases the SiONa bonds that promote Ca2+ and Mg2+ ions diffusion. This layer eventually promotes further growth or ripening of the diopside crystals. Thus, nucleation and crystal growth of the CMS glass proceed continuously at the crystallization peak temperature (Tnc), detected by differential scanning calorimetry. Thereby, one-step crystallization of the CMS glass-ceramics becomes possible and practical.

Preparation of Glass-Ceramics by Reactive Crystallization with Waste Glass and Mullite

Diopside glass-ceramics were prepared by reactive crystallization with mixed powder of waste glass and mullite. The effects of mullite content and sintering temperature and holding time on the crystal phase and morphology of diopside glass-ceramics were investigated. The reactive crystallizing behavior between waste glass powder and mullite was studied using energy dispersive spectrdmeter during the sintering and holding process. The result show that the optimum preparation conditions were as follows: the addition of 30 wt% mullite used as crystallization promoting agent, sintering temperature of 900 °C and holding time of 2h. The main difference between reactive crystallization method and the traditional method of preparing diopside glass-ceramics was the reactive crystallization mechanism. The diopside and corundum crystals were formed via an interaction between glass powder and mullite instead of direct precipitation from the parent glass during the calcining and holding process. With the increasing of sintering temperature and holding time, the Ca and Mg element concents of the glass were increased, on the contrary, that Si element concent was decreased in the mullite. It shows that the Si element diffused from mullite to glass and precipitated diopside crystals.

On the induction of homogeneous bulk crystallization in Eu-doped calcium aluminosilicate glass by applying simultaneous high pressure and temperature

From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca3Mg(SiO4)2] and diopside [CaMgSi2O6]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f65d1 → 4f7 transition of Eu2+ was studied in both host systems. Additionally, the 5D0 → 7FJ transition of Eu3+ was used as an environment probe in the pristine glass and the glass-ceramic.

Isotopic microanalysis sheds light on the magmatic endmembers feeding volcanic eruptions: The Astroni 6 case study (Campi Flegrei, Italy)

Sr-isotopic microanalysis has been performed on selected minerals from the Campi Flegrei caldera, together with Sr and Nd isotopic ratio determinations on bulk mineral and glass fractions. The aim was a better characterization of the chemically homogeneous, but isotopically distinct magmatic components which fed volcanic eruptions of the caldera over the past 5ka, in order to enhance our knowledge about one of the most dangerous volcanoes on Earth.Information on the involved magmatic endmembers, unobtainable by analyzing the isotopic composition of whole rock samples and bulk mineral fractions, has been acquired through high-precision determination of 87Sr/86Sr on single crystals and microdrilled mineral powders. We focused our investigations on the products emplaced during the Astroni 6 eruption (4.23calka BP), assumed representative of the expected event in case of renewed volcanic activity in the Campi Flegrei caldera. Data on single crystals and microdrilled mineral powders have been compared with Sr and Nd isotopic compositions of bulk mineral fractions from products emplaced during the whole Astroni activity, which included seven distinct eruptions. The 87Sr/86Sr ratios of single crystals and microdrilled mineral powders are in the 0.7060 to 0.7076 range, much wider than that of bulk mineral fractions, which range from 0.7066 to 0.7076. Moreover, the Sr isotopic ratios are inversely correlated to 143Nd/144Nd. The new data allow us to better define the magmatic endmembers involved in mingling/mixing processes that occurred prior to/during the Astroni activity. One magmatic endmember, characterized by average 87Sr/86Sr ratio of ~0.70750, was quite common in the past 15ka activity of the Campi Flegrei caldera; the other, as evidenced by the isotopic composition of single feldspar and clinopyroxene crystals, is less enriched in radiogenic Sr (87Sr/86Sr ~0.70724). The latter is interpreted to represent a new magmatic component that entered the Campi Flegrei caldera feeding system in the past 5ka, the previously recognized Astroni 6 component. However, diopside crystals in Astroni 6 are characterized by even lower 87Sr/86Sr, in the range of 0.7060–0.7068 and by the highest 143Nd/144Nd ratios measured in the products of Astroni activity. These diopsides may represent another common magmatic component, as they have been found in most of the Phlegrean Volcanic District products emplaced over the past 75ka. These diopsides, crystallized in a mantle-derived mafic magma, were entrapped by the Astroni 6 magma during ascent, before it mingled/mixed with the more differentiated and enriched in radiogenic Sr resident magma, thus attaining an intermediate Sr-Nd isotopic fingerprint.These results have an important outcome on the understanding of the volcano behavior, as renewed activity can be triggered by the arrival of fresh magma in the feeding system that would mingle/mix with the resident magma. Such an event may be able to start an unrest phase at the volcano that could last for years or decades, perhaps culminating in a new eruption.

