مطالعه فنّی آرایه های گچی محوطه تاریخی شادیاخ نیشابور (ساختارشناسی سه قطعه آرایه گچی) (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
در میان آرایه های معماری خراسان، آنچه کمتر شناخته شده، آرایه های گچی یافت شده از شهر قدیم نیشابور است. این آرایه ها متعلق به سده های اولیه اسلام هستند و در ظرافت و تنوع نقش با آرایه های گچی ساسانیان و عباسیان در سامرا برابری می کنند. شادیاخ یکی از محوطه های شهر قدیم نیشابور است که آرایه های گچی بی نظیری از دوران سلجوقی را در خود جای داده است. مطالعات اندکی در رابطه با این محوطه و آرایه های گچی آن انجام شده است. هدف این پژوهش، شناخت فنّی و ساختاری ملاط سه قطعه از آرایه های گچی محوطه شادیاخ است که می تواند گام مهمی در راستای شناخت، معرفی و حفظ این آثار ارزشمند بوده و همچنین در بخش آرایه های معماری اطلس میراث فرهنگی ایران تأثیرگذار باشد. در این راستا از روش تصویربرداری با استفاده از میکروسکوپ پورتابل Dinolite، آنالیز XRD و همچنین SEM-EDS جهت انجام مطالعات فنّی استفاده شده است. نتیجه پژوهش نشان می دهد که فاز های اصلی نمونه ملاط های مورد مطالعه مربوط به ژیپس، کلسیت و کوارتز است. البته در یکی از نمونه ها، انیدریت هم به عنوان فاز اصلی شناخته شده است که این تبدیل فاز در شرایط آب وهوایی نیشابور دور از ذهن نیست. همچنین برای برش راحت تر نقوش آرایه گچی برجسته، هنرمند گچبر برای ساخت ملاط، ملاط کم مایه را انتخاب کرده و کمی بیشتر از حالت معمول، آن را ورز داده است (ملاط گچ نیم کشته). برای ماندگاری بیشتر آن، در زمان اجرای لایه بستر گچی، عملیات ماله کشی از حالت عادی بیشتر بوده و همچنین فشار ماله بر سطح بستر از حالت معمول بیشتر بوده است. درخصوص تغییرات و فرسایش ملاط، برخی از بلور های ژیپس به مرور زمان به انیدریت تبدیل شده و در برخی نمونه ها، ریزبلور ژیپس بر روی بلور های اصلی تشکیل شده است.An Investigation into the Characterization of Gypsum-Based Stucco Ornaments in Historical site of Shadiakh in Nishabur, Iran
Background and Objectives:
In order to complete and compile the cultural heritage atlas, one of the branches are architectural ornaments. Gypsum-based stucco ornaments are one of the important parts of Iran’s architectural ornaments. The gypsum-based stucco ornaments of Shadiakh of Nishapur area are among the ornaments belonging to the early centuries of Islam in Iran. In the present study, an attempt has been made to obtain information on the structural and technical aspects of the gypsum-based ornaments of Shadiakh Nishapur area.
In the following research, three fragments of mentioned ornaments of Shadiakh, which were found in the fourth season of excavations, were technically examined. Visual observations have also been made using a digital microscope. The structural analysis of these fragments has been done using X-ray diffraction (examination of the phases in gypsum samples) and scanning electron microscopy (observation of the crystal microstructure of the samples).
The archaeological site of Nishapur is located in the east of the current Nishapur, in the vicinity of the tombs of Attar and Khayyam (Haddon 2016). Shadiakh has been excavated during seven seasons (Labbaf khaniki, 2022). This area consists of various sections such as grape extraction workshop, blacksmith workshop, pottery and glass workshop, dungeon, stable, kitchen, warehouse, etc. According to the reports of the fourth season of the excavation (Labbaf Khaniki and Bakhtiari Shahri, 2003), one of the most important sections known as Bār-e ‘Ām Hall. This hall consists of four porches overlooking an octagonal space in the middle, which leads to the adjacent spaces through four corners and through four doors. The porches are built in different geographical directions. In the later periods, the northwest porch underwent changes with the use of a blade wall and the stucco ornaments. The northeast porch is the same as the northwest, with the difference in the floor height and in front of it, stucco ornaments and inscriptions are represented.
Methodes:
Imaging and observing the grain size of samples was done using a Dinolite portable microscope with a maximum magnification of 250 times. Images were taken at 60x magnification. For XRD analysis, the EXPLORER model device made by GNR, Italy, DECTRIS detector, with copper x-ray producing tube (Cu K alpha = 1.54 Å), maximum potential difference 40 Kv and current intensity 30 mA under 2θ angle and angle 60-60-degree radiation was used. The analysis was done qualitatively and the required analysis was done with Xpert software.
In order to image the crystalline microstructure of the samples, SEM device model LEO1450VP made by Zeiss, Germany with maximum voltage Kv 35 equipped with EDS analysis made by OXFORD England model 7353 and with resolution of 133eV was used. The samples were coated using SC 7620 gold-palladium coating machine for 180 seconds. Imaging was done in different magnifications and under 20 Kv voltage.
Findings:
XRD results: The samples have quartz, cristobalite, anhydrite, gypsum, calcite and goethite. The main phases identified in sample SH.1-U are: quartz, anhydrite and gypsum, and secondary phases include cristobalite and calcite. By examining the graphs of this sample and sample SH.2 the coexistence of anhydrite and gypsum is observed. Gypsum and anhydrite were identified as the main phase in sample SH.1-U, and gypsum as the main phase and anhydrite as secondary phase in sample SH.2. It seems that the placement conditions of these two samples after digging and exploration were not the same. In the third sample, only gypsum was detected. Quartz, which left a long peak in the sample SH.1-U and SH.2, is present as an impurity in gypsum compounds. In SH.3-U sample, quartz has been identified as a secondary phase. This impurity is mainly added to the gypsum mortar purposefully. Calcite is the other identified phase in all three fragments.
SEM results: It can be said that the accumulation of crystals in samples SH.1-U, SH.1-S, SH.2 is high and the crystals are densely placed next to each other. Samples SH.3-U and SH.3-S have less density and empty spaces like holes can be seen in it (compared to the previous two samples). Fewer gypsum crystals can be seen in SH.1-U and SH.1-S samples. In other samples, due to humidity and temperature fluctuations, gypsum microcrystals are formed on the main crystals. It seems that in SH.1-U and SH.1-S samples, some gypsum crystals have turned into anhydrite over time due to hot and dry environmental conditions. In the SH.1 and SH.2 samples, crystals have grown in the form of sheets (mostly in two directions) and some of them are placed on top of each other, which can be one of the reasons of slow pace of setting process.
Conclusion:
Regarding the constituent materials of the studied mortar samples, it can be said: their constituent compounds are not much different from each other. Part of the small difference in the elements and compositions can be related to the conditions of the exposure of the work in the long term and in the post-exploration period. Part of it is also related to the processing time of gypsum mortar. Part of the difference in the materials can be related to the impurity of the gypsum stone, which was baked in the same way and used after crushing and sieving. The main phases of the studied mortars are gypsum, calcite and quartz. Regarding the changes and erosion of the mortar, it seems that some gypsum crystals have turned into anhydrite over time, and in some samples, due to humidity and temperature fluctuations, part of the gypsum crystal has dissolved in water and then from the evaporation of water, gypsum microcrystals are formed on the main crystals.
Characterization,gypsum-based mortar,architectural Ornaments,Shadiakh,Nishabur,
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