Lancaster delftware: a Raman spectroscopy, electron microscopy and Mössbauer spectroscopy compositional study

In 2008, excavations were conducted by the Northern Ceramic Society at the site of the former Lancaster delftware potworks, which operated between 1754 and about 1790. The recovered sherds have been non‐destructively examined by Raman and electron microscopies and the iron phases in the biscuit by Mössbauer spectroscopy. These methods have provided a new understanding of the mineralogy of the delftware produced at Lancaster using clay imported from Carrickfergus in Ireland and blended with the local ferruginous‐aluminous clays. This has implications for the attribution of delftware produced at Liverpool, Bristol, Scotland and Ireland. The Carrickfergus clay has been found to be highly dolomitic resulting in the body of the delftware forming diopside and the magnesian olivine forsterite, when fired. Brookite had not converted to rutile, nor had tridymite, nor cristobalite formed; the K‐feldspars did not undergo further chemical reactions, and the observation of metakaolin would suggest that the biscuit firing temperature was in the order of 800–900 °C. Chalcedony containing moganite was established as the silica source. A cobalt‐containing lead‐tin glaze was applied to the biscuit body and, after decorating, was fired. The mineralogy of the pigments used to decorate the objects indicate the yellow to be the PbSbSn triple oxide, the green to be a copper silicate mixed with lead‐tin yellow, the purple and browns to be manganese silicates and the blue to contain cobalt spinels and cobalt pyroxenes. Diopside crystals together with recrystallised tin agglomerates have been observed floating within the glaze. Copyright © 2015 John Wiley & Sons, Ltd.

Co, Fe가 diopside 결정색 변화에 미치는 영향

본 연구에서는 도예가들이 경험적으로 제조하여 사용하는 diopside 결정유약에 <TEX>$Co_3O_4$</TEX>와 <TEX>$Fe_2O_3$</TEX>를 첨가하였을 경우 Co와 Fe이 유약과 diopside 결정의 발색에 미치는 영향을 연구하고자 하였다. 그 결과 diopside 결정유약에 <TEX>$Co_3O_4$</TEX>를 넣을 경우 유약의 색상은 blue색을 띠며 결정의 색상은 diopside 결정에 Co가 고용되면서 pastel violet색을 띠었으며 diopside 결정유약에 <TEX>$Fe_2O_3$</TEX>를 넣을 경우 유약의 색상은 brown색을, 결정의 색상은 diopside 결정에 Fe가 고용되면서 goldenrod색을 띠었다. 그리고 diopside 결정유약 표면에 석출된 결정은 diopside 결정과 diopside precursor로 이루어져 있었다. 또한 유지시간이 길어짐에 따라 diopside precursor의 량은 줄고 diopside 결정량은 많아졌다. Diopside 결정에는 Fe보다는 Co가 더 잘 고용되었으며, Co가 고용될 경우 diopside 결정성은 더 좋아져 특성 peak의 강도가 높아졌다. 그리고 Fe이 고용되면 특성 peak의 강도는 낮아지면서 diopside 결정은 부분적으로 와해됨을 알 수 있었다. This study was conducted to study the influence of Co and Fe on the color of glaze and diopside crystals in the diopside crystal glaze empirically produced and used by ceramic artists, in case of adding <TEX>$Co_3O_4$</TEX> and <TEX>$Fe_2O_3$</TEX>. As a result, the color of glaze was blue when <TEX>$Co_3O_4$</TEX> was added to the diopside crystal glaze and the diopside crystals appeared pastel violet with Co included. When <TEX>$Fe_2O_3$</TEX> was added to the diopside crystal glaze, the color of glaze appeared brown and the color of diopside crystals was goldenrod with Fe included. The crystals precipitated on the surface of diopside consisted of diopside crystals and diopside precursors. With longer retention time, the amount of diopside precursors decreased and the amount of diopside crystals increased. Also, Co was more easily included by the diopside crystals than Fe was and crystallizability of dispside was improved in case of including Co. Including Fe lowered peak intensity of properties and partially dissolved the diopside crystals.

Diopside Crystal Glaze Using Seed

Currently, diopside (<TEX>$MgCaSi_2O_6$</TEX>) crystal glaze is used frequently for pottery works or in earthen wares, though the process is not straightforward. However, to create and control the positions and sizes of the crystals in desired amounts when making pottery is difficult. To solve this problem, a diopside crystal seed was created at a temperature of <TEX>$1450^{\circ}C$</TEX>. After planting this seed in the glaze, a glaze combination and firing process which allows a user to create crystals with the desired position and at the desired size were established. In addition, in order to investigate the creation process of the crystals, the growth patterns of the crystals were observed and examined using Raman spectrography and XRD and SEM analyses. As a result, the optimum synthesis condition of the diopside seed was created by mixing 1 mole of <TEX>$CaCo_3$</TEX>, 0.2 mole of <TEX>$(MgCo_3)_4(MgCoH)_2{\cdot}5H_2O$</TEX> and 2 moles of <TEX>$SiO_2$</TEX> and then applying a firing process to the mixture at <TEX>$1,450^{\circ}C$</TEX> for 30 minutes. The optimum glaze content of the seed was 70 % feldspar, 20 % limestone and 10 % <TEX>$MgCo_3$</TEX>. For the firing process, it was confirmed that the size of crystal is larger with a longer firing time at <TEX>$1100^{\circ}C$</TEX> by completing a two-hour process at <TEX>$1280^{\circ}C$</TEX>. In addition, the diopside crystal has columnar structure and is less than <TEX>$1{\mu}m$</TEX> in size.

An experimental study of pyroxene crystallization during rapid cooling in a thermal gradient: application to komatiites

Abstract. To investigate the crystallization of pyroxene in spinifex-textured komatiites, we undertook a series of experiments in which compositions in the CaO-MgO-Al2O3-SiO2 CMAS system were cooled rapidly in a thermal gradient. Cooling rates were generally between 5 and 10 °C h−1, but some runs were made at 100–200 °C h−1; thermal gradients were between 10 and 20 °C cm−1. These conditions reproduced those at various depths in the crust of komatiite lava flow. The starting composition was chosen to have pigeonite on the liquidus, and most of the experimental charges crystallized zoned pigeonite–diopside crystals like those in komatiite lavas. An intriguing aspect of the experimental results was their lack of reproducibility. Some experiments crystallized forsterite, whereas others that were run under similar conditions crystallized two pyroxenes and no forsterite; some experiments were totally glassy, but others crystallized entirely to pyroxene. The degree of supercooling at the onset of pyroxene crystallization was variable, from less than 25 °C to more than 110 °C. We attribute these results to the difficulty of nucleation of pyroxene under the conditions of the experiments. In some cases forsterite crystallized metastably and modified the liquid composition to inhibit pyroxene crystallization; in others no nucleation took place until a large degree of supercooling was achieved, and then pyroxene crystallized rapidly. Pigeonite crystallized under a wide range of conditions, at cooling rates from 3 to 100 °C h−1. The notion that this mineral only forms at low cooling rates is not correct.

The First Step in the Production of Fiber‐Diopside Crystal

In this study, the use of sepiolite, formed as fibers in nature, in the production of fiber‐diopside crystals and its effect on crystallization were researched. Sintering process was performed for both pellet and powdered samples. Grain–grain interactions in pellets were effective in diopside crystallization during sintering. It was determined that poor grain–grain interactions and grains with pores formed local glassy phase and crystallization. Dendritic structure was largely formed than eutectic structure within the pellets. The prevention of dendritic growth of crystals by determining the cooling interval could yield longer fiber crystals.

Diffusion-controlled metamorphic reaction textures in an ultrahigh-pressure impure calcite marble from Dabie Shan, China

The overall metamorphic reaction in an impure calcite marble from the ultra-high pressure (UH P ) zone at Changpu, eastern Dabie Shan, China, is partitioned into local reaction domains defined by isolated grains of omphacite, garnet, epidote, quartz and ilmenite within the calcite matrix. These reaction domains witness different stages of the metamorphic evolution. Chemically homogeneous omphacite in some instances has partial or complete coronas of quartz which are interpreted as a prograde phenomenon, i.e . caused by replacement of a plagioclase precursor by omphacite with increasing pressure. Rare relics of talc in epidote indicate that the first breakdown reaction during exhumation was talc + omphacite + garnet = amphibole + epidote ± quartz (still within the eclogite facies). During this early retrogression stage, omphacite was partially or completely rimmed by chemically heterogeneous amphibole. Most garnets developed a thick corona of epidote plus some quartz and calcite during this early retrogression or are completely pseudo-morphed. Where garnet occurs near or next to omphacite, this corona consists partly or entirely of amphibole. The second retrograde stage is commonly characterized by the breakdown of omphacite + quartz to albite + diopside + amphibole, often in the form of symplectite. Localized reactions become evident as omphacite at its site can decompose to three distinct types of symplectite (albite + diopside, albite + amphibole, albite + diopside + amphibole). Matrix quartz grains develop rims of individual diopside crystals at distances up to 2–3 millimetres from symplectites; additional outer rims of albite develop adjacent to garnet or corona epidote. Matrix quartz remote from omphacite sites is locally transformed into albite, where an Al-bearing mineral (mostly epidote) is found nearby. Epidote in contact with quartz develops albite coronas as it decomposes into albite + minute grains of Ce-rich epidote (allanite). Primary epidote and corona epidote remote from any quartz develop a complex compositional zoning with enrichment of mainly Ce 3+ at the outer rim, indicating exposure to a fluid undersaturated in alumina. Finally, large ilmenite grains in the matrix develop thick overgrowths of titanite, but in several instances an intermediate step of rutile formation is preserved. All these features indicate a direct correlation of textures with transport distances of dissolved chemical species in a non-pervasively infiltrating pore fluid. Simplified open-system reactions were derived for each site at each metamorphic stage and show that Al must have been quite mobile during prograde quartz corona formation, whereas both Si and Al were relatively immobile during the two retrograde stages – the relative sequence of mobility being Na + > Mg 2+ , Ca 2+ , Fe 2+ >> Si 4+ > Al 3+ , Ti 4+ . Mass-balance between sites is consistent and no significant gain or loss of cations is indicated.

Effect of CaO/SiO2 ratio on the preparation and crystallization of glass-ceramics from copper slag

Glass-ceramics were synthesized successfully from iron-rich copper slag and the iron was recovered in the same process so that iron-rich copper slag was recycled efficiently. The influence of CaO/SiO2 ratio on the preparation of glass-ceramics was emphasized using differential scanning calorimetry (DSC), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the residual iron concentration of the quenched glass is less than 1.43mass% and Fe concentration in recovery of copper slag is more than 96.6mass%, highlighting that the iron is extracted effectively from copper slag. Crystallization kinetics result shows an increase in the activation energies of crystallization with an increase in CaO/SiO2 ratio up to 0.38 and subsequently a decrease with further increase in CaO/SiO2 ratio up to 0.42. Anorthite with lamellar shape and diopside with irregular column shape are developed as the major phases in all the glass-ceramics samples with different CaO/SiO2 ratios. The increase in CaO/SiO2 ratio hinders the crystal growth of lamellar anorthite but benefits the formation of diopside crystals. For CaO/SiO2=0.42, the optimal comprehensive properties of the glass-ceramics are achieved: low porosity of 0.11%, low bibulous rate of 0.04%, high density of 2.75g/cm and high hardness of 85.75HBa.

Fe–Mg interdiffusion rates in clinopyroxene: experimental data and implications for Fe–Mg exchange geothermometers

Chemical interdiffusion of Fe–Mg along the c-axis [001] in natural diopside crystals (X Di = 0.93) was experimentally studied at ambient pressure, at temperatures ranging from 800 to 1,200 °C and oxygen fugacities from 10−11 to 10−17 bar. Diffusion couples were prepared by ablating an olivine (X Fo = 0.3) target to deposit a thin film (20–100 nm) onto a polished surface of a natural, oriented diopside crystal using the pulsed laser deposition technique. After diffusion anneals, compositional depth profiles at the near surface region (~400 nm) were measured using Rutherford backscattering spectroscopy. In the experimental temperature and compositional range, no strong dependence of D Fe–Mg on composition of clinopyroxene (Fe/Mg ratio between Di93–Di65) or oxygen fugacity could be detected within the resolution of the study. The lack of fO2-dependence may be related to the relatively high Al content of the crystals used in this study. Diffusion coefficients, D Fe–Mg, can be described by a single Arrhenius relation with$$D^{{{\text{Fe}} - {\text{Mg}}}} = 2. 7 7\pm 4. 2 7\times 10^{ - 7} {\text{exp(}}-3 20. 7\pm 1 6.0{\text{ kJ}}/{\text{mol}}/{\text{RT)m}}^{ 2} /{\text{s}}.$$ D Fe–Mg in clinopyroxene appears to be faster than diffusion involving Ca-species (e.g., D Ca–Mg) while it is slower than D Fe–Mg in other common mafic minerals (spinel, olivine, garnet, and orthopyroxene). As a consequence, diffusion in clinopyroxene may be the rate-limiting process for the freezing of many geothermometers, and compositional zoning in clinopyroxene may preserve records of a higher (compared to that preserved in other coexisting mafic minerals) temperature segment of the thermal history of a rock. In the absence of pervasive recrystallization, clinopyroxene grains will retain compositions from peak temperatures at their cores in most geological and planetary settings where peak temperatures did not exceed ~1,100 °C (e.g., resetting may be expected in slowly cooled mantle rocks, many plutonic mafic rocks, or ultra-high temperature metamorphic rocks).

OH in diopside and enstatite at 6 GPa in the system CaO–MgO–SiO2–H2O

Single crystals of pure diopside (CaMgSi 2 O 6 ) were synthesized at 6 GPa or 8 GPa and between 1300 °C and 1150 °C under water-saturated conditions coexisting with forsterite + enstatite, enstatite + coesite, wollastonite + coesite or forsterite + wollastonite, and the incorporation mechanisms of OH in the pyroxenes in the respective phase assemblage were studied by FTIR-spectroscopy. The IR spectra of diopside exhibit two different OH-absorption bands: one prominent band at 3357 cm −1 that appears in all spectra, whereas another band at 3598 cm −1 only appears in spectra of diopside synthesized under lower silica activity ( i.e ., coexisting with forsterite). The band at 3598 cm −1 indicates a low availability of Si and can be assigned to tetrahedral OH-defects (T-site vacancies), while the band at 3357 cm −1 can be assigned to octahedral defects (M-site vacancies). Enstatite crystals from the assemblages diopside + enstatite + coesite and diopside + enstatite + forsterite exhibit an additional absorption band at 3436 cm −1 when compared to enstatite synthesized in the system MgO–SiO 2 –H 2 O. This absorption band could be caused by generation of additional hydrous defects due to the incorporation of Ca that amounts up to 1.8 wt% CaO in enstatite coexisting with diopside. The water content of diopside coexisting with enstatite and coesite clusters around 145 ppm (wt), while the water content of diopside from all other phase assemblages clusters around 60 ppm (wt). The new results suggest that the water content in pyroxenes correlates with silica activity during formation.

Petrographic and microprobe study of nephrites from Lower Silesia (SW Poland)

Lower Silesia hosts important European nephrite deposits of Jordanów and less-known of Złoty Stok. Nephrite artifacts were discovered in archaeological sites dated back to the Neolithic period, across Eurasia. Especially artifacts found in Poland, Italy and Bulgaria may originate from Polish nephrites. Nowadays, only one artifact is precisely linked to Jordanów. Petrographic study of nephrites and chemical analyses of constituents by means of EMPA allow accurate identification of the nephrites. The characteristic phases of Jordanów tremolite nephrite are rotated and cataclased diopside porphyroblasts with pressure shadows, chlorite layers and nests with interlocking non-pseudomorphic texture and prehnite veins. The presence of hydrogrossular, grossular, titanite, apatite with monazite inclusions, and zircon with pleochroic haloe is typical. Chlorites are usually represented by penninite, and minor clinochlore and diabantite. The characteristic features of Złoty Stok actinolite nephrite are löllingite and diopside crystals usually visible by the naked eye, with the presence of quartz and carbonates. Löllingite is chemically inhomogeneous and gold bearing. Most of the mineralogical-petrological features can be obtained using non-destructive methods

Shonkinites and minettes of the Ryabinovyi massif (Central Aldan): composition and crystallization conditions

Dikes of biotitic shonkinites and minettes of the complex Ryabinovyi alkaline massif (Central Aldan) have been studied. The dikes are localized in a neck of K-picrites in the northeast of the massif, which intrudes gold-bearing microcline–muscovite metasomatites (Muscovitovyi site). The obtained data on the chemical and trace-element compositions of the rocks and minerals and study of melt inclusions in clinopyroxenes indicate that the biotitic shonkinites and minettes crystallized from the same deep-seated high-pressure alkaline ultrabasic magma during its evolution. Apparently, at the early stage of crystallization of diopside in the biotitic shonkinites, homogeneous carbonate–silicate melt was separated into immiscible fractions of silicate, carbonate–salt, and carbonate melts. The temperature of melt immiscibility was >1120–1190 °C, i.e., higher than the homogenization temperature of silicate inclusions in the diopside. The contents of trace elements in the biotitic shonkinites and rock-forming clinopyroxenes were one or two orders of magnitude higher than the mantle values. The Eu/Eu* ratios of both the considered rocks and the clinopyroxenes were close to those of chondrites, which testifies to their crystallization from mantle magma. The HREE/LREE ratio indicates that the magma source was localized at the depths where garnet-spinel assemblages existed. The negative Nb and Ti anomalies in the trace-element spectra and the high (>5) La/Nb ratios in the rocks and clinopyroxenes point to the influence of crustal material on the parental magma. Crystallization of magma took place in reducing conditions, which is evidenced by the low (4–7) Ti/V ratios in clinopyroxenes and the presence of chloride–sulfate inclusions in them. Since gold in the Ryabinovyi massif is associated with late sulfate–chloride and sulfate–carbonate fluids, it might have been transported by alkaline chloride–sulfate and carbonate (carbonatite) melts, found as inclusions in clinopyroxenes of the biotitic shonkinites, at the early stages of Mesozoic magmatism.

Optimum Condition and Color Mechanism for Gold Color Glaze in Diopside Crystallization

Generally, the color gold has had a biased conception due to its traditional use. Thus, this bias has resulted in a lack of usage of golden glaze on ceramics and also a lack of extensive studies of such glazes. In this paper, optimum conditions and mechanism of formation of gold color crystallization glaze containing <TEX>$Fe_2O_3$</TEX>(hematite), which is developed for gold colors of ceramic glazes, were studied. Experimental result showed that there are pyroxene based on diopside and <TEX>$TiO_2$</TEX> phase in the base of a crystallization glaze with a value of <TEX>$TiO_2$</TEX> of 6 wt% confirmed by XRD and Raman Spectroscopy. When <TEX>$Fe_2O_3$</TEX> was used as a colorant for the gold color, the <TEX>$TiO_2$</TEX> peak became extinct and the intensity of the diopside peak was sharper. Feldspar of 60 wt%, talc of 20 wt% and limestone of 20 wt% were used as the starting materials and these were tested using a three component system. The best result of test was selected and extended to its vicinity as an experiment to determine <TEX>$TiO_2$</TEX> and <TEX>$Fe_2O_3$</TEX> contents. The glaze with <TEX>$TiO_2$</TEX> of 6 wt% and <TEX>$Fe_2O_3$</TEX> of 12 wt% addition showed stable pyroxene based diopside crystals and the development of gold color. This gold color was obtained with CIE-<TEX>$L^*a^*b^*$</TEX> values of 51.27, 4.46, 16.15 (a grayish yellow brown color), which was gained using the following firing conditions: temperature increasing speed <TEX>$5^{\circ}C$</TEX>/min, holding for 1 h at <TEX>$1280^{\circ}C$</TEX>, annealing speed <TEX>$3^{\circ}C$</TEX>/min till <TEX>$1100{\circ}C$</TEX>, holding for 2 h at <TEX>$1100{\circ}C$</TEX>, and finally natural annealing.

Melt-Rock Reaction in the Mantle: Mantle Troctolites from the Parece Vela Ancient Back-Arc Spreading Center

The Godzilla Megamullion is a giant oceanic core complex located in an extinct slow-spreading segment of the Parece Vela Basin (Philippine Sea). It exposes lower crust and mantle, offering an opportunity to unravel the architecture, composition, and magmatic processes operating in the shallow mantle of a back-arc basin. Here we present data on primitive troctolites and associated olivinegabbros close to the breakaway zone of the megamullion. The troctolites are subdivided into olivine (olivine460 vol. %) and plagioclase (plagioclase460 vol. %) sub-types. Both have textures and mineral compositions suggesting formation through melt^rock reaction.We suggest that the Ol-troctolites formed by dissolution and disaggregation of dunite with crystallization of new plagioclase and diopside by a mid-ocean ridge basalt (MORB)-like melt, producing a high-Mg melt.The Pl-troctolites probably formed by local dissolution of an anorthositic cumulate and crystallization of olivine, diopside and new plagioclase owing to mixing the high-Mg melt residual to the formation of the Ol-troctolites with melt crystallizing an anorthositic cumulate. We show that the Oland Pl-troctolites and associated Ol-gabbros were strongly influenced by melt^rock reaction with the enclosing peridotite, reflecting solidification by reaction and conductive cooling of ascending melts in the mantle. The effects of the melt^rock reaction account for a sharp decrease in plagioclase anorthite content with respect to diopside Mg# and olivine forsterite content. Contrasting olivine nickel contents can constrain the environment of formation of olivine-rich rocks in the lower crust and mantle, the extent and nature of the processes by which they form, and the melt compositions involved in the reaction process. Comparison of olivine nickel contents in troctolite and gabbro occurrences in oceanic and ophiolite settings reveals a set of relationships consistent with this. Olivine gabbros from the 1508 m Hole 735B Atlantis Bank gabbro section have low nickel contents, whereas those from the 1400 m Hole U1309D Atlantis Massif gabbro section have high nickel. This is consistent with less-reacted infiltrating melt at the latter, and suggests that U1309D represents a deeper section of the lower crust near the crust^mantle transition, whereas the former has been shown to have crystallized near the dike^gabbro transition. Godzilla troctolites and gabbros bear clear similarities to East Pacific Rise (EPR) troctolites and gabbroic segregations drilled in dunites crosscutting residual mantle peridotite at Hess Deep Site 895.The latter represent multi-stage crystallization of stagnant melts in conduits beneath the EPR.Thus, it appears that the processes that formed the Godzilla troctolites occur beneath ocean ridges across the spreading rate spectrum.

Growth mechanisms of surface crystallized diopside

The two glasses A and B of similar composition are melted and annealed at 870 °C for up to 20 h to initiate the surface crystallization of diopside. Phase and orientation analyses are performed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Both glasses show two discernible layers of crystal growth into the bulk: while multiple phases occur in glass A only diopside is detected in the adapted glass B. The most part of crystal growth in layer 1 is subject to an orientation change of 90°. In the adapted glass B, the predominant c-axes orientations of layer 1 and 2 are orthogonal to each other. Sample deformation and specific crack patterns near the surface are described and explained by occurring tensions.

The thermal properties of cordierite/diopside composites fabricated by glass–ceramics process for LED packages

Abstract Cordierite/diopside composites were manufactured by the heat-treatment of green compacts composed of diopside (CaO–MgO–2SiO 2 ) and cordierite (2MgO–2Al 2 O 3 –5SiO 2 ) glass frits. The thermal properties were analyzed as a function of the type and intensity of the crystalline phases generated and the microstructure. The composites contained 0–30 wt% diopside glass frits had α-cordierite as the major phase and the μ-cordierite as the minor phase (designated as α-series). In the composites containing 40–80 wt% of diopside frit, the μ-cordierite and diopside crystals were generated as the major and minor phase, respectively (designated as μ-series). Adding diopside glass frit decreased the thermal conductivity of the α-series specimens but increased that of the μ-series specimens. The density of the composites showed a linearly proportional relationship with the thermal conductivity. At an equal density, the α-series specimens had higher thermal conductivity than the μ-series specimens. 30–50 nm crystals were sparsely observed in the microstructures of the μ-series specimens and 30–100 nm crystals were formed compactly in the α-series specimens. The cordierite/diopside composites manufactured in this research can be applied as LED packaging materials due to their adequate thermal conductivity of 1–3 W/mK and their diffusivity of 0.5–1.3 mm 2 /s.

Sintering behavior and mechanical properties of mica-diopside glass–ceramic composites reinforced by nano and micro-sized zirconia particles

Primary glass–ceramic containing phlogopite and diopside crystals were prepared through sintering of 70wt.% mica bearing and 30wt.% wollastonite bearing base glasses.Different amounts of microsized and nanosized partially stabilized zirconia particles were added to the aforementioned primary composition to improve mechanical properties.Glass–ceramics and the relevant composites were sintered in a temperature interval of 950–1020°C at the heating rate of 10°C/min and soaking time of 3 hat maximum temperature.According to the obtained results, phlogopite and diopside were formed as the main crystalline phases during sintering of zirconia free specimens. However, dissolution of zirconia in the glass matrix led to the formation of the zircon phase in zirconia containing specimens. Based on the SEM observations, residual nano-sized zirconia was detectable as the agglomerates in the microstructures. Micro-sized zirconia enhanced bending strength of the relevant composites. On the other hand, toughness was promoted in the presence of nano-sized zirconia particles